FACIES
MOSAICOF THE
UPPER
YATES
AND LOWER TANSILL FORMATIONS(UPPER PERMIAN),
RATTLESNAKE CANYON, GUADATAJPE XOUNTAINS,
XEWMEXICO
'
..
BY
-~
...
"~
ARTHUR H. SCHWARTZ
"
"A thesis submitted in partial fulfillment of the
requirements for the degree of
MASTER OF SCIENCE
(Geology)
at the
UNIVERSITY OF WISCONSIN-"AJJISON
1981
I
ii
ABSTRACT
This study i s focused on
45 m of s t r a t i g r a p h i c i n t e r v a l c e n t e r e d
around the contact between the upper
Yates and
P e h a n , Guadalupianage
S i x s t r a t i g r a p h i c s e c t i o n s were measured i n
TansillFormations.
R a t t l e s n a k e Canyon, which t r e n d s p e r p e n d i c u l a r t o t h e C a p i t a n
ment.
Escarp-
The o b j e c t i v e of this'.study was todetermine,throughstudying
a n d - t r a c i n g i n d i v i d u a l b e d s , che . d e t a i l e d f a c i e s mosa5c of a l i m i t e d
s t r a t i g r a p h i c i n t e r v a l of c ~ r b o n a t e s h e l f s t r a t a a d j a c e n t t o t h e
CapitanLimestone.
The s t u d y a r e a
2 112
encompasses t h e mostbasinward
km of s h e l f s t r a t a , a n a r e a
of a b r u p t f a c i e s c h a n g e s r e l a t e d t o d i f f e r -
ences i n energy,depth,and
water s a l i n i t y v a r i a t i o n .
The c a r b o n a t e s h e l f c a n b e s u b d i v i d e d i n t o f i v e f a c i e s
of a
marginal mound p r o f i l e ; i n a s h e l f w a r d d i r e c t i o n t h e f a c i e s a r e :
2) o u t e r s h e l f ,
1) shelfedge,
5 ) evaporiteshelf.
Dunham (1972).
of t h e s t u d y
3) shel'f c r e s t , 4 ) i n n e r s h e l f ,
and
The marginal mound p r o f i l e was f i r s t recognized by
The CapitanLimestonecomprisestheshelfedge.
area c o m p r i s e t h e o u t e r s h e l f , s h e l f c r e s t ,
Rocks
and i n n e r
shelf.
Eight rock types
graintype,grain
texture.
were d i f f e r e n t i a t e d u s i n g several v a r i a b l e s ,
s i z e , grain abundance, rock fabric, and depositionel
The rocktypesare:
1) s k e l e t a lg r a i n s t o n e ,
2) n o n s k e l e t a l
g r a i n s t o n e , 3) f e n e s t r a ln o n s k e l e t a l - s k e l e t a lp a c k s t o n e - g r a i n s t o n e ,
4 ) f e n e s t r a ln o n s k e l e t a lp a c k s t o n e - g r a i n s t o n e ,
g r a i n s t o n e , 6) peloidmudstone-wackestone,
5 ) p i s o l i t i c packstone-
7) s i l i c i c l a s t i c s a n d s t o n e ,
iii
8) s i l i c i c l a s t i c - r i c h p e l o i d
The o u t e r s h e l f
wackestone.
strata are composed of Rock Types 1 and 2.
These
rocks consist of well s o r t e d , well rounded g r a i n s with abundant.cross
laminationandparallellamination.Evidenceof
The o u t e r s h e l f
emergence is absent.
strata are i n t e r p r e t e d t o h a v e b e e n d e p o s i t e d
in a
s u b t i d a l , non-emergent carbonate sand shoal environment.
The s h e l f . crest strata are composed of Rock Types 3 , 4 , and 5.
,
and p i s o l i t e s are t h e predomi-
Fenestralfabric,sheetcracks,tepees
nantelements
of t h e s h e l f
crest rocks.
t h e r e s u l t of p e r l t i d a l d e p o s i t i o n
strata
on a " t i d a l f l a t "
on t h e lee s i d e
This supportsEstebanandPray's(1975,
ofthecarbonatesandshoals.
1976,1977)
The s h e l f crest s t r a t a were
crest
i n t e r p r e t a t i o n of p e r i t i d a l d e p o s i t i o n f o r s h e l f
.
The i n n e r s h e l f
may b e l a m i n a t e d o r
s t r a t a are composed of Rock Type 6.
These rocks
burrowed; some lamination may b e of a l g a l o r i g i n .
Locally, crystallotopic or scattered nodular
molds of e v a p o r i t e s ,
gypsum and anhydrite,occur.Evidenceofprolongedsubaerialexposure
is absent.
The i n n e r s h e l f
strata were deposited i n a r e s t r i c t e d ,
probably hypersaline, shallow lagoon.
Sandstone rocks of the shelf
and 8.
The a u t h o rs u g g e s t s . t h a tt h e
s t r a t a are c l a s s e d as Rock Types 7
s i l i c i c l a s t i c g r a i n s were trans-
ported i n highly concentrated sediment dispersions from
d e p o s i t e d i n water depthsof
whichthey
were
3 t o 6 m.
This studysupportsEstebanandPray's(1975,1976,1977)interp r e t a t i o n of p i s o l i t h s as primary particles deposited subaqueously
in
iv
a p e r i t i d a l environment.
i n t e r t e p e ed e p r e s s i o n s .
i n the
P i s o l i t i c beds are l a r g e l yl o c a l i z e d
The i n t e r t e p e ed e p r e s s i o n s
served as "mega-
splash"cupsforpisoliteformation.
Tepee formation was syndepositional.
I t . i s t h er e s u l t
two-phase process, an e a r l y p h a s e o f d e s i c c a t i o n c o n t r a c t i o n
and a
cements.
later phase of expansion from crystallization of carbonate
Two formsof
c y c l i c s e d i m e n t a t i o n are present,sandstone-
carbonatecycles,andcycles
within carbonate strata.
sea level responsible for the sandstone-carbonate cycles
on t h e o r d e r o f
of a
5 t o 10 m; cycleswi.thinthecarbonate
r e s u l t of sea level changes on t h e o r d e r o f 1 / 2 t o
The changes i n
were probably
s t r a t a were t h e
2 m.
Changes i n
sea level resultedfromepisodicshelfsubsidence.Thisstudysupports
Pray's (1977) s u g g e s t i o n t h a t
the s a n d s t o n e u n i t s were deposited a t
high sea l e v e l s t a g e s and the c a r b o n a t e u n i t s
a t low sea l e v e l s t a g e s .
The l a t e r a l e x t e n t and t h e abundance of p i s o l i t e s and tepees
withintheshelf
crest v a r i e d . w i t h time.
the s t u d y i n t e r v a l , t h e H a i r p i n
Three i n f o r m a l u n i t s w i t h i n
Dolomite,. t h e T r i p l e t Dolomite, and
the Basal Dolomite, are c h a r a c t e r i z e d by d i f f e r e n t amounts of p i s o l i t e s
andtepees.
The HairpinDolomite
abundanceof
p i s o l i t e s and t e p e e s ; t h e T r i p l e t
i s c h a r a c t e r i z e d by a widespread
Dolomitehas
of p i s o l i t e s and tepees; the Basal Dolomitecontainsan
is between t h e s e two extremes.
to be
amount that
The a u t h o r i n t e r p r e t s t h e s e d i f f e r e n c e s
the r e s u l t of d i f f e r e n t l e n g t h s
spent in the peritidal environment,
frequency of shelf subsidence.
a paucity
of time s h e l f crest sediments
which is a f u n c t i o n of t h e rate and
V
TABLE of CONTENTS
.........................................................
INTRODUCTION .....................................................
Purpose ....................................................
Geologic Setting ............................................
Field and Laboratory Methods ..............................
ABSTRACT
...............................................
Acknowledgements ...........................................
DEPOSITIONAL PARTICLES ...........................................
Nonskeletal Particles ......................................
Skeletal Grains .........................................
i ..
ROCK FABRICS .....................................................
Fenestral Fabric ...........................................
Algal Lamination ...........................................
Burrows .....................................................
Evaporite Fabrics ..........................................
Sheet Cracks .....................
.........................
Tepees ......................................................
DIAGENESIS .......................................................
Cements ....................................................
Internal Sediment ...........................................
Porosity ...................................................
Evaporites .................................................
Emergent Surfaces ..........................................
Dolomitization .............................................
Previous Work
ii
1
1
2
11
13
15
17
17
19
28
28
31
33
33
36
36
43
43
54
54
57
58
60
vi
.......................................
61
.......................................................
64
...........................
67
........................
69
Sandstone Diagenesis
ROCK TYPES
Rock Type1. Skeletal Grainstone
Rock Type2. Nonskeletal Grainstone
Rock
Type3. Fenestral Nonskeletal-Skeletal
Packstone-Grainstone
..................................
69
Rock.Type4. Fenestral Nonskeletal
Packstone-Grainstone
71
Rock
72
Rock
Rock
..................................
Type5. Pisolitic Packstone-Grainstone................
Type6. Peloid Mudstone-Wackestone....................
Type7. Sandstone (Siliciclastic) .....................
Rock Type8. Siliciclastic-rich Peloid
Wackestone
............................................
PISOLITE GENESIS.................................................
DEPOSITIONAL ENVIRONMENTS........................................
Outer Shelf or Carbonate Sand Shoals
.......................
75
75
76
82
92
94
..................................
Inner Shelf or Lagoon
......................................
Sandstone Depositional Environment
.........................
CYCLIC SEDIMENTATION ..............................................
Sandstone-Carbonate Cycles.................................
102
...........................................
107
Shelf Crest or Tidal Flat
Carbonate Cycles
...........................
Hairpin Dolomite...........................................
Triplet Dolomite...........................................
Basal Dolomite.............................................
CONCLUSIONS ......................................................
VARIATION OF THE SHELF CREST WITH TIME
96
99
106
106
113
113
114
115
117
vii
.....................................................
APPENDIX .........................................................
Reprint of Neese and Schwartz (1977) .......................
Measured Sections ..........................................
Cross Section in Rattlesnake Canyon .....................
BIBLIOGRAPHY
123
132
134
148
(pocket)
viii
LIST o f ILLUSTRATIONS
Figure
.
2.
1
3
4
.
.
5
.
6
.
7
8
.
.
.
10.
11.
1 2.
9
.
1 4.
13
.
16.
15
.
18.
17
19
.
20
.
2 1*
Page
Physiography of the' GuadalupeMountains
................
Structural provinces of the Permian basin complex
......
3
4
Stratigraphic cross section of the Northwest
Shelf and the Delaware Basin
5
Stratigraphic cross section of the Northwest
Shelf and the Delaware Basin
6
.......................
.......................
Profile across the
Guadalupian carbonate shelf
.........
6
Geologic map of the study area and locations of
measured sections
8
Stratigraphic section of the Yates and Tansill
Formations
9
..................................
.........................................
Yates and Tansill Formations ...........................
Faults in Rattlesnake Canyon ...........................
Skeletal grainstone .....................................
Fenestral nonskeletal packstone .........................
Peloidpackstone .......................................
Fenestral nonskeletal packstone
........................
Fenestral nonskeletal-skeletal packstone ...............
Nonskeletalgrainstone .................................
Fenestral fabric .......................................
Fenestral fabric .......................................
Algalmatlamination ...................................
Algal mat lamination ...................................
Burrowed nonskeletal-skeletal packstone ................
Evaporite molds i n peloid dolomite wackestone ..........
10
12
21
22
23
24
25
26
29
30
32
32
34
35
ix
Figure
Page
............................
23 . Large tepee ............................................
22
24
..
.
.
26 .
25
.
28 .
29 .
27
30
.
Small tepee with sheet cracks
............................................
Isopachous cement in nonskeletal'grainstone ............
Isopachous cement.lining fenestrae .....................
Microcrystalline cementand sparry cement' ..............
Microcrystalline and microspar cement ..................
Internal sediment i n a sheet crack .....................
Small tepee
32
.
Crossbedding in nonskeletal grainstone
.
36
.
37
.
.
39 .
40 .
38
49
50
51
52
55
62
S i l i c i c l a s t i c sandstone
35
40
59
..............................
................................
.
.
34 .
39
Incipient calichefication i n a fenestral
nonskeletal packstone
31
33
37
.................
Parallel lamination in nonskeletal grainstone
..........
Pisolitic grainstone ...................................
S i l i c i c l a s t i c sandstone ...................................
Fluidescape structures ................................
Siliciclastic-rich peloid wackestone ...................
In-place p i s o l i t e s .....................................
Clastic pisolites ......................................
Environments of a Holocene carbonate platform ..........
68
70
74
77
79
ao
a6
a7
93
TABLE
Tab l e
.
1
Page
Rock types
........................
.....................
65
INTRODUCTION
Purpose
Numerous g e o l o g i s t s h a v e v e n t u r e d i n t o t h e
GuadalupeMountains
of west Texas and New Mexico t o examine exposures of
a now-classical
carbonate shelf-to-basin transition in the Permian
Despite the considerable
on many problems.
amount of study, information
shelfmargin,
is s t i l l needed
The problems r e l a t e d t o s h e l f s t r a t a a r e :
1) genesis of t h e p i s o l i t e f a c i e s ,
t h es h e l fs a n d s t o n e s
ReefComplex.
2) depositionalenvironment(s)
3) d e p o s i t i o n a lp r o f i l ea c r o s st h es h e l f
4) t y p e s o f c y c l i c s e d i m e n t a t i o n ,
of
and
5) r a n g e o f s e a l e v e l
fluctuationresponsibleforcyclicsedimentation,
6) r e l a t i v e impor-
tance of vadose meteoric versus submarine diagenetic processes.
previously, broad Guadalupian age regional facies have been
described by Lloyd(1929),
King (1948), Newel1
a.(1953),Kendall
(1969); Tyrrell (1969), Dunham (1972),andSmith(1974b).
s t u d i e s were concerned with mostof
i n t h e GuadalupeMountains.
the stratigraphic interval present
However, d e t a i l e ds e d i m e n t o l o g i cs t u d i e s
ofthevariousGuadalupianagerocktypes
and s t r a t i g r a p h i c u n i t s
composing t h e s e r e g i o n a l f a c i e s h a v e n o t b e e n
t h i s s t u d y was todetermine,throughstudy
beds,thedetailedfaciesmosaicof
of c a r b o n a t es h e l f
These
done.
The o b j e c t i v e o f
and t r a c i n g o f i n d i v i d u a l
a limited stratigraphic interval
strata a d j a c e n tt ot h eC a p i t a n" r e e f " .
This
d e t a i l e d i n v e s t i g a t i o n would y i e l d some of the information necessary
to solve the
problems d e s c r i b e d above.
2
Geologic Setting
The GuadalupeMountains
are a t r i a n g u l a r b l o c k , t i l t e d g e n t l y
eastward andbounded
on t h e w e s t by a zoneof
( F i g u r e1 ) .R e l i e f
on t h es o u t h e a s t e r ns i d eo ft h e
l a r g e normal f a u l t s
Guadalupe
Mountains r e f l e c t s the o r i g i n a l d e p o s i t i o n a l t o p o g r a p h y
shelfto
the b a s i n .
1), forms p a r t of the' rim of the
Delaware Basin, a Permian i n t r a c r a t o n i c b a s i n ( F i g u r e
2).
t h e GuadalupeMountains
are p a r t of the Northwest Shelf.
t h e GuadalupeMountains
are Leonardian and Guadalupian
DuringGuadalupian
ate rocks of
b e l t on the marginofthe
Most of
. Strata i n
i n age.
the predominantlycarbon-
time deposition of
a narrow 1 5 t o 25 km wide
the Northwest Shelf occupied
b e l t gradesinto
on t h e
The Capitan or GuadalupeEscarpment,
the block (Figure
southeast side of
from t h e
Delaware Basin.Shelfwardthecarbonate
an e v a p o r i t e b e l t 5 0 t o 1 0 0
km wide. Further shelf-
ward t h e e v a p o r i t e s g r a d e i n t o c o n t i n e n t a l r e d s h a l e s
Basinward t h e c a r b o n a t e s h e l f r o c k s g r a d e i n t o
Znd sandstones.
the rocks of the
Delaware Basin, which are predominantly sandstone with minor
of interbedded limestone (Figure
,
This studyfocuses
tion, centered .about
t i o n s( F i g u r e
4).
amounts
3).
on approximately 45 m of s t r a t i g r a p h i c sec-
the contact between the Yates and T a n s i l l FormaThe Yates and T a n s i l l Formations are composed
of s h e l f strata deposited on the NorthwestShelf.
The Yates Forma-
t i o n is composed ofinterbeddedsandstonesandcarbonates.
The over-
l y i n g T a n s i l l Formation and underlying Seven Rivers Formation
predominantlycarbonates.Basinwardthe
are
Yates and TansillFormations
3
Figure 1.
Physiography of the Guadalupe Mountains, Texas and New
Mexico. Study area colored green.
4
Figure 2 .
S t r u c t u r a lp r o v i n c e s of t h e Permian b a s i n complex, Texas
and New Mexico. Study area coloredgreen.
5
NORTHWEST SHELF
"
DELAWARE BASIN
A
V
Figure 3.
A
Stratigraphic cross section ofthe Northwest Shelf and
the Delaware Basin showingthe regional facies. After
Meissner (1972). Study area colored green.
6
WH
SHELF
BWSiN
CASTILE
SE
FM.
VICTOR10 PEAK MBR.
BONE SPRING LS.
1.6
Figure 4 .
S t r a t i g r a p h i cc r o s ss e c t i o n
of theNorthwestShelf
DelawareBasin.Study
areacoloredgreen.
Figure 5.
Proposed p r o f i l e a c r o s s t h e
AfterPray (1977).
32 KM
and t h e
Guadalupiancarbonateshelf.
The CapitanLimestone
gradeabruptlyintotheCapitanLimestone.
is
c o m p r i s e st h es h e l fe d g eo rs h e l fm a r g i nf a c i e s .T h i ss t u d y
focused on t h e most basinward 2 1/2 l
a of s h e l f strata, ar, area of
r a p i df a c i e sc h a n g e s .
was divided by Pray (1977)
This area of rapid facies changes
i n t of i v ec a r b o n a t ef a c i e s( F i g u r e
basinwarddirection
are:
s h e l f , 4 ) shelfedge,and
5).
These f a c i e s l i s t e d i n
crest, 3) o u t e r
1) i n n e rs h e l f ,2 ) . s h e l f
5) basinedge.
a
One mainfocusof
this
study i s t h e t r a n s i t i o n f r o m t h e i n n e r s h e l f a c r o s s t h e s h e l f c r e s t
to the outer shelf.
Excellent exposures of the shelf
and shelf edge rocks occur
i n t h e many c a n y o n s . d i s s e c t i n g t h e s o u t h e a s t s i d e o f t h e
Mountains.
Guadalupe
S t r a t i g r a p h i c s e c t i o n s were measured in R a t t l e s n a k e
Canyon and some r e c o m a i s a n c e work was c a r r i e d o u t i n Walnut Canyon
(Figure 6 ) .
National Park
Bothof
t h e s e canyons a r e l o c a t e d i n t h e C a r l s b a d
i n s o u t h e a s t e r n New Mexico.
R a t t l e s n a k e Canyon v a s
chosen as t h e s t u d y area b e c a u s e o f t h e e x c e l l e n t
exposures of the
and continuous
Yates and Tansill Formations along
cular to the shelf,
Caverns
a line perpendi-
edge.
The s t r a t i g r a p h i c i n t e r v a l s t u d i e d was d i v i d e d i n t o t h r e e i n formalrockunits;theHairpinDolomite,theTripletUnit,
B a s a lT a n s i l l
U n i t (Figures 7 and 8).
author and other
and t h e
These names were used by t h e
members of the Wisconsin carbonate research group
working i n the GuadalupeMountains
(Esteban and Pray,1977).
The
s t r a t i g r a p h i c s e c t i o n i n F i g u r e 7 was measured i n Walnut Canyon,
8
Figure 6.
Geologic map of t h e s t u d y a r e a
and l o c a t i o n s of measured
sections.Study
area of authorcoloredgreen.
9
'
STRATIGRAPHIC
u
a
SECTION, WALNUT '. CANYON.
v)
Z W
00
CY)
u)w
z:
gk!
INFORMAL
ROCK UNITS
XEX
DOLOMITE
I.I
Grain types
]SO+FT.
'
Restricted skeletal
1
d
-
,
'
Peloids, composite '
and
coated
micrite
.
I
Pisoliths
STUDY
INTERVAL
I
i
J :
'
Depositional texture
Mud-supported
All other rocks are
grain-supported
.:.
.. .
Figure 7.
G e n e r a l i z e ds t r a t i g r a p h i cs e c t i o n
of theYates and
Tansill Formations showing t h e i n f o r m a l d i v i s i o n i n t o
s m a l l e ru n i t s .S e c t i o n
measured i n c e n t e r of t h e p i s o l i t e
b e l t i n Walnut Canyon. Taken from EstebanandPray
(1977)
Study i n t e r v a l c o l o r e d g r e e n .
10
Figure 8.
Photograph of the Yates and Tansill Formations showing
the informal division into the Hairpin Dolomite, Triplet
Unit, and Basal Dolomite. Photograph is of the northeast
side of Rattlesnake Canyon about 314 km shelfward of
the Capitan Escarpment. The basin is to the right and
the shelf is tothe left.
11
1.6 km shelfward of the Capitan Limestone and
snake Canyon, alongapproximate
D i n R a t t l e s n a k e Canyon.
facies s t r i k e w i t h measured s e c t i o n
Boundariesbetweenthesethreeunits
a t contactsbetweencarbonate
and sandstonebeds.
units and two sandy carbonate units
few degrees o r less.
t i v e l ye a s y .
Two sandstone
the study area,
thin
200 m of the Capitan Limestone, where they
and g r a d e a b r u p t l y i n t o
Strata i n mostof
are
in the study interval provide
are continuous over mostof
excellent markers and
persisting to within
7.2 km east of Rattle-
the s h e l f edge carbonates.
the study area are undeformed with dips of
a
This made c o r r e l a t i o n i n the study area rela-
However, i n Rattlesnake Canyon 1.1 and 1.2 km s h e l f -
ward of the Capitan Escarpment,
with a down-thrown blockbetween
two previously unmapped' f a u l t s o c c u r
them ( F i g u r e 9 ) .
The f a u l t s t r e n d
parallel to the Capitan Escarpment and have stratigraphic displacements of approximately 16 m.
King(1948)determined
t o b e l a t e Pliocene or e a r l y
f a u l t i n g i n t h e GuadalupeMountains
Pleistocene.
Use of the sandstonemarkersand
logy p e r m i t s a c c u r a t e c o r r e l a t i o n
Field and Laboratory
"
the carbonatelitho-
across t h e f a u l t s .
Methods
F i e l d work was conducted during the
Augustof1976andduring
theageofthe
months ofJune,July,and
a 2 week p e r i o d i n January of 1977.
s t r a t i g r a p h i c s e c t i o n s were described andmeasured
the Rattlesnake Canyon area (Figure 6 ) .
conducted i n the Walnut Canyon area.
Six
in the field in
Reconnaissancework
was
The reconnaissance work was
assisted by Douglas Neese, Mateu Esteban, Lloyd Pray and other
mew
12
I
i
E
Figure 9.
Photogra.phof
two f a u l t si nR a t t l e s n a k e
Canyon. The f a u l t s
s t r i k ep a r a l l e lt ot h e
GuadalupeEscarpment.
The f a u l t s
are locatedbetweenmeasuredsections
B and C. Arrows
i n d i c a t e relative m o t i o na l o n gt h ef a u l t s .I nt h i sp h o t o
t h e b a s i n is t o t h e l e f t and t h e s h e l f is t o t h e r i g h t .
13
bers of the
Wiscons: i nc a r b o n a t e research group.Douglas
Neese con-
d u c t e d f i e l d work i n Walnut Canyon on a complementary Masters t h e s i s
during the same time period as t h e a u t h o r
Approximately 300 handsamples
bed, polished,
andexamined
were c o l l e c t e d .
These were slab-
with respect to their depositional
diageneticfabrics.Carbonaterocks
and
were c l a s s i f i e d u s i n g t h e s y s t e m
proposed by Dunham (1962).Sandstones
systemproposed
(Neese, 1979).
were c l a s s i f i e d u s i n g t h e
100,
by Dott(1964).Thinsections,approximately
were examined using the petrographicmicroscope.
Some t h i n s e c t i o n s
of carbonates were s t a i n e d w i t h a d o u b l e s t a i n of a l i z a r i n red-Sand
potassium ferricyanide, to differentiate
t od e t e c t
calcite fromdolomite
the presence of ferrousiron(Dickson,1965).
sections of sandstones
sium f e l d s p a r( B a i l e y
Some thin
were e t c h e d w i t h h y d r o f l u o r i c a c i d
with sodium cobaltinitrite solution to detect
and
and s t a i n e d
the presence of potas-
and.Stevens,1960).Figuredspecimens
are on
f i l e , thesis number UW 1666, a t the Department of Geology, University
ofWisconsin,Madison,Wisconsin.
Previous
.the Permian
The amount o f p u b l i s h e d l i t e r a t u r e c o n c e r n e d w i t h
Basincomplex
i s extensive.
P h i l i p E. King(1948)wrote
s i o n a l p a p e r that d e a l t w i t h t h e s t r a t i g r a p h y , t e c t o n i c s ,
a profes-
mapping
and many other geologic aspects of the southern Guadalupe Mountains.
This now-classic work, served to spark the
interests of many geolo-
g i s t s i n the geology of the Guada1up.e Mountains.
(1958),Motts
(1962).,andHayes(1964)
GuadalupeMountains
Hayes andKoogle
extendedthe
mapping of t h e
that P h i l i p King hadstudied.Tyrell(1969),
14
using fusulinid zonation, focused
on t h e d i f f i c u l t problem of cor-
r e l a t i o n from the s h e l f t o t h e b a s i n .
The book by Newell
et &.
(1953) discussed i n d e t a i l t h e s e d i -
mentologic and paleoecologic aspects of .the Permian reef
The Capitan Limestone w a s i n t e r p r e t e d t o b e
e t a l . (1953).
"
The N e w e l l
et &.
complex.
a b a r r i e r r e e f by Newell
(1953) book f u r t h e r s t i m u l a t e d
work on the f a c i e s and i n t e r p r e t a t i o n o f t h e d e p o s i t i o n a l p r o f i l e
across the shelf
and s h e l f edge.
S t u d i e s byBoyd
Tyrrell(1969),
(1958),Kendall(1969),
Dunham (1972),Meissner(1972),
investigated the depositional
r e g i o n a lf a c i e s .
Silver and Todd (1969),
andSmith(1974b)
and diagenetic environments of broad
These authorsalsodescribedthesandstone-carbonate
cycles i n the s h e l f strata.
Smith (1974b) d e s c r i b e dc y c l e sw i t h i n
the carbonate strata..
The work by Kendall(1969),
Dunham (1972), and Smith (1974b)
a l s o d e a l t with t h e d i a g e n e t i c e n v i r o n m e n t s o f t h e f a c i e s .
Dunham's
work s t r e s s e d the importance of vadose meteoric processes during the
e a r l yd i a g e n e s i s
of these rocks.
topographic crest of the Capitan
H e a l s op r o p o s e dt h a t
the paleo-
Reef Complex was i n the p i s o l i t e
b e l t o f the s h e l f s t r a t a and not i n t h e o r g a n i c " r e e f " r o c k s
of t h e
s h e l f edge.
Recently, the University of Wisconsin carbonate research group
under the d i r e c t i o n o f
LloydPray
to the sedimentology problems
has b e e n d i r e c t i n g its a t t e n t i o n
of the Permian ReefComplex
the GuadalupeMountains'.Babcock's(1974)andYurewicz's(1976)
exposed i n
15
d o c t o r a l theses focused on the Capitan Massive.
Both t h e s e s empha-
s i z e d the i n t e r p r e t a t i o n t h a t the Capitan Limestone was n o t a b a r r i e r
reef but
formed a t a submerged shelf edge,and
portance of submarine processes 'during
Capitan Massive.'
also stressed the
m
i -
the . e a r l y d i a g e n e s i s of t h e
My thesis was conductedconcur-rently w i t h t h a t of
Douglas Neese (Masters thesis, 1979).
The author.and Douglas Neese
(1979) were concerned with d e p o s i t i o n a l and diagenetic environments
of s h e l f strata.
E a r l y . r e s u l t s from t h e s e theses were published i n
a j o i n t a r t i c l e (see a p p e n d i x f o r a copy of t h e p u b l i c a t i o n ,
andSchwartz',
1977).Sarg's
the transi-tionfrom
(1976) d o c t o r a lt h e s i s
Neese
was a study of
the e v a p o r i t e b e l t t o t h e c a r b o n a t e b e l t .
At
the p r e s e n t time the Goat Seep Formation i s under'study by Allan
Crawford.
Neil Hurley(1978)
r e c e n t l yf i n i s h e d . as t u d y
on s h e l f
strata i n a p o s i t i o n o n t h e d e p o s i t i o n a l p r o f i l e e q u i v a l e n t t o t h e
study area of t h e a u t h o r b u t
section.
i n an older part of the stratigraphic
. ,
For a more extensive l i s t i n g of the l i t e r a t u r e , a s e l e c t e d
bibliography of Guadalupian literature
Field conference guidebook of
is presented i n the 1977
the Permian Basin s e c t i o n of the Soci-
e t y of Economic Paleontologists and Mineralogists.
Acknowledgements
Financial support for the .field
work was provided i n the form
of a grant from the New Mexico Bureau of
Mines. and Mineral Resources.
The Wisconsin Alumni Research Foundation provided financial support
i n t h e formof
'a research a s s i s t a n t s h i p .
The a s s i s t a n c e andcooper-
16
a t i o n of personnel from
ciated.
the Carlsbad Caverns National Park is appre-
D r . Mateu Estebanfrom
the UniversityofBarcelona,Spain
a s s i s t e d i n many a s p e c t s in t h e f i e l d and i n the l a b o r a t o r y .
Discus-
s i o n s with Douglas Neese, who worked i n the f i e l d on a complementary
problem a t the same t i m e as the author were h e l p f u l .
andencouragement
The a s s i s t a n c e
of. my wife i n t h e p r o d u c t i o n of the f i n a l d r a f t of
this thesis is g r e a t l ya p p r e c i a t e d .F i n a l l y ,
suggested and supervised this thesis.
D r . Lloyd C. Pray
17
DEPOSITIONAL PARTICLES
Introduction
as e i t h e r n o n s k e l e t a l
Depositional particles can be classified
or s k e l e t a l .
Dunham (1972),Smith(1974b),andEstebanandPray
(1977) have documented that i n a s h e l f w a r d d i r e c t i o n , t h e p r o p o r t i o n
These
o fc a r b o n a t en o s k e l e t a lt os k e l e t a lp a r t i c l e si n c r e a s e s .
same a u t h o r s a l s o documented that p a r t i c l e s i z e d e c r e a s e s
ward d i r e c t i o n . P a r t i c l e t y p e s
i n a shelf-
are here defined and d e s c r i b e d t o
c l a r i f y the d e s c r i p t i o n s of r o c k f a b r i c s
and rock types given
later.
Nonskeletal Particles
N o n s k e l e t a l p a r t i c l e s are t h e mostabundanttype
strata.
D e f i n i t i o n s of n o n s k e l e t a l p a r t i c l e s
different authors
i n the s h e l f
are troublesomebecause
w i l l use d i f f e r e n t names f o r t h e same p a r t i c l e .
Another problem with nonskeletal particles
differentiate two p a r t i c l e t y p e s o n
is that authors w i l l
@e b a s i s of a s i z e l i m i t a t i o n .
D i f f e r e n t a u t h o r s will use d i f f e r e n t s i z e l i m i t a t i o n s .
w i l l attempt to give .the best definition
The author
and w i l l note synonyms where
appropriate.
Peloids
-
Peloids are g r a i n s composed of an aggregate of cryptocry-
stalline carbonate.
This term can b e u s e d i r r e s p e c t i v e o f t h e s i z e ,
shape, or o r i g i n of t h e grain (McKee andGutschick,1969).In
my
study area, I use the t e r m p e l o i d s f o r c r y p t o c r y s t a l l i n e g r a i n s t h a t
range from 0.2 to
Pellets
-
5 mm i n size.
“A g r a i n composed of m i c r i t i c ( c r y p t o c n s t a l l i n e )
material,
lacking significant internal structure
Most p e l l e t s are very f i n e s a n d t o
and generally ovoid
i n shape.
coarse s i l t s i z e grains", (Leigh-
"..,..
(1962) d e s c r i b e s p e l l e t s as,
t o n and Pendexter, 1962). Folk
or ovoid aggregates of microcrystal-
rounded, s p h e r i c a l t o e l l i p t i c a l
line calcite ooze, devoid of any internal s t r u c t u r e " .T h i s
termwill
the smaller c r y p t o c r y s t a l l i n eg r a i n st h a t
b eu s e dh e r et od e s c r i b e
range i n s i z e from 0.03 t o 0.2
mm.
P e l l e t s are alwaysroundedspher-
i c a l t oe l l i p t i c a lg r a i n s .P e l o i d sc a nb e
Lumps; Aggregates;Aggregate
.
any shape.
Lumps; Grapestones
- These terms
are
Milliman (1974) d e f i n e s
probably the most troublesometodefine.
"aggregate" as a g r a i n that contains. two o r more fragments joined
together by a c r y p t o c r y s t a l l i n e matrix which c o n s t i t u t e s less than
50% o ft h eg r a i n .I l l i n g
Holocenesedimentsandcalled
(1954j f i r s t recognized these p a r t i c l e s i n
them "lumps".
The term grapestone was r e s e r v e d f o r t h o s e
grainsprotrude,resembling
H e defined several types.
lumps fromwhichround
a bunch ofgrapes.Milliman(1974)pro-
posed that "lump" be used t o r e f e r t o p a r t i c l e s
half the grain-is
paper, instead the
Intraclasts
-
matrix.
i n which more than
terms w i l l beused
None of these
i n this
term intraclast defined below w i l l be used.
Folk (1962) d e f i n e d t h i s
term as "fragments ofpenecon-
temporaneous, g e n e r a l l y weakly consolidated carbonate sediment that
the sea bottom and redeposi-
has been eroded from adjoining parts of
ted to
form a new sediment."Folkincluded
i n t r a c l a s ts
Lithoclasts
Illing's "grapestone"
as
.
- Folk(1962)described
these as fragments of consolida-
ted limestone eroded from ancient limestone outcrops
on anemergent
19
~
land area.
The a u t h o r b e l i . e v e s t h a t t h i s d e f i n i t i o n s h o u l d b e a l t e r e d
by o m i t t i n g the word "ancient".Evidence
t i o n of
now i n d i c a t e s t h a t l i t h i f i c a -
carbonatesedimentcanoccurveryrapidlyandcanbeconsi-
d e r e d a s penecontemporaneous.
Ooid - N e w e l l s &. (1960)
defined an ooid
as a p a r t i c l e t h a t h a s
o n e o r more r,egular lamellae formed as successive coatings around
nucleusand
i n which, the c r y s t a l s of the
lamellae must show a sys-
tematic crystallographic orientation with respect
Ooids are d e f i n e d t o b e
Pisolites
a
t o the grain surface.
less t h a n 2 mm i n diameter.
- P i s o l i t e s are s p h e r i c a l t o i r r e g u l a r s h a p e d p a r t i c l e s
w i t h a m u l t i p l e laminated coating and
Pisolith nuclei can be skeletal
a diameter greater than
or n o n s k e l e t a l and can be
2
m
m
.
composed
of s i n g l e or m u l t i p l e p a r t i c l e s . .
Coated Grains
- Coated g r a i n s are i r r e g u l a r l y s h a p e d p a r t i c l e s w i t h
an accretionary coating.
Hcrite
-
Micrite refers t o c l a y s i z e d c a r b o n a t e p a r t i c l e s .
upper s i z e l i m i t o f m i c r i t e
Siliciclastics
-
is 4 microns i n diameter.
This term r e f e r s t o a l l t h e n o n c a r b o n a t e
Within the carbonate rocks quartz
mineralandfeldsparoccursin
r o c k st h e r e
The
particle?.
i s t h e predominant s i l i c i c l a s t i c
small q u a n t i t i e s . W i t h i n t h e s a n d s t o n e
are s e v e r a l s i l i c i c l a s t i c m i n e r a l s .
These a r e d e s c r i b e d
i n t h e s e c t i o n on rock types.
Skeletal Grains
S k e l e t a l g r a i n s are most abundant i n t h e o u t e r m o s t o r b a s i n w a r d
portionsof
the s h e l f .
Althoughthey
are abundant i n some b e d s t h e
20
d i v e r s i t y of t h e b i o t a is low.
This is a n i n d i c a t i o n t h a t s a l i n i t y
and water c i r c u l a t i o n o n t h e s h e l f
were v a r i a b l e , p r o b a b l y
due t o
d e p o s i t i o n a t or near sea l e v e l .
Dasycladacean
- Grains of dasycladacean algae,
are t h e mostabundant
area.
skeletal particles in the rocks
The two majorgenera
studyarea
a green algae,
of dasycladaceanalgaerecognized
are MizziaandMacroporella(Johnson,
and environmental studies of
of t h e s t u d y
1942).
.
Ecologic
modern d a s y c l a d a c e a n a l g a e i n d i c a t e t h a t
they occur i n shallow protected marine lagoons (Ginsburg
1971)
in the
eta.,
SeeFigure10.
Calcispheres
- Calcispheres are single-chambered,hollowcalcareous
s p h e r e s w i t h a c r y p t o c r y s t a l l i n e wall s t r u c t u r e and an average diam-
eter of 70 t o 100 microns(Bathurst,1971).Bothspinoseand
are i n t e r p r e t e d
s p i n o s e forms are p r e s e n t .C u r r e n t l y ,c a l c i s p h e r e s
to be the reproductive spores
non-
of dasycladacean algae (Way,1977).
Most f o s s i l c a l c i s p h e r e s are r e p o r t e d f r o m r o c k s i n t e r p r e t e d
as de-
p o s i t e d i n very s h a l l o w m a r i n e w a t e r w i t h r e s t r i c t e d c i r c u l a t i o n
11.
(Wilson,1975).SeeFigure
Foraminifera
- Two g e n e r a l t y p e s
i n g and f u s u l i n i d s . .
These f o r a m i n i f e r a a r e d i s c u s s e d i n d e t a i l
because of their unusual
tion.
of forams are recognized, encrust-
morphologyand
their importance in correla-
Two generaofencrustingforamshavebeenidentified,
T u b e r i t i n a andHemigordius(Figures
12 and 13).
Generally,these
forams are f o u n d u n a t t a c h e d . T u b e r i t i n a c a n o f t e n b e m i s t a k e n l y
i d e n t i f i e d as a c a l c i s p h e r e .
However, T u b e r i t i n ah a s
a larger
.
21
'*
A
i
Figure 10.
N e g a t i v e p r i n t of a t h i n s e c t i o n of a s k e l e t a l g r a i n s t o n e ,
RockType 1, showing dasycladaceanalgae (D) and
Tubiphytes?
(T).
(VW 1666/1).
22
Figure 11. Thinsectionphotomicrographof
a f e n e s t r a ln o n s k e l e t a l
4 . This p a r t i c u l a r sample i s
packstone, Rock
Type
composed of p e l l e t s predominantly.Spinosecalcispheres
(C) are a l s o p r e s e n t i n a small amount. Fenestrae are
p a r t i a l l yf i l l e dw i t hm i c r o s p a r
cement. V
(W 1 6 6 6 / 2 ) .
23
Figure 1 2 .
Thinsectionphotomicrograph
of a p e l o i d p a c b t o n e ,
Rock
Type
4 . Rock i s cemented withmicrospar.Note
t h eT u b e r i t i n a (T).
(UW 1666/3).
24
Figure 13.
Thin section photomicrograph of 2 porous f e n e s t r a l
nonskeletalpackstone, Rock Type 4 . P o r o s i t y i s
f e n e s t r a l . some solution enlargement of f e n e s t r a e i s
a l s op r e s e n t .
Note t h e HernigoGdius (H) foram.
(UW 1 6 6 6 / 4 ) .
25
Figure 1 4 .
Thin s e c t i o n photomicrograph of a f e n e s t r a l n o n s k e l e t a l 3. Fenestrae(F)
are
s k e l e t a lp a c k s t o n e , Rock
Type
f i l l e d w i t h m i c r o s p a r cement.Note
theCodonofusiella
f u s u l i n i d( C ) .
(UW 1666/5).
26
Figure 15.
Thin s e c t i o n photomicrographof a n o n s k e l e t a lg r a i n s t o n e ,
Rock
Type
2 . Most p a r t i c l e s are p e l o i d s . Some appear
tobeaggregategrains.
Note t h e Yabeina f u s u l i n i d .
Cement f i l l i n g p o r e s i s equantspar.Withinthefusulinid
theporeshaveanisopachous
cement l i n i n g . (W 166616).
27
diameter, 170 t o 400 microns, is non-spinose with perforate
test
walls, and is o f t e n multichambered with 2 t o 4 bulbous chambers
a r r a n g e du n i s e r i a l l y
(Toomey, 1972).
have been identified, Codonofusiella
Two genera of fusulinids
andYabeina(Figures
1 4 and 15).
these f u s u l i n i d s t h e r e a d e r
For a s y s t e m a t i c d e s c r i p t i o n of
i s r e f e r r e d t o SkinnerandWilde
For a d i s c u s s i o n o f f u s u l i n i d z o n a t i o n
i s referredto
(1955).
i n t h e s h e l f strata t h e r e a d e r
Tyrrell (1969).
Miscellaneous Skeletals.
o r ' trace amounts.
- Other s k e l e t a l g r a i n s
are p r e s e n t i n minor
They includegastropods,brachiopods,pelecypods,
greenalgae,ostracods,echinoderms,sponges,bryozoans,and
Tubiphytes.
These m i s c e l l a n e o u ss k e l e t a lg r a i n s
as fragmented particles, although whole gastropods
most commoky occur
are common.
28
ROCK FAERICS
Introduction
Rock f a b r i c can be defined
as t h e o r i e n t a t i o n and arrangement
i n spaceofvariouselementsthatcomprise
In carbonatesthe
are the g r a i n s , matrix, cements,porosity,and.
major f a b r i c e l e m e n t s
internalsediment.
a rock.
It i s ' : t h e r o c k f a b r i c
mation on t h e d e p o s i t i o n a l
which y i e l d s the b e s t i n f o r -
and diageneticenvironments.
p r e s e n t i n s t r a t a ofthestudy
Rock f a b r i c s
area are describedbelow.Discussion
of their occurence within the "back . r e e f " o r s h e l f
s t r a t a is reserved
f o r later i n the r e p o r t .
Fenestral Fabric
- Fenestral fabric
i s t h e term applied t o a rock i n
which f e n e s t r a e are present.Tebbutt
as,
,1
e t a l . (1965) d e f i n e df e n e s t r a e '
"
primary o r penecontemporaneousgaps
i n a rock framework, that
are l a r g e r t h a n g r a i n s u p p o r t e d
interstices".
(1970) m o d i f i e d t h i s d e f i n i t i o n
t o make i t a l s o a p p l i c a b l e t o
ChoquetteandPray
supported rocks by d e f i n i n g f e n e s t r a e as any primaryopening
mudlarger
.,
thanthe
normal i n t e r p a r t i c l e o p e n i n g s .
A f e n e s t r a e may beanopen
s p a c e o r i t may b e p a r t i a l l y o r c o m p l e t e l y f i l l e a w i t h
internalsediment.(Figures
1 6 and 17).
Currently, the a c c e p t e d i n t e r p r e t a t i o n
formby
several processes:
cement andfor
is thatfenestraecan
1) molds of a l g a l mats, 2) a l t e r n a t e
w e t t i n g and drying of sedimentproducingplanarshrinkagecavities,
3) trapped air o r g a s b u b b l e s p r o d u c i n g s p h e r i c a l o r i r r e g u l a r
c a v i t i e s (Boyd, 1975).
29
Figure 1 6 .
Outcropphotographshowing
f e n e s t r a lf a b r i ci n
nonskeletalpackstone.Outcroplocatedinmeasured
S e c t i o n C. White c i r c l e i s 2 cm i n diameter.
a fenestral
30
E
I
Figure 1 7 .
P o l i s h e ds l a b
showing f e n e s t r a lf a b r i c .
(VW 1666/7).
32
Figure 18.
Outcrop in Section C showing algal mat lamination.
White circle is 2 cm in diameter.
!
Figure 19.
Polished slab showing algal mat lamination.
(UIJ 1666/ 8).
33
Burrows
- Burrows o c c u rw i t h i n
as u n f i l l e d , b r a n c h e d
the f i e l d , burrowsappear
tubes.
Smith(1974b)
some of t h e n o n - p i s o l i t i c r o c k s . I n
i n t e r p r e t e d mostof
However, the a u t h o r d i d n o t
o r unbranchedcurved
t h e burrows t o b e U-shaped.
see any evidence of either U-shaped
or
The burrows are 2 t o 5 mm i n diameter, up t o 10 cm
J-shapedburrows.
i n l e n g t h , andmost
are neither v e r t i c a l nor h o r i z o n t a l b u t are ir-
r e g u l a r l yi n c l i n e d .
(SeeFigure
20).
Esteban and Pray (1977) suggest-
ed the p o s s i b i l i t y t h a t s o m e t u b u l a r f e n e s t r a e ,
might beburrows.
In p o l i s h e d s l a b s ,
1 t o 2 mm i n diameter
a few s p r a i t e - f i l l e d burrows
were found.
Garrett (1977) described similar u n f i l l e d burrows i n Holocene
i n t e r t i d a l pond sediments on Northwest Andros I s l a n d , Bahamas.
These burrows were made by a polychaete belonging to
Dasybranchus.
S e i l a c h e r (1967)and
the genera
that
Rhoads (1975) have'noted
vertical o r inclined burrows are domixiant i n strata deposited i n t h e
i n t e r t i d a l zone.
Horizontalburrowsalongbeddingsurfaces
are
p r e s e n t i n n e r i t i c environments.Horizontalburrowshavenotbeen
noted i n the s t u d y area.
Comparison of the Guadalupian age burrows
with Holocene burrows and burrows of other ages indicate tha.t the
Guadalupian burrows probably originated
in the i n t e r t i d a l or shallow
sub t i d a l environment.
Evaporite Fabrics
- Two
types of evaporite
c r y s t a l l o t o p i c andnodular.Crystallotopic
formof
molds are p r e s e n t ,
molds show t h ec r y s t a l
the o r i g i n a l e v a p o r i t e mineral, gypsum or anhydrite.
Nodular molds are irregular shaped equidimensional
molds. (Figure 21).
T
..
34
Figure 20.
Outcrop of mixed nonskeletal-skeletalPackstoneshowing
burrowing.Outcropoccurs
i n Section D. White c i r c l e
is 2 c m i n diameter.
35
Figure 21.
Outcrop of peloid dolomite wackestone showing crystallotopic and nodular evaporite molds. Photograph taken
by Douglas Neese in Walnut Canyon. White circle is
2 cm in diameter.
36
~
I n the study area t h ee v a p o r i t ef a b r i c so c c u r
a s e i t h e r openpores
o r as molds f i l l e d w i t h s p a r r y e q u a n t c a l c i t e
cement.
fabrics have been recognized only in
The e v a p o r i t e
mudstones and wackestones of
the study area.
Sheet Cracks
-
F i s c h e r (1964) d e f i n e d s h e e t c r a c k s a s h o r i z o n t a l
shrinkagecracksoropenings.Esteban
and Pray.(1977)
redefined
t h e .term so t h a t i t would encompass a l l n o n - t e c t o n i c f r a c t u r e s
(Dunham's term, 1968) of s h r i n k a g eo re x p a n s i o no r i g i n .
c r a c k s are h o r i z o n t a l o r - p a r a l l e l t o b e d d i n g .
cal sheet cracks
Most s h e e t
High a n g l e o r v e r t i -
are much less f r e q u e n t t h a n . t h o s e p a r a l l e l t o
22 and
ding and more commonly c u ta c r o s st h e , g r a i n s .( S e eF i g u r e s
29).
F i s c h e r (1964) i n t e r p r e t e ds h e e tc r a c k s
as s h r i n k a g es t r u c t u r e s
t h a t r e s u l t e d from desiccation of sediments deposited
i n t h e Permian strata as the r e s u l t of expansion due
to forces exerted
a r a g o n i t e and e v a p o r i t e c r y s t a l s t r a p p e d i n i n t e r t i d a l
sediments.Both
Smithand
i n t e r t i d a l phenomenon.
t i d a l environment.
may a l s o h a v e formed i n a shallow sub-
In thePelmian
plexly filled with eogenetic
- Tepees
F i s c h e rc o n s i d e r . s h e e tc r a c k st ob ea n
EstebanandPray(1975,1976,1977)have
suggested that sheet cracks
Tepees
in the inter-
i n t e r p r e t e d some of t h es h e e tc r a c k s
t i d a l environment.Smith(1974a)
bygrowing
bed-
s'trata most s h e e t c r a c k s
cementsan$/or
are con-
internal sediment.
arenontectonicanticlinalstructures.
A typical
tepee has a characteristic symmetrical chevronlike structure with
b e d d i n gi n c l i n e d
upward toward a s u b v e r t i c a l axial f r a c t u r e .
is some i n t e r d i g i t a t i o n of t r u n c a t e d b e d s f r o m o p p o s i t e s i d e s
There
of
37
I
*
I
I
r
t
1'
+
Figure 22.
Outcropshowing l e f t f l a n k of a small tepee with
sheetcracks
(SH).
Outcrop occurs i n s e c t i o n C.
White c i r c l e i s 2 cm i n diameter.
38
the axial f r a c t u r e .
Dips ofbedswithintepees
than 50 degrees,but
some beds do approach vertical.
m i n height.(Figures
from.1/4to2
Pray(1977)
are g e n e r a l l y less
22, 23, and 2 4 . )
Tepeesrange
Esteban and
r e p o r t e d that commonly the spacing of tepees
t o the s i z e of the tepees.
The smaller tepees are closelyspaced
are widelyspaced.
and the l a r g e r t e p e e s
is related
Tepees alsohave
a tendency
t o be stacked.
. .
The l a r g e r t e p e e s o c c u r i n
a belt 1/2 to
314 km shelfward of t h e
Their s i z e decreases away from t h i s b e l t .
CapitanMassiveLimestone.
In the GuadalupeMountains
crests c a n n o t b e t r a c e d i n p l a n
the tepee
view b u t random s t r i k e s s u g g e s t p o l y g o n a l p a t t e r n s .
strata i n Morocco, AsseretoandKendall
fo&,ng
(1977)documented
t e p e e crests
megapolygons, 1 t o 6 m i
n diameter.Sheetcrackfracturing
of beds i n tepees i s comon.
These sheet cracks are u s u a l l y f i l l e d
i n a complex manner with eogenetic
The core of most tepees
and s h e e t c r a c k s f i l l e d
the tepees.
cement a n d / o r i n t e r n a l s e d i m e n t .
is composed o f f e n e s t r a l l a m i n a t e d r o c k s
with cement and internalsediment.Sediments
in intertepee depressions generally
wedge o u t a g a i n s t t h e f l a n k s
generally localized
reported that
the p i s o l i t e - r i c h strata are
i n the i n t e r t e p e e d e p r e s s i o n s .
Holocene tepees have been
Shinn(1969)
of
was syndepositional.
This i n d i c a t e s that tepeeformation
Esteban and Pray(1977)
ments.
In J u r a s s i c
documented i n t h r e e d i f f e r e n t environ-
documented s u b t i d a lt e p e e s
the Persian Gulf.Price(1925),
documented t e p e e s i n s u b a e r i a l
i n thesediments
Reeves (1970)and
of
otherauthorshave
terrestrial c a l c r e t e s o i l s , c a l i c h e .
'
39
Figure 23.
Outcrop of l a r g et e p e ei n Yates Formation.Outcrop
occurs 114 km east of Rattlesnake Canyon and along
s t r i k e w i t h S e c t i o n F.
40
Figure 24.
Outcrop showing a small tepee. Outcrop occurs at
Section C. White circle is 2 cm in diameter.
41
i n the sedimentsofthe
Evamy (1973) r e p o r t e d p e r i t i d a l t e p e e s
Persian Gulf.
Oomparison of the f a b r i c of t h e d i f f e r e n t t y p e s o f
tepeesto
Holocene
the tepees i n t h e Permian strata suggested to Assereto and
Kendall (1977) t h a t t h e Permian tepees are of a p e r i t i d a l o r i g i n .
S u b t i d a l t e p e e s are g e n e r a l l y composed of s k e l e t a l c a l c a r e n i t e s w i t h
a complex h i s t o r y ofsubmarinecementationandboring.Fenestral
f a b r i c was notobserved
i ns u b t i d a lt e p e e s .
Caliche t e p e e sa l s o
lack fenestral fabric.
Smith(1974a)
and Dunham (1972) i n t e r p r e t t e p e e s t r u c t u r e s t o
b e the r e s u l t ofexpansion.Smith(1974a)
(1977) i n t e r p r e t t h e c a u s e
and EstebanandPray
of expansion as t h e r e s u l t
e r t e d by penecomtemporaneous growth of
Assereto and Kendall (1977)
earlyphasedesiccationcontraction,
In an
i n the p e r i t i d a l zone, produced
crests.
t5e polygonalpattern.oftepee
d e s i c c a t i o nt oh a v er e s u l t e d
as a two-phase process, an e a r l y
and a later expansionphase.
desiccationcontractionphase
ex-
a r a g o n i t e or p o s s i b l y magnesian
c a l c i t e cement d u r i n g l i t h i f i c a t i o n .
i n t e r p r e t e d the formation of tepees
of forces
The a u t h o r i n t e r p r e t s t h e
from p e r i o d i c s u b a e r i a l e x p o s u r e .
s u g g e s t that the exposure w a s longer i n d u r a t i o n t h a n t h a t
I
needed t o
produce f e n e s t r a lf a b r i c .F r a c t u r e s ,u n f i l l e ds h e e tc r a c k s ,
formed
by this d e s i c c a t i o n c o n t r a c t i o n are then enlarged during the
later
expansionphase
of tepeeformation.
They are enlargedbymoisture
s w e l l i n g and by the f o r c e e x e r t e d d u r i n g c r y s t a l l i z a t i o n
cements.
The desiccationphase
of tepeeformationoccurs
of carbonate
i n the
42
intertidal and/or supratidal environments.
The expansion phase of
tepee formation can occur anywhere i n a peritidal environment.
author suggeststhatthelarge
tepees indicates
The
amounts of cements associated with
a subtidal dominance during theexpansionphase.
.. .
.
43
DIAGENESIS
Introduction
D i a g e n e s i sw i t h i ns h e l f
purpose of
strata is extensive.
It w a s n o t t h e
the writer t o d e a l with a l l of t h e a s p e c t s of diagenesis
or t o ,treat them i n d e t a i l , b u t
my observations permit
some d i a g e n e t i c
The numerous articles on thediagenesisofthe
interpretations.
Permian strata t e s t i f y t o
its complexity.
In t h e s e c t i o n on rock
f a b r i c s , the d i a g e n e t i cf a b . r i c s ,t e p e e s ,s h e e tc r a c k s ,
molds were b r i e f l y d i s c u s s e d .
. .
In t h i s s e c t i o n ,
and e v a p o r i t e
major a s p e c t s of the
cement, p o r o s i t y , and internal sediments associated with these feat u r e s a n d . w i t h the strata w i l l be discussed.
Cements
The most s p e c t a c u l a r cements are d e v e l o p e d w i t h i n t h e l a r g e
(5-10 cm) s h e e tc r a c k s
Cement t y p e sp r e s e n ti n
i n tepeecores.
s h e e t c r a c k s are 1) radialfibroushemisphoroids,
fibrouscrust,
3) l a m i n a t e d c r u s t s
2) mammillary
and 4 ) sparryequant
calcite.
Assereto and Kendall (1977) described the f t b r o u s cements as pseudofibrous.
They describedpseudofibrous
cement as, "...sparry
pseudomorphing e l o n g a t e f i b r o u s c r y s t a l s ,
c r o s s s e c t i o n and havesquare
calcite
which are hexagonal i n
o r featheryterminations".
Assereto (1974) i n t e r p r e t e d the f i b r e s ' s q u a r e t e r m i n a t i o n s
Folk and
as an
i n d i c a t i o n t h a t the f i b r o u s c r y s t a l s were o r i g i n a l l y a r a g o n i t e that
has i n v e r t e d t o calcite.
Cements within v o i d s o t h e r t h a n s h e e t c r a c k s
form smaller masses
and are n o t a s - s p e c t a c u l a r b u t . a r e - q u a n t i t a t i v e l y more important i n
44
the rock.
The cements within i n t e r p a r t i c l e , i n t r a p a r t i c l e ,
f e n e s t r a lp o r e s
are generallydolomite.
destroyed mostof
The d o l o m i t i z a t i o nh a s
the o r i g i n a l c r y s t a l f a b r i c . .
the o r i g i n a l f a b r i ' c
are p r e s e n t , f o u r
pachousbladedtofibrous,
and
However, g h o s t s of
cement textures occur:
1) iso-
2) m i c r o c r y s t a l l i n e , 3) microspar,
4 ) s p a r r y . ' I n t h e more basinward strata the cement i s calcite.
Sheet Crack Cements
"
RadialFibrousHemispheroids
-
The radial fibrous hemispheroids
composed of calcite f i b r o u s crystals or dolomiteghosts
c r y s t a l s , 10 t o 30 nun l o n g t h a t
"drusefan"
on the f l o o r s and r o o f s - o f s h e e t c r a c k
These hemispheroids are found
cavities.
I observed that
are more comon i n thebasinwardportionsof
thesehemispheroids
theshelf.
of f i b r o u s
This i s the
form a r a d i a t i n g f a n .
cement of Dunham (1972).
are
Some hemispheroidsoccuron
. .
a floor.ofinternalsediment
and are s u b s e q u e n t l y o v e r l a i n b y . a l a y e r o f i n t e r n a l s e d i m e n t .
The
penecontemporaneous . n a t u r e of the internal sediment, as shown by
the presence of Guadalupian age b i o t a (see d i s c u s s i o n o n i n t e r n a l
sediment),indicates
that the radial fibrous hemispheroids
penecontemporaneous o r i g i n .
Where p r e s e n t , this cement type i s
u s u a l l y the earliest cement p r e c i p i t a t e d i n a sheet crack.
i t is n o t p r e s e n t
i n a l l s h e e tc r a c k s .
11-15, and 11-16.) andEsteban
are of
However,
Dunham (197.2, Figures 11-11,
and Pray(1977,Figure
11-12c) have
excellent photos of t h i s cement type.
Ginsburg and James (1976) reported the occurrence
fibroushemispheroidsofaragonite,("botryoidalaragonite",
of r a d i a l
their
45
term), w i t h i n cavities i n Holocene reef
B r i t i s h Honduras.
wall limestones i n Belize,
wall limestone.
s i d e s , and r o o f s , of c a v i t i e s w i t h i n t h e r e e f
Radial fibrous hemispheroids
Limestone.
the f l o o r s ,
These r a d i a lf i b r o u sh e m i s p h e r o i d sl i n e
are abundant within the Capitan Massive
Babcock, Pray,andYurewicz(1977)andSchmidt
i n t e r p r e t these hemispheroids to be of
(19771
a subtidal marine origin.
Dunham (1972) compared t h e morphology of t h i s cement t o s t a l a c t i t e
and stalagmite growthsformed
caves.
i n f r e s h water vadose conditions
The writer considersthe.evidence
acceptable.
in
of a subniarine o r i g i n more
were
The r a d i a lf i b r o u sh e m i s p h e r o i d si ns h e e tc r a c k s
probably precipitated during
a rise i n sea level t h a t f l o o d e d t h e
tepees.
Mammillary Fibrous Crusts
-
Mammillary f i b r o u s c r u s t . cement c o n s i s t s
of calcite laminae. and dolomite. ghosts of laminae of f i b r o u s c r y s t a l s
o r i e n t e dp e r p e n d i c u l a rt o
laminaerange
the s u r f a c e of d e p o s i t i o n .I n d i v i d u a l
i n t h i c k n e s s . f r o m 0.1 t o 5
t h i c k as 4 cm.
mm. The c r u s t may b e as
This cement type commonly, butnoteverywhere,
anisopachousliningon
the walls of a s h e e t c r a c k .
forms
Dunham (1972)
noted that some of these f i l l i n g s are asymmetric, the floor deposits
are t h i c k e r t h a n
i n them.
the roof deposits and have
However, closeexamination
more internal sediment
i n t h e f i e l d reveals thatthe
reverse s i t u a t i o n can also occur, roof deposits thicker than
d e p o s i t s (cf. EstebanandPray,1977;FigureII-12a).
floor
Internal
sediment commonly o v e r l i e s o r i s incorporated i n the c r u s t s on t h e
f l o o r so f
sheet cracks.
The penecontemporaneous n a t u r eo ft h e
46
internal siediment i n d i c a t e s that t h i s is an eogenetic cement.
Dunham (1972) compared t h e morphologyof
t o growths l i n i n g t h e
walls of caves.
this f i b r o u s cement
On t h e b a s i s of their s i m i l a r i t y
cements t o h a v e p r e c i p i t a t e d i n
he interpreted the fibrous crust
f r e s h water vadose.conditions.AsseretoandKendall
that t h i s cement was s i m i l a r t o
(1977) noted
the a r a g o n i t e cements t h a t e n c r u s t
The writer f e e l s that the isopachousnature
g r a i n s i n a beachrock.
of most of these f i b r o u s c r u s t s i n d i c a t e s
a p h r e a t i c subaqueous
origin.Folk(1974)proposedthattheformationofaragonitefibres
generallyrequires
water with a Mg/Ca r a t i o of 211 o r more.
c o n d i t i o n most commonly occurs i n m a r i n e t o h y p e r s a l i n e
Laminated.-
Cement
-
The crinkled laminae
sparlayers
Crusts may be as t h i c k as 3 cm.
. .
andKendall,1977).
In the f i e l d t h i s t y p e
c o u l d e a s i l y be m i s t a k e n f o r a laminatedsediment.
cement can be found 1.ining the
Dunham (1972,Figures
and k c r o s p a r
are 0.02 t o 0.5 mm t h i c k and the k c r o -
are 0.1 t o 3 mm t h i c k ( c f . A s s e r e t o
laminated crust
waters.
Laminated c r u s t cement c o n s i s t s o f , a l t e r -
n a t i o n s of c a l c i t e or d o l o m i t e m i c r i t i c c r i n k l e d l a m i n a e
layers.
This
of cement
However, t h e
roofs of c a v i t i e s .
11-15 and 11-16) has two photographs of t h i s
cement type.
In some 1 o c a l i t P e s t h i s t y p e
ofcementdoes
cracks, b u t forms a c o a t i n go v e rs e v e r a l
not line sheet
particles.
The laminated
c r u s t s may form a mammillary o r b o t r y o i d a l c o a t i n g t h a t
o v e r l a i n by sediments.Examination
and Pray,1977;Figure
is immediately
of geometricrelations(cf.Esteban
V-2b and V-2c) i n d i c a t e that the laminated
47
crust'cement probably
formed a c o a t i n g or e n c r u s t a t i o n on t h e
depositionalsurface.EstebanandPray
(1977) have documented t h a t
their botryoidal. cement is t h i c k e s t andmostabundanthigh
on t h e
f l a n k s of tepees and is m o s t l y a s s o c i a t e d w i t h p i s o l i t i c r o c k s .
The writer i n t e r p r e t s t h e l a m i n a t e d c r u s t
t o A s s e r e t o andKendall's
cement t o b e e q u i v a l e n t
(1977) f e s t o o n e d c e l l u l a r c r u s t
Esteban and Pray's (1977) b o t r y o i d a l cement.
cementand
Relationshipswith
internal s e d i m e n t i n d i c a t e that the laminated crusts
formed e a r l y .
%
(1977) noted that t h i s t y p e
AsseretoandKendall
of cement had
features similar to those described for Holocene supratidal splash
or spray zone cements of the Persian Gulf.
this observation.
.I was n o t a b l e t o c o n f i r m
These cements in t h eP e r s i a n
Gulf e n c r u s tt h e
s u r f a c e and cavities within beach rock (Purser' and Loreau, 1973).
AsseretoandKendall
:,.
(1977) reported that the microspar laminae
commonly show ghosts of f i b r o u sc r y s t a l s .
microspar resulted
'
fromneomorphism
They p o s t u l a t e dt h a tt h e
of an o r i g i n a l , p o s s i b l y a r a g o n i -
t i c cement.
Sparry Equant Calcite
-
The sparry 'equant c a l c i t e cement i s composed
of calcite c r y s t a l s r a n g i n g
from 0.03 t o 1 mm i n diameter.
as the l a s t cement t o f i l l - t h e p o r e s .
The o r i g i n of t h i s cement i s
probably the same as that of t h e s p a r r y e q u a n t
types of pores.
Other Cement-
It occurs
cement found i n o t h e r
Its o r i g i n i s d i s c u s s e d i n the n e x ts e c t i o n .
(Those n o t found i n sheet cracks)
Isopachous Bladed to Fibrous Cement
cement consists of ghosts
-
The isopachous bladed to fibrous
o f fibroustobladedcrystals
that range
48
(See Figures 25 and 2f i)
from 0.1 t o 1 mm i n l e n g t h .
.
The isopachous
cement p r e f e r e n t i a l l y o c c u r s i n t h e c o a r s e r g r a i n e d r o c k s ,
more basinwardrocks.
of “calcite
sal. (1976)
James
isopachous bladed
British Honduras.Submarine
hasbeen
and t h e
reported t h e occurrence
cement i n shallow reefs of Belize,
a r a g o n i t i ci s o p a c h o u sf i b r o u s
sal.
documented by James
(1976)and
cement
Schroeder(1972).
Evamy (1973) r e p o r t e d the o c c u r r e n c e o f f i b r o u s a r a g o n i t e c r y s t a l s
the p o r e s o f i n t e r t i d a l r o c k ;
isopachously lining
M i c r o c r y s t a l l i n e Cement
- Microcrystalline
micrite-sized crystals, ranging
cement is composed of
from 1 t o 4 microns i n diameter.
The cement fo,rms rims around pores and around grains and therefore,
can p r o b a b l y b e i d e n t i f i e d
.as
d e p o s i t i o n a l c l a s t i c element,
a c h e m i c a l p r e c i p i t a t e and n o t a
(See Figures 27 and 28).
This cement
is mre common i n the coarsergrainedrocks.Microcrystalline
cement has been found
ments.
i n the Holocene i n s e v e r a l d i f f e r e n t environ-
s.(1971),
Land (1971),
Ginsburg
and James
sg . (1976),
r e p o r t e d Mg-calcite m i c r o c r y s t a l l i n e cements i n Holocene r e e f s .
Moore (1971),Robertsand
Moore (1971),andTaylor
reported aragonitic microcrystalline
beachrocks.
and I l l i n g (1971)
cement i n Holocene i n t e r t i d a l
Steinen (1974) r e p o r t e dm i c r o c r y s t a l l i n e
f r e s h water vadoseenvironment.
Dunham (1972) reportedmicrocrystal-
l i n e meniscus cements w i t h i n s h e l f
Meniscuscements
by Dunham (1971).
cement i n t h e
strata i n the GuadalupeMountains.
have been documented i n t h e f r e s h water vadose zone
%e author interprets the m i c r o c r y s t a l l i n e cement
t o probably have originated
i n a variety of environments.
49
Figure 25.
Thinsectionphotomicrograph
showingisopachousbladed
cement l i n i n g a pore i n a nonskeletal grainstone,
Rock 5 p e 2.
(VW 1666/9).
50
Figure 26.
Thinsectionphotomicrographof
a f e n e s t r a ln o n s k e l e t a l
packstone, Rock Type 4 . Fenestrae are l i n e dw i t ha n
isopachouscement,then
f i l l e d w i t h a l a t e sparry
equant cement. (VW 1666/10).
51
Figure 27.
Thin section photomicrograph showing microcrystalline
( W 1666/11).
cement (M) and sparry equant cement. V
52
Figure 28.
Thin section photomicrograph of a fenestral skeletalnonskeletal grainstone, Rock Type 3. Pores are filled
with microcrystalline cement (MC) and microspar cement
(MS). The microcrystalline cement is the darker
cement. (VW 1666/12).
53
Microspar Cement
-
Microspar consists
of s u b h e d r a l t o a n h e d r a l
from 5 t o 20 microns i n diameter(Folk,1965).
equantcrystalsranging
It occurs 'more commonly i n t h e finer grainedrocks.
(See Figure28).
S t e i n e n (1974) documented the occurrence of calcite microspar i n t h e
freshwaterphreaticenvironment.Folk
(1965) i n t e r p r e t e dm i c r o s p a r
t o b e the r e s u l t of neomorphism ofmicrite.TaylorandIlling
(1971)
documented within the submarine environment
andShinn(1969)have
neomorphism o f o r i g i n a l a r a g o n i t e f i b r o u s
and m i c r i t i c cement t o
The microspar cement i n t h e s h e l f
Mg-calcite microspar.
the GuadalupeMountains
probably evolved
strata of
i n a variety of different
environments.
SparryEquant
Cement
- Sparry equant
t oa n h e d r a l ,e q u a n t . c l e a r
microns i n diameter.
calcite c r y s t a l sr a n g i n g
from 30 t o 80
'
a time sparryequant
preted to have been precipitated
cement w a s i n t e r -
i n the freshwater phreatic environ-
However, Schroeder(1972)reportedtheoccurrenceofsparry
c r y s t a l s o f Mg-calcite i n Holocene, Brrmuda cup reefs.Schroeder
(1973) a l s o documented s p a r r y calcite forming a meniscus o u t l i n e i n
P l e i s t o c e n e Bermuda reefrock.
This i n d i c a t e s that s p a r r y calcite
can also form i n thevadoseenvironment.Folk(1974)hasinterpreted
sparry equant calcite t o form i n waters with low M g h a i o n r a t i o .
This condition is p r e s e n t i n the freshwater phreatic environment.
Folk also noted that this condition occurs
waters.
.
It occurs as the l a s t cement i n t h e larger pores.
(See Figure 26 and27).For
ment.
cement is composed of subhedral
i n connate subsurface
54
I n t e r n a l Sediment
Internal sediment is comon i n s h e e t c r a c k s .
i n some f e n e s t r a l p o r e s .
Three typesof
It i s a l s o p r e s e n t
internal sediment are
p r e s e n t : 1) r e d i r o n s t a i n e d d o l o m i t e p e l l e t s ,
2) d o l o m i t e p e l l e t
s i l t , 3) microcrystallinedolomite.(SeeFigure29).
Mast of the
internal sediment shows f a i n t p a r a l l e l l a m i n a t i o n .
In some l o c a l i t i e s
i t is normalgraded.
Assereto and Kendall (1977)and
Dunham (1972) r e p o r t e d f i n d i n g
internal sediment with skeletal grains (dasycladacean algae, ostracods,
and Tubiphytes) derived penecontemporaneously from the surrounding
sediments.
As noted i n t h e p r e v i o u s s e c t i o n
on cements, i n t a m a l
sediment is commonly i n t e r l a m i n a t e d with cement.
forms the micritic laminae
l i n ed o l o m i t ei n t e r n a ls e d i m e n tc o m o n l y
t h a t are p r e s e n t i n t h e l a m i n a t e d c r u s t
is not common.in the mostbasinward
study area.
The microcrystal-
cement.
I n t e r n a ls e d i m e n t
or shelfward portions
of t h e
It i s most common i n the f e n e s t r a l and p i s o l i t i c r o c k s
of the s h e l f crest.
Assereto and Kendall
dolomitepelletsto
formsfrom
(1977) i n t e r p r e t e d r e d i r o n s t a i n e d
be terra rosa.
Terra r o s a i s a r e d s o i l which
s u b a e r i a ls o l u r i o no fl i m e s t o n e .
Terra r o s a is a common
f i l l i n shallow subsurface (epigenetic) cracks of emergent carbonate
lithified rocks
i n the Bahamas,. Yucatan, and Florida (Roehl, 1967).
I was n o t a b l e t o v e r i f y
this i n t e r p r e t a t i o n .
Porosity
Several porosity types
are p r e s e n t i n t h e r o c k s
of t h e s t u d y
'
' '
'
55
.Figure 2 9 .
Thinsectionphotomicrograph
showing s h e e t c r a c k f i l l e d
w i t h cement and t h r e e t y p e s of i n t e r n a l s e d i m e n t ;
red iron stained dolomite pellets
(R), dolomitepellet
s i l t ( S ) , and m i c r o c r y s t a l l i n ed o l o m i t e (M).
(VW 16661’13).
56
interval: 1) f e n e s t r a l , 2) i n t e r p a r t i c l e , 3) moldic, 4 ) burrow,
5 ) i n t r a p a r t i c l e , 6) vug, 7) s h e e t crack, and 8) f r a c t u r e .
Only
t h e f e n e s t r a l and i n t e r p a r t i c l e p o r o s i t y i s p r e s e n t i n an amount of
economic s i g n i f i c a n c e i n a petroleum reservoir rock.
Porosity associated with fenestral fabric
15).
and bestpreserved(SeeFigure
is t h e most abundant
Some of the f e n e s t r a l p o r e s
have f l a t f l o o r s .
This i s the r e s u l t of i n t e r n a l s e d i m e n t p a r t i a l l y
f i l l i n g the void.
Some of the vug p o r o s i t y was p r o b a b l y o r i g i n a l l y
f e n e s t r a l p o r o s i t y that has been enlarged
by s o i u t i o n .
I n t e r p a r t i c l e p o r o s i t y i s mostabundant
i n the coarser grained
The l a r g e . s i z e o f t h e i n t e r p a r t i c l e
p i s o l i t e strata (SeeFigure
32).
pores i n these beds enabled
them to. remain open during cementation.
Moldic porosity is l a r g e l y , t h e r e s u l t of s o l u t i o n o f ' a r a g o n i t e
gastropods, dasycladaceans and evaporite minerals
drite).Evaporite
onlythe
(gypsum and anhy-
in
molds are c r y s t a l l o t o p i c or nodularandoccur
mostshelfward
strata.
See Figure 2 0 ' f o r a photograph.
Evaporites are: discussed i n more d e t a i l i n the next s e c t i o n .
Burrow p o r o s i t y was described i n the s e c t i o n on rock fabrics.
See Figure 19 f o r a photograph.
1 n t r a p a r t i c l e . p o r o s i t y o c c u r s i n minor amounts and only within
the l a r g e r g a s t r o p o d s and some dasycladacean' aglae.
Vug p o r o s i t y i s n o t common.
Most ofthe
vug porosityappears
t o b e the result of enlargement by solution of other types of pores.
S e e Figure 23 f o r a photograph.
Sheet crack porosity occurs.only
i n the very large sheet
cracks.
57
Most.of the o r i g i n a l p o r o s i t y i n the .sheet crack is f i l l e d with
cement a n d / o r i n t e r n a l s e d i m e n t .
F r a c t u r ep o r o s i t yo c c u r si n
probably originated during
small amounts.These
fractures
the u p l i f t of t h e GuadalupeMountains
i n the l a t e Pliocene or e a r l y P l e i s t o c e n e .
Evaporites
is p r e s e n t i n t h e
Evidence of e v a p o r i t e s , gypsum and anhydrite,
formof
c r y s t a l l o t o p i c andnodular
molds .(See Figure 20).
l o t o p i c molds are t h e more abundant of the two' types.
Some of the
c r y s t a l l o t o p i c molds are l e n s or disc-shaped, suggestive
In the study area e v a p o r i t e molds were found only
Crystal-
of gypsum.
i n measured
The molds are r a n d o m l y . d i s t r i b u t e d i n mudstone-wackestone
s e c t i o n F.
bedsapproximately
30 cm t h i c k .
The bedsunderlying
w i l l commonly have a c r i n k l y t o f l a t a l g a l l a m i n a t i o n
and o v e r l y i n g
or burrows.
Beds w i t h e v a p o r i t e molds grade out basinward into a n o n s k e l e t a l
p a c k s t o n e .F e a t u r e si n d i c a t i v eo fd e s s i c a t i o n ,f e n e s t r a lf a b r i c
and mud cracks, are n o t p r e s e n t , i n t h e e v a p o r i t i c b e d s .
Kinsman and Park (1976) described stromatolite structures and
associated evaporites in
PersianGulf.
Holocene sediments.of the Trucial coast,
They described a smooth mat s t r o m a t o l i t e morphology
which r a n g e s f r o m s h a l l o w s u b t i d d
to upper i n t e r t i d a l enV.iro.ments.
In the upper 20 to 30 cm o f t h e i n t e r t i d a l
of discoid
zone the p r e c i p i t a t i o n
gypsum destroys a l l a l g a l s ' c r u c t u r e s .
Butler (1969)and
KendallandSkipwith(1969)described.the
e v a p o r i t e s and the a s s o c i a t e d f a b r i c s of t h e s u p r a t i d a l environment
..
58
evaporite mineral, although
gypsum i s p r e s e n t .
The anhydriteoccurs
masses w i t h a nodular, nodular mosaic,
as bedsand
o r a mosaic
of these f a b r i c s i s p r e s e n t i n the strata of t h e
fabric.Evidence
study area b u t is not abundant.
The a u t h o r i n t e r p r e t s t h e e v a p o r i t e s t o h a v e b e e n p r e c i p i t a t e d
i n a restrictedlagoon.
from hypersalinebrinesforming
The evapo-
rites were p r e c i p i t a t e d w i t h i n s h a l l o w s u b t i d a l , i n t e r t i d a l ,
and
low s u p r a t i d a l s e d i m e n t s .
Emergent Surfaces
A major d i a g e n e t i c f e a t u r e t h a t i s l o c a l l y p r e s e n t
calcrete o r c a l i c h e ,
eredzone,
dolomiteunit
1 t o 5 cm thick, a t thetop
i n the T r i p l e t Unit.
andPray(1977)described
of t h e
This i s ofGuadalupianage.
It is p r e s e n t i n measured s e c t i o n s C, D, and.E.
zone has a reddish pink color
i s a weath-
In the f i e l d t h i s
and a micritic appearance. Esteban
thin s e c t i o n s f r o m t h i s
zone that showed
a l t e r a t i o n of pisolith fragments, microchanneling and microsparitization.
'
Esteban(1976)described
the p r e d o m i n a n t c a l i c h e f a b r i c t o
be a clotted, peloidal micrite with microspar channels and
(SeeFigure
30).
zone a t thetopof
T h i sd e s c r i p t i o n
cracks.
matches the f a b r i c p r e s e n t i n t h e
the T r i p l e t Dolomite.
This supports the i n t e r -
p r e t a t i o n of this zone as a f o s s i l calcrete.
A t the Yates-Tansill c o n t a c t , at an outcrop along
the highway
i n Walnut Canyon, Esteban and Pray (1977) interpreted lithologic
a l t e r a t i o n i n the u n d e r l y i n g r o c k , t o b e a f o s s i l s o i l p r o f i l e .
.. ..
59
Figure 30.
Thinsectionphotomicrographof
a f e n e s t r a ln o n s k e l e t a l
4 , showing i n c i p i e n t c a l i c h e f i c a t i o n .
packstone, RockType
Note t h e m i c r o c h a n n e l i n g a n d c l o t t e d ' t e x t u r e .
(UW 1666/14).
60
The l i t h o l o g i c a l t e r a t i o n o c c u r s
as a p r o g r e s s i v e upward i n c r e a s e
i n t h e upper f o o t of the
in carbonate content
Upper T r i p l e t s a n d s t o n e .
as lensoid nodules,
P a r t of this carbonate occurs
1 t o 3 mm thick.
Thin s e c t i o n s of t h i s , r o c k show microspar replacement
micritic texture, microchanneling, and possible
grains, mottled
calcicutans.Esteban(1977,personal
u s i n gt h i ns e c t i o n s ;f i e l d
may b e d u e t o
communication) n o t e dt h a tt h e
zone as a f o s s i l s o i l c o u l d o n l y b e
interpretation of this
d i dn o tf i n d
of q u a r t z
criteria are n o t s u f f i c i e n t .
any s'imilar zones i n Rattlesnake Canyon.
done
The author
However, this
the recessive weathering of the sandstones.
Thomas (1965), Dunham (1969, 1972),andSmith(1974b)have
p r e t e dt h ep i s o l i t i cr o c k st ob ec a l i c h e .E s t e b a n
interpreted the pisolitic rocks to be
origin.
The authoragreeswithEsteban
and,Pray(1977)
of submarineprimary
particle
and Prayanddiscussesthe
the s e c t i o n on genesis of p i s o l i t i c r o c k s .
subject further in
Smith (1974b) a l s o d e s c r i b e d
the s h e l f strata.
inter-
,
some n o n - p i s o l i t i c c a l i c h e
The n o n - p i s o l i t i c c a l i c h e
was composed of a
rich i n laminar and fibrous carbonate
partly brecciated.upper layer
that changes downward via a crudely nodular
l a y e ri n t ou n a l t e r e dr o c k .
in
crumbly i n t e r m e d i a t e
The a u t h o r examined s e v e r a l o u t c r o p s
the n o n - p i s o l i t i c caliche and concluded t h a t t h e y
of
are n o t c a l i c h e ,
b u t are b r e c c i a s a s s o c i a t e d w i t h t e p e e s .
Dolomitization
Dolomiterocks
'are r e s t r i c t e d t o
of t h e mostbasinward
stones.
the s h e l f strata.. The .rocks
shelf, the shelf edge
In the dolomiticrocks
and t h e b a s i n are lime-
a l l g r a i n s are d o l o m i t eb u tt h e
61
cement may bedolomiteand/or
calcite.
The c r y s t a l s i n g r a i n s re-
placed by dolomite are anhedral and approximately 3 microns i n s i z e .
This c r y s t a l s i z e o b l i t e r a t e s some of the microscopic features
grains but does
not o b l i t e r a t e t h e g e n e r a l o u t l i n e
The a u t h o r i n t e r p r e t s
process.Examinationof
t h ee v i d e n c ef o r
this conclusion.
are p r e s e n t w i t h i n t e p e e
strata:
and, calcite as s h e e tc r a c k
of grains.
an eogenetic
the dolomitization to be
the cements w i t h i n t e p e e
of
strata provides
Two mineralogictypesof
cements
dolomite as i n t e r p a r t i c l e cement
f i l l cement.
The s h e e t c r a c k f i l l i n g
cement was p r e c i p i t a t e d a f t e r ' t h e l i t h i f i c a t i o n n e c e s s a r y f o r s h e e t
the dolomitizationoccurred
crackformationoccurred.Therefore,
b e f o r e the s h e e tc r a c k
cements were p r e c i p i t a t e d .
Dunham (1972)
a t t h i s time.
also interpreted the dolomitization to have occurred
s
Sands tone
, ,
Sandstones are cemented with a dolomite microspar
the microspar present
Locally,there
i n the 'carbonate rocks (See Figure
are p o c k e t so f 2 c a l c i t i c
cement.
31).
P o r o s i t y is p r e s e n t
only i n trace amounts as i n t e r p a r t i c l e p o r o s i t y .
thin s e c t i o n s r e v e a l e d
similar t o
Examinationof
that l o c a l l y the cement may b e r e p l a c i n g
the q u a r t z g r a i n s .
Hull, Jr. (1957) and Dunham (1972) bothnoted
a narrow b e l t , 114 t o 112 km shelfward of the Capitan
Limestone i n which f e l d s p a r c o n t e n t
Massive
was anomalouslylow.
is c o i n c i d e n t with the p i s o l i t e b e l t . O u t s i d e
contentaverages
that t h e r e was
This b e l t
of this b e l t f e l d s p a r
25%, within this b e l t the average is 1%.Dunham
62
Figure 31.
Thinsectionphotomicrograph
of a s i l i c i c l a s t i c sandstone,
RockType
7. Microsparcementandironoxidesoccur
between t h eg r a i n s .
The i r o no x i d e s are t h e opaque
areas i n t h e photo. U
(W 1666/15).
63
(1972) a l s o examined h i s samples f o r k a o l i n i t e c o n t e n t .
that the kaolinite content
was h i g h e r f o r r o c k s w i t h i n t h e b e l t
compared t o r o c k s o u t s i d e o f t h e b e l t .
k a o l i n i t e was p r o b a b l y t h e r e s u l t
duringsubaerialexposure.
He found
as
Dunham concluded t h a t t h e
of a l t e r a t i o n o f t h e f e l d s p a r
I d i dn o ts t u d yt h i sr e l a t i o n s h i p .
.
ROCK TYPES
Rock types were differentiated using several variables,
principally: grain
'type, grain size, grain
. and depositionaltexture.
types to aid
abundance, rock fabrics,
The rocks were separatedintothevarious
i n the recognition of depositional environments and
cyclicsedimentation i n theshelfstrata.Previously,theauthor
described nine lithofacies (see
Someof
Neese and Schwarrz, 1977 i n appendix).
the nine lithofacies are retained,
some were added.
The author will notethese
.lithofacies has been
discarded here
some are discarded,
changes.
and
The term
and replaced by the term "rock
..
type".
q .
.
.
.
.
A t o t a l of eight rock types a r e recognized i n t h e s h e l f s t r a t a
Six carbonate rock types occur:
1) Skeletal grains tones
2) Nonskeletalgrainstones
3) Fenestral nonskeletal-skeletal packstone-grainstone
4 ) Fenestral nonskeletal packstone-grains tone
5 ) P i s o l i t i c packstune-grainstone
6) Peloid muds tone-wackes tone
The other two rock types present are siliciclastic-rich:
7) S i l i c i c l a s t i c sandstone
8) Siliciclas tic-rich peloid wackestone
These eight rock typesaredescribed
characteristics of the different
below.
rocktypes
A summary of the
i s provided i n Table 1.
..
65
Table 1.
Summary of RockType
Characteristics
66
Dolomite. miinor
sa1*its
HiErODpar
67
Rock a,&,
Skeletal
Grainstone
75% o r more are skeletal:Dasycladaceanalgae,
Grainwpe:
gastropods,brachiopods,pelecypods,bryozoans,
sponges,echinodermfragments,Tubiphytes.
Nonskeletal grains
are p e l o i d s a n d i n t r a c l a s t s .
Most g r a i n s are well rounded.
Depositional Textures:
Grainstonedominant,
local. occurrences of
packstone interbeds.
Sedimentarystructures:
Abundant occurrencesof
10 t o 20 d e g r e e s d i p , c r o s s l a m i n a t i o n
low a n g l e ,
i n t a b u l a r and
wedge shaped sets 10 t o 30 cm thick (See Figure
P a r a l l e ll a m i n a t i o n
i s a l s o abundant..
32).
Beds are 3 to 5 m
thick.
Rock Fabrics:
None
Mineralogy:Predominantlylimestone,shelfwardpatches
of dolomite
occur.
Diagenetic features :
Cements:
Isopachousbladed
and f i b r o u s calcite, sparryequant
calcite, traces of microspar clacite.
Porosity:
.
Vug, less than 10%.
Internal Sediment:
Other:
.
None
Abundant neomorphism. of , g r a i n s i n t o mScritic grains.
OtherFeatures:Coatings'on
many g r a i n s i n thecross-sets.Coatings
are a c c r e t i o n a r ya n d f o ro n c o l i t i c .
This rocktype
equivalent to the Skeletal-rich limestone facies
and Schwartz ,(1977).
is
i n Neese
68
Figure 32.
Outcropphotograph of
g r a i n s t o n e , RockType
10 t o 15 degrees i n a
occurs i n S e c t i o n B.
crossbedding i n a n o n s k e l e t a l
2. Cross bedshave a d i p of
basinwarddirection.Outcrop
Photographtaken by LloydPray.
69
I I
Rock Type 2, Nonskeletal Grainstones
Grain Type:
75% or more are nonskeletal:peloidspredominantly,
and intraclasts.
S k e l e t a lg r a i n s
are dasycladacean algae,
Most g r a i n s are well rounded.
foraminifera,andgastropods.
are
DepositionalTextures:Grainstones,localpackstonelaminae
present.
Sedimentary s t r u c t u r e s :
(See Figure
Abundant o c c u r r e n c e so fp a r a l l e ll a m i n a t i o n
33), and l o c a l o c c u r r e n c e s of cross lamination,
with 10 t o 20 degrees dip
5 t o 10 cm t h i c k .
Rock f a b r i c s :
i n t a b u l a r and wedge shaped sets
Beds are .1 t o 2 m t h i c k .
None
Mineralogy:Predominantlydolomite,basinwardpatchesoflimestone
occur.
Diagenetic features:
Cements:
Microspardolomite,sparryequant
calcite, l o c a l i z e d
patches of isopachous bladed to fibrous dolomite.
Porosity:
Vug, less than 10%.
I n t e r n a l Sediment:
None.
Other f e a t u r e s : A c c r e t i o n a r y c o a t i n g l o c a l l y p r e s e n t o n
This rock type w a s not previously described
some grains.
i n Neese and
Schwartz . (1977).
Rock Type 3, Fenestral Nonskeleeal-Skeletal Packstone-Grainstone
Grain Type:
S k e l e t a l and n o n s k e l e t a l i n aboutequalproportions.
Local occurrences of skeletal-rich beds, especially
c l a d a c e a na l g a er i c hb e d s .S k e l e t a lg r a i n s
are:
daceanalgae,.gastropods,foraminifera,ostracods,and
dasydasycla-
:-
70
I
Figure 33.
Parallel l a m i n a t i o n i n a n o n s k e l e t a lg r a i n s t o n e ,
Rock Type 2 . Sample is from S e c t i o n B.
(VW 1666/16).
71
are:
thinshelledpelecypods.Nonskeletalgrains
p e l o i d s , intraclasts, and p e l l e t s .
DepositionalTextures:Grainstonesandpackstones
i n e q u a l propor-
tions.
Sedimentarystructures:
Rock f a b r i c s :
Beds are 112 t o 2 m thick.
None.
Abundant f e n e s t r a lf a b r i c ,a l t h o u g hl o c a l l ya b s e n t .
Sheet cracks and tepees are a l s o p r e s e n t .
is p r e s e n t i n b o t h
the cores of tepees
depressions.Localoccurrences
This rocktype
and t h e i n t e r t e p e e
of burrows.
Mineralogy:
Dolomite.
Diagenetic features
Cements:
;
Microcrystallinedolomitespar,dolomitemicrospar,
sparryequant
calcite.
W i t h i ns h e e tc r a c k s :r a d i a lf i b r o u s
calcite and dolomite hemispheroids,
calcite anddolomite
P o r o s i t y :F e n e s t r a l ,
crusts, sparry equant
calcite.
burrow, i n t r a p a r t i c l e( w i t h i ng a s t r o p o d s ) ,
vug,approximately
Internal Sediment:
mammillary f i b r o u s
10% t o t a l .
r e d i r o n s t a i n e dd o l o m i t ep e l l e t s ,d o l o m i t e
pellet silt.
Other f e a t u r e s :
None.
This rocktype
was previouslydescribed
the Mixed s k e l e t a l - n o n s k e l e t a l d o l o m i t e f a c i e s
as
i n Neese
and Schwartz (1977).
Rock
I
_
6,
Fenestral Nonskeletal Packstone-Grainstone
Grain Type: . 7 5 % o r more are n o n i k e l e t a l :p e l o i d s ,
intraclast,
p e l l e t s , and some s c a t t e r e dp i s o l i t h s .S k e l e t a l
grains
ostracods.
-DepositionalTextures:Packstoneandgrainstone
Sedimentary. ' s t r u c t u r e s :
Rock f a b r i c s :
i n e q u a lp r o p o r t i o n s .
Beds 114 t o 1 m t h i c k .
None.
Abundant f e n e s t r a lf a b r i c ,
This rock type occurs both
sheet cracks, andtepees.
i n t h e c o r e s of tepees and
intertepeedepressions.Localoccurrences
a l g a ll a m i n a t i o n .
of burrows and
Trace amounts of c r y s t a l l o t o p i c and
nodular, gypsum and. a n h y d r i t e molds in t h e most shelfward
portions.
Mineralogy: . Dolomite.
Diagenetic features:.
Cements:
Hicrocrystalline dolomitespar,dolomitemicrospar,
sparryequant
calcite.
Within sheet c r a c k s :r a d i a l
f i b r o u s calcite and dolomitehemispheroids,
mammillary
f i b r o u s calcite .and dolomite crust, sparry equant
P o r o s i t y :F e n e s t r a l ;
calcite.
burrow, i n t r a p a r t i c l e( w i t h i ng a s t r o p o d s ) ,
moldic(evaporite),
vug,and
s h e e tc r a c k .T o t a l
amount
of p o r o s i t y is 10%.
Internal S e d i m e n t :r e di r o ns t a i n e dd o l o m i t ep e l l e t s ,
dolomite pellet silt.
Other f e a t u r e s :
None.
This rock type was previouslydescribed
the Non-skeletal. dolomite
as
i n Neese and Schwartz (1977).
Rock Type 5, Pisolitic Packstone-Grainstone
Grain Type:
75% or more are p i s o l i t h s .N o n s k e l e t a lg r a i n s
p i s o l i t e s ,p e l l e t s ,p e l o i d s ,
and i n t r a c l a s t s
.
are:
Skeletal
73
g r a i n s are notabundant.Dasycladacean
algae are p r e s e n t
as nuclei of some p i s o l i t h s .
DepositionalTextures:Grainstonesandpackstones.Grainstones
are predominant.
Sedimentary structures:Inversegradedbedding
i s l o c a l l yp r e s e n t .
Beds are 114 t o 1 m thick.
Rock f a b r i c s :S h e e tc r a c k s ,
some as t h i c k as 10 cm.
type is mainly localized
i n the intertepee depressions.
There are local occurrences
of p o l y g o n a l f i t t i n g o f
For a more completedescription
pisoliths.
This rock
see t h e s e c t i o n
on pisolite genesis.
Mineralogy:
Dolomite.
.
Diagenetic features :
Cements:
Dolomite and c a l c i t e microspar,sparryequant
calcite.
calcite
Within s h e e tc r a c k s :r a d i a lf i b r o u s
anddolomitehemispheroids,
anddolomite
matmnillary f i b r o u s calcite
crusts, laminated c a l c i t e and/ordolomite
crusts, sparryequant
calcite.
10 t o 15%.
P o r o s i t y :L o c a lo c c u r r e n c e so fi n t e r p a r t i c l e ,
Internal S e d i m e n t : ' r e d i r o n s t a i n e d d o l o m i t e p e l l e t s ,
dolomite pellet silt, microcrystalline dolomite.
Other f e a t u r e s :
See t h e s e c t i o n on p i s o l i t e g e n e s i s
completediscussion.
This rocktype
for a more
was described
previously as the P i s o l i t h - r i c h d o l o m i t e f a c i e s
andSchwartz
(1977).
i n Neese
'.
74
I
Figure 3 4 .
.
I
Polished slab of p i s o l i t i c g r a i n s t o n e , Rock Type 5.
Note t h e i n t e r p a r t i c l e and i n t r a p a r t i c l e p o r o s i t y .
(UW 1666/17).
75
Rock Type 6, P e l o i d Mudstone-Wackestone
Grain Type:
Nonskeletalgrains
are predominant.
p e l o i d s ,o t h e rn o n s k e l e t a lg r a i n s
g r a i n s are:
ostracods
75% o r more are
are p e l l e t s .S k e l e t a l
c a l c i s p h e r e s ,e n c r u s t i n gf o r a m i n i f e r a ,
and
.
DepositionalTextures:
Dominantlywackestonegrading
i n t o mudstone
locally.
S e d i m e n t a r ys t r u c t u r e s :P a r a l l e l a m i n a t i o no c c u r sl o c a l l y .
Beds
are 5 t o 30 cm t h i c k .
Rock fabrics:Localoccurrencesofburrows,
a l g a l lamination, and
gypsum and a n h y d r i t e molds ( b o t h c r y s t a l l o t o p i c and small,
2 to 5
mm,
nodular molds).. . In the basinward portions
there are thin b e d s w i t h l a m i n a r f e n e s t r a l f a b r i c .
..
Mineralogy:
Dolomite.
,, ..
Diagenetic f e a t u r e s :
Cements : Dolomitemicrospar.
Porosity:
Moldic; c r y s t a l l o t o p i c andnodularevaporite
Localoccurrencesofburrowporosity.Total
molds.
amount of
p o r o s i t y i s less than 5%.
Internal Sediment:
Other f e a t u r e s :
None.
None.
This .rocktype
was previouslydescribed
as
the Mud-supported d o l o m i t e f a c i e s i n Neese andSchwartz
(1977).
RockType
7,Sandstone
Grain D p e :
(Siliciclastic)
S i l i c i c l a s t i c s , s i l t t ov e r yf i n es a n d
size.
76
DepositionalTextures:
are subangular.
Well s o r t e dg r a i n s
These
the c l a s s i f i c a t i o n of
rocks are q u a r t z a r e n i t e s u s i n g
Dott(1964)Sedimentarystrucutres.:.Localoccurrences
of p a r a l l e ll a m i n a t i o n .
Also, l o c a l o c c u r r e n c e s i n u p p e r p o r t i o n s
5 t o 10 cm t h i c k , sets
of beds of small,
o f currentripple(?)cross
lamina-
t i o n . w i t h 10 t o 20 degrees dip.
Rock f a b r i c s :
None.
Mineralogy:Predominantlyquartz,
trace amounts ofpotassium
feldspar,muscovite,biotite,tourmaline,zircon,and
kaolinite
.
Diagenetic features:
Cements:
Predominantlydolomitemicrosparwithlocalpa'tches
. .
. .
of c d c i t e microspar
P o r o s i t y :I n t e r p a r t i c l e ,
I n t e r n a l Sediment:
Other f e a t u r e s :
less than 5%.
None:
Iron s t a i n i n g .I r r e g u l a r
and s p h e r i c a li r o no x i d e
concretions, 1 t o 4 cm i n s i z e occur (See Figure 35).
Also, i r o n o x i d e
crusts, 1/2 t o 1 cm t h i c k , forms on
some beddingplanes.Thisrocktype
w a s previously
described as the Sandstone ( s i l i c i c l a s t i c ) f a c i e s i n
Neese and Schwartz (1977).
Rock Type
8, Siliciclastic-R&&
Peloid Wackestone
Grain Type:, S i l t t o v e r y f i n e s a n d s i z e
lyquartz.Carbonategrains
s i l i c i c l a s t i c s , predominantare:
p e l o i d s ,i n t r a c l a s t s ,
77
;,
Figure 3 5 .
'
... .4*~
..
..
,
&
Outcrop of s i l i c i c l a s t i c s a n d s t o n e , Rock Type 7 .
Note t h e i r o n s t a i n i n g and ironconcretions.Outcrop
occurs i n S e c t i o n E. White c i r c l e i s 2 c m i n d i a m e t e r .
78
dasycladacean algae, and
a few s c a t t e r e d c o a t e d g r a i n s
and foraminifera.
Depositional
Texture:
Wackestone.
Sedimentarystructures:
None.
beddingstyles:
p a r a l l e ll a m i n a e .
However, there are two d i f f e r e n t
1) P a r a l l e lb e d d i n g ,
2) Wavy b e d d i n g ,w i t hl e n t i c u l a r ,
thin ( 2 t o 5' cm thick)'beds(SeeFigure
haveamplitudes
Rock f a b r i c s : I n
2 t o 10 cm t h i c k ,
37).
wavy,
The waves
of 5 t o 8 cm.
the p a r a l l e l bedded u n i t s t h e r e
that resemble fluid-escape structures
are s t r u c t u r e s
(See Figure 36).
They are a l s o similar t o d e s i c c a t i o n f e a t u r e s d e s c r i b e d
by K i n s m a n and Park (1976)on
flat.
a carbonate supratidal
In the wavy bedded u n i t s p o r o s i t y s u g g e s t i v e o f
f e n e s t r a l f a b r i c and nodular anhydrite
molds occurs
locally.
Mineralogy:
S i l i c i c l a s t i c s are predominantlyquartz,with
kaolinite.present.Carbonate
some
is dolomite.
Diagenetic features:
Cements,:
Dolomitemicrospar,localpatchesof
calcite
microspar.
Porosity:
Some p o r o s i t ys u g g e s t i v e
of f e n e s t r a l , and some
suggestiveofnodularanhydritemolds.
amount of i n t e r p a r t i c l e p o r o s i t y . T o t a l
s i t y i s less than 5%.
I n t e r n a l Sediment:
None.
Also, minor
amount of poro-
79
Figure 36.
P o l i s h e ds l a b of s i l i c i c l a s t i c - r i c h p e l o i d w a c k e s t o n e ,
RockType
8. Arrows i n d i c a t ep o s s i b l ef l u i de s c a p e
s t r u c t u r e s . The author i s u n a b l et od e t e r m i n ei ft h e
lamination is of a l g a l mat o r c u r r e n t o r i g i n .
Sample
i s from S e c t i o n C .
(VW 1666/18).
80
Figure 37.
Outcropof wavy bedded u n i t of s i l i c i c l a s t i c - r i c h
peloidwackestone, RockType
8. O r i g i n of wavy bedding
i s unknown. Outcropoccurs
i nS e c t i o n C. Note t h e
hammer f o r s c a l e .
81
Other features:
Some ofthe
areironstained.
laminae i n the parallel bedded units
This rock type was previouslydescribed
as the Mixed sandstone-dolomite f a c i e s i n Neese and Schwartz
(1977).
82
PISOLITEGENESIS
The o r i g i n of t h e p i s o l i t h s and p i s o l i t i c strata has been debated
f o r many y e a r s .
as s u b t i d a l a l g a l m a r i n e
They havebeeninterpreted
(1942), Adam
nodules, i.e. o n c o l i t e s , by Ruedemann (1929),Johnson
and Frenzel (1950),
Newel1 e t a l . (1953), and Kendall (1969).
"
Another i n t e r p r e t a t i o n was proposed by Dunham (1965a, b , 1969,1972)
and independently by Thomas (1965).
They a r g u e d t h a t t h e p i s o l i t h s
were n o t marine a l g a l n o d u l e s , b u t i n - p l a c e e a r l y v a d o s e c o n c r e t i o n s .
Dunham proposed that the p i s o l i t i c f a c i e s was probably a Permian
fossilecaliche.
The most r e c e n t i n t e r p r e t a t i o n was proposed by
EstebanandPray(1975,1976,1977)andEsteban(1976).
They
..
interpreted the. pisoliths to be primary particles deposited
subaqueous-
ly i n a p e r i t i d a l environment.
Dunham (1969) provided excellent criteria and d a t a f o r demons t r a t i n g the in-placenon-algalorigimof
the p i s o l i t e s .
The following
f e a t u r e s were p o i n t e d o u t by Dunham t o s u p p o r t h i s c o n c l u s i o n s :
1) reverse or inverse graded bedding and
a paucity of c u r r e n t t r a c 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) polygonal f i t t i n g of p i s o l i t h s , 3) downward
e l o n g a t i o n so fp i s o l i t h
laminae, 4 ) i n - p l a c e f r a c t u r i n g ,
inclusionsincorporated
i n the u p p e r p a r ' t o f t h e p i s o l i t h s ,
5)perched
6) absence
of a l g a l f i l a m e n t s or cells.
EstebanandPray(1975,1976,1977)andEsteban
(1976) pointed
o u t that fragmented p i s o l i t h s are common as n u c l e i of o t h e r p i s o l i t h s .
They a l s o n o t e d t h a t t h e
matrix between p i s o l i t h s , where p r e s e n t ,
may c o n t a i n p i s o l i t h f r a g m e n t s .
'They concluded t h a t t h e s e f e a t u r e s
83
suggest that some p i s o l i t h fragments were p r e s e n t as, g r a i n s and were
r e d e p o s i t e dw i t hp i s o l i t i cc o a t i n g s .K e n d a l l
gradedbeddingandcrossbedding
(1969) r e p o r t e d normal
i n some o f t h e p i s o l i t e b e d s .
suggested that t h i s i n d i c a t e d t h a t t h e p i s o l i t h s
p l a c e b u t were subaqueously transported
were n o t formed in-
and then deposited.
Esteban and Pray(1975,1976,1977)andEsteban
pointed o u t t h a t p o l y g o n a l f i t t i n g ,
He
(1976) a l s o
downward e l o n g a t i o n s , andperched
i n c l u s i o n s i n t h e p i s o l i t h laminae, occur i n only some of the piso-
laminae of these p i s o l i t h s . E s t e b a n
l i t h s and only i n t h e o u t e r
(1976) n o t e d t h a t , w h i l e i n v e r s e g r a d i n g , p o l y g o n a l f i t t i n g ,
elongation, and perched inclusions indicate
b u t downward elongation do n o t r e q u i r e
and Pray concluded that in-place
s t a g e s of p i s o l i t h growth.
downward
all
an i n - p l a c e o r i g i n ,
a vadoseenvironment.Esteban
growth was evident only
They a r g u e dt h a tt h e
i n the l a t e
'data suggested
..
p i s o l i t h growth by an accretionary process.
The a u t h o r examined t h e major p i s o l i t e b e a r i n g u n i t o f t h e
upper Yates, (informally the Hairpin dolomite),
Canyon f o r f e a t u r e s t h a t
i n Rattlesnake
would a i d i n d e t e r m i n i n g t h e o r i g i n
the pisolite facies. This unit
measured s e c t i o n s C, D, and E inverse graded bedding
are p r e s e n t b u t t h e y a l s o
of
was chosen because p i s o l i t e s t r a t a
are abundant and widespread ( s e e c r o s s s e c t i o n i n appendix).
b u t i s notabundant.Polygonal
In
is present,
f i t t i n g and downward e l o n g a t i o n
are n o t abundant..
The authorobserved
that fragmented p i s o l i t h s are common as n u c l e i o f o t h e r p i s o l i t h s .
Normal graded bedding occurs
:.
i n a few l o c a l i t i e s i n s e c t i o n s C, D,
a4
and E.
Cross-bedding was notobserved, i n any l o c a l i t y .
vations of oriented
From obser-
hand samples p o l y g o n a l f i t t i n g and downward
elongation, where present, occur.
i n the outer laminae
However, i t is a l s o w o r t h n o t i n g ,
as had been noted
of t h e p i s o l i t h s .
by Esteban and
that elongations i n directionsotherthan
Pray(1976,1977)
were also observed by t h e a u t h o r i n R a t t l e s n a k e
Dunham (1969,1972)hadconcluded
Esteban(1976)noted
Canyon.
that the pisoliths
formed i n the vadose diagenetic environment
downward
were
i n caliche s o i l s .
that the reported features of
the p i s o l i t e
beds i n the Permian strata had l i t t l e resemblance to the macroscopic
features of caliche soil profiles.
of
features
macroscopic
,
Esteban (1976) d e s c r i b e d t h e
..,
..
caliche;
'I.'. .a v e r t i c a l l y zoned, subhorizontal carbonate
deposit, normally developed with three
main rock
types: 1) massive .chalky, 2)nodular-crumbly,and
3 ) . l a m i n a t e d a n d / o r p i s o l i t i c compact c r s t or caprock.
The p o s i t i o n anddevelopmentof
these rock types i n t h e
vertical s e q u e n c e ( p r o f i l e ) a n d l a t e r a l l y
is h i g h l y
is that
v a r i a b l e . The o n l y r a t h e r c o n s i s t e n t r e l a t i o n
the massive-chalkyrockgrades
downward i n t o t h e o r i g i n a l
rock or sediment through a t r a n s i t i o n . z o n e , . b o t h w i t h
strong evidence for in-place alteration and replacement
of the o r i g i n a l r o c k or sediment.. .I1
The author did not find
any l o c a l i t i e s i n R a t t l e s n a k e
Canyon where
these macroscopic features of caliche occur.
Esteban (1976) also noted that t h e r e p o r t e d p e t r o g r a p h i c
f e a t u r e s of the C a p i t a n p i s o l i t h s ' d i f f e r g r e a t l y
fromthoseof
v a d o s ep i s o l i t h s
i n c a l i c h ep r o f i l e s .
Vadose c a l i c h e p i s o l i t h s ,
wheredeveloped,
are micritic, i n d i s t i n c t l y l a m i n a t e d , a n d r a r e l y
have more than fivelaminae.Capitanpisolithshavedistinctlaminae,
c o m n l y 10 o r more ( f r e q u e n t l y 20 o r more),and
are composed of
. .
.
85
thin micritic layers alternating with
haveghosts
mosaics of microspar that
or b l a d e d c r y s t a l s .
of r a d i a l f i b r o u s
A d i s t i n c t i v e f e a t u r e of caliche i s the abundance of f i n e
grained calcareous
1976).
~
!
material with.a c l o t t e d , p e l o i d t e x t u r e ( E s t e b a n ,
In the C a p i t a n p i s o l i t h s micrite occurs i n only some p i s o l i t e
n u c l e i and laminae.
by cements or sandto
The i n t e r - p i s o l i t h ps o r e s
are usually
occupied
s i l t s i z e carbonatematrix material.
(1969) notedtheresemblance
Dunham
of t h e C a p i t a n p i s o l i t h s w i t h c a v e
p e a r l s formed i n a vadoseenvironment.Esteban(1976)reported,
however, that Donahue (1965, 1969)and
had demonstrated that cave- pearls
From f i e l d s t u d i e s , E s t e b a n
Ullastre and Masriera (1973)
grow subaqueously.
ra-
and Pray(1975,1976,and1977)
ported finding
two major, end. member types of p i s o l i t i c s t r a t a ,
"in-place"and
"clastic".
The c h a r a c t e r i s t i c s o fi n - p l a c ep i s o l i t i c
strata are: 1) well s o r t e d , w i t h i n v e r s e g r a d i n g ,
2) l i t t l e or no
matrix, 3) absence of obvious c l a s t i c t e x t u r e s , 4 ) p i s o l i t h s are
smooth, s p h e r o i d a lw i t h
small n u c l e i .
The . c h a r a c t e r i s t i c s of
c l a s t i c p i s o l i t i c strata are: 1) good t o poor s o r t i n g , l o c a l l y
showing clastic t e x t u r e s , 2) no inversegrading,
n i t e matrix, 4 ) broken andabraded
Figures 38and
39).Observations
mite in Rattlesnake
3) abundant calcare-
p i s o l i t h s are p r e s e n t .
by t h ea u t h o r
(See
in t h eH a i r p i n Dolo-
Canyon i n s e c t i o n s C, D, and E i n d i c a t e t h a t
t h e two end member t y p e s o f p i s o l i t i c
strata do occur.
Clastic
p i s o l i t e beds are more a b u n d a n t t h a n i n - p l a c e p i s o l i t i c b e d s .
Esteban and Pray(1975,1976,1977)argued
thatthein-place
86
Figure 38.
Outcrop of i n - p l a c ep i s o l i t e s showing reverse graded
bedding.Outcropoccurs
i nS e c t i o n E. White c i r c l e
i s 2 cm i n diameter.
87
Figure 39.
P o l i s h e ds l a b of c l a s t i c p i s o l i t e s . Note t h ei r r e g u l a r
shape of these pisoliths and the broken pisoliths that
are n u c l e i . Arrows i n d i c a t eb r o k e np i s o l i t h st h a t
are
n u c l e i . Sample is fromSection D. (VW 1666/19).
88
p i s o l i t h s formedmostly
i n a bed of loose
by isopachousgrowth
p a r t i c l e s a t o r near a subaqueoussediment
interface.
p a r t i c l e s i n these beds were p r e f e r e n t i a l l y e n l a r g e d .
that the o u t e r laminae o f i n - p l a c e p i s o l i t e s
The upper
They noted
may show the polygonal
f i t t i n g , downward elongation, o r perched inclusion described
Dunham (1969,1972).
They concluded t h a tt h e s ev a d o s ef e a t u r e s
occurred only locally
i n t h e last stage of evolution of
the rock.
t h a t the c l a s t i c p i s o l i t h s p r o b a b l y
EstebanandPrayargued
by
formed
both by a c c r e t i o n on f r e e l y moving subaqueous p a r t i c l e s and as eros i o n a lp r o d u c t s
of i n - p l a c ep i s o l i t h s .
They n o r e dt h a t
clastic
p i s o l i t e beds are more abundant than in-place pisolite beds
o v e r l i ei n - p l a c ep i s o l i t eb e d s .
This v e r t i c a l r e l a t i o n s h i p
and many
of c l a s t i c
.
I.
and in-place pisolite beds
was also observed by t h e a u t h o r i n
Rattlesnake Canyon.
Esteban and Pray were the f i r s t t o n o t e t h a t t h e p i s o l i t i c
beds were l a r g e l yl o c a l i z e d
and Pray(1977)
t o t h ei n t e r t e p e ed e p r e s s i o n s .E s t e b a n
documented b e d s o f p i s o l i t e s
the flanks of tepees
which wedged , o u t a g a i n s t
as e v i d e n c e o f t h e s y n d e p o s i t i o n a l o r i g i n
of
p i s o l i t e s , and as an argument,for a subaqueous o r i g i n i n possibly
r e s t r i c t e d water bodies i n i n t e r t e p e e ponds.
The authorobserved
i n numerous l o c a l i t i e s in Rattlesnake Canyon t h e l o c a l i z a t i o n of
p i s o l i t e beds to intertepee depressions.
Donahue (1965,1969)demonstrated
thatthere
ments f o r p r o d u c i n g a c c r e t i o n a r y p a r t i c l e s ,
andcavepearls.
These fourrequirements
were f o u r require-
i.e. o o i d s , p i s o l i t e s ,
are: 1) calciumcarbonate
89
d e p o s i t i o n from a s u p e r s a t u r a t e d s o l u t i o n ,
2) a v a i l a b i l i t y of a
nucleus, 3) a g i t a t i o n of g r a i n s , 4 ) a splashcup.
i n t e r t e p e e d e p r e s s i o n s would have served
cup" f o r the formation
I s u g g e s tt h a tt h e
as a n e x c e l l e n t
of t h e C a p i t a n p i s o l i t e s .
High on the flanks of
some tepees, in-place and c l a s t i c p i s o l i t e
beds are o v e r l a i n by a rocktype,
that EstebanandPray(1975,1976,
1977) termed b o t r y o i d a l p i s o l i t e .
These rockshaveboth
clasts.
c l a s t i c and
(2 t o 10+ cm)
multilaminarboundstonefabrics,containinglarge
irregular pisoliths,
"megasplash
many w i t h m u l t i - p a r t i c l e n u c l e i
and coated intra-
They s u g g e s t e dt h a tf e a t u r e sw i t h i nt h e s er o c k si n d i c a t e d
that they may haveformed
p i s o l i t e so c c u r
a t or near the water surface. Botryoidal
i n several l o c a l i t i e s i n t h e Hairpin Dolomite i n
. .,< .
;
Sections C, D, E, and F.
Summary
The o b j e c t i v e o f t h i s t h e s i s
was n o t a d e t a i l e d s t u d y on t h e
o r i g i n of t h e . p i s o l i t e s . R a t h e r , t h e o b j e c t i v e w i t h r e s p e c t
l i t e genesis, w a s t o e s t a b l i s h t h e f a c i e s
p i s o l i t e beds occur
mosaic of s t r a t a i n which
and t o a t t e m p t t o make observations bearing
the i n t e r p r e t a t i o n s of p i s o l i t e g e n e s i s .
suredsections
to piso-
In my study area, i n mea-
C, D, E, and F t h e H a i r p i n Dolomiteprovided
d a t a on t h e p i s o l i t e b e d s .
The authoragreeswith
proposed by Esteban and Pray(1977)
p r i m a r yo r i g i nf o rt h ep i s o l i t e s .
the b e s t
the i n t e r p r e t a t i o n
t h a t p o s t u l a t e s a syndepositiond.
I i n t e r p r e t the i n - p l a c e p i s o l i t h s
t o have formed subaqueously by isopachousgrowth
p a r t i c l e s i n a ni n t e r p e ed e p r e s s i o n .
on
i n a bed of l o o s e
The intertepee depression
90
served as a megasplashcup
for the formation of the
pisolites.
Those p i s o l i t e s near t h e t o p were p r e f e r e n t i a l l y e n l a r g e d b e c a u s e
a longerduration.
t h e yc o u l db er o l l e d . a b o u tf o r
some i n - p l a c e p i s o l i t e f o r m a t i o n
show p o l y g o n a l f i t t i n g ,
elongations,andperchedinclusions.
r e s u l t e do n l y
Late s t a g e s o f
All of t h e s e l a t e s t a g e f a b r i c s
when a g i t a t i o n of the p i s o l i t h sc e a s e d .
o f agitation could result
became emergent.
The c e s s a t i o n
from a rise i n sea level t h a t would p l a c e
the interpepeedepression.below wave base.
sea level droppedand
could also result if
downard
The c e s s a t i o n o f a g i t a t i o n
the i n t e r t e p e e d e p r e s s i o n
The presence of downward e l o n g a t i o ni n d i c a t e s
t h a t i n t h e l a t e s t a g e s a t least some of the p i s o l i t e beds were
emergent and i n t h e vadose diagnenetic environment.
Esteban and Pray(1977)
postulated that
c l a s t i c p i s o l i t h s were
deposited i n shallower water t h a n . t h e i n - p l a c e p i s o l i t h s .
The
The
brokenandfragmentedpisolithsindicatesincreasedagitation.
author interprets the
clastic p i s o l i t h s t o h a v e
formed by a c c r e t i o n
on loose subaqueous p a r t i c l e s and as erosional products of in-place
pisolites.
Esteban and Pray(1977)proposed
theydescribedprobably
that the botryoidai pisolite
formed a t o r near t h e water s u r f a c e .
I
noted earlier that their b o t r y o i d a l cement, o r my laminated crust
cement, g r e a t l y r e s e m b l e s s u p r a t i d a l s p r a y
P e r s i a n Gulf today.These
zone cements found i n the
cements i n the P e r s i a n Gulf e n c r u s t the
s u r f a c e and cavities within beach rock (Purser
and Loreau,1973).
91
I s u g g e s t that t h e b o t r y o i d a l cements were p o s s i b l y t h e r e s u l t o f
\
spray zone or s p l a s h zone p r e c i p i t a t i o n d u r i n g a time when he crests
ofthetepees
were emergent.
The l a r g e i r r e g u l a r p i s o l i t e s
and
coated intraclasts may have formed i n small depressions on the tepee
f l a n k s .P u r s e r
and Loreau (1973) a l s od e s c r i b e di ns h a l l o wd e p r e s s i o n s
i n the s u p r a t i d a l beachrockzone
of t h e P e r s i a n Gulf l a r g e ( 2 t o 1 O i -
cm) rock clasts, t h a t are c o a t e d w i t h c r u s t s
similar t o those encrust-
i n g the s u r f a c e and c a v i t i e s of the nearby beach rock.
92
DEPOSITIONAL ENVIRONMENTS
Introduction
It is the concensus of g e o l o g i s t s that h a v e s t u d i e d
that the Guadalupian shelf
water.
this area
s t r a t a were deposited i n shallow marine
To achieve a b e t t e r u n d e r s t a n d i n g
of theGuadalupianshelf
strata we should examine t h e v a r i o u s Holocene shallow water carbonate
water carbonate
platforms for possibleanalogs.Holoceneshallow
platforms are composedof
a variety ofenvironments.
n o t e d t h a t i n Holocene sediments there
James (1979)
is a common sequence of
environmentsfromthereeftowardsland.Thissequenceofenviron-
ments is:
1) r e e f , 2) lime sandshoals,
s i d e of the
6) land(SeeFigure
40).
James (1979)
of t h e t i d a l f l a t u n i t f a c i l i t a t e s i n t e r -
also noted that recognition
pretation of
4 ) lagoon, 5) t i d a l f l a t s on the s h e l f -
lime sand shoals,
ward s i d eo ft h el a g o o n ,
3) t i d a l f l a t s on t h e lee
the s u r r o u n d i n g l i t h o l o g i e s .
Pray (1977) d i v i d e d t h e
1) s h e l f edge, 2) o u t e r s h e l f ,
5) e v a p o r i t e s h e l f
and inner shelf
Permian s h e l f i n t o
'3) s h e l f crest, 4 ) inner s h e l f ,
(See Figure 5). P r a y ' s o u t e r s h e l f , s h e l f
are subdivisions of the marginal
nized by Dunham (1972).
(1979) d i v i s i o n o f
five regions:
logues.Pray(1977)proposed
mound p r o f i l e recog-
Comperison o f P r a y ' s d i v i s i o n w i t h
Holocene shelves produces
crest,
James'
some i n t e r e s t i n g ana-
t h a t the s h e l f crest w a s t h er e g i o n
the s h e l f t o p o g r a p h i c a l l y h i g h e r t h a n t h e
rest of the s h e l f .
of
He
proposed that the sediments of t h e Permian s h e l f cres't were i n i t i a l l y
deposited i n a shallow subtidal environment.
As sedimentation pro-
93
II
OPEN SHELF
OR
II
.I
LAND
I
Figure 40.
Plan view of a Holocene carbonateplatform showing the
sequence of environments. TakenfromJames
(1979).
94
crest s e d i m e n t s b u i l t up t o t h e p e r i t i d a l
ceeded the shelf
level.
Most of the sediments on the s h e l f crest are p e r i t i d a l w i t h small
I b e l i e v e that examination of t h e
i n t e r b e d so fs u b t i d a ls e d i m e n t s .
profile across Holocene shelves indicates that the tidal flats
the lee s i d e of the carbonate sand shoals
totheshelf
most probably corresponds
It thenfollows
crest of the Permian Reef Complex.
the o u t e r s h e l f
lime s a n d s h o a l s , t h e r e e f
is e q u i v a l e n t t o t h e
and the i n n e r s h e l f
equivalenttotheshelfedge,
on
that
is
is equivalentto
the lagoonal sediments.
James (1979) a l s o . n o t e d t h a t the t r a n s i t i o n from the reef across
the lime s a n d s h o a l s , t i d a l f l a t s ,
abruptsuccession.
and i n t o t h e l a g o o n
would b e an
To determine i f James' (1979)sequenceofenvi-
ronments is an adequate model f o r t h e Permian s h e l f strata a comparison
was made betweenfeaturesofHoloceneenvironments
and f e a t u r e s of
the Permian s h e l f .
"
Outer
-
Shelf
or Carbonate
Sand
Shoals
James (1979)andWilson(1975)havedescribedthe
ofcarbonatesandshoals.
characteristics
They are g e n e r a l l y well s o r t e d , o o l i t i c ,
p e l l e t o i d a l or s k e l e t a l lime sands.Oncolites
may a l s oo c c u r .
Bed-
ding i s planarwithabundantcrosslamination.Earlycementation
characterestic, t h e r e f o r e i n t r a c l a s t s ofcemented
common.
These s h o a l s
is
lime sand are
are m o s t l yd e p o s i t e ds u b t i d a l l y
i n shallow,
2 t o 10 m depth, marine water.
Comparison of these f e a t u r e s w i t h f e a t u r e s
i n d i c a t e that t h e s k e l e t a l g r a i n s t o n e
of the study area
(Rock Type 1) and t h e non-
s k e l e t a l g r a i n s t o n e (Rock Type 2) p r e s e n t i n s e c t i o n s A and B (see
95
c r o s s s e c t i o n i n appendix) were probably deposited
emergent lime sandshoals.
These rocks are well s o r t e d , g r a i n s
rounded, with abundant cross lamination
Oncolites are a l s o p r e s e n t , b u t
of emergence, i.e.
as ' s u b t i d a l non-
and p a r a l l e l l a m i n a t i o n .
are notabundant.
f e n e s t r a lf a b r i c
There i s no evidence
strata
and mud cracks.Carbonate
of 5 t o 15 degrees.
of the outer shelf have basinward dips
well
Neil
Hurley(1978,1979)demonstrated,usinggeopetalfabricmeasurements,
that the primary depositional dip
degrees.Isopachousbladed
1 and 2.
origin.
was basinward a t approximately 8
o r f i b r o u s cement is common i n Rock Types
As noted earlier, t h e s e cements are probably of submarine
Some o ft h e
most b a s i n w a r ds k e l e t a lg r a i n s t o n e sc o n t a i n
fragmentsoforganisms,e.g.Tubiphytes,sponges,bryozoans,and
echinoids, that were p r o b a b l y a b l e t o
In Holocene carbonate
basinwardof
environment.
live' i n t h i s environment.
shelves the carbonate sand shoals occur
a t i d a l f l a t environment and shelfward of a reef
Also thecarbonatesandshoals
approximately lkm.
are r e l a t i v e l y narrow,
Examination of t h ec r o s ss e c t i o n
area ( s e e a p p e n d i x ) i n d i c a t e s t h a t o u t e r s h e l f
1 and 2, occurimmediatelybasinwardof
f a b r i c .I n
i n t h es t u d y
strata, Rock Types
strata w i t h a b u n d a n t f e n e s t r a l
the f i e l d , the authortracedoutcrops
Section A that rapidly grade basinward into shelf
CapitanLimestone.
,
of Rock Type 1 i n
edge rocks of the
The l a t e r a l r e l a t i o n s h i p s of Rock Types 1 and 2
with other rock types also supports the author's concSusion that
outcrops of Rock Types 1 and 2, i n Sections A and B, were deposited
as carbonate sand shoals.
96
Shelf Crest o r T i d a l F l a t
James (1979) d e s c r i b e d t i d a l f l a t s i n d e t a i l ,
"...numerous
environments may exist in'very close proximity, not only perpendicu-
l a r t o the s h o r e l i n e , b u t p a r a l l e l t o
i t as well, s o that i n the
geologic record rapid local lithological variations a.re to be expected,
both vertically
and l a t e r a l l y , r a t h e r t h a n
a. smooth s u c c e s s i o n of
progressivelyshallowerenvironments".Sedimentsofthetidalflats
are generallyrecognized
by t h e p r e s e n c e o f f e n e s t r a l f a b r i c .
In
this d i s c u s s i o n the author w i l l c o n s i d e r t h e s h e l f c r e s t t o i n c l u d e
rocks deposited predominantly
i n a p e r i t i d a l environment.
I interpret the fenestral nonskeletal-skeletal packstonegrainstones (RockType
3 ) , thefenestralnonskeletalpackstone-
grainstones (RockType
4 ) , and the p i s o l i t i c g r a i n s t o n e - p a c k s t o n e s
(Rock.Type 5) t o h a v e b e e n d e p o s i t e d
The abundanceof
c i a t e dw i t h
i n . a p e r i t i d a l environment.
f e n e s t r a l f a b r i c and sheeJ cracks within
these r o c k si n d i c a t e s
and asso-
In an
their p e r i t i d a l n a t u r e .
earlier section the author documented evidence that supports
tidaloriginfor
the Guadalupian tepees.
a peri-
Tepees are alsoabundant
i n strata containing Rock Types 3, 4 , and 5 (See HairpinDolomite,
Sections C, D, E, and F).
A comparison of t h e lateral r e l a t i o n s h i p s o f
Permian s h e l f
crest strata w i t h t h e l a t e r a l r e l a t i o n s h i p s i n Holocene shelves
suggests that the.Permian shelf
crest strata were deposited pre-
dominantly as a t i d a l f l a t i n the lee of carbonate sand shoals.
Basinward, Rock Types 3, 4 , and 5 g r a d e i n t o o u t e r s h e l f
strata
97
containing RockTypes
1 and 2 .
This transition was observed by the
author i n t h e T r i p l e t Dolomite, and the Basal Dolomite between Sections
Shelfward Rock- Types 3 , 4 , and 5 grade into strata
B and A.
ing Rock Type 6 .
This t r a n s i t i o n was observed i n t h e T r i p l e t
between Sections E and F.
Dolomite
3,
The l a t e r a l r e l a t i o n s h i p ofRockTypes
4 , and 5 with outer shelf strata
t i d a l f l a t s on t h e l e e s i d e
of
is analogous.to the relationship
of shoals t o t h e shoals themselves.
As noted e a r l i e r , in the geologic record the tidal
f l a t environ-
ment should show local lithologic variation both vertically
laterally.
contain-
In a l l threecarbonateunits
and
i n Sections C, D, and E l o c a l
.and l a t e r a l l y is evident.
lithologicvariationbothvertically
The
local lithologic variation w a s greatly assisted by the formation of
tepees.
It i s evident that
the formation of tepees many produce a
variety of mini-environments.
Within one intertepeedepressionin-
place p i s o l i t h s could be forming.
depression clastic, pisoliths
,
A t the s&e time i n another
could be forming.
In another depression
fenestral skeletal or mixed nonskeletal-skeletal strata could be
forming.
a t any one particular point in
The author suggests that
time tepees could be developing a t one part of the shelf crest,
fenestral laminated..rocks i n another part,
part of the shelf crest.
and p i s o l i t e s i n another
All of these localities
could b e along
facies strike.
The author envisions the following
formation of t h e s e t i d a l . f l a t s .
sequence of events i n the
The f i r s t event would b e deposition
of a nonskeletal or @xed skeletal-nonskeletal sediment on the lee
side of thecarbonate
sand shoals.
James(1979)
noted that the
98
t i d a l f l a t s form on the lee s i d e o f t h e c a r b o n a t e s a n d s h o a l s a f t e r
or currents had swept sand together to
beach r.idges developed
island.
As sedimentationproceeded
mixed skeletal-nonskeletal sediment
form
the nonskeletalsedimentand/or
would e n t e r the i n t e r t i d a l environ-
ment and s t r a t a w i t h f e n e s t r a l f a b r i c and l o c a l a l g a l l a m i n a t i o n would
develop.
After the development of f e n e s t r a l f a b r i c ,
cracks and tepees
would b e i n i t i a t e d , p o s s i b l y
the formation of s h e e t
by f u r t h e r d e s i c c a t i o n .
P r e c i p i t a t i o n of cements would then produce expansion of.sheet cracks
necessarytoformmaturetepees.
As noted earlier the evidence
supports a.submarine origin.for radial fibrous hemispheroid cements.
me
author suggests that
i f t h e r e was a small rise i n sea l e v e l a t
t h i s time the large p o r e s , i n the cores of tepees
for the precipitation
would b e i d e a l
of cements resembling those present
cavities of Holocene r e e f s .
sites
in the large
As noted earlier t h e r a d i a l f i b r o u s
hemispheroid cements i n s h e e t . c r a c k s g r e a t l y r e s e m b l e r a d i a l f i b r o u s
hemispheroids of a r a g o n i t e found. w i t h i n cavities i n the Holocene deep
reef-wall limestones
1976).
i n B e l i z e , ' B r i t i s h Honduras (Ginsburgand James,
Dunham (1972) n o t e dt h es i m i l a r i t y
cements forming in caverns.
of cement.
of t h i st y p e
of cement t o
He proposed a vadose o r i g i n f o r this type
However, t h i s cement hasbeenfoundinterlaminatedwith
i n t e r n a l s e d i m e n t c o n t a i n i n g marine b i o t a Babock ( 1 9 7 4 ) , Yurewicz
(1976),and
Babcock, Pray, and Yurewici (1977).
cates that the radial fibrous hemispheroids
T h i s evidenceindi-
were probablysubmarine
cements.
This proposed rise i n sea l e v e l would a l s o b e an a p p r o p r i a t e
99
time f o r t h e i n i t i a t i o n
of i n - p l a c e p i s o l i t h
development.
i n sea level could then produce the formation of
fabrics, and a l s ol o c a lt r u n c a t i o n
would possibly form
A drop
clastic p i s o l i t h
of t e p e e s .B o t r y o i d a lp i s o l i t e s
a t a time.when the crests of tepees
were a t or
above the water s u r f a c e .
Esteban and Pray(1977)proposed
events.
the following sequence of
A rise i n sea l e v e l r e s u l t i n g from shelf subsidence
i n i t i a t e developmentofin-place
would
p i s o l i t e s i n intertepee depressions.
As sedimentation proceeded water depth would become shallower and
c l a s t i c p i s o l i t h development would b e i n i t i a t e d .
A t t h e same time
that these events were occurring botryoidal pisolites could be forming
on the flanks of those tepees
Fsteban and Pray
a t o r near t h e water s u r f a c e .
(1977) c a l l f o r a s i n g l e rise i n sea level and
s e d i m e n t a t i o n a c c r e t i n g towards t h e water s u r f a c e ( f i l l l e v e l )
produci,ng s h o a l e r c o n d i t i o n s .
The e f f e c t i v e n e s s of a change i n sea level as a r e s u l t of s h e l f
subsidence i n producing a changefromonesedimenttype
to another
dependent on the amount of sediment within an i n t e r t e p e e d e p r e s s i o n .
For.example, i f one depression
water surface than
is 'filled to a level closer to the
i n another depression,
a drop i n sea l e v e l would
probably i n i t i a t e clastic p i s o l i t e f o r m a t i o n i n t h e h i g h e r one and
might n o t i n i t i a t e i t i n t h e one t h a t is only s l i g h t l y f i l l e d .
her
"
S h e l f o r Lagoon
Wilson (1975) h a s d e s c r i b e d t h e c h a r a c t e r i s t i c s o f s e d i m e n t s
ofrestricted
marine shelflagoons.
.They are c h a r a c t e r i s t i c a l l y
is
100
as t h e dominant
mudstones or wackestones with peloids and/or pellets
graintype.
Thesemudstones
or algal
may belaminated,burrowed,
laminated.Locally,unfossiliferousunlaminated
homogeneous m i c r i t e
or scattered nodular molds of evaporites,
with crystallotopic
gypsum
and a n h y d r i t e , a l s o o c c u r .
I i n t e r p r e t the peloid dolomite
mudstone-wackestone (Rock Type 6)
i n a shallow subtidal lagoon.
to have been deposited
The author
observed i n S e c t i o n F t h i s r o c k t y p e w i t h l o c a l o c c u r r e n c e s
e v a p o r i t e molds,burrows,and
algallaminations.Evidence
of
of sub-
aerial exposure is n o t p r e s e n t
(mud c r a c k s , s h e e t
tepees, .ana renestral f a b r i c .
The low abundance of b i o t a , and t h e
low d i v e r s i t y , p l u s t h e p r e s e n c e o f . e v a p o r i t e
cracks, p e r i t i d a l
molds i n d i c a t e s that
the lagoon w a s p r o b a b l y . r e s t r i c t e d , p r o d u c i n g h y p e r s a l i n e c o n d i t i o n s .
James (1979) p o i n t e d o u t t h a t . o n H o l o c e n e c a r b o n a t e s h e l v e s
lagoonal sediments
onthe
most commonly occur shelfward .of t h e t i d a l f l a t s
lee s i d e o f t h e c a r b o n a t e s a n d - s h o a l s .
.Examination of t h e
cross section o f the study area shows t h a t RockType
ward i n t o Rock Types 3; 4 , and. . 5.
betweenSections
E and F.
The a u t h o ro b s e r v e dt h i st r a n s i t i o n
As described i n t h e p r e c e e d i n g s e c t i o n
Rock,Types 3; 4 , and 5 t o r e p r e s e n t a p e r i t i d a l
the author interprets
f l a t that formedon
6 grades. basin-
the 1 e e . s i d e ofcarbonatesandshoals.
The
l a t e r a l r e l a t i o n s h i p s o b s e r v e d . i n t h e Permian s h e l f strata is analogous to relationships observed on Holocene carbonate shelves.
'&is f u r t h e r s u p p o r t s t h e c o n c l u s i o n t h a t
as a lagoonal sediment shelfward
carbonate sand shoals.
Rock Type 6 was deposited
of t i d a l f l a t s on the lee s i d e of
101
Summary of Carbonate Depositional Environments
The profile across the Guadalupian shelf during carbonate
s i t i o n c o n s i s t e d of a s h e l f e d g e , a n o u t e r s h e l f ,
aninnershelf,
to have been
and an e v a p o r i t e s h e l f .
on the o u t e r s h e l f , s h e l f
depo-
a s h e l f crest,
I i n t e r p r e t my study area
crest, and the basinward
p o r t i o n of the i n n e r s h e l f .
The rocks of the s h e l f edge form-theCapitanMassiveLimestone.
The o u t e r s h e l f r o c k s , l a r g e l y s k e l e t a l g r a i n s t o n e s
and nonskeletalgrainstones
emergent sandshoalsdeposited
1)
(RockType
non-
(Rock Type 2) formed'ascarbonate
The
i n a s u b t i d a l environment.
s h e l f crest rocks, fenestral nonskeletal-skeletal packstone-grainstones
(Rwk Type 3 ) , f e n e s t r a l n o n s k e l e t a l p a c k s t o n e - g r a i n s t o n e s
Type 4 ) , and p i s o l i t i cp a c k s t o n e - g r a i n s t o n e
(RockType
(Rock
5), were the
result of p e r i t i d a l d e p o s i t 0 2 on a " t i d a l f l a t " on t h e lee s i d e of
thecarbonatesandshoals..
Rock Types 3 and 4 formed i n the i n t e r -
t i d a l and s u p r a t i d a l p o r t i o n s o f t h e " t i d a l
flat".
predominantly formed i n t h e i n f r a t i d a l p o r t i o n s
The i n n e r s h e l f r o c k s , p e l o i d d o l o m i t e
RockType
5
of t h e " t i d a l f l a t " .
mudstone-wackestones
(Rock
Type 6 ) were deposited i n a , r e s t r i c t e d p r o b a b l y h y p e r s a l i n e s h a l l o w
s u b t i d a l lagoon.Compartson.of
t h ef a b r i c sw i t h i nt h e s er o c k s
the lateral r e l a t i o n s h i p s o f t h e s e r o c k s t o f a b r i c s
and
and l a t e r a l
r e l a t i o n s h i p s on Holocene carbonate shelves supports these interpretations.
Recently, Babcock (1974), Yurewicz(1976,
1977) Babcock
(1977), Cys gal. (1977), and Hurley(1978,1979)noted
d i f f e r e n c e between Holocene carbonate shelves
st.
a major
and t h e Permian s h e l f
102
in that the Capitan
Limestone w a s d e p o s i t e d i n water below wave
base, 20 t o ' 5 0 m in depth, whereas Holocene shelf edge sediments
( r e e f s ) are deposited i n shallowwaterabove
of t h i s d i f f e r e n c e :
authorscitedthefollowing.asevidence
1) l a c k o f m a j o r b i o t i c z o n a t i o n
mentation within Capitan Limestone,
These
wave base.
and a p p r e c i a b l e s k e l e t a l f r a g -
2)- lack of Capitan-derived
sediment or erosional blocks of the Capitan within basinward shelf
formations, 3) extrapolation of primary depositional basinward dip
from t h e s h e l f c r e s t t o t h e C a p i t a n L i m e s t o n e .
Sandstone Depositional Environment
of t h e sili-
Determination of t h e environment of deposition
c i c l a s t i cs a n d s t o n eu n i t s
is notaneasytask.Outcropsofthe
sandstones are not abundant, and sedimentary structures
are n o t
e a s i l ys e e ni no u t c r o p so r. r o c ks a m p l e s .S e d i m e n t a r ys t r u c t u r e s
are n o te a s i l yr e c o g n i z e d
l a c k ofclays.
due t o t h e e x c e l l e n t s o r t i n g
and t h e
Where recognizable,sedimentarystructures
smallcurrentripples,crosslaminations,
are'
and p a r a l l e l l a m i n a t i o n .
These f e a t u r e s were observed i n t h e upper portions
of beds i n
measured S e c t i o n A and i n o u t c r o p i n Walnut Canyon.
.Sandstones i n t h e s t u d y area occur as two s h e e t s 5 and 8 m
thick.
These two s a n d s t o n e s h e e t s a r e l a t e r a l l y p e r s i s t e n t a l o n g
facies strike over the entire shelf
(NeeseandSchwartz,
1977).
The b a s a l c o n t a c t of t h e s e s a n d s t o n e u n i t s w i t h t h e u n d e r l y i n g
carbonate unit i s sharp and erosional only in the area
c a r b o n a t es h e l fc r e s t .
In t h eo u t e rs h e l ft h e s es a n d s t o n e
of t h e
units
.'
I
103
t h i n and break .up i n t o smaller b e d s t h a t are interbedded with the
In the study area this t r a n s i t i o n
carbonatesandshoalbeds.
C and A (see c r o s s s e c t i o n i n appendix).
occurs between Sections
Further basinward
the sands become calcareous and, grade i n t o t h e
shelfward portions of
the shelf edge rocks.
The l a t e r a l c o n t i n u i t y o f t h e s a n d s t o n e b e d s ,
of the s i l i c i c l a s t i c g r a i n s s u g g e s t s t h a t
andtheuniformity
the s i l i c i c l a s t i c g r a i n s
may have been transported to the carbonate shelf
by eolian processes.
Once they. reached the. s h e l f the question remains:
by e o l i a np r o c e s s e s
or w e r e - t h e yd e p o s i t e di n
Frenzel(1950),andKendall(1969)supported
environment.
Newel1 et a l . (1953), Ball
"
were they deposited
a lagoon?
Adam and
an e o l i a n d e p o s i t i o n a l
&. (1971), Jacka sa.
(1969),andSmith(1974b)supported
a subaqueous depositionalenviron-
ment. i n t e r p r e t a t i o n .
noted that a d h e s i o nr i p p l e s ,
Smith(1974b)
t y p i c a l ofeoliansandsheets,
are a b s e n t , a n d f i n e - g r a i n e d d e t r i t a l
white micas, rare i n eolian environments, are widespread and l o c a l l y
abundant.
posed.
Two subaqueous depositionalenvironmentshavebeen
Balls&.
(1971) proposed a lagoonalenvironment.
and Todd (1969)proposed
pro-
Silver
a coastal plain environment.
Pray(1977)andHurley
(1978) havesuggestedthatthe
ciclastics were deposited a t a time when t h e s h e l f s u b s i d e d ,
ducing a h i g h e r sea l e v e l .
silipro-
I s u g g e s tt h a tt h es h e l fs u b s i d e n c e
may h a v e i n c r e a s e d t h e s l o p e o f t h e s h e l f .
This i n c r e a s e i n s l o p e
may have provided a s e t . t i n g i n which t r a n s p o r t of s i l i c i c l a s t i c s
i n a shallowsubaqueous d e k i t y c u r r e n t may haveoccurred.
Blatt
e t a l . (1972) noted that sandstone beds lacking any lamination,
"
..
104
,I
...are formed either by
very r a p i d . d e p o s i t i o n from suspension o r
by d e p o s i t i o n from very highly concentrated sediment dispersions".
A grainflow
is a typeofsedimentdispersion.
teristics ofgrainflowdeposits
I) thick,ungraded,sharply
are:
bounded beds,generallymassiveinternally;
dish-shaped laminae, oriented
Some of thecharac-
2) presence of f a i n t ,
parallel with bedding (can be inter-
p r e t e d as f l u i d e s c a p e s t r u c t u r e s ) ;
3) s c a r c i t y of s o l e marks;
4) l a c k of t r a c t i o n s t r u c t u r e s ( S t a u f f e r , 1 9 6 7 ) .
Deposition from a very highly concentrated sediment disperion
(grain flow) could explain the absence of lamination and the presence
of f l u i de s c a p es t r u c t u r e si nG u a d a l u p i a n . a g e
traction structures present
i n the sandstone beds occur only
the u p p e rp o r t i o n so ft h es a n d s t o n eu n i t s .
probablyformed
siliciclastics.
These s t r u c t u r e s
on , t h e s h e l f .
Hurley(1978)reportedfindingquartzsiltstonebeds
on the s h e l f w a r d s i d e
thickness of these pinched out beds
acrosstheshelf
in
as sea level.was f a l l i n g , j u s t b e f o r e t h e r e c u r r e n c e
of carbonate deposition
pinchedout
The
which
of a presumed s h e l f crest.
The
( 3 m) and an e s t i m a t e d r e l i e f
crest of 3 m, suggests a water depthof
,
forsandstonedeposition.Therefore,
.
I s u g g e s tt h a tt h e
3 to 6 m
siliciclas-
t i c s were t r a n s p o r t e d i n highly concentrated sediment dispersions
fromwhich
they were d e p o s i t e d i n water depths of
r e s u l t e d from subsidence of
3 to 6 m that
the s h e l f .
The thinning and grading of
the s a n d s t o n e s i n t o
the basinward
p o r t i o n of t h e o u t e r s h e l f , i n d i c a t e s t h a t s a n d s t o n e d e p o s i t i o n
was
105
probably contemporaneous w i t h d e p o s i t i o n of t h e o u t e r s h e l f
s h e l f edge.
3: suggest that the carbonatesandshoals
s h e l f may have served as b a r r i e r s t o d e p o s i t i o n
and
of t h eo u t e r
of sand beds
on the
shelf edge.
The s i l i c i c l a s t i c rich peloid wackestone
(RockType
8) repre-
s e n t s s h o r t intervals of time when n e i t h e r s a n d s t o n e nor carbonate
environments were dominant.
Smith (1974b) notedthepresence
of
sandstone dikes i n some s h e l f e d g e r o c k s , s u g g e s t i n g t h a t l i t h i f i c a t i o n of the sandstones was later t h a n t h a t of the carbonates.
This d i f f e r e n c e i n t h e time of cementation
wavy bedding found
(Rock 'Type 8 ) ,
may h e l p e x p l a i n t h e
i n t h e s i l i c i c l a s t i c rich peloid wackestone
WaVy beddingcouldhaveevolved
a heterogeneous layer
fxom compaction of
composed o f l i t h i f i e d c a r b o n a t e l e n s e s
surrounded by "soft" s i l i c i c l a s t i c rock.
.
.
106
CYCLIC SEDIMENTATION
Introduction
Cyclic strata are p r e s e n t i n most of the carbonate shelves
that h a v e b e e n s t u d i e d
ReefComplex
by g e o l o g i s t s . S h e l f s t r a t a o f t h e
are no exception.
Two formsof
Permian
cyclicstrataare
at a largescale,
p r e s e n ti nt h er o c k so ft h es t u d ya r e a .. F i r s t ,
. t h e r e is i n t e r b e d d i n g of sandstones and predominant carbonate units.
Second, within the carbonate strata there
carbonaterocktypes.Bothofthesetypes
are c y c l e s o f d i f f - w e n t
of c y c l i c strata are
discussed below.
Sandstone-CarbonateCycles
The sandstones on t h e s h e l f h a v e r e c e i v e d
much a t t e n t i o n b u t
t h e r e is l i t t l e agreement a s t o t h e i r d e p o s i t i o n a l e n v i r o n m e n t .
Some of t h e . c h a r a c t e r i s t i c s of these sandstones can be explained
by c y c l i c s e d i m e n t a t i o n .
Each c y c l e c o n s i s t s of a s a n d s t o n e u n i t o v e r l a i n by a carbonate
unit.
The b a s a l c o n t a c t s
l y i n gc a r b o n a t e
I observedofsandstoneunitswith
units are s h a r p and e r o s i o n a l .
under-
In t h e T r i p l e t
Unit a weathered zone, d e s c r i b e d p r e v i o u s l y , formed a t t h e t o p of
the carbonate in the area
and E).
of the s h e l f c r e s t ( s e e S e c t i o n s
C, D,
The c o n t a c t o f t h e s a n d s t o n e w i t h t h e o v e r l y i n g c a r b o n a t e
u n i t is i n other places gradationa1,over approximately
1/2 m.
S i l v e r and Todd (1969) and Meissner (1972) proposedthatthe
c a r b o n a t e u n i t s were deposited a t s t a g e s o f h i g h
sea level, cl.astic
107
units a t s t a g e s of low sea level.
Subaqueous a n d / o r s u b a e r i a l
e r o s i o n of the c a r b o n a t e s o c c u r r e d d u r i n g s h o r t i n t e r v a l s o f
extremely low sea level.
Pray(1977)suggestedexactly
the opposite,
carbonate units were deposited a t stages of low sea l e v e l , c l a s t i c
sea level.
u n i t s a t stagesofhigh
would allow saline lagoon
carbonate production
onto the s h e l f area.
He p o s t u l a t e d t h a t s u b s i d e n c e
waters t o s p i l l o n t o t h e s h e l f
and i n h i b i t
and allow s h a l l o w c u r r e n t s t o t r a n s p o r t s a n d s
My i n t e r p r e t a t i o n ofsandstonedeposition
in
(see s e c t i o n on sandstone
.highly concentrated sediment dispersions
depositionalenvironment)supportsPray'sinterpretation.
Silver and Todd(1969)and
Meissner(1972)suggestedthatthe
sea level change was a r e s u l t ofeustasy
o r epeirogeny.Orogenic
.
:
movements would not be, 'able to produce
areal e x t e n t t h a t
are p r e s e n t .
subsidence could have produced
the uniform cycles
Pray(1977)
of l a r g e
s u g g e s t e dt h a te p i s o d i c
the sandstone-carbonate cycles.
Carbonate Cycles
Cycles w i t h i n t h e c a r b o n a t e
by Smith(1974b)and
strata were previously described
Esteban 'and Pray(1977).Cyclicsedimentation
is b e s t developed i n t h e s t r a t a of t h e s h e l f crest.
Cyclesfoundby
g r a i n s t o n e s (RockType
packstone-grainstones
(RockType
the author consist of the p i s o l i t i c packstone-
5) a l t e r n a t i n g w i t h t h e f e n e s t r a l n o n s k e l e t a l
(RockType
4) or p i s o l i t i c p a c k s t o n e - g r a i n s t o n e s
5) a l t e r n a t i n g w i t h t h e f e n e s t r a l n o n s k e l e t a l - s k e l e t a l
packstone-grainstones
the HairpinDolomite
(Rock Type 3 ) .
These cycles were observed i n
i n S e c t i o n s C, D, E, and F; i n t h e T r i p l e t
108
Dolomite i n Sections D and E; i n t h e Basal Dolomite i n Sections B,
C, D, and E.
These cycles are b e s t seen i n t h e i n t e r t e p e e d e p r e s s i o n s
one d e p r e s s i o n t o a n o t h e r .
and cannotbecorrelatedfrom
c y c l e s are 1 / 2 t o 1 m i n thickness.
These
The contactbetweenthe
p i s o l i t i c u n i t and the o v e r l y i n g u n i t i s commonly gradational over
3 t o 5 cm, a l t h o u g hl o c a l l y
i t canbe
The c o n t a c t
a s h a r pc o n t a c t .
between the p i s o l i t i c u n i t and the u n d e r l y i n g f e n e s t r a l u n i t
s h a r p and probablyerosional.If
(1975,1976,1977)
w e acceptEsteban
interpretationthat
is
and Pray's
the p i s o l i t e s o r i g i n a t e
subaqueously, then the sequence from 'pisolitic packstones-grains tones
i s a shoaling upward
into overlying fenestral packstones-grainstones
sequence as theysuggested.
The natureofcontacts
I haveobserved
between the u n i t s of c. .y c l e s a l s o s u p p o r t s t h i s c o n c l u s i o n .
Esteban and Pray (1977) described cycles within
rocks whichthey
named the"walnutitecycle".
t h ew a l n u t i t ec y c l e
The b a s a l member of
is a f e n e s t r a l p e l o i d p a c k s t o n e
overlain by a bed of in-place pisolites.
the p i s o l i t i c
bed.
The c o n t a c t between t h e
f e n e s t r a l u n i t and t h e o v e r l y i n g i n - p l a c e p i s o l i t i c u n i t
and l o c a l l y - e r o s i o n a l . O v e r l y i n g t h e i n - p l a c e p i s o l i t e
c l a s t i c p i s o l i t e bed.
This is
The contactbetween
i s sharp
bed i s a
the i n i p l a c e p i s o l i t e s
and the c l a s t i c p i s o l i t e beds is g r a d a t i o n a l over 2 t o 5 cm.
clastic p i s o l i t e bedgrades
upward, over 4 t o 6 cm, i n t o t h e b a s a l
member of the nextcycle.Thistype
HairpinDolomite
The
of c y c l e was observed i n t h e
i n Sections C, D, E, and F ; i n the T r i p l e t
Dolomite i n Sections D and E; i n the Basal Dolomite i n Sections B,
C, D, and E.
109
i s b e s t developed i n t h e i n t e r t e p e e
The "walnutite cycle"
i
On the f l a n k so ft e p e e si n - p l a c ep i s o l i t eu n i t s
depressions.
relative t o c l a s t i c p i s o l i t e u n i t s .
poorlydeveloped
are
The " w a l n u t i t e
cycle" w a s i n t e r p r e t e d by Esteban and Pray (1977) as a s h o a l i n g
upward cycle.
first and
The fenestralpeloidpackstonesoccured
these small g r a i n s may have p r o v i d e d t h e n u c l e i f o r
Also, c o i n c i d e n t w i t h t h e f o r m a t i o n o f f e n e s t r a l
i n - p l a c ep i s o l i t e s .
fabric,tepees
would develop that form
the "mega-splash"
cupsneces-
The 'clastic p i s o l i t e s
s a i yf o rf o r m a t i o no fi n - p l a c ep i s o l i t e s .
would then form
the overlying
after t h e i n - p l a c e p i s o l i t e s .
Shelfward from
the p i s o l i t e b e l t c y c l e s w i t h i n t h e p e l o i d
dolomite mudstone-wackestones
(Rock Type 6 ) were observed i n the
B a s a l Dolomite i n S e c t i o n F.
Thesecyclesconsistsofbedsof
algal mat(?) laminated
molds andburrows
mudstones w i t h l o c a l
lenses of evaporite
a l t e r n a t i n g witb t h i n beds of laminoid fenestral
These cycles are n o t w e l l developed and occuroveran
wackestones.
i n t e r v a l of 1/2 t o 1 m.
eachotherover
The two members of eachcyclegradeinto
a vertical thicknessof
5 t o 10 cm.
These cycles
may r e p r e s e n t a shallowing upward c y c l e from a s h a l l o w s u b t i d a l
l a g o o ni n t o
a low i n t e r t i d a l environment.Thistypeofcycle
have resulted
may
from s h i f t i n g of the s h e l f cres; environment and t h e
inner shelf environment.
In my study area a n o t h e r s t y l e o f c y c l i c c a r b o n a t e
occurs.
These cyclesoccur
150 t o 200 m shelfwardfrom
i n anapproximately
strata;
50 m wide b e l t ,
the CapitanLimestone.
This c y c l e
110
was obserired i n t h e Basal Dolomite i n S e c t i o n A.
This c y c l e h a s
2 members, t h e b a s a l member of the c y c l e i s e i t h e r s k e l e t a l g r a i n s t o n e (Rock Type 1 ) or t h e n o n s k e l e t a l g r a i n s t o n e
(Rock Type 2 ) .
The b a s a l member .(1/2 t o 1 m t h i c k ) u s u a l l y c o n t a i n s t r a c t i o n
structures, predominantly parallel lamination although cross
lamina-
This member grades upward, over 1 t o 5 cm, i n t o
t i o no c c u r sl o c a l l y .
the upper member, a f e n e s t r a l n o n s k e l e t a l - s k e l e t a l p a c k s t o n e g r a i n s t o n e (RockType
3) u n i t , 1 t o 2 m t h i c k .
The contactbetween
.the f e n e s t r a l u n i t and the o v e r l y i n g b a s a l member of t h e n e x t c y c l e
is g e n e r a l l y s h a r p .
c o m n and may occur only once
graphicsection.
are n o t
It shouxdbenotedthatthesecycles
o r twice i n 50 m of v e r t i c a l strati-
The a u t h o r i n t e r p r e t s t h i s t o b e
a s h o a l i n g upward
c y c l e from a subaqueom' environment i n t o a n i n t e r t i d a l e n v i r o n m e n t .
T h i s . c y c l e may h a v e . r e s u l t e d f r o m s h i f t i n g of , t h e o u t e r s h e l f
environmentand
the s h e l f crest environment.
SUmmaW
Cyclic sedimentation.on the shelf
crest r e s u l t e d from changes
i n sea l e v e l or lateral s h i f t s of mini-environments along facies
s t r i k e o r episodic subsidence o r a combination of these f a c t o r s .
The p e r i t i d a l environment i n which t h e p i s o l i t e s and tepees formed
canbe
composed of many subenvironments.
s h i f t s ofenvironment
I suggestthatthe
were p o s s i b l y i n i t i a t e d by storms.
occur on most Holocene carbonate platforms and
responsible for the transport
and Garret, 1977).
lateral
Storms
may b e l a r g e l y
of sediment on t h e t i d a l f l a t (Hardie
It h a sa l s ob e e nd e m o n s t r a t e dt h a t
some of t h e
111
morphology of H o l o c e n e , t i d a l flats i s determined by t h e o c c a s i o n a l
storm and n o t by t h e d a i l y t i d e s .
The carbonate cycles .on t h e o u t e r and i n n e r s h e l f c o u l d a l s o
be the result
of l a t e r a l s h i f t s of e n v i r o n m e n t s a l o n g f a c i e s s t r i k e .
However, t h e s e c y c l e s
arise fromchanges
and t h e c y c l e s i n t h e p i s o l i t e b e l t c o u l d
i n sea level.
It is w o r t h n o t i n g t h a t i n
.
'
strata of my s t u d y a r e a c y c l e s
consisting of outer shelf rocks overlain
by s h e l f c r e s t r o c k s i n
are a b s e n t .
. t u r n o v e r l a i n by i n n e r s h e l f r o c k s
The absenceof
this
in sea l e v e l
t y p eo fc y l i cs e d i m e n t a t i o ni n d i c a t e st h a tc h a n g e s
were n o t l a r g e enough t o cause large s h i f t s i n t h e environment.
The author suggests that changes
of 2 m or less.
Cycles a r e p r e s e n t a t t h e t r a n s i t i o n s b e t w e e n
environments; i.e.
outershelf.
i n sea l e v e l were only on t h e o r d e r
shelf crest to inner shelf,
and ' s h e l f c r e s t t o
Cycles are a l s o p r e s e n t w i t h i n t h e s h e l f c r e s t .
S m i t h (197413) andEsteban
and Pray(1977)suggestedthatthese
cycles are better explained
by small 1 / 2 t o 2 m changes i n sea l e v e l .
The a u t h o r a g r e e s w i t h t h i s s u g g e s t i o n .
The sandstonecarbonatecycles
sea level.
Yurewicz(1976,1977)
are due t o l a r g e r changes in
s u g g e s t st h a tt h es h e l fe d g e
sediments were d e p o s i t e d i n d e p t h s g r e a t e r t h a n
ward the sandstones pinch out
Massive Limestone.
strata.
Basin-
and grade into the shelf edge Capitan
Also, e r o s i o n s u r f a c e s a t t h e b a s e
u n i t s are l o c a l i z e d t o t h e s h e l f
shelforoutershelf
15 o r 20 m.
of sandstone
crest, and are n o t p r e s e n t i n i n n e r
This i n d i c a t e s t h a t t h e
rise i n sea
112
level r e s u l t i n g from s h e l f s u b s i d e n c e t h a t i n i t i a t e d s a n d s t o n e
depositiondidnotexposesedimentsoftheshelfedge.
suggeststhatsandstone-carbonatecyclesweretheresult
f l u c t u a t i o n on t h e o r d e r of 5 to 10 m.
The author
of s e a l e v e l
113
VARIATION OF THE SHELF CREST WITH TIME
Introduction
Cyclic sedimentation is onetype
environmentswith
time.
of v a r i a b i l i t y of the shelf
However, examinationofthecrosssection
of the s t u d y area (see a p p e n d i x ) i n d i c a t e s t h a t
three i n f o r m a l u n i t s ,
different during deposition of each of the
and t h e Basal Dolomite.
The Hairpin Dolomite, the Triplet Dolomite,
The t h r e e i n f o r m a l u n i t s d i f f e r
abundanceof
from each other with respect to the
d i f f e r e n t f a b r i c s of t h e s h e l f
t h e shelf crest.
crest and the width of
From o b s e r v a t i o n s i n t h e f i e l d t h e a u t h o r n o t e d
that the width of t h e o u t e r s h e l f
time.
the s h e l f was q u i t e
s t r a t a does not seem t o v a r y with
The s h e l f crest strata appearto
a s h e l f w a r dd i r e c t i o n .
expand i n . w i d t h only i n
This t y p e o f . v a r i a t i o n o f t h e s h e l f
was f i r s t r e p o r t e d by t h e a u t h o r andDouglas
.
strata
Neese in Neese and
Schwartz (1977).
Hairpin Dolomite
The Hairpin Dolomite
i s c h a r a c t e r i z e d by an abundance, bath
v e r t i c a l l y and l a t h r a l l y , ; o ft e p e e sa n dp i s o l i t i cr o c k s .
p i s o l i t e s , i n a s s o c i a t i o n with f e n e s t r a l p a c k s t o n e s
occur from
1 / 4 t o 2 -1/4km i n back of t h e s h e i f e d g e
B, C, D, E, and F).
The author was n o t a b l e t o
enough shelfward to determine
GuadalupeMountains.
and grainstones
(see Sections
trace t h i s u n i t
the l o c a t i o n w h e r e . t h e p i s o l i t e s
tepees are no longer present because
summit p e n e p l a i n s u r f a c e
Tepeesand
the r o c k s i n t e r s e c t e d
far
and
w i , t h the
(King, 1948)formingthetopofthe
It is e v i d e n t t h a t ' t h e p e r i t i d a l
shelf crest
.
114
environment'was well developed and wide during deposition
The l a t e r a l t r a n s i t i o n from the s h e l f crest
HairpinDolomite.
strata t o r o c k s of t h e s h e l f edge occurs between Section
the HairpinDolomite.
B and A i n
a
This t r a n s i t i o n is rapid,occurringover
d i s t a n c e less t h a n 1 / 4 km.
deposition of
of t h e
It i s s,uggestedthatsubsidenceduring
the HairpinDolomite
e n a b l e dt h ep e r i t i d a ls h e l f
was slow.
The slowsubsidence
crest t o become extremelywide.
The
of time during
slow subsidence would a l s o a l l o w f o r l o n g p e r i o d s
which peritidal diagenetic processes could produce the abundant
tepees and s h e e t c r a c k s .
T r i p l e t Dolomite
The T r i p l e t Dolomite i s c h a r a c t e r i z e d by a paucity of tepees
and p i s o l i t e s (see c r o s s s e c t i o n
i n appendix).
However, f e n e s t r a l
f a b r i c and thin sheet cracks are abundant.Examination
graphicSections
C, D, and E (see appendix)indicatesthattepees
i n a shelfward
in t h e T r i p l e t Dolomite appear higher .in the section
direction.
Also, i n S e c t i o n B a 2 m t h i c k bedof
skeletalgrainstones
T r i p l e t Dolomite.
of strati-
(RockType
o u t e rs h e l f
2) i s p r e s e n t a t t h e t o p
This i n d i c a t e s a s h e l f w a r dt r a n s i t i o n
s h e l f and s h e l f crest environments during deposition
non-
of t h e
of t h eo u t e r
of t h e T r i p l e t
Dolomite.
I suggest that subsidence during deposition
of t h e T r i p l e t
Dolomite was r a p i d and t h a t c a r b o n a t e s e d i m e n t a t i o n was b a r e l y
a b l e t o keep up with i t .
Examination of t h e c r o s s s e c t i o n i n d i c a t e s
that s h e l f crest strata, Rock Types 3, 4 , and 5 i n Sections C, D,
and E occurred i n a b e l t approximately 1 1 / 2 km wide.,
The paucity
115
oftepees
' i s possiblydueto
the suggestedrapidsubsidence.
Rapid
subsidence could shorten considerably the duration sediment spent
i n t h e p e r i t i d a l d i a g e n e t i c environment.
B a s a l Dolomite
In comparison with.the Hairpin Dolomite and the Triplet Dolomite,
the
Basal Dolomite has characteristics t h a t are somewhere i n between.
Tepeesand
p i s o l i t e s are p r e s e n t and abundant (see Sections B, C, D,
and E) but they
Dolomite.
are n o t as. abundant and widespread
as i n t h e H a i r p i n
In previous work, (Neese and Schwartz, 1977) i t w a s
noted that s k e l e t a l g r a i n s are more comon i n the Basal Dolomite,
than i n e i t h e r the T r i p l e t Dolomite o r the Hairpin Dolomite.
Examination of the c r o s s s e c t i o n (see appendix), show t h a t t h e
d i s t r i b u t i o n ofshelf
crest strata, Rock Types 3 , 4 , and 5, i n d i c a t e s
that the s h e l f crest f o r t h e Basal Dolomite was wider than that
of the T r i p l e t Dolomite but narrower than that
of t h e H a i r p i n
Dolomite.
I suggest that the subsidence rate during deposition
Basal Dolomite was slow enough to allow abundant formation
of t h e
of tepees
and p i s o l i t i c strata. .However, the subsidence r a t e w a s n o t so slow
as t o a l l o w t h e f o r m a t i o n
It is also worth noting
as l a r g e nor do theyhave
Dolomite.
of t e p e e s t o become extremelywidespread.
that tepees i n t h e Basal Dolomite are n o t
as much r e l i e f as t h o s e i n the Hairpin
The l a r g e number and typeofskeletalfragments
in
this u n i t i n d i c a t e that normal marine conditions were more p r e v a l e n t
rather t h a nh y p e r s a l i n ec o n d i t i o n s .
I s u g g e s tt h a td u r i n g
116
d e p o s i t i o n of i& i s u n i t sea l e v e l was s l i g h t l y h i g h e r a n d allowed
marine water t o c i r c u l a t e o n t o t h e s h e f f
crest " t i d a l f l a t " .
sumonary
The Hairpin Dolomite, Triplet Dolomite,
d i f f e r from each o t h e r with r e s p e c t t o t h e
f a b r i c s of t h e s h e l f
and Basal Dolomite
abundance of d i f f e r e n t
crest andthe.widthoftheshelf
author has s u g g e s t e d t h a t
crest.
The
these d i f f e r e n c e s are p o s s i b l y ' r e l a t e d t o
d i f f e r e n t rates of subsidence.
rate of subsidence would enable a l a r g e amount
A very slow
accrete o n . t h e p e r i t i d a l s h e l f
ofsedimentto
rate of subsidence
and become abundant.
cantly the intervals of
'
A veryslow
would also produce long intervals of time during
which p e r i t i d a l d i a g e n e t i c p r o c e s s e s ,
couldoccur
crest.
tepee and sheet crack formation,
A f a s t rate would s h o r t e n s i g n i f i -
time t h a t sediment would b e a f f e c t e d by
p e r i t i d a ld i a g e n e t i cp r o c e s s e s .
There is a n o t h e r p o s s i b l e e x p l a n a t i o n .
crosssection(see.appendix)
.. Examination of the
shows t h a t s a n d s t o n e u n i t s
were
depositedbetween.deposition of each of t h e s e three carbonate
units.
The a f f e c t s of the sandstonedeposition
,
on t h e morphology
of the shelf could have produced the differences between these three
units.
order of
It hasbeendemonstrated
that d i f f e r e n c e s i n relief on the
1 / 2 t o 1 m can produce s i g n i f i c a n t changes i n d e p o s i t i o n a l
environments.
,,
'
117
CONCLUSIONS
1. I h e carbonateshelf
shelf edge
strata were deposited in bands p a r a l l e l t o
the
on a marginal mound p r o f i l e (Dunham, 1972)whichcan
In a s h e l f w a r d d i r e c t i o n t h e s e
besubdividedintofivefacies.
f a c i e s are: 1) shelfedge,
2) o u t e r s h e l f ,
3) s h e l f crest,
4 ) inner s h e l f , and 5) evapori.teshelf(Pray,,1977).
study area were deposited i n the o u t e r s h e l f , s h e l f
inner s h e l f .
Rocks of my
crest, and
The CapitanLimestone was deposited on t h e s h e l f
edge.
2.
E i g h t majorrocktypesof
the s h e l f s t r a t a of my study area are:
1).s k e l e t a l g r a i n s t o n e , . 2) nonskeletal grainstone,
nonskeletal-skeletalpackstone-grainstone,
3) f e n e s t r a l
4 ) f e n e s t r a l non-
5) p i s o l i t i c p a c k s t o n e - g r a i n s t o n e ,
skeletalpackstone-grainstone,
6) p e l o i d mudstone-wackestone,7)
-siliciclastic sandstone, and
8) siliciclastic-rich peloid wackestone.
The o u t e r s h e l f
strata are composed of Rock Types 1 and 2.
The s h e l f crest strata are composed of Rock Types 3 , 4 , and 5.
The i n n e r s h e l f
strata are composed of Rock Type 6.
The author
i n t e r p r e t s the outer s h e l f ' s t r a t a t o h a v e b e e n d e p o s i t e d i n
s u b t i d a l non-emergent carbonatesandshoalenvironment.
a
The
s h e l f crest strata were t h e r e s u l t of p e r i t i d a l d e p o s i t i o n on
a "tidal flat"
The i n n e r s h e l f
on the lee s i d e of the carbonate sand shoals.
strata were d e p o s i t e d i n a r e s t r i c t e d , p r o b a b l y
hypersaline,shallowlagoon.
This sequence is a n a l o g o u st ot h a t
proposed by James (1979) f o r Holocenecarbonate
shelves.
118
3.
Carbonaterocksof
the inner s h e l f , the s h e l f crest, and the most
are dolomites.
s h e l f w a r do u t e rs h e l f
limestones .of t h e o u t e r s h e l f
These rocksgradeinto
and the shelf edge.Dolomitization
is i n t e r p r e t e d t o h a v e b e e n e o g e n e t i c .
4.
The presence of e v a p o r i t e s i n the study area is i n d i c a t e d by
c r y s t a l l o t o p i c . a n dn o d u l a r
The
gypsum and a n h y d r i t e molds.
within
author interprets the evaporites to have been precipitated
the sediments from hypersaline brines forming
i n a restricted
and low
lagoon, probably within shallow subtidal, intertidal,
supratidal sediments
5.
.. Bedded e v a p o r i t e s
are n o t p r e s e n t
The two s a n d s t o n e u n i t s i n the Trip1et.uni.t
are continuous over
most of. the s t u d y area t o w i t h i n 200 m of the Capitan Limestone,
the s h e l f edge carbonates.
where they t h i n and grade abruptly into
The a u t h o r s u g g e s t s t h a t t h e s i l i c i c l a s t i c s
highly co'ncentrated sediment dispersions from
were t r a n s p o r t e d i n
which they
were
deposited i n water depths of 3 t o 6 m.
6. The core of
most tepees is composed of fenestral laminated rocks
(Rock Types 3 and 4 ) and s h e e t c r a c k s f i l l e d
internal sediment.: -Most tepees, and
i n s h e l f crest strata.
a l l large tepees occur only
Sediments i n intertepee depressions
generally wedge o u ta g a i n s tt h ef l a n k so ft e p e e s .
and e r o s i o n a l t r u n c a t i o n o f t e p e e s i n d i c a t e s
was syndepositional.
phase process,
w i t h cement and
This f e a t u r e
that tepee formation
Tepee formation may b e t h e r e s u l t
an e a r l y p h a s e . o f d e s i c c a t i o n c o n t r a c t i o n
l a t e r phase of expansion from crystallization
and a
of carbonate cements,
a l t h o u g h t h e mechanics of each process are.not completely
I.
of a two
. ... <
119
understood.
7.
(1975, 1976, ,
The author'sobservationssupportsEstebanandPray's
are i n t e r p r e t e d
1977) i n t e r p r e t a t i o n of p i s o l i t e g e n e s i s . P i s o l i t h s
a peritidal
to be primary particles deposited subaqueously in
environment.
Two end member t y p e s o f p i s o l i t i c
and "clastic".
observed,"in-place"
s t r a t a were
Clastic p i s o l i t i c strata
are more abundant than in-place strata and commonly o v e r l i e
P i s o l i t i c beds are l a r g e l y l o c a l i z e d
strata.
i n - p l a c ep i s o l i t i c
i n the intertepee depressions.
served as "mega-splash''
The i n t e r t e p e ed e p r e s s i o n s
cups f o r p i s o l i t e f o r m a t i o n .
Botryoidal pisolites
formed on t h e f l a n k s of emergent tepees.
The b o t r y o i d a l c o a t i n g cements were p r o b a b l y p r e c i p i t a t e d i n a
supratidal spray
8.
zone.
Carbonate grain size
and s k e l e t a l g r a i n abundance decreases
shelfwarddirection.Nonskeletalcarbonategrains
abundant grains
9.
in a
are the most
i n the s h e l f strata.
E i g h t types of p o r o s i t y are p r e s e n ti nt h ec a r b o n a t er o c k s .
are:
They
1) f e n e s t r a l , 2) i n t e r p a r t i c l e , 3) moldic, 4 ) burrow,
5) i n t r a p a r t i c l e , 6) vug, 7y s h e e t crack, and 8) f r a c t u r e .
The
fenestral p o r o s i t y and i n t e r p a r t i c l e p o r o s i t y are p r e s e n t i n
s i g n i f i c a n t amountsand
be ofeconomic
are probably the only types of pores to
significance in petroleum reservoir rocks.
10. Four cement types occur within
cracks).
These fourtypes
former pores (other than sheet
are:
1) isopachousbladedtofibrous,
2) m i c r o c r y s t a l l i n e , 3) microspar,and
these cementsprobablyformed
4 ) equantspar.
Each of
i n more than.oneenvironment.
The
120
. .
author interprets the ispachous, microcrystalline,
I
.
and microspar
. cements t o have been primary and eogenetic, probably precipitated
out of marine t o hypersaline water.
l a t e r and interpreted as a fresh
The equantspar
cement is
water cement.
11. Four cement types. previously recognized
by Dunham (1972),
withinthelargesheetcracksin.tepeecores.
occur
These four types are:
1) radial fibrous hemispheroids, 2) mammillary fibrous crusts,
3) laminated crusts, and 4 ) sparry equant calcite.
interprets the- radial fibrous
fibrous crusts to
hemispheroids and the mammillary
have been precipitated early in a
marine tohypersaline
The author
environment.
subaqueous
The laminated crusts are
interpreted t o have been p r e c i p i t a t e d i n a supratidal splash
environment.
zone
The sparry equant c a l c i t e w a s p r e c i p i t a t e d l a t e
i n a fresh water phreatic
environment.
12. Internal sediment is most commonon
associated with fenestral
the shelf crest
laminated rocks
and p i s o l i t i c rocks (Rock mpe 5).
..
sedimentoccurs withinsheetcracks.
(RockTypes
and is
3 and 4 )
Three types of internal
These three types are:
1) red iron stained dolomite pellets, 2) dolomite p e l l e t s i l t ,
and 3) microcrystalline dolomite.
All three types canoccur
interlaminated within one sheet crack.
13. Two forms of cyclic sedimentation are present,
cycles and cycleswithincarbonatestrata.
cycles consist of a sandstone unit grading
carbonateunit.
sandstone-carbonate
The sandstone-carbonate
i n t o an overlying
Sea l e v e l changes on theorder
of 5 to 10 m were
121
probablyresponsibleforthesandstone-carbonatecycles.
interpretationsupportsPray's
My
(1977) t h e o r y t h a t s a n d s t o n e u n i t s
were deposited a t a high sea level s t a g e and carbonate units
at
a low sea level s t a g e .
..
14 Within the s h e l f crest strata c y c l e s c o n s i s t o f
pisolitic rocks, grading into either
RockType
and Pray;1976,1977)consists
fenestral peloid packstones overlain
l a i n by. clastic p i s o l i t e s .
shelftoshelf
3 or 4 , f e n e s t r a l
i n s h e l f crest s t r a t a
laminatedrocks.Anothertypeofcycle
the "walnutite cycle" (Esteban.
Rock'Typ'e 5,
of
by i n - p l a c e p i s o l i t e s ,
In t h e t r a n s i t i o n zonefrom
over-
inner
crest the cycles consist of algal mat(?) laminated
mudstones with local lenses of evaporite
molds andburrows
natingwith,fenestrailaminatedwackestones.
zone from s h e l f crest t o o u t e r s h e l f
alter-
In t h e t r a n s i t i o n . '
the c y c l e s c o n s i s t o f ' s k e l e t a l
or n o n s k e l e t a l g r a i n s t o n e s , .Rock Type 1 or 2, a l t e r n a t i n g with
Rock Type 3 .
fenestrallaminatedpackstone-grainstones'
within the carbonate strata are t h e r e s u l t ofchanges
on t h e o r d e r o f
Cycles
i n sea level
1/2 t o 2 m, a.conclusion reached by Smith (1974b)
and Esteban and Pray(1975,1976,1977).
15. The p o s i t i o n and width of shelf environments
time.
The HairpinDolomite
were v a r i a b l e w i t h
is c h a r a c t e r i z e d by lateral and
v e r t i c a i abundance of tepees and p i s o l i t i c r o c k s .
with the Hairpin Dolomite,
the T r i p l e t Dolomite i s c h a r a c t e r i z e d
by a pauci.tyoftepeesand.pisolites.
.
In comparison
The Basal Dolomite has
. c h a r a c t e r i s t i c s that l i e between .those of the T r i p l e t Dolomite and
122
the H a i r p i n
Dollomite;tepeesandpisolites
i:hough p r e s e n t and
abundant, are n o t as abundant and widespread
as i n the Hairpin
Dolomite.
The a u t h o r i n t e r p r e t s t h e w i d e s p r e a d
abundance of tepees
and p i s o l i t i c rocks i n the Hairpin Dolomite t o h a v e r e s u l t e d
from a slow rate of subsidence during deposition. During deposition
of the T r i p l e t Dolomite the rate of subsidence was h i g h , t h e r e f o r e
l i m i t i n g the duration sediment spent
i n t h e , p e r i t i d a l environment.
The rate of s u b s i d e n c e f o r the Basal Dolomite f a l l s i n befween the
rates f o r t h e H a i r p i n
Dolomiteand
the T r i p l e t Dolomite.
123
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cements i n P l e i s t o c e n e
Bermuda reefrock:
Sed.Geology,
V. 10, p. 179-204.
Seilacher, A . , 1967,Bathymetry
V. 5, p. 413-428.
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Marine Geology,
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Shinn, E. A., 1968, P r a c t i c a l s i g n i f i c a n c e
carbonaterocks:.Jour.Sed.Petrology,
of b i r d s e y e s t r u c t u r e s i n
v. 38,p.
215-223.
Shinn, E. A., 1969,Submarine l i t h i f i c a t i o n ofHoloceneCarbonate
sediments i n t h e Persian Gulf:Sedimentology,
v. 1 2 , p . 109-144.
Silver, B. A., and R. G. Todd, 1969,Permian c y c l i c strata, n o r t h e r n
Midland and Delaware b a s i n s , west- Texas and s o u t h e a s t e r n New
Mexico:
Assoc.PetroleumGeologistsBull.,
V. 53,p.
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Skinner, J. W., and G. L. Wilde,1955, New f u s u l i n i d s from t h e Permian
of west Texas: Jour. Paleontology, v. 29, p. 927-940.
i n Upper Permian shelf carbonate
Smith, D. B., 1974a, Origin of tepees
rocksofGuadalupeMountains,
New Mexico:
k s o c . Petroleum
63-67.
GeologistsBull., V. 58,p.
A
m
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Smith, D. B., 1974b,Sedimentation of upper Artesia (Guadalupian)
cyclic shelf deposits of northern
GuadalupeMountains, New
Assoc. PetroleumGeologistsBull.,
V. 58,p.
1699Mexico:
1730.
Am.
d e p o s i t s and t h e i r i m p l i c a t i o n s ,
S t a u f f e r , P. H., 1967,Grain-flow
Sante Ynes Mountains, C a l i f o r n i a :J o u r .
Sed. Petrology, v. 37,
p. 487-508.
Steinen, R. P., 1974, Phreatic and vadose diagenetic modification
Pleistocenelimestone:petrographicobservationsfromsubsurface
o f Barbados, West I n d i e s :
Assoc.PetroleumGeologistsBull.,
V. 58, p . 1008-1024.
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Taylor, 3. D. M., and L..V. I l l i n g , 1971, A l t e r a t i o n of recent
a r a g o n i t e t o magnesian calcite cement, Qatar, Persian Gulf,
0. P. Bricker(ed.),Carbonate
Cements: Baltimore,Johns
Hopkins Univ. P r e s s , p. 36-39.
&
Tebutt, G. E., C. D. Conley,and D. W. Boyd, 1965,Lithogenesis of a
distinctive carbonate rock fabric,
.& R. B. Parker (ea.),
C o n t r i b u t i o n st o Geology: Universityof
Wyoming-Laramie, p. 1-13.
Thomas, C. M., 1965,Origin of p i s o l i t e s( a b s . ) :
PetroleumGeologistsBull.,
V. 49, p. 360.
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Toomey, D. F., 1972, The b i o t a of thePennsylvanian(Virgilian)
LeavenworthLimestone,midcontinentregion,
P a r t 3: D i s t r i b u t i o n
o f calcareousforaminifera:
Jour. Paleontology, V. 4 6 , p . 276298.
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'
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Tyrrell, W. W.,
Jr., 1962,.Petrology and s t r a t i g r a p h y of near-reef
Tansill-Lamar strata, '3Guadalupe Mountains, Texas and
New Mexico,
Permian of the Central GuadalupeMountains, Eddy County, New
Mexico--Field t r i p guidebookand geologicaldiscussions:
West
Texas Geol.SOC.Spec.
Pub. 62-48, p. 59-69.
T y r r e l l , W. W., Jr., 1969, Criteria u s e f u l i n i n t e r p r e t i n g e n v i r o n ments of u n l i k e but time-equivalent carbonate units (TansillCapitan-Lamar),Capitanreef
complex, west Texas and New Mexico,
i n G. M. Friedman (ed.), Depositional environments i n carbonate
rocks:SOC.
Econ. PaleontologistsandMineralogistsSpec.
Pub.
14, p. 80-97.
-
Ullastre, J., and A. Masriera, 1973,Morfogenesisde
10s o o l i t e s y
p i s o l i t o sd e las cavernas: Speleon, V . 20, p. 5-61.
Vail, P. R.,
R. M. Mitchum, Jr., and S. Thompson, 111, 1977,Seismic
sea level, P a r t 4 : Global
s t r a t i g r a p h y andglobalchangesof
cycles of relative changesof sea level, & C. E. Payton (ed.),
applications to hydrocarbon exploration:
Seismic stratigraphy
Assoc.PetroleumGeologists,
Memoir 26, p. 83-97.
Am.
-
Wilson, 3. L., 1975,Carbonatefacies
Springer-Verlag,471p.
i ng e o l o g i ch i s t o r y :
Wray, J. L., 1977,Calcareousalgae(Developments
New York, Elsevier, 185 p.
s t r a t i g r a p h y4 ) :
New York,
in paleontology and
of
Yurewicz, D. A . , 1976,Sedimentology,paleoecology,anddiagenesis
the massive f a c i e s o f t h e l o w e r
and middle Capitan Limestone
(Permian),Guadalupe Mountains, New Mexicoand west Texas: Unpub.
Wisconsin-Madison,278
p.
Ph. D. Thesis,Universityof
of the lowerand
Y u r e w i a , D. A . , 1977, Origin of the.massive facies
New
middle Capitan Limestone. (Permian), Guadalupe Momtains,
Mexico and west Texas, & Upper Guadalupian facies, Permian reef
complex,Guadalupe Mountains, New Mexico and west Texas, 1977
Basin S e c t i o n SOC. Econ.
Fieldconferenceguidebook:Permian
PaleontologistsandMineralogists,
Pub. 77-16, p. 45-92.
132
APPENDIX
133
The following article is reprinted without any changes from:
. .
'
M. E. Hileman and S. J. Mazzullo (eds.), Upper Guadalupian facies,
Permian Reef complex, Guadalupe Mountains, New
1977 Field conference guidebook:
Mexicoand west Texas,
Permian Basin Section SOC. Econ.
Paleontologists and Mineralogists, Pub. 77-16, p. 437-450.
134
FACIES MOSAIC OF THE UPPER YATES A N D LOWER TANSILL
FORMATIONS, WALNUT AND RATTLESNAKE CANYONS,
GUADALUPEMOUNTAINS, NEW MEXICO
Douglas A. Neese and Arthur H. Schwartz
University of Wisconsin
Department of Gedogy and Geophysics
Madison,Wisconsin 53706
INTRODUCTION
A stratigraphic interval approximately 150 feet thick centered on the contact between the Yates and Tansill Formations i n the eastern Guadalupe Mountains
wasstudiedby the authon (M.S. theses) during
the summer of 1976. This report
presents preliminary results of the work.
Previousworkby Tyrrell (1969), Dunham (1972), Smith (1974) andothers
has delineated broad regional facies belts. O u r study attempted to determine the
more detailed facies of individual units over a narrow belt (2 miles wide and 7
miles long) parallel and adjacent to the Capitan Front, and to provide a facies
mosaic for better interpretations of the pisolite and associated facies. Our study
focused on the strata orthe grainstone and packstone belts shown by Smith (1974).
Our data results from detailed observations and sampling of well-exposed stratigraphic sections and from walking out correlative units between these sections has
yielded information on the geometry and low1 variability of the strata.
Douglas Neese worked in Walnut Canyon on detailed facies mapping parallel and 1-2 miles behind the Capitan Front. Arthur Schwartz worked in Rattlesnoke Canyon on detailed mapping perpendicular to the Capitan Front. A geologic
map showing locations of measured stratigraphic sections and a cross-section showing major stratigraphic units i s presented in Figure 1.
The upper Yates-Tansill stratigraphic interval was chosen for study because
exposures are excellent and accessible, the contact between the Yates and Tansill
is easily recoanized and severol sandstone units occur that are laterally persistent
and excellent for correlation. Informalnames were applied to units i n the upper
Yates and lower Tansill Formations for ease of reference. The upper Yates cansists of two informal divisions known as the Hairpin Dolomite and the Triplet Unit
to as
in this report. The lower Tansill consists of a unit, here informally referred
the Basal Dolomite.
STRATIGRAPHIC SECTIONS
Stratigraphic sections were plotted i n the field at a scale of 10 feet to the
inch. Samples were taken at lithologic changes, and every 2 to 5 feet where
possible. Approximately 1000 samples were taken during the course of the field
135
NW
BACK SHELF
looit#
I
E
SHELF SHELF SLOPE
VlCTORlO
"_
SE
3
SHY CANYON FM.
(1
2 MILES
0
BONE SPRING LS.
A /
"
-+
/modi/irdfiom ryndr.IY62)
Figure 1 .
BASIN
0
1.6
3 2 KM
- (Top)
Geologic map Rattlesnakeand Walnut Canyonarea
southeastern Guadalupe Mountoim showing location strotigraphic secof
of
of
tions. (Bottom) Cross-sectionshowingmajorstratigraphicunits.
The
dark line of the Yates-Tansill Formation contact shows the location of
this study.
136
work. Many of these samples have been slabbed and polished and approximately
150 thin sections have been made. Microscopic examination of these samples was
made to determine grain types and abundance, sorting and abundance of mud and
other data. The resulting informotion, combined with field data, permittied the
closification of the many rock types ard sequences into maior facies groups. These
facies classifications are summarized below'.
The key stratigraphic sections showing the clossification of their facies are
shown in cross-sections constructed parallel and perpendicular to the shelf edge.
These are shown in Figures 2, 3 and 4.
FACIESCLASSIFICATION
The facies classification adopted herein is based on composition, depositional texture, grain type, and abundance of grains present. TWO sandstone facies
are characterized by abundance of siliclastics (quartz andsome feldspar). Seven
are largely carbonates, of which 6 have grain-supported textures and one is mudsupported. Most carbonate rocks are dolomite, but dolomitization has not altered
details of depositional texture. The grain-supported carbonate facies are:
1. Skeletal-rich limestone
2. Skeletal-rich("restricted")
dolomite
3. Mixed skeletal
non-skeletal dolomite
-
4. Non-skeletal dolomite
5. Pisolith-poor dolomite
6. Pisolith-rich dolomite
The sandstone facies are :
7. Sandstone (siliclastic)
8. Mixed sandstonedolomite
One carbonate facies is mud-supported :
9. Mud-supported dolomite
Grain-Supporfed, Skeletal-Rich Limestone
This faciw is composed,of grainstones and minor mud-lean packstones containing a biota characteristic ofnormalmarine water. Skeletal groins occurring i n
the rocks are largely whole and fragmented bryozauiu, echinoderms, forams, Tubiphytes sp., sponges, gastropods, and calcareous algae (dasycladacean and some
encrusting forms). Micritic non-skeletal grains, mostly peloids andcomposite
grains are common, especially in the finer grained and/or more poorly sorted rocks.
Laminated coatings and micritic envelopes occur on some of the skeietol.and nonskeletal grains. Unlike most rocks of the shelf, rocks of this facies are predomin-
137
FACIES
NW
PERPENDICULAR TO
Z
Figure 2.
- Facies cross-section in Rattlesnake Canyon.
SHELF EDGE,
138
RATTLESNAKE,
CANYON
FEET
R
I
SE
"40
-30
"20
"
"
"
"
"10
"0
-10
-20
-30
-40
-50
-63
-m
-ea
I
. 6 !
i
"90
tm
I
139
Figure 3.
-
Wert-ecat bclcfa croa-aection in Walnut Conyon.
140
FACIES PERPENDICULAR TO SHELF EDGE, WALNUT (!!"ON
R
141
-
antly limestone. These rocks bccur as massive beds 3 5 m i n thickness, and
tacally display law-angle cross-sets 10 30 cm thick. Cross-bed dips are primarily toward the basin (easterly), although shelfward dips (westerly) occur as well.
The grains present in the cross-bedded units tend to be oolitically coated. The
racks of this facies occupy a narrow belt 100-500 m wide immediately shelfward of
the Capitan Limestone. In this belt the shelf sandstones have thinned a d are present as thin (4-14 m) tongues that pinch and swell locally, and cannot be traced
into the Capitan. Racks of this facies were probably deposited in a turbulent subtidol environment.
-
Grain-Supported, Skeletal-Rich ("Restricted")Dolomite
This facies is composed of pockstones and grainstones that contain a low
diversity "restricted" water biota.
Restricted water is usedin this report to indicate thqt conditions of temperature and salinity were variable to the extent that
they limited the development of a high diversity, normal marine biota. Grains
are primarily skeletal, mostly dasycladacean algae, gastropods, fomms, and ostracods. Dasycladacean algae are predaninant, forming at least 80% of the skeletal
grains. NonGkeletal grains are minor, including peloids, coated a d compostte
grains, and intraclasts. Bedding is even and parallel ;beds are &-14 m thick.
Same rocks of this facies also occuras small packets or lenses within rodts of the
mixed skeletal
nan-skeletal facies. Rocks of this facies are present as partial
fillings of inter-tepee depressions. Racks of this facies are most commonly associanon-skeletal facies
ted Qith the mare basinward racks of the mixed skeletal
and with the mare shelfward of the skeletal-rich limestone facies. They probably
nonwere deposited under conditions very similar to those of the mixed skeletal
skeletal facies. They probably represent deposition in relatively shallow water at
places of moderate turbulence when water conditions were favorable far high praductian rates of dasycladacean algae.
-
-
-
.
Grain-Supparid, Mixed Skeletal.
-
Non-Skeletal Dolomite
This facies consists of groinstones primarily, and minor packstones composed
of skeletal and nan-skeletal grains in approximately equal abundance (more than
1/3 of each). Non-skeletal grains include pelaids,
composite grains and coated
grains (up to 5 mm). Skeletal grains are representative of a restricted water biota
and consist mostly of dasycladacean algae, gastropods, foroms, and ostracods.
Bath skeletal and nan-skeletal grains may locally have thin laminated coatings.
Locally, rocks of this facies are burrowed. Fenestral fabric is common and various
shapes of fenestme occur. Probable nodular anhydrite molds (4-1 cm) occur locally.
4
Rocks of this facies commonly occur in even parallel beds to 14 m thick.
They also occur in lenses associated with tepees. The lenses thin aver teepee crests
and thicken between them. Rocksof this facies are mast abundant i n oreas immediately shelfward of rocks belonging to the skeletal-rich limestone facies. Farther
shelfward this facies l o s e s the skeletal components and intertongues with rocks of
142
the groin-supported, non-skeletol facies. These rocks were probably deposited in
o subtidal to intertidal environment in quiet to occasionally turbulent water.
Grain-Supported,Non-SkeletalDolomite
This focies consists primarily of mud-lean packstones and grainstones in
which over 2/3 of the grains are non-skeletol The non-skeletal grains include
peloids, composite grains, coated grains and intraclosts. The skeletol grains present are representative of a restricted water biota. They are largely dosycladocean
algae, gastropods, fomms, and ostracods. Some grains have a thin laminated coating. Most grains are sand to granule size except for larger whole or fragmented
gastropods.Fenestral
fabric occurscommonly. Burrows are present locally. In
the most shelfword localities nodular anhydrite molds (4-1 cm) occur. Bedding i n
these rocks is even and parallel, layers are mostly 3 1 m thick, but thinner beds
occur within inter-tepee depressions. Towards the basin ( to the east), beds of
this facies commonly intertongue with the more shelfword beds of the mixed skeletal
non-skeletal facies. In the more shelfward outcrops they intertongue with dolomite of the mudsupported facies. These rocks were probably deposited i n moderately quiet water of a subtidal to intertidal environment.
.
-
-
Grain-Supported, Pisolith-Poor Dolomite
This focies is composed primarily of packstong and some grainstones and
contains between 10 and 50% pisoliths. Other grains include peloids,composite
groins, introclosts, and a few oncolites. Some skeletal fragments such as dasycladocean algae ond foroms occur but are minor. Most commonly the grains ore paarly
sorted. The pisoliths in this focies are small, mostly of granule size (2-4 mm).
Their nuclei are mostly peloids and some skeletol .fragments. They appear fo be
more micritic than the pisoliths of the pisolite-rich facies. Fenestrol fabric, some
distinct and others obscure, occurs locally.
-
The rocks of this facies may occur in distinct beds, up to 1 14 m thick,
the rock occur i n
especially i n the Tonsill Formation. However, more commonly
thinner units (less than 4 m thick) that are transitional beds between rocks of the
pisolite-rich facies and rocks of the grain-supported, non-skeletal facies. Rocks
of the pisplite-poor facies have wide loteral continuity. In the most shelbard
outcrops these rocks intertongue with rocks of the mud-supported dolomite facies.
Rocks of this facies occur commonly in the uplifted central cores and flanks of tepees. They were probably deposited in subtidal to intertidal environments i n
turbulent to moderately turbulent water of hypersaline quality sufficient to repress
skeletal grain production.
Groin-Supported,Pisolith-RichDolomite
This focies is composed of packstones and grainstones containing more than
50% pisoliths. Other rock types present i n minor abundance as pockets or lenses
ore skeletal grainstones, non-skeletol grainstones, and mixed
skeketal
non-
-
143
skeletal grainstones. In the pisolith-rich rocks, sand to granule size peloids and
composite grains, and fine sand to silt size siliclastics occur in minor abundance.
Pisaliths in this facies range upward to 2 3 cm i n size. Pisolith-rich units ore
almost always associated with tepee structures but the converse is not true. The
pisolitic rocks are morecommon i n the inter-tepee depressions. Bedsof pisolithrich rocks are laterally continuous only within individual depressions. The major
occurrence of this facies is i n the Hairpin Dolomite (informal name)
of the Yates
Formation, where pisolith-rich units as thick as. 14 m occur. We consider the
pisaliths as syndepositional particles, and believe this facies was deposited in a
shallow peritidal environment(EstebonandPray,
1975, 1976).
-
Sandstone Facies
This facies is composed of rocks containing predominantly siliclastic grains
and largely devoid of carbcnate grains. Racks consist of well sorted, subangular,
very fine sand to silt size quartz and some feldspar. The rock is cemented mainly
by dolomite. Iron oxide as stains, concretions (4 10 cm), and crusts is abundant
throughout. In the field the rocks of this facies weather to form a grassy covered
recessive slope that is readily recognized. Most rocks are yellowish-orange on
weathered surfaces and light gray dn fresh surfaces. Bedding surfaces are usually
poorly defined. Basal contacts of units with interbedded carbonates appear sharp
and upper contacts are sharp or gradational. The weathering characteristics of
'the racks makes the upper contact difficult to observe. Distinct primary sedimentary
structures are uncommon. Obscure parallel to wavy lamination is common, and
some small (5-30 an) low-angle cross-sets occur. Rocksof this facies occur in
two sheets (one 5 m, the other 6 m thick) ,both in the Yates Formation in our
study area. They are laterally continuous aver the entire study area until within
100 m of the shelf edge where they pinch aut and/or intertongue with the carbonate
racks of the shelf edge. The racks of this facies were deposited in a subaqueous
environment at the shelf edge, and in a probable subaqueous environment aver the
area studied.
-
Mixed Sandstone
- Dolomite Facies
This facies is composed of sandy dolomite and dolomitic sandstone, with
bath siliclastic and carbonate grains. Grains include silt to very fine sand size
quartz (some feldspar), pisoliths, and peloids. Skeletal fragments occur and increase in abundance towards the shelf edge. These rocks are cemented with dolomite. The rocks of this facies weather slightly recessive.
-
In outcrop the racks of this facies occur i n thin (generally 3 1 m thick)
sheets. They are remarkably persistent latemlly for their thickness and pinch out
as they approach to within 100 m of the shelf edge. Two types of bedding styles
occur : parallel and wovy. Theformerhas even, parallel laminae (approximately
2 mm) and thin (2-10 cm) beds. The laminaihn may be disrupted by fenestral
fabric or possible fluid-escape structures. This iype of unit commonly overlies
pisalith-rich strata associated with tepees. The basal contacts of these units are
144
distinct Dlanar e r a;ion surfaces that truncate teoees in the underlying rock units.
These urhs of dolomitic sandstone grade upwardl into dolomite. The wavy bedded
deposits have lenticular, wavy, thin (2-5 cm) beds, the waves having amplitudes
of 5 8 cm. These beds are underlain and overlain by discontinuous or semicontinuaus packets of soft, earthy weathering, sandy carbonate. Units with wavy bedding
are not os laterally persistent as units with parallel bedding. Fenestral fabric a d
cavities suggestive of nodular anhydrite molds '(4 - 1 cm) occur in both the wavy
and parallel units, but are morecommon in the latter. The racks of this facies were
deposited in a subaqueous environment.
-
Mud-Supported Dolomite
This facies is composed primarily of dolomite mudstone and minor grain-lean
dolomite wockestones. The grains are mostly peloids of medium sand size and skelatal Fragmentsof a highly restricted (hypersaline) water biota (ostracods, calcispheres, gastropods and dosycladacean algae). Evidence of evaporites is abundant
as nodular moldsof anhydrite (4 - 1 cm) or crystallotopic moldsofgypsum or anhydrite.
These rocks occur in outcrop in even, parallel beds ranging in thickness
from 5 to 30 cm. At some localities, these rocks occur in units 10 to 20 cm thick,
consisting of discontinuous, wavy parallel beds 2 5 cm thick, with amplitudes of
5 8 cm. Someof the beds exhibit a crinkly (approximately 1 mm) lamination
that strongly resembles laminated algal mats. Burrows are locolly present in the
thicker beds. The rocks of this facies may be cnsociated with racks of the grainsupported, non-skeletal Facies. They are more commonly found i n thp most shelfward portions of the study area, and suggest deposition from quiet, hypersaline
water.
-
-
CONCLUSIONS
Preliminaly conclusions from this study of the upper Yates and lower Tansill Formation of the marginal mound and outer shelf slope strata i n Walnut and
Rattlesnake Canyons ore :
1: Stratigraphic units (0.5
-
6 m) of the sandstone (siliclastic) and
mixed sandstone (siliclastic-carbonate) Facies persist throughout the
study area with but minor thickness variations. Bedsof these Facies
pinch out abruptly at the shelf edge 100 - 300 m away from the Capitan massive facies. Feworno facies variations are evident i n these
units parallel or perpendicular to the shelf edge ;they ore believ.4 to
be subaqueous deposits.
2. Facies of the carbonate units are laterally persistent parallel to the
shelf edge. Threemajor carbonate units and several subunits (0.5
3 m) have been traced laterally for 10 miles. Perpendicular to the
-
145
shelf edge their facies change rapidlx. Towar$ the shelf,carbonate
rocks became more poorly sorted and Increase In mrcrite content and
evaporitic traces. Shelfward of the marginal mound,grain size diminishes.
'
3. Carbonate units between the two major sandstone units (upper Yots;)
decrease in thickness by one-half over the three mile interval s h e l b
to the Capitan.
4. Abundance and diversity of skeletal grains increases towards the Capitw
as reported by others ;however, this change from normal marine to mare
restricted or hypersaline environments is abrupt in one upper Yates carbonate (the HairpinDolomite) and gradational i n twoothers ( the
Triplet Dolomite and Basal Tansill Dolomite).
5., Facies patterns perpendicular to the shelf edge indicate that the relative width of facies belts was highly variable through time. Moreover,
a t various times same facies belts were absent. The carbonate facies
studied did not simply prograde "in
step" with the Capitan Limesione.
6. Mast tepees are associated with fenestral laminated beds of ;h e mixed
(restricted) skeletal andnon-skeletal facies. Although tepees are
associated with pisolith-rich rocks, the pisaliths are best developed i n
inter-tepee depressions.Pisolith-richcarbonatesandabundant,
large
tepees occur across at least two miles of the shelf, exiending to within
less than a half-mile of the shelf edge i n the lower carbonate (Yotes).
They are poorly developed and occur i n a narrow facies belt i n the
uppermost Yates and lowermost Tansill carbonate units.
7
7. Erosional surfaces are common at the upper boundaries of maior carbcnote units and within carbonate units. The most pronounced erosional
surfaces are those where the sandstone facies or mixed skeletal - nonskeletal facies overlietarbonate units with truncated tepees. Some
erosion surfaces show thin zones of alteration, representing possible
sail development. Although erosion surfaces are found close to the
Shelf edge, the alteration zones are localized to areas 1 - 2 miles behind the Capitan Front.
8. The three major carbonate units (Hairpin Dolomite, Triplet Unit and
Basal Dolomite) differ significantly in their shelfward facies progression, indicating that the governing environmental conditions determining carbonate facies, such as water quality, depth and turbulence, were
only partly related to the distance behind the shelf edge. The major
differences of these three carbonate units are summarized below :
Lower carbonate (HairpinDolomite),upper
Yates Formation
146
The pisolith-rich facies dominates this unit, and is associated with
-
nonlarge and abundant tepees. Beds of the mixed skeletal
skeletal facies alternate with beds of the pisolith-rich facies. The
broad belt of pisolith-rich facies and tepees extemls across most of
the study area and persists to within 4 4 mile of the shelfward
edge of the Capitan.
-
Middle Carbonate (Triplet Dolomite), upper
Yates Formation
This unit is the best example of shelfward thinning. The Triplet
Dolomite changes from 1 to 6 meteen in thickness over a distance of
three miles perpendicular to the Cclpitan Limestone. The unit h a s
more admixed siliclastic silt and sand-sizegrains ond micrite than
the other two, and pisolith-rich facies and tepees are minor.
Upper Carbonate (Basal Dolomite),lowerTansillFormation
-
Mixed skeletal
non-skeletal facies persist in this unit through
much of the study area, suggesting a deeper shelfward penetration
of more open marine water than for the other two units. Overlying
pisolith-rich units are in a basinword prograding, shoaling upward
sequence that terminates upward at an erosion surface overlain by
sandstone.
ACKNOWLEDGMENTS
Partial support for this work has been provided by the New Mexico Bureau
of Mines and Mineral Resources and the Wisconsin Alumni Research Foundation.
This support, the cooperation of the Carlsbad Caverns National Park personnel and
the assistance of Mateu Esteban and of Llyod Pray, who is supervising this ihesis
work, is sincerely appreciated.
1 47
REFERENCES
Dunham, R. J., 1972, Capitan.reef, New Mexico
and Texas : facts and questiom
to aid interpretation and group discussion : SOC. Econ. Paleontologists and
Mineralogists, Permian Basin Section Publ. 72-14, variously paged.
Hayes, P. T., 1957, Geology of Carlsbad Caverns East Quadrangle, New Mexico :
U. S. Geal. Survey Quad. Mop GQ 98.
and R. L. Kaagle, 1958, Geology of Carlsbad Caverns West Quadrangle, New Mexico Texas : U. s. Geol. Survey Quad. MapCG 112.
-
Smith, D. B., 1974, Sedimentation of Upper Artesia (Guodalupian) cyclic shelf
deposits of northern Guadalupa Mountains, New Mexico :Bull. Amer.
Asoc. Petroleum Geologists, V. 58, p. 1699-1730.
Tyrrell, W. W., 1962, Petrology and stmtigmphy of near-reef Tamill-Lamar
strata, in-Guadalupe Mountaim, Texas and New Mexico, Permian of the
Central Guadalupe Mountains, Eddy County, New Mexia, Field Trip
Guidebook a d Geological Discussions : West Texas Geol. SOC., Spec.
Pub. 62-48, p. 59-69.
-
, 1969, Criteria useful in interpreting environments of unlike but timeequivalent carborxrte units (Tamill-Capitan-Lamar), Capitan Reef Complex,
West Texas and New Mexioo, in G. M. Friedman (ed.), Deposifional
Environments in Carbonate ROCK:
SOC. Ewn. Paleontologists and Mineralogists Spec. Pub: 14, p.
80-97.
148
LOCATION 'OF'MEASURED SECTIONS
7
The location of each measured section is given as the location
of
the
contact
between
the
Yates
and
Tansill
Formations
within
Maps GQ 112 and
section. Refer to U. S. Geological Survey Quadrangle
GQ 167.
Also, see
Figure6 in text fora map showing the relative
positions of measured sections.
Section A is 1585 feet
from
the
east
line
1900and
feet
from
the
south
line of Section4 in Township25 South, Range2 4 East. Elevation
approximately 4250 feet.
B is 1850 feet
Section -
from
the
west
line
2110and
feet
from
the
south
line of Section
4 in Township25 South, Range24 East. Elevation
approximately 4300 feet.
Section C is 1160 feet
from
the
west
line2640
andfeet
from
the
south
4 in Township 25 South, Range2 4 East. Elevation
line of Section
approximately 4350 feet.
D is 635 feet
Section -
from
the
west
line1585.and
feet
from
the
north
line of Section
4 in Township25 South, Range.24 East. Elevation
approximately 4450 feet.
Section E is 660 feet
from
the
east
line
1 3 0 and
feet
from
the
north
5 in Township.25 South, Range24 East. Elevation
line of Section
approximately 4500 feet.
F is 1585 feet
Section -
from
the
west
line
2640and
feet
from
the
32 in Township 2 4 South, Range2 4 East. Elevation
line of Section
approximately 4600 feet.
,
south
that
149
.
KEY FOR
.
MEASURED
.
SECTIONS
"
GRAIN TYPES
Q = siliciclastics (95% quartz)
=
peloids
~0
=
intraclists
@ = pisolites .
6
= gastropods
Q
*
=
= dasycladacean
algae
t
i
l =
sponges
crinoids
$ = skeletal,
unidentifiable
A = Tubiphytes sp.
POROSITY
TYPES
B = interparticle
F
= moldic
I = intraparticle
E
=
= fenestral
nodular
evaporitic
moldic crystallotopic
evaporitic
EROSION SURFACE.=
ACCESSORY CURVES
= fabric
presentin all
rock types in that
unit
6
= symbol indicates grain
type to which the
accessory curve applies
I
2
I
I
1
I
t
I
I
= number
in, accessory curves
indicates the rock type
of
that unit in which the
fabric occurs
= indicates a local, or
discontinuous
occurrence
FACIES PERPENDICULAR TO SHELF EDGE, RATTLESNAKE CANYON
LAND
2 1/4
2
I
I
N
I
F
I-
--
I 114
I 14
3/4
0
kilometers
.-
I
”
I
I
314 km
I
I
I
I
c
D
t
C
A
I
”
3
I
? I -
I
7
;
:
-\
/
>
CAPTAIN
MASSIVE LS.
LITHOLOGY
DOLOMITE
ROCK TYPES
LIMESTONE
I
SKELETAL GRAINSTONES
2
NONSKELETAL GRAINSTONES
3
FENESTRAL
NONSKELETAL-SKELETAL
4
FENESTRAL
NONSKELETAL
5
PISOLITIC
DOLOMITE
SANDSTONE
OTHER SYMBOLS
MIXED SANDSTONE CARBONATE
I
GRAINTYPES
* *-_
PACKSTONE-GRAINSTONES
PACKSTONE-GRAINSTONES
3
C
5
4
C
5
CYCLES O F ROCK TYPES 5 $I 3
CYCLES OF ROCK TYPES 4 & 5
- 0
MICRITIC (PELOIDS, COATED GRAINS ETC.)
PACKSTONES-GRAINSTONES
*
i
aJ4
a.a
WATER)
(RESTRICTED
SKELETAL
wl
MARINE)(NORMAL
SKELETAL
PIS0 LlTHS
6 DOLOMITE
PELOID
MUDSTONE-WACKESTONE
7
SANDSTONE (SILICICLASTIC)
8
SILICICLASTIC-RICH PELOID
WACKESTONE
TRACTION
T
-
STRUCTURES (PARALLEL & CROSS LAMINATIONS)
EROSIONAL SURFACE
TEPEE STRUCTURE
E
J
EVAPORITE
MtILDS
Geology by A.H. SCHWARTZ