GEOLOGY OF THE D CROSS MOUNTAINQUADRANGLE
SOCORRO AND CATRON COUNTIES,
NEW MEXICO
APPROVED:
D e a n o f G r a d u a t e School
GEOLOGY OF THE D CROSSMOUNTAINQUADRANGLE,
SOCORROANDCATRONCOUNTIESr
NEW MEXICO
BOB RUSSELLROBINSON
B a c h e l o r of Science: Master of Science
DISSERTATION
Presented t o t h e F a c u l t y o f t h e G r a d u a t e School of
The U n i v e r s i t y o f W x a s a t E l Paso
in Partial Fulfillment
for t h e Degree of
DOCTOR OF G E O L O G I C A LS C I E N C E S
I N GEOLOGY
T H EU N I V E R S I T YO FT E X A SA TE LP A S 0
May, 1 9 8 1
ACKNOWLEDGEMENTS
I thank Dr. DavidIeMone,
h i s help i n allphases
h i sd e s i r e
my committeechairman,
of thisundertaking,especiallyfor
and demand t h a tt h ej o bb ec o m p l e t e d .
members o f my c o m m i t t e ew e r ea l w a y sa v a i l a b l e
t i v e i n s o l v i n ga n yp r o b l e m st h a t
S t u a r t was e s p e c i a l l y h e l p f u l
Dr. C.
pretations.
for
The o t h e r
and coopera-
I encountered.
Dr. C.
w i t h s e d i m e n t o l o g i c a li n t e r -
Chapin, Dr. S. Hook, D.
Tabet
and
F.
Campbell of t h e N e w Mexico Bureau o f Mines andMineral
R e s o u r c e sp r o v i d e db o t hn e e d e dc r i t i c i s m
me t o b e t t e r u n d e r s t a n d
t h a te n a b l e d
F i n a l l yt o
R.
I g i v e my s i n c e r e s t
was p r o v i d e df o rt h i ss t u d yb yt h e
Mexico B u r e a u o f Minesand
number 816-246
and e n j o y my work.
Mills and a c a s t o f t h o u s a n d s t h a t i n s i s t e d
that this dissertation be completed,
kudos.Funding
and encouragement
New
Mineral Resources a s p r o j e c t
NW.
ii
ABSTRACT
Approximately 5 0 0 0 f t ( 1 5 2 5 m ) o f s t r a t a c r o p o u t i n
t h e D C r o s sM o u n t a i nq u a d r a n g l ei nw e s t - c e n t r a l
The o l d e s t s t r a t a a r e r e d s h a l e s
New Mexico.
andsandstonesof
the
C h i n l eF o r m a t i o n( L a t eT r i a s s i c )t h a ta c c u m u l a t e do na n
a meandering stream
e x t e n s i v e ,l o w - l y i n g ,c o a s t a lp l a i ni n
c o m p l e x .J u r a s s i ca g es t r a t a ,i fd e p o s i t e d
were s u b s e q u e n t l ye r o d e d
i n the area,
d u e t o u p l i f t o f t h e Mogollon
Highlands and n o r t h - n o r t h w e s tt i l t i n go f
t h e a r e ad u r i n gt h e
Jurassic.
The basalDakotaSandstone
planing
i n gt h e
, meandering
was d e p o s i t e d b y l a t e r a l l y
streams b e f o r e r e g i o n a l s u b s i d e n c e d u r -
Cenomanian r e s u l t e d i n t h ei n i t i a le n c r o a c h m e n t
t h em i d - c o n t i n e n tC r e t a c e o u ss e a w a yi n t ot h e
Acoma embayment.
!the area o s c i l l a t e d b e t w e e n p a r a l i c
m a r i n ee n v i r o n m e n t sf o r
Period.
of
and c o a s t a l non-
t h e remainderof
t h e Cretaceous
As a r e s u l t , a c o m p l e xs e q u e n c eo fd a r k ,o f f s h o r e
m a r i n e muds of t h e Mancos S h a l e i n t e r f i n g e r t o t h e
c o a s t a lm a r i n e
and f l u v i a l s a n d s t o n e s
west w i t h
and s h a l e s o f t h e
Dakota, Tres Hermanos, Gallup,andCrevasse
Canyon Formations.
N o r t h e a s t - d i r e c t e dc o m p r e s s i o n a lf o r c e sa s s o c i a t e d
t h eL a r a m i d eo r o g e n yd e f o r m e dt h es t r a t ai n t o
b r o a do p e nf o l d s
a t t h e c l o s eo fC r e t a c e o u s
c o n g l o m e r a t e sa n da r k o s i cs a n d s t o n e so ft h e
with
a series of
time.
Pebble
Baca Formation
(Eocene) were eroded from t h e Z u n iM o u n t a i n s ,t r a n s p o r t e dt o
iii
t h es o u t h e a s ti n
a f l u v i a lc h a n n e l - f l o o d p l a i nc o m p l e x ,
and
a c c u m u l a t e di na ne a s t - t r e n d i n g ,e l o n g a t e ,s t r u c t u r a ll o w .
A t h i c kc o v e ro fv o l c a n i c
spreadover
t h e a r e ad u r i n gt h eO l i g o c e n e .L i t h i c - c r y s t a l
and c r y s t a l - l i t h i c
t u f f s and d e b r i s f l o w so f
Formationwerederived
s o u t ho f
and v o l c a n i c l a s t i c r o c k s
th e Spears
from a m a j o r v o l c a n i c c e n t e r l o c a t e d
t h e D CrossMountainquadrangle.
After c e s s a t i o no fv o l c a n i s m ,s e d i m e n t sw e r es t r i p p e d
from t h i s v o l c a n i ch i g h l a n d
e x t e n d i n ga l l u v i a lf a n
e r a t eo f
RockTank
and accumulatedin
complex.
a northward
The Miocene ( ? ) conglom-
Canyon is a f a n g l o m e r a t et h a t
was d e r i v e d
p r i n c i p a l l y from e r o s i o n of Spears t u f f s .
t h e a r e a i s a south-dipping
The d o m i n a n ts t r u c t u r eo f
homoclineformed
Plateau.
as t h e r e s u l t o f u p l i f t o f t h e C o l o r a d o
The c o n t i n u i t yo f
t h e homocline i s , however,
broken b y a s e r i e s of Neogene normal f a u l t s t h a t formed i n
r e s p o n s et o
t h e opening of t h e RioGrande
necks and p l u g sc r o p p i n go u t
Mesa were e m p l a c e dd u r i n gt h e
r i f t .V o l c a n i c
on D CrossMountain
and B l u e
Late T e r t i a r y andappearto
p o s t - d a t eu p l i f to ft h eP l a t e a u .
iv
CONTENTS
Pag e
..................
Abstract . . . . . . . . . . . . . . . . . . . . . . .
Table of C o n t e n t s . . . . . . . . . . . . . . . . .
L i s t of Figures . . . . . . . . . . . . . . . . . .
L i s t of Tables . . . . . . . . . . . . . . . . . . .
L i s t of Plates . . . . . . . . . . . . . . . . . . .
Introduction . . . . . . . . . . . . . . . . . . . .
L o c a t i o n and Access . . . . . . . . . . . . . .
Climate a n dV e g e t a t i o n
............
Physiography . . . . . . . . . . . . . . . . .
Purpose and Scope
...............
P r e v i o u s Work . . . . . . . . . . . . . . . . .
R e g i o n aS
l etting
...............
S t r a t i g r a p h y. . . . . . . . . . . . . . . . . . . . .
T r i a s s i c System . . . . . . . . . . . . . . . .
Chinle Formation . . . . . . . . . . . . .
Cretaceous System . . . . . . . . . . . . . . .
Dakota Sandstone . . . . . . . . . . . . .
DakotaSandstone
- Main Body . . . .
P a g u a t e Tongue . . . . . . . . . . . .
Twowells Tongue . . . . . . . . . . .
Mancos S h a l e . . . . . . . . . . . . . . .
N
IM S p r i n g s Tongue . . . . . . . . . .
WhitewaterArroyo
Tongue . . . . . . .
Acknowledgements
V
ii
iii
V
viii
ix
X
1
1
1
3
5
6
7
10
10
10
16
18
18
27
33
39
39
43
Page
..........
Tongue . . . . . . . . . . . .
Rio Salado Tongue
45
D Cross
50
..........
Atarque Member . . . . . . . . . . . .
Carthage Member . . . . . . . . . . .
F i t e Ranch Member . . . . . . . . . .
Mesaverde Group . . . . . . . . . . . . . .
Gallup
Sandstone
............
Crevasse Canyon Formation . . . . . .
T e r t i a r y System . . . . . . . . . . . . . . . .
Baca Formation . . . . . . . . . . . . . .
S p eFaorrsm a t i o n
..............
Tres Hermanos Sandstone
.....
B l u e Mesa B a s a l t . . . . . . . . . . . . .
Q u a t e r n aSryys t e m
...............
Pediment
Gravels
.............
Alluvium.Colluvium.Landside.and
E o l i aDne p o s i t s
..............
I n t r u s i v e Rocks . . . . . . . . . . . . . . . .
S t r u c t u r a l Geology . . . . . . . . . . . . . . . . .
Geomorphology . . . . . . . . . . . . . . . . . . . . .
Economic Geology . . . . . . . . . . . . . . . . . .
Coal . . . . . . . . . . . . . . . . . . . . . .
Uranium . . . . . . . . . . . . . . . . . . . . .
O i l and Gas . . . . . . . . . . . . . . . . . .
Summary o f G e o l o g i H
c istory . . . . . . . . . . . . .
Conglomerate of Rock
Tank
vi
Canyon
52
56
59
60
64
64
73
82
83
92
98
102
106
106
108
109
115
121
122
122
130
130
132
Page
..................
Appendix A: P o i n t CountMineralogy
of S e l e c t e d
Thin-sections . . . . . . . . . . . . .
Appendix B:
P a l e o c u r r eD
n ta t a
...........
Appendix C : Measured S e c t i o n . . . . . . . . . . . .
Vita . . . . . . . . . . . . . . . . . . . . . . . .
R e f e r e n c e sC i t e d
vii
135
149
154
157
213
LIST OF FIGURES
Page
Figure 1
Index map s h o w i n gl o c a t i o n
D CrossMountainquadrangle
Figure 2
New Mexico.
i n northwestern
...............
...............
D i a g r a m a t i cs e c t i o n
New Mexico
S t r a t i g r a p h i cs e c t i o n
.........
S t r a t i g r a p h i cs e c t i o n
Figure 9
S t r a t i g r a p h i cs e c t i o n
Figure 1 0
.....
...........
54
67
o f t h eC r e v a s s e
S t r a t i g r a p h i cs e c t i o n
............
F i g u r e 11 Map showing t h e l o c a t i o n
MountainCoalField
36
of t h eG a l l u p
..............*.
Canyon Formation.
29
of t h e Tres
s t r a t i g r a p h i cs e c t i o n
Sandstone
.....
o f t h e Twowells
tongue of t h e DakotaSandstone.
Hermanos Sandstone.
20
of t h eP a g u a t e
tongue of t h e DakotaSandstone.
Figure 8
19
D i a g r a m a t i cc r o s s - s e c t i o na c r o s s
west-central
Figure 7
11
out in the D
. . . . . . . . .. .
CrossMountainarea
Figure 6
8
of the Cretaceous
m a r i n es t r a t ac r o p p i n g
Figure 5
2
S t r a t i g r a p h y i n t h e D CrossMountain
quadrangle.
Figure 4
.......
Map showing t h e l o c a t i o n o f t h e major
s t r u c t u r a ld i v i s i o n s
Figure 3
of t h e
of t h eD a t i l
...........
viii
75
123
L I S T OF TABLES
Pag e
Table 1
X-ray F l u o r e s c e n caen a l y s e s
volcanicrocksfromthe
Mountain
area
Table 2
Chemical
analyses
from t h D
e atil
of
D Cross
..............
96
of c o asla m p l e s
Mountain
Coal
ix
Field.
..
.
128
L I S T OF PLATES
Page
Plate 1
Geologic Map o f t h e
D CrossMountain
.........
..........
q u a d r a n g l e , New Mexico.
Plate 2
D Cross
Mountain
Area
Plate 3
C h a n n e ls a n d s t o n ei nt h eC h i n l e
................
Formation
Plate 4
C r e t a c e o u ss t r a t ae x p o s e d
s l o poef
Plate 5
Plate 6
4
14
on t h e e a s t
........
D Cross
Mountain
B a s a lc h e r tp e b b l ec o n g l o m e r a t ei n
main
body
in
pocket
of the
Dakota
Sandstone
17
the
....
23
.
30
ContactbetweenthePaguatetongueof
t h e DakotaSandstoneandunderlying
N
IM S p r i n gt so n g u e
Plate 7
o f t h e Mancos S h a l e .
C l i f f - f o r m i n go u t c r o po fm o w e l l s
sandstone
................
Mammites d e p r e s s u s . . . . . .
Plate 8
Specimen
of
Plate 9
C l i f f - f o r m i n go u t c r o po f
35
41
t h e Atarque
..
...........
Member of t h e T r e s Hermanos Sandstone
51
Plate 1 0
Ophiomorpha
burrows
58
P l a t e 11
C l i f f - f o r m i n go u t c r o po ft h e
Sandstone
Plate 1 2
................
66
C r o s s - s t r a t i f i e du p p e rs h o r e f a c ed e p o s i t s
i n tG
h ea l l uSpa n d s t o n e
Plate 13
Gallup
Oyster
bioherm
in
.........
69
.
70
t h e Gallup
Sandstone.
X
Pag e
P l a t e 14
Plate 15
Channelsandstone
i n theCrevasse
Canyon Formation.
............
Coal seam i n t h e Crevasse Canyon
Formation
................
Baca Formation. . . . . . . .
P l a t e 16
Exposureof
Plate 17
S h a l es t r a t a
Formation
80
84
i n t h e base of t h e Baca
................
C r y s t a l - l i t h i ct u f f s
P l a t e 19
................
Conglomerate o f Rock Tank Canyon. . . . .
P l a t e 20
P h o t a n i c r o g r a p ho ft h i n - s e c t i o no f
Formation
B l u e Mesa b a s a l t .
a7
i n t h eS p e a r s
Plate 18
Plate 2 1
71
............
94
100
104
Flows of Blue Mesa b a s a l t c a p p i n g
D Cross
Mountain
..........
............
Mesa
P l a t e 22
D Cross
Mountain.
P l a t e 23
Coal seam a tt h eb a s eo ft h eC r e v a s s e
Plate 24
............
P h o t o m i c r o g r a p ho fc o a lt h i n - s e c t i o n .
..
Canyon Formation.
xi
105
110
124
127
INTRODUCTION
Location and Access
i s l o c a t e da p p r o x i m a t e l y
The s t u d y a r e a
New Mexico, i n t h e n o r t h e a s t e r n p a r t
northwestofMagdalena,
of CatronCountyandthenorthwesternpart
( F i g u r e 1 ) . This 64 m i
CrossMountain
4 0 m i ( 6 4 km)
2
o f SocorroCounty
a r e a i s i n c l u d e de n t i r e l y
on t h e D
7 1/2' t o p o g r a p h i cs h e e tp u b l i s h e db yt h e
Access t o t h e D Cross
UnitedStatesGeologicalSurvey.
i s m o s te a s i l yo b t a i n e db y
Mountainarea
theMartinRanch,
a gradedroadto
which i n t e r s e c t sS t a t e
Highway 5 2 ,
a p p r o x i m a t e l y 2 5 m i ( 6 5 km) n o r t h o f Magdalena.
Climate andVegetation
i s approximately 1 2 i n .
P r e c i p i t a t i o ni nt h es t u d ya r e a
( 3 0 cm) a n n u a l l y and o c c u r s m o s t f r e q u e n t l y a s d o w n p o u r s
d u r i n g t h e summer and e a r l yf a l l .T e m p e r a t u r e sr a n g e
0
s l i g h t l yo v e r
0
1 0 0 F ( 3 8 C ) on summer d a y st o
from
well below
The a r e a i s c l a s s i f e da s
f r e e z i n gd u r i n gw i n t e rn i g h t s .
a
semiarid desert.
V e g e t a t i o n i s t y p i c a lo fh i g he l e v a t i o n ,s e m i a r i d
r e g i o n so ft h es o u t h w e s t .T r e e s
PinyonPine,
common t o t h e a r e ai n c l u d e :
Rocky MountainJuniper,andStaghornCholla.
RioGrandeCottonwoodandBonpolandWillows
along the c o u r s e so fl a r g e r ,s a n d y
a r ea b u n d a n t
creeks and a t h i g h e r
e l e v a t i o n ss t a n d so fP o n d e r o s aP i n eo c c u r
s l o p e s .v a r i o u s
s h r u b s , g r a s s e s ,c a c t i ,
1
on s a n d s t o n e d i p
a n ds m a l lo a kt r e e s
2
"
"
...
Socorro Co.
N
,''.
Bear M t s .
S.H. 60
.
0
5 mi
Figure 1. M a p showing t h e location of the study area.
3
a l s of l o u r i s hw i t h i n
The v e g e t a t i o n i s o ft h e
the area.
Upper Sonoran t oT r a n s i t i o nL i f eZ o n e s .
Largerformsof
w i l d l i f e a r en o ta b u n d a n ti nt h ea r e a .
and b i r d s are most common.
R a b b i t ,d e e r ,s n a k e s ,r o d e n t s ,
F o x ,c o y o t e ,m o u n t a i nl i o n ,b o b c a t ,a n db l a c kb e a ra r er a r e .
The a r e a i s u s e de x c l u s i v e l yf o rd o m e s t i cl i v e s t o c k
grazingP
. l e n t i f u lw e l l - w a t e r
and a p p a r e n t l ya d e q u a t e
foliagesupportmoderate-sizeherdsofcattle.
Physiography
is w i t h i n t h e Datil
The D CrossMountainquadrangle
s u b d i v i s i o no ft h eB a s i n
(Hawleyand
andRange
others, 1976).
p h y s i o g r a p h i cp r o v i n c e
t h e GallinasMountains,DatilMountains
Cross Mountain,extendinto
( B l u e Mesa),and
t h e a r e a( P l a t e
n a s Range i s composed ofrounded
o ft h et h r e er a n g e s
D
The G a l l i -
2).
h i l l s o fd e e p l yi n c i s e d
q u a r t zl a t i t et u f f so ft h eS p e a r sF o r m a t i o n .
w i t h a maximum e l e v a t i o n . o f
,
Threeprominentmountainranges
Blue Mesa,
8541 f t ( 2 6 0 4 m)
and i s cappedby
, is
thehighest
a seriesofflat-lying
b a s a l tf l o w sw h i c hh a v ep r e v e n t e dd e v e l o p m e n to f ,a n ds u b s e -
As a r e s u l t ,
quentdowncuttingbyanymajorstreamsystem.
t h e northernendofBlue
mass.
Mesa i s a l a r g e m o n o l i t h i c r o c k
D Cross Mountain i s a v o l c a n i cn e c kw h i c hh a si n -
t r u d e di n t og e n t l yd i p p i n gC r e t a c e o u sa g es a n d s t o n e sa n d
shales.
D i f f e r e n t i a le r o s i o no ft h es h a l e s
hasproduced
the mountain.
a s e r i e s o f benchesand
andsandstones
c l i f f s o nt h es l o p e so f
4
Plate 2 .
D Cross MountainArea--view
i s to t h en o r t h w e s t .
The l i g h t c o l o r e d h i l l s i n t h e
l e f t foregroundare
theGallinasMountains;darkermountain
in left
background i s Blue Mesa; D Cross Mountain i n r i g h t
background
.
5
EasilyerodedChinleandCrevasse
Canyon s t r a t a form a
r o l l i n g h i l l t o p o g r a p h yi nt h en o r t h e a s t e r np o r t i o no f
mapped a r e a .
On t h e e a s t s i d e ofBlue
the
Mesa and t h e n o r t h
f a c eo ft h eG a l l i n a sM o u n t a i n s ,p e d i m e n ts u r f a c e st h a td i p
awayfrom
t h em o u n t a i nf r o n t s
AlamocitaCreek,
are thedominantlandforms.
a l a r g es a n d ye p h e m e r a l
e a s t and c u t s o b l i q u e l y a c r o s s
area.
the structuralgrainof
the
t h e m a s t e r stream a r ed o m i n a n t l y
T r i b u t a r i e so f
north-trending
stream, flows
.
Local r e l i e f i s a p p r o x i m a t e l y 2200 f t ( 6 7 0 m ) , r a n g i n g
from 6380 f t (1945 m ) i n t h e
8541 f t (2603 m ) on Blue Mesa.
e x i t s t h e s t u d ya r e a ,t o
CrossMountain
bed ofAlamocitaCreekwhere
it
D
r i s e s 8495 f t (2589 m ) a b o v es e al e v e l .
PurposeandScope
The p u r p o s eo f
g e o l o g yo f
t h i s s t u d y was t o map and describe t h e
t h e D CrossMountainquadrangle.
mapped d u r i n g 1978-80 a t a s c a l e o f
S t a t e sG e o l o g i c a lS u r v e y
lhe a r e a was
1:24,000 usingUnited
(USGS) t o p o g r a p h i c sheets and
United States F o r e s tS e r v i c ec o l o ra e r i a lp h o t o g r a p h s .
Measured s e c t i o n s wereused
t h er e g i o n a lg e o l o g i cs e t t i n g
e x t e n t ,g e o m e t r y ,
and t o d e t e r m i n e t h e l a t e r a l
and r e l a t i o n so ft h e
r o n m e n t a li n t e r p r e t a t i o n s
c o n t e n t ,t h e
t oi n t e g r a t et h ea r e ai n t o
mapped u n i t s . h v i -
are based on u n i t g e o m e t r y , f o s s i l
type o f u n i t c o n t a c t s ,
and v e r t i c a l and l a t e r a l
s e q u e n c e so fs e d i m e n t a r ys t r u c t u r e s .S i x t yf i v et h i n s e c t i o n s were e x a m i n e d p e t r o g r a p h i c a l l y f o r g r a i n s i z e ,
6
s o r t i n g , grain morphology, mineralogy, and diagenetic
c h a n g e st oa u g m e n th a n d - s p e c i m e nd e s c r i p t i o n s
of t h e rock
18 u l t r a - t h i nc o a ls e c t i o n s
u n i t s .A d d i t i o n a l l y ,
were
Four c o a l samples were
examined f o r maceralcomponents.
a n a l y z e df o r
B.T.U.
v a l u e , andwhole-rockanalysesofthe
majoroxides
were o b t a i n e d fromtwo
Rock c o l o r s weredeterminedin
units.
igneousrock
t h e f i e l du s i n g
the
of A m e r i c ar o c kc o l o rc h a r t .
G e o l o g i c a lS o c i e t y
P r e v i o u s Work
Herrick (1900) was t h e f i r s t g e o l o g i s t t o r e p o r t
t h e s t r a t ac r o p p i n go u ti nt h e
on
D CrossMountainarea.
He
produced a r e c o n n a i s s a n c e s t r i p map along t h e c o u r s e o f
Alamocita C r e e k and b r o a d l y d i f f e r e n t i a t e d
Triassic,
C r e t a c e o u s ,a n dv o l c a n i cr o c ku n i t s .
Winchester ( 1 9 2 0 ) s t u d i e d the C r e t a c e o u ss t r a t aa s
p a r to f
upper Rio Salado
a c o a le v a l u a t i o np r o g r a mo ft h e
d r a i n a g eb a s i n .
Basedon
a
s t r a t i g r a p h i cs e c t i o n sm e a s u r e di n
t h e s t u d y area, W i n c h e s t e ri n t r o d u c e ds e v e r a l
new forma-
t i o n a l names i n t o t h e l i t e r a t u r e .
The o i l and g a s p o s s i b i l i t i e s o f t h e a r e a
onby
Wells ( 1 9 1 9 ) .I n
thestratigraphy
were r e p o r t e d
t h i s r e p o r t Wells b r i e f l y d e s c r i b e d
and s t r u c t u r e o f a p o r t i o n o f t h e
D Cross
Mountainquadrangle.
The a r e a was mapped a t a scale of a p p r o x i m a t e l y
1:126,000byGivens(1957)
quadrangle.
a s a p a r to ft h e
His map i s , however
, of
Dog S p r i n g s
a g e n e r a ln a t u r e .
7
Many g e o l o g i s t s ( P i k e , 1 9 4 7 ; L a n d i s , Dane andCobban,
1973; and M o l e n a a r ,1 9 7 3 )h a v em e a s u r e dp a r t i a ls e c t i o n s
of
in t h e a r e a i n a n a t t e m p t
t h eC r e t a c e o u ss t r a t ac r o p p i n go u t
t oc o n s t r u c tr e g i o n a ls t r a t i g r a p h i cc r o s s - s e c t i o n s .
The
Cretaceouspaleontologyhasbeenextensivelydiscussedby
197713) ,
Landis, Dane and Cobban ( 1 9 7 3 ) , Cobban (1977aand
Cobban and Hook ( 1 9 7 9 ) , Hook and Cobban (1977,1979,1980a,
and1980b),
and Hook, Cobban and Landis(1980).Other
reportsthathavebrieflynoted
t h e g e o l o g yo f
the areaare
text.
r e f e r e n c e dw i t h i nt h e
R e g i o n a lS e t t i n g
The D CrossMountainquadrangle
i s l o c a t e db e t w e e nt h e
Acoma embayment and t h e Mogollon s l o p e( F i g u r e
Acoma embayment, a r e g i o n a l s y n c l i n a l s t r u c t u r e
f a u l t e d and f o l d e dM e s o z o i cs t r a t a
southwest , g r a d e sn o r t h w a r di n t o
dippingTertiaryvolcanics
composed o f
that d i p gentlytothe
The
t h e San JuanBasin.
Mogollon s l o p e i s t h es o u t h e r nb o u n d a r y
Plateau(Fitzsimmons,1959)
The
2).
o f theColorado
and is formedbysouthward
and a s s o c i a t e d s e d i m e n t a r y r o c k s .
The Zuni Mountains are a northwest-trending,assym-
The u p l i f t e db l o c k
m e t r i c a l ,d o u b l yp l u n g i n ga n t i c l i n e .
50 m i ( 8 0 km) longand
20 m i ( 3 2 km) wideandhasbeen
s t r u c t u r a l l ye l e v a t e da p p r o x i m a t e l y
5000 f t ( 1 5 2 5 m) ( K e l l e y ,
1955).Precambriangranitesandmetamorphicrocks
exposed i nt h ec o r e
and c l a s t i c r o c k s d i p
is
are
of t h es t r u c t u r e .P a l e o z o i cc a r b o n a t e
awayfrom
t h e crest of t h e a n t i c l i n e .
8
SAN JUANBASIN
ZUNI UPLIFT
ACOMA BASIN
MOGOLLON
SLOPE
SAN AGUSTINE~IAINS
Figure 2. M a p showing the location of the major
structural elements in northwestern New Mexico.
9
The Lucero u p l i f t and P u e r c of a u l t
k m ) wide,
The Lucero u p l i f t i s a 1 0 m i ( 1 6
west.
s t u d ya r e at ot h e
zoneborderthe
40 m i ( 6 4 km) l o n g ,a s y m m e t r i c a l ,u p l i f t e db l o c k
t h a tt r e n d s
N 10'
S t r a t ai n v o l v e di nt h eu p l i f th a v e
E.
undergonebroadarching
and o v e r t h r u s t i n ga s s o c i a t e d
theLaramideorogeny(Kelley
with
and Wood, 1946)andthe
Southern Rocky M o u n t a i nd e f o r m a t i o nb e l t( K e l l e y ,1 9 5 7 ) .
i s a s e r i e so fn o r t h - n o r t h e a s t -
The P u e r c of a u l tz o n e
The f a u l t zone is
t r e n d i n g down-to-the-westnormalfaults.
7-22 m i ( 10-34 km) wideand
w i t h i nt h e
30 m i ( 4 8 km) l o n g .S t r a t a
The m a j o rf a u l t s
zone d i p g e n t l y t o t h e e a s t .
a r e of b a s i n a n dr a n g eo r i g i n( K e l l e y ,1 9 5 7 ) ,a l t h o u g hb a s i n
f o r m a t i o nw i t h i nt h e
Rio Grande r i f t h a s a f f e c t e d t h e a r e a .
S o u t h e a s to ft h es t u d ya r e a ,o p e n i n go ft h e
r i f th a sp r o d u c e ds e v e r a lg r a b e ns t r u c t u r e s .
Gulchgrabenforms
g r a b e ns t r u c t u r eb e g a nt o
C h a p i n ,o r a l
The Mulligan
a north-trendingtopographiclowbetween
t h e Bear-MagdalenaandGallinas-San
(C.
RioGrande
commun.
Mateo Mountains.
form approximately 26 m.y.
, 1979).
This
B.P.
The SanAugustinePlains,
a f l a t , e x t e n s i v es u r f a c el o c a t e ds o u t ho f
Mountains, i s a l s o a g r a v e l - f i l l e d b a s i n t h a t
t h e Gallinas
is p a r t o f t h e
s o u t h w e s t - t r e n d i n gg r a b e nc o m p l e xt h a tf o r m e di nr e s p o n s et o
openingofthe
RioGrande
r i f t (Chapin and o t h e r ,1 9 7 5 ) .
10
STRATIGRAPHY
Approximately 5 0 0 0 f t (1525 m ) o fT r i a s s i ct h r o u g h
Q u a t e r n a r ya g es t r a t ac r o po u ti nt h e
q u a d r a n g l e( F i g u r e
D CrossMountain
the evolving cli-
d e p o s i t i o n a le n v i r o n m e n t st h a tr e f l e c t
matic , tectonic
a plethora of
These r o c k sr e p r e s e n t
3).
, volcanic
and s e d i m e n t a l o g i c a l c o n d i t i o n s
p r e v a l e n t i n t h e area d u r i n g t h e p a s t
200 m i l l i o n y e a r s .
T r i a s s i cS y s t e m
The Triassic System is r e p r e s e n t e db yt h eC h i n l e
a t i o n i n t h e D CrossMountainarea.Only
Form-
a p a r t i a ls e c t i o n
o f t h e f o r m a t i o n is e x p o s e di nt h es t u d ya r e a .
Younger
T r i a s s i c or J u r a s s i c s t r a t a , i f d e p o s i t e d ,
were s u b s e q u e n t l y
erodedfromthearea.
C h i n l e Formation
The term "Chinle" was o r i g i n a l l ya p p l i e db yG r e g o r y
( 1 9 1 6 ) t o" h i g h l yc o l o r e d
. .. s h a l e s a n ds a n d s t o n e "t h a t
exposedinChinleValley,Arizona.
A t t h er e f e r e n c e
are
sec-
t i o n ,G r e g o r yd i v i d e dt h ef o r m a t i o ni n t of o u ri n f o r m a l
u n i t s .C o r r e l a t i v e s
of t h e s e are n o tr e c o g n i z e d
i n the
Acoma b a s i n .
Tonking(1957)
was t h e f i r s t p e r s o n t o
t e r m i n o l o g yf o rs t r a t ac r o p p i n go u ti nt h e
use t h eC h i n l e
Acoma b a s i n .I n
t h e P u e r t e c i t o area, h ed i v i d e dt h ef o r m a t i o ni n t of o u r
i n f o r m aul n i t sL
. a t e rG
, i v e n s( 1 9 5 7 a) p p l i e dt h e
name
11
STRATIGRAPHIC UNIT
AGE
-
unconsolidated qravels
Solo
leis.
"
"
Blue Mesa Basalts
'lio.
dio.
conglomerate of Rock Tank Canyon
ligo
Spears Formation
Baca Formation
l
W
ma a
CrevasseCanyon Formation
x@
Gallup Sandstone
m h 3
$e
D Cross tongue
m
0 a,
Gc:
Fite Ranch Member
6
Carthage
Member
m o
2z 7m
mw
v,
Atarque Member
Rio Salado tongue
a,
3
Twowells tongue
m
0
0
e
m
m
Paguate tongue
ul
INM Springs
tongue
m
Dakota Sandstone-main body
Triassic
Chinle Formation
Figure 3 . Stratigraphic column for the D Cross
Mountain area, New Mexico.
m
12
C h i n l eF o r m a t i o nt o
a s e r i e s o f “red shales andmudstones’’
west o ft h e
t h a tc r o po u t
D Cross
(1920) had e a r l i e r used
Mountainquadrangle.Winchester
these same s t r a t a .F o l l o w i n g
o n l y “Red Beds’’ t od e s i g n a t e
the usageofGivens
i n the
Red L a k e f a u l t
(1957), two i n f o r m a l d i v i s i o n s o f t h e
Chinle are r e c o g n i z e di nt h e
map area:
and a l a w e rs a n d s t o n eu n i t .
Basedoncomparisonsofthe
C h i n l ei n
t h e s t u d ya r e a
a nu p p e rs h a l eu n i t
w i t h T o n k i n g ’ sd e s c r i p t i o n s ,t h e
s a n d s t o n ea n ds h a l eu n i t so f
D CrossMountainprobably
c o r r e l a t e w i t h T o n k i n g ‘ su n i t st h r e e
and f o u r ,r e s p e c t i v e l y .
R e g i o n a l l y , t h e Chinle i s d i s c o r d a n t l y o v e r l a i n b y t h e
CretaceousDakotaSandstone.
twoformations
t h eC h i n l e
The unconformitybetween
i s n o to b v i o u sl o c a l l y .
i s n o te x p o s e di nt h e
the
of
The b a s a lc o n t a c t
D CrossMountainquadrangle
and a c o m p l e t es t r a t i g r a p h i cs e c t i o nc o u l dn o tb em e a s u r e d .
From well l o g d a t a ,F o s t e r
m ) o fC h i n l es t r a t aa r e
v i c i n i t yo f
(1964) inferred t h a t 1475 f t (450
present i n t h e subsurface i n t h e
D CrossMountain.
The C h i n l ea p p e a r st o
m a i n t a i n a u n i f o r mt h i c k n e s sf r o mn o r t h - c e n t r a l
N e w Mexico
s o u t h w a r du n t i lr e a c h i n gt h ez e r oi s o p a c hl i n ef o r
r o c k si nV a l e n c i aC o u n t y ,
Jurassic
New Mexico ( F o s t e r , 1964).
ofthisline,theChinlethinsrapidly
a n dp i n c h e so u ta l o n g
a w e s t - n o r t h w e s t - t r e n d i n gl i n ep a s s i n gt h r o u g hR e s e r v e ,
Mexico ( F o s t e r , 1964).
South
New
The s o u t h w e s t h i n n i n go ft h eC h i n l e
is largely the resultofpost-Triassicerosionalthough
d e p o s i t i o n a lt h i n n i n gc a n n o tb e
ruled o u t .
some
13
No d i a g n o s t i c f o s s i l s
werecollectedfromtheChinle
s t r a t a ,a l t h o u g hs i l i c i f i e d
o t h e ra r e a s ,v e r t e b r a t ef o s s i l s ," f o s s i lf o r e s t " ,
and f r e s h
These
w a t e rb i v a l v e sh a v eb e e nr e p o r t e d( D a u g h e r t y 1, 9 4 1 ) .
f o s s i l si n d i c a t e
In
wood f r a g m e n t sa r ep r e s e n t .
a Late T r i a s s i ca g ef o r
t h e Chinle (McKee,
1951).
u n i t o f t h e ChinleFormation
The lowersandstone
c o n s i s t s o f approximately 5 0 f t ( 1 5 m) o f t h i n - t o
thick-bedded
, w h i t e ,r e d
s i l t s t o n e s( P l a t e
3).
andlavendersandstonesand
The s a n d s t o n e s are m o d e r a t e l y
indurated, very calcareous,
f i n e - to very fine-grained
, submature
moderatelytowell-sorted
,
l i t h i c arkoses.
S u b a n g u l a rt os u b r o u n d e dg r a i n so fq u a r t za r et h em o s t
common frameworkconstituentandcomprise
6 5 7 0 % o ft h e
r o c k .V a c u o l i z e dp l a g i o c l a s e ,o r t h o c l a s e ,m u s c o v i t e ,o p a q u e
m i n e r a l s , c h e r t , subhedralzircon,andbadlyweatheredvol-
canic ( ? ) rockfragmentsoccurinvaryingamounts(Appendix
A)
*
The rock i s c e m e n t e db yl a r g e ,
diameter,equant
texture.
0.2 i n . ( 5 1
mm)-
c a l c i t e c r y s t a l s and h a s a p o i k i l i t i c
P a r t i a lr e p l a c e m e n to ft h ef r a m e w o r kg r a i n sb y
c a l c i t e cement is common.
Fine- t oc o a r s e - t e x t u r e dc h e r t
and k a o l i n i t e a r e l o c a l l y p r o m i n e n t
The s a n d s t o n e u n i t
the
cements.
is composed o f a s e r i e s o f l a r g e
S c a l ec u t - a n d - f i l ld e p o s i t s .
Each c u t - a n d - f i l lf e a t u r e
is
boundedbyanupperandlowercurvedtruncationsurface.
Each s e d i m e n t a t i o n u n i t e x h i b i t s
o fs e d i m e n t a r ys t r u c t u r e s
a c h a r a c t e r i s t i cs e q u e n c e
and i s normallygraded.
The
14
Plate 3 .
Channel sandstoneintheChinleFormation--the
s a n d s t o n eu n i to c c u r s
i n t h eb a s a l5 0
f t 115 m
l of
~~~,
t h e form'ation. Photograph was taken i nS e c t i o n
10, T. 3 Ne, R. 0 W.
.
~
~
15
sequence i s , fromthebaseupward:
cm) t h i c k , s t r u c t u r e l e s s
c l a s tc o n g l o m e r a t e ,
( 1 ) a 0.5-1.0
f t (15-30
or c r u d e l y c r o s s - s t r a t i f i e d , c l a y -
( 2 ) a 3-10 f t ( 1 - 3
m) t h i c kz o n e
l a r g e - s c a l et r o u g hc r o s s - s t r a t i f i e ds a n d s t o n e ,a n d
of
(3) a
zone o f v a r i a b l e t h i c k n e s s o f s m a l l s c a l e t r o u g h c r o s s s t r a t i f i c a t i o n s a n dm i c r o c r o s s - l a m i n a t i o n sP. a l e o c u r r e n t
flowdirectionasdetermined
from t h e o r i e n t a t i o n o f c h a n n e l
axes and maximum f o r s e t d i p d i r e c t i o n s g a v e
d i r e c t i o n o f N 2'
E (Appendix B ) .
i s composed ofapproximately150
The s h a l e u n i t
m ) o fi n t e r c a l a t e ds h a l e
and s i l t s t o n e .
f t (46
The broad
, low
N
IM Ranch is covered w i t h r e d s o i l
v a l l e yn o r t ho ft h e
erodedfrom
a mean flow
t h i sn o n r e s i s t a n ts h a l eu n i t .
Only t h eu p p e r
25-30 f t (8-9 m) o ft h es h a l eu n i t ,i m m e d i a t e l yb e n e a t h
a
i s e x p o s e d .I nt h ec l i f f
ridgecappedbyDakotaSandstone,
f a c e t h e rock i s dominantly a r e d t o l a v e n d e r , s i l t y ,
s l i g h t l yc a l c a r e o u s ,b e n t o n i t i c ,m o t t l e ds h a l e .
0.5-2.0
f t (0.15-0.6
m ) o ft h es h a l e
The upper
is w h i t e ,p r o b a b l yt h e
r e s u l t o fl e a c h i n gb yg r o u n dw a t e rw h i c hp e r c o l a t e dt h r o u g h
theporousDakotaSandstone.
%e C h i n l e s t r a t a r e p r e s e n t
bed" d e p o s i tt h a ta c c u m u l a t e d
c o a s t a lp l a i n .
a c l a s s i c . c o n t i n e n t a 1" r e d on a b r o a dn o r t h e a s t - s l o p i n g
The h i g hs h a l et os a n d s t o n er a t i o
and t h e
sequence and t y p e of s e d i m e n t a r y s t r u c t u r e s i nt h es a n d s t o n e
u n i t i s s u g g e s t i v e of d e p o s i t i o n as p o i n t - b a r s i n l a t e r a l l y
migrating
, mixed-load , meandering
Galloway ( 1 9 7 7 ) .
streams a s d e s c r i b e d b y
Wood f r a g m e n t sa n dr o o tm o t t l i n g ,
a lack
16
i n theshale
o fp r i m a r ys e d i m e n t a r ys t r u c t u r e s
member,and
" o x i d i z e d "c o l o ra r ec h a r a c t e r i s t i c sg e n e r a l l ya s s o c i a t e d
as f l o o d p l a i n s
w i t h s u b a e r i a lt e r r e s t r i a le n v i r o n m e n t ss u c h
thatdevelopadjacenttomeanderingstreamchannels.
O ' S u l l i v a n ( 1 9 7 7 ) hasproposed
a s i m i l a rd e p o s i t i o n a l
f o r much of t h e C h i n l e s t r a t a c r o p p i n g o u t
model
i n New Mexico.
CretaceousSystem
Approximately 1 7 0 0 f t ( 5 2 0 m) o f C r e t a c e o u s s t r a t a a r e
e x p o s e di n
t h e mapped area.
are c o n f i n e d t o a t r i a n g u l a r - s h a p e ds e g m e n t
C r e t a c e o u sr o c k s
west o ft h e
!the l a r g e s te x p o s u r e so f
Red Lake f a u l t ( P l a t e
4).
A smallexposureof
is t h e
Csevasse Canyon Formation,northofAlamocitaCreek,
onlyCretaceousstrata
t h a t c r o p so u t
on t h e e a s t s i d e o f
t h e Red L a k e f a u l t .
In e a r l i e r s t u d i e s , c o r r e l a t i o n s o f C r e t a c e o u s s t r a t a
b e t w e e ni s o l a t e do u t c r o pa r e a s
were b a s e dp r i m a r i l yo n
c o u n t i n g t h e number o fs a n d s t o n e s
t h es e q u e n c e
b a s i s .R e c e n t
and a t t e m p t i n g t o
upwardfrom
t h eb a s eo f
match these on a one-to-one
and o n g o i n gi n v e s t i g a t i o n so ft h er e g i o n a l
Cretaceousstratigraphybystaff
members of t h e United
S t a t e sG e o l o g i c a lS u r v e ya n dt h e
New Mexico Bureau o f Mines
and M i n e r a lR e s o u r c e sh a v er e s u l t e di ne x t e n s i v er e v i s i o no f
,
t h e l i t h o s t r a t i g r a p h i ct e r m i n o l o g yo fC r e t a c e o u s
c r o p p i n go u ti nt h e
San Juan, Acoma , andZuni
In t h e a r e a mapped i n t h i s s t u d y , f i v e
t i o n s ,r a n g i n gi na g e
fromCenomanian
strata
basins.
d i s t i n c t forma-
t oC o n i a c i a n ,h a v e
"
Plate 4 .
Cretaceous s t r a t ae x p o s e do nt h ee a s ts l o p eo f
CrossMountain--thesection
i s composed of
approximately1700 f t ( 5 2 0 m) o fi n t e r b e d d e d
c l i f f - f o r m i n gs a n d s t o n e s
and s h a l e s . The red
s h a l eu n i ti nt h ef o r e g r o u n d
i s C h i n l es h a l e .
D
18
i s shown i n
b e e nd e l i n e a t e d .
The C r e t a c e o u ss t r a t i g r a p h y
F i g u r e s 4 and 5.
These l i t h o s t r a t i g r a p h i c u n i t s r e p r e s e n t
s e d i m e n t st h a ta c c u m u l a t e di nt h r e ed e p o s i t i o n a le n v i r o n ments:
(1) o f f s h o r em a r i n e ,
( 2 ) coastap
l a r a l i ca n d
( 3 ) c o n t i n e n t a lf l u v i a l .
Dakota Sandstone
i s theDakotaSandstone.
The b a s a lC r e t a c e o u su n i t
r e f e r e n c es e c t i o nf o rt h eD a k o t a
n o l o g yi n t ot h e
Meek and
of Dakota,Nebraska.Herrick
Hayden ( 1 8 6 1 )i nt h ev i c i n i t y
( 1 9 0 0 ) was a p p a r e n t l y t h e
was d e s c r i b e db y
The
t h e Dakota termi-
f i r s t t oe x t e n d
Acoma b a s i n .R e g i o n a ls t u d i e so ft h ei n t e r -
tonguedrelationsofmarineandnonmarineCretaceousrocks
i nn o r t h w e s t e r n
New Mexico have shown t h a t i n
is n o t a simple,
and Acoma b a s i n st h eD a k o t aS a n d s t o n e
is s p l i ti n t os e v e r a l
s i n g l es a n d s t o n eb o d y ,b u t
s a n d s t o n ep a c k a g e s
t h e San Juan
by i n t e r v e n i n g t o n g u e s o f
discrete
Mancos S h a l e .
I ng e n e r a l ,t h eD a k o t at o n g u e sm e r g et o
become a s i n g l e u n i t
n e a r t h e New Mexico-Arizonaborder.In
t h e map area t h r e e
Dakota u n i t sa r er e c o g n i z e d ,t h e s e
g r a p h i co r d e r :
(1) DakotaSandstone(mainbody),
Paguatetongue,and
Dakota Sandstone
a r e , i na s c e n d i n gs t r a t i (2.)
( 3 ) Twowellstongue.
Main Body
Within t h e Acoma b a s i n t h e mainbody
Sandstonerangesfrom
area ( T o n k i n g ,1 9 5 7 )t o
6 f t ( 2 m ) t h i c ki n
94 f t ( 2 9
o f t h e Dakota
the Puertecito
m ) t h i c k i nt h e
19
NONMA:
I
Gallup ss.
upward
Conlacion
Turonian
800 i t .
D Cross St
'
Fife Ranch
7
.
.I
fining-
\
Mb.-
,
maximum
regresston
Carthage M
600 fr.
Atarque Mb
Rio Salado Sh
400 f t .
-
Twowells
ss.
Whitewater
Arroyo Sh.
Paguate ss.
coarsening.
upward
:I
I
INM Springs
Sh.
-
Dakota ss.
(mainbody)
200 f t .
Tumnian
Cenomanian
upward
1
Figure 4 . Generalized Section of t h e marine,
Cretaceous rocks cropping out In t h e D Cross
Mountain area. Notice t h e c i a s e relation of
coarsening upward sandstone packages IO regressive episodes.
MARlNE
Carthage area
a Two Wells
D Cross M t .
I
b
1
1
NW
undivided
Mesaverde
..
Gr
. - ..
.. . . .
' - .. ...
. . .
I
-.
.
.. Gallup S s . ( Gallego)'<
. .
-
.
.
SE
. _. ._. .
I
>
D Cross Sh.
Pescado Sh.
.' .'Twowells Ss-LL__.
. ~. ._ . .
~
Rio Salado Sh. cn
rn
..
3
3
1,
Y
-
0
Colo.
c
INM Springs Sh.
50 mi
Figure 5. Northwest oriented cross-section
illustrating the relations between Cretaceous rock units
in t h e Two Wells area, Acoma basin( D Cross M t ) and
Carthage area. Modified from Molenaar, 1974 and Hook and Cobban, 1980.
N
0
21
Huckleberry well ( F o s t e r , 1 9 6 4 ) .
part,reflectsthe
V a r i a t i o ni nt h i c k n e s s ,
in
l a c k o f c o n s i s t e n tp l a c e m e n to ft h eu p p e r
b o u n d a r y ,t h o u g ha c t u a lc h a n g e s
i n t h i c k n e s sc e r t a i n l yo c c u r .
I n t h es t u d ya r e a
of t h e DakotaSandstone
t h e mainbody
is
u n i f o r m l y 32 f t ( 1 0 m ) t h i c k .
t h e main body o f
In t h e D CrossMountainquadrangle,
t o o n l ya s
t h e D a k o t aS a n d s t o n e( h e r e a f t e rr e f e r r e d
Dakota or D a k o t aS a n d s t o n e )d i r e c t l yo v e r l i e st h e
Formati.on,andforms
Chinle
a r e s i s t a n tr i d g et h a tc a nb et r a c e d
N
IM ranchhouse
northwardfromtheabandoned
Creek i n Sec. 2 1 , T.
bankofAlamocita
3 N.,
on t h en o r t h
R.
b l o c k s of detachedDakotasandstonehavebeen
“ l e t down” a s
As a r e s u l t ,
theincompetentshalebelowhasbeenremoved.
a l a n d s l i d e - l i k et o p o g r a p h y
i s t y p i c a l l yd e v e l o p e da l o n gt h e
two f o r m a t i o n s .
A s e c t i o n of theDakota
was measuredwhere
8 W.
a small
i n Sec. 2 1 , T. 3 N . ,
a r r o y oc u t so b l i q u e l ya c r o s st h es t r a t a
R.
Due t o
8 W.
t h e underlying C h i n l e s h a l e s ,l a r g e
t h ep l a s t i cb e h a v i o ro f
c o n t a c tb e t w e e nt h e
the
A t t h i sl o c a l i t yt h ee r o s i o n a lb a s a lc o n t a c tw i t h
t h eC h i n l e
is well exposed.
t h eo v e r l y i n g
o c c u r so v e r
The Dakota i s g r a d a t i o n a li n t o
Mancos Shaletongue.
The g r a d a t i o n a lc h a n g e
a stratigraphicinterval’ofapproximately
10 f t
( 3 m ) and is t h e r e s u l t o f a n i n c r e a s e i n t h i c k n e s sa n d
num-
b e ro fs h a l eb e d sn e a rt h et o po ft h eu n i t .
I c h o s et op l a c et h eu p p e rc o n t a c to ft h ef o r m a t i o na t
thetopof
a p r e d o m i n a n t l ys a n d s t o n ei n t e r v a lw h i c hu n d e r -
l i e s d a r k - c o l o r e ds h a l e
more t y p i c a lo ft h e
Mancos.
This
22
l i t h o l o g i cd e f i n i t i o n
is s i m i l a r t o
t h a t usedbyFoster
( 1 9 6 4 ) f o rs u b s u r f a c ec o r r e l a t i o n s
and c o r r e s p o n d st o
a
s l i g h tb r e a ki nt o p o g r a p h y .
No f o s s i l s were c o l l e c t e d from t h e mainbodyof
DakotaSandstone.Regionalstudiesindicate
C r e t a c e o u su n i t
age.
the
that the basal
i s o fe a r l i e s tL a t eC r e t a c e o u s( C e n o m a n i a n )
A Thatchee
r quivalent
( m i d d l e Cenomanian)
(Cobban,
1977a) was c o l l e c t e d from n o d u l a rl i m e s t o n ec o n c r e t i o n si n
t h e o v e r l y i n g Mancos Shaletongue
2 0 f t (6 m ) above t h e t o p
?his is t h e
o f t h e m a i n body o ft h eD a k o t aS a n d s t o n e .
stratigraphically lowest occurrence of
w i t h i n t h e s t u d ya r e a .
t a c ti n d i c a t e s
a diagnosticfauna
%e g r a d a t i o n a l Dakota-Mancoscon-
a s i m i l a ra g ef o rt h eD a k o t a .
The DakotaSandstonecan
be d i v i d e di n t o
(1) a b a s a lc o n g l o m e r a t i cs a n d s t o n e
three p a r t s :
u n i t , ( 2 ) a middle shale
u n i t , and ( 3 ) a nu p p e rs a n d s t o n eu n i t .' I h e s ed i v i s i o n sa r e
used i n f o r m a l l yi n
t h i s study.
The lower 1 6 f t ( 5 m ) of theDakota
bedded,
is a massively
t r o u g hc r o s s - s t r a t i f i e d ,w e l l - i n d u r a t e d
posedofsmallpebbleconglomerates
medium-grainedsandstones
t h i c k e r andmore
and t h e u n i t
u n i t com-
and s l i g h t l y p e b b l y ,
(Plate 5).
C o n g l o m e r a t eb e d sa r e
numerous i n t h e b a s a l p a r t o f t h e e x p o s u r e
is g r a d e d .
T e x t u r a l l y , t h e lower p a r t o f theDakota
subequalamountsofsandandgravel,
mon s i z e - g r a d e .
i s composed of
w i t h sandthemore
?he l a r g e rc o n s t i t u e n t sa r ew e l l - r o u n d e d ,
equantpebblesofblackchert
andvariously-colored
com-
23
Plate 5 .
B a s a lc h e r tp e b b l ec o n g l o m e r a t ei nt h em a i nb o d y
of t h e Dakota Sandstone--the u n i t i s a f i n i n a
upward sequence.Photograph
was t a k e ni nS e c t i o n
8 W.
21, T. 3 N.,R.
24
quartzite.
Many o f t h e s e c l a s t s were probablyreworkedfrom
T r i a s s i c or J u r a s s i cs t r a t a .G r a v e ls i z em a t e r i a lo c c u r s
d i s c r e t el e n t i c u l a rb e d st h a tr a n g ei nd i m e n s i o n
in
from a
s i n g l e pebble t o 1 f t ( 3 0 cm) or more i n t h i c k n e s s .
conglomeratebeds
a distance of
These
often gradelaterallyintosandstoneover
a few f e e t .
The c o a r s e - g r a i n e db e d sa r e
well s t r a t i f i e d w i t h
large,
s h a l l o wt r o u g hc r o s s - s t r a t i f i c a t i o nb e i n gt h ed o m i n a n t
m e n t a r ys t r u c t u r e .P l a n a rw e d g e - s e t st h a tr a n g e
1.0'ft
sedi-
from 0 . 1 t o
( 3 t o 30 cm) t h i c k are t h e o n l y c r o s s - s t r a t i f i c a t i o n
type o b s e r v e di nt h ei n t e r v e n i n gs a n d s t o n eb e d s .
lower u n i t is a s e c t i o n composedpredomi-
O v e r l y i n gt h e
n a n t l yo fs h a l e s
w i t h a few t h i ns a n d s t o n eb e d s .
The s h a l e s
a r es i l t y ,b l a c k ,v e r yc a r b o n a c e o u s ,n o d u l a ra p p e a r i n g ,
t h i n -t o
medium-bedded.
The i n t e r c a l a t e ds a n d s t o n e s
o n l y a few i n c h e s t h i c k , l a t e r a l l y c o n t i n u o u s , s i l t y ,
ately carbonaceous, poorly sorted
f t (15-30 c m ) t h i c k b e d s
ately indurated
are
moder-
, fine-grainedsubarkoses.
,is composed o f numerous
The upperunitoftheDakota
0.5-1.0
and
of l i m o n i t e - s t a i n e d , moder-
, calcareous , moderately sorted, fine-grained
q u a r t z a r e n i t e s andsubarkoses.
r a t e db yt h i nb e d s
These s a n d s t o n e sa r es e p a -
of black s h a l e .
The o n l y s t r u c t u r e s
p r e s e n tw i t h i nt h e s es a n d s t o n e s
are b r a n c h i n gb u r r o w st h a t
r e s e m b l eP l a n o l i t e sw h i c ho c c u r
a s c a s t s on t h e s o l e s o f t h e
s a n d s t o n eb e d s .
The s a n d s i z e c o n s t i t u e n t s
r o u n d e dq u a r t zg r a i n s
a r e d o m i n a n t l ys u b r o u n d e dt o
(86-90%) t h a t a r e g e n e r a l l y s i n g l e
25
s i z e compo-
c r y s t a l s w i t h u n d u l o s ee x t i n c t i o n .o t h e rs a n d
n e n t si n c l u d ec h e r t
(lo%),
s u b r o u n d e dz i r c o n( t r a c e )
k a o l i n i z e dp o t a s s i u mf e l d s p a (r t r a c e () A p p e n d i x
framework g r a i n s a r e c l o s e l y p a c k e d
o r convex-concaveboundaries.
A).
Pressure s o l u t i o n i n go ft h e
i s common.
Cementation was a c c o m p l i s h e d p r i m a r i l y b y
on t h e q u a r t z g r a i n s
i n f i l l i n go fi n t e r g r a n u l a rv o i d s
The
and d i s p l a y c r e n u l a t e d
q u a r t z a n ds q u a s h i n go fl a b i l ep a r t i c l e s
cipitationasovergrowths
, and
s i l i c a prelater
andby
w i t h calcium c a r b o n a t e i n
a
p a s s i v ep o r e - f i l l i n gs e q u e n c e .A u t h i g e n i cc l a ym i n e r a l sa r e
a l s op r e s e n tw i t h i nt h em a t r i x .
?heDakota
s t r a t a r e p r e s e n t ss e d i m e n tt h a ta c c u m u l a t e d
The t r a n s i t i o n
i n b o t hp a r a l i ca n df l u v i a le n v i r o n m e n t s .
fromnonmarine
f l u v i a lc o n d i t i o n s ,r e p r e s e n t e db yt h eb a s a l
u n i t ,t on e a r s h o r em a r i n ec o n d i t i o n st h a tp r e v a i l e dd u r i n g
t h e accumulation of t h eu p p e ru n i td e v e l o p e da st h er e s u l t
of t h e encroachmentof
sea i n t o t h e
a s h a l l o wC r e t a c e o u s
D
CrossMountainareaduringtheCenomanian.
The l o w e r c o n g l o m e r a t i c s t r a t a o v e r l i e
unconformity.During
a regional
t h e time r e p r e s e n t e db y
streams a t o r
a b l es u r f a c e ,t h ea c t i o no fl a t e r a l l yp l a n i n g
n e a rb a s e - l e v e lp r o d u c e d
a nearpeneplane
planationgravel-sizecomponen'tsreworked
l y i n gT r i a s s i c ,a n dp e r h a p sJ u r a s s i c ,
t h e unconform-
surface.
During
from t h e under-
s t r a t a accumulated as
a stream b o t t o m l a g a n d a s g r a v e l b a r s i n t h e f l u v i a l
system.
The b a s a lc o n g l o m e r a t eu n i tc o n t a i n s
c h a r a c t e r i s t i c s commonly a s s o c i a t e d w i t h b r a i d e d
many o f t h e
stream
1
26
deposits:
base, ( 2 ) c o a r s eg r a i n
(1) s l i g h t l ye r o s i o n a l
s i z e , ( 3 ) m o d e r a t es o r t i n g ,
( 4 ) . d o m i n a n c eo fu n i d i r e c t i o n a l
p l a n a rc r o s s - l a m i n a t i o n s ,a n d( 5 )l a c ko ff o s s i l s( D o e g l a s ,
1962).
D e p o s i t i o no ft h ef l u v i a ls e d i m e n t so c c u r r e da st h e
seas b e g a nt ot r a n s g r e s si n t ot h ea r e a ,
LateCretaceous
r e d u c i n gt h er e g i o n a gl r a d i e n t J. u d g i n gf r o mt h ew i d e s p r e a d
extentofthebasalunitanextensivefluvial
h a v ee x i s t e di nt h e
andMcKnight
area.
S t o k e s( 1 9 5 0 ) ,
complexmust
Reeside ( 1 9 5 7 ) ,
similar s e t t i n g s i n
(1968)haveenvisioned
i n t e r p r e t i n gt h i n ,p e r s i s t e n tb a s a lc o n g l o m e r a t e si nt h e
Rocky M o u n t a i nr e g i o n P
. a l e o c u r r e n td a t ao b t a i n e df r o m
c r o s s - s t r a t i f i c a t i o ni nt h el o w e ru n i ti n d i c a t e
westerlypaleoslope(Appendix
Ihe m i d d l e s h a l e u n i t
.
is s l i g h t l y b i o t u r b a t e d , v e r y
a few i m m a t u r es a n d s t o n ei n t e r -
c a r b o n a c e o u s ,a n dc o n t a i n s
beds..
B)
a south-
No m e g a f o s s i l s were observed i n t h e s h a l e i n t e r v a l .
The u p p e rs a n d s t o n eu n i t
is composed o fn u m e r o u sb i o t u r b a t e d
sandstoneandshalebedsthatgradeverticallyintooffshore
muds (Mancos S h a l e )c o n t a i n i n go p e nm a r i n ef o s s i l s .T h i s
mudstoneandsandstonesequencerepresents
mud c o a s t l i n e and n e a r s h o r eb a r
a transgressive
complex t h a t accumulated on
a s a n d - s t a r v e dc o a s t l i n ed u r i n gt h ee a r l i e s tm a r i n e
g r e s s i o n i n t o t h e area.
S i m i l a r mud-dominated
havebeendescribedbyFisherand
Louisiana Gulf Coast.
transshorelines
Brown (1972)fromthe
27
Paguate Tongue
..
Near t h e town o fP a g u a t e ,
New Mexico,Landisandothers
6 2 f t (19 m) of
(1973) measured and d e s c r i b e da p p r o x i m a t e l y
s a n d s t o n ea n ds i l t s t o n et ow h i c ht h e ya p p l i e dt h e
PaguateSandstonetongueof
name
t h e DakotaSandstone.In
same s t u d y , t h e y d e m o n s t r a t e d t h a t t h e P a g u a t e
t h e main body of t h e DakotaSandstonenear
Mexico.Inthe
D Cross a r e a 32 f t ( 1 0
o u ta p p r o x i m a t e l y
this
mergedwith
Grants, New
m ) o fs a n d s t o n ec r o p
1 0 0 f t (30 m ) above t h e mainbody
of t h e
D a k o t aS a n d s t o n e .B a s e do nt h es t r a t i g r a p h i cp o s i t i o n ,
l i t h o l o g y , and a g e , t h e s e s t r a t a
P a g u.a t.eS a n d s t o n ee q u i v a l e n t s .
were d e t e r m i n e dt ob e
No P a g u a t es t r a t ac r o po u t
at D
east, of D Cross M o u n t a i n .T h e r e f o r e ,t h eo u t c r o p s
Cross M o u n t a i nr e p r e s e n tt h es o u t h e a s t e r n m o s te x t e n s i o no f
the sandstone
..
?he Paguatethickensandmergeswiththemainbodyof
t h e DakotaSandstonein
The
a n o r t h w e s t w a r d l yd i r e c t i o n .
were derived from
geometryoftheunitindicatesthestrata
t h e west o r n o r t h w e s t( L a n d i sa n do t h e r s ,1 9 7 3 ) .
stratificationmeasurementsinthe
Cross-
D Cross Mountainand
Pueblo Viejo a r e a s show a u n i d i r e c t i o n a l s o u t h e r l y p a l e o c u r r e n tp a t t e r n( A p p e n d i xB ) - - o b l i q u et ot h ei n f e r r e d
C r e t a c e o u ss h o r e l i n ea tt h a t
time.
This s u b s t a n t i a t e st h e
c o n c l u s i o n so fL a n d i sa n do t h e r s( 1 9 7 3 )t h a t
p r o g r a d e di n
a southeasterlydirection.
t h e Paguate
28
i s p o o r l ye x p o s e di nt h e
The Paguatetongue
M o u n t a i na r e a ,c r o p p i n go u to n l ya s
D Cross
a l o wd i s c o n t i n u o u s
r i d g e formed a t t h e base o f t h e slopebeneath'Ityowells
s a n d s t o n ei n
3 N.,
Sec. 8, T.
a p a r t i a ls e c t i o n
A t t h i sl o c a l i t yo n l y
8 W.
R.
composed o f 15 f t ( 5 m ) o f s t r a t a
i s concealed
e x p o s e d ;f u r t h e rt ot h es o u t ht h eP a g u a t e
b e n e a t hQ u a t e r n a r ya l l u v i u m .
d o e s I however
t h es t u d y
.thePaguate
I
A c o m p l e t es e c t i o no fP a g u a t e
1 m i ( 1 . 6 km) n o r t h o f
cropoutapproximately
area a l o n gt h ec o u r s e
of the
Rio SaLado,andthere
is 32 f t ( 1 0 m ) t h i c k( F i g u r e
s e r v e da m m o n i t ec o l l e c t e df r o mt h e
a s P a r x a c s o m p s o c e r a sl a n d i s i ,
a well pre-
middle o ft h eu n i ti n
Rio S a l a d o .
(S. Hook, o r a l commun.,
6).
was determinedfrom
The a g eo ft h eP a g u a t e
e x p o s u r e sa l o n gt h e
is
The ammonite was i d e n t i f i e d
a l a t e m i d d l e Cenomanianform
L a n d i sa n do t h e r s
1978).
(1973)
of A c a n t h o c e r a sa m p h i b o l u m ,a l s o
h a v ec o l l e c t e ds p e c i m e n s
a
t h e lower 2 5 f t ( 8 m ) o ft h e
Cenomanianammonite,from
PaguateSandstonenearLaguna,
New Mexico.
A s t h eP a g u a t e
is a t l e a s t 100 f t ( 3 0 m) s t r a t i g r a p h i c a l l y l o w e r t h a n t h e
l a t e CenomanianTwowells
t o n g u e , a middle Cenomanianage
for
t h eP a g u a t ea p p e a r sr e a s o n a b l e .
%he Paguate is a coarsening-upwardsequenceoffine-to
m e d i u m - g r a i n e ds a n d s t o n et h a t
is g r a d a t i o n a lf r o mt h eu n d e r -
l y i n g Mancos S h a l e ( P l a t e 6 ) .
u n i t is g r e e n - g r a y( 1 0
GY 5/2),
c a l c a r e o u s ,a n dm o d e r a t e l ys o r t e d .
s i v e l y beddedand,
The lower 2 0 f t ( 6 m ) o ft h e
silty,moderatelyindurated,
This' s i l t y zone is mas-
as t h e result o fi n t e n s eb i o t u r b a t i o n ,
29
Depositional environment
Whitewater
Arroyo Sh.
gradational
contact
Off-shore
muds
Upper shoreface
'-l>ioturbated
' \
bioturbated,
sandy,
grey shales, locally
fossiliferous
\
\
Lower shoreface
zones
Transitional to
Off-shore mud
I
-gradational contact
INM Spring
Shale
mud
Off-shore muds
I
10 f t
sand
\\\
--11'
I
0 ft
tabular
cross-stratification
horizontal
laminations
bioturbation
Figure 6 . Stratigraphic section of the Paguate tongue of
the Dakota Sandstone.
The Paguate accumulated a s an
offshore bar sand.
30
Plate 6.
ContactbetweenPaguatetongue
of t h e Dakota
INM Springstongue
of
Sandstone and t h eu n d e r l y i n g
t h e Mancos S h a l e - - t h ec o n t a c t
is gradational.
L i g h t e rc o l o r e da r e a si nt h es h a l ei n t e r v a la r e
b e n t o n i t e sP
. hotograph
was t a k e ni nS e c t i o n
5 r T.
3 N . R 8 W . , Wiley Mesa quadrangle.
I
31
h a s a swirled appearance.
Due t o the h i g hc l a yc o n t e n t
of t h e u n i t , t h e r o c k
t h eb a s e
F o s s i l s are o f t e np r e s e n t
of
is s p h e r o i d a lw e a t h e r i n g .
and includeunabradedinoceramids
and ammonites.
The l o w e rp a r to f
I
!
o fb i o t u r b a t e d
t h i nt o
t h e u n i t is o v e r l a i n b y
, h o r i z o n t a l l yl a m i n a t e dt o
~
10 f t ( 3 m)
structureless,
t h i c k wavy bedsofmedium-grainedsandstone.Iron
a reddish-orange
oxidewithintheburrowedzonesimparts
(10
R 4 / 6 )c o l o rt ot h es t r a t a .
The upper 2 f t ( 6 1 cm) of t h e Paguate i s a r e s i s t a n t ,
white ( N 9 )
,
cross-stratified
, well-sorted, medium-grained
The c r o s s - s t r a t i f i c a t i o n so c c u r
g l a u c o n i t i cq u a r t z a r e n i t e .
i n s e t s u p t o 1 f t ( 3 0 cm) t h i c k and a r e o f t h e p l a n a r
wedge-shape type.
The c r o s s - l a m i n a ea r ei n c l i n e du n i f o r m l y
t ot h es o u t h - s o u t h e a s t .
Fine-tomedium-grainedquartzcomprisesfrom94-95%of
t h ef r a m e w o r kc o n s t i t u e n t si n
examined.
t h e f i v et h i n - s e c t i o n s
The q u a r t zg r a i n sa r eg e n e r a l l yf r e eo fi n c l u -
s i o n s and h a v e s t r a i g h t e x t i n c t i o n ; a l t h o u g h g r a i n s w i t h
n e e d l e - s h a p e dr u t i l ei n c l u s i o n s
e x t i n c t i o na r ep r e s e n t .
s u b r o u n d e dt os u b a n g u l a r .
and g r a i n sw i t hu n d u l o s e
Most g r a i n sa r es u b e q u a n t
Other c o n s t i t u e n t st h a to c c u r
amounts greater t h a n 1%i n c l u d e :r o u n d e d
5 / 6 )g l a u c o n i t e
and
( 2 % ) , greychert
, medium-green(5G
( 2 % ) , p o t a s s i u mf e l d s p a r
(l%), and s i l t s t o n e (1%). Trace a m o u n t so fp a r t i a l l y
d e g r a d e db i o t i t e
A)
*
andmuscovite
were a l s or e c o r d e d( A p p e n d i x
in
32
The rock t e x t u r e r a n g e sf r o mm o d e r a t e l yo v e r p a c k e d ,i n
which t h e g r a i n s h a v e s h o r t s t r a i g h t c o n t a c t s , t o t i g h t l y
packed i n whichsutured,concave-convex,
g r a i nc o n t a c t s
mica,
a r e t h ed o m i n a n tt y p e .S o f tg r a i n so f
a r e deformed because o ft h e
g l a u c o n i t e , andmudstone
compact
or l o n g ,s t r a i g h t
ion.
Calcite and s i l i c a a r e t h e p r i m a r y c e m e n t i n g a g e n t s .
S i l i c a was t h e e a r l i e s t p r e c i p i t a n t .
derivedfromsolutionofquartz
The s i l i c a cement was
a t graincontacts
r e p r e c i p i t a t e da sq u a r t zo v e r g r o w t h sw i t hc r y s t a l
terminations.
t a l l i n ew i t h
and
face
Calcite cement i s f i n e l yt oc o a r s e l yc r y s -
some c r y s t a l s a t t a i n i n g
( 7 . 6 mm) i nd i a m e t e r .
numerousframework
a s i z e up t o 0 . 3 i n .
The l a r g e rc r y s t a l se n c o m p a s s
g r a i n s and a r e t h e p r o d u c to fa g g r a d i n g
n e o m o r p h i s mP
. a r t i a rl e p l a c e m e n o
t f r a m e w o r kc o n s t i t u e n t s
by t h e c a l c i t e cement i s .common.
The PaguateSandstone
is sandwichedbetweenopenmarine
Mancos S h a l eu n i t sa n dr e p r e s e n t sa no f f s h o r em a r i n es a n d
is g e n e r a l l y
bar c o m p l e x .G l a u c o n i t ei nt h es a n d s t o n e
I
ascribedto
a normalmarineenvironment
(
Cloud,1955),and
t h ep r e s e n c eo fa no p e nm a r i n ef a u n ap r o v i d e ss t r o n gs u p p o r t i v ee v i d e n c ef o rt h em a r i n eo r i g i no ft h er o c k .
s e q u e n c eo fp r i m a r ya n db i o g e n i cs e d i m e n t a r y
t e x t u r e so b s e r v e di n
d u r i n gp r o g r a d a t i o no f
s t r u c t u r e s and
t h e r o c k i s s i m i l a rt ot h o s ep r o d u c e d
a s h a l l o wo f f s h o r em a r i n es a n d
described by Carter(1978)andReineck
M i g r a t i o no fa no f f s h o r e
The
bar as
and Singh(1975).
sand bar will produce a c o a r s e n i n g -
33
upwardsandstonepackage
as b i o t u r b a t e d o f f s h o r e
muds a r e
o v e r r i d d e nb yc o a r s e - g r a i n e d ,c r o s s - b e d d e db a rc r e s t
s e d i m e n t s ( R e i n e c k andSingh,1975).
The observedcharac-
t e r i s t i c s o ft h eP a g u a t ec l o s e l ya p p r o x i m a t et h i s
model f o r
as
a p r o g r a d i n go f f s h o r es a n db a r .P a l e o c u r r e n ti n d i c a t o r s ,
well a s r e g i o n a l g e o m e t r i c r e l a t i o n s , i n d i c a t e t h a t p r o g r a d a t i o n was t o t h e s o u t h e a s t .
TwowellsTongue
<
The !lMowells tongue was named byPike
(1947) for
exposures near Two Wells, New Mexico, i n t h en o r t h w e s t e r n
p a r to ft h e
state.
a s a l e n t i l o ft h e
P i k e ( 1 9 4 7 ) o r i g i n a l l yi n c l u d e dt h eu n i t
Mancos S h a l e , b u t s u g g e s t e d t h a t t h e
sandstonebodymightbe
more c l o s e l y r e l a t e d
S a n d s t o n e ,S u b s e q u e n ti n v e s t i g a t i o n s
t o theDakota
by Dane and o t h e r s
( 1 9 7 1 ) h a v ed e m o n s t r a t e dt h a tt h eW o w e l l sm e r g e sw i t ht h e
Dakota near Window Rock, Arizona.
The u n i t i s now con-
a tongue of theDakota.
s i d e r e dt ob e
Dane and o t h e r s( 1 9 7 1 )
were t h e f i r s t t o a p p l y t h e
Twowells t e r m i n o l o g y t o s t r a t a i n t h e
D Cross-Alamo Day
S c h o o la r e a .T h e i ru s a g es u p e r c e d e st h ee a r l i e rd e s i g n a t i o n
o f R e s Hermanos S a n d s t o n eu t i l i z e db y
Tonking(1957),
Given (1958) , a n dJ i c h a( 1 9 5 8 ) .
R e g i o n a l l y ,t h e
sheet-sand.
Herrick ( 1 9 0 0 ) ,
nYowells is a s o u t h e a s t w a r dt h i n n i n g
Dane and o t h e r s( 1 9 7 1 )r e p o r t e dt h a t h es a n d -
s t o n ep a c k a g ee x t e n d s
a t l e a s t 140 m i ( 9 0 km) s o u t h e a s t w a r d
from Window R o c k , Arizona,andhas
a maximum widthof
200 m i
34
(125 k m ) .
In t h e s o u t h e r n Acoma b a s i n , i m m e d i i a t e l y e a s t o f
D Cross Mount a i n , t h e
Twowells c o n s i s t s o f
c o n t i n u o u ss a n d s t o n el e n t i l s( T o n k i n g ,
1958).
a seriesof
dis-
1957, andGivens,
The Twowells i s n o tp r e s e n ti nt h eR i l e ya r e a
(Massingill, 1979).
t h e Twowells is t h e
In t h e D CrossMountainquadrangle,
f i r s t r e s i s t a n tc l i f f - f o r m i n gu n i ta b o v et h e
(Plate 7).
S t r a t i g r a p h i cs e p a r a t i o no f
D a k o t ab ya ni n t e r v e n i n g
t h e Twowellsand
Mancos ShaletongueandPaguate
Sandstone i s 209 f t ( 6 4 m ) on t h e e a s t
Mountain.
DakotaSandstone
s i d e of D C r o s s
The Twowells is 4 4 f t (13 m ) t h i c k ( F i g u r e 7 ) .
Ihe uppercontactoftheTwowellswiththeRioSalado
S h a l et o n g u eo ft h e
Mancos S h a l e i s poorlyexposed.Inmost
a 4-6 f t ( 1 2 - 2 4 cm) t h i c k zoneof
a r e a st h e r ea p p e a r st ob e
i n t e r b e d d e ds a n d s t o n e sa n dd a r ks h a l e sn e a rt h et o p
unit.
The u p p e rc o n t a c t
r e s i s t a n ts a n d s t o n e
of t h e
of t h e l a s t
was p l a c e d a t t h et o p
bed.
is
The lowerTwowellscontact
g r a d a t i o n a l and conformablewiththeunderlyingWhitewater
Arroyotongueofthe
Mancos Shaleand
where sand is g r e a t e r t h a n
No d i a g n o s t i c f o s s i l s
i nt h e
D C r o s s area.
was drawn a t t h e p o i n t
5 0 % byvolumeof
t h e rock.
were c o l l e c t e d from t h e Twowells
E x t e n s i v ec o l l e c t i n g
from t h et o po f
t h e Twowells i nt h eP u e r t e c i t oa r e ah a sy i e l d e d
a late
Cenomanian age fauna ( S . Hook, o r a l commun.,
D C r o s sa r e aP y c n o d o n t en e w b e r r i ,
In t h e
a l a t e Cenomanian t o e a r l y
T u r o n i a no y s t e r ,a n dS c i p n o c e r a sg r a c i l e ,
ammonite,occurwithin
1979).
a l a t e Cenomanian
1 0 f t ( 3 m) a b o v et h et o p
of t h e
1
35
r
Plate 7.
C l i f f - f o r m i n go u t c r o p
of 'Ibuowells' sandstone--the
Twowells is theorangeweathering
u n i t formingthe
was
second c l i f f inthephotograph.Photograph
5 ? T. 3 N . , R. 8 W.
Wiley Mesa
t a k e ni nS e c t i o n
quadrangle.
36
Depositional Environment
Rio Salado
Shal c
Off-shore
muds
s h a r p , f l a t contact
,
. . . ,
..
.$.
..
bioturbated
"
shale$ break
.
Lower Shoreface
.
'T a b uwl ae rd g e s e t s
Upper
shoreface
erosional contact
overlain by c l a y - c l a s t c o n y .
burrowed with vague
horizorltal
laminations
Lower
shoreiace
-
c
gradational contact
W hitewater
Arroyo
Sh.
mud
II
Off-shore muds
sand
10 ft
0 ft
Figure 7. Stratigraphic section of t h e Twowells
tongue of the Dakota Sandstone.
1
37
This i n d i c a t e s a l a t e Cenomanian a g e f o r t h e
Twowells.
sandstone u n i t .
I n a n o r t h w e s t e r l yd i r e c t i o n ,
i s e s s e n t i a l l ys y n c h r o n o u s
(S.
t h e Twowells
Hook, o r a l commun., 1 9 7 8 ) .
Dane and o t h e r s (1971) h a v er e p o r t e dt h a tt o w a r dt h e
s o u t h w e s t t h e !Itvowells r i s e s . s l i g h t l y s t r a t i g r a p h i c a l l y .
is a
In t h e D CrossMountainareatheTwowells
coarsening-upwardsequencecomposedpredominantly
bioturbated
of
, thick beds of calcareous, moderately sorted,
mature, s i l i c a c e m e n t e d ,f i n e - g r a i n e dg l a u c o n i t i cc h e r t a r e n i t e s and subarkoses(Appendix
within depositional u n i t s ,
z o n e sc o n s i s to fs p a r s eb u r r o w s
OK
The b i o t u r b a t e d
A).
, f l a t - l y i n g ,b r a n c h i n g ,
o f a b u n d a n tc i r c u l a r
0.1 in.
(2.5
mm) d i a m e t e rb u r r o w st h a ta r ec o n c e n t r a t e da l o n gb e d d i n g
planes.
The d i f f e r e n c ei nt y p e
andabundance
p r o b a b l y r e f l e c t s r a t eo fs e d i m e n t a t i o n .
theunit,
dark-brown
o f t h eb u r r o w s
Near t h em i d d l eo f
a zone t h a t i s composed o fo n e
o r more b e d s o f
( 5 YR 2/1), t a b u l a r c r o s s - s t r a t i f i e d ,
coarse-grained sandstone
medium- t o
, containing squashed clay clasts
i m p a r t s a bandedappearanceto
the strata.
,
The upper 1 0 f t
( 3 m ) o € t h e Twowells i s composed o f medium b e d so ff i n e -
grained
, b i o t u r b a t e ds a n d s t o n e .M i n e r a l o g i c a l l y
the
I
Twowells i s s i m i l a rt ot h eP a g u a t eS a n d s t o n e .
The geometryandthepresenceof
g l a u c o n i t ew i t h i nt h e
accumulatedas
a marinefaunaand
Twowells s u g g e s t s t h a t
a n e x t e n s i v eo f f s h o r em a r i n e
the s t r a t a
s h e e t s a n dt h a t
d e v e l o p e dd u r i n ga j m a r i n er e g r e s s i o n T
. h i n n i n go f
s a n d s t o n ep a c k a g et ot h es o u t h e a s t ,t h ' ed i s t r i b u t i o no f
I
the
a
38
s u i t e of m e t a m o r p h i cm i n e r a l s
( O w e n s , 1 9 6 3 ) ,a n dt h ed i p
d i r e c t i o no ft a b u l a rc r o s s - l a m i n a t i o n ss u g g e s tt h a t
the
s e d i m e n t s were d e r i v e d from thenorthwest(Appendix
B)
C h a r a c t e r i s t i c so f
.
t h e r o c kc l o s e l yr e s e m b l et h o s e
p r o d u c e di nt h el o w e ra n du p p e rs h o r e f a c ee n v i r o n m e n t so f
recent s h a l l o w m a r i n e o f f s h o r e b a r s
( R e i n e c k andSingh,
The
1975) and a n c i e n st h o r e f a c ed e p o s i t s( M o l e n a a r 1
, 973).
lower p a r t o ft h eu n i tr e p r e s e n t sl o w e rs h o r e f a c et o
transitional,bioturbated,siltysands
below wave base.
The u p p e rp a r t
t h a t accumulated
o f t h e unit is cross-
s t r a t i f i e d and c o n t a i n s mud r i p - u pc l a s t s .
mese sediments
accumulated i n a g i t a t e dw a t e r sa b o v en o r m a l
wave b a s e ,p e r -
hapson
a b a rc r e s t .F o s s i l s
and b u r r o w sa r e ,e x p e c t e d l y ,
n o t common i nt h i sh i g he n e r g ye n v i r o n m e n t .
%e ' h o w e l l sa p p e a r st or e p r e s e n t
t h a ta c c u m u l a t e dd u r i n g
K i r k , 1977).
a s h o r e f a c es a n d s t o n e
a r e g r e s s i v es e g u e n c e( P e t e r s o na n d
However, s e v e r a lf a c t o r s
a
l e n d e v i d e n c et o
F i r s t , t h e Twowells i s
d i f f e r e n to r i g i nf o rt h es t r a t a .
"time-flat" from P u e r t e c i t o , New Mexico, t oS h i p r o c k ,
New
Mexico, i n a d i r e c t i o no b l i q u et ot h eC r e t a c e o u ss h o r e l i n e ;
t h i s phenomenon i s n o t g e n e r a l l y a t t r i b u t e d t o t r a n s g r e s s i v e r e g r e s s i v ec y c l e s S
. e c o n d t, h e
i nc o n s i d e r a b l eq u a n t i t i e s ,
p e r i o d so f
Twowells c o n t a i n sg l a u c o n i t e
which is s u g g e s t i v eo fl o n g
slow or n o n d e p o s i t i o n .T h i r d ,t h e r e
l i t h o l o g i ce v i d e n c ew h i c h
i s no
would s u p p o r t a. s h i f t o f t h e
s h o r e l i n ed u r i n gt h ea c c u m u l a t i o no ft h e
Twowells s t r a t a .
An a l t e r n a t i v e d e p o s i t i o n a l m o d e l , w h i c h
has lessconjec-
39
i s t h a tt h el l v o w e l l ss a n d s t o n ea c c u m u l a t e d
t u r a lq u a l i t i e s ,
to the
a s a no f f s h o r eb a rc o m p l e xt h a tp r o g r a d e dp a r a l l e l
s h o r e l i n e .T h i s
would e x p l a i nt h et r a n s i t i o n a ll o w e r
con-
t a c t w i t h open marine s h a l e s , t h e r e g i o n a l “ t i m e - f l a t ’ ’
n a t u r e of t h e s a n d s t o n e u n i t i n
t h ep a l e o s h o r e l i n e ,
a d i r e c t i o np e r p e n d i c u l a rt o
and t h e lack o f l a t e r a l l y r e l a t e d
regressive deposits.
Mancos S h a l e
Mancos S h a l e was t h e name a p p l i e d byCross(1899)
approximately1200
n e a rt h e
f t (366 m ) o fd a r ks h a l et h a tc r o po u t
town of Mancos, Colorado.Inthe
and Acoma b a s i n s o f
to
N e w Mexico
, the
San J u a n , Z u n i
,
Mancos S h a l e is s p l i t
i n t o n u m e r o u st o n g u e sb yi n t e r v e n i n gs a n d s t o n e .u n i t s .
The
i n t e r t o n g u i n g is t o t h e west and s o u t h w e s t ( P i k e , 1 9 4 7 ;
S e a r sa n do t h e r s ,
1 9 4 1 ; andMolenaar,1974).
Shaletongueswere
mapped i n t h e
r a n g l e I. ns t r a t i g r a p h i co r d e r
name)
, WhitewaterArroyo,
INM S p r i n g s
Four Mancos
D Cross Mountain quad-
these a r e :
Rio Salado,and
INM Springs
(new
D Cross.
Tongue
On t h e e a s t e r n s l o p e
of D CrossMountain,approximately
90 f t (27 m ) of Mancos s h a l e s e p a r a t e
sandstones.
t h e PaguateandDakota
This s h a l e i s l a t e r a l l ye q u i v a l e n tt ot h eC l a y
Mesa tongue o f t h e Mancos S h a l e a s d e s c r i b e d
o t h e r s( 1 9 7 3 ) .
by L a n d i s and
A t t h e Clay Mesa s t r a t o t y p e ,t h es h a l es e c -
t i o n i s boundedby
t h e Cubero Member andPaguateSandstone
40
tongueoftheDakotaSandstone.However,theCuberowedgeso u tw i t h i nt h e
Mancos S h a l es o u t ho f
t h e Laguna a r e a (Hook
and o t h e r s , 1 9 8 0 ) and t h e Clay Mesa t e r m i n o l o g yc a n n o tb e
e x t e n d e df r o mt h er e f e r e n c es e c t i o ni n t ot h e
D Cross
In t h i sr e p o r tt h el o w e s ts h a l et o n g u e
Mountain a r e a .
of
t h e Mancos i s named t h e N
IM S p r i n g st o n g u eo ft h e
The name i s d e r i v e d from INM S p r i n g sl o c a t e d
Shale.
28,
T.
Mancos
i n Sec.
R. 8 W.
3 N.,
R e g i o n a l l y ,t h e
N
IM S p r i n g st o n g u et h i n st o
west ( L a n d i sa n do t h e r s ,
t h e north-
1 9 7 3 ) and west (Hook and o t h e r s ,
1 9 8 0 ) as theboundingDakotaSsndstonetonguesmerge.
P i n c h o u tp o i n t so f
p a s s i n gt h r o u g h
Mount Powell,
TWO
Wells,andAtarque,
New
D Cross Mountain, a t t h er e f e r e n c es e c t i o n
Mexico.Northof
o f t h eC l a y
a line
t h e s h a l et o n g u eo c c u ra l o n g
Mesa S h a l e , t h e
N
IM S p r i n g se q u i v a l e n t
( 2 1 m ) t h i c ka n dc o n s i s t s" . . . m o s t l y
clay shale, silty
o f medium-
is 7 0 f t
t od a r k - g r a y
i n part,buthasbentonites,limeyconcre-
t i o n s , and t h i nl i m e s t o n eb e d s "( L a n d i sa n do t h e r s ,
1973).
East o f D Cross Mountain, where t h eP a g u a t eS a n d s t o n e
a b s e n t and t h el o w e s t
Arroyotongueof
is
Mancos s h a l e andoverlyingWhitewater
t h e Mancos S h a l em e r g e ,t h es h a l ei n t e r v a l
h a sb e e nl o o s e l yr e f e r r e dt oa st h eW h i t e w a t e rA r r o y ot o n g u e
o f the Mancos S h a l e( M a s s i n g i l l ,
The N
IM S p r i n g st o n g u e
a r e a .E r o s i o n
opmentof
1979).
is poorlyexposed
of t h es h a l eg e n e r a l l y
i n t h es t u d y
r e s u l t s i n t h ed e v e l -
a low g r a s sc o v e r e df l a tb e t w e e nt h eP a g u a t ea n d
Dakotasandstones.
For d e s c r i p t i v ep u r p o s e s
a "composite"
41
s e c t i o n was c o n s t r u c t e d from i s o l a t e de x p o s u r e s
w i t h i n and a d j a c e n tt o
betweenthe
t h e s t u d ya r e a .
of t h e s h a l e
The l o w e rc o n t a c t
INM S p r i n g s and themainbody
o f t h e Dakota
Sandstone i s o n eo fi n t e r b e d d i n g
and was a r b i t r a r i l y p l a c e d
a t t h et o p
bed t h a t i s g r e a t e r t h a n
of t h el a s ts a n d s t o n e
f t ( 6 1 cm) t h i c k . .
PaguateSandstone
The c o n t a c tb e t w e e nt h e
i s a l s og r a d a t i o n a l .
change i s , however,the
r e s u l t o fa n
g r a i n s i z e n e a rt h et o po f
i n t e r b e d d e d nature.
atthepoint
INM Springsand
%e g r a d a t i o n a l
increase i nm e d i a n
t h e INM S p r i n g sa n dn o t
T h e r e f o r e , t h e u p p e rc o n t a c t
where t h er o c k
2
o f an
was p l a c e d
is t e x t u r a l l y a sandstone.
Cobban ( 1 9 7 7 a )h a sc o l l e c t e d
a Thatcherage(middle
C e n o m a n i a n )f a u n af r o mc o n c r e t i o n si nt h el o w e rp a r to f
the
N
IM S p r i n g s h a l e I. d e n t i f i e di n v e r t e b r a t e si n c l u d e :
Plicatula
arenaria,
p e c t e n i dand
s,
Ostrea" _b e l o i t i .
The INM S p r i n g sc o n s i s t sp r e d o m i n a n t l y
g r e y ( N 5 ) s h a l e w i t h m i n o ri n t e r c a l a t i o n s
b e h t o n i t e , a n dc a l c a r e o u ss i l t s t o n e .
i s p r i m a r i l yd a r k - b l a c k
of b l a c k (Nl) t o
of l i m e s t o n e ,
The lower 2 0 f t ( 6 m )
(Nl), n o d u l a r w e a t h e r i n g , v e r y
c a l c a r e o u s , s i l t y s h a l e s and i n t e r b e d d e d ,
0.3-1.0
ft
2 . 5 cm) t h i c k , v e r y c a l c a r e o u s , m o d e r a t e l y i n d u r a t e d
yellow ( 1 0 Y 4 / 2 ) ,
(
.75-
, light-
veryfine-grainedlithicarenitesand
s i l t s t o n e s .F e e d i n g
s o l e s of t h es a n d s t o n e
t r a c k s and t r a i l s a r e
and s i l t s t o n eb e d s .
common on t h e
The upper 6 0 f t
(18 m) of t h e INM S p r i n g s i s a m o d e r a t e l y c a l c a r e o u s ,
s p l i n t e r yw e a t h e r i n g ,s i l t y ,
medium-grey (N5) s h a l e ,
42
Near t h e b a s eo ft h e
INM S p r i n g s , a z o n eo fl a r g e ,
(I m ) - d i a m e t e r ,e l l i p s o i d a l ,l i m e s t o n en o d u l e s
c o n t i n u o u s bed t h a tf o r m s
3 f t
form a n e a r l y
a weak bench i n some a r e a s .
nodulesaremedium-brownish-grey
( 5 Mc 5 / 1 ) m i c r i t e
The
andcon-
tain megafossils.
B e n t o n i t e so c c u r
i n t h e INM S p r i n g sa ta p p r o x i m a t e l y
f t ( 3 m ) , 2 6 f t ( 8 m ) , and43ft.
the unit.
These b e n t o n i t e s a r e
cm) , and.25
ft
w e a t h e rg r e e n i s h -
o r a n g e( 5
Sp e c t i v e l y .
Y 6/6)
The b e n t o n i t e s
on a f r e s hs u r f a c et h e y
(N8).
Gypsum c r y s t a l s a r e
s h a l et o n g u e .
m) above t h e b a s eo f
0 1 f t (1 cm), 0.5 ft ( 1 5
cm) t h i c k r e
( 7.5
areverylight-grey
13
10
common i n t h e u p p e r p a r t
of t h e
The gypsum i s c o n f i n e dt op o s t - d e p o s i t i o n a l
f r a c t u r e s w i t h i n t h er o c kt h a tc u to b l i q u e l ya c r o s sb e d d i n g
surfaces.
The INM SpringsShaleaccumulated
mud e n v i r o n m e n td u r i n g
gression.
i n an o f f s h o r e ,s h e l f
t h e i n i t i a lC r e t a c e o u sm a r i n et r a n s -
The s h a l et o n g u e
i s g r a d a t i o n a li n t ol o w e rs h o r e -
f a c es a n d s t o n e so ft h eu n d e r l y i n gD a k o t aS a n d s t o n ea n di n t o
o f f s h o r eb a rd e p o s i t so ft h eo v e r l y i n gP a g u a t eS a n d s t o n e .
The presenceofanunabradedopenmarinefaunaandthehigh
s i l t c o n t e n to f
t h e s h a l e si n d i c a t et h a tn e a r s h o r e ,y e t
n o r m a l ,m a r i n ec o n d i t i o n sp r e v a i l e dd u r i n gd e p o s i t i o no ft h e
sediments
.
43
WhitewaterArroyoTongue
Owens ( 1 9 6 6 ) f i r s t a p p l i e d
t o n g u et o
t h e termWhitewaterArroyo
a s e c t i o n of d a r k s h a l e s t h a t s e p a r a t e t h e m a i n
bodyoftheDakotaSandstoneand'ItyowellsSandstonetongue
i n t h eZ u n ib a s i n .
Arroyotobe
He, however,consideredtheWhitewater
a member oftheDakotaSandstone.Landisand
a tongue o f
o t h e r s( 1 9 7 3 )l a t e ri n c l u d e dt h es h a l eu n i ta s
t h e Mancos as had Moench ( 1 9 6 3 ) , and Moench and S c h l e e
(1967).
is used i n t h i s r e p o r ti nt h e
The WhitewaterArroyo
sense o f L a n d i sa n do t h e r s( 1 9 7 3 ) .
This u s a g er e q u i r e s
a
c o r r e l a t i o no fa p p r o x i m a t e l y
40 m i ( 6 4 km) from the n e a r e s t
WhitewaterArroyooutcropin
t h e Narrows a r e a .
i s 9 2 f t (28 m ) t h i c k i n Sec. 1 7 ,
The WhitewaterArroyo
T.
3 N.,
R. 8 W. on t h e e a s t s i d e of t h e D Cross Mountain.
The s h a l e i n t e r v a l appears t o m a i n t a i n a u n i f o r mt h i c k n e s s
i n a n o r t h w a r dd i r e c t i o na tl e a s t
as f a r as Laguna, New
Mexico,whereLandisandothersreported
f t ( 2 7 m)
a thickness of 90
.
Northwest of D Cross Mountain,theWhitewaterArroyo
t h i n st o
a 60 f t (18 m ) t h i c k i n t h e v i c i n i t y o f G a l l u p ,
Mexico (Owens, 1 9 6 3 ) .E a s to f
Sandstone is n o t p r e s e n t
M a s s i n g i l l( 1 9 7 9 )
D Cross Mountain t h e Paguate
and theWhitewater
i s 187 f t ( 5 7 m ) t h i c k .
i n c l u d e s ,h o w e v e r ,t h el a t e r a le q u i v a l e n t
Arroyo o f
This s e c t i o n
o f t h e INM S p r i n g s
tongue of t h e Mancos ShaleandthePaguatetongueof
DakotaSandstone
New
a sd e s c r i b e di nt h e
the
D CKOSS a r e a ; t h u s , n o
44
more t h a n 1 0 0 f t ( 3 0 m) of t h e i n t e r v a l is WhitewaterArroyo
equivalents.
is s i m i l a r i n l i t h o l o g y and
?heWhitewaterArroyo
w e a t h e r i n gc h a r a c t e r i s t i c st o
In t,he
t h e INM S p r i n g sS h a l e .
D Cross Mountain a r e a , t h e i n c o m p e t e n t s h a l e s a r e t y p i c a l l y
poorlyexposed
and t h e c o n t a c tb e t w e e n
is c o n c e a l e db e n e a t hQ u a t e r n a r ya l l u -
andPaguateSandstone
vium.
t h e WhitewaterArroyo
However , i n t h e bed o ft h e
Hio S a l a d o ,a p p r o x i m a t e l y
1 m i ( 1 . 6 km) n o r t h o f t h e s t u d ya r e ai nS e c .
8 W.,
t h e c o n t a c tb e t w e e n
3
N., R.
t h e two u n i t s i s g r a d a t i o n a l .
contactbetweentheWhitewaterArroyo
TwowellsSandstone
5, T.
'Ihe
and t h e o v e r l y i n g
is a l s og r a d a t i o n a l ,
and is t h e r e s u l t o f
a n increase i n s i l t and s a n dc o n t e n ti nt h eu p p e rp a r t
of
t h e s h a l eu n i t .
F o s s i l sa r er a r e
i n t h e WhitewaterArroyo.Occasionally,
unabradedspecimensofanExogyraandInoceramusspeciesoccur
asfloat
i n t h eu p p e rp a r to f
b l a g ec o l l e c t e d
the section.
A f o s s i l assem-
o t h e r s (1973) i n d i c a t e s a
byLandisand
C e n o m a n i a na g ef o rt h es h a l es t r a t a .
The WhitewaterArroyo
c a r e o u s ,d a r k - g r e y
( 5 Y 7/2).
i s dominantly a s i l t y , v e r y c a l -
(N4) s h a l et h a tw e a t h e r sy e l l o w i s h - g r e y
S a n d yz o n e so c c u rs p o r a d i c a l l yt h r o u g h o u t
the
u n i t and s m a l l , 0 . 2 f t ( 6 cm)-diameter, e q u a n t , m i c r i t e
n o d u l e sa r ea b u n d a n ti n
S e v e r a lw h i t e
section.
t h e upper 1 0 f t ( 3
m) o f t h e u n i t .
(N9) b e n t o n i t e so c c u rw i t h i n
The s t r a t i g r a p h i c a l l yl o w e s t
( 1 5 cm) t h i c k , a n do c c u r sa p p r o x i m a t e l y
the shale
of these i s 0.5 f t
35 f t (11 m ) above
45
t h et o po ft h eP a g u a t eS a n d s t o n et o n g u e .
( 1 9 8 0 )b e l i e v et h i sb e n t o n i t eb e d
"x"
bentonite
"
...which
may b ee q u i v a l e n t
"
a t 92.1 m.y."
byObradovich
The s e c o n db e n t o n i t eo c c u r s
(1975).
to the
l i e s w i t h i n t h e Acanthoceras 'amphi-
bolum Zone and h a sb e e nd a t e d
and
Cobban
Hook and o t h e r s
a few f e e t
is
belowtheWhitewterArroyo-Twowellscontact.Thisbed
o n l y 3 i n . ( 7 . 6 cm) t h i c k .
?he W h i t e w a t e rA r r o y og r a d e sa b o v ea n db e l o wi n t oo f f s h o r eb a rs a n d s t o n e sa n dr e p r e s e n t ss e d i m e n t sd e p o s i t e d
The p r e s e n c eo f
below wave b a s e .
a s p a r s e ,u n a b r a d e d ,o p e n
marine f a u n a and t h e a b s e n c e -.6f a p p r e c i a b l e q u a n t i t i e s o f
s i l t andsand
i n t h e& a l es u g g e s td e p o s i t i o n
i n a no f f s h o r e
openmarineshelf-mudenvironment.
Rio
-
S a l aTd oo n e
The RioSaladoShaletongueof
name a p p l i e d by S. Hook and W.
t h e Mancos S h a l e was t h e
Cobban ( o r a l commun., 1 9 7 9 )
sequence t h a t s e p a r a t e s t h e
t o a t h i c k ,b l a c ks h a l e
and Tres Hermanos s a n d s t o n e s i n the P u e r t e c i t ua r e a .
s t r a t o t y p e ,a l o n gt h ec o u r s e
(1979)measured
as t h e o u t c r o p
The
and is 229 f t (711 m) t h i c k on
D Cross Mountain.
p r o b a b l yc o r r e l a t i v ew i t ht h eu p p e r1 7 0 - 2 0 0
M a s s i n g i l l ' sA l a m i t o
A t the
a u n i f o r mt h i c k n e s se a s t w a r da sf a r
can b et r a c e d
t h e eastern s l o p eo f
.
of t h e Rio S a l a d o ,M a s s i n g i l l
238 f t ( 7 3 m ) of Rio S a l a d os t r a t a .
s h a l et o n g u em a i n t a i n s
ow ells
The Rio Salado is
f t (52-cil m) o f
Well tongue of t h e Mancos S h a l e .
46
Rio S a l a d o is e s t a b l i s h e d a s l a t e
The a g eo ft h e
m a n i a nt oe a r l yT u r o n i a nb a s e d
S c i p o n o c e r a sg r a c i l e ,
on t h e c o n t a i n e d f o s s i l s .
a s t a n d a r d zoneammoniteof
WesternInteriorCretaceous(CobbanandReeside,
, occurs
Cobban and S c o t t , 1 9 7 2 )
Ceno-
the
1 9 5 2 ; and
a few f e e t abovethelower
This ammonitezonemarkstheCenomanian-
RioSaladocontact.
Rio S a l a d o is o fe a r l yt o
Turonianboundary.?heupper
a s i n d i c a t e db yt h ep r e s e n c eo f
m i d d l e Turonianage
depressus ( P l a t e 8 ) .
Mammites
A change from c a l c a r e o u ss h a l et o
non-
Rio Salado i s c o n s i d e r e db y
c a l c a r e o u ss h a l e sw i t h i nt h e
In the
many w o r k e r st om a r kt h eC a r l i l e - G r e e n h o r nb o u n d a r y .
D Cross M o u n t a i na r e a ,t h i sb o u n d a r yo c c u r sa p p r o x i m a t e l y
f t ( 2 1 m ) below t h e RioSalado-Tres
70
Hermanos c o n t a c t .
Exposures o f t h e s h a l e u n i t a r e e x t r e m e l y p o o r d u e t o
c a l v i n g of h u g eb l o c k so f
Rio S a l a d os l o p e .
i t i s a dark-grey
Tres Hermanos s a n d s t o n eo n t o
the
can befound,
Where e x p o s u r e so ft h er o c k
( N 3 ) , n o n c a l c a r e o u s t o m o d e r a t e l yc a l -
c a r e o u s ,s p l i n t e r yw e a t h e r i n gs i l t ys h a l e .
l h i n , light-brownish-grey
throughout t h e s h a l e u n i t .
cropoutat
( 5 YR 4/1) c a l c a r e n i t e so c c u r
' k i c k e rz o n e s
of c a l c a r e n i t e s
3 3 f t ( 1 0 m) and 80 f t ( 2 4 m ) above t h e
Twowells-RioSaladocontact.
The c a l c a r e n i t e sa r ep l a t y
weathering,bioturbated,silty,thinlylaminated
lineated
, andform
p o o r l yd e v e l o p e db e n c h e si nt h eo t h e r w i s e
s m o o t hs l o p e .F o s s i lh a s h
beds.
, current-
i s common i n t h e c a l c a r e n i t e
The most common f o s s i lc o n s t i t u e n t sa r eM y t i l o i d e s
47
Plate 8 .
Specimen of Mammites d e p r e s s u s - - t h i ss p e c i m e n
was
c o l l e c t e d from t h e c e n t e r of a l a r g ec o n c r e t i o n 6 0
f t ( 1 8 m ) b l o w t h e Rio Salado-Tres Hermanos
contact.
m y t i l o i d e s ;s h a r kt e e t h
and o t h e r b i o c l a s t s
are a l s o
recorded.
L i m e s t o n ec o n c r e t i o n so c c u ri n
z o n sw i t h i nt h e
shale s e c t i o n .
o fl i g h t - g r e y
(N7) toolivegrey
n o d u l e st h a t
two s t r a t i g r a p h i c h o r i -
The l o w e ru n i t
i s composed
micrite
( 5 Y 5 / 2 ) ,m a s s i v e ,
are e l o n g a t ea n dp a r a l l e lt ob e d d i n g .T h i s
zone i s w i t h i n 10 f t ( 3 m ) of t h e Twowells-RioSaladocont a c t .F o s s i l sa r ev e r ya b u n d a n ti nt h ec o n c r e t i o n a r yz o n e
and i n c l u d e :P y c n o d o n t en e w b e r r y i , u' n i d e n t i f i e de c h i n o i d s ,
The upperconcre-
and t h e a m m o n i t eS c i p o n o c e r a sg r a c i l e .
t i o n a r y zone is 2-3 f t (30-61 c m ) t h i c k and o c c u r sa p p r o x i m a t e l y 6 0 f t (18 m ) belo'w t h e Tres Hermanos Sandstone.
c o n c r e t i o n sa r ey e l l o w i s h - b r o w n
(10 YR 5/2)
, as
much a s 2 f t
( . 7 m ) i nd i a m e t e r
, septarian-like,
(21-30 m ) a p a r t .
The n u c l e i o € t h ec o n c r e t i o n so f t e nc o n -
s i s t of t h el a r g e
ammonite Mammites d e p r e s s u s .
b e a r i n gc o n c r e t i o n s
andspaced
70-100 f t
The f o s s i l -
are .of p a r t i c u l a r i n t e r e s t i n t h a t
t h e c o n c r e t i o n s a r e c o n f i n e dt o
The
(1)
a n a r r o ws t r a t i g r a p h i cz o n e
and ( 2 ) t h eo y s t e r sa r ea t t a c h e di ng r o w t hp o s i t i o nt ot h e
ammonite c a s t .
S. Hook ( o r a l commun.
similar o c c u r r e n c e s o f o y s t e r s a t t a c h e d
and lower
,
1980) h a so b s e r v e d
on b o t h t h e u p p e r
surfaces o f casts o f M. d e p r e s s u s i n o t h e r a r e a s .
The p o s i t i o n o f t h e
s h o r e f a c es a n d s t o n e so ft h e
Rio S a l a d os h a l e sb e t w e e n
paralic
Atarque Member o ft h eT r e s
Hermanos Sandstoneand'IkrowellsSandstone,andthepresence
o f a l a r g e l yu n a b r a d e d ,o p e nm a r i n ef a u n as u g g e s tt h a tt h e
49
RioSalado
was d e p o s i t e db e l o w
wave b a s e a s o f f s h o r e , m a r i n e
a t r a n s g r e s s i v e - r e g r e s s i v es e q u e n c e .
s h e l f - m u d sd u r i n g
The S c i p o n o c e r a s g r a c i l e - b e a r i n g l i m e s t o n e n o d u l e s
may
have accumulated seaward o f t h e o f f s h o r e m a r i n e mud f a c i e s
indeeper,clear
g r e s s i o ni nt h e
waters a n dc o u l dr e p r e s e n t
maximum t r a n s -
Seaward p r o g r e s s i o n from s a n d st o
area.
i s a well known model f o r e p e i r i c
c l a s t i c muds t oc a r b o n a t e s
sea deposits (Shaw, 1964).
C a l c a r e n i t e s , composed of f i n e s a n d s i z e c a r b o n a t e b i o -
c l a s t s , may e i t h e rr e p r e s e n ts e d i m e n t st h a tw e r ea c c u m u l a t e d
t h r o u g hr e w o r k i n go ft h em a r i n e
muds d u r i n gs t o r me v e n t s ,
or
t h a t were t r a n s p o r t e d offshore b y s t o r m - r e l a t e d c u r r e n t s .
?he o f f s h o r e movement o fs a n ds i z em a t e r i a lb ys t o r m - g e n e r a t e d
c u r r e n t s is well known from t h e Recent(ilayes,
1967).
Ihe p r e s e n c e of o y s t e r s h e l l s , a t t a c h e d i n g r o w t h
p o s i t i o no na m m o n i t e
c a s t s , s u g g e s t sa ne r o s i o n a ls u r f a c e
e x i s t s i n t h e s t r a t a t h a t is n o t l i t h o l o g i c a l l y a p p a r e n t .
This assumption i s based on t h e f a c t t h a i t h e o y s t e r s o c c u r
attached t o ammonite casts and n o t t o o r i g i n a l
material.
The f o l l o w i n gh i s t o r y
is s u g g e s t e d :
skeletal
(1) d e p o s i -
t i o n of ammonite s h e l l s , ( 2 ) b u r i a l and i n t e r n a l f i l l i n g o f
t h e ammonite s h e l l s , ( 3 ) l i t h i f i c a t i o n of t h e m o l d - f i l l i n g
s e d i m e n t s , ( 4 ) d i s s o l u t i o no ft h eo r i g i n a l
material, ( 5 ) e r o s i o n andaccumulationof
i n a s i n g l eh o r i z o n ,a n d
ammonite s k e l e t a l
the f o s s i l casts
( 6 ) attachmentandgrowthofoys-
t e r s on t h e casts.
R e g i o n a l l y , t h e p r e s e n c e of a ne r o s i o n a l
c o n g l o m e r a t ew i t h i n
t h e same t i m e - s t r a t i g r a p h i c i n t e r v a l
50
s u p p o r t st h ep r e s e n c eo fa nu n c o n f o r m i t yw i t h i nt h es t r a t a
(S.
Hook, o r a l commun.,
erosionalvacuities
may e x i s t i n t h e Mancos s h a l e u n i t s t h a t
c a n n o t be i d e n t i f i e d w i t h o u t
D Cross
-
O t h e rm i n o rh i a t u s e sa n d
1980).
detailed study.
Tongue
The D Cross tongue was d e f i n e d b y
astheshalethatcropsout
Mountain i n Sec. 30, T.
Dane and o t h e r s ( 1 9 5 7 )
on t h e e a s t e r n f l a n k o f
3 N.,
R.
8 W. betweenthe"Gallego"
(upper G a l l u p ) and a "lowerGallupsandstone"
Sandstone).
A t t h es t r a t o t y p et h e
(53 m ) t h i c k .
Fast o ft h e
f t (37 m)
f t (88 m) n e a rR i l e y ,
New Mexico,
i s n o tp r e s e n t .
J o r n a d a d e l Muerto a r e a , t h e
West and n o r t ho f
Shaletongue
s t o n e :t h e
D Cross tongue is 173 f t
D C r o s sS h a l eo f1 2 1
where t h e" G a l l e g o "s a n d s t o n e
thick.
(Tres Hermanos
D Cross area, M a s s i n g i l l( 1 9 7 9 )
r e p o r t e dt h i c k n e s s e so ft h e
n e a rP u e r t e c i t o ,a n d2 9 0
D Cross
In the
D Cross i s 363 f t (111 m )
D Cross M o u n t a i n ,t h e
D Cross
i s s p l i t i n t o two u n i t s b ya ni n t e r v e n i n gs a n d "E" s a n d s t o n e of Molenaar(1973
P i k e ( 1 9 4 7 ) , i n a r e g i o n a ls t u d y
correlatedthe,
and 1 9 7 4 ) .
of t h eC r e t a c e o u s ,
a s of t h e n unnamed, D Cross t o n g u ew i t ht h e
Pescadotongueofthe
Mancos S h a l ei nt h eZ u n ib a s i n .
At
t h e time t h e D C r o s sS h a l e
was f o r m a l l y d e f i n e d ,
o t h e r s( 1 9 5 7 )b e l i e v e dt h e
D Cross was a s t r a t i g r a p h i c a l l y
Dane and
h i g h e rs h a l et o n g u et h a nt h eP e s c a d o M
. o l e n a a r( 1 9 7 4 )l a t e r
partiallysubstantiated
Pike's originalcorrelationby
51
l e a s t t h el o w e rh a l fo f
d e m o n s t r a t i n gt h a ta t
D C r o s sS h a l e
is e q u i v a l e n tt ot h eP e s c a d ot o n g u e .
The D Cross S h a l e is l a t e m r o n i a n t o e a r l y C o n i a c i a n
i na g e
(S. Hook, o r a l commun.,
s a n d i e rz o n e si n
Hook b e l i e v e st h a t
1979).
are time
t h e lower p a r t o f t h e u n i t
Lopez Member o ft h e
e q u i v a l e n tt ot h eJ u a n a
( C a r l i l e ShaleoftheRatonand
Dane and o t h e r s ( 1 9 6 6 ) i nt h e
Mancos S h a l e
Denver b a s i n s ) as d e f i n e d b y
San JuanBasin.
The D Cross tongue i s t h e h i g h e s t p r o m i n e n t s l o p e f o r m i n gu n i ti nt h e
The rock i s a
D CrossMountainarea.
medium-grey ( N 3 t o 5 Y 5 / 2 ) , c h u n k y w e a t h e r i n g , s l i g h t l y t o
noncalcareous
, moderate-olive grey
siltyshalecontaining
, bioturbated,
( 5 Y 4/1)
n u m e r o u sf o s s i l - b e a r i n gc o n c r e t i o n
z o n e s .I d e n t i f i a b l ef o s s i l sc o l l e c t e d
from t h el o w e rp a r t
o ft h eu n i it n c l u d e P
: r i o n o c y c l u sw y o m i n g e n s i s P
, rionoc y c l u sn o v i m e x i c a n u s ,C o i l o p o c e r a si n f l a t u m ,a n d
Lopha
bellaplicata.
The m i d d l e p o r t i o n
moderately calcareous
of t h e u n i t i s g e n e r a l l y v e r y s i l t y ,
, and contains abundant oyster hash
,
The
P r i o n o c y c l u sn o v i m e x i c a n u s ,a n dv a r i o u sm i c r o f o s s i l s .
upper 4 0 f t ( 1 2 m) of D' C r o s ss h a l e
is s l i g h t l y c a l c a r e o u s
and c o n t a i n s t h e f o l l o w i n gf o s s i l s :
Lopha s a n n i o n i s I, n o -
ceramus perplexus, Prionocyclus novimexicanus,
P.
quadratus,
and B a c u l i t e sy o k o y a m i .
C o n c r e t i o n a r yz o n e s
are common i n t h e
D Cross s h a l e ;
o c c u r r i n g a t 1 f t (30 cm), 9 f t . (3 m), 2 2 f t ( 7 m), 134 f t
(41 m )
, and
143 f t (44 m ) a b o v et h ef o r m a t i o n
base.
The
52
, s o l i d , s m a l l , subequant ,
m i c r i t en o d u l e st ol a r g e ,
3 f t (1 m)-diameter ,
c o n c r e t i o n s v a r y from i s o l a t e d
g r e y (N5)
s u b e q u a n tt oe l o n g a t e ,y e l l o w i s h - g r e y
(5 Y 7/2), septarian-
l i k e c o n c r e t i o n st h a tf o r mn e a r - c o n t i n u o u s
beds.
Fossil
the concretions i n the
a m m o n i t e so f t e nf o r mt h en u c l e io f
lowertwoconcretionzones.
The l o w e r c o n t a c t o f t h e
D Cross s h a l e w i t h t h e Tres
Hermanos Sandstone is s h a r p and f l a t or, l o c a l l y u n d u l a t o r y .
The upper c o n t a c tw i t ht h eG a l l u pS a n d s t o n e
sandstoneand
is g r a d a t i o n a l ;
s h a l e beds a r ei n t e r b e d d e do v e r
g r a p h i ci n t e r v a lo f
was placed a t t h e b a s e
greater than 1 f t
m)
5-6 f t (1.5-1.8
The u p p e rc o n t a c t
was
o f thefirstsandstonethat
( 30 c m )
thick.
The D C r o s ss h a l e sa c c u m u l a t e di n
mud environmentduring
.
a strati-
a n e a r s h o r em a r i n e
a r e g i o n a lt r a n s g r e s s i v e - r e g r e s s i v e
sequence as d o c u m e n t e d b y t h e s h a l e u n i t c o n t a i n i n g a n o p e n
m a r i n ef a u n aa n dg r a d i n qi n t oo v e r l y i n gm a r i n es h o r e f a c e
sandstones.
The s i l t yc h a r a c t e ro f
abraded s h e l lh a s h ,
t h e s h a l e ,p r e s e n c eo f
and a b u n d a n tf o s s i l ss u g g e s ts h a l l o w
. w a t e rd e p t h sa n dd e p o s i t i o n
t y p i c a l" c l e a n "o f f s h o r e
i n a t r a n s i t i o n a lz o n eb e t w e e n
muds andlowershoreface
environments.
Tres HermanosSandstone
Thename
TKeS Hennanos was f i r s t usedby
Herrick ( 1 9 0 0 )
f o rt h eC r e t a c e o u sa g es t r a t at h a tc r o po u ta l o n gt h ec o u r s e
o f t h e Rio S a l a d oi nw e s t - c e n t r a l
New Mexico.
Herrick's
53
a type l o c a l i t y f o r t h e f o r -
f a i l u r et oa d e q u a t e l yd e s i g n a t e
mation h a s l e dt oc o n s i d e r a b l ec o n f u s i o n
a s t o h i si n t e n d e du s a g e .
bothPike
among l a t e rw o r k e r s
In t h e D CrossMountainarea,
( 1 9 4 7 ) andGivens(1957)usedthe
Tres Hermanos
t e r m i n o l o g y for what is now c o n s i d e r e dt h e
TMowells
Sands tone.
S.
Hook and W.
Cobban ( o r a l commun.,
l y r e d e f i n e da n de l e v a t e d
1 9 7 9 )h a v er e c e n t -
t h e Tres Hermanos t of o r m a t i o n a l
s t a t u s and d e f i n e dt h r e ef o r m a lm e m b e r s ;t h e s ea r e ,i n
(1) a l o w e rs a n d s t o n e
a s c e n d i n go r d e r :
-
t h eA t a r q u e
Mem-
-
b e r , ( 2 ) a m i d d l ec o a l - b e a r i n gs a n d s t o n ea n ds h a l es e c t i o n
t h e Carthage Member, and ( 3 ) a nu p p e rc o n c r e t i o n a r ys a n d -
stone
-
t h eF i t e
Ranch Member.
The combinedthickness
of
t h e t h r e e members is 2 3 0 f t ( 7 0 m ) i n Sec. 1 9 , T. 3 N.,
W.
o nt h es o u t h e a s t e r ns l o p eo f
The f o r m a t i o n , a s
R.
D Cross Mountain(Figure
8
8).
a package, i s p r o b a b l yc o r r e l a t i v ew i t h
t h e Atarque member oftheGallupSandstoneand
F sandstone
( o r e q u i v a l e n t )o fM o l e n a a r( 1 9 7 3 )i nt h eZ u n ib a s i no f
w e s t e r n New Mexico.
R e g i o n a l l y , t h e T r e s HermanosSandstone
northeast.
"he t h i n n i n go c c u r si nt h eC a r t h a g e
i s d u et ot h es t r a t i g r a p h i c
n o r t h e a s t w a r dd i r e c t i o n .
a wedging-outoftheCarthage
r i s e oftheAtarque
The r i s e of theAtarque
New Mexico.
2 4 4 f t ( 7 4 m) t h i c k .E a s t
the
Member, and
Member i n a
results i n
Member along a l i n e e x t e n d i n g
n o r t h w e s t - s o u t h e a s tf r o mt h ev i c i n i t yo fG r a n t s ,
t oC a r r i z o z o ,
thinsto
A t C a r t h a g et h eT r e s
New Mexico,
Hermanos i s
of G r a n t sa no f f s h o r em a r i n e
54
Depositional
Environment
D Cross
Fite Ranch
Mb.
,
... .
k-
.
.
cong
.
Shoreface
sand
very carbonaceous
- structureless, carbonaceous,
laterally continuous
Fluvial coastal
plain and marsh
,
lenticular fining upward
\
Carthage
sandstones
Mb.
carbonaceous shales
oyster biolithites
coarsening upward
cycles
cross-stratified
-
- "_
Lagoonal
Regressive barrier
and shoreface sand
complex
bioturbated
Rio Salado
fzt
interbedded contact
Off-shore mud
mud} sand
Figure 8 . Stratigraphic section of t h e Tres Hermanos
Sandstone. The Tres Hermanos accumulated during
a regressive-transgressive episode.
55
s a n d s t o n e ,t h eS e m i l l aS a n d s t o n eo f
Dane and o t h e r s ( 1 9 6 8 )
,
i s of Tres Hermanos a g e( M o l e n a a r ,1 9 7 3 ) .
The TKeS Hermanos is a s s i g n e d a m i d d l em r o n i a na g e
based on the presence of Collignoniceras
a t the base
0.f
"
woollgari woollgari
the formation and Scaphites ferronensis,
-S.
w h i t f i e l d i ,P r i o n o c y c l u sn o v a m e x i c a n u s ,a n dC o i l o p o c e r a s
i n f l a t u m w i t h i n a few f e e t a b o v et h e
S h a l ec o n t a c t .
Tres Hermanos-D Cross
The a g eo ft h eb a s eo ft h e
Tres Hermanos
a line
becomesyoungerfromsoutheasttonorthwestalong
fromTruth
or Consequences , New Mexico , t o Cuba , New Mexico.
The t o p o f t h e f o r m a t i o n a p p e a r s t o b e
"time-flat'' between
t h e same a r e a s a s d e n o t e d b y t h e p r e s e n c e o f P r i o n o c y c l u s
maconbi a t b o t h l o c a l i t i e s
commun.
, 1979).
( S . Hook and W.
This s u g g e s t se i t h e r
m a r i n et r a n s g r e s s i o n
Cobban, o r a l
a v e r yr a p i dr a t eo f
or a n o r t h w e s t - s t r i k i n gs h o r e l i n e .
R a p i dm a r i n et r a n s g r e s s i o n sa p p e a rt oh a v eb e e n
d u r i n g t h e C r e t a c e o u si nt h es o u t h e r n
n o r t h w e s t - t r e n d i n gp a l e o s h o r e l i n ef i t s
g e o g r a p h ya sd i s c u s s e db y
common
Rocky Mountains,and
well i n t ot h ep a l e o -
Hook and o t h e r s ( 1 9 8 0 ) .
Tres Hermanos i s g r a d a t i o n a l l y i n t e r -
The b a s eo ft h e
bedded w i t h theunderlyingRioSalad;Shaletongueofthe
Mancos S h a l e .
Along t h eb a s eo ft h es c a r p - f o r m i n go u t c r o p ,
bioturbatedthin
t o verythinbedsofhorizontally
n a t e d ,s i l t ys a n d s t o n e
d a r ko r g a n i c - r i c h
v a lo fa p p r o x i m a t e l y
lami-
and s i l t s t o n e a r e i n t e r b e d d e d w i t h
Mancos s h a l e s o v e r
5 f t (1.5 m ) .
a s t r a t i g r a p h i c interThe c o n t a c tb e t w e e nt h e
a
56
Tres Hermanosand
t h eo v e r l y i n g
D Cross S h a l e i s s h a r pa n d
flat.
Atarque Member
The Atarque Member forms t h e b o l d c l i f f t h a t
n e n t on t h e e a s t s i d e of D Cross Mountain.
is promi-
This s a n d s t o n e
u n i t i s composed o f 53 f t ( 2 5 m ) o fi n t e r c a l a t e ds a n d s t o n e
and t h i ns h a l eb e d s( P l a t e
9).
The f r e q u e n c ya n dt h i c k n e s s
of ' t h e u n i t .
of t h e s h a l e . b e d s i n c r e a s e s t o w a r d s t h e t o p
The Atarque is c h a r a c t e r i z e d b y
medium t o t h i c k b e d s o f
hummocky l a m i n a t e d , b i o t u r b a t e d
and c r o s s - s t r a t i f i e d , f i n e -
t o medium-grainedsubarkoses.
Numerous l a r g e , u p t o 3 ' f t
developed,spherical
t h eb a s e
(1 m ) d i a m e t e r ,p o o r l y
, calcareousconcretionsarepresentat
of theAtarque
Member.
S i m ' i l a rc o n c r e t i o n s
were
noted by H e r r i c k ( 1 9 0 0 ) i n h i s o r i g i n a l d e f i n i t i o n o f t h e
Tres Hermanos.
The c o n c r e t i o n sa r eo n l ys l i g h t l y
r e s i s t a n tt ow e a t h e r i n gt h a nt h es u r r o u n d i n gr o c k
a sv a g u e
more
andappear
brown zones a t t h e o u t c r o p .
The Atarque, i n g e n e r a l , e x h i b i t s c y c l i c s e d i m e n t a t i o n .
A t y p i c a l c o a r s e n i n g upward c y c l e c o n s i s t s o f
dark,structurelessshale
or s i l t s t o n e
at
(11 t h i n ,
t h eb a s eo ft h e
sequence, ( 2 ) a m i d d l eu n i to fs t r u c t u r e l e s s ,h o r i z o n t a l l y
l a m i n a t e d o r l o wa n g l ec r o s s - l a m i n a t e d ,f i n e - g r a i n e ds a n d s t o n ec o n t a i n i n g
Ophiomorphaburrows
( P l a t e 1 0 ) .and ( 3 ) an
u p p e rs e q u e n c eo fp l a n a rc r o s s - s t r a t i f i e ds a n d s t o n e .
wedge-planar s e t s a v e r a g e less t h a n ' 1 f t ( 3 0 c m ) i n
fie
..
51
Plate 9 .
C l i f f - f o r m i n go u t c r o p
o f theAtarque
Member of
t h e Tres Hermanos Sandstone--theAtarque
is a
coarsening-upwardsequence
of c r o s s - s t r a t i f i e d
29,
s u b a r k o s e s . photograph was t a k e ni nS e c t i o n
T. 3 N., R. 0 W.
58
P l a t e 10.
Ophiomorpha burrows--these trace f o s s i l , which
a r e c h a r a c t e r i s t i c of s h o r e f a c ee n v i r o n m e n t s ,a r e
"res Hermanos
common i nt h e Atarque Member o ft h e
Sandstone.
59
are i n c l i n e d t o the
t h i c k n e s s ,a n df o r e s e ts t r a t i f i c a t i o n s
s o u t h e a s t( A p p e n d i x
B)
.
The u p p e rp a r to ft h eA t a r q u e
is composed o f r i p p l e d ,
, b i o t u r b a t e d , thin-bedded , f i n e - g r a i n e d
sandstone,dark-colored , f o s s i l i f e r o u s , b i o t u r b a t e d s h a l e ,
microcross-laminated
and r a r e b i o t u r b a t e d b i o m i c r i t e s a n d r i p p l e d b i o s p a r i t e s .
-
Cymbophora sp., Cardium paraeculum', Laternula sp., Gyrodes
d e s p r e s u s ,a n do y s t e r sa r e
Member.
common a t t h e t o p o f t h e A t a r q u e
The s k e l e t a l material i s g e n e r a l l yu n a b r a d e d .
The
i n t o t h e o v e r l y i n gC a r t h a g e
A t a r q u eg r a d e sv e r t i c a l l y
Member.
C a r t h a g e Member
The Carthage Member i s 123 f t ( 3 8 m ) t h i c k and c o n s i s t s
o f numerous3-5
f t (0.9-1.5
yellow t o o l i v e g r e e n ( 5
m)-thick,
lenticular
,
light-
Y 8/3 t o 56 Y 3 / 2 ) , s i l t y , p o o r l y
sorted , troughandtabularcross-stratified,
f i n e - g r a i n e df e l d s p a t h i cl i t h a r e n i t e s .
and r i p p l e d
These s a n d s t o n e s
a basalclay-
h a v es h a r p ,u n d u l a t o r yc u tb a s e sa n dc o n t a i n
c l a s t c o n g o m e r a t e .B i o t u r b a t i o nf e a t u r e s
The sandstonepac'kages
,
are r a r e .
become cleanerandmore
persis-
t e n tt o w a r dt h et o po ft h e
member and t h e shale i n t e r v a l s
i n c r e a s ei nb o t h ,t h i c k n e s s
and i n o r g a n i cc o n t e n t .
shaleintervals
are d a r k , o r g a n i c - r i c h , s i l t y ,
small, 0 . 1 f t (3cm)-diameter
The
a n dc o n t a i n
, s u b e q u a n t ,d a r k - r e d
( 5 R 3/4)
i r o n s t o n ec o n c r e t i o n s .
S e v e r a lt h i n ,d a r k - r e d d i s h - b r o w n
the h i g h e rp a r to f
( 1 0 R 3/4)zonesin
t h e C a r t h a g ec o n t a i na p p r o x i m a t e l y5 0 %
60
No c o a l i s , however , developed i n t h e
carbonaceous matter.
Carthage Member.
U n u s u a lr o c kt y p e sa s s o c i a t e dw i t ht h e
are a t h i n , l a t e r a l l y p e r s i s t e n t ,
c a r b o n a c e o u si n t e r v a l
(1 m ) - t h i c k ,
structureless, grey
3 ft
(N7) , s i l t y s u b a r k o s e ,
w h i c hc o n t a i n sa b u n d a n td i s s e m i n a t e do r g a n i cf r a g m e n t sa n d
l e n t i c u l a rz o n eo fr e d
as t h e
( 5 R 4/6)
c l a y s t o n ec l i n k e r s
a
formed
r e s u l of
t
i n s i t u combustion.
"
The carbonaceousCarthage
Member i s o v e r l a i n b y t h e
F i t e Ranch Member.
The c o n t a c tb e t w e e nt h eF i t e
Member andCarthage
i s s h a r p and s l i g h t i y e r o s i o n a l .
F i t e Ranch
-
Ranch
Member
The F i t e Ranch i s 24 f t ( 7 m ) t h i c kt h r o u g h o u t
the study
t h e F i t e Ranch ( F sand of Molenaar,1973)
areaR
. egionally,
a v e r a g e s 5 f t ( 1 . 5 m ) i n t h i c k n e s s , b u t it is n o t p r e s e n t
Nutria monocline.
e v e r y w h e r e ,s u c ha si nt h e
of t h e s e c t i o n t h e r o c k
A t t h eb a s e
is a s t r u c t u r e l e s s ,
, y e l l o w i s h - g r e y( 5 Y 7 / 2 )s l i g h t l y
c a l c a r e o u s , b i o t u r b a t e d , m o d e r a t e l y - s o r t e d , medium f i n e s p h e r o i d a lw e a t h e r i n g
Dark o r g a n i c s t r e a k s a n dc o a fl r a g m e n t s
g r a i n e ds u b a r k o s e .
Tne
o c c u rl o c a l l yw i t h i nt h eb a s eo ft h es a n d s t o n eu n i t .
u p p e rp a r t
of t h e u n i t
cemented subarkose
i s a medium f i n e - g r a i n e d , c a l c i t e
.
Large, moderate-brown
( 5 YR 3 / 4 )c o n c r e t i o n st h a ta r e
a s much as 5 f t (1.5 m ) i n diameter.
Ranch Member.
w e a t h e ro u t
, are
common i n t h e
These c o n c r e t i o n s a r e v e r yc o n s p i c u o u sa n d
as h u g es p h e r i c a lb o u l d e r s .
Fite
61
E i g h tt h i n - s e c t i o n s ,
and a lime
o f s e v e ns a n d s t o n e s
Tres Hermanos were e x a m i n e dp e t r o g r a p h i c a l l y .
s t o n e ,f r o mt h e
A wide v a r i e t y o f rock types are represented i n t h e
Wes
Atarque Member g e n e r -
Hermanos s t r a t a .S a n d s t o n e sf r o mt h e
a l l y c o n t a i n less than 80% q u a r t z g r a i n s
and are s u b a r k o s e s .
The q u a r t z g r a i n s a r e m o s t l y s u b r o u n d e d , s i n g l e g r a i n s w i t h
are free o fi n c l u s i o n ,a l t h o u g h
u n d u l o s ee x t i n c t i o na n d
grainswithmicrolites,bubblesandbubbletrainsare
p r e s e n t .S p a r r y
c a l c i t e i s t h ec h i e fc e m e n t i n ga g e n t .
Feldspars a r e t h e s e c o n d m o s t a b u n d a n t m i n e r a l c o n s t i t -
uent.Potassium
and lesser
f e l d s p a r s , m o s t l yo r t h o c l a s e
amounts of microcline, a r e t h e d o m i n a n t f e l d s p a r t y p e s
r e c o r d e d ,c o m p r i s i n g
u p t o 11%of t h e g r a i n s i n
some samples.
Many of t h e g r a i n s are m i c r o p e r t h i t e a s e x h i b i t e d b y
the
%e
c h a r a c t e r i s t i ca l t e r a t i o np a t t e r no ft h eg r a i n s .
are g e n e r a l l y
f e l d s p a r s a r es u b a n g u l a rt os u b r o u n d e d ,a n d
smaller t h a nt h eq u a r t zg r a i n s .B o t hu n w e a t h e r e dg r a i n sa n d
grains that
h a v eu n d e r g o n ev a r y i n gd e g r e e s
of k a o l i n i z a t i o n
a n d / o rv a c u o l i z a t i o na r ep r e s e n t .S o d i cp l a g i o c l a s e sa r e
r a r e l yo b s e r v e da n da r ep o o r l yp r e s e r v e d .O t h e rc o n s t i t u entsthatoccurin
small q u a n t i t i e s , b u t w h i c h
a b u n d a n tl o c a l l y ,i n c l u d e
: muscovite
s k e l e t a l c a r b o n a t e material
, biotite,glauconite,
, opaque minerals
and o r g a n i c material) , c h e r t , s i l t s t o n e g r a i n s
skeletalmaterial,
A)
may be
( iron oxides
, phosphatic
a n da n i s o t r o p i ch e a v ym i n e r a l s( A p p e n d i x
62
S a n d s t o n e si nt h eC a r t h a g e
Member a r e v e r y c a l c a r e o u s ,
s i l t y ,c o n t a i nn og l a u c o n i t e ,h a v e
a h i g h e rp e r c e n t a g eo f
o r g a n i cd e b r i s ,m i c a ,a n dm u d s t o n ec l a s t st h a nt h eA t a r q u e
s a n d s t o n e s .S a n d s t o n e si nt h e
F i t e Ranch Member a r e miner-
a l o g i c a l l ys i m i l a rt ot h o s eo ft h eA t a r q u e .
organiccontent,
lhe h i g h
of a clay-
lack of glauconiteandpresence
a t t h e base o ft h e
c a s tc o n g l o m e r a t e
F i t e Ranch s a n d s t o n e i s
noteworthy.
The Tres Hermanos is composed o f a t h i c k s e c t i o n o f
m a r s h yc o a s t a lp l a i ns e d i m e n t s( C a r t h a g e
s a n d w i c h e db e t w e e nr e g r e s s i v e( A t a r q u e
Member) t h a t a r e
Member) and t r a n s -
g r e s s i v e ( F i t e Ranch Member) s a n d s t o n e s T
. h e s es t r a t a
accumulated duringone
p o s i t i o no ft h e
Mexico
of two m a j o r f l u c t u a t i o n s i n t h e
New
Upper C r e t a c e o u s s h o r e l i n e i n c e n t r a l
.
The Atarque Member r e p r e s e n ts e d i m e n t st h a ta c c u m u l a t e d
a s a near-shoresubmergedbar
or b a r r i e r i s l a n dc o m p l e x
d u r i n g a l a t e Greenhorn-early Carlile r e g r e s s i o n .
s a n d s t o n ee x h i b i t sv a r i a t i o n si nt e x t u r e
s t r u c t u r e st h a t
andsedimentary
are similar t o t h a t i n t e r p r e t e d b y
bar.
Molenaar
These c h a r a c t e r i s t i c s
( 1 9 7 3 )a s
a progradingsand
include:
( 1 ) c o a r s e n i n g - u p w a r dg r a i ns i z e ,
decrease i n b i o t u r b a t i o n ,
The
(2) vertical
( 3 ) p r e v a l e n c e of p a r a l l e l
o f t h eu n i t ,
l a m i n a t i o n s( l o w e rs h o r e f a c e )i nt h el o w e rp a r t
and ( 4 ) g r a d a t i o n from o f f s h o r e m a r i n e muds a t t h e b a s e i n t o
c o a l - b e a r i n gc o a s t a l
p l a i n s e d i m e n t s a t t h et o p .
t h r e e v e r t i c a l l y stacked bars e x i s t i n t h e
As many a s
D C r o s sa r e a .
63
Member, a s e r i e s o f t h i n ,
Near t h e t o p o f t h e A t a r q u e
imma-
ture , bioturbated and cross-stratified, oyster-bearing
s a n d s t o n e s , b i o m i c r i t e s , and i n t e r c a l a t e d d a r k - c o l o r e d
b i o t u r b a t e ds h a l e s
a r e i n t e r p r e t e da sl a g o o n a li no r i g i n .
L e n t i c u l a rs a n d s t o n e si nt h eC a r t h a g e
Member r e p r e s e n t
c h a n n e l - f i l ld e p o s i t st h a ta c c u m u l a t e di nc h a n n e l st h a tw e r e
c u t i n t or o o t - m o t t l e do r g a n i c - r i c h
a c c u m u l a t e di n
menton
a f l o o dp l a i n
s h a l e a n d" c o a l s "t h a t
and i n t e r d i s t r i b u t a r y e n v i r o n -
a f l u v i a l l y - c o n s t r u c t e dl o w e rc o a s t a lp l a i n .
Similar c h a n n e ls a n d s ,p e a t - b e a r i n gf l o o dp l a i n
and i n t e r -
d i s t r i b u t a r y d e p o s i t s are p r e s e n t l y a c c u m u l a t i n g
on t h e
(Gould and Morgan ,
M i s s i s s i p p iR i v e rd e l t ap l a i nc o m p l e x
1962) and a r e well known from therock-record(Erpenbeckand
Flores1
, 979).
The F i t e Ranch s a n d s t o n e r e p r e s e n t s
t i o n a le n v i r o n m e n ti nt h e
This
D CrossMountainquadrangle.
sandstone is a, moderately bioturbated
sequence.
a s i n g l ed e p o s i -
The u n i th a s
, fining-upward
a s l i g h t l ye r o s i o n a lb a s e
o v e r l a i nb ym a r i n es h a l e so ft h e
and i s
D C r o s st o n g u e .S i m i l a r
s a n ds e q u e n c e sa r ep r e s e n t l ya c c u m u l a t i n go nt h es o u t h e a s t
Texas Gulf C o a s t a s
a r e s u l t of a m a r i n e t r a n s g r e s s i o n
c a u s e db yl o c a ls u b s i d e n c ea n d
a deficiencyofsandentering
t h es h o r e l i n es y s t e m .
me
Member , its a b s e n c e i n
some areas , and its synchronousage
t h i n n e s so ft h e
F i t e Ranch
i n widespread o u t c r o p s i n d i c a t e t h a t t h e s a n d r e p r e s e n t s a n
o n l a ps a n d s t o n et h a t
was d e p o s i t e d on a r a p i d l y s u b s i d i n g
s a n d - s t a r v e dc o a s t l i n e .
64
MESAVERDE GROUP
The name "Mesaverde Group" was f i r s t a p p l i e db y
( 1 8 7 7 )t o
Holmes
a t h i c ks e q u e n c eo fC r e t a c e o u ss a n d s t o n e sa n d
i n Montezuma County,Colorado.
s h a l e st h a tc r o po u t
Since
Holmes' o r i g i n a l work theterm"Mesaverde"hasbeenused
i n c o n s i s t e n t l yt oc o n n o t a t ee i t h e rg r o u p
rank.
' B o f o r m a t i o n so ft h eM e s a v e r d e
s t u d y area.
or f o r m a t i o n a l
Group c r o po u ti nt h e
T h e s ea r e ,i na s c e n d i n go r d e r ,
SandstoneandtheCrevasse
t h e Gallup
Canyon Formation.
Gallup Sandstone
The name Gallego was f i r s t used byWinchester(1920)
f o r a t h i c k ,c l i f f - f o r m i n gs a n d s t o n et h a tc r o p so u ta l o n g
t h e Rio Salado and t h eA l a m o c i t a
Creek b e d s i n w e s t - c e n t r a l
New M e x i c o W
. i n c h e s t e r( 1 9 2 0 )o r i g i n a l l yc o n s i d e r e dt h e
G a l l e g ot o
be a p a r t o f t h e
L a t e r , P i k e ( 1 9 4 7 ) ,i n
now o b s o l e t e Miquel Formation.
a r e g i o n a ls t u d yo ft h eC r e t a c e o u s ' o f
N e w Mexico,includedtheGallego
MesaverdeFormation.
rankbyMolenaar
as t h e b a s a l
The Gallego was r a i s e dt of o r m a t i o n a l
( 1 9 7 4 ) who suggested t h a tt h es a n d s t o n e
c o r r e l a t i v ew i t ht h eu p p e rG a l l u ps a n d s t o n eo f
Basin.
member o ft h e
%e G a l l u pt e r m i n o l o g y
is
t h e San Juan
is now used t h r o u g h o u tt h e
Acoma b a s i n for W i n c h e s t e r ' sG a l l e g oS a n d s t o n e .
I nt h eR i l e y - P u e r t e c i t o
i n t o two u n i t s b y
area, t h e G a l l u p
an i n t e r v e n i n gt o n g u e
( M o l e n a a r 1, 9 7 4 ) M
. assingill
is d i v i d e d
o f t h e Mancos S h a l e
( 1 9 7 9 ) o p t e dt oa p p l yt h e
65
" G a l l e g ot e r m i n o l o g y "o n l yt o
t h e l o w e ro ft h e s e
s t o n e s ;i n c l u d i n gt h eu p p e ru n i t i n
Formation ( s i c )
two sand-
h i s undividedMesaverde
.
i s a s i n g l e , 80 f t ( 2 4
In t h e D C r o s sa r e at h eG a l l u p
m ) t h i c k ,s a n d s t o n et h a tf o r m st h es t r a t i g r a p h i c a l l yh i g h e s t
laterally persistent cliff on the east
face of D Cross Moun-
t a i n ( P l a t e 11). The u p p e rp a r to ft h e
Gallup i s b l e a c h e d
is v e r y d i s t i n c t i v e when viewedfrom
whiteand
a distance.
In
F o s s i l sa r en o ta b u n d a n ti nt h eG a l l u pS a n d s t o n e .
t h e D C r o s s area P r i o n o c y c l u sn o v i m e x i c a n u s ,B a c u l i t e s
perplexus, a n dL o p h as a n n i o n i so c c u ri n
yokoyami,Inoceramus
t h eu n d e r l y i n g
D C r o s ss h a l ew i t h i n
o ft h eG a l l u p .
1 0 f t ( 3 m ) of t h e b a s e
Lopha s a n n i o n i s is common i nt h eu p p e rf e w
f e e t o f t h e Gallup Sandstone and Inoceramus
o c c u rt h r o u g h o u t h eu n i t M
. assingill
sp.
fragments
( 1 9 7 9 ) h a sr e p o r t e d
-
P r i o n o c y c l u s sp. and B a c u l i t e s yokoyami ftom the base
G a l l u p i n t h eP u e r t e c i t oa r e a .
f o s s i la s s e m b l a g e ,t h eG a l l u p
Based on t h ec o n t a i n e d
i s l a t el U r o n i a ni na g e .
In t h e D CrossMountainquadrangle,theGallup
posedof
9).
o€ the
is com-
a coarsening-upwardsequenceofsubarkoses(Figure
A t t h e base o ft h eu n i tt h i n ,v e r yf i n e - g r a i n e ds a n d -
s t o n e s a r e i n t e r b e d d e dw i t hs h a l e so v e r
of 2-5 f t (0.6-1.5
m).
Sandstoneandoverlying
a verticaldistance
The c o n t a c tb e t w e e nt h eG a l l u p
Crevasse Canyon Formation is s h a r p
and i r r e g u l a r b u t p o o r l y e x p o s e d .
The g r e a t e s t p a r t o f t h e
G a l l u p is composed o f a l t e r -
n a t i n g beds o f f i n e - t o m e d i u m - g r a i n e d , m o d e r a t e l y s o r t e d
66
P l a t e 11.
C l i f f - f o r m i n go u t c r o p
o f GallupSandstone--the
u n i t i s a c o a r s e n i n g upward sandstonepackage
measuring 8 0 f t ( 2 4 m) t h i c k . The c o n t a c t w i t h
theunderlying
D Cross s h a l e i s g r a d a t i o n a l .
67
Depositional Environment
Crevasse
Canvon
I
coal
seam,
laterallv
ovster
biolithites
-root-mottled
abular cross-stratified
-
I
Lagoon and swamp
Upper Shoreface
Lower Shoreface
“horizontal laminations
and burrows
-bioturbated
I
Lower Shoreface
and
Transitional
-interbedded
Transitional zone
contact
Off-shore muds
3 Cross
Shale
mud
I
10 f t
sand
L
Oft
Figure 9 . Stratigraphic section of the Gallup
Sandstone. The Gallup sandstone represents
a coastal barrier bar deposit.
68
s u b a r k o s e st h a t
bioturbated
, or
a r e h o r i z o n t a l l yl a m i n a t e d
intenselybioturbated
and s p a r s e l y
and s t r u c t u r e l e s s .
A b r a d e dp e l e c y p o ds h e l lh a s ho c c u r sa l o n gb e d d i n gp l a n e s
throughout the u n i t , b u t
it i s more common a t t h e b a s e o f
t h e formation.
G r a i ns i z ei n c r e a s e sr a p i d l yn e a r
the topoftheunit
where t h e rock is a medium-grained,white(N8)
, mature,
well
s o r t e d ,t a b u l a rc r o s s - s t r a t i f i e ds a n d s t o n e( P l a t e1 2 ) .
is a p p r o x i m a t e l y 1 5
T a b u l a rc o s e t sc o m p r i s ea ni n t e r v a lt h a t
f t ( 5 m) t h i c k .
The c r o s s - l a m i n a e are h i g ha n g l e ,i n c l i n e d
u n i f o r m l yt ot h es o u t h e a s t( A p p e n d i x
t h a ta r e
B)
, a n do c c u ri n
sets
a s much a s 1 f t ( 3 0 cm) t h i c k .L a t e r a l l y ,s m a l l
s a n d - f i l l e dc h a n n e l so c c u r
a t thetopofthecliff-forming
unit.
A series of thin-bedded, dark-colored
s h a l e s and i n t e r c a l a t e d medium-bedded,
t u r e l e s s t oh o r i z o n t a l l yl a m i n a t e d ,a n d
s t r a t i f i e ds a n d s t o n e so c c u r
Gallup.
, bioturbated
bioturbated , strucripple cross-
i n t h eu p p e rf e wf e e to ft h e
The s a n d s t o n e sa r em o d e r a t e l ys o r t e d ,c a l c i t e
cementedsubarkoses.Locally,small
b i o h e r m so c c u ri nt h es h a l ei n t e r v a l s .
zones are dark-brown
( 5 YR 2/4)
a g a i n s tt h ew h i t eG a l l u ps a n d s t o n e s
are l o n g ,s l e n d e r ,b l a c k
, l e n t i c u l a ro y s t e r
The f o s s i l i f e r o u s
and s t a n d o u t c o n s p i c u o u s l y
(Plate 13).
?he o y s t e r s
( N l ) Ostera s o l e n i s c u s t h a t o c c u r
in growth position.
Long, 0.3 i n . ( 7 . 6 mm)-diameter, c i r c u l a r , b r a n c h i n g
root-tubes
are p r e s e n ti nt h eu p p e r
p a r t of t h e u n i t i n
many
69
P l a t e1 2 .C r o s s - s t r a t i f i e d ,
u p p e rs h o r e f a c ed e p o s i t sa t h e
t o p of theGallupSandstone.Photograph
was
t a k e na l o n gt h en o r t h
bank o f Alamocita Creek i n
S e c t i o n 30, T. 3 N., R. 8 W.
70
P l a t e 13.
o y s t e r bioherm i nt h e
upperGallupSandstone-t h e o y s t e r s are O s t e r as o l e n i s c u st h a to c c u ri n
g r o w t hp o s i t i o n .
Brown weathering of thebioherm
i s d i s t i n c t i v ea g a i n s tt h ew h i t eG a l l u ps t r a t a .
Photograph was t a k e ni nS e c t i o n
3 0 , T. 3 N., R. 8
W.
71
areas.
i n o u t c r o p sa l o n gt h e
The t u b e s a r eb e s te x p o s e d
n o r t h bank o f t h e Alamocita Creek d u es o u t h
of D Cross
Mountain.
E x a m i n a t i o no ft h eG a l l u ps a n d s t o n e si nf i v et h i n s e c t i o n s show t h er o c kt ob e
a s u b a r k o s eo rl i t h i ca r k o s e .
The d o m i n a n t m i n e r a l c o n s t i t u e n t
60-75% o f t h e rock.
The q u a r t zg r a i n sa r eu n i f o r m l y
r o u n d e d ,s i n g l ec r y s t a l s
and a r ef r e e
i s q u a r t zw h i c hc o m p r i s e s
sub-
with slightlyunduloseextinction
of i n c l u s i o n s F
. e l d s p a rc o m p r i s e sa p p r o x i -
The f e l d s p a r
m a t e l y 1 9 % byvolumeoftheframeworkgrains.
g r a i n sa r em o s t l yi n t e n s e l yw e a t h e r e do r t h o c l a s et h a ta r e
s m a l l e rt h a nq u a r t zg r a i n s .O n l y
a t r a c e o fp l a g i o c l a s ea n d
m i c r o c l i n e w e r en o t e d .O t h e rm i n e r a l s ,p r e s e n ti nv a r y i n g
, c h e r t( a s
q u a n t i t i e s ,i n c l u d e :m u s c o v i t e( t r a c e )
3 % ), g l a u c o n i t e ( t r a c e ) , o p a q u e c o n s t i t u e n t s
much a s
(1-2%) , and
mudstone c l a s t s (1-3%) (Appendix A ) .
The r o c kv a r i e sf r o ml o o s e l yp a c k e d ,
p o i n tc o n t a c t ,t ot i g h t l yp a c k e d ,
t i p l e concave-convexor
with grainsin
w i t h g r a i n sh a v i n g
mul-
straighb
t o u n d a r i e sS
. q u a s h i n go f
labilemineralconstituents
i n t h e more t i g h t l y p a c k e d
f a b r i c i s common.
The p r i m a r yc e m e n ti nt h er o c k
c r y s t a l s are l a r g e , u p t o
0.1 in.
is c a l c i t e .
The c a l c i t e
(2.5 mm) i n d i a m e t e r
equant,andenclosenumerousframeworkgrains.
,
The cement
i s o fa na g g r a d i n g ,n e o m o r p h i co r i g i na s
shown b y t h e
p r e s e n c e of framework g r a i n s f l o a t i n g i n
the sparrycalcite
c e m e n t .F i n e l yc r y s t a l l i n e
s i l i c a c e m e n to c c u r si nm o s t
72
rock s p e c i m e n s ,b u t
it is more common i n t h e t i g h t l y p a c k e d
S i l i c a i s s u b o r d i n a t e t o c a l c i t e i nt o t a lv o l u m e .
rocks.
were o b s e r v e di nm o s ts a m p l e s .
Minor a m o u n t s o f c l a y m a t r i x
Some o f t h i s " m a t r i x "
may b e s q u a s h e d c l a y - c l a s t s .
a n e a r s h o r e ,r e g r e s -
The G a l l u p s t r a t a a c c u m u l a t e d a s
s i v e , m a r i n es a n db o d ya n di nr e l a t e de n v i r o n m e n t s .S o r t i n g ,
grainsize,
g r a p h i cr e l a t i o n s
c o n c e p to f
t h eu n i t
a s well as s t r a t i -
a n dm i n e r a l o g y( g l a u c o n i t e ) ,
and t h ec o n t a i n e df a u n a ,s u p p o r tt h e
a m a r i n eo r i g i n f o r t h e u n i t .
i s composed o f b i o t u r b a t e d
h o r i z o n t a l l yl a m i n a t e ds a n d s t o n e
lhe l o w e rp a r t
of
and s t r u c t u r e l e s s or
t h a t g r a d e si n t om a r i n e
mud
s t r u c t u r e l e s s t oh o r i z o n -
of D C r o s sS h a l e B
. ioturbated,
t a l l yl a m i n a t e ds a n d sg r a d ei n t om a r i n e
muds i n typical
Holocenelowershorefaceenvironments(Bernardandothers,
1 9 7 0 ) .S o r t i n g
t h eu n i t
and g r a i ns i z ei n c r e a s et o w a r dt h et o po f
and t a b u l a r c r o s s - s t r a t i f i c a t i o n s
are well developed
'Ihese deposits r e s e m b l eu p p e rs h o r e f a c es e d i m e n t st h a ta c c u mulateabovewave-base
(1975)
a s d e s c r i b e d byReineckandSingh
.
L o c a l l y ,b l a c k ,o y s t e rp a t c h
b l a c ks h a l e s
reefs and b i o t u r b a t e d
and small t i d a l c h a n n e l s
l a g o o n a le n v i r o n m e n tf o r
document a c o e x i s t i n g
a t l e a s t p a r t of t h e Gallup.
s t r u c t u r e l e s s t o h o r i z o n t a l l yl a m i n a t e ds a n d sa s s o c i a t e d
w i t ht h el a g o o n a ls e d i m e n t s
d e p o s i t s( H a y e s ,1 9 6 7 )
d e l t a s( B e r n a r d
are similar t o washoverfan
or t h e d i s t a l p o r t i o n s o f t i d a l
and o t h e r s ,1 9 7 0 ) .
?bin
73
I nt h e
a c l a s s i c sequence from
Alamo Day Schoolarea
i s e x p o s e di nt h e
l o w e rs h o r e f a c et h r o u g hd u n ed e p o s i t s
This s e c t i o n i s o v e r l a i nb yc o a l - b e a r i n g
GallupSandstone.
s e d i m e n t so ft h eC r e v a s s e
Canyon Formation.Inthe
a r e at h ec l o s er e l a t i o n so ft h e
commun.,
tubes
1 9 7 7 )w i t h i nt h eu p p e rp a r to ft h e
No beach or d u n ed e p o s i t ss e p a r a t e
these swamp
However, d u e tocontemperaneous
and s h o r e f a c ed e p o s i t s .
e r o s i o n ,d u n e
t o non-
t h e p r e s e n c eo fm a n g r o v e - l i k er o o t
( C h a i f f e t z ,o r a l
sandstone.
G a l l u p sandbody
is well d o c u m e n t e db yc o a l st h a to v e r l i e
marineenvironments
theGallupandby
D Cross
a n db e a c hd e p o s i t so f t e na r en o tp r e s e r v e di n
t h er o c k - r e c o r d( D i c k e r s o na n do t h e r s ,1 9 7 2 ) .
Crevasse CanyonFormation
Givens(1957)extendedtheCrevasse
o fA l l e na n dB a l k( 1 9 5 4 )i n t ot h e
Canyon t e r m i n o l o g y
D Cross a r e a ;a p p l y i n gt h e
f o r m a t i o n a l name t o a t h i c k sequenceofcoal-bearingsands t o n e sa n ds h a l e s
Givens,however
t h a t o v e r l i e t h e G a l l u p( G a l l e g o )S a n d s t o n e .
, made
no attempt t o d e f i n e a n y o f t h e f o r m a l
members o f t h e f o r m a t i o n t h a t
Basin.
are . r e c o g n i z e d i n t h e
San Juan
I h a v er e c o g n i z e dt h r e ed i s t i n c tu n i t sw i t h i nt h e
Crevasse Canyon F o r m a t i o n ;t h e s ea r e ,i na s c e n d i n go r d e r :
(1) basal s a n d s t o n e ,
( 2 ) i n t e r b e d d e ds h a l e
and ( 3 ) u p p e rs a n d s t o n e '.I h e s ed i v i s i o n s
m a l l ya n dc a n n o t ,
andsandstone,
are used i n f o r -
as y e t , be c o r r e l a t e d w i t h t h e members
described b yA l l e na n dB a l k( 1 9 5 4 ) .I nt h eR i l e y - P u e r t e c i t o
a r e a ,M a s s i n g i l l
( 1 9 7 9 ) r e c o g n i z e dt h r e ei n f o r m a ld i v i s i o n s
74
( s i c ) (Crevasse
o fh i su n d i f f e r e n t i a t e dM e s a v e r d eF o r m a t i o n
Canyon F o r m a t i o n ) T
. h e s eu n i t sc o r r e s p o n dr o u g h l yt ot h e
i n t h e D CrossMountainarea.
d i v i s i o n s I h a v eu t i l i z e d
The Crevasse Canyon Formation d i p s g e n t l y t o
the south-
west and is exposed i n a l m o s tc o n t i n u o u so u t c r o pa l o n ga n
east-west l i n e fromPietown,
Mexico.North
New Mexico, t oP u e r t e c i t o ,
New
o f t h i s l i n e , t h e s t r a t ah a v eb e e ne r o d e dd u e
t ou p l i f to ft h eC o l o r a d oP l a t e a u .S o u t ho ft h eo u t c r o p
Canyon is present o n l y i n t h es u b s u r f a c e .
b e l t ,t h eC r e v a s s e
I n g e n e r a l , t h eC r e v a s s e
p i n c h e s - o u tw i t h i nt h e
Mountain (Molenaar
,
Canyon t h i c k e n s t o t h e e a s t and
Mancos S h a l en o r t ho f
1974)
D Cross
.
In t h e D CrossMountainquadrangleanincompletesect i o no fC r e v a s s e
was measuredon
Canyon, 7 9 3 f t ( 2 4 2 m ) t h i c k ( F i g u r e 1 0 )
t h e n o r t hf a c eo f
%e f o r m a t i o n
B l u e Mesa.
may be a p p r e c i a b l y t h i c k e r
, but
v a r i a b l e d i p s , andrugged
t e r r a i n make a c c u r a t e t h i c k n e s s
t h e l a c k o f marker b e d s ,
determinations difficult.
!the Crevasse Canyon c r o p so u ti nt h es o u t h w e s t e r n
northeasternpartsof
t h e Red Lake f a u l t .
t h e mapped a r e a on o p p o s i t e sides o f
The s t r a t a , w h e r en o tp r o t e c t e db y
r e s i s t a n tc a pr o c ks u c h
e r o d e st o
and
as t h e b a s a l t f l o w s
a
on BlueMesa,
form a s e r i e s o f l o w c u e s t a - l i k e h i l l s .
No d i a g n o s t i c m e g a f o s s i l s
Canyon s t r a t a , a l t h o u g h
were o b s e r v e di nt h eC r e v a s s e
a few p o o r l y p r e s e r v e d p e l e c y p o d s
were c o l l e c t e d from t h e l o w e rp a r to ft h ef o r m a t i o n .
Crevasse Canyon r e s t s c o n f o r m a b l yo nt h e
The
l a t e TUronian t o
Feet
Depositional
Environment
75
Fluvial
vertically
stacked
fining
meandering
upward sandstone packages;
no interbedded coals
fining upward channel
sandstones
300
dominantly
dark,
organicDelta
plain
richshale;sandstonessare
lenticular, fine upward and
have cut bases and basal
clay-clast conglomerates;
coal seams locally developed
coal or laterally oyster
biolithites
Coastal marsh
or lagoon
Shoreface
mud] sand
Figure 1 0 . Stratigraphic section of the Crevasse
Canyon Formation. Note fining
upward sandstone units.
76
and is unconformablyover-
e a r l yC o n i a c i a nG a l l u pS a n d s t o n e
l a i nb y
t h e Eocene Baca Formation.
A l a t eC o n i a c i a nt o
e a r l y Eocene a g ea p p e a r sr e a s o n a b l ef o rt h eC r e v a s s e
strata.
PollenfromCrevasse
Canyon
Canyon s h a l e sp a r t i a l l y
s t a n t i a t e st h i sa g ed e t e r m i n a t i o n( C h a i f f e t z ,o r a l
sub-
commun.,
1977).
The b a s a ls a n d s t o n es e q u e n c eo ft h eC r e v a s s e
F o r m a t i o nc o n s i s t s
f t ( 1 5 m) o f s i l t y
of approximately50
s h a l e and a s i n g l e l a t e r a l l y p e r s i s t e n t ,
sandstone.
Canyon
The middle u n i to ft h eC r e v a s s e
30 f t ( 9 m ) - t h i c k
Canyon i s
a p p r o x i m a t e l y 500 f t ( 1 5 2 m) t h i c k a n d c o n s i s t s o f
n o u sr e p e t i t i o no fi n t e r b e d d e ds h a l e s
upper s a n d s t o n es e q u e n c e
a monoto-
The
andsandstone.
is com-
i s 250 f t ( 7 6 m) t h i c k ,a n d
p o s e dp r e d o m i n a n t l yo fs a n d s t o n e
w i t h t h i ns h a l ei n t e r b e d s .
upper s e q u e n c ea r en o t
I n d i v i d u a ls a n d s t o n eb o d i e so ft h e
t h i c k e rt h a nt h o s ei nt h e
middle u n i tb u t ,p a c k a g e so f
v e r t i c a l l y stacked s a n d s t o n e s c o m p r i s e i n t e r v a l s o f c o n s i d e r a b l et h i c k n e s s .
o fs h a l e
The l a c k o f a na p p r e c i a b l et h i c k n e s s
and t h ea b s e n c e s
of c o a l is t h e b a s i s f o r
e n t i a t i o nb e t w e e nt h eu p p e ra n d
Canyon.
me
differ-
middle u n i t s o f t h e C r e v a s s e
upper sequence crops o u t as a s e r i e s of p o o r l y
developedcliffs
on t h e n o r t h a n d e a s t
a n dp r o b a b l yr e p r e s e n t st h e
sides of B l u e Mesa
s t r a t a shown a s PointLookout
S a n d s t o n ei nt h e1 9 6 5e d i t i o no ft h e
New Mexico S t a t e
Geolog i c Map.
Sandstoneswithinthethree
(Plate 14).
I ng e n e r a lt h e y
members are v e r y similar
a r e l e n t i c u l a r , and t h e ya r ei n
77
P l a t e 14.
Channel s a n d s t o n ei nt h eC r e v a s s e
Canyon
cut base,
Formation--thesandstoneunithasa
l e n t i c u l a rg e o m e t r y , and i s a f i n i n g upward
22, T. 3
sequence.
Photograph
taken
in
Section
N. I R. 0 W.
78
shale u n i t or
e r o s i o n a lc o n t a c tw i t he i t h e ra nu n d e r l y i n g
rip-up c l a s t s a r e com-
a n o t h e rs a n d s t o n e .G r a v e l - s i z ec l a y
mon i n t h e b a s e o f
' !%e s a n d s t o n e s
t h e s a n d s t o n ep a c k a g e s .
a r el i g h t - y e l l o w
(5 Y 8 / 6 )
, well
i n d u r a t e d ,c o n c r e t i o n a r y ,
c r o s s - s t r a t i f i e ds u b a r k o s et h a tg r a d e s
t h eb a s et of i n es a n da t
the top.
s e q u e n c eo fs e d i m e n t a r ys t r u c t u r e s
The f o l l o w i n g v e r t i c a 1
is p r e s e n t :
( 1)
( 4 ) zoneofinterbedded
r i p p l e ds a n d s t o n e s
soles.
ed i n t e r v a l
( 3 ) t a b u l a rc r o s s - s t r a t i f i
w i t h sets o fc r o s s - l a m i n a e
struc-
( 2 ) trough
t u r e l e s s t oc r u d e l yt r o u g hc r o s s - s t r a t i f i e dz o n e ,
c r o s s - s t r a t i f i e dz o n e ,
at
fromcoarsesand
as much as 1.5 f t ( 4 6 cm) t h i c k ,
, fine-grained , traction-current-type
and s h a l e s w i t h t r a c k s
and t r a i l s on bed
Ihe d i p d i r e c t i o n o f c r o s s - l a m i n a t i o nf o r e s e t si n d i -
c a t e a n o r t h e a s tp a l e o - f l o wd i r e c t i o n( A p p e n d i x
B).
is
G e n e r a l l yt h eu p p e rf e wi n c h e so fe a c hs a n d s t o n e
moderate-brown
cementedzone
f o r m i n gc a p
( 5 Mi 3 / 4 )
The c a l c i t e
and v e r yc a l c a r e o u s .
r e s u l t si nt h ed e v e l o p m e n to f
a r e s i s t a n t dip-
on which a k a r r e n - t y p ew e a t h e r i n gs u r f a c ed e v e l -
o p s .H i c k o r y - n u ts i z e ,
brown ( 5 YR 4 / 4 )
, carbonate
or i r o n
o x i d ec e m e n t e dc o n c r e t i o n so c c u rs p o r a d i c a l l yw i t h i nt h e
sandstones.
M i n e r a l o g i c a l l y ,t h es a n d s t o n ef r a m e w o r kg r a i n s
are
m o d e r a t e l ys o r t e da n dr o u n d e dt os u b r o u n d e dq u a r t za n da s
much a s 17% p o t a s s i u mf e l d s p a r .
include greychert(3-4%)
Rarer m i n e r a lc o n s t i t u e n t s
, p l a g i o c l a s e( 3 - 1 0 % ) , m i c a s
and a t r a c eo fr o u n d e dz i r c o n( A p p e n d i x
A).
(2%),
Ihe g r a i n sa r e
79
l o o s e l y boundby
s i l i c a and hematitecement
OK
have a c l a y
pore-Cilling matrix.
I n t e r v e n i n gs h a l eu n i t sa r ep o o r l ye x p o s e d ,d u s k y
y e l l o w - g r e e nt ol i g h t - o l i v e( 5
GY 5 / 2
t o 1 0 Y 5/4)
and i r r e g u l a rc a l c i u mc a r b o n a t ea n d
s i d e r i t e c e m e n t e dc o n c r e t i o n sL
. ocally,
thin, structure-
l e s s ,f i n e - g r a i n e d ,i r o no x i d ec e m e n t e ds a n d s t o n e s
seams ( P l a t e 1 5 ) ,
i nt h es h a l eu n i t s .
OCCUK
andcone-in-conelimestone
The t h i c k e s t c o a l seam i n t h e D
Cross a r e a is 2 f t ( 6 1 cm) t h i c k and
i n t e r v a li nS e c .
with
s o l e s , 0.5 f t ( 1 5 a n ) - t h i c k , l e n -
t r a c k s and t r a i l s onbed
t i c u l a rc o a l
silty,
wood impres-
s p l i n t e r yw e a t h e r i n g ,o r g a n i cr i c h ,a n dc o n t a i n
s i o n s ,r a r ep e l e c y p o d s
,
3 0 , T.
3 N.,
R.
D e p o s i t i o n of t h eC r e v a s s e
OCCUKS
within the shale
8 W.
in
Canyon s t r a t a t o o k p l a c e
c o a s t a lm a r s h ,f l u v i a lc h a n n e l
and f l o o dp l a i ne n v i r o n m e n t s .
Dark c o l o r e d s h a l e s t h a t o v e r l i e t h e m a r i n e s h o r e f a c e
l a g o o n a lG a l l u ps a n d s t o n e sc o n t a i n
and
thick laterallypersis-
t e n t C l a s s o p o l l i s p o l l e n - b e a r i n g c o a l s and f i n e s a n d s t o n e s .
"
mese d e p o s i t sa c c u m u l a t e di n
a c o a s t a lb r a c k i s ht of r e s h
watermarshenvironmentbehind
t h e s t r a n d l i n es a n d s t o n e .
S i m i l a ra c c u m u l a t i o n so fp e a ta r e
environmentsandfrom
Shomakerand
t h e r o c k - r e c o r d( R o e h l e r ,1 9 7 7 ;
o t h e r s ,1 9 7 1 ;
1962; and F i s k , 1 9 6 0 ) .
Young, 1955;Gould
swamp.
and Morgan,
The p r e s e n c e of m a n g r o v e - l i k er o o t -
c a s t se x t e n d i n gi n t ot h eu p p e rp a r t s
i n d i c a t e st h a tr o o t e d
known i nR e c e n tc o a s t a l
o f t h e G a l l u ps a n d s t o n e
trees or s h r u b s flourished i n t h e
80
Plate 15.
Coal seam i n t h e Crevasse Canyon Formation--this
seam i s l e s s than 1 f t ( 3 0 cm) t h i c k and cannot
b et r a c e dl a t e r a l l y S. a n d s t o n eu n i td i r e c t l y
above t h e c o a l i s a c r e v a s s es p l a y .
Photograph
was taken i n S e c t i o n 2 1 , T. 3 N., R. 8 W .
81
t h e lower and m i d d l e p a r t o f t h e
S a n d s t o n ea n ds h a l ei n
. .
are similar t o d e p o s i t s
Crevasse Canyon e x h i b i t f e a t u r e s t h a t
t h a t accumulate i n t h e l o w e r r e a c h e s
o f meanderingstream
on a low r e l i e f
s y s t e m st h a td e v e l o p
, c o a s t a lp l a i n .
s a n d s t o n e s are c h a r a c t e r i z e d b y e r o s i o n a l b a s e s ,
c l a s t conglomerates
, fining-upward
textures
g e o m e t r y ,t r a c t i o n - c u r r e n t - t y p ec r o s s - b e d d i n g
basal c l a y -
, lenticular
, and a
d i s t i n c t i v es e q u e n c e
of s e d i m e n t a r y s t r u c t u r e s t h a t i s
generallyassociated
w i t h meandering stream p o i n t - b a r
d e p o s i t s( M a b e r r y 1
, 971).
p a c k a g e ss u g g e s t st h a t
c h a n n e l se x i s t e d ;
p a r t so ft h e
The t h i n n e s so ft h es a n d s t o n e
a s e r i e s o fs m a l la n a s t o m o s i n g
similar t ot h eN i g e r( A l l e n ,1 9 6 5 )a n d
Mississippi River(ColemanandGagliano,1965)
d e l t ap l a i n s .G e n e t i c a l l y - r e l a t e d
!
The
d a r k s h a l e s ,c o a l
seams
c o n t a i n i n ga n g i o s p e r mp o l l e n ,a n dt h i nd i r t ys a n d s t o n e s ,
t h a t are l a t e r a l l y a s s o c i a t e d w i t h t h e c h a n n e l s a n d s t o n e s
representinterdistributarydepositsthataccumulated
b e t w e e ns a n d - f i l lc h a n n e l s .
.
T h e s ei n t e r d i s t r i b u t a r ya r e a s
p r o b a b l yf l u c t u a t e db e t w e e no p e nw a t e r
and a f r e s h water fauna,and
b yd e p o s i t i o no fc l e a ns h a l e s
vegetation-clogged
lakes c h a r a c t e r i z e d
, s t a g n a n t , chemically-reducing
which t h i n c o a l s developed.
swamps i n
Similar g e n e t i cs e q u e n c e s
well d o c u m e n t e do nt h ed e l t ap l a i n
are
of t h eM i s s i s s i p p iR i v e r
( F i s k , 1 9 6 0 )T
. h i n" d i r t y "s a n d s t o n e si n t e r b e d d e dw i t ht h e
f l o o d - b a s i ns e d i m e n t s
are p r o b a b l y c r e v a s s e s p l a y i n o r i g i n .
The upper p a r t of theCrevasse
Canyon i s composed p r i -
m a r i l yo ft h i c k ,l e n t i c u l a rs a n d s t o n ep a c k a g e st h a tc o n s i s t
82
of a s e r i e s o f v e r t i c a l l ys t a c k e dc h a n n e ls a n d s t o n e s .F l o o d
p l a i nc l a y s
and s i l t s a r en o t i c e a b l ya b s e n t .
The s a n d s t o n e s
e x h i b i t c h a r a c t e r i s t i c s similar t o t h e f l u v i a l s a n d s t o n e s i n
t h em i d d l eu n i t
c o a l so c c u ri n
Formation.
and d i f f e r o n l y i n
s i z e andnumber.
No
t h e uppersequenceoftheCrevasse
Canyon
The m a s s i v es a n d s t o n e sr e s e m b l et h o s et h a t
a c c u m u l a t ei nt h eu p p e rr e a c h e so f
system,inan
a meandering stream
area o f slow s u b s i d e n c e , p e r h a p s b e y o n d t h e
h i n g e - l i n eo fc o a s t a ls u b s i d e n c e .
Here t h e c h a n n e l s would
m i g r a t el a t e r a l l yo v e rg r e a td i s t a n c e sr e w o r k i n ga n dr e d i s t r i b u t i n gf l o o dp l a i n
muds w h i l e d e p o s i t i n g o n l y
point-barsandsequence.
a c r o s st h ea r e a
a thin
Each s w e e po ft h er i v e rs y s t e m
would t h e nd e p o s i ta n o t h e rp o i n t - b a r
last.
c h a n n e l - f i l ls e q u e n c ea b o v et h e
The r e s u l t is a
s e r i e s o fv e r t i c a l l ys t a c k e dc h a n n e l ss a n d s .
t h e upperTexas
sandstonepackagesfrom
Thick T e r t i a r y
G u l f Coasthavebeen
a s c r i b e d t o a s i m i l a r mode o f d e p o s i t i o n ( F i s h e r , 1 9 6 8 ) .
I nc o n c l u s i o n ,t h es t r a t ao ft h eC r e v a s s e
Canyon
r e p r e s e n t a t r a n s i t i o n from c o a s t a l marshandlagoonal
c o n d i t i o n ,t h r o u g hd e l t ap l a i nc o n d i t i o n s ,i n t o
a "normal"
m e a n d e r i n gf l u v i a sl y s t e m .
This v e r t i c a ls e q u e n c e
t y p i c a l of a low r e l i e f
, clastic , prograding shoreline.
is
T e r t i a r y System
I
S t r a t a t h a t accumulatedduringtheCenozoicdocument
p e r i o d s of f l u v i a ld e p o s i t i o n ,w i d e s p r e a dv o l c a n i s m ,a n d
a s s o c i a t e de r o s i o n .
The o l d e s tT e r t i a r yr o c k se x p o s e di n
83
t h e D Cross area are Eoceneredbeds
o f t h e Baca Formation
t h a td i s c o n f o r m a b l yo v e r l i eC r e t a c e o u sa g eC r e v a s s e
strata.
a t h i c k ' p i l e of q u a r t z l a t i t e
DuringtheOligocene,
t u f f s and r e l a t e d r o c k s
Canyon
were d e r i v e d from a v o l c a n i c c e n t e r
l o c a t e di nt h eG a l l i n a sM o u n t a i n s .F o l l o w i n gt h ee r u p t i v e
eventsthedetritusstripped
from t h e v o l c a n i c a l l y c o n -
s t r u c t e dh i g h l a n d sa c c u m u l a t e da s
apron.During
a Miocene a l l u v i a n f a n
t h e P l i o c e n e , a s e c o n de r u p t i v ee v e n ts p r e a d
t h i nb a s a l t i cl a v a so v e r
The
a r o l l i n gh i l lt o p o g r a p h y .
l a t e P l i o c e n e was a time o f e r o s i o n andpedimentconstruct i o na s s o c i a t e dw i t hr e g i o n a ll o w e r i n go fb a s e - l e v e l .
BacaFormation
The term Baca Formation was o r i g i n a l l y used i n t h e
R i l e y - P u e r t e c i t o area b yW i l p o l ta n do t h e r s( 1 9 4 6 )f o r
the
lower 687 f t ( 2 0 8 m) of W i n c h e s t e r ' s ( 1 9 2 0 ) D a t i lF o r m a t i o n .
Givens(1957)extendedtheBacaterminologyinto
Mountain area.
Well d a t a i n d i c a t e t h a t
t h e D Cross
2500 f t (760 m ) of
Baca s t r a t a are p r e s e n ti nt h es u b s u r f a c e ,a l t h o u g hi nt h e
DatilMountains
maximum e x p o s u r e s are less t h a n 1 1 0 0 f t ( 3 3 5
m ) t h i c k( S n y d e r
,
1971).In
t h e D Cross Mountainquadrangle,
a minimum of 670 f t ( 2 0 4 m) o fr e d( 5
s t o n e s , a n dr e dt ow h i t e
c o n s t i t u t et h e
R 4/6) s h a l e s and s i l t -
( 5 R 5/4 t o N8) l i t h i c arkoses
Baca Formation ( P l a t e 1 6 ) .
R e g i o n a l l y , Baca, or Baca e q u i v a l e n t s ,a r ee x p o s e df r o m
C a r t h a g e , New Mexico, w e s t w a r di n t oA r i z o n a .S t r a t ac o r r e -
84
Plate 1 6 .
Exposure o ft h e
Baca
Formation--Section
3 5 , T. 3
N., R. 8 W.
The s e c t i o n i s 640 f t ( 1 9 5 m ) t h i c k
and w h i t e
and composed of i n t e r b e d d e dr e ds h a l e
sands tone.
85
l a t i v e w i t h t h e Baca i n c l u d e t h e EagerFormation(Johnson,
1978)andMogollon
R i m g r a v e l si nA r i z o n a
No d i a g n o s t i c f o s s i l s
strata.
( C a t h e r ,1 9 8 0 ) .
wererecoveredfromthe
S i l i c i f i e d wood i s , however
Baca
, p r e s e n ti n
a few
a few smallbonefragments
conglomeratebeds,and
were
c o l l e c t e d from exposures ofBacabelowtheprospectonthe
n o r t h face ofBlue
A
In t h e ' S o c o r r o a r e a , Garfer
Mesa.
c o l l e c t e d middle Eocene r h i n o c e r o s - l i k er e m a i n s
Bacaand
Protoreondon p u m i l u s h a sb e e n
o u t c r o p se x p o s e d
(1910)
from t h e
described fromBaca
west o ft h es t u d ya r e a( S n y d e r ,1 9 7 1 ) .
Vertebrate remains of Eocene t o e a r l y O l i g o c e n e a g e
known from t h e Datil Mountainsand
are
Quemado a r e a s ,T i l i a c e o u s
a n dJ u g l a n d a c e o u s( L i n d e n - w a l n u t )p o l l e nh a v eb e e ni d e n t i f i e d from t h eb a s a l
area (M.
Baca s h a l e s i n
C h a i f f e t z ,o r a l
The c o n t a c to ft h e
commun.,
t h e D CrossMountain
1978).
Baca withtheunderlyingCrevasse
Canyon F o r m a t i o nh a sb e e nc o n c l u d e dl o c a l l yt o
s i o n a l , angularly unconformable
workers.
, or
be:
ero-
conformable by various
'Ihe n a t u r eo ft h ec o n t a c tc a n n o t
be p h y s i c a l l y
demonstrated from t h e l i m i t e d e x p o s u r e s i n t h e s t u d y a r e a .
%e u p p e r c o n t a c t
between t h e BacaandSpearsFormation
is e r o s i o n a l a l o n g t h e n o r t h
Approximately0.5
W.,
face o ft h eG a l l i n a sM o u n t a i n s .
m i (1 km) s o u t h o f Sec. 3 4 , T. 2 N . ,
Spears t u f f s c r o p o u t a p p r o x i m a t e l y
t h ep r o j e c t e dS p e a r s - B a c ac o n t a c t
Mountains.
1 0 0 f t ( 3 0 m ) below
as o b s e r v e d i n t h e G a l l i n a s
No f a u l t i n g i s e v i d e n tb u t
g r a v e l s o b s c u r et h e
R.
field relations.
a t h i c ks e q u e n c eo f
a
86
The b a s e of t h e Bacawas
placedatthefirstoccurrence
o fv a r i e g a t e ds h a l e s .I nt h e
D C r o s sa r e a ,v a r i e g a t e d
s h a l e s occur i n a zonetha.t
t h i c k (Plate 1 7 ) .
is a p p r o x i m a t e l y 50 f t (15 m )
The s h a l e s are s i l t y ,h o r i z o n t a l l y
lami-
, root-mottled ,
( N 4 ) , light-brown
nated to s t r u c t u r e l e s s , s l i g h t l y c a l c a r e o u s
olivegrey(5
( 5 YR 6 / 4 )
Y 6/ 1)
t o medium-dark g r e y
, greyish-purple(5
Ironstonenodulesand0.5-1.0
P 6/2)
, a n dy e l l o w( 5
Y 7/4).
f t (15-30cm)-diameter,black
t o y e l l o w ( N 2 t o 5 Y 7 / 4 ) ,s e p t a r i a n - l i k ec a r b o n a t ec o n c r e i s considered
t i o n sa r el o c a l l ya b u n d a n t .T h i sb a s a lz o n e
Canyon and is composed o f , i n
“ t r a n s i t i o n a l “t ot h eC r e v a s s e
a
p a r t , r e w o r k e dC r e t a c e o u s t r a t aJ. o h n s o n( 1 9 7 8 r) e p o r t e d
much a s 250 f t ( 7 6 m ) t h i c k ,
s i m i l a rt r a n s i t i o nz o n e ,a s
betweenthe
D.
Baca andCrevasse
C h a m b e r l i n( o r a l
commun.,
zone” may b e a c t u a l l y
Canyon i n t h e DatilMountains.
1 9 8 0 )b e l i e v e st h i s“ t r a n s i t i o n
a w e a t h e r e dz o n ei nt h et o po ft h e
Crevasse Canyon F o r m a t i o n .A n o t h e rp o s s i b i l i t y
v a r i e g a t e ds h a l e s
is t h a t t h e
are ofPaleoceneage.
?he Baca c o n s i s t s p r i n c i p a l l y o f s i l t y s h a l e s i n
numerous4-30
b e d so c c u r .
f t (1.2-9.1
m ) - t h i c k ,l e n t i c u l a rs a n d s t o n e
?he s h a l e sa r er e d( 5
careous to s l i g h t l y c a l c a r e o u s ,
structureless.
0.1-.02
which
R 4 / 6 ) ,s i l t y ,n o n c a l andvaguelylaminated
or
‘&in, i r r e g u l a ri r o n s t o n el a y e r s ,i s o l a t e d ,
i n . ( . 2 5 - . 5 0c m ) - d i a m e t e r ,b o t r y o i d a li r o no x i d e
n o d u l e s ,a n dp e a - s i z e ,w h i t e( N 7 )
, calcium
or t h i n c a l i c h e b e d s o c c u r s p o r a d i c a l l y w i t h i n
c a r b o n a t en o d u l e s
the section.
07
P l a t e 17.
S h a l es t r a t ai nt h eb a s e
of t h e Baca Formation-t h es h a l ei n t e r v a l
i s approximately 5 0 f t ( 1 5 m )
t h i c k and composed of v a r i e g a t e d ,c o n c r e t i o n a r y
s h a l eo fp o s s i b l eP a l e o c e n e
age.
88
Thin structureless
or h o r i z o n t a l l y l a m i n a t e d
, muddy,
s l i g h t l yc a l c a r e o u s ,f i n e - g r a i n e d ,r e d
( 5 R 5/4) l i t h i c
a r k o s e s are common i n t h e s h a l eu n i t .
The s a n d s t o n e sr a n g e
from 0.1-3.0
f t ( - 2 5 cm-1 m ) t h i c k and h a v ee r o s i o n a l
or
g r a d a t i o n a lc o n t a c t sw i t ht h ee n c l o s i n gs h a l e s .
Thicker s a n d s t o n ep a c k a g e sa r ef i n i n g - u p w a r ds e q u e n c e s
composed o f medium- t o c o a r s e - g r a i n e d , m o d e r a t e l y s o r t e d
i n d u r a t e d , c a l c i t e cemented ar koses.
,
These s a n d s t o n e s a r e
a s much as 30 f t ( 9 m ) t h i c kb u tp i n c h - a n d - s w e l ll a t e r a l l y .
The b a s e of a t y p i c a l s a n d s t o n e
s h a l e or a n o t h e rs a n d s t o n eu n i t .
cal s a n d s t o n e is s t r u c t u r e l e s s
troughcross-stratified
w e d g e - s e t st h a ta r e
s h a l er i p - u p
stones.
is erosionalintoeither
The l o w e rh a l fo f
a typi-
, h o r i z o n t a l l yl a m i n a t e d
or
and may c o n t a i n z o n e s . o f t a b u l a r
u p t o 1 f t ( 3 0 cm) t h i c k .L a r g e ,r e d
c l a s t s a r e common a t t h e b a s e
The u p p e rp a r to f
of t h e sand-
a t y p i c a ls a n d s t o n e
is medium-
g r a i n e d and e x h i b i t st h ef o l l o w i n gv e r t i c a ls e q u e n c eo f
(1) h o r i z o n t alla m i n a t i o n ,
s e d i m e n t a r ys t r u c t u r e s :
( 2 ) z o n e so fs m a l la s y m m e t r i c a l
r i p p l e s ; l o c a l l yc l i m b i n g ,
and ( 3 ) h o r i z o n t a ll a m i n a t i o nw i t hr a r ec o n t o r t e dl a m i n a e .
The sandstone body
b ys h a l e ,
may b e g r a d a t i o n a l l y or s h a r p l y o v e r l a i n
or i t may be i n e r o s i o n a l c o n t a c t w i t h a n o v e r -
l y i n gs a n d s t o n e .
A s i n g l e , 6 f t ( 3 m)
thick,dip-slopeformingconglom-
e r a t e crops o u ta p p r o x i m a t e l y
t h e BacaFormation.
70 f t (24 m ) above t h e b a s eo f
The conglomerate is c o n t i n u o u st h r o u g h -
89
o u t t h e D CrossMountainareaand
conglomerate west of D CrossMountain
quadrangle.
a similar
I haveobserved
i nt h e
CalShip
Mesa
The c o n g l o m e r a t eh a sa ne r o s i o n a lb a s ea n d
is
composed o fr a n d o m l yo r i e n t e d ,e q u a n tt ob l a d e d ,r o u n d e d
p e b b l e sa n dc o b b l e s
of v a r i o u s l y c o l o r e d q u a r t z i t e
and
c h e r t , a r k o s i c s a n d s t o n e , g r e y (N6) f o s s i l i f e r o u s P a l e o z o i c
me
l i m e s t o n e ,a n dg r a n i t e .
i n .( 1 5
cm) i nd i a m e t e r .
l a r g e r c l a s t s a r e as much as 6
This conglomerate may s e p a r a t et h e
Eocene Baca f r o mt h eu n d e r l y i n g ,p e r h a p sP a l e o c e n e ,v a r i e -
litter the
g a t e ds h a l ez o n e .A b u n d a n tg r a v e l - s i z ec l a s t s
s l o p eh i g h e r
i n t h es e c t i o n ;b u t ,
a source f o r t h e m a t e r i a l
c o u l dn o tb el o c a t e d .
M i n e r a l o g i c a l l y t h e Baca s a n d s t o n e s a r e l i t h i c a r k o s e s
and a r k o s e s .Q u a r t z
c o m p r i s e so n l y
50-608
ture ofsinglegrains
is t h e m o s ta b u n d a n tc o n s t i t u e n tb u t
of t h er o c k .
The g r a i n sa r e
a mix-
a n dc o m p o s i t eg r a i n sw h i c hh a v ee i t h e r
undulose or s t r a i g h te x t i n c t i o n .
Most a r ei n c l u s i o n
free
althoughgrainswithbubbles,bubbletrains,andmicrolite
i n c l u s i o n sd oo c c u r .
The q u a r t zg r a i n s
are g e n e r a l l y
subrounded.
F e l d s p a r s comprise 2 0 % of t h e framework g r a i n s (Append i x A).
Most are potassium feldspars (13%).
is common, and
t h em o s ta b u n d a n tK - f e l d s p a r ,m i c r o c l i n e
p e r t h i t eg r a i n s
are r a r e .
Orthoclase is
Most of t h eK - f e l d s p a r sg r a i n s
are subrounded, moderately weathered
, anddue
to vacuoli-
z a t i o n and k a o l i n i z a t i o n , a p p e a r c l o u d y i n p l a i n - l i g h t ,
a l t h o u g ht h es p e c t r u mf r o mf r e s ht oi n t e n s e l yw e a t h e r e d
g r a i n sa r ep r e s e n t .P l a g i o c l a s eg r a i n sc o m p r i s e
8% o f t h e
90
s a n df r a c t i o n .P a r t i a la l t e r a t i o no ft h e s eg r a i n st o
s e r i c i t e or i l l i t e i s common.
p l a g i o c l a s et o
S e l e c t i v ea l t e r a t i o no f
i l l i t e or s e r i c i t e w i t h i n p e r t h i t e g r a i n s
is
a1 so n o t e d .
O t h e rc o n s t i t u e n t sc o m p r i s ea p p r o x i m a t e l y
r o c kT
. h e s ei n c l u d eg r e y
1 2 % of t h e
(N4) m i c r o c r y s t a l l i n ec h e r t
(6%),
l i m e s t o n e ( 2 % ) , m u s c o v i t e (1%), g r a n i t e and q u a r t z s c h i s t
( 3 % ) , c h l o r i t e ( t r a c e ) , b i o t i t e ( t r a c e ) , and h e a v ym i n e r a l s
(trace).
The rock is c e m e n t e db yb l o c k ys p a r r yc a l c i t e .
c a r b o n a t ec r y s t a l sa r ea sl a r g ea s
eter.
0.3 in.
The
( 8 mm) i n diam-
Other c e m e n t i n ga g e n t sa r er a r e l yp r e s e n t ,a l t h o u g h
f i n e - g r a i n e d ,p o o r l ys o r t e ds a n d s t o n e s
matrix
may have a c l a y
.
I nt h e
m u l a t e di n
D C r o s sM o u n t a i na r e a ,t h e
Baca s t r a t a accu-
a s e r i e s o fs o u t h e a s tf l o w i n gm e a n d e r i n g
a sc h a n n e l - f i l l
streams,
and f l o o dp l a i nd e p o s i t s .V e r t e b r a t ef o s s i l
r e m a i n sa n da s s o c i a t i o nw i t ho t h e rc o n t i n e n t a le n v i r o n m e n t s
a r es t r o n ge v i d e n c ef o r
t h e c o n t i n e n t a lo r i g i no ft h er o c k
unit.
R e g i o n a l l y , many l o c a l s o u r c e s
Formation(Johnson,1978;andCather,1980).
o f p e b b l e - s i z e dc l a s t si nt h e
Paleozoic granitic
e x i s t e d f o rt h e
Baca
The l i t h o l o g y
Baca s u g g e s t s a P r e c a m b r i a nt o
, metamorphic , and sedimentary provenance.
Rounding of t h e l a r g e s t
c l a s t s i n d i c a t e s on t h e o r d e r o f
m i (160 km) of t r a n s p o r ta n dc r o s s - l a m i n a ei nt h eu p p e rp a r t
oftheformationgive
a southeasterlypaleo-flowdirection
100
91
This d a t as u g g e s t st h a tt h e
(Appendix B ) .
Zuni Mountains
rocks t h a t c r o p o u t i n t h e
werederivedfrom
o f New Mexico.
l a n d s , however
Baca s e d i m e n t s
from theMogollonhigh-
I n f l u xo fs e d i m e n t s
, ist documentedby
t h e p r e s e n c eo fs a n d - s i z e d
v o l c a n i cr o c kf r a g m e n t sa n dc r o s s - l a m i n a et h a ti n d i c a t e
a
t h e lower 1/3 o f t h e
more n o r t h e r l y p a l e o - f l o w d i r e c t i o n i n
u n i t .C a t h e r( 1 9 8 0 )h a sd o c u m e n t e dt h a t
much o ft h e
exposed i n t h eG a l l i n a sM o u n t a i n ss o u t h e a s t
Baca
o f t h e D Cross
a r e a was d e p o s i t e di nn o r t h - f l o w i n gs t r e a m sa n di na n
a s s o c i a t e dl a k e - d e l t a
complex.
The s o u r c ef o rt h e s e
s e d i m e n t s was s t r o n g l yi n f l u e n c e db yt h eM o g o l l o nh i g h l a n d s .
Lenticular
, fining-upwardsandstonesthathave
cut
b a s e s and b a s a l c l a y - c l a s t c o n g l o m e r a t e s a r e i n t e r p r e t e d t o
b ec h a n n e l - f i l ld e p o s i t s .T h e s es a n d s t o n e se x h i b i t
is s i m i l a rt o
s e q u e n c eo fs e d i m e n t a r ys t r u c t u r e st h a t
, V i s h e r( 1 9 7 2 ) , andBernard
V e r t i c a ls t a c k i n go fg e n e t i cu n i t s
a
a s d e s c r i b e db y
t y p i c a lm e a n d e r i n gs t r e a mp o i n t - b a rs a n d
A l l e n( 1 9 6 4 )
a
and o t h e r s ( 1 9 7 0 ) .
is common.
Horizontally
laminated and r i p p l e df i n e - g r a i n e ds a n d s t o n e st h a ta r e
l a t e r a l l ya s s o c i a t e dw i t ht h ec h a n n e l - f i l ls e q u e n c e sa r e
similar t o n a t u r a l l e v e e d e p o s i t s o f t h e B r a h m a p u t r a R i v e r
(Coleman,1969).
The h i g h c l a y c o n t e n t
suspended-loadmeandering
mud-covered
f l o o dp l a i n s
o f t h e Baca is e v i d e n c e of a h i g h
stream s y s t e m , b e c a u s e e x t e n s i v e
are r e q u i r e d f o r bank s t a b i l i z a t i o n
b e f o r em e a n d e r i n gc a no c c u r( B e r n a r da n do t h e r s ,1 9 7 0 ) .
Mudstones make up60%oftheBacaFormation.
The mudstones
92
a r e r e d , e x h i b i t d e s i c c a t i o nf e a t u r e s ,c o n t a i nc a l i c h e
and are r o o t m o t t l e d .
n o d u l e sa n dv e r t e b r a t ef o s s i lr e m a i n s ,
S i m i l a rd e p o s i t sa c c u m u l a t e
a l o n gt h ec o u r s e so f
on i n t e r f l u v i a l f l o o d p l a i n s
many l a r g e m e a n d e r i n g
streams (Bernard
and o t h e r s ,1 9 7 0 ) .T h i ns a n d s t o n e sw i t h i n
th e dominantly
mud i n t e r v a l may be o f c r e v a s s e s p l a y o r i g i n .
Cather ( 1 9 8 0 )b e l i e v e st h a t
t h e red c o l o r a t i o n of t h e
Baca s t r a t a i s a d i a g e n e t i c phenomenonand
accumulatedunder
climate
."
a "hot,semiarid
The e x t e n s i v em e a n d e r i n g
t h a t t h e Baca
, possiblesavanna-like
stream complexes
t h e D Cross M o u n t a i na r e as u g g e s tt h a t
d e v e l o p e di n
wetter, perhapssubhumid
a
climate e x i s t e d .
Spears Formation
The S p e a r s Member was o r i g i n a l l y s e p a r a t e d
W i n c h e s t e r ' s( 1 9 2 0 )
from
D a t i l FormationbyTonking(1957).
Givens(1957)extended
t h e S p e a r st e r m i n o l o g yi n t o. t h e
S p r i n gq u a d r a n g l eb u tu s e dt h e
t h e Datil Formation.
Dog
term S p e a r s Ranch Member of
The u n i t was e l e v a t e dt of o r m a t i o n a l
rankandrenamedtheSpearsFormationbyChapin(1974).
The Spears i s a ne x t e n s i v eu n i tc r o p p i n go u ti nt h e
D a t i l , Bear
I
Iemitar, G a l l i n a s , Magdelena,andChupadera
M o u n t a i n s a, n dJ o y i t a
e q u i v a l e n tt ot h e
Hills.
The S p e a r s i s p r o b a b l y
Rubio Peak F o r m a t i o ni n' t h ee a s t - c e n t r a l
p a r to ft h eD a t i l - M o g o l l o nv o l c a n i cf i e l d
commun.
,
1980).
(C.
C h a p i n ,o r a l
A t t h e r e f e r e n c es e c t i o n ,i nt h en o r t h e r n
Bear M o u n t a i n s ,t h eS p e a r sc o n s i s t s
of approximately 1200 f t
93
accumulated a s a
( 3 6 5 m) o fs a n d s t o n ea n dc o n g l o m e r a t et h a t
v o l c a n i c l a s t i ca p r o na r o u n da nO l i g o c e n ev o l c a n i c
, 1979).
(ChapinandSeager,1975;andMassingill
Cross Mountainquadrangle,
f t ( 6 1 0 m ) t h i c ka n d
field
I nt h e
D
t h e S p e a r s is a p p r o x i m a t e l y 2000
is composed p r e d o m i n a n t l y o f t u f f
b r e c c i a s and v o l c a n i c l a s t i c s e d i m e n t a r y r o c k s .
'Ihe n o r t h e r n face o ft h eG a l l i n a sM o u n t a i n sa n d
s o u t h e r np a r to fB l u e
Mesa ( n o r t h e r n Datil M o u n t a i n s )a r e
p r i m a r i l yu n d e r l a i nb yS p e a r sl i t h o l o g y .
w e a t h e r i n go f
t h e r o c kr e s u l t si nt h ed e v e l o p n e n to fs m o o t h -
s i d e d h i l l s and v a l l e y s i n
Throughoutthe
overliesthe
'Ihe r e s i s t a n c et o
which e x p o s u r e s are poor.
D Cross a r e a , t h eS p e a r sd i s c o n f o r m a b l y
Baca Formationand
is s e p a r a t e db ya na n g u l a r
mapped area
unconformity from y o u n g e rs t r a t a .S o u t ho ft h e
h o w e v e r ,t h e
Spears is c o n f o r m a b l y o v e r l a i n b y
o fa s h - f l o wt u f f s
a thick pile
andflowrocks(Givens,1957;and
H a r r i s o n 1, 9 8 0 ) .
I nt h es t u d y
area, t h e S p e a r s
is composed o f a s u i t e o f
r o c kt y p e st h a ti n c l u d e sl i t h i c - c r y s t a la n dc r y s t a l - l i t h i c
t u f f s and v o l c a n i c l a s t i cs e d i m e n t a r yr o c k s .V o l c a n i c l a s t i c
rocks a r e t h em o s ta b u n d a n tr o c kt y p e s .
t h eu n i t
is p r e d o m i n a n t l yl i g h t - g r e y
The lower p a r t o f
(N7) t u f f ( P l a t e 1 8 )
w h i c hg r a d e sv e r t i c a l l yi n t ov o l c a n i c l a s t i cr o c k s .
p o o re x p o s u r e s ,l a c k
of distinctive marker
beds, s t r u c t u r a l
complication,andthelenticularityofthelithotypes,
bers were n o t d e l i n e a t e d d u r i n g m a p p i n g .
Due t o
mem-
94
plate 18.
C r y s t a l - l i t h i c t u f f s intheSpearsFormation.
The t u f f s a r e q u a r t z - r i c h
and pumicepoor.
D e v i t r i f i c a t i o n of t h e groundmass is e x t e n s i v e .
Photographtaken
on t h e west side of Dog Springs
Canyon approximately 1 m i ( 1 . 6 km) s o u t ho ft h e
Martin Ranch h o u s e .
95
G e n e r a l l y ,t h e
t u f f s a r el i g h t - g r e y
(N7), l i t h i c show l i t t l e
c r y s t a la n d ,d u et oe x t e n s i v ed e v i t r i f i c a t i o n ,
evidenceofwelding
or compaction.
small p e b b l es i z e ,
rangefromsandto
The l i t h i cf r a g m e n t s
and a r e composed
p r e d o m i n a n t l yo fr o u n d e dt oa n g u l a rv o l c a n i cr o c kf r a g m e n t s
t h a ta r el i t h o l o g i c a l l ys i m i l a rt ot h ee n c l o s i n gt u f f
matrix.
Sand s i z e c l a s t s o f q u a r t z a r e n i t e s
limestones,granites,
, fossiliferous
and g n e i s s e s a r e a l s o p r e s e n t
P h e n o c r y s t sw i t h i nt h et u f f si n c l u d es t r o n g l y
quartz (rare)
, zoned , e u h e d r a l
and a t r a c eo fa u g i t e
embayed
andhave
a more c a l c i c
(common) , o p a q u e m i n e r a l s
(common) ,
a n ds a n i d i n e .D e v i t r i f i c a t i o no ft h e
groundmass m a k e s d e t a i l e d s t u d y o f t h e r o c k d i f f i c u l t .
f l u o r e s c e n c ea n a l y s i so f
X-ray
a S p e a r s t u f f i n d i c a t e sa p p r o x i -
m a t e l y 68% s i l i c a (Table 1).
Debris f l o w s are common i n t h e S p e a r ss e c t i o n .B o t h
monomicticandpolymictic
d e b r i s f l o w sa r ep r e s e n t .
e r a l l y t h e c l a s t s are e i t h e r u n i f o r m l y r o u n d e d
tered.
or i n t r u s i v e i g n e o u s o r i g i n
Gen-
or a n g u l a r ,
and are v o l c a n i c i n o r i g i n .O c c a s i o n a lc o b b l e s
o fs e d i m e n t a r y
.
or b r o k e n a n d e s i n e ( a b u n d a n t )
that exhibitsmultiplegrowthstages
c o r e , euhedral amphibole
(0-10%)
or b o u l d e r s
are a l s o encoun-
D e b r i sf l o w sc o n t a i n i n ge n o r m o u sb l o c k so ff o s s i l -
iferousPaleozoiclbestone
are common i n t h e b a s e o f t h e
formation.
Rare rock types w i t h i n t h e u n i t i n c l u d e b l a c k
b a s a l t i c a u t o b r e c c i a s and t h i n , c r o s s - s t r a t i f i e d
y e l l o w (5 Y 7/6) v o l c a n i c a r e n i t e s .
(Nl)
, moderate-
The l a t t e r rock types
96
OXIDE
Blue Mesa Basalt
Si0
6 7 905
47.384
Ti02
0.741
2.614
14.649
14.079
Fe 0
2 3
4.766
11.464
Mg 0
2.081
8.902
Ca 0
3.888
9.409
Na20
3.883
2.971
2.784
1.110
0.076
0.186
0.413
0.706
101.186
98.826
A1203
K2O
Mn02
Total %
TABLE 1
X-ray Fluorescence Analyses of Volcanic Rocks
from the D Cross Mountain Area
97
i n the
are c o n f i n e dt ot h es o u t h e r n m o s te x p o s u r e s
quadrangle.
is r e l a t i v e l y
BeddingwithintheSpearsFormation
c h a o t i c w i t h d i p sc h a n g i n ge v e r y
few t e n s o f
t h e g e n e r a l d i p is t ot h es o u t h w e s t .
feet, although
An u n u s u a ls t r u c t u r e
0.5 m i ( 0 . 8 km) s o u t ho f
o c c u r si nt h et u f f sa p p r o x i m a t e l y
m e r e , l i g h t - g r e yc r y s t a l - l i t h i c
theFredMartinRanch.
t u f f s d i p a s much a s 80
0
s t r i k e s t h a tc u r v et h r o u g h
andhave
0
a 1 8 a0r c .
S e v e r a lc r y s t a l - r i c ht u f fs a m p l e s
were c o l l e c t e df o r
r a d i o m e t r i cd a t i n g U
. n f o r t u n a t e l yt h i n - s e c t i o na n a l y s e s
of s m a l lx e n o l i t h s
i n d i c a t e dt h ep r e s e n c e
x e n o c r y s t si na l ls p e c i m e n s
f i e r e f o r e ,n or a d i o m e t r i cd a t e s
(G.
and p o s s i b l e
O s b o r n ,o r a l
commun., 1 9 7 9 )
were a t t e m p t e d .
.
f i e Spears
o v e r l i e s Eocene Baca s t r a t a and i s l a t e r a l l y e q u i v a l e n t t o
r o c k so ft h e
b e e nd a t e da s
Bear Mountains-Joyita
3 3 t o 37 m.y.
Hills a r e a , t h a t h a v e
o l d ( C . C h a p i n ,o r a l
commun.,
1980).
The S p e a r ss t r a t aa c c u m u l a t e di nn u m e r o u sg e n e t i c a
r e l a t e de n v i r o n m e n t s
i n close p r o x i m i t y t o
T e r t i a r yc a u l d r o nc o m p l e x .
Mapping i nt h e
.11y
a suspected
D Cross Moun t a i n
and Dog S p r i n g sq u a d r a n g l e sh a sn o t ,h o w e v e r ,d e l i n e a t e d
e i t h e r a s t r u c t u r a l or geomorphiccauldronmargin.In
the D
Cross M o u n t a i nq u a d r a n g l et h eS p e a r su n c o n f o r m i t yo v e r l i e s
t h e Baca Formation.Southofthe
mapped a r e a ,t h eS p e a r s
c o v e r e db yy o u n g e ra s h - f l o wt u f f s( H a r r i s o n 1
, 980).
It is
is
98
c o n c e i v a b l et h a t
a c a u l d r o nc e n t e r
i s c o n c e a l e di nt h e
s o u t h e r nG a l l i n a sM o u n t a i n s .
?he t h i c ka c c u m u l a t i o no fm u d f l o w si nt h e
D C r o s sa r e a
a largeeruptive
suggestsdepositionincloseproximityto
c e n t e r .A l t h o u g ht h et e c t o n i cf r a m e w o r ka s s o c i a t e dw i t h
d e p o s i t i o no ft h eS p e a r s
is n o t f u l l y u n d e r s t o o d , t h e s t r a t a
a r e similar t o mudflowapronsthataccumulatearoundcauld r o nc e n t e r s
i n o t h e ra r e a s .L a r g eb l o c k so fP a l e o z o i c
l i m e s t o n ei nt h eS p e a r sF o r m a t i o np r o b a b l yr e p r e s e n t
t h a t was t r a n s p o r t e d i n t o t h e
debris
area from a Laramide h i g h as
clasts within debris flows.
A t t i t u d e s o ft h eS p e a r ss t r a t aa r ee r r a t i c ,c h a n g i n g
e v e r y f e w hundred f e e t .
a l s op r o n o u n c e d .
are
L a t e r a lv a r i a t i o n si nl i t h o l o g y
lhe c h a o t i c d i p s a r ed u et ob o t hp e n e c o n -
t e m p o r a n e o u ss o f ts e d i m e n td e f o r m a t i o na n dt ot h eo r i g i n a l
d i p s o f debris f l o w st h a t
were d e p o s i t e di na ne n t r e n c h e d
c h a n n e ls y s t e m .
Conglomerate of RockTankCanyon
-<
*
"
Approximately 2 9 0 f t ( 8 8 m ) o fc o a r s es a n d s t o n e
c o n g l o m e r a t e crop o u t east o ft h e
e x p o s u r e so ft h eu n i to c c u ri n
is h e r e r e f e r r e d t o
Red Lake f a u l t .
and
?he b e s t
Rock Tank Canyon a n dt h eu n i t
a s t h e c o n g l o m e r a t eo f
Rock Tank Canyon.
These same s t r a t a were e a r l i e r d e s i g n a t e d S a n t a
Fe Formation
b yG i v e n s( 1 9 5 7 ) .
An a t t e m p t t o
Galushaand
r e s t r i c t t h eS a n t a
B l i c k ( 1 9 7 1 )h a sn o t
Fe t e r m i n o l o g yb y
been well receivedandmost
99
“late T e r t i a r yv a l l e y
f i l l of A t l a n t i c d r a i n a g e ”i n
Mexico i s p r e s e n t l yc o n s i d e r e dt o
New
be Santa Fe Formation
( E l s t o n ,1 9 7 6 ) .B e c a u s et h er e l a t i o n so ft h ec o n g l o m e r a t e
or t o t h e
of Rock Tank Canyon t oo t h e rc o n g l o m e r a t eu n i t s ,
r e g i o n a ld r a i n a g ep a t t e r nd u r i n gd e p o s i t i o na r en o tf u l l y
u n d e r s t o o d , I h a v eo p t e dn o tt oa p p l y
a f o r m a ll i t h o s t r a t i -
g r a p h i c name t o t h e u n i t .
Ihe c o n g l o m e r a t eo f
Rock Tank Canyon i s e x p o s e di n
t o t h e Red Lake f a u l t from
d i s c o n t i n u o u so u t c r o pa d j a c e n t
thevicinityofBlue
area.
Mesa Tank northwardbeyondthe
a similar conglomeratehave
I s o l a t e do u t c r o p so f
r e p o r t e ds o u t h
mapped
of t h e s t u d y a r e a
andfrom
been
?res Hermanos Mesa
and Table Mountain Mesa ( G i v e n s ,1 9 5 7 ) .
%e conglomerate r e s t s w i t h a n g u l a r i t y o n o l d e r s t r a t a
Spears , Baca ( P l a t e 1 9 )
o ft h e
, and
Crevasse Canyon Forma-
t i o n s ,f r o ms o u t ht on o r t h ,a n da p p e a r st oh a v eb e e n
d e p o s i t e do n
a n o r t h - s l o p i n gs u r f a c e .
Sec. 35, T. 3 N.
e x p o s e ds e c t i o n so c c u ri n
t h en o r t he n do ft h en o r t h - t r e n d i n gr i d g e .
ity,the
base of t h ec o n g l o m e r a t e
with Baca s t r a t a .
The t h i c k e s ta n d
, R.
8 W.
best
, along
A t t h a tl o c a l -
is i ne r o s i o n a lc o n t a c t
Local r e l i e f on t h ec o n t a c t
is o n l y 1-2
f t (30-61 m).
Ihe conglomerateof
Rock Tank Canyon i s t h o u g h tt ob e
o f l a t e Miocene t oP l i o c e n ea g e .
from t h e s t r a t a and t h ea g e
and s t r a t i g r a p h i cr e l a t i o n s .
No f o s s i l s were c o l l e c t e d
i s t h e r e f o r e based on s t r u c t u r a l
The u n i ta n g u l a r l yo v e r l i e s
t h eO l i g i o c e n eS p e a r sF o r m a t i o nb u t
is c u t b y t h e
Red Lake
100
Plate 19.
Conglomerate of b c k Tank Canyon. The l i g h t - g r e y
hillsinthe
background a r e composed o f 2 9 0 f t
( 8 8 m ) of v o l c a n i cp e b b l ec o n g l o m e r a t e s .
This
conglomerate is i n erosional c o n t a c tw i t hr e d
Baca Formation s t r a t a . Photograph was taken
l o o k i n gs o u t h w e s t
from S e c t i o n 3 6 , T. 3 N . , R . 8 W.
101
fault.
Latest movement along t h e f a u l th a sb e e nt e n t a t i v e l y
e s t a b l i s h e d a s l a t eP l i o c e n e .
?he c o n g l o m e r a t eu n i t
composed o f l i g h t - g r e y
is a fining-upwardsequence
(N7) s t r u c t u r e l e s s t o h o r i z o n t a l l y
laminatedconglomeratesandinterbeddedpinkish-grey
8 / 1 )s a n d s t o n e s .
( 5 YR
Near t h eb a s eo ft h eu n i t ,t h i n -t o
m e d i u m - t h i c kl e n t i c u l a rb e d so fm o d e r a t e l y
to poorlysorted,
indurated , large-pebbleconglomeratesarethedominantrock
type.
Ihe l a r g e r c l a s t s are a s much a s 8 i n . ( 2 0 an)
d i a m e t e rb u ta v e r a g eo n l y
0.5
i n . (1.3 cm) i nd i a m e t e r .
'Ihe c l a s t s are g e n e r a l l y p l a t y t o
compact, i m b r i c a t e d ,
quartz
subangulartosubroundedpebblesandcobblesof
l a t i t et u f f .
c l a s t s o c c u ri n
Black ( N l ) b a s a l t ,l i m e s t o n e ,a n ds a n d s t o n e
t r a c e amounts.
The r o c k i s g r a i ns u p p o r t e d
and h a s a l i g h t - g r e y ( N 7 ) t of a i n t - p i n k
( 5 YR 8/1) c a l c a r e -
ous , muddy, v o l c a n i c a r e n i t e m a t r i x .
?he u p p e rp a r to ft h ec o n g l o m e r a t eo f
i s composed o f l i g h t - p i n k
( 5 E 8/1)
Rock Tank Canyon
, v e r yp e b b l y ,c o a r s e -
g r a i n e dh o r i z o n t a l l ya n dt a b l u l a rc r o s s - s t r a t i f i e dv o l c a n i c a r e n i t e s( A p p e n d i x
A).
The s a n d s t o n e sa r em o d e r a t e l y
s o r t e d and are composed o fv o l c a n i cr o c kf r a g m e n t s ,f e l d s p a r s , and q u a r t z g r a i n s t h a t
are c e m e n t e d b y c a l c i t e
or ,
l o c a l l y ,b ya nu n i d e n t i f i e dz e o l i t e .P l a c e r so fd a r k c o l o r e dh e a v ym i n e r a l so c c u ra l o n gi n d i v i d u a ll a m i n a e .
O f t e nt h es a n d s t o n e sg r a d el a t e r a l l ya n dv e r t i c a l l yi n t o
conglomerates and occasionally, thin, discontinuous
, mud-
102
s t o n e st h a te x h i b i td e s s i c a t i o nc r a c k s
and t h i n ,w h i t e( N 9 )
c a l i c h eh o r i z o n so c c u ri nt h es a n d s t o n es e q u e n c e .
The conglomerate of Rock Tank Canyon a c c u m u l a t e di n
a
a
l a r g en o r t h w a r de x t e n d i n ga l l u v i a lc o m p l e xt h a td e p o s i t e d
s e d i m e n t a r ya p r o na r o u n d
t h e f l a n k so f
t h e S p e a r sv o l c a n i c
L o c a l l yd e r i v e dv o l c a n i cp e b b l e sw i t h i n
pile.
s i z e t o w a r dt h et o po ft h eu n i ts u g -
t h ed e c r e a s ei ng r a i n
gestderivation
t h e u n i ta n d
f r o me r o s i o no f
t h e SpearsFormationduring
a p e r i o d of t e c t o n i cq u i e s c e n c e .
angular,locallyderived
The p r e s e n c eo fl a r g e ,
c l a s t s , o x i d i z e dc o l o r ,m u d - c r a c k s ,
t e x t u r a l c h a n g e s ,a n dr e l a t i o n st o
c a l i c h eh o r i z o n s ,r a p i d
o t h e rc o n t i n e n t a ls t r a t a
are c h a r a c t e r i s t i c s commonly
a s s o c i a t e dw i t ha l l u v i a lf a nc o m p l e x e s( B u l l ,1 9 7 2 ) .
Len-
t i c u l a rb e d d i n g ,p r e v a l e n c eo fc r o s s - s t r a t i f i c a t i o n sa n d
c l o s e resemblance t o
r a p i d l a t e r a l c h a n g e si nt e x t u r eb e a r
s e d i m e n t sd e p o s i t e d
as f l u v i a lc h a n n e l - f i l l
d e p o s i t so ft h ep r o x i m a l
rock-record
and midfanportionsofHoloceneand
humid a l l u v i a l f a n c o m p l e x e s
B l i s s e n b a c h( 1 9 5 4 ) ,
andsheet-flood
a s d e s c r i b e db y
McGowen andGroat(1971),andRobinson
(1976)
Blue Mesa B a s a l t
"
Severalbasaltflowscropout
Mountain Mesa.
!these
t h e SpearsFormation
on Blue Mesa and D C r o s s
f l o w sd i s c o r d a n t l yo v e r l i e
a t thesouthernendofBlue
p r o g r e s s i v e l yy o u n g e rr o c k st ot h en o r t h .
Mountain Mesa t h ef l o w so v e r l i eC r e v a s s e
t u f f s of
Mesa and
On D Cross
Canyon s t r a t a .
103
Two flows are p r e s e n t on D Cross Mountain Mesa and a s
many as t h r e ef l o w s
f l o w sa v e r a g e
on B l u e Mesa.
may b ep r e s e n t
l e s s than50
Individual
f t ( 1 5 m ) t h i c k and e x h i b i t well-
developed v e r t i c a l c o l u m n a rj o i n t i n g .T y p i c a l l y ,
(0.3-3.0
m)-thickdark-yellowish-orange
t h eb u l k
( 1 0 YR 6/6) zoneof
is overlainbyblack
ashandvesicularbasaltbreccia
blockyweathering
a 1-10 f t
,
(Nl)
, dense, porphyritic basalt that comprises
of t h e u n i t .
?he b a s a l t s are d e n s e ,b l a c k
d o t t e dw i t hf a i n t - w h i t e
( N l ) , p r o p h y r i t i c , and
(N8) s p o t s on weathered surfaces.
, unal-
%e p h e n o c r y s t s are o r i e n t e d , l a t h s h a p e d , s u b h e d r a l
t e r e da n d e s i n e - l a b r a d o r i t e( 4 5 - 5 5 % )( P l a t e
a l b i t e a n dc a r l s b a dt w i n n i n g
20) t h a t e x h i b i t .
and r a r ez o n i n g ,e u h e d r a lt o
s u b h e d r a l ,e q u a n to l i v i n e( 2 0 - 2 5 % )c r y s t a l st h a ta l w a y sh a v e
a l t e r a t i o n rims ofreddish-brown
i d d i n g i s t e , and
( 1 0 R 4/6)
a n h e d r a tl os u b h e d r a pl y r o x e n ec r y s t a l s( 2 0 - 2 5 % ) .
p h e n o c r y s t s are surroundedby
smallfeldsparlathsandmicroli
and m a g n e t i t e V
. o l c a n i cg l a s s
o ft h eb a s a l t
thevolcanicneckwhichforms
vent.
a f e l t y groundmasscomposed
tes o f a u g i t e , o l i v i n e
is r a r e .
(?)
,
A c h e m i c a la n a l y s i s
on D Cross Mountain Mesa was
D Cross Mountain.
on B l u e Mesa was t h ep r o b l e m a t i c a l
On t h em e s a st h e
flows d i p 1-2
t h es o u r c eb u td i p ss t e e p e na b r u p t l yt o
(Plate 21).
of
i s g i v e n i n Table 1.
%e s o u r c e of t h ef l o w s
f o rt h ef l o w s
The
A smallsegment
0
The s o u r c e
Blue Mesa
r a d i a l l y awayfrom
9-10
0
n e a rt h e
vents
of a c o l l a p s e d l a v a t u b e on t h e
n o r t h face o f B l u e Mesa i s o r i e n t e d N 10'
E.
!
104
P l a t e 20.
Photomicrograph of t h i n - s e c t i o no fB l u e
Mesa
b a s a l t . The l a r g el a t hs h a p e dc r y s t a l sa r e
a n d e s i n e - l a b o r d o r i t e ,h i g hb i r e f r e n g e n c ec r y s t a l s
a r eo l i v i n e and p y r o x e n e . F e l t y groundmass i s
composed of f e l d s p a r s ,o l i v i n e ,p y r o x e n e
and
m a g n e t i t e( c r o s sN i c h o l s ,l o wp o w e r ) .
105
Plate 21.
Flows o f Blue Mesa b a s a l tc a p p i n g
D Cross
Mountain Mesa. Two flows, eachapproximately50
f t ( 1 5 m) t h i c kc a nb es e e n .
Notice how t h ed i p s
o f t h e flow r o c k si n c r e a s e (from l e f t to r i g h t )
n e a rt h e D Cross v e n t .
106
S e v e r a lb a s a l ts a m p l e sw e r ec o l l e c t e df o rr a d i o m e t r i c
d a t i n g ;n o n e ,h o w e v e r ,p r o v e da d e q u a t ef o ra n a l y s i s .S t r a t i g r a p h i c ,t o p o g r a p h i c ,a n dr e g i o n a lr e l a t i o n ss u g g e s tt h a tt h e
f l o w s a r e a p p r o x i m a t e l y 3-4 m.y.
t h a nt h ec o n g l o m e r a t eo f
r e l a t i o no f
28and33,
h a sb e e n
Rock Tank Canyon basedonthe
Red Lake f a u l t .
t h e two u n i t st ot h e
T.
3 N.
, R.
tilted tothe
The f l o w s are younger
old.
8 W.
, the
Miocene ( ? ) conglomerate
e a s t by movement a l o n g t h e f a u l t .
miles t o t h e
This same f a u l t is c o v e r e db yt h ef l o w ss e v e r a l
south
In S e c s .
.
In s u r r o u n d i n ga r e a s ,v o l c a n i cn e c k sw i t ha s s o c i a t e d
f l o w st h a t
are l i t h o l o g i c a l l y , s t r a t i g r a p h i c a l l y ,
g r a p h i c a l l y similar t o t h o s e o f t h e
h a v eb e e nd a t e da t
3.4-3.6m.y.
mun.,1980)and3.1
m.y.
D Cross Mountain a r e a
B.
B.P.
andtopo-
(C.
P.
C h a p i n ,o r a l
com-
(BachmanandMehnert,1978).
A similar a g e a p p e a r s l i k e l y f o r t h e
D Cross Mountain b a s a l t
flows.
QuaternarySystem
Pediment Gravels
Threegravelcoveredpedimentshavebeen
mapped i n t h e
, and Qg3. D i f f e r e n t i a t i o no f t h e
Q g l ’ Qg2
g r a v e l s is b a s e do ne l e v a t i o na n dd e g r e e
of i n d u r a t i o n .I n
s t u d y area:
g e n e r a l , t h e sedimentcover
, i s less than 1 0 f t ( 3 m ) t h i c k
and is composed o f p o o r l y s o r t e d g r a v e l
volcanicarenitesthat
and c r o s s - s t r a t i f i e d
are l o c a l l yl o o s e l yc e m e n t e db y
107
caliche.
These s e d i m e n t s were d e r i v e d from t h ee r o s i o no f
rest with
D a t i lv o l c a n i c si nt h es u r r o u n d i n gm o u n t a i n sa n d
strata.
a n g u l a r i t ya b o v eo l d e r
!the o l d e s t g r a v e l ,
which is a l s o t o p o g r a p h i c a l l y
h i g h e s t , i s north-slopingand
was d e p o s i t e d on a w i d e s p r e a d ,
3-4 m.y.-oldgeomorphicsurface.Remnantsof
covered surface o c c u ri nt h e
the
the gravel-
extreme s o u t h - c e n t r a lp o r t i o n
are a p p r o x i m a t e l y 200 f t ( 6 1 m) above
o ft h eq u a d r a n g l ea n d
thepresentdrainage.
An e x t e n s i v e n o r t h e a s t - s l o p i n g s u r f a c e
t h e l a t e r a l p l a n i n ga c t i o no f
was developedby
streams flowing a t a lower
e l e v a t i o nt h a nt h o s e
t h a t deposited the Q
g r a v e l s!.t h i s
gl
gravel-covered surface ( Q ) s l o p e st ot h en o r t h e a s t
away
92
from t h e Datil Mountainsand
is l e s s t h a n 1 0 0 f t ( 3 0 m )
h i g h e rt h a n
t h e p r e s e n td r a i n a g e .
t ot h o s eo f
Q
The g r a v e l sa r es i m i l a r
b u tc o n t a i n a l a r g e rp r o p o r t i o no fa n g u l a r ,
gl
b l a c k (N2) b a s a l t c l a s t s t h a t were d e r i v e dp r i n c i p a l l yf r o m
e r o s i o no f
t h e b a s a l tf l o w sc r o p p i n go u to n
the mesa s u r -
a north-
f a c e .C r o s s - s t r a t i f i c a t i o nm e a s u r e m e n t si n d i c a t e
e a s t p a l e o s l o p ed u r i n gd e p o s i t i o no ft h eg r a v e l s .
g r a v e ld e p o s i t
Qg2
is a p p r e c i a b l y t h i c k e r t h a n t h o s e o f e i t h e r
and may r e p r e s e n t a coalesced bajada complex
Q~~ or Q
93'
t h a t b u i l t o u t w a r df r o mt h em o u n t a i nf r o n t .
!the l o w e s t a n d m o s t e x t e n s i v e g r a v e l - c o v e r e d s u r f a c e
a few t e n s of f e e t a b o v et h ep r e s e n td r a i n a g e .
onwhich
thegravels
w e a k l yr e s i s t a n t
The s u r f a c e
accumulated is n o r t h - s l o p i n g
Baca andCrevasse
is
Canyon s t r a t a .
and c u t on
The most
108
i s i nt h ee a s t - c e n t r a lp o r t i o no ft h e
e x t e n s i v ee x p o s u r e
i s o n l y a few f e e t t h i c k i n
mapped area.Sedimentcover
most areas andcomposed
d o m i n a n t l y o f u n c o n s o l i d a t e ds a n d
and pebble s i z e v o l c a n i c c l a s t s .
The g r a v e l - c o v e r e ds u r f a c e sr a n g ei na g e
PliocenetoHoloceneand
were d e v e l o p e db yt h ea c t i o no f
l a t e r a l l yp l a n i n gs t r e a m sd u r i n g
base-level.
from l a t e s t
a step-like l o w e r i n go f
are t h e more
For t h i s r e a s o nt h eo l d e rs u r f a c e s
d i s s e c t e d and s t a n d a t a h i g h e r e l e v a t i o n .
Alluvium, Colluvium, Landslide, _
and
. Eolian Deposits
The e p h e m e r a lc r e e kb e d si nt h ea r e aa r ef l o o r e dw i t h
l o c a l l yd e r i v e dg r a v e l ,s a n da n d
mud.
Unconsolidatedsedi-
mentsdepositedalongthecourseofAlamocita
been mapped as:
p l a i nd e p o s i t s ;
Creek have
Q a l s ,r e c e n ts t r e a md e p o s i t s ;Q a l t ,f l o o d
are
and Qs, d u n ed e p o s i t s .Q a l ss e d i m e n t s
m o d e r a t e l yt op o o r l ys o r t e da n dc r u d e l yc r o s s - s t r a t i f i e d .
P e t r o l o g yo f
t h e d e p o s i t s r e f l e c t s t h el o c a lg e o l o g yo f
the
are
Alamocita Creek d r a i n a g eb a s i n .F l o o dp l a i nd e p o s i t s
poorlysorted
muds and s a n d s a n d , l o c a l l y , g r a v e l s w h i c h
Creek and i t s t r i b u t a r i e s .
form thebanksofAlamocita
C r o s s - s t r a t i f i e dd u n ed e p o s i t s ,f o r m e db y
t i o no fs a n d
blownfrom
form t h i c ka c c u m u l a t i o n s .
o fq u a r t zs a n da n dr e a c h
areas.
t h e accumula-
t h e bed of Alamocita Creek, l o c a l l y
The d u n e s a r e composed d o m i n a n t l y
30 f t ( 9 m ) i n h e i g h t i n
%e l a r g e rd u n e so c c u r
on t h es o u t hs i d eo f
some
the
109
c r e e k a s a r e s u l t of t h e p r e v a i l i n g n o r t h w e s t t o s o u t h e a s t
winds.
U n d i f f e r e n t i a t e dw a t e r - l a i ng r a v e l s ,s a n d s ,a n d
havebeen
muds
mapped a s Q a l .T h e s ed e p o s i t si n c l u d el o c a l l y
or a l l u v i a lf a n
d e v e l o p e d ,i s o l a t e dp e d i m e n tg r a v e l s
d e p o s i t s on BlueMesa,andslope-washcoveredareassuch
as
t h eC r e t a c e o u ss h a l ev a l l e y sn o r t ho fA l a m o c i t a
Colluvium (Qc) wasmapped
Creek.
o n l y where t a l u s a n do t h e r
were so t h i c k a s t o c o n c e a l
l o c a l l yd e r i v e dd e b r i s
the
u n d e r l y i n gr o c k .L a r g e ra r e a s . o fc o l l u v i u ma r ea s s o c i a t e d
w i t h t h e D Cross Mountainventand
Mesa and D CrossMountain
mapped a s Qls.
Two such
The l a r g e s tl a n d s l i d ef e a t u r eo c c u r s
Mesa.
on t h ee a s ts i d eo fB l u e
b a s a l th a v e
Blue
Mesa.
Landslideblockshavebeen
areas were d e l i n e a t e d .
t h e f l o w sc a p p i n g
There numerousblocksof
s l i d down t h e east s i d eo ft h e
mesa.
The b l o c k s
appear t o have s l i d a l o n gs t e e p l yi n c l i n e ds h a l eu n i t si n
t h e Baca Formation.
A zone ofjumbledDakotaSandstoneand
ChinleFormationinSec.
9,
T.
3 N.,
R.
8 W. h a sa l s ob e e n
mapped a s a l a n d s l i d e t e r r a i n .
I n t r u s i v e Focks
A s i n g l ev o l c a n i cn e c k ,
t h es t u d ya r e a .
D CrossMountain,
%e v e n tr o c k
wasmapped
in
a t D Cross Mountain i s a
b a s a l t i cv e n t a g g l o m e r a t et h a th a si n t r u d e di n t oC r e v a s s e
Canyon s t r a t a ( P l a t e 2 2 ) .
t h ei n t r u s i v er o c k ,
Due t ot h er e s i s t a n tn a t u r eo f
t h e neck now s t a n d s 300 f t ( 9 1 m ) above
P l a t e 22.
D Cross
Mountain.
Formerly
c a l l e d Turtle
Mountain. D Cross Mountain is a v o l c a n i cv e n t ,
is well developed i n t h el o w e r
c o l u m n a rj o i n t i n g
p a r to ft h ee x p o s u r e .
The v e n tr o c k i s cappedby
a s e r i e so ff l a tl y i n gl a v af l o w st h a ts o l i d i f i e d
i n a l a v a lake.
The "DX" v i s i b l e on t o po ft h e
mountain i s a n a t u r a lr o c kf o r m a t i o n .
111
lhe D Crossneck
t h ei n t r u d e ds t r a t a .
i s s e m i c i r c u l a ri n
f t ( 4 6 0 m) i n diameter.
p l a n andapproximately1500
Due t o
t h ea c c u m u l a t i o no fc o l l u v i u ma tt h eb a s eo ft h ec l i f f ,t h e
intrusivecontact
i s n o te x p o s e d .
Columnar j o i n t i n g is well d e v e l o p e dw i t h i nt h ei n t r u sion.
The j o i n t s a r e g e n e r a l l y v e r t i c a l . o r n e a r v e r t i c a l
t h e base of t h e e x p o s u r e , b u t f l a r e w i l d l y
at
from place t o
p l a c e .I nt h eu p p e rt h i r do ft h en e c k ,t h ec o o l i n gc o l u m n s
f l a t t e no u t
lhese
and a r eo v e r l a i nb yh o r i z o n t a ll a v a s .
a l a v a lake t h a t
flat-lyingbasaltrocksprobablyrepresent
s o l i d i f i e di nt h ev o l c a n i cv e n t .
M i n e r a l o g i c a l l yt h e
Mesa and D CrossMountain
similar t ot h ef l o w sc a p p i n gB l u e
Mesa.
is
D C r o s sM o u n t a i ni n t r u s i v er o c k
lhe rock i s , h o w e v e r ,m o r ev e s i c u l a ra n dc o n t a i n s
a b u n d a n tl a r g e
t o small x e n o l i t h so fs a n d s t o n e ,s h a l e ,a n d
v a r i o u s types of i g n e o u sr o c k s .
A p r o b a b l e , less w e l l - e x p o s e d , v e n t e x i s t s b e n e a t h t h e
b a s a l t flows on B l u e Mesa.
Spearstuffs
CrossMountain
Here t h e magma h a si n t r u d e d
a t a p p r o x i m a t e l yt h e
neck.
Mesa v e n t i n c l u d e :
same e l e v a t i o n as t h e D
C r i t e r i a for t h ee x i s t e n c eo ft h eB l u e
t h i c k e n i n g of t h el a v a
t i o n of t h e Spears t u f f s , a n dt h er a d i a l
away from t h es u s p e c t e dv e n ta r e a .
section, alterad i p s o fl a v af l o w s
lhe g e o m e t r yo ft h e
intrusioncannotbeascertained.
lhree small, i r r e g u l a ri n t r u s i o n sm e a s u r i n g
100 f t ( 3 0 m) i n diameter were mapped.
p l u g s are similar t o t h e
1)
less t h a n
Lithologically, t h e
CrossMountainventrock.
lhese
112
small i n t r u s i o n s p r o b a b l y r e p r e s e n t f i n g e r - l i k e i n t r u s i o n s
o f magma t h a t o r i g i n a t e d
from a b u r i e d magma chamber b u t
s o l i d i f i e db e f o r er e a c h i n gt h es u r f a c e .
I ns u r r o u n d i n ga r e a si n t r u s i o n sa n da s s o c i a t e df l o w
are r e l a t e d t o
r o c k st h a t
a t 3.4-3.6
havebeendated
commun.,
a widespreadgeomorphicsurface
m.y.
1980) and 3 . 1 m.y.
B.P.
B.P.
were a l s op r o b a b l y
t h i s p e r i o do fv o l c a n i ca c t i v i t y .
Two n o r t h w e s t - t r e n d i n g d i k e s
s i d eo f
crop o u t o n t h e s o u t h w e s t
These t a b u l a ri n t r u s i o n sc a n
D Cross Mountain.
t r a c e di n t e r m i t t e n t l y
Two miles ( 3 . 2 km) n o r t ho ft h e
q u a d r a n g l e ,o n e
be
f o r a t l e a s t 5 m i ( 8 km) a n dm a i n t a i n
a r e l a t i v e l yu n i f o r mt h i c k n e s so fb e t w e e n
m).
Chapin, o r a l
(BachmanandMehnert,
1 9 7 8 ) .V e n t sa n dp l u g si nt h es t u d ya r e a
emplacedduring
(C.
6-10 f t (1.8-3.0
D Cross Mountain
or b o t h o f t h e d i k e s t h i c k e n t o
l a r g e ,i r r e g u l a ri n t r u s i v e
body.
form a
The trace o ft h ed i k e s
only slightly deflected by topography;
is
a v e r y steep d i p t o
t h e east is i n d i c a t e d .
A l t e r a t i o na l o n gt h e
d i k e m a r g i n s i s minimal.Gener-.
a l l y , a t h i n ,r e d d i s h - o r a n g e
( 1 0 R 6/6)bakedzoneextends
a 1-2 i n .( 2 . 5 - 5
few i n c h e s i n t o t h e h o s t r o c k a n d
t h i c k ,b l a c k
d i k em a r g i n .
( N l ) g l a s s yc h i l l e dz o n e
The d i k er o c k
is developed a t t h e
i s n o n r e s i s t a n t to weathering
and forms a s l i g h t t o p o g r a p h i c d e p r e s s i o n a l o n g
The rock is s u g a r y w e a t h e r i n g
its t r a c e .
, aphanitic, olive green
, a n dp o r p h y r i t i c .I n
two
brown,pleochloric , e u h e d r a l b i o t i t e
( 5 GY 3/2)
cm)
t h i n - s e c t i o n se x a m i n e d ,
i s thedominantpheno-
a
113
cryst.
from 0 . 0 1 mm t o 1 mm i n
The b i o t i t ec r y s t a l sr a n g e
d i a m e t e r ,a r ef r e s ht o
s u b p a r a l l e lt ot h e
c r y s t a l se x h i b i t
s l i g h t l y a l t e r e d , and a r ea r r a n g e d
d i k e margins.
Many o f t h e b i o t i t e
rim.
a d a r k - r e da l t e r a t i o n
Opaque m i n e r a l s
comprise less t h a n 1%oftherock.
O t h e rp h e n o c r y s t si n
t h e r o c kh a v eb e e na l t e r e dt oc l a y
m i n e r a l s ( 7 ) and z e o l i t e s , or h a v eb e e nr e p l a c e db yc a l c i t e
and s i l i c a .
These a l t e r e dp h e n o c r y s t sa r ee u h e d r a lt o
subhedral b u t positiveidentificationcouldnotbe
made.
Based on t h e c r y s t a l f o r m , t h e y a r e s p e c u l a t i v e l y e i t h e r
h o r n b l e n d e or, p e r h a p s ,p y r o x e n e .l h ep h e n o c r y s t sa r es e t
i n a s i l i c i f i e d or z e o l i t i z e dm a t r i x .
originallybeen
The rock may have
a basalticandesite.
young as theCrevasse
The d i k e s c r o s s - c u t s t r a t a a s
Canyon F o r m a t i o n R
. e l a t i o n st op o s t - C r e v a s s e
a r eb a s e d
Canyon s t r a t a
on r e l a t i v er e l a t i o n st ot e c t o n i ce v e n t s .
dikescropoutadjacentto,
The two
of, the D
and on o p p o s i t e s i d e s
Cross f a u l t and a r e t h o u g h t t o
be r e p e a t e d p a r t s o f
a single
d i k et h a th a sb e e nc u tb yt h ed o w n - t o - t h e - e a s tf a u l t .
t h i s r e l a t i o n is c o r r e c t , t h e
Oligocene.
t h en o r t hf a c e
If
dikes are at least
as young a s
'Ihe d i k e s ,f u r t h e r m o r e ,a p p e a rt ob eo f f s e t
of Blue Mesa byMiocene
on
( ? ) movement along
t h e Red Lake f a u l t .
N o r t h - t r e n d i n g ,b a s a l t i ca n d e s i t e
P u e r t e c i t oa r e at h a ta r ea s s o c i a t e d
d i k e s i nt h eR i l e y -
w i t h RioGrande
are dated a t 24-25 m.y. o l d ( C . C h a p i n ,o r a l
A similarageappearslikelyforthe
rifting
commun.,
dikes inthe
1980).
D Cross
114
M o u n t a i na r e a .
Based on thecompositionandage
d i k e s , t h e y are t h o u g h tn o t
v e n t sa n da s s o c i a t e d
t o be g e n e t i c a l l y r e l a t e d t o t h e
flow r o c k so fB l u e
Mesa and D Cross
Mountain I b u t t o h a v e f o r m e d d u r i n g a n o l d e r e v e n t
related t oe x t r u s i o no ft h ep o s t - S p e a r sv o l c a n i c s
s o u t h e r n Datil Mountains.
of t h e
I
perhaps
of the
115
STRUCTURALGEOLOGY
The g e n e r a l s t r u c t u r e o f t h e
The c o n t i n u i t yo f
s o u t h w e s td i p p i n gh o m o c l i n e .
anticline the
andby
c r e s t ofwhich
a b r o a dn o r t h e a s t - o r i e n t e d
i s c u t by a m a j o r n o r t h e a s t are well
s t r i k i n gn o r m a lf a u l t .T e c t o n i ce v e n t st h a t
documented i nt h e
i
area i n c l u d e :
Range f a u l t i n g ,a n dt h e
the struc-
a s e r i e s o fn o r t h - n o r t h w e s t
t u r e i s , however,brokenby
t r e n d i n gn o r m a lf a u l t s
is a
D CrossMountainarea
Laramide f o l d i n g ,B a s i na n d
u p l i f t o ft h eC o l o r a d oP l a t e a u .
L i t t l e c a nb eg l e a n e dc o n c e r n i n gp r e - C r e t a c e o u st e c t o n -
ism i n t h e area.
However, there i s anangularunconformity
s e p a r a t i n g t h e Triassic ChinleFormationfrom
t h e Cretaceous
D a k o t aS a n d s t o n e R
. e g i o n a l l y t, h eC h i n l ep i n c h e so u t
a g a i n s tt h ee r o s i o n a ls u r f a c et ot h es o u t h .
The g e n t l e up-
l i f t and n o r t h w a r dt i l t i n go ft h eC h i n l ep r o b a b l yo c c u r r e d
d u r i n gt h eJ u r a s s i cP e r i o d .
B r o a d ,o p e n ,n o r t h e a s t - t r e n d i n ga n t i c l i n e s
c l i n e s are p r o m i n e n tf e a t u r e sn o r t ho ft h es t u d y
o ft h e
m o r ei m p r e s s i v es t r u c t u r e s ,t h e
and syn-
area.
One
Red Lake a n t i c l i n e ,
h a s a maximum width of 4 m i (6 km) a n dc a nb et r a c e ds o u t h -
ward f o r a minimum of10
m i ( 1 6 km) t o a p o i n tn e a r
abandoned INM Ranch h e a d q u a r t e r si n
W.
Sec. 21, T. 3 N.,
The c r e s t of t h e Red Lake a n t i c l i n e is c u t b yt h e
the
R. 8
Red
L a k e f a u l t which p a r t i a l l y m a s k s t h e a n t i c l i n a l s i g n a t u r e i n
t h e D Cross Mountainquadrangle.
116
The Red Lake a n t i c l i n e i s asymmetrical and southplunging.
s t r u c t u r e t r e n d s N 30'
The a x i s o ft h e
0
p l u n g e ss o u t h w a r da t
10
.
S t r a t aa tl e a s t
as young as
Crevasse Canyon a r ei n v o l v e di nt h ef o l d i n g .
on t h e w e s t e r n l i m b a r e 5-8
d i p sa s
much a s 4 7
0
0
Dips o fs t r a t a
t o t h e west.
These h i g h e r
Red L a k e f a u l t and d r a g
i s r e s p o n s i b l e for
along t h e down-to-the-eastnormalfault
t h eh i g h e r
Ihe e a s t e r n l i m b
t ot h ee a s t - s o u t h e a s t .
d i p s o c c u ri nc l o s ep r o x i m i t yt ot h e
E and
dips.
The nose of t h e Red Lake a n t i c l i n e i s b r o k e nb ys e v e r a l
small west-northwest-trending
h a v el o c a l l yb e e nd e f o r m e di n t o
and s y n c l i n e s .
tear f a u l t s and t h e s t r a t a
a s e r i e s of small a n t i c l i n e s
These s u b s i d i a r yf o l d si n v o l v eD a k o t a( m a i n
body) andTwowells
s t r a t a and were producedby
movement
a l o n gt h ef a u l t .F o l d i n go c c u r r e dd u r i n gt h eL a t eC r e t a c e o u s
t o e a r l y Eocene a s t h e
r e s u l t of n o r t h e a s t - d i r e c t e dc o m p r e s -
s i o n a lf o r c e sa s s o c i a t e dw i t ht h eL a r a m i d eo r o g e n y .
As many a s 20 s u b p a r a l l e ln o r t h w e s t - t r e n d i n gn o r m a l
f a u l t s were mapped i nt h e
The
D CrossMountainquadrangle.
faultsaremostlydown-to-the-eastin
a step-like f a s h i o n .
A few f a u l t s , howkver, a r e down-to-the-westandseveralhave
d i p s of less t h a n 70'.
andno
H o r s t and g r a b e ns t r u c t u r e s
are r a r e
reverse f a u l t i n g was d e m o n s t r a t e d .I ng e n e r a lt h e
faultblocks
are t i l t e d t o t h e e a s t - s o u t h e a s t
a few d e g r e e sg r e a t e rt h a nt h a to ft h er e g i o n a l
p l a c e m e n ta l o n gt h en o r m a lf a u l t s
a t a n g l e so n l y
dip.
Dis-
is g e n e r a l l y less t h a n 7 5
117
f t ( 2 3 m) and t h e f a u l t s c a n n o t b e t r a c e d l a t e r a l l y f o r
great distances.
movement is c o n c e n t r a t e d
Most o ft h ed o w n - t o - t h e - e a s t
The D Cross f a u l t t r e n d sn o r t h w e s t -
along D C r o s sf a u l t .
ward,has
a minimum of 7 m i (11 k m ) .
b et r a c e df o r
d i p s 80-85'
700 f t ( 2 1 3 m )
a maximum d i s p l a c e m e n to f
east.
t ot h e
, andcan
The f a u l tp l a n e
upper and lower
I nm o s ta r e a s
Crevasse Canyon s t r a t a a r e j u x t a p o s e d a c r o s s t h e f a u l t
p l a n e I. nt o p o g r a p h i c a l l yl o w e ra r e a sa l o n gA l a m o c i t a
Creek, exposedmiddleCrevasse
Canyon s t r a t a havebeen
dropped down a g a i n s t t h e Carthage Member of t h e Tres
Hermanos Sandstone.
The D C r o s s f a u l t c a n b e t r a c e d
c o r n e ro f
8 W.
t h e q u a d r a n g l ea s
from t h e n o r t h w e s t
f a r s o u t ha sS e c .
Canyon s t r a t a .
b e f o r eb e i n gl o s ti nC r e v a s s e
m u s t c o n t i n u es o u t h w a r db e c a u s ed i s p l a c e m e n t
f a u l t , on t h e n o r t hf a c eo f
fault,has
,
The f a u l t
area.
Blue Mesa, e a s t o ft h e
A large
Red L a k e
a similar s e n s ea n dm a g n i t u d eo fd i s p l a c e m e n t
it p r o b a b l y is a no f f - s e ts e g m e n to ft h e
and is c o n c e a l e d
beneathQuaternarygravelsinthevalleyeastof
D C r o s sf a u l t
a s theSpearsFormation.Miocene
11 and 1 4 1 T.
3 N.
, R.
and
D Cross f a u l t .
This unnamed f a u l t c o n t i n u e s s o u t h e a s t w a r d
Faultsinthe
R.
on t h e f a u l t i s
500 f t ( 1 5 2 m ) i n t h a t
s t i l l on t h eo r d e ro f
2 N.
6, T.
B l u e Mesa.
zone o f f s e t s t r a t a a s
young
( ? ) c o n g l o m e r a t e si nS e c s .
8 W. p o s t - d a t e movement a l o n gs e v e r a l
n o r t h w e s t - t r e n d i n gf a u l t sT. h e r e f o r et,h n
e orthwestt r e n d i n g f a u l t s are o fl a t eO l i g o c e n et o
Mioceneage.
This
118
s u g g e s t s a BasinandRange
o r i g i nf o rt h ef a u l t s ,a l t h o u g h
t h ef a u l t - z o n e - t r e n d
is p a r a l l e lt o
t h e ZuniMountains.
The o r i e n t a t i . o no f
b e e ni n
Laramide s t r u c t u r e s o f
t h e f a u l t s may have
part controlledbyolderplanes
of weakness.
were mapped i n t h e
S e v e r a ln o r t h e a s t - t r e n d i n gf a u l t s
cut
s o u t h e a s t e r np o r t i o no ft h es t u d ya r e a .T h e s ef a u l t s
t h e Spears t u f f .
Due t ot h ec h a o t i cd i p so ft h eS p e a r s
s t r a t a and t h e l a c k o f marker b e d s , r e l a t i v e d i s p l a c e m e n t s
and many s m a l l f a u l t s p r o b a b l y
c o u l dn o tb ea s c e r t a i n e d
exist i n the tuffsection
which were n o t mapped.
?he Red Lake f a u l t is a p r o m i n e n tn o r t h e a s t - t r e n d i n g ,
be t r a c e d
h i g ha n g l e ,d o w n - t o - t h e - e a s tn o r m a lf a u l tt h a tc a n
t h r o u g h o u tt h es t u d y
v a r yf r o m
70
0
s o u t h w e s ts i d e
area.
i nS e c .
1 0 , T.
of Blue Mesa.
3 N.,
R. 8 W. t o 85
Creek, Chinle
Canyon s t r a t a
s t r a t a h a v eb e e nj u x t a p o s e da g a i n s tC r e v a s s e
Red Lake f a u l t .I nt h en o r t h w e s t
quarter o f Sec. 33, T. 3 N.
, R.
8 W., t h e f a u l t
west s i d eo fB l u e
Mesa a n de x t e n d s
limit o ft h es t u d ya r e a .L o c a l l y ,
f a u l t is c o n c e a l e d b y t h e b a s a l t f l o w s t h a t c a p t h e
The e a s t e r ns e g m e n t
splits i n t o
One s e g m e n tc o n t i n u e st ot h es o u t h w e s t
where i t c u t s a c r o s s t h e
beyond t h es o u t h e r n
Red
or i s d i s t r i b u t e d i n
s e v e r a lf a u l ts p l a y s .N o r t ho fA l a m o c i t a
two majorsegments.
on t h e
Displacementalongthe
a s i n g l ef a u l tp l a n e ,
b y movement a l o n gt h e
0
1200 f t (365 m ) and i s e i t h e r con-
Lake f a u l t i s morethan
c e n t r a t e da l o n g
plane
Dip a n g l e s o f t h e f a u l t
this
mesa.
of t h e Red L a k e f a u l t i s c o n c e a l e d
119
beneathQuaternarygravelsinthevalleyeastof
B l u e Mesa
and it is n o te x p o s e ds o u t ho f
R.
Sec. 33, T. 3 N . ,
Drag on t h e downthrownblockofthe
l o c a l l yt i l t e dt h es t r a t aa s
e v e r ,d e c r e a s er a p i d l y
Red Lake f a u l t h a s
much a s 90
awayfrom
8 W.
0
.
The d i p s , how-
t h e f a u l t p l a n e and s t r a t a
w i t h i n 0.5 m i ( 0 . 8 km) o f t h e f a u l t a p p e a rt ob eu n a f f e c t e d
b yt h e
Mesa is a f a u l t - b o u n db l o c kt h a th a s
movement.Blue
beencaughtupbetween
Lake f a u l t .
t h e twomajorsegments
o f t h e Red
The e n t i r em o u n t a i nh a sb e e nt i l t e d ,
30-35
p e r h a p sr o t a t e d ,
0
and
t ot h ee a s t - s o u t h e a s t .
S t r a t a as young as t h e Miocene ( ? ) conglomerateof
Tank Canyon a r e c u t b y t h e
b a s a l tf l o w so n
Red L a k e f a u l t ; t h e
B l u e Mesa o v e r l i e t h e
t h e r e f o r ey o u n g e r .
Rack
3-4 m.y.-old
f a u l t t r a c e , and a r e
Thus t h e l a t e s t movement a l o n gt h e
Red
L a k e f a u l t is o f Miocene or P l i o c e n ea g e .
An unusual s t r u c t u r e o c c u r s i n t h e
m a t e l y 1 m i ( 1 . 6 km) s o u t ho ft h e
Spears t u f fa p p r o x i -
Fred MartinRanch.
e a s t side of Dog S p r i n g sC a n y o n ,t h et u f f sh a v e
much as 80'
a n df o l d i n go ft h e
dips of a s
a 180°, 0.3 m i ( 0 . 5
andhavebeenfoldedinto
km)-diameter semicircular arc.
On t h e
The f a u l t i n g , f r a c t u r i n g ,
Spears may b e r e l a t e d t o c o l l a p s e ,
s t r a t a i n t o a d e p l e t e d magma
s u b s i d e n c eo ft h eo v e r l y i n g
chamber from w h i c ht h e
or
t u f f s emanated.
However , n oc a u l d r o n
s t r u c t u r eh a sb e e nr e c o g n i z e d .
'Ihe C o l o r a d oP l a t e a u
c r u s t a lb l o c kt h a t
d i a m e t e r( K i n g ,1 9 7 7 ) .
is a h i g h s t a n d i n g , d i s s e c t e d
measures n e a r l y 500 m i ( 8 0 0 km) i n
Uplift a l o n gt h em a r g i n so f
the
120
P l a t e a u ,b e g i n n i n gi nt h ee a r l y
Miocene(ChapinandSeager,
flextures t h a t
1 9 7 5 ) ,h a sb e e nd o m i n a n t l ya l o n gm o n o c l i n a l
may i n p a r t r e f l e c t o l d e r c r u s t a l w e a k n e s s e s .
The D Cross a r e a o c c u p i e s
margin of t h e p l a t e a u .
b e e na f f e c t e d
In t h e s t u d y a r e a , s t r a t a t h a t h a v e
by Laramide andBasinand
e v e n t sd i pb e t w e e n
e r a t eo f
a p o r t i o no ft h es o u t h e a s t e r n
10-19
0
Range t e c t o n i c
t ot h es o u t h w e s t .
Ihe conglom-
Rock Tank Canyon (Miocene 7 ) p o s t - d a t e s
e a r l i e rd e f o r m a t i o ne v e n t s ,b u t
is t i l t e d a s
these
much a s 8'
to
t h e s o u t h .T i l t i n go ft h e s es t r a t ar e p r e s e n tt h er i s i n go f
t h e C o l o r a d oP l a t e a u .M a s s i n g i l l( 1 9 7 9 )h a sr e p o r t e d7 0 0
f t
(213 m ) o fC o l o r a d oP l a t e a u - a s s o c i a t e du p l i f ti nt h eR i l e y P u e r t e c i t oa r e as i n c et h eP l i o c e n e
t h ee l e v a t i o no f
(3-4 m.y.
B.P.)
basedon
a r e g i o n a lg e o m o r p h i cs u r f a c e .U p l i f t
along t h e m a r g i n s o f
t h e P l a t e a u may s t i l l b e a c t i v e .
121
GEOMORPHOLOGY
Alamocita Creek i s a l a r g ee a s t - f l o w i n ge p h e m e r a l
stream which c u t s a c r o s s
the s t r u c t u r a lf a b r i co ft h e
D
C r o s sM o u n t a i nq u a d r a n g l e F
. i e l de v i d e n c es u g g e s t st h e
s t r e a m was s u p e r p o s e do n t o
c u t t i n go fo v e r
mwn-
t h e u n d e r l y i n gs t r u c t u r e s .
2000 f t (610 m) i nt h ep a s t
few m i l l i o n
yearshasbeenepisoidic,oscillatingbetweenperiodsof
base-levelstability
and p e r i o d so fr a p i dd o w n c u t t i n g .
lhree pediment surfaces were f o r m e dd u r i n gp e r i o d s
of
temporarystabilityofthelocalbase-levelbylaterally
p l a n i n gt r i b u t a r i e so ft h e
master stream.
covered surfaces a r e mapped,from
mese g r a v e l -
o l d e s tt oy o u n g e s t :
Qgl,
was n o t mapped b u t i s
A fourth,oldersurface
and Q
93'
d e f i n e d by t h e d i s t r i b u t i o n of b a s a l t f l o w s
Qg2r
on B l u e Mesa and
and Q
surfaces s l o p e
Qgl
93
100 f t
from t h eG a l l i n a sM o u n t a i n sa t
Mesa.
on D CrossMountain
g e n t l yt ot h en o r t h
( 3 0 m) per mile andweregradedtoAlamocita
flowed a t a h i g h e re l e v a t i o n .
eastward awayfrom
The Q g 2 s u r f a c es l o p e s
B l u e Mesa and was c u t t o g r a d e t o
way b yh e a d w a r de r o s i o ni n t o
s u r f a c e , i f t r a c e dt o
a
of Alamocita Creek t h a t worked i t s
n o r t h - o r i e n t e dt r i b u t a r y
e f f e c t t ot h i s
C r e e k when it
Rock Tank Canyon.
This
t h e s o u t h beyond t h er e a d j u s t m e n t
sidestream, m e r g e sw i t ht h e
surface.
gl
Alamocita Creek i s c u r r e n t l y , i n a d e g r a d a t i o n a l p h a s e a n d
Q
r e c e n te r o s i o nh a sr e s u l t e di nd i s s e c t i o no ft h eo l d e r
g e o m o r p h i cs u r f a c e s .
122
ECONOMIC GEOLOGY
Co a 1
is w i t h i n t h e Datil
2
2
765 m i (1958 km ) i n
The D CrossMountainquadrangle
M o u n t a i nc o a lf i e l dt h a tc o v e r s
Valencia c o u n t i e s , New Mexico ( F i g u r e
Socorro, Catron,and
11). No m i n e sa r ep r e s e n t l yo p e r a t i n gw i t h i nt h e
field.
F i v eu n d e r g r o u n dm i n e so p e r a t e ds p o r a d i c a l l yb e t w e e n
time more t h a n 9 0 0 t o n s
early1900'sand1949duringwhich
were removed.
o fc o a l
morethan
the
Read and o t h e r s ( 1 9 5 0 )e s t i m a t e dt h a t
a billiontonsofreservesexistin
the field.
New MexicoBureau
Recentexploratorydrillingbythe
of
MinesandMineralResourcessuggeststhatcommercialcoal
d e p o s i t sa r ep r e s e n t
i n t h e Datil M o u n t a i nc o a lf i e l d( F r o s t
and o t h e r s , 1 9 7 9 ) .
Coalseams
i nt h e
Datil Mountain f i e l d a v e r a g e l e s s
t h a n 2 f t ( 6 1 cm) t h i c kb u tr a n g e
thickness.
The C o a l - b e a r i n gi n t e r v a lo c c u r si nt h el o w e r
2 0 0 f t ( 6 0 m ) o ft h eC r e v a s s e
I
Member ? )
.
up t o 5 f t (1.5 m) i n
Canyon Formation(Dilco
!the t h i c k e r s e a m sa r e ,h o w e v e r ,c o n f i n e dt o
a
zone w i t h i n 6 0 f t (18 m) above t h e t o p of t h e Gallup
Sandstone.
I nt h e
D CrossMountainquadranglethe
t h i c k e s t seam is
a p p r o x i m a t e l y 2 f t ( 6 0 cm) t h i c k a n do c c u r si nt h el o w e r
f t (1.5 m) of t h eC r e v a s s e
Canyon Formation ( P l a t e 2 3 ) .
This seam i s p r o b a b l yc o r r e l a t i v ew i t ht h e
W i n c h e s t e r( 1 9 2 0 )
mapped i nt h eP a s t u r e
seam t h a t
Canyon andWild
5
123
MEXICO
COAL FIELD
0
D CROSS MT.
QUADRANGLE
10 mi
Figure 11. Map showing the location and
extent of the Datil Mountain coal field.
124
P l a t e 23.Coal
seam a tt h eb a s eo f
t h e Crevasse Canyon
Formation.
This seam o c c u r sw i t h i n
a few f e e t
abovetheGallupSandstoneandcan
be t r a c e d
a l m o s tc o n t i n u o u s l yi n t ot h eP a s t u r e
Canyonand
Wild Horse Mesa q u a d r a n g l e s .
The seam is 2 f t
( 6 0 cm) t h i c k .
Dark s h a l eu n i t
a t b a s eo f
p h o t o g r a p hr e p r e s e n t sc o a s t a lm a r s hd e p o s i t s .
125
Horse Canyon quadrangleandthe
BureauofMines
seam coredby
t h e New Mexico
and M i n e r a lR e s o u r c e si nt h eP u e b l oV i e j o
Mesa and Wild Horse Canyon q u a d r a n g l e s( F r o s t
1979).
Numerous t h i nc o a l
and o t h e r s ,
seams t h a t d o n o th a v eg r e a t
l a t e r a l e x t e n to c c u rs t r a t i g r a p h i c a l l yh i g h e ri nt h e
Crevasse Canyon Formation.
i n both
Coals i n t h e D CrossMountainareaaccumulated
c o a s t a lm a r s h
and i n t e r d i s t r i b u t a r y swamps on a low-lying
c o a s t a lp l a i nd u r i n g
%e t h i c k e r
a m a j o rm a r i n er e g r e s s i o n .
c o a l seams a r e c l o s e l y a s s o c i a t e d w i t h c o a s t a l s a n d s t o n e
bodies,theyarelaterallycontinuous,
and c o n t a i n b r a c k i s h
w a t e rC l a s s o p o l l i sp o l l e n .M a n g r o v e - l i k er o o tc a s t s
monlyextendfrom
t h e c o a lh o r i z o ni n t ot h eu n d e r l y i n g
Gallup Sandstone.
similar t o t h e
com-
These c o a l sa c c u m u l a t e di na ne n v i r o n m e n t
Dismal Swamp o f N o r t hC a r o l i n aa n dV i r g i n i a .
Accumulations of mangrove-peat
swamps above marine sand-
b o d i e s are well known from c o a s t a l swamps o fs o u t h e a s t e r n
Florida(Teichmullerand
Teichmuller
, 1975)
.
C o a l sh i g h e ri nt h es t r a t i g r a p h i cs e c t i o na r e
c l o s e l y related t of l u v i a l .s a n d s t o n eb o d i e s .
As a r e s u l t o f
t h e l a t e r a l m i g r a t i o no ft h es t r e a mc h a n n e l s
f l o o d i n g ,t h e s ec o a l
seams a r e t h i n
andoverbank
and d i s c o n t i n u o u s .
Similardepositshavebeendocumentedfrom
River d e l t a p l a i n (Gould andMorgan,
more
t h e Mississippi
1962).
The D C r o s s M o u n t a i n c o a l s a r e c l a s s i f i e d a s h i g h v o l a t i l e C bituminous.
of t h e s e m i s p l i n t v a r i e t y
On a " f r e s h " surface, t h e c o a l sa r e
and c l e a t f a c e s a r e
well
126
developed.
me
face c l e a t s s t r i k e N 25'
c l e a t s s t r i k e N 70'
m i n e r a l i z a t i o na l o n g
E.
w
and t h e b u t t
On t h e o u t c r o p ,s e c o n d a r y
t h e c l e a t s i s r a r e ,a l t h o u g hp y r i t e
samples ( F r o s t and o t h e r s ,
c r y s t a l s a r e common i n c o r e d
1979).
T r a n s p a r e n ta t t r i t u s
e n t (Plate 24).
is t h ed o m i n a n tm a c e r a lc o n s t i t u -
Antraxylonandopaque
a t t r i t u sa r e
common
and f u s a i n is r a r e .C l a y ,c a l c i u mc a r b o n a t e ,a n ds i l i c a
o c c u ra l o n gm i c r o f r a c t u r e s
Most s a m p l e sa l s oc o n t a i n
and a s v o i d - f i l l i n g p r e c i p i t a n t s .
windblown
(?)
q u a r t z g r a i n s .I n
a few i n t e r f l u v i a l c o a l s , q u a r t z g r a i n s c o m p r i s e a s
much a s
4 0 % o ft h er o c kv o l u m e .C o r e ds a m p l e sy i e l dc a l o r i m e t r i c
v a l u e sr a n g i n gf r o m
1 1 , 7 0 0 t o1 2 , 6 0 0
B.T.U.
(Table 2); a s h
is
Sulfur
( 9 - 1 6 % ) and s u l f u r ( l e s s t h a n 1%)
c o n t e n t is low.
( F r o s t and
m o s tf r e q u e n t l ye n c o u n t e r e di no r g a n i cf o r m
others, 1979).
The lowercoal
seam i n t h e
D C r o s s Moun t a i n area would
mined
appeartobethickenoughandcontinuousenoughtobe
c o m m e r c i a l l yS
. e v e r a fl a c t o r s h, o w e v e r ,
limit t h e f e a s i -
b i l i t y of economicmining
D CrossMountain
of c o a li nt h e
include:
q u a d r a n g l eU. n f a v o r a b lceo n d i t i o n s
(1) s t r u c t u r a l
c o m p l i c a t i o n s ; ( 2 ) ruggedtopography;
( 3 ) l i m i t e da c c e s s ;
( 4 ) natureandthicknessofoverburden:and
(5) lack of
l o c a l market.
Many of t h e s e l i m i t a t i o n s d o n o t a p p l y t o
a r e a ss u r r o u n d i n gt h es t u d y' a r e a
whichcoalpossiblycould
( e . 9 . Red L a k e V a l l e y )i n
be commerciallymined.
P l a t e 24.
Photomicrograph o f c o atlh i n - s e c t i o n .
Large
y e l l o w and redfragments
are a n t h r a x y l o n ;s m a l l
y e l l o w and r e dc o n s t i t u e n t sa r et r a n s p a r e n t
a t t r i t u s ; b l a c km a t e r i a l i s opaque matter and
w h i t ea r e a sa r eq u a r t zg r a i n s .
128
TABLE 2
Coal A n a l y s e s from t h e D a t i l M o u n t a i n F i e l d
New Mexico
Vol.
M
A sohi s t .
~
I
I1
I11
Iv
BTU
S uFl.fCu .r
Type
~~
0.6
16.0
325. 7. 8
48
1.4
16.4
40.0
42
2.5
9.6
401. 5. 0
4.1
8.9
8.4
12,238
C
11,725
C
47
12,646
C
40.5
1.3
46
12,017
C
32.7
30.4
1.9
27
11,621
W
14.3
23.2
300. 4. 9
33
11,642
W
16.7
36.6
20.3
4.3
22
9,821
W
11.9
30.0
20 .86. 4
21
10,467
19.0
14.2
30.9
36
10,740
w
w
9.1
12.9
305. 4. 3
43
11,951
W
7.6
40.3
20.4
5.9
26
11,672
w
13.6
9.8
30 .53. 1
41
11,591
W
25.9
9.1
30.4
0.3
34
7,430
W
9.1
11.1
307. 3. 2
43
9,120
W
NA
12.2
40.9
0.5
47
10,030
W
NA
NA
46.6
53
0.6
11,430
w
6.5
7.1
34.5
52
0.5
11,990
w
5.3
7.2
34.9
53
0.5
12,150
w
0.8
0.5
129
V
..
.
F C
Sulfur
BTU
7.6
36.9
56
0.5
12,820
W
NA
NA
39.9
60
0.6
13,870
W
18.5
10.8
31.7
0.4
39
8,480
W
12.6
11.6
34.0
42
0.5
9,090
W
NA
13.2
38.9
48
0.5
10,400
W
NA
NA
44.8
55
0.6
11,990
w
NA
11,555
M
Moist.
Ash
NA
Vol
5 4 6.63 2 . 0 6 . 4
IFrostandothers,
1979; a s receivedbases
11
Massingill, 1979;
I11
CampbellandClark,
IV
Campbell, 1 9 1 2
V
TabetandFrost,
-
BTU, dry mineralmatterfree
1915
1978
C
core sample
W - weathered surface or mine sample
M - mine sample
TYPE
130
Uranium
in
The Baca Formation i s a well known uraniumhostrock
west-central
New Mexicoand
cropsoutextensivelyinthe
CrossMountainquadrangle.
l o c a t e d on t h e n o r t h
A smalluraniumprospect
D
is
face o f B l u e Mesa i n t h e " t r a n s i t i o n
zone"betweenCrevasse
Canyon and Baca s t r a t a .
o c c u r sn e a rt h ei n t e r s e c t i o no ft h e
D Crossand
The p r o s p e c t
Red L a k e
f a u l t s and it i s n o t known i f t h e anomaly was a s s o c i a t e d
w i t h these f a u l t s or i f it is s t r a t i g r a p h i c a l l y c o n t r o l l e d .
However,uranium
p r o s p e c t s west o f t h e s t u d y area i n t h e
Fed
B a s i n d i s t r i c t havebeencenteredontheBaca-Crevasse
Canyon " t r a n s i t i o n zone .'I
W i t h i nt h e
s t u d y area t h e Baca F o r m a t i o na p p e a r st o
The s a n d s t o n eb o d i e s
a p o t e n t i a lu r a n i u mh o s tr o c k .
fluvial origin,they
be
are o f
resemble o t h e r h o s t r o c k s o f t h e
a b l e a c h e dw h i t ec o l o r
C o l o r a d oP l a t e a ur e g i o na n dt h e yh a v e
which is o f t e na s s o c i a t e dw i t hu r a n i u mm i n e r a l i z a t i o n .
The
t h i c k p i l e o f s i l i c i c t u f f si nt h eG a l l i n a sM o u n t a i n sc o u l d
p r o v i d e a s o u r c eo fu r a n i u m .U n f o r t u n a t e l y ,o r g a n i cd e b r i s
i s s c a r c ew i t h i ne x p o s e d
Baca c h a n n e ls a n d s t o n e s .
O i l and Gas
Wells ( 1 9 1 9 ) ,W i n c h e s t e r
d i s c u s s e dt h eo i l
area.
( 1 9 2 0 ) , and Foster(1964)have
and g a s p o t e n t i a l
They c o n c l u d e dt h a t
of t h e D CrossMountain
structural traps involving
Pennsylvanian or P e r m i a nc a r b o n a t e s
or C r e t a c e o u ss a n d s t o n e s
131
had p o t e n t i a l as o i l and g a sr e s e r v o i r s .S e v e r a l
d r i l l e dp r i o r
t o 1 9 6 4i nt h ev i c i n i t y
d i dn o td e t e c ts i g n i f i c a n t
(
Foster, 1964)
.
o i l wells
of D Cross Mountain
shows o f e i t h e r o i l or g a s
132
SUMMARY OF GEOLOGIC HISTORY
Red s h a l e s and s a n d s t o n e s o f theChinleFormati'
on
accumulated on a n e x t e n s i v e l o w - l y i n g c o a s t a l p l a i n
meandering stream complexduringthe
Upper Triassic.
were s u b sequent:1y
J u r a s s i cs t r a t a ,i fd e p o s i t e di nt h ea r e a ,
e r o d e dd u et o
in a
u p l i f t oftheMogollonHighlandsandnorth-
n o r t h w e s tt i l t i n go ft h ea r e a .
For most o f t h e Lower C r e t a c e o u st h ea r e ar e m a i n e di n
a ne r o s i o n a l
s t a t e d u r i n gw h i c hl a t e r a l l yp l a n i n g
streams
b e v e l e dt h ea r e aa n dd e p o s i t e dt h eb a s a lD a k o t aS a n d s t o n e .
R e g i o n a ls u b s i d e n c ed u r i n gt h eC o n i a c i a nb r o u g h te n c r o a c h m e n to f
t h e m i d - c o n t i n e n tC r e t a c e o u ss e a w a yi n t ot h e
embaymentfrom
Acoma
t h es o u t h e a s t .
For t h er e m a i n d e r
of t h eC r e t a c e o u s ,t h e
area f l u c t u -
ated b e t w e e np a r a l i ca n dc o a s t a ln o n - m a r i n ee n v i r o n m e n t s .
lhe oscillatorynatureoftheshoreline
was t h e r e s u l t o fa n
i n t e r p l a yo fs p o r a d i cu p l i f ti nt h eC o r d i l l e r a nh i g h l a n d s
As a r e s u l t ,
a n ds l o ws u b s i d e n c eo ft h ed e p o s i t i o n a lb a s i n .
a complexsequence
of d a r k o f f s h o r e m a r i n e
Mancos S h a l e i n t e r f i n g e r
muds o f t h e
t o t h e west w i t h c o a s t a l
and
muds , and paludal. c o a l s o f t h e D a k o t a ,
fluvialsandsand
Tses Hermanos, Gallup, andCrevasse
Canyon Formations.
I
Near t h e end of t h eC r e t a c e o u s ,n o r t h e a s t - d i r e c t e d
c o m p r e s s i o n a lf o r c e sa s s o c i a t e dw i t ht h e
produced a s e r i e s ofbroadopen
Laramide orogeny
f o l d s and u p l i f t e d b l o c k s
s u c h as t h e Zuni"MountdinsandMogollonHighlands,and
1
i
I
133
resulted i n t h ef i n a le a s t w a r dr e g r e s s i o n
from t h e a r e a .
Pebble c o n g l o m e r a t e sa n da r k o s i cs a n d s '
were t r a n s p o r t e dt ot h e
erodedfromtheZuniMountains
s o u t h e a s ti n
a f l u v i a lc h a n n e l - f l o o d p l a i n
a c c u m u l a t e di n
f o rtm
h ei n g
of t h e marine seas
a west-trending
complexand
, elongated
structural basin
Eocene Baca Formation.
I
a
D e p o s i t i o no ft h e
Baca Formation was followedby
I
p e r i o d of e r o s i o n b e f o r e a t h i c k c o v e r o f v o l c a n i c a n d
v o l c a n i c l a s t i cr o c k ss p r e a do v e r
t h e a r e ad u r i i gt h e
t u f f s , and
O l i g o c e n e .L i t h i c - c r y s t a la n dc r y s t a l - l i t h i c
d e b r i s flows o ft h eS p e a r sF o r m a t i o n
were d e r i v e d froman
of t h e D
e r u p t i v ec e n t e rl o c a t e da l o n gt h es o u t h e r nb o u n d a r y
C r o s sM o u n t a i nq u a d r a n g l e .E r u p t i o no ft h et u f f s
l o w e db yt h ee x t r u s i o n
was f o l -
of a t h i c k p i l e o f a s h - f l o w
tuffs
from o t h e r v o l c a n i c c e n t e r s , i n t r u s i o n o f b a s a l t i c a n d e s i t e
d i k e s a n dn o r m a fl a u l t i n g .
The conglomerate of Rock Tank
Canyon (Miocene ? ) was d e r i v e d p r i n c i p a l l y f r o m e r o s i o n o f
Spears t u f f upon c e s s a t i o n o f v o l c a n i s m
a na l l u v i a lf a n
and was d e p o s i t e d i n
complex thatextendednorthwardfromthe
G a l i i n a sM o u n t a i n s .
Uplift o ft h eC o l o r a d o
P l a t e a u , b e g i n n i n gi nt h ee a r l y
t o m i d d l e Miocene, t i l t e d a l l o l d e r s t r a t a
t h es o u t h .
a s much a s 8'
to
East-west o r i e n t e de x t e n s i o n a lf o r c e sd u r i n gt h e
l a t e s t Miocene t oP l i o c e n e ,p e r h a p sr e l a t e dt or e n e w e do p e n ing of t h e Rio Grande r i f t r e s u l t e d i n t h e f o r m a t i o n
largedown-to-the-eastnormal
(365 m) o fd i s p l a c e m e n t .
of a
f a u l t with as much as 1 2 0 0 f t
134
V o l c a n i cn e c k sa n dp l u g sc r o p p i n go u to n
Mountainand
D Cross
B l u e Mesa were e m p l a c e dd u r i n gt h e
Late
T e r t i a r yD
. u r i n gt h eP l e i s t o c e n e A
, l a m o c i t aC r e e kb e g a n
downcuttingand
was superposed across t h e s t r u c t u r a l g r a i n
o f t h ea r e a .D u r i n gp e r i o d s
o f b a s e - l e v e ls t a b i l i t y ,p e d i -
ment and terrace s u r f a c e s were c o n s t r u c t e d b y l a t e r a l l y
p l a n i n gt r i b u t a r i e s
of t h em a s t e rs t r e a m .
p h y s i o g r a p h yo ft h ea r e a
b a s el e v e l
The p r e s e n t
i s r e l a t e d t o c o n t i n u e dl o w e r i n go f
and i n c i s i o n o f s t r e a m s i n t o
sequence of s e d i m e n t s a n d v o l c a n i c r o c k s .
t h e complexly f a u l t e d
135
REFERENCES C I T E D
A l l e n , J. R.
1 9 6 4 ,S t u d i e si nf l u v i a t i l es e d i m e n t a t i o n :
L.,
s i x cyclothemsfromthe
Lower Old Red S a n d s t o n e , Anglo-
Welsh B a s i nS
: e d .v, o l3. ,
A l l e n , J. R.
,
L.
1965, Late Q u a t e r n a r yN i g e rd e l t a
a s s o c i a t e da r e a s :
Bull.,
Am.
49, no.5,
VOl.
, and
A l l e n , J. E.
p. 163-198.
ASSOC.
and
P e t r o l e u mG e o l o g i s t
p . 547-600.
of F o r t
1 9 5 4 ,M i n e r a lr e s o u r c e s
B a l k , R.,
New
DefianceandTohachiQuandrangles,Arizonaand
Mexico:
New Mexico BureauofMinesandMineral
R e s o u r c e s , B u l l . 36,192
p.
, andMehnert,
1978, New K-Ar
d a t e s and
t h e l a t e P l i o c e n et oH o l o c e n eg e o m o r p h i ch i s t o r y
of the
Bachman, G. 0.
H.
New Mexico:
c e n t r a l Rio Granderegion,
American B u l l .
Bernard, H. A.
LeBlanc,
, vol.
, Majors, C.
R. J. , Sr .,
-A
east Texas
H.,
Geol. SOC.
85, p . 283-292.
F.
,
Jr.
,
P a r r o t t , B.
S.
, and
1970,RecentsedimentsofSouth-
fieldguide
t o t h eB r a z o sa l l u v i u ma n d
deltaplains
and t h eG a l v e s t o nb a r r i e ri s l a n dc o m p l e x :
TexasBureau
of Econ. Geology,Guidebook
11, 1 6 p .
, and
r e p r i n ta p p e n d .
B l i s s e n b a c h , E.
, 1954,Geology
r e g i o n sG
: eol.
B u l l , W. B.
,
of a l l u v i a lf a n si ns e m i - a r i d
SOC. America B u l l . ,
v o l 6. 5 ,
p. 175-190
in
1 9 7 2 ,R e c o g n i t i o no fa l l u v i a lf a nd e p o s i t s
-
t h e s t r a t i g r a p h i c r e c o r d ; i n R e c o g n i t i o n of Ancient
SedimentaryEnvironments,
J. K.
Rigbyand
W.
K.
Hamblin
1 36
eds.:
SOC. = o nP
. aleontologist
pub.no.16,
Campbell, M.
and M i n e r a l o g i s st p e c .
p. 63-83.
samples from v a r i o u s
1 9 1 2 ,A n a l y s e so fc o a l
R.,
f i e l d s i n t h e U n i t e dS t a t e s :
U.
S.
Geol.
Survey
Bull.
5411 499 P .
Campbell, M.
andClark,
R.,
F.
samples f r o mv a r i o u s
R.
€I.,1978,
1915,Analyses
of c o a l
p a r t s o ft h eU n i t e dS t a t e s :
Geol. Survey B u l l . 621,332
Carter, C.
,
p.
A r e g r e s s i v eb a r r i e r
and b a r r i e r -
p r o t e c t e dd e p o s i t s D
: e p o s i t i o n a el n v i r o n m e n t s
v o l . 48, p . 933-950.
Sand:Jour.Sed.Petrology,
, 1980,Petrology,Diagensis,and
Stratigraphyofthe
Univ. l k x a s Austin,unpub.
M.S.
t h e s i s , 243 p .
New Mexico Bureau of MinesandMineral
R e s o u r c e s ,o p e n - f i l er e p o r tn o .
E.
New Mexico:
1974C
, o m p o s i t es t r a t i g r a p h i cc o l u m n ,
E.,
Magdalena area:
Chapih; C.
Genetic
Eocene Baca Formation, Alamo Navajo
R e s e r v a t i o na n dV i c i n i t y ,S o c o r r oC o u n t y ,
Chapin, C.
and
of t h e Late T e r t i a r yC o h a n s e y
g e o g r a p h i c a ls e t t i n g
C a t h e r , S. M.
U. S .
, Blakestead,
R.
46.
andSeimers,
B.,
W. T.
Geology o f t h e Magdalena area, SocorroCounty,
,
1975,
New
-
Mexico; i n F i e l d t r i p s t o c e n t r a l New Mexico; p a r t 2:
Am.
ASSOC.
PetroleumGeologistGuidebook,
S e c t . Ann. Mtg. June,1975,
Rocky Mtn.
p . 43-49.
I
Chapin, C.
E.
, andSeager , W.
Grande r i f t i n t h e S o c o r r o
R.,
1 9 7 5 ,E v o l u t i o no ft h e
and Ias Cruces areas:
Rio
New
137
MexicoGeol.
SOC. Guidebook26th
p.
f i e l dc o n f e r e n c e ,
297-321.
, J r . , 1 9 5 5 ,P h y s i c a l limits o fg l a u c o n i t e formation: A
m. ASSOC. P e t r o l e u mG e o l o g i s t B u l l . , v o l 3. 9 ,
Cloud, P.
E.
p. 484-492.
Cobban, W.
of theDakota
1 9 7 7 a ,F o s s i lm o l l u s k s
A.,
Sand-
New
s t o n e and i n t e r t o n g u e d Mancos S h a l eo fw e s t - c e n t r a l
Mexico:
New Mexico Geol.SOC.Guidebook20thfield
c o n f e r e n c e , p. 213-220.
Cobban, W.
1 9 7 7 b ,C h a r a c t e r i s t i cm a r i n em o l l u s c a nf o s -
A.,
s i l s from t h e DakotaSandstoneandintertongued
S h a l e , west-central New Mexico:
Prof.Paper
Cobban, W.
S. Geol.Survey
U.
1009, 74 p.
and Hook, S. C.,
A.,
Mancos
1 9 7 9 ,C o l l i g n o n i c e r a s
w o o l l g a r iw o o l l g a r i( M a n t e l l )
ammonitefaunafrom
Upper C r e t a c e o u s of W e s t e r nI n t e r i o r ,
United S t a t e s :
New Mexico BureauofMinesandMineralResources,
37,51
Cobban, W.
the
Mem.
p.
A.
, andReeside,
J.
€3,. Jr ., 1 9 5 2 ,C o r r e l a t i o no f
of
t h eC r e t a c e o u sf o r m a t i o n so ft h eW e s t e r nI n t e r i o r
t h eU n i t e dS t a t e s :
Geol. SOC. America B u l l .
, vol.
no. 10, p. 1 0 1 1 - 1 0 4 4 .
Cobban, W.
A.,
a n dS c o t t ,
G.
R.,
1 9 7 2 ,S t r a t i g r a p h ya n d
ammonitefaunaoftheGranerosShaleandGreenhorn
Limestone nearPueblo
, Colorado:
Prof. Paper645,108
p.
U.
S. Geol.Survey
63,
138
Coleman, J. M.
,
1969,Brahmaputra
River:
c h a n n e l processes
andsedimentation:Sed.Geology,vol.3,
Coleman, J. M . ,
andGagliano,
p. 129-239.
S. M . ,
1965,Sedimentary
in
Mississippi R i v e r D e l t a i c P l a i n ;
structures:
s t r u c t u r e s and t h e i r hydrodynamic
P r i m a r ys e d i m e n t a r y
interpretation:
SOC. Econ. P a l e o n t o l o g i sat n d
a l o g i s ts p e c .p u b .n o .
Miner-
1 2 , p. 113-148.
1899, Description o f t h eT e l l u r i d eq u a d r a n g l e
Cross, W.,
U. S. Geol. Survey Atlas, T e l l u r i d ef o l i o
(Colorado) :
no.
51.
Dane, C.
Waneck, A. A.
H.,
, andReeside,
Jr.,
J. B . ,
1957,
Cretaceous r o c k s i n
R e i n t e r p r e t a t i o no fs e c t i o no f
Alamosa C r e e k V a l l e y a r e a , CatronandSocorroCounties,
Am.
New Mexico:
, vol.
Assoc.PetroleumGeologistBull.
4 1 , no. 2, p . 181-196.
Cobban , W.
Dane, C. H.,
A. and Kauf fman, E.
G.
, 1966,
a reference
Stratigraphyandregionalrelationshipsof
s e c t i o n for t h eJ u a n a
t h e SanJuanBasin,
Bull.
Dane , C. H.
1224-H,
15 p.
E.
S e m i l l aS a n d s t o n e ,
t h es o u t h e a s t e r n
Dane , C. H.
U.
S.
U. S. Geol. Survey
New Mexico:
, Kauffman,
Mexico:
Lopez Member, Mancos S h a l e ,i n
G.
, andCobban,
a newmember
part o ft h e
A.
W.
of t h e Mancos S h a l e i n
SanJuanBasin,
Geol.
Survey
Bull.
1254-F,
, l a n d i s , E.
R.
, andCobban,
TwowellsSandstoneTongue
, 1968,
New
21 p.
W.
A.,
1971, ?he
of t h e DakotaSandstoneand
t h e Res Hermanos Sandstone a s usedby
Herrick ( 1 9 0 0 ) ,
139
w e s t e r n New Mexico:
U.
S. Geol.SurveyProf.
Paper
750-B, p. B17-B22.
Daugherty, L.
H.
, 1941,
C a r n e g i eI n s t .
Dickerson, K.
A.,
The Upper T r i a s s i cF l o r ao fA r i z o n a ,
p.
Wash. Pub.,526,108
B e r r y h i l l , H.
Jr., and Holmes, C. W.,
L.,
1972, C r i t e r i a f o rr e c o g n i z i n ga n c i e n tb a r r i e rc o a s t -
-
l i n e s ; in Recognition of ancient sedimentary environm e n t s , J. Rigbyand
Hamblin eds. :
W.
SOC. Econ.
P a l e o n t o l o g i s t and M i n e r a l o g i s t spec. pub.no.
16, p.
192-214.
J., 1962,
Doeglas, D.
of b r a i d e dr i v e r s :
E l s t o n , W.
E.
The s t r u c t u r e of s e d i m e n t a r yd e p o s i t s
Sed.,
v o l . 1, p. 167-190.
, 1 9 7 6 ,G l o s s a r yo fs t r a t i g r a p h i ct e r m so ft h e
-
New Mexico; i n
Mogollon-Datil Volcanic Provence,
New Mexico:
CenozoicVolcanisminSouthwestern
New
Mexico Geol. SOC.spec.pub.no.5,151p.
Erpenbeck, M.
F.
, a n dF l o r e s ,
R.
1 9 7 9 ,S t r a t i g r a p h ya n d
M.,
Upper Cretaceous
d e p o s i t i o n a le n v i r o n m e n t so ft h e
P i c t u r e d C l i f f s S a n d s t o n ea n dF r u i t l a n dF o r m a t i o n si n
thesouthwesternSanJuanBasin,
New Mexico:
Geol. SOC. America Abstracts withPrograms,
Sect. 32nd Ann. Mtg.,
F i s h e r , J. J.
,
Rocky Mtn.
May, 1979, p. 271.
1 9 6 8 ,B a r r i e ri s l a n df o r m a t i o n :d i s c u s s i o n :
Geol. SOC. America B u l l . ,
F i s h e r , W. L. and Brown, L. F.
System,
(abstract)
&
vol.
.
7 9 , p. 1421-1426.
, Jr ,
1972,Beachand
Clastic DepositionalSystems
-A
Barrier
Genetic
140
Approach t oF a c i e sA n a l y s i s :T e x a sB u r e a uo f
Geology,211
F i s k , H.
N.
,
Economic
p.
1960,Recent
Mississippi R i v e rs e d i m e n t a t i o n
andpeataccumulation:
Cong. Av. E s t u d e s de S t r a t i -
g r a p h i e e t deGeologieduCarbonifere,
4th
, September,
1958, Heerlen, Compte r e n d u , p. 187-199.
Fitzsimmons, J. P.,
west-central
1959, !the s t r u c t u r e andgeomorphologyof
New Mexico
-
A r e g i o n a ls e t t i n g :
New
Mexico Geol. SOC., G u i d e b o o k1 0 t hf i e l dc o n f e r e n c e ,
p.
112-116.
F o l k , R.
L.
,
1968,PetrologyofSedimentaryRocks:Hemphill
Press, Austin,Texas,170p.
F o s t e r , R. W.
,
1 9 6 4 ,S t r a t i g r a p h y
t i e s of CatronCounty,
a n dp e t r o l e u mp o s s i b i l i -
New Mexico:
of Mines andMineralResources
F r o s t , S. J. , Tabet, D. E.,
Bull.
andCampbell,
New MexicoBureau
85,55p.
F. W.,
1979,Coal
D a t i l MountainCoalField:
e x p l o r a t o r yd r i l l i n gi nt h e
, open-
New Mexico Bureau of MinesandMineralResources
f i l e r e p o r t no. 111, 49 p .
Galloway, W.
E.,
C o a s t a lP l a i n
1 9 7 7 ,C a t a h o u l aF o r m a t i o no ft h e
-
D e p o s i t i o n a ls y s t e m s ,c o m p o s i t i o n ,
structural developnent
u r a n i u md i s t r i b u t i o n :
Geol.,
Galusha, T.,
Texas
, ground-water
flow h i s t o r y , and
Univ. of TexasBureau
o f Econ.
59 p .
and B l i c k , J. C.,
1 9 7 1 ,S t r a t i g r a p h yo ft h e
S a n t a Fe Group, New Mexico:
B u l l . ,v o l .
Am.
1 4 4 , a r t . 1, 127 p .
Mus. Nat. H i s t o r y
141
A
Garner
A
U.
r
J. H.,
1910, The Carthage coal f i e l d , N e w Mexico:
Geol.SurveyBull.381,
S.
Givens, D. B . ,
p. 461-473.
1957,,Geologyofthe
Dog S p r i n g sQ u a d r a n g l e :
New Mexico Bureau of MinesandMineralResourcesBull.
,
58, 40 p .
Gould, H.
R.
, andMorgan,
J. P.
swamps and marshland;
in
Texas:
Houston
Geological
E.,
1962, Coastal L o u i s i a n a
Geology of t h e Gulf Coast and
c e n t r a l Texas andguidebook
Gregory, H.
,
o f e x c u r s i o n s :H o u s t o n ,
SOC., p.
287-341.
1 9 1 6 , The Navajocountry;
h y d r o g r a p h i cr e c o n n a i s s a n c e
a g e o g r a p h i c ,and
of p a r t s of Arizona, N e w
U. S. Geol. Survey,
Water-Supply
Mexico,
and
Utah:
Paper 380.
H a r r i s o n , R. W . ,
1980,Geology
of t h en o r t h e a s t
Dati 1
N e w Mex ico :
Mountains,SocorroandCatronCounties,
M. S. t h e s i s ,
New Mexico I n s t . MiningandTech.,unpub.
137 p.
Hawley, J. W . ,
Bachman, G. 0.
,
Q u a t e r n a r ys t r a t i g r a p h yi n
G r e a tP l a i n sP r o v i n c e s ,
in Quaternary
ed.:
andManley,
K.,
t h e Basinand
N e w Mexicoand
1976,
Range and
w e s t e r n Texas;
S t r a t i g r a p h y of North America, W. Mahaney
Dowden, Huthicsonand
Ross, Inc.
,
Stroudsburg,
Penn., p . 235-275.
Hayes, M. O., 1 9 6 7 H
, urricanes
a s g e o l o g i c a la g e n t s :c a s e
s t u d i e s of h u r r i c a n e s Carla 1961,andCindy1963:
TexasBureauof&on.Geology
Rept. I n v e s t . 6 1 , 54 p .
142
1 9 0 0 , Report on a g e o l o g i c a lr e c o n n a i s s a n c e
H e r r i c k , C. L . ,
i n w e s t e r nS o c o r r oa n dV a l e n c i a
Am.
G e o l o g i s t ,v o l .
Holmes, W. H.,
C o u n t i e s , New Mexico:
25, p . 331-346.
1877,Report
on t h e San Juan d i s t r i c t :
Geol. Survey Terr.,
9 t h Ann. Rept., p . 237-276.
, andCobban,
( S t a n t o n ) - common
W.
Hook, S. C.
New Mexico:
A.,
1 9 7 7 , Pycnodontenewberryi
g u i d ef o s s i li n
N e w Mexico Bureauof
R e s o u r c e s Ann. Rept.,1976-77,
Hook, S. C . ,
andCobban,
mexicanus(Marcou)
W. A . ,
-
Hook, S. C . ,
andCobban,
1 9 7 9 , P r i o n o c y c l u sn o v i -
New Mexico Bureau of Mines and
Ann. Rept.,1977-78,p.
W. A . ,
S h a l e s , New Mexico:
Hook, S. C.,
andCobban,
Mines andMineral
p . 48-54.
34-42.
1980a, Some g u i d ef o s s i l s
Upper CretaceousJuanaLopez,
M i n e r a lR e s o u r c e s ,
Upper C r e t a c e o u so f
common Upper C r e t a c e o u sg u i d e
f o s s i l i n New Mexico:
M i n e r a lR e s o u r c e s ,
U. S.
in
Mancos and C a r l i l e
New Mexico B u r e a u o f Mines and
Ann. Rept.,1978-79,
W.
t y p es e c t i o no fJ u a n a
A.,
p . 38-42.
1 9 8 0 b ,R e i n t e r p r e t a t i o no f
Lopez Member of Mancos S h a l e :
New Mexico Geology, vol. 2 , no.2,p.17-22.
Hook, S. C . ,
Cobban, W. A . ,
andLandis,
E.
R.,
1980,
ExtensionoftheintertonguedDakotaSandstone-Mancos
S h a l et e r m i n o l o g yi n t ot h es o u t h e r n
Mexico Geology,vol.2,no.
J i c h a , H.
L.
3 , p.
ZuniBasin:
New
42-44 and 4 6 .
, J r ., 1 9 5 8 ,G e o l o g ya n dm i n e r a lr e s o u r c e so f
Mesa d e l Oro Quadrangle,SocorroandValencia
Counties,
1 43
N e w Mexico:
I
N e w Mexico BureauofMinesandMineral
Resources, B u l l .
,
Johnson, B. D.
56, 6 7 p .
1 9 7 9 ,G e n e t i cs t r a t i g r a p h ya n dp r o v e n a n c eo f
,
t h e Baqa Formation, New Mexico,andEagarFormation
Arizona:Univ.Texas
a t Austin,unpub.
M.
S. t h e s i s ,
150 p .
K e l l e y , V.
, 1 9 5 5R, e g i o n atle c t o n i c so tfh eC o l o r a d o
C.
p l a t e a u and r e l a t i o n s h i p s t o t h e o r i g i n
’
and d i s t r i -
o f New Mexico Press, no. 5,
butionofuranium:Univ.
1 2 0 p.
K e l l e y , V.
C.
, 1 9 5 7 ,T e c t o n i c so f
s u r r o u n d i n ga r e a s
t h e SanJuanBasinand
Four CournersGeological
:
G u i d e b o o k ,s e c o n df i e l dc o n f .
San JuanBasis,p.
and Wood, G.
C.,
of t h e s o u t h w e s t
44-52.
1
K e l l e y , V.
, Geology
SOC.
H.
,
1946,Lucero
S o c o r r o a, n dB e r n a l i l l oC o u n t i e s ,
Uplift, V a l e n c i a ,
New Mexico:
U.
S.
I
Geol.Survey,
King, P. B . ,
O i l and Gas I n v e s t . Prelim. Map 47.
1977, The e v o l u t i o n of NorthAmerica:Princeton
Univ. Press, P r i n c e t o n
Landis, E. R.,
Dane, C. H.,
graphic terminology
Shale
West-Central
,
New J e r s e y ,1 9 7
andCobban,
Io f
W.
p.
A.,
1 9 7 3 ,S t r a t i -
t h e DakotaSandstoneand
New Mexico:
Mancos
U. S. Geol.
Survey,
B u l l . 1372-J, p . J l - J 4 2 .
Maberry, J
tion
U t ah :
O.,
1971,Sedimentary
Cretaceous)Sunnyside
f e a t u r e s , B l a c k h a w k formaD i s t r i c t , CarbonCounty,
U. S. Geol. Survey,Prof.Paper688.
144
M a s s i n g i l l , G.
1979,GeologyoftheRiley-Puertecito
L.,
of C o l o r a d oP l a t e a u ,
a r e a ,s o u t h e a s t e r nm a r g i n
County, N e w Mexico:Univ.Texas
Socorro
E l Paso,unpub.
301 p.
D.G.S.,
, andGroat,
McGowen, J. H.
West Texas:
C.
G.
,
1 9 7 1 , Van Horn Sandstone,
model f o r m i n e r a le x p l o r a -
An A l l u v i a lf a n
o f &on.Geology,
tionT
: e x a sB u r e a u
Rept. I n v e s t n
. o.
72157P.
McKee, E.
D.
, 1 9 5 1 ,T r i a s s i cd e p o s i t s
Mexico b o r d e ra r e a ,
Mexicoand
A r i z o n a ,p .
McKnight, J. F . ,
New
85-92.
1968, Geology o f t h eB o f e c i l l o sM o u n t a i n
a r e aT, r a n s - P e c o s
,
of
New MexicoGeol.SOC.Guidebook
and west s i d e s o f t h e SanJuanbasin,
t h es o u t h
Ph .D.
o f t h e Arizona-New
Texas:
Univ.
Texas
Austin,
unpub.
198 p.
andHayden,
Meek, F. B . ,
F. V.,
1 8 6 1 ,D e s c r i p t i o no f
new
Lower S i l u r i a n , Jurassic, C r e t a c e o u s a, n dT e r t i a r y
fossilscollected
i n N e b r a s k aT e r r i t o r y
remarks on t h er o c k s
Academy Nat. S c i .
Moench, R.
,
fromwhich
Moench, R.
H.
p . 415-447.
and u r a n i u md e p o s i t s
Laguna q u a d r a n g l e , New Mexico:
Geol.Quad.
t h e yw e r eo b t a i n e d :
P h i l a d e l p h i a ,P e n n . ,
1963,Geology
H.,
w i t h some
U.
S.
Geol.Survey,
Map GQ-207.
, a n dS c h l e e ,
J. S . ,
1967,Geologyanduranium
d e p o s i t s of t h e Laguna d i s t r i c t , New Mexico:
Geol.Survey,
of t h e
prof. Paper519,
117 p.
U.
S.
145
Molenaar, C. M . ,
of
1 9 7 3 ,S e d i m e n t a r yf a c i e sa n dc o r r e l a t i o n
t h e G a l l u pS a n d s t o n ea n da s s o c i a t e df o r m a t i o n s ,n o r t h -
e a s t e r n New Mexico:FourCorners
Geol. SOC. Memoir
Book, p. 85-110.
Molenaar, C. M.
,
1 9 7 4 ,C o r r e l a t i o n
,
and a s s o c i a t e df o r m a t i o n s
SanJuanand
Geol.SOC.
of t h e GallupSandstone
Upper C r e t a c e o u s ,e a s t e r n
Acoma b a s i n s , New Mexico:
,
Guidebook25th
New Mexico
f i e l d conference , p.
251-258.
Obradovich, J. D.
, andCobban,
t h eL a t eC r e t a c e o u s
America:Geol.
O ' S u l l i v a n , R. B.,
B a s i no f
W. A.
,
1975, A time-scale f o r
of t h e w e s t e r ni n t e r i o r
of North
Assoc. Canada,spec.pub.13,
p. 33-54.
1 9 7 7 ,T r i a s s i cr o c k si nt h e
San Juan
a d j a c e n t areas:
New Mexicoand
Geol. SOC., Guidebook28th
New Mexico
f i e l d conference
, p.
139-146.
Owens, D.
E.
, 1963,?heDakotaFormation
of t h e SanJuan
Basin , New MexicoandColorado:Univ.Kansas,unpub.
Ph .D.
Owens, D.
!thesis , 353 p .
E.
,
1 9 6 6 , Nomenclature of Dakota Sandstone
( C r e t a c e o u s )i n
San JuanBasin,
Colorado:
Am.
50,no.5,
p. 1023-1028.
New Mexicoand
A s s o c .P e t r o l e u mG e o l o g i s tB u l l .
P e t e r s o n , F. , and K i r k , A. R.
,
1 9 7 7 ,C o r r e l a t i o no ft h e
I
C r e t a c e o u sr o c k si nt h e ,
, vol.
SanJuan
Basin, B l a c k Mesa ,
KalparowitsandHenryBasins,southernColorado
146
Plateau:
New Mexico Geol. SOC.,Guidebook28th
field
c o n f . , p. 167-178.
P i k e , W.
S.
,
1947,Intertonguingmarineandnonmarine
C r e t a c e o u sd e p o s i t so f
western Colorado:
Read, C.
B.,
Duffer, R.
New Mexico,Arizona,andsouth-
Geol. SOC.
Mem. 24,103p.
H.,
New Mexico:
1 9 5 0C
, o a rl e s o u r c e so f
R e e s i d e , J. B . ,
Am.,
Wood, G.
T.,
Survey, Circ. 89,24
Upper
and Zapp, A. D . ,
U.
S.
Geol.
p.
1 9 5 7 ,P a l e o e c o l o g yo ft h eC r e t a c e o u ss e a so f
i n Treaties
the Western Interior of the United States:
Geol. SOC.
onmarineecologyandpaleoecology:
A
m
.
Mem. 6 7 , vol.2,p.505-542.
Reinech, H.
andSingh,
E.,
I. B . ,
1 9 7 5D
, e p o s i t i o n a sl e d i -
mentaryenvironments:Springer-Verlag,
New York, New
York, 439 p .
Robinson, B. R . ,
1 9 7 6 ,S t r a t i g r a p h ya n de n v i r o n m e n to f
d e p o s i t i o no f
member 9 o f t h e Rawls F o r m a t i o n ,P r e s i d i o
County,Texas:Univ.ofHouston,unpub.
M.S.
thesis,
151 p .
R o e h l e r , H. W.
,
1977,Depositionalenvironmentsof
Almond F o r m a t i o ni nt h e
Rocky Mtn. Coal , Proc.
Sears,
J.
D.,
Hunt, C. B.,
the
Rock S p r i n g sU p l i f t :
, 1976
Geol.
Sympos. , p . 87.
andHendricks,
T. A.,
1941,
T r a n s g r e s s i v e and r e g r e s s i v eC r e t a c e o u sd e p o s i t si n
s o u t h e r n San JuanBasin,
New Mexico:
Survey, P r o f . p a p e r1 9 3
F , p . 101-121.
U.
S. Geol.
147
Shaw, A. B.
, Time
i ns t r a t i g r a p h y :
McGraw-Hill Book Co.,
New York, 365p.
Shomaker , J. W.
, Beaumont,
E.
and Kottlowski
C.,
New MexicoandColorado:
, 1971,
Mem. 25,189p.
S t r a t i g r a p h i ca n a l y s i so ft h e
New Mexico:
Univ.
Formationwest-central
Mexico,unpub.
S t o k e s , W. L.,
Ph.D.
T a b e t , D.
SOC.
Am.
Bull.
, vol.
2 , p. 91-98.
E.,
and F r o s t , S. J.,
Teichmuller, M . ,
and Teichmuller, R.,
Berlin-Stuttgart,
,
i n Coal Petrology,
Stach
New Mexico Bureauof
Mines
B u l l . 41, 67 p .
1 9 7 2 , P h y s i c a l c h a r a c t e r i s t i c s of f l u v i a l
in Recognition
environments:
SOC.
of a n c i e n t s e d i m e n t a r y
Econ. P a l e o n t o l o g i sat n d
M i n e r a l o g i s t spec. pub.no.
Wells, E. H.,
E.
428 p .
New Mexico:
andMineralResources
deposits:
1975, The G e o l o g i c a l
1 9 5 7 ,G e o l o g yo ft h eP u e r t e c i t oq u a d r a n g l e ,
SocorroCounty,
S.,
f i e l d s andmines
Map 10, map w i t h t e x t .
b a s i s of c o a l f o r m a t i o n ;
!tbnking, W. H.
1978,Coal
New Mexico BureauofMinesandMineral
Resources,Resources
V i s h e r , G.
of N e w
applied t o Shinarump
1950,Pedimentconcept
of New Mexico:
ed.,
Baca
t h e s i s , 160 p.
andsimilarconglomerates:Geol.
61,no.
E.,
New Mexico
Bureau of MinesandMineralResources,
Snyder, D. 0.
F.
resources o f t h e San
1 9 7 1 ,S t r i p p a b l el o w - s u l f u rc o a l
J u a nB a s i ni n
,
1 6 , p . 84-97.
1919, O i l and g a s possibilities o f t h e
P u e r t e c i t od i s t r i c t ,S o c o r r o
and V a l e n c i aC o u n t i e s ,
148
N e w Mexico:
Resources)
B u r e a u ofMinesandMineral
ResourcesSurvey,
Wilpolt, R. H.,
G.
,
MacAlpin, A. J., Bates, R.
P a l e o z o i cr o c k s
t h eo c c u r r e n c e
Bull.716,
Young, R. G . ,
of
Mesa, V a l e n c i a ,l b r r e n c e ,a n d
New Mexico:
, Map
, 1920,
SocorroCounty,
, andVorbe,
of J o y i t a Hills, Los PinosMountains
SocorroCounties,
E.
L.
map and s t r a t i g r a p h i c s e c t i o n s
andnorthernChupadera
and Gas I n v e s t .
, Mineral
3, 47 p .
Bull.
1946,Geologic
Winchester, D.
( N e w Mexico
N e w Mexico SchoolofMines
U.
S. Geol. Survey, O i l
61.
Geology of Alamosa Creek V a l l e y ,
New M e x i c o ,w i t hs p e c i a lr e f e r e n c et o
o f oil and g a s :
U.
S. Geol.Survey,
p. 1-15.
1 9 5 5 ,S e d i m e n t a r yf a c i e sa n di n t e r t o n g u i n g
Upper Cretaceous Book C l i f f s Formation, Utah and
Colorado:Geol.SOC.
Am.
Bull.
, vol.
66.
14 9
APPENDIX A
150
APPENDIX A
Point-count Mineralogy of Selected Thin-sections
"
Sample Number
4
7
7%
9
70
Quartz
90
6
86
K spar
T
T
17
Plagioclase
0
0
0
Mica
T
T
T
Glauconite
T
0
2
Rx. Frags.
Meta. Rx. Frags.
10
12
11
0
0
0
0
0
0
Others
T
T
T
Quartz 9 5
11
94
Sed.
Ign.
Rx. Frags.
Sample Number
1 912
64
17
75
K spar
11
10
Plagioclase
1
2
Mica
1
2
Glauconite
1
T
10
31
Meta.
0
0
Ign.
0
0
2
1
Sed.
Rx. Frags.
Rx. Frags.
Rx. Frags.
Others
151
Sample Number
Quartz
23
21
60
K spar
45
93
75
7
60
24
15
1
13
Plagioclase
2
1
15
8
Mica
1
T
1
1
Glauconite
T
T
0
0
Rx. F r a g s .
M e t a . Rx. Frags.
Ign. R
x. Frags.
10
4
0
7
0
0
0
6
0
0
71
2
Others
5
5
5
3
Sed.
Sample Number
Quartz
K spar
10
62
9 4 63
41
70
6 9 65
56
17
11
4
Plagioclase
3
10
8
8
Mica
1
2
1
1
Glauconite
0
0
0
0
7
11
11
12
Rx. F r a g s .
Meta. R
x. Frags.
Ign. Rx. Frags.
0
0
4
0
0
0
1
T
O t h e3r s
2
1
4
Sed.
152
Sample Number
Quartz
69
K spar
8
Plagioclase
10
Mica
Glauconite
0
Sed. Rx. Frags.
15
Meta.
Ign.
Rx. Frags.
0
Rx. Frags.
T
Others
4
Code to sample numbers in Appendix A
Sample Code
Rock Unit
Rock Name
4
Dakota- main body
Sublitharenite
6
Dakota- main body
Sublitharenite
7
Twowells tongue
Subarkose
9
Twowells tongue
Lithic arkose
11
Paguate tongue
Sublitharenite
12
Paguate tongue
Quartzarenite
17
Tres Hermanos Sandstone
Subarkose
153
Sample Code
Rock Unit
Rock Name
19
Tres Hermanos Sandstone
Feldspathic Litharenite
21
Gallup Sandstone
Lithic arkose
23
Gallup Sandstone
Subarkose
41
Baca Formation
Lithic arkose
45
Baca Formation
Lithic arkose
62
Crevasse Canyon Fm.
Arkose
63
Crevasse Canyon Fm.
Lithic arkose
93
Conglomerate of Rock Tank
Volcanicarenite
94
Chinle Formation
Lithic arkose
95
Chinle Formation
Lithic arkose
The.mineralogy is based on 2 0 0 grain-count. A l l samples were
stained for potassium. Sedimentary rock fragments include locally
derived clay-clasts. Rock names are after Folk (1968).
154
APPENDIX B
1'
mean
vector
n 20
mean N 2 E
\I
0
vector mean
i
8
number of readings
(n)
mean S
3O
Q
n
E
mean
19
s loo w
d
vector mean
~
&
vector mean
Paleocurrent Rose Diagrams: A) Chinle Formation
B) DakotaSandstone
main body C)PaguateSandstone
D) TwowellsSandstone.
-
156
n 15
mean
mean S 34 E
vector mean
0
8
number of readings
( n )
!
Paleocurrent Rose Diagramsf A) AtarqueMember
B) GallupSandstoneC)CrevasseCanyon
Formation
D) Baca Formation.
APPENDIX C
158
MEASURED S E C T I O N 1
DakotaSandstone(Main
Body)and
l i n e startingin
Measuredalonganeast-west
Section21,
t h e NW 1 / 4
8 W. on J u l y 24,1978,withJacob
T. 3 N .R, .
compass.
s t a f f andBrunton
Unit
INM S p r i n g sS h a l e
Thickness
Feet
Description
Meters
INM S P R I N G S ( p a r t i a ls e c t i o n )
8
Composite.
Sandstone
and
shale:
0.1 t o 0.3 f t t h i c k s i l t s t o n e s
v e r yf i n e - g r a i n e ds u b a r k o s e s
and
(10 Y
, moderately indurated , very
Abuncalcareous , fossiliferous.
4/2)
d a n tb u r r o w so nb e d d i n gp l a n e s .
Shalesaresilty,moderatetovery
c a l c a r e o u s , thin-bedded
a p p e a r i n g( 1 0
7
Y 7/4).
, and nodular
.......
10.1
3.1
0.5
0.1
S i l t s t o nSe i: m i lstao
irl t s t o n e s
of u n i t 8C
. o n t a i n sl a r g e ,
diameter
3.0 f t
, sub-spherical yellow
red ( 5 YR 5/1) micrite c o n c r e t i o n s
c o n t a i n i n g sparse m e g a f o s s i l s .
Thatcher
fauna.
6
..........
Composite.
Sandstone
and
shale
Same a s u n i t 8.
One-halfinch
:
ption
Thickness
Feet
Unit
Meters
b e n t o n i t e bed a t 4 . 7 ft above
base.
5
...............
Covered.
Contains
N
IM S p r i n g s -
Dakota
(Main
Body)
contact.
....
TOTAL N
IM SPRINGS TONGUE
10.7
3.3
5 .11. 5
26.4
7.9
DAKOTA SANDSTONE ( M A I N BODY)
4
Sandstone:
Thin,
wavy and f l a t
b e d ss e p a r a t e db yt h i ns h a l e
,
p a r t i n g s .L i m o n i t es t a i n e d
i n d u r a t e dM
. o d e r a t e lsyo r t e d ,
calcareous.
Burrow c a s t s abun-
d a n ta l o n gb e d d i n gp l a n e s .
G r a d e st ou n i b
t e l o w (. 5
6 / 1t o
3
N 7)
YR
.............
Composite.
Sandstone
and
shale
a
9.3
2.
7.1
2.2
:
I n t e r b e d d e dt h i nc a l c i t ec e m e n t e d
sandstonesasunit
2 a n dv e r y
s i l t yf i n e - g r a i n e ds a n d s t o n e s
( 1 0 YR 6 / 6 )w i t ha b u n d a n td i s s e m i n a t e do r g a n i cd e b r i s .
S h a l e s occur i n i r r e g u l a r t h i n
t o medium bedsand
are n o d u l a r
weathering ( N 6 t o N 8 ) .
ut onbi et l o w
S l. o p e - f o r m e r .
Grades
...
160
Thickness
Feet
D
Uensict r i p t i o n
2
Sandstone :
Meters
Moderately resis-
fine-
t a nnto n c a l c a r e o uvse r y
g r a i n e d , well s o r t e d
r
chert-
a r e n i t e ( 1 0 YR 8 / 2 )w i t hb l a c k
( N 4) carbonaceous s t r e a k s .
S i l t i e r , more carbonaceous,and
l e s s r e s i s t a n ta tb a s e .
d a n t b u r r o , ws.
Abun-
L i m o n i tset a i n i n g
( 5 YR 5/6) a l o n gf r a c t u r e sa n d
burrows.
1
S h a r pf,l abt a s e .
Sandstone :
....
1.2
0.4
Indurated, calcite
and s i l i c a - c e m e n t e d ,w e l l - s o r t e d
medium- t oc o a r s e - g r a i n e dc h e r t a r e n i t eL. e n s e os qf u a r t z pebbleandchert-pebbleconglom-
e r a t e abundant i n l o w e r p a r t
of
Base is t r o u g hc r o s s -
unit.
stratified,top
i s t a b u l a rc r o s s -
s t r a t i f i e dM
. a s s i v e l yb e d d e d
f i n e s upward.
Upper few i n c h e s
are l i m o n i t e - s t a i n e dS. h a r p
e r o s i o n a lc o n t a c tw i t hC h i n l e
shales.
.............. 15.2
TOTAL DAKOTA SANDSTONE
TOTAL MEASURED SECTION
32.8
18.0 59.2
4.6
1 0 .o
-
MEASURED
SECTION
2
INM SpringsandTwowellsTongues
east-west l i n e s t a r t i n gi nt h e
Measured
along
an
o fS e c t i o n
8,
T.
3 N.,
R.
1/4
8 W. on July25,1978,withJacob
s t a f f andBruntoncompass.
Thickness
Feet
D
Uensict r i p t i o n
Meters
TW(IWELL.9 TONGUE
block o f Tres
13
Covered.
Landslide
Hermanos Sandstone. Abundant
n e w b e r r y ia s
unit.
-P.
f l o a t a t b a s e of
...............
3.0
0.9
8.2
2.5
1.5
0.5
S1a2n d s t oFn ien: e - g r a i nc ehde r t a r e n i t ew i t hs q u a s h e d
mud c l a s t s .
Moderatelyresistant,slightly
moderately
calcareous.
to
Lower 6.0
f t t h i c k - b e d d e d ,p o o r l ys o r t e d ,
s t r o n c j l by i o t u r b a t e dB. u r r o w s
are 0.2 i n . i nd i a m e t e ra n dh o r i z o n t aPl .a lyee l l o w i s h - o r a n g e
( 1 0 YR 8 / 6 ) .
Upper 2.0 f t form
11
............
C o v e rP
ed
r o. b a sbhl ya l e .
.....
10
Sandstone:
weak bench.
Medium f i n e - g r a i n e d ,
moderately calcareous', moderately
Unit
Thickness
Feet
Description
topoorlysorted,massiveto
v a g u e l y medium-bedded.
bioturbated.
Strongly
Small c i r c u l a br u r -
rows c o n c e n t r a t e da l o n gb e d d i n g
p l ane s
9
...............
11.6
3.5
Sandstone : Well i n d u r a t e d , s i l i c a
c e m e n t ecdh e r t a r e n i t eF. i n e s
upwardfrom
medium c o a r s ep e b b l y
sandstonetolowermedium-grained
cross-bedded or h o r i z o n t a l l y
l a m i n a t e sda n d s t o n eS. h a r p
upper
c o n t a cLt i. m o n ist tea i n eLd i. g h t
g r e y ( N 7 ) t od a r ky e l l o w i s h - o r a n g e
(lOYR6/6)
. . . . . . . . . . . . 2.3
."
As u n i t 1 0 . . . . . . .
8
Sandstone:
7
S a n d s t o n Ien: d u r a t e d ,
0.7
1.3
0.4
4.9
1.5
silica
c e m e n t e dc h e r t a r e n i t eF. i n e s
up-
ward t o medium c o a r s ep e b b l ys a n d s t o n eT. a b u l acrr o s s - s t r a t i f i e d
or h o r i z o n t a l l yl a m i n a t e d S. l i g h t l y
c a l c a r e o u s , medium thick-bedded.
Moderate brown ( 5 YR 4 / 4 )
6
tolight
grey (N 7 ) .
. . . . ',.. . . . . . .
Sandstone:
Base o fc l i f f - f o r m e r .
M a s s i v e l yb e d d e d ,f i n e - g r a i n e d
ption
163
Thickness
Feet
Unit
Meters
well
chertareniteM
. o d e r a t e l yt o
s i l i c a and c a l c i t e
s o r t e d ,c l a y ,
c e m e n t sS. t r o n g l yb i o t u r b a t e di n
upper p a r t .
Liesegang
banding
pronounced.Gradestounitbelow.
Greyish-orange
( 1 0 YR 7/4).
TOTAL TWOWELLS
....
.
13.4
11.2
3.4
44.0
WHITEWATER ARROYO TONGUE
5
S h a l e : S i 1t y v, e r yc a l c a r e o u s ,
dark-grey
Lower
( N 3 t o N 5).
h a l fo fu n i tp o o r l ye x p o s e d .
Con-
t a i n s two b e n t o n i t e b e d s ; t h e
loweststratigraphically
f t t h i c k andoccurs
i s 0.6
13.0 f t above
t h e base of t h eu n i t .
'Ihe second
b e n t o n i t e i s 0.2 f t t h i c k and
o c c u r s 8 7 . 0 f t above base o f t h e
u n i tF. l o aot cf o n e - i n - c o n e
1imestone and
G r a d etuosn i t
micr i t e n o d u l e s .
6.
.........
TOTAL WHITEWATER ARROYO TONGUE
91.8
28.0
91.8
28.0
21.8
6.6
PAGUATE TONGUE
4
Covered.
Base
a l sl ya n d s t o n e .
of s l o p e .
Iater-
..........
164
Thickness
Feet
D
Uensict r i p t i o n
3
Sandstone :
Meters
Coarsening upward
from s i l t y , p o o r l y s o r t e d , v e r y
f i n e - g r a i n e dq u a r t z a r e n i t et o
moderately sorted
, indurated,
b i o t u r b a t e d ,d u s k yy e l l o w
6/4)
(5 Y
f i n e - g r a i n e ds a n d s t o n e .
L i m o n i t se t a i n e d .
Lower p a r t
Forms weak bench.
organic-rich.
Base
not
exposed.
.........
TOTAL PAGUATE TONGUE
14.2
4.3
36.0
11.0
57.2
17.4
N
IM SPRINGS TONGUE
2
S h a l e : M o d e r a t e l yc a l c a r e o u s
,
splinteryweathering,silty,
common m e g a f o s s i l f l o a t
gypsum c r y s t a l .
( N 5).
and
Medium-grey
'Ituo b e n t o n i t e s ;t h e
s t r a t i g r a p h i c a l l yl o w e ru n i t
is 0.2 f t t h i c k and o c c u r s a t
26.0 f t a b o v e t h e b a s e o f t h e
u n i t ;t h eo t h e r
a n do c c u r s
u n i t base.
is 0.3 f t t h i c k
a t 43.0 f t above
B e n t o n i t e s are p a l e
greenish-yellow
( 1 0 Y 8/2)and
weathergreyish-orange
7/4).
( 1 0 YR
................
165
Th i c kne ss
Feet U n i t
1
Description
Covered.
Forms g r a s s y f l a t .
Laterally shale
..........
IM SPRINGS TONGUE
TOTAL N
TOTALMEASURED
SECTION
30.1
87.3
259.1
9.2
26.2
79.0
ption
166
MEASURED SECTION 3
PaguateSandstone
Measured i n t h e
N.,
R.
bed o f Rio S a l a d oi nS e c t i o n5 ,
T. 3
8 W. Wiley Mesa q u a d r a n g l e on J u l y 30, 1978with
J a c o b s t a f f andBruntoncompass.
Thickness
Feet
Unit
Meters
PAGUATE TONGUE
3
Sandstone : Medium-grained,
slightly glauconitic quartzarenite.
Well s o r t e d , c a l c i t e
cemented , b i o t u r b a t e d
cross-stratified.
, tabular
Knobby
w e a t h e r i n g ,l i g h t - g r e y
(N 7 ) .
Scarce
inoceramids.
Grades
...........
to
u n ibt e l o w
2
Sandstone:
2.5
0.8
14.5
4.4
Upper f i n e - to lower
medium-grained
, moderately
sorted
,
c a l c i t e c e m e n t e dq u a r t z a r e n i t e .
H o r i z o n t a l l lya m i n a t e dB. i o t u r bated
z o n e sL. i g h t - o l i v g
erey
.
( 5 Y 6 / 2 )G
. r a d e tsou n ibt e l o w .
1
S a n d s t o n se i: l tvye rf yi n e g r a i n e dq u a r t z a r e n i t e .
Hard ,
indurated, light-olive grey
167
Thickness
Unit
Feet
( 5 Y 5/2)
Meters
to medium-grey ( N 6 ) .
E x t r e m e lbyi o t u r b a t e dI s. o l a t e d
l e n s e s o f inoceramids and r a r e
ammonites; P. l a n d i s i .
t o u nbi et l o w
Grades
...........
TOTAL PAGUATE TONGUE
TOTAL MEASURED SECTION
15.5
4.7
32.5
9.9
-
32.5
9.9
"
168
MEASURED S E C T I O N 4
Rio S a l a d oS h a l e
M e a s u r e da l o n ga ne a s t - w e s tl i n es t a r t i n g
of t h e TwowellsSandstone
i nt h e
from t h e t o p
SW 1 / 4 S e c t i o n 20, T.
3 N.,
8 W. onAugust29,1978withJacobstaffandBrunton
R.
compass.
Thickness
Feet
Unit
Meters
R I O SALAD0 TONGUE
.
26.8
8.2
...........
41.6
12.7
R e s Hermanos.
13
Covered t ob a s eo f
12
S h a l eG
: r e y i s h - o l i v eg r e e n
( 5 GY
3/2),silty,splinteryweathering,
noncalcareous
11
Concretionzone:
2.0 f t d i a m e t e r ,
subsperical , carbonate concretions
c o n t a i n i n g Mammites d e p r e s s u s
10
,
...
0.72.3
S h a l e :O l i v eg r e e nt om o d e r a t e g r e y ( 5 G Y 4/2 t o N 6 ) , v e r y cal-
..........
c a r e os iulst ,y .
9
Bentonite:
24.1
79.1
White ( N E ) , w e a t h e r s
greyish-orange
....
........
( 1 0 YR 7 / 4 ) .
8
Shale:
As u1n0i. t
7
S a n d s t o n e :C a l c a r e n i t e
, grey
brown ( N 5 t o 5 YR 5 / 2 ) , t h i n l y
to
0.2
0.1
11.1
3.4
169
Unit
Thickness
Feet
Description
Meters
l a m i n a t e d ,l i n e a t e d ,M y t i l o i d e s
mytolodies hash abundant.
6
0.9
0.3
32.5
10.0
1.2
0.4
3.4
1.0
10.1
3.0
0.1
0.1
20.1
6.1
TOTAL RIO SALAD0 TONGUE
229.4
69 -9
TOTAL SECTION MEASURED
229.4
69.9
Shale:
As u n i t1 0 ,s h a r kt e e t h
as f l o a t .
5
3
Calcarenite, as unit
...............
Shale:
Poorly e x p o s e d , g r e y ( N 6 ) ,
s i l t y , non-calcareous
.......
C o v e r e dP
. r o b a b l ys h a l e
as u n i t
4 .
2
.............
Sandstone :
7 . .
4
................
B e n t o n i t eC
: o v e r e di n
l i n e of
s e c t i o enx p o s e lda t e r a l l y
1
.....
Covered.
.....
Across g r a s s y f l a t ,
p r o b a b l ys h a l e
a s u n i t 4.
.....
ption
170
MEASURED
SECTION
5
Tres Hermanos Sandstone
east-west l i n e s t a r t i n g i n t h e
Measuredalongan
S e c t i o n l g r T. 3 N.r
R.
8 W. on J u l y 30,1978
SW 1/4
w i t h Jacob
s t a f f andBruntoncompass.
Thickness
Feet
Unit
Meters
TRES
HERMANOS
SANDSTONE
F I T E RANCH MEMBER
17
Sandstone
Fining upward
:
sequence.
Base i s massive
s p h e r o i d a lw e a t h e r i n g ' ,b i o t u r b a t e d , medium f i n e - g r a i n e d
silty,moderatelysortedsub-
arkose c o n t a i n i n g commonmud
clast.
Upper p a r t of u n i t
is f i n e - g r a i n e d , s l i g h t l y
c a l c a r e o u s and carbonaceous.
Large, 5.0 f t diameter, brown
(5 YR 4 / 2 ) carbonatecemented
c o n c r e t i o n s are common a t t o p .
I_
E r o s i o n a lb a s e ,s h a r pf l a t
u p pceor n t aw
c ti t h
D Cross.
TOTAL FITE RANCH MEMBER
....
24.1
7.324.1
7.3
171
Thickness
Unit
Description
Feet
. .
Meters
CARTHAGE MEMBER
16
Shale:
Black ( N 2 )
,
nonsi1 t y
calcareous carbonaceous,
C o n t a i n s s e v e r a l muddy v e r y
......
f i n e - g r a i n esdu b a r k o s e s
15
27.2
8.3
3.1
0.9
3.9
1.2
4.0
1.2
7.2
2.2
Sandstone:
Fines
upward.
Fineg r a i n e d ,n o n c a l c a r e o u s ,
a t e l y to poorly sorted
moder-
, s u b a r kose.
Common c o aflr a g m e n t sG. r e y i s h y e l l o wg r e e n
( 5 GY 7 / 2 ) .
...........
b a s ac lo n t a c t
14
Sharp
S h a l eG: r etbyol a c k
(N 6 t o
N 2 ) , si1 t y , n o n c a l c a r e o u s ,
carbonaceous.
13
Sandstone :
...........
Moderately r e s i s -
t a n t , punkyweathering,
calcareous.
non-
Muddy ‘ f i n e - g r a i n e d
subarkose.ModeratelySorted
atop.
Weak bench-former.
Light-grey
t o greyish-yellow
g r e e n ( N 6 t o 5 G Y 7/2)
12
Covered.
Probably
shale.
11
Shale:
......
.....
Black ( N 3 ) , non-
c a l c a r e o u s ,b l o c k y
to s p l i n t e r y
ption
172
Thickness
Feet
Unit
trace
w e a t h e r i n g ,c l e a n ,
.......
c a r b o n a cm
e oaut es r i a l
10
Meters
5.4
17.6
Composite.
Sandstone
and
shale:
S h a l e sa r ep a l eo l i v e
(10 Y 6/2)
Rare i r o n s t o n e
poorly
exposed.
c o n c r e t i o n s and l i g n i t e z o n e s ;
Sandstones are n o n c a l c a r e o u s
m o d e r a t e l yr e s i s t a n t ,
( 5 GY 6/1)
and d i s c o n t i n u o u sP.e b b l e - s i z e d
clayclastabundantatbase.
F i n e - g r a i n e dl i t h i ca r e n i t e s .
C l a yp o r e - f i l l
and l i m o n i t ec e m e n t .
S h a r pl o w e rc o n t a c t ,g r a d a t i o n a l
...........
u cp op ne tr a c t
7
S a n d s t o nR
e :e s i s t a n t
44.2
13.5
sorted,
I
h o r i z o n t a l l yl a m i n a t e dt os t r u c -
t u r e l e s s I t h i n - b e d d e db i o t u r b a t e d ,
f i n e - g r a i n esdu b a r k o s L
e .i g h t g r e yt og r e e n i s h - y e l l o w
Y 7/2).
(N 8 t o 5
..............
TOTAL CARTHAGE MEMBER
1.O
123.2
0.3
37.6
ATARQUE MEMBER
6
Sandstone:
Iower p a r ,lti;g h t
+
g r e y (N 7), m o d e r a t e l y resistant, very calcareous
I
fine-
ption
113
Thickness
Feet
Unit
Meters
g r a i n e ds ,u b a r k o s eM
. oderately
Upper p a r t ; Iower
bioturbated.
, moderately
fine-grained
sorted ,
h o r i z o n t a l l yl a m i n a t e d ,s l i g h t l y
c a l c a r e o u s ( N 8 t o N Y 7/2).
G r a d e st ou n i b
t elow.
'lbp of
......
c l i f f - f o r m i nsga n d s t o n e
5
Composite.
Sandstone
,
1.5
15.0
4.6
and s h a l e :
as follows;
T h r e ec y c l i c a lu n i t s
non-resistant
4.9
slightly calcareous
mudstone,carbonaceous,
( 5 Y 4/2)
,
b l o c k yw e a t h e r i n g ,g r a d e st o
punky weathering
( 5 Y 7/2)
, noncalcareous ,
, silty fine-grained,
moderatelyresistantcarbonaceous
subarkose.
'Ibp o fu n i t
medium-grained,
i s lower
s a l t and pepper
, irregular
, well-sorted , hori-
with orange pinpoints
medium-bedded
zontally laminated
, moderately
b i o t u r b a t e ds u b a r k o s e .
u n i t i s i n v e r s e l yg r a d e d .
4
Each sub-
.....
S a n d s t o n eT:h i ctvkoe rtyh i c k
beds
, moderately calcareous sub-
arkoses.
Base i s punky, s i l t y
1
174
Thickness
Feet
DUensict r i p t i o n
Meters
andfine-grained,withvague
h o r i z o n t al al m i n a t i o n sM. i d d l e
p a r t is f i n e - g r a i n e d , mediumbedded I s l i g h t l y b i o t u r b a t e d ,
h o r i z o n t a l l yl a m i n a t e d .
Minor
t a b u l acrr o s s - l a m i n a eP.o o r l y
d e v e l o p e dc a r b o n a t ec o n c r e t i o n s
( N 8 ) w i t ho r a n g e
n e a r top.
..............
specks.
3
Covered.
24.4
7.4
13.1
4.0
L a t e r asl l o
yp e -
f o r m i n gv e r yc a l c a r e o u s
I
bio-
t u r b a t e d , c o a r s e si1t s t o n e t o
f i n se a n d s t o n e .
2
Sandstone :
S h a ripr r e g u l abra s e
Low angle
w i t hs o l em a r k i n g s .
cross-laminae
r i p p l e dz o n e s .
bedded.
a t baseand
Medium-
arkose.
rare
to thick-
( 1 0 YR 7/4).
Moderately
Fine-
c a l c a r e o u rse s i s t a n t .
grained
....
( 5 Y 7/2).
I
m o d e r a t e l y sorted sub-
Upper p a r t o f u n i t is
t h i n t o medium-bedded
I
trough
or t a b u l a rc r o s s - s t r a t i f i e d ,
f l a g g yv
, e r yc a l c a r e o u sc o n cretionary lower medium-grained
175
Thickness
tion
Unit
Meters
s u b a r k o s e ,r o u n d e dw e a t h e r i n g
outcrop
1
..............
30.8
9.4
5 .O
1.5
Composite.
Sandstone
and
shale:
S a n d s t o n e s are t h i n , h o r i z o n t a l l y
laminated, slightly calcareous
c a r b o n a c e o u sa n dv e r yf i n e - g r a i n e d .
( 5 YR 5/1).
Micaceous.
Sharp
i r r e g u l a rb a s e s
and f l a t s h a r p
u p p e cr o n t a c t s S. l i g h t l yb i o turbated,groovecast
S h a l e sa r ed a r kg r e y
on soles.
(N 3),
slightly calcareous, silty
carbonaceous.
and
...........
TOTAL ATARQUE MEMBER
25.4
TOTAL TRES
HERMANOS
SANDSTONE
TOTAL SECTION MEASURED
70.3
230'.5
70.3
__
230.5
-
83.2
176
MEASURED S E C T I O N 6
D CrossShale
M e a s u r e da l o n ga ne a s t - w e s tl i n es t a r t i n gi nt h e
S e c t i o n 30, T.
3 N.,
R.
NW 1/4
8 W. on August 3, 1978withJacob
s t a f f andBruntoncompass.
Unit
Thickness
Feet
Description
D CROSS TONGUE
4
S h a lS
e :l i g h t m
tl o
yo d e r a t e l y
calcareous.
Breaks chunky.
Brokenoysterfragmentsand
m i c r o f o s s i l s common.
tolight-olivegrey
Y 5/2).
Dark-grey
( N 3 to 5
Gypsum
common
i nf r a c -
t u r e s andalongbeddingplanes.
C o n c r e t i o n a r yz o n e sa t1 4 3 . 0
and134.0
ft
f t abovebaseofforma-
t i o nC
. o n c r e t i o n as r ec; a r b o n a t e ,
two t of o u r
f e e t i nd i a m e t e r
and
s u b s p h e r i c a la n do f t e nh a v ef o s s i l
( a m m o n i t e )n u c l e i (. 5
Y 4/1 t o
5 Y 7/2),olivegrey
to yellowish-
g r e yI.n t e r b e d d e d
Sandstone
w i t h Gallup
. . . . . . . . . . . . . 107.132.6
Meters
177
Unit
3
Meters
Description
Thickness
Feet
S h a l eS: i l t yn, o n c a l c a r e o u s ,
chunkw
y e a t h e r i n fgo s s i l i f e r o u s .
Medium-dark g r e y t o o l i v e g r e y
.........
(N 4 t o 5 Y 5/1).
2
Limestone :
Concretionzone
44. 0
13.4
2.1
0.6
I
micrite
undulatorybed.Sandy
A few
c o n t a i n i n gf o s s i ld e b r i s .
i s o l a t e ds e p t a r i a nc o n c r e t i o n s .
Common gypsum v e i n - f i l l i n g
.
Yellowish-brownweathering
...............
5/6).
1
( 1 0 YR
Shale :
S i l t y ,n o n c a l c a r e o u s
d a r k - o l i v eg r e y( 5
Y 4/1).
I
Con-
tains thin beds of very fine
s a n d s t o n ea n ds a n d s t o n e - f i l l e d
burrows.
Prominent
concretionary
zones 1 . 0 f t and 9 . 0 f t above
base of u n i tC
. o n c r e t i o n so f t e n
as nuclei:
c o n t a i na m m o n i t e s
.
Pr i o n o c y c l u s sp
collecti.
I
Coilopocer as
Sharp f l a t t o undula-
t o r yl o w e rc o n t a c t .
. . . . . . . . -20 .o
TOTAL D CROSS TONGUE
TOTAL MEASURED SECTION
173.2
52.8
173.2
6.1
52.8
-
178
MEASURED SECTION 7
GallupSandstone
M e a s u r e da l o n ga ne a s t - w e s tl i n es t a r t i n g
1/4 S e c t i o n 30, T. 3 N.,
Jacobstaff
, steel
from t h e SE
8 W. on August 6 , 1978, w i t h
R.
tapeandBrunton
compass.
Thickness
Feet
D
Uensict r i p t i o n
Meters
GALLUP SANDSTONE ( P a r t i a l S e c t i o n )
6
S a n d s t o nM
e :a s s tithvoiec k l y
bedded, s t r u c t u r e l e s s .
Non-
c a l c a r e o u s , medium f i n e grained
, s o r t e d , moderate1 y
bioturbated subar kose
with
matrix.
c l a yp o r e - f i l l
One
t o 5.0 f t t h i c k s t r o n g l y
pale
b i o t u r b a t e dz o n e s ,
yellowish-brown
5
Sandstone:
( 1 0 YR 7/2)
....
20.1
6.1
3.1
0.9
P a r a l l e l lami-
, moderately calcareous ,
r e s i s t a n t , s o r t e d , s u b a r kose ,
nated
c a l c a r e o u sc e m e n t ,p a l e o r a n g e ( 1 0 YR 8 / 2 ) .
4
Sandstone :
........
Thickly
bedded,
g e n e r a l l y s t r u c t u r e l e s s with
m i n o re l o n g a t e ,l i g h t - b r o w n
179
Unit
Thickness
Feet
Description
Meters
( 5 YR 6/4) burrows.
Locally
intenselybioturbatednear
b a s eo f
unit,
fine-grained
S o r t e d , upper
, noncalcareous
toslightlycalcareous,resis-
.........
t a n t , subarkose.
3
Sandstone :
Verycalcareous
24.8
7.6
31.2
9.5
1.5
0.5
,
, friable,
( 5 Y 7/2) ,
moderately sorted
yellowish-grey
subarkose.
cliff.
Forms b a s e of
Upper f i n e - g r a i n e d
and t h i c k l b
yedded.
bed f i n e s upward.
Each
Tops o f
bedsstronglybioturbated.
Minor p a r a l l e l l a m i n a t i o n .
Sharpe f l a t base.
2
.........
cal-
ShaleS
: i l t y s, l i g h t l y
1
c a r e o u s ,c h u n k yw e a t h e r i n g ,
d a r k - g r e y to pale-brown
( N 3 t o 5 YR 5/2).
tu
onderlying
1
Similar
D Cross s h a l e s .
Sandstone : Very calcareous
greyish-orange
(5 Y 7/2),
carbonaceoH
u so. r i z o n t a l l y
branchingburrowsonbedding
,
...
180
Thickness
Feet
DUensict r i p t i o n
Meters
p l a n e sR. e s i s t a n tp, o o r l y
s o r t e d ,v e r yf i n e - g r a i n e d
s u b a r k o s eL. a t e r a l l y
discontinuous.
Minor low
a n g l ec r o s s - l a m i n a ea tt o p
..........
..
TOTAL GALLUP SANDSTONE
0.6
81.3
-
24.8
TOTAL MEASUREDSECTION
81.3
24.8
of u n i t
I
0.2
MEASURED S E C T I O N 8
GallupSandstone
Measuredalongthenorthbank
o f AlamocitaCreek
ing i n t h e SE 1 / 4 S e c t i o n 30, T. 3 N . ,
1978 w i t hJ a c o bs t a f f
R.
start-
8 W. on August 1 0 ,
and Bruntoncompass.
mickness
Unit
Description
Feet
Meters
GALLUP SANDSTONE ( P a r t i a lS e c t i o n )
3
C o m p o sSi taen. d s t osnhea,l e ,
limestone :
S a n d s t o n e sa r e
b i o t u r b a t e d ,v a g u e l yl a m i n a t e d ,
poorly s o r t e d , f i n e - g r a i n e d
s u b a r k o s e sS. h a l e as r eg r e y
( N 6), s i l t y , o r g a n i c r i c h ,
slightlycalcareous,chunky
w e a t h e r i n gL.i m e s t o n easr e
elliposoidal, biolithites :
2
O s t r esao l e n i s c u s .
Coal
d e v e l o p el adt e r a l l y
........
Sandstone:
Medium-bedded,
s o r t e d ,t a b u l a rc r o s s s t r a t i f i e d ,r o o t - m o t t l e d
subarkoses.
Root c a s ta r e
l o n g ,c i r c u l a r ,b r a n c h i n g
15.4
4.7
182
Unit
Description
andmost
unit.
1
Meters
Thickness
Feet
common a t t o p o f
...............
10.1
3.1
23.2
7.1
Sandstone:
Thickly
bedded,
g r e y i s h - o r a n g ep i n k
7/2)
( 1 0 YR
, moderately sorted,
horizontally laminated,
slightlybioturbated,suba r k o sR
e .e s i s t a n t .
........
TOTAL GALLUP SANDSTONE
48.7
14.8
TOTAL S E C T I O N MEASURED
48.7
14.8
183
MEASURED S E C T I O N 9
Crevasse Canyon Formation
Measured along a n o r t h - s o u t h l i n e s t a r t i n g
1/4 S e c t i o n 3 1, T. 3 N.,
R.
8 W.
i n t h e SE
on August 21, 1 9 7 8 w i t h
B r u n t o nc o m p a s sa n dJ a c o bs t a f f .
mickness
Feet
D
Uensict r i p t i o n
Meters
CREVASSE CANYON FORMATION ( P a r t i a l S e c t i o n )
50
Sandstone :
Fining
upward
s e q u e n c e . !tko s u b u n i t s ; c o a r s e g r a i n e da t
base, w i t hc l a y
c l a s tc o n g l o m e r a t ea b o v e
e r o s i o n a ll o w e rc o n t a c t .
S t r u c t u r e l e s st oc r u d e l y
cross-stratified.
Upper
p a r t s of s u b u n i t s a r e f i n e grained, moderately sorted
microcross-laminated
rippled.
and
Moderately
calcareous.
49
,
............
S h aPl eo:oer lxyp o s e d ,
medium-
g r e y ( N 5), v e r y s l i g h t l y
calcareous , contains several
6 i n .t h i c kg r e y i s h - o l i v e
18.2
5.5
ption
184
Thickness
Feet
Unit
Meters
( 1 0 Y 4/2), s t r u c t u r e l e s s ,
.........
d si ar tnyd s t o n e s .
25.5
20.1
6.1
10.0
3.0
15.1
4.6
6.5
2.0
Two s u b u n i t s
Sandstone:
48
s e p a r a t e db ye r o s i o n a l
face.
90.2
sur-
Rock i s v e r ys i m i l a r
i n t e x t u r e , compositionand
t y p e andsequenceof
sedi-
m e n t a r ys t r u c t u r e st ou n i t
................
Covered.
47
Probably
shale.
.....
50.
46
Sandstone:
C u t b a os ev e r l a i n
clast
b ys m a l lp e b b l ec l a y
c o n g l o m e r a t eB. a sset r u c -
tureless , top cross-bedded and
ripple-laminated
, flaggy,
poorly
s o r t e dL. a r g be r o w n i s h grey(5
YR 4 / 1 )
c r e t i o n s common.
carbonatecon-
.........
S4a5n d s t o F
n er i: a bsliel ,t y ,
flaggy,moderatelysorted,
medium-grainedsubarkoseto
l i t h i cs u b a r k o s e .
Y e l l o w i s h - g r e(y5
44
Cut
base.
Y 8/4).
Sandstone:
Pale-greenishy e l l o w ( 1 0 Y 8 / 2 )F. i n e s
.....
185
Unit
Thickness
Feet
Description
upwardfrom
Meters
medium t of i n e -
g r a i n e d a t top.
0.1 f t
diameter c l a y c l a s t common
a t b a s eR
. o u g hc r o s s s t r a t i f i e da b
t a s eS
. lightly
calcareous.
43
............
8.6
2. 6
......
5. 8
1.8
.
30.9
9.4
(10 Y 8/2).
............
15.2
4.6
Sandstone:
C u t base.
15.1
4.6
10.1
3.1
0.7
0.2
25.8
8.2
Shale:
P o o r l ye x p o s e dp, a l e -
o l i v e ( 1 0 Y 6/2), s i l t y
42
SandstoneG
: e n e r a l l ya su n i t
41
S a n d s t o n eS: l i g h t l cya l c a r e o u s ,
50.
m a s s i v e ,f l a g g y ,p o o r l ys o r t e d ,
c l a y e ys u b a rk o s e .F i n e s
upward
,
c o n t a i n sh i c k o r y - n u t - s i z ec o n c r e t i oP
n sa .l e - g r e e n i s h - y e l l o w
40
above
39
As un i t
........... ...
ShaleS
: i l t y v, e r ys l i g h t l y
c a l c a r e o u ss p a r c er o o t - m o t t l
pale-olive
38
(10 Y 6/2)
i ng
I
.......
S a n d s t o n eF: i n e us p w a r dc, u t
b a s eT. r o u gchr o s s - s t r a t i f i e d
m o d e r a t e l ys o r t e du p p e rf i n e g r a i n e d ,c a l c a r e o u sc e m e n t .
37
S h a l eP: o o r l eyx p o s e d .
....
......
186
Thickness
Feet
Unit
36
Sandstone :
Meters
V e rcya l c a r e o u s ,
t r o u g hc r o s s - s t r a t i f i e d ,f i n e grained , moderately sorted.
Yellowish-grey
(5
35
Y 7/2).
.....
4.1
1.3
25.9
7.9
30.6
9.3
12.1
3.7
10.1
3.1
Shale:
Poorly
exposed.
Slope-
former.
C o n t a i n s a few d i r t y
s a n d s t o nien t e r b e d sG. r a d e s
34
'
............
t ou n i t
36.
Shale :
S i 1t y n
, oncalcareous
chunkyweathering
,
, carbonaceous.
C o n t a i n sn u m e r o u st h i n ,d i s c o n tinuous dirty light-olive green
.......
( 5 Y 5 / 2s)a n d s t o n e s .
Composite.
33
Sandstone
and
shale:
similar t o u n i t 34:
S h a l e sa r e
s a n d s t o n e s are 2.0-3.0
f t thick,
s t r u c t u r e l e s s and c o n t a i n wood
impressions.
Pale-greenishy e l l o w (10 Y 8/2)
32
Sandstone
:
.........
S1 i g h t l yc a l c a r e o u s
medium-grained moderately sorted
,
,
f i n e s upward t ou p p e rf i n e g r a i n e dc r o s s - l a m i n a t e dc o n c r e t i o n a r ys u b a r k o s e .
c l a yc l a s tc o n g l o m e r a t e
Cutbasewith
......
Feet
187
Thickness
Description
Unit
S h a l eP. a l e - o l i v e
31
( 1 0 Y 6/2),
....
s i lstlyi g, hctal lyc a r e o u s .
Sandstone:
30
18.0
5.5
Cut base
overlain
byclayclastconglomerate.
Lower p a r t ;m a s s i v e ,l o w e r
medium-grained, upper part
;
u p p e rf i n e - g r a i n e d ,c r o s s s t r a t i f i e dw i t hs m a l l
brown
( 5 YR 4/4) carbonateconcretions.
Very c a l c a r e o u tso p .
.......
......
32. . . . . . .
u n i t above.
Grades
to
29
Shale:
Poorly
exposed.
28
Sandstone:
27
Shale :
As u n i t
Light-green
25.0
7.6
36.5
11.1
10.0
3.0
15.1
4.6
5.1
1.5
17.0
5.2
, noncal-
c a r e o u s ,s i l t yc o n t a i n i n g
two
t h i ns t r u c t u r e l e s ss a n d s t o n e s
i n middle p a r t .
Sandstone:
26
..........
\
25
Shale:
24
Sandstone:
......
........
As u n i t 24.
As u n i t 23.
C u t b a s ew i t hc l a y
c l a s ct o n g l o m e r a t e F. i n e s
ward.
up-
Base is s t r u c t u r e l e s s
t o c r u d e l yt r o u g hc r o s s s t r a t i f i e d , medium-grained,
moderatelysorted,calcite
188
Unit
Thickness
Feet
Description
cemented s u b a r k o s e .
Meters
Upper
p a r t i s lowermedium-grained
pale-yellowish-orange
8/4)
( 1 0 YR
cross-
and h a s s m a l ls c a l e
..
l a m i n a eG
. r a d e tsou n iat b o v e .
23
S h a l eO
: l i v eg r e e n
12.1
3.7
15.5
4.7
(10 Y 6/2),
s i l t yn,o n c a l c a r e o u sC. o n t a i n s
a 0.5 f t t h i c kc o a l
seam.
.....
.....
22
C o v e r e dP. r o b a b l syh a l e .
21
S h a l eS: i l t ym, o d e r a t e - y e l l o w i s h -
5.1
1.5
10.0
3.0
12.0
3.7
g r e e n (10 Y 7 / 4 ) n o n c a l c a r e o u s ,
c o n t a i n so n e0 . 5
f t t h i c k , mod-
erately sorted
, calcareous very
...
f i n e - g r a i n e ds a n d s t o n ea tt o p
20
Sandstone :
C u t b a s ew i t hc l a y
up-
c l a s t cong 1omerate.
Fines
ward.
Med i um-grained, very
calcareous I moderately sorted
,
medium-gra i ned subarkose.
!Ihinly
laminated.
Pale-olive
weathers
brown.
19
( 1 0 Y 6/2)
..........
Shale:
Moderate-greenish-yellow
( 1 0 Y 7/2)
, silty, noncalcareous,
c o n t a i n s r a r e o n et ot h r e ei n c h
diameter g r e y i s h - o l i v e ( 1 0 Y 4 / 2 ) ,
ption
189
Thickness
Feet
Unit
Meters
brownishblackweatheringirons t o n ec o n c r e t i o n s
s t o nien t e r b e d s
and t h i ns a n d -
..........
28.9
8.8
........
7.8
2.4
............
20.1
6.1
7.0
2.1
13.2
4.0
9.5
2.9
, very
18
Sandstone:
Poorly
exposed
( 1 0 YR 8/2)
p a l eo r a n g e
c a l c a r e o u cs e m e n t .
4/1)
, flaggy,
Brown ( 5 YR
w e a t h e r i ntgo p
S1 h7 a P
l eo: o relxyp o s ecdo,n cretionary.
16
, medium
Shale:
Poorly
exposed
g r e y ( N 5 ) ,c o n t a i n i n g
a thin
v e r ys a n d yl i m e s t o n ew i t hc o n e i n - c o n es t r u c t u r e sn e a rt o p ,
l a t e r a l lcyo a l l y .
.........
1S5h a l eP:o o r leyx p o s e d
one0.5
, contains
, f t t h i c kf i n e - g r a i n e d
clayey,poorlysortedlithic a r e n i t e ;r i p p l e du p p e r
surface,
common i n v e r t e b r a t e t r a c k s
and
t r a iPl sa.l e - g r e e n i s h - o l i v e
( 5 Y 5/4)
14
.............
S a n d s t oFn lea: g sglyi g
, htly
c a l c a r e o u s ,c l a y e y ,c r u d e l y
c r o s s - s t r a t i f i e dT. h i lni m e y
zones.
Brown ( 5 YR 4 / 1 ) .
.....
190
Thickness
Feet
D
Uensict r i p t i o n
13
Meters
S h aSl ei l:m
t yo, d e r a t e - o l i v e
brown ( 5 Y 4 / 4 )
homogenous,
wood impressionsandsmall
c a r b o n a ct eo n c r e t i o n s
12'
.......
2.1
0.6
2.1
0.6
4.9
1.5
.
8.0
2.4
.........
25.2
7.7
Sandstone:
Light-brown
( 5 YR
5/6) , f i n e - g r a i n e d v e r y
cal-
careous.
Grades tsoa n d y
l i m e s t o n e a t top.Karren
11
..............
Shale:
Poorly
exposed.
......
10
S a n d s t o nbew
: pear rctr;o s s -
surface
s t r a t i f i e d , thin-bedded
, flaggy,
non t o m o d e r a t e l y c a l c a r e o u s ,
fine-grained , clayey, moderateyellowish-brown
(10 YR 5 / 4 ) .
Upper p a r t ; v e r y s a n d y l i m e s t o n e ,
p a l e o r a n g e (10 YR 8 / 2 )c o n t a i n -
i n ga n g u l a rq u a r t zg r a i n s ,c l a y
c l a s t s wood and d a r kc a r b o n a t e
concretions.
9
S h a lPeo: o rel xy p o s ecda,r bonaceous,
a
Wood i s s i l i c i f i e d .
(N 4 ) .
Sandstone : Weak bench-former
noncalcareous subar kose
,
, poorly
191
Unit
Thickness
Feet
Description
,
s o r t e dv a g u e l yc r o s s - s t r a t i f i e d
7
. . . . . . . . .2.5. . . .
S h a l eP: o o r l eyx p o s e d .
......
6
Sandstone :
c u t base.
4/4)
Moderate-brown
Meters
8.3
LO. 3
3.1
6.9
2.1
6.5
2.0
5.8
1.8
10.4
3.2
( 5 YR
,
weathering, fine-grained
, weakly indurated ,
very calcareous , angular grains.
Subar kose t o l i t h i c a r e n i t e , c u t
poorly sorted
b a s ew i t hc l a y
.
.....
c l a s t conglomerate
5
Covered.
Probably
shale.
4
Sandstone :
Fines
upward.
Upper
,
fine- to lower medium-grained
subarkose I moderately sorted,
crudelycross-stratified,
wood
impressions , sparce plecypods.
C u t base w i t h c l a y c l a s t
conglomerate.
3
...........
Shale:
Poorly
exposed,
Moderate
o l i v e (5 Y 4/4)
c o n t a i n i n g small
,
concretions ,
noncalcareous
verycarbonaceousneartop
(N 4)
..
m i n o rt h i ng r e e n i s hs a n d s t o n e s .
2
,
S a n d s t o n eC
: u bt a s ew i t hc l a y
c l a s t conglomerate.
Fining
up-
ward s e q u e n c e , v e r y c o a r s e -
to
ption
192
Thickness
Feet
Unit
coarse-grained
Meters
, moderately sorted.
Upper s u r f a c ed i p - s l o p ef o r m e r .
T r a c ef o s s i l so nb o t t o m so ft h i n
s a n d s t o n e s a t t o p of u n i t .U n i t
is t r a c e a b l e o v e r e n t i r e
D Cross
q u a d r a n g l eC.o n c r e t i o n a r y ,
calcareous.
1
nbn-
............
27.1
8.3
53.0
16.1
TOTAL CREVASSE CANYON
793.6
241.9
TOTAL SECTION MEASURED
793.6
241.9
Composite.
Sandstone
and s h a l e :
G r a d a t i o n a lt oG a l l u pS a n d s t o n e .
Sandstones are y e l l o w i s h - w h i t e
,
f i n e - g r a i n e dm o d e r a t e l yt op o o r l y
sorted subar koses
, with
small
ripples and
c r o s s - l a m i n a eS. h a l e s
are p o o r l ye x p o s e d ,s i l t y ,
car-
bonaceous
, andhave
tracks.
L a t e r a l l y coal seams
common f e e d i n g
...
193
MEASURED SECTION 1 0
Baca Formation
Measuredalong
t h e NE 1 / 4 ,
a s o u t h w e s tt r e n d i n gl i n es t a r t i n gi n
NW 1 / 4 S e c t i o n3 6 ,
T. 3 N . ,
R.
8 W. on October
3r1978withJacobstaffandBruntoncompass.
Thickness
Feet
D
Uensict r i p t i o n
Meters
BACA FORMATION ( P a r t i a l S e c t i o n )
46
Shale:
Moderate-red
( 5 R 5/4)
silty, slightly calcareous,
w i t hv e r ym i n o rt h i ns a n d y
45
...............
Sandstone: As u n i t 43. . . . . . .
44
Sandstone:
zones
G r e y i s h - p i n k( 5
8.0
2.4
7.1
2.2
....
3.5
1.1
..
10.2
R 8/2),
m o d e r a t e l ys o r t e dv e r ys l i g h t l y
calcareous , friable , fine- to
medium-grained ar kose.Massive
at base
, horizontally laminated
a t t o pG. r a d etsuon i t
45.
S4a3n d s t o n
S ei l:gt yr e, y i s h - p i n k
( 5 R 8/2)
I
f r i a b l es l i g h t l y
calcareous , f i n e - g r a i n e da r k o s e
42
S a n d s t oS
nh
e i:arrrpe g u l a r
cutbasewithclay
c l a s t con-
glomerate.
Medium-grained,
3.1
194
Unit
Thickness
Feet
Description
Meters
moderatelysortedlslightly
calcareous , arkose
, greyish-
p i n k ( 5 R 8 / 2 ) ,v a g u e l y
l a m i n a t e d or cross-bedded,
laminae.
minor
contoured
Fines
upward t ou p p e rf i n e - g r a i n e d
cross-bedded
sandstone.
Grades
............
t o u n i t 43.
41
S a n d s t o n e :S h a r pc u tb a s e
basal conglomerate
12.9
3.9
4.0
1.2
3.6
1.1
15.1
4.6
4.2
1.3
, thick-
bedded
, massive, moderately
sorted
I
slightly calcareous
...
rare l i g h t -
Shale:Verysandy,
r e d( 5
9.1
with
medium c o a r s e - g r a i n e da r k o s e .
40
30.0
ft
R 6/6), 0.1-0.5
t h i c ks a n d s t o n ei n t e r b e d s
As u n i t 17.
39
Sandstone:
38
S h a l e :L i g h t - r e d( 5
.....
......
R 6/6) ,
s i l t y ,w i t hi n t e r b e d s
of t h i n ,
0.1 t o 0 . 2 f t t h i c k f l a g g y
sandstone
37
.............
Sandstone:Poorexposure
f ine-grained
I
upper
, massive , f r i a b l e
c a l i c h en o d u l e s
a t top.
I
......
195
Unit
36
*
Thickness
Feet
Description
Covered.
Note :
Meters
Red s h a l e sl a t e r a l l y .
Common r o u n d e dr e s i s t a t e
pebbles l i t t e r s l o p ef r o mu n i t
35 through 40.
Source n o t
determined.
35
Sandstone :
Medium-bedded,
massive a t b a s e c o n t a c t n o t
Upper part is h o r i -
exposed.
z o n t a l l y laminated t o l o wa n g l e
c r o s s - l a m i n a t eMdo. d e r a t e l y
sorted, calcareous
, medium-
t oc o a r s e - g r a i n e ds u b a r k o s e .
Upper few f e e t are i n t e r b e d d e d
s a n d s t o n ea n ds h a l e
u n i t 34
34
similar t o
..............
10.0
3.0
34.1
10.4
16.9
5.1
Composite.
Sandstone
and
shale:
S e c t i o np o o r l ye x p o s e dS. a n d s t o n e s
are w h i t e (N 9 ) , l e n t i c u l a r , 0.35 . 0 f t t h i c k andmorenumerous
toward top of u n i t , s h a l e s
are
................
Covered.
L a t e r a l l y red s h a l e s . . .
silty
33
I
32
Sandstone:
Cut base w i t hc l a y
c l a s t conglomerate.
Base
t h i c k -t ot h i n - b e d d e d ,m a s s i v e
is
196
Unit
Thickness
Feet
Description
Meters
t o low a n g l e c r o s s - l a m i n a t e d ,
moderately sorted medium-grained
arkose,slightlycalcareous.
unit
F i n e su p w a r d ,g r a d e st o
.......
a b o v eb yi n t e r b e d d i n g
31
Shale :
22.0
6.7
9.1
2.8
15.9
4.8
4.8
1.5
8.9
2.7
28.8
8.9
M o d e r a t e - t o - l i g h tr e d
( 5 R 5/4 t o 5 R 6/6), s i l t y ,
structureless
30
...........
SandstoneT
: h r e eb e d sa su n i t
29 s e p a r a t e d by0.5-1.0
breaks.
29
f t shale
..............
Sandstone:
Sharp
f l a tb a s a l
c o n t a c tT. h i n l lya m i n a t e d ,
low a n g l e c r o s s - l a m i n a t e d , f i n e g r a i n e d ,c l a y e ya r k o s ew i t h
unit
s h a l ep a r t i n gG
. r a d e tso
above
28
27
...............
S h a l eC
: l e a n l, i g h t - r e d
6/6), s l i g h t l cy a l c a r e o u s
.....
C o v e r e dL. a t e r a l l ys h a l e
as
u n i t above.
26
(5 R
............
S a n d s t o n eF:i n e - g r a i n eadr k o s e ,
g r e y i s h - p i n k( 5
R 8 / 2 ) , moder-
a t e l yc a l c a r e o u s ,t a b u l a rc r o s s s t r a t i f i e di n
sets t h a t a r e
ption
197
Thickness
Feet
Unit
e i g h ti n c h e s
a buonvi et .
thick.
Shale:
24
S a n d s t o nSeh: acrbu
pat s e ,
As
Grades t o
............
1u7n.i t
........
25
Meters
7.5
2.3
1.2
0.4
6.3
1.7
19.1
5.8
4.0
1.2
5.8
1.8
t a b u l a r and h o r i z o n t a l l y lamin a t e d ,s l i g h t l yc a l c a r e o u s ,
to
m o d e r a t e l ys o r t e d ,f i n e medium-grainedgreyish-pink
( 5 R 8/2), a r k o s e w i t h minor
...........
s h a bl er e a k s .
23
Shale :
D o m i n a t e l iyg h t - r e d ,
s i l t y ( 5 R 6/6) f l a g g y f i n e g r a i n e ds a n d s t o n e s
s t o n e s common
22
Sandstone:
and s i l t -
...........
White ( N 9 ) , resis-
t a n t ,c a l c a r e o u s ,m e d i u m - g r a i n e d ,
s o r t e ad r k o s eT. a b u l a r
l a m i n a t e di n
cross-
sets 0.3 f t t h i c k ,
g r a d e st ou n i ta b o v eb yi n t e r bedding
S h2a1l e :
*
..............
1u7n.i t
........
As
Crossed small f a u l t , d i s p l a c e m e n t
unknown.
ption
198
Thickness
Feet
Unit
20
Meters
S a n d s t o nPeo: o rel xy p o s ecdu, t
b a s e , s t r u c t u r e l e s s , ar kose ,
f i n e s upward.
...........
1. 6
5.5
1.7
12.9
3.9
4.9
1.5
30.1
9.2
20.0
6.1
As u n i t 1 7 , g r a d e s
1S9h a l e :
laterally to siltstone
sandstone
S
1 8a n d s t o n e :
17
5.2
and
.............
As u n i t 1 6 . . . . . . .
Shale:
Light-red
( 5 R 6/6),
slightlycalcareous,silty,
....
s l o p e - f o r m esrt,r u c t u r e l e s s
16
cut
Sandstone:
Fines
upward,
basewithclayclastconglomerate.
Base is w h i t e ( N 9 )
, m a s s i v et o
horizontally laminated,
a t e l ys o r t e da r k o s e .
moder-
Upper. p a r t
i s t h i n l yl a m i n a t e dw i t h
rare
I
rippled
z o n e sP. a r t i n g
linkat i o n s common.
above
15
Grades t o unkt
...............
Composite.
Sandstone
and
shale
:
S a n d s t o n e sa r et h i n l yb e d d e d ,
light-red
( 5 R 6 / 6 ) , moder-
ately sorted
S h a l e sa r e
t ou n i t
14.
, calcareous.
a s u n i t 17.
Grades
............
on
199
Thickness
Feet
Unit
14
Sandstone : M o d e r a t e ltypoo o r l y
, light
sorted, medium-grained
pink, arkose.
Low a n g l ec r o s s -
...
21.5
6.5
...........
15.9
11.4
15.8
4.
20.2
6.2
12.0
3.7
s t r a t i f i e d ,g r a d e st ou n i t1 5
13
Meters
Shale:
As u n i t 17:
numerous
thin sandstone interbeds
,
t h i c k e s t i s 2.0 f t , s a n d s t o n e s
increase i n number v e r t i c a l l y ,
14.
g r a d e st o
12
Sandstone:
Medium- ft ion e -
grained
arkose.
andbelow
Grades above
t ob o u n d i n gu n i t s ,
middlepart
i s medium-bedded
and h o r i z o n t a l l y l a m i n a t e d
.
t o p andbottom
less
11
are s t r u c t u r e -
andthin-bedded
Shale:
10
.......
a
As u n i t 1 5 w i t h
c a l i c h ec o n c r e t i o n si n
horizons
,
some
..............
Sandstone:
Cut
base w i tchl a y
clast conglomerate, very calcareous , coarse-grained arkose.
F i n e s upward i n t o inkerbedded
s a n d s t o n e s and s h a l e s .
Base
is low a n g l e c r o s s - s t r a t i f i e d
...
200
Thickness
et
Unit
9
Meters
Description
Sandstone:Light-red
( 5 R 6/6)
,
, poorly sorted,
m o d e r a t e l y calcareous , d i r t y ,
thin-bedded , c r o s s - s t r a t i f i e d
fine-grained
..
19.0
5.8
........
45.0
13.7
micaeous a r k oFsiuenp.ews a r d .
8
C o v e r e dL. a t e r a l liyn t e r b e d d e d
sandsto
as hn adel e
7
Sandstone : M o d e r a t e l ys o r t e d ,
calcareous, friable
grained
, cross-stratified
a r k o s eC
. ub
t ase,
former.
6
( 1 0 R 8/2)
weak bench-
........
..............
Crossed small f a u l t - d i s p l a c e m e n t
unknown.
5
5.0
1.5
15.4
4.7
Shale:Poorlyexposed,vague
bedding
*
, fine-
C o n g l o m e r a t eS: l i g h t l ye r o s i o n a l
base.
Dip-slope
former,
brown
( 5 YR 3/4)
, withrounded,compact,
o re l o n g a t e ,c l a s t
u p t o 0.5 f t
d i a m e t e rV
. a g u e l yl a m i n a t e d
and
c r o s s - s t r a t i f i eM
d .o d e r a t e l y
c a l c a r e o u s , c l a s t s a r er a n d o m l y
, limestone ,
arkose , s c h i s t , q u a r t z i t e .
oriented quartz, chert
granite,
tion
201
Thickness
Meters
Unit
Minor i n t e r b e d d e dc r o s s - s t r a t i f i e d
i s p r o b a b l yt h e
a r k o s e sU
. nit
b a s e of G i v e n sm e a s u r e ds e c t i o n
........
15.8
4.8
..
13.9
4.2
.........
15.2
4.6
7.6
2.3
f o r Baca Formation.
4
Sandstone :
8/4)
Greyish-yellow
, f r i a b l e , moderately
(5 Y
cal-
c a r e o u s ,m a s s i v et oc r u d e l y
a t base.
cross-stratified,
Top
is moderately sorted
, calcareous,
indurated
T.a b u l a r
cross-
s t r a t i f i e dg r e e n i s h - y e l l o w ,
m o d e r aitne dl yu r as u
t ebda r k o s e .
3
Covered.
Grassy
similar utnoi t
2
Sandstone :
flat.
2
May b e
Yellowish-grey
8/1) , medium-grained
(5 Y
, moderately
sorted,slightlycalcareoussuba r k o s e .S h a r pc u tb a s ew i t hc l a y
c l a s t c o n g l o m e r a t eB
. o t ht a b u l a r
and h o r i z o n t a l l a m i n a t i o n s p r e s e n t .
F i n e s upward
, underlying shale
are b l e a c h e dw h i t e .
c ot avcetr e d .
1
Upper con-
...........
Composite.
Sandstone
and
shale:
S a n d s t o n e s are v e r y f i n e - g r a i n e d ,
ption
202
Thickness
Feet
Unit
slightly calcareous, silty,
h e m a t i t se t a i n e dB. o t t o m as r e
e r o s i o n a l ,i r r e g u l a r
andhave
i r o n s t o n el a y e r si nu n d e r l y i n g
shales.
Thin-bedded
.
are dominatelithology
Shales
and a r e ;
variegated, vaguely laminated
s l i g h t l y t o noncalcareous
,
, and
s a n d yi na r e a s C
. o l o r si n c l u d e
h u e s of y e l l o w , r e d
g r e e ng r e y ,o l i v e .
, lavender,
0.1-0.2
f t
d i a m e t e rh e m a t i t en o d u l e sa n d
l a y e r s and 1 . 0 f t d i a m e t e r carb o n actoen c r e t i oan
arb
seu n d a n t
TOTAL BACA FORMATION
TOTAL MEASURED S E C T I O N
..
45.0
13.7
194.8 638.9
63194.8
8.9
Meters
203
MEASURED
SECTION
11
Conglomerate of Rock Tank Canyon
a west t o e a s t t r e n d i n g l i n e s t a r t i n g i n
Measuredalong
t h ec r e e k
8 W.,
bed i nt h e
Nw 1 / 4 S e c t i o n3 4 ,
SE 1 / 4 ,
3 N.,
R.
o nJ u l y1 8 ,1 9 7 8w i t hJ a c o bs t a f €a n dB r u n t o nc o m p a s s .
Thickness
Feet
D
Uensi ct r i p t i o n
CONGLOMERATE OF ROCK TANK CANYON
3
T.
Composite.
Conglomerate
and
of u n i t
s a n d s t o n e :B a s a lp a r t
is p e b b l ec o n g l o m e r a t e sa s
u n i t 1.
F i n e s upward t o
i n t e r b e d d e dp i n k i s h - g r e y
( 5 YR 8/1)
I
cross-stratified,
coarse-grained
moderately
I
topoorlysorted,voianic a r e n i t eMs .o d e r a t e l y
i n d u r a t e dw i t h
calcite.
Interbeddedconglomerates
a r e i nb e d s0 . 5 - 3 . 0
diameterand
ft in
cross-
stratified : tabular.
C l a s t a r e e x c l u s i v e l y of
v o l c a n iocr i g i n' I. h i n
Meters
204
Unit
Thickness
Feet
B s c r i p t ion
c a l i c h ez o n e sa n d
Meters
mud-
cracked s h a l e o c c u r
. . . . . . . . 225.3
t h r o u g h o ut htuen i t
2
Sandstone :
68.7
Verypebbly
c o a r s e - g r a i n e dv o l c a r e n i t e .
Crudely medium- t o t h i c k bedded.
Dominately
......
h o r i z o n t a l l yl a m i n a t e d .
3
(N 6 t o
Conglomerate:
Grey
N 8 ) , abundant, cut-and-
f i l l s t r u c t u r e s , wavy-
l e n t i c u l a r b e d s , well s t r a t i fied
, bothtabular
and h o r i -
z o n t a ll a m i n a t i o n sp r e s e n t .
Minor s a n d s t o n e st h a ta r e
cross-stratified
and grade
I
v e r t i c a l l y and l a t e r a l l y t o
conglomerates.
Medium-bedded
Maximum c l a s t s i z e2 . 5
ft,
average is less than 0 . 1 f t ,
, subrounded t o
subangular , r h y o l i t i c t o
imbricated
latite tuffs, very minor
basalts.
Trace l i m e s t o n e
and s a n d s t o n e as c l a s t s .
.
22.0
6.7
205
Th i c kne ss
Unit
Feet
Description
Meters
P l a t y t o compact s h a p e .
Sharp erosional c o n t a c t . w i t h
Baca Formation.
..........
TOTAL CONGLOMERATE OF
ROCK TANK CANYON
47.1
89.8 -4 294
TOTAL MEASURED SECTION 8 9 . 8
294.4
14.4
ption
206
MEASURED SECTION 1 2
MesaverdeUndivided--Tres
area.
J o r n a d ad e lM u e r t o
g l e rS e c t i o n
5 , T.
3 S.,
R.
1 9 7 8w i t hJ a c o bs t a f fa n d
Hermanos Sandstone
BustosWell7-1/2'quadran-
3 E.
Measured on September 15,
Abney l e v e l b y
Tabet, G. Massingilland
B.
Robinson, D.
S. Hook.
Thickness
Feet
Unit
Meters
MESAVERDE UNDIVIDED ( P a r t i a l S e c t i o n )
Sandstone
37
Fine-grained
:
moderately sorted
I
very
c a l c a r e o u s , subangular
quartz grains, minor
.
c h e r t and opaques
(10 R 8/2 to 10 YR 7/4).
Medium-bedded w i t h
p a r a l l e lp l a n a r
cross-
l a m i n a t i o nBsa. s a l
c o n t a c t s h a r p and
Undulatory.
............
TOTAL MESAVERDE
19.5
5.9
19.5
5.9
15.0
4.6
D CROSS TONGUE
36
Shale :
Noncalcareous
( 5 Y 6/2)
, fissile
.............
207
Unit
35
Thickness
Feet
Description
Meters
Limestone : M i c r i tceo n c r e t i o n s ,
( 5 Y 8/4) c o n t a i n i n g Lopha
sannionis
34
Shale:
Noncalcareous,
(N 6 )
33
.............
1.0
0.3
20.5
6.3
0.5
0.1
15.0
4.6
18.0
5.5
47.0
14.3
44.9
13.7
0.1
0.1
fissile,
...............
SandstoC
n ea:l c a r e n istiel ,t y ,
t h i n l yl a m i n a t e d ,b u r r o w e d ,w i t h
g r a d a t i o n a lt o pa n db o t t o m ,
( 5 Y 7/2)
32
.............
S h aSl ei l: t y ,
fissile,
( 5 YR 6 / 1 ) .
31
Shale:
Noncalcareous
( 5 Y 5/1)
30
............
Shale :
, fissile,
.............
Fissile, contains
n u m e r o u sl i m e s t o n ec o n c r e t i o n s
e l o n g a t et ob e d d i n gp l a n e ,
f t by5.0
29
f t , ( 5 Y 5/1)
2.0
......
S h aNl eo:n c a l c a r e ofui s ,s i l e ,
containsthinsiltstone
beds a t
20.0 f t , 30.0 f t I and 34.0 f t
above base o fu n i t .S i l t s t o n e s
a r e l a m i n a t e d a n dc a l c a r e o u s .
28
Limestone:
27
Shale:
Micrite , (10 YR
...
7/4). .
As u n i t 29, t h i n c a l -
c a r e n i t e beds a t 128.0 f t , 1 3 0 . 0
208
Thickness
Unit
f t and132.0
unit.
26
Feet
Description
f t abovebase
of
. . . . . . . . . . . . . . . 137.0
Limestone :
Meters
41.8
Concretionary
micrite nodulesformalmost
c o m p l e tbee dB. a c u l i t e s
yokoyami and
25
Shale :
- ...
P r i o n o c y c l u s sp.
Noncalcareous
0.5
0.1
42.5
13.0
0.2
0.1
9.7
3.0
0.3
0.1
, fissile,
(5 Y 5/1), c o n t a i n i n g s i x i n c h
m i c r i t e c o n c r e t i o n sa t
26.0 f t and32.0
23.0 f t ,
f t abovebase.
C o n c r e t i o n sa r es i m i l a rt o
u n i t2 6 .
18
.............
S a n d s t o n eS: i l t cy a l c a r e n i t e ,
f o s s i l i f e r o u s , (10 YR 7/2)
c o n t a i n sS: c a p h i t efse r r o n e n s i s ,
Prionocycluswyomingensis
17
Shale:
Noncalcareous,
fissile,
.........
S a n d s t o n eC
: alcarenite
as 33 . . .
c l e a n ,( 5
16
.....
Y 6/1).
c o n t a i n sS: c a p h i t i e w
s arreni
andPrionocycluswyomingensis
15
Shale:Verypoorlyexposed
TOTAL D CROSS TONGUE
. . . . -8.5
360.7
2.6
110.0
ion
20 9
Thickness
unit
TRES HERMANOS SANDSTONE
14
Sandstone:
Coarsening
upward
sequence.
Very
fine-grained
a t top.
a tb a s e ,f i n e - g r a i n e d
M o d e r a t e l ys o r t e ds u b a r k o s e
( 5 Y 8/1)
,
7 YR 8 / 2 ,
1 0 YR 8 / 4 ,
Upper s u r f a c e
1 0 YR 7 / 6 ) .
r i p p l e da n db i o t u r b a t e d .
.........
M a s s i v e l y bedded.
13
Shale :
41.0
12.5
35.0
10.7
15.0
4.6
S i l t y, f i s s i l e ,
abundant gypsum c r y s t a l s ,
(N 5 t o N 7).
Septarian
concretionscontaining
f o s s i l st h r o u g h o u tu n i t .
Grades t ou n i ta b o v e .
Lopha b e l l a p l i c a t a and
-
Ostrea s p .
12
............
Composite.
Sandstone
and
I
s h a l e :s a n d s t o n e s
are f i n e -
, moderately
careous , 0.3-1.0 f t
grained
andcomprise
calthick
50% of t h e u n i t .
S h a l e s a r e poorly exposed
11
Sandstone:
Base is t h i c k -
bedded andcross-laminated;
.....
ption
210
Thickness
Feet
Unit
Meters
t o p is h o r i z o n t a l l y l a m i n a t e d .
medium-
F i n e s upwardfrom
g r a i n e dt of i n e - g r a i n e d .
Moderately calcareous,
wood impressionsandconcretionary (large)
, also
..
7.5
2.3
..........
4. 0
1.2
20.0
6.1
5.0
1.5
wood ( p e t r i f i e d ) .
10
Shale :
Fissile
( 1 0 YR 8 / 2 ) .
, noncalto
c a r e o u s ,s i l t y ,g r a d e s
u n i t 9, s h a r p c o n t a c t w i t h
u n i t 10.
9
(N 6)
Sandstone:
Light-grey
(N 4 )
,
p o o r l y s o r t e d , a n g u l a rs u b a r k o s e .
T h i c k - b e d d e d ,t a b u l a rc r o s s s t r a t i f i e d w i t hs p a r c ep e t r i f i e d
wood and dark-brown
( 5 YFz 2/4)
c a r b o n a t ec o n c r e t i o n st h a t
up t o 4 . 0 f t t h i c ka n d
are
20.0 f t
l o n gn e a rb a s e S
. h a r pi r r e g u l a r
b a s acl o n t a c t
0
Sandstone :
...........
V e fr iyn e - g r a i n e d ,
l o c a l l ys i l t s t o n e
I
and
mudstone.
S a n d s t oN
n eo:n c a l c a r e ofui n
s ,e g r a i n e d , medium-bedded,subarkose,
( 1 0 YR 7 / 4 ) ,
l o wa n g l ep l a n a r
..
211
Thickness
Feet
D
Uensi ct r i p t i o n
cross-laminated
and m o t t l e d or
structureless.
Minor
knobby
........
Ophiomorphaburrows
6
Meters
5.0
1.5
5.0
1.5
0.9
0.3
12.0
3.7
4.0
1.2
5.0
1.5
S h aSl ei l:m
t yi ,c a c e o u s ,
f i s s i l e , s l i g h t l y t o noncalcareous.
5
............
Sandstone:
Very
fine-grained,
silty, slightly calcareous,
moderately bioturbated
( 1 0 YR 7/4)
,
............
......
4
Shale:
Poorly
exposed.
3
Sandstone : S l i g h t l yc a l c a r e o u s
,
fine- to medium-grained, moderately sorted
, medium-bedded,
t a b u l a rc r o s s - s t r a t i f i e ds u b a r k o s e , (10 YR 7 / 4 )
2
Shale:
....... .
F i s s i l e , ( N 6) w i t h a
few t h i n f i n e - g r a i n e d s a n d s t o n e
interbeds
1
Sandstone:
bedded
.............
Medium- t o t h i c k -
, s t r u c t u r e l e s s , mottled
c r o s s - l a m i n a t e dL. o c a l l y
or
cuspate
r i p p l e s ,m o d e r a t e l ys o r t e d ,f i n e t o medium-grained
, subarkose.
Horizontal laminations
a t base ,
212
Thickness
Feet
DUensict r i p t i o n
t a b u l a rc r o s s - l a m i n a t i o n sn e a r
top.
Minor c l a y c l a s t c o n g l o m e r a t e s
and
Meters
c o n c r e t i o n st h r o u g h o u tu n i t .
F o s s i l i f e r o u s ;C o l l i g n o n i c e r a s
w o o l l a rw
i oollgari.
....., ..
79.0
24.1
TOTAL TRES
HERMANOS
238.4
72.7
TOTAL MEASURED SECTION
618.6
188.6
I
213
VITA
Bob Russell Robinson was b o r ni nL a u r e l ,
Doris andJamesRobinson.
November 2 1 , 1949, t h es o no f
After graduationfromVidor
e n t e r e dc o l l e g e
hereceived
Mississippi,
High SchoolinVidor,Texas,he
a t Lamar U n i v e r s i t y i n Beaumont, Texas where
H e was
a BachelorofSciencedegreein1972.
employed for ninemonthsin1973withExplorationLogging
U.S.A.
a s a well-site g e o l o g i s t b e f o r e e n t e r i n g t h e G r a d u a t e
School a t t h eU n i v e r s i t y
r e c e i v i n gh i s
o f Houston,Houston,Texas.
Master o fS c i e n c ed e g r e ei n
began work o n h i s
Upon
May, 1 9 7 6 , he
Doctorate of G e o l o g i c a lS c i e n c e s
U n i v e r s i t y of T e x a s a t E l Paso.Whileworkingon
a t the
h i sd e g r e e
h eh a sh e l df a c u l t yp o s i t i o n si nt h eD e p a r t m e n to fG e o l o g y
a t New Mexico S t a t eU n i v e r s i t y( S p r i n g r1 9 7 9 ) ;E a s t e r n
Mexico University(1979-80);and
MiningandTechnology
Permanent
address:
New
New Mexico I n s t i t u t e of
(Summer , 1 9 8 0 ) .
Box 233
Vidor , Texas77662