Geology
of t h e
MOLINO PEAK QUADRANGLE
G1 enn
fi.
Osburn, Dav. i d
M.
P e t t y , and C . E. Chapin
1981
- 1 -
G e o l o g i cq u a d r a n g l e maps f o rt h eS o c o r r o - M a g d a l e n aa r e a ,
SOCOrrO County, New Mexico
S e v e r a lh u n d r e ds q u a r em i l e s
of d e t a i l e d g e o l o g i c mapping
h a v e now been c o m p l e t e ao nt h ev o l c a n i cr o c k so ft h en o r t h e a s t e r n
i n t h eS o c o r r o - M a g d a l e n aa r e a .
D a t i l - M o g o l l o nv o l c a n i cf i e l d
Most of t h i s mappinghas
been a v a i l a b l e s i n c e c o m p l e t i o n a s
New
MexicoBureauofMinesandMineralResourcesopen
filereports
c o n s i s t i n g of i n d i v i d u a l t h e s i s maps a n da c c o m p a n y i n gt e x t s .
Over t h ey e a r s ,h o w e v e r ,t h es t r a t i g r a p h i cn o m e n c l a t u r eh a s
c h a n g e dt ot h ep o i n tt h a tc o m p a r i s o nb e t w e e nt h e s ei n d i v i d u a l
maps is d i f f i c u l t .S e v e r a lp u b l i c a t i o n sa r ec u r r e n t l yb e i n g
p r e p a r e dt oh e l pr e s o l v e
t h i s s t r a t i g r a p h i cc o n f u s i o n .
The f i r s t
o ft h e s e
is S t r a t i g r a p h i c C h a r t 1 w h i c h will p r e s e n t t h e c u r r e n t
i n i t s e n t i r e t ya n cp r o v i d e
a glossary
s t r a t i g r a p h i cn o m e n c l a t u r e
to
and o t h e r c o r r e l a t i o n a i d s t o r e l a t e t h i s n o m e n c l a t u r e
p r e v i o u s l yu s e d
names.
T h i s mzp-sheet s i z ec h a r t
s h o u l d be
a v a i l a b l e by December 1 9 8 1 .
C o n c u r r e n tw i t ht h ep r e p a r a t i o no fS t r a t i g r a p h i cC h a r t
1, t h e
t h e s i s maps a r eb e i n gc o m p i l e d
i n + a i r a n g l ef o r m a t
and p l a c e do n
,open f i l e u n d e rt h eu m b r e l l ao f
ope'n f i l e 1 3 9 . E a c hq u a d r a n g l e
. w i l l be a s s i g n e d a p r e f i x l e t t e r ( s u c h a s 1 3 9 a ) and w i l l be
i n many c a s e s , a s h o r t
a v a i l a b l e s e p a r a t e l y . An e x p l a n a t i o na n d ,
t e x t will b ea v a i l a b l ew i t ht h e
map. Nomenclatureand
map
u n i t s w i l l be s t a n d a r d i z e d . Themapping
s y m b o l sf o rw i d e s p r e a d
w i t h i n t h e s ea r e a s ,w h i l eg e n e r a l l ye x c e l l e n t ,
i s n o t a l l of
u n i f o r mq u a l i t y ,p a r t i c o 1 , a r l y
i n t h e t r e a t m e n t of Q u a t e r n a r y
units.
A d d i t i o n a l l y ,m o s tq u a d r a n g l e sh a v e
unmapped p o r t i o n s ,
u s u a l l y i n a r e a s of e x t e n s i v e b a s i n - f i l l a l l u v i u m .
and unmapped
I n i t i a l l y t h e maps w i l l b ec o m p i l e da st h e ya r e
a v a i l a b l e ,h o l e s
will be
p o r t i o n s will r e m a i n . A s timebecomes
f i l l e d i n and p r o b l e ma r e a sf i e l dc h e c k e d
and upgraded.
will remainand
it is i n e v i t a b l e
O b v i o u s l ya n ye r r o r si ng e o l o g y
i n r e c o m p i l i n g t h i s much g e o l o g y t h a t d r a f t i n g e r r o r s
w i l l be
made. A s h o r tn o t ed e s c r i b i n gt h e
known p r o b l e ma r e a sa n dt h e
amountofcheckingthathasbeendone
w i l l b ei n c l u d e d w i t h e a c h
q u a d r a n g l e . W e a s k you t h e u s e r s of t h e s e maps t on o t i f y us of
a n yp r o b l e ma r e a st h a t
y o um i g h tf i n d .P l e a s es e n d
us a n o t e a s
t ot h ee x a c tl o c a t i o n
and n a t u r e of t h ep r o b l e m sa n d
we will make
e v e r ye f f o r tt of i e l dc h e c k
and c o r r e c t them.
I
Thankyou
C.
f o ry o u rh e l p .
E. C h a p i n
Osburn
ti. R.
INTRODUCTION
11 y e a r s a v e r y l a r g e d a t a b a s e
of d e t a i l e d
D u r i n gt h ep a s t
g e o l o g i c m a p p i n gh a sb e e na c c u m u l a t e df o rt h en o r t h e a s t e r np a r t
oftheDatil-Mogollonvolcanicfield
-- theSocorro-Magdalena
a r e a . T h i s mapping h a sm a i n l yb e e nd o n eb yg r a d u a t es t u d e n t s
of
t h e New Mexico I n s t i t u t e o f M i n i n g
andTechnologyworking
o n tne
N e w MexicoBureauofMinesand
M i n e r a lR e s o u r c e sM a g d a l e n a
P r o j e c t . The p r o j e c th a s
been s u p e r v i s e d by C . E. C h a p i na n d ,
an2
s i n c e 1 9 7 8 , G . R. Osburn.
Becauseof
i n c o m p l e t ec o v e r a g e
p r o b l e m a t i c s t r a t i g r a p k , y , t h i s mapping h a s n o t p r e v i o u s l y been
compiled and p u b l i s h e d . Mapping
and
s t r a t i g r a p h i c studies have
n i wp r o g r e s s e d to the p o i n t t h a t s e l e c t e d a r e a s
c a n becompiled
The f i r s t quadrangle
a n dr e l e a s e da sg e o l o g i cq u a d r a n g l e
maps.
t o b er e l e a s e d
i s t h e M o l i n oP e a kq u a d r a n g l el o c a t e d
a p p r o x i m a t e l y 1 0 m i l e ss o u t h w e s t of t h e town of S o c o r r o .
I n p r e v i c u s s t u d i e s w i t h i n t h l . s a r e a and t h r o u g h o u t t h e
used f o r many of
Socor;o-MaSc?alfna a r e a , i n f o r m a l naneshavebeen
t h ev o l c a n i c u n i t s .
S e v e r a lp u b l i c a t i o n sa r e
now i n p r e p a r a t i o n
for
e s t a b l i s h i n g a f o r m a l , and h o p e f u l l yl a s t i n g ,n o m e n c l a t u r e
v o l c a n i cr o c k si n
t h i s a r e a . T h i s new nomenclature is used o n
t h i s map s h e e t ' a n d f o r t h a t r e a s o n d i r e c t r e f e r e n c e
t o p r e v 'l ous
s t u d i e s is p r c b l e m a t i c a l .P u b l i c a t i o n s
i n g r e p a r a t i o n c o n s i s t of
a s t r a t i g r a p h i cc h a r td e s i g n e dt oi n t r o d u c e
t h e new n o m e n c l a t u r e
to p r e v i o u s l yu s e dn o m e n c l a t u r e ,a n d
and t o f a c i l i t a t e c o m p a r i s o n
t h e i n i t i a l two c i r c u l a r s d e s c r i b i n o i n d e t a i l t h e
D a t i l Group
i n t h i s a r e a ) and t h e H e l l s Nesa
( f o r m e r l yt h eS p e a r sF o r m a t i o n
T u f f .S t r a t i g r a p h i cC h a r t
#1, S t r a t i g r a p h i cN o m e n c l a t u r ef o r
v o l c a n i c r o c k s of t h eS o c o r r o - M a g d a l e n aa r e a ,D a t i l - M o g o l l o n
v o l c a n i c f i e l d , i s a p r o t o t y p e of a new s e r i e s of New Mexico
BureauofI4ines
and M i n e r a lR e s o u r c e sp u b l i c a t i o n s .S e v e r a l
l o c a t i o nf i g u r e s ,s t r a t i g r a p h i cc o l u m n s
and a g l o s s a r y a r e
t h i s s h e e t which t h e serious r e a d e r of t h i s map will
p r o v i d e do n
f i n di n d i s p e n s i b l e .
PREVIOUS AND PRESENT WORK
- 2 -
L i t t l e p r e v i o u sg e o l o g i c work h a s beendone
i n or n e a r t h e
Molino P e a k q u a d r a n g l e . E a r l i e r mapping by K a l i s h( 1 9 5 3 )a n d
t h e n o r t h w e s t e r n corner o f t h e q u a d r a n g l e
Krewedl(1974)covered
andmapping
by Miesch(1956)
and W i l l a r d( u n p u b . )c o v e r e d
a
n a r r o ws t r i pa l o n gt h ee a s t e r nb o r d e r .
Geologicmappingused
i n c o m p i l i n g t h i s q u a d r a n g l ei n c l u d e s
most of t h e M . S. t h e s i s maps of Osburn(1978)and
P e t t y( 1 9 7 9 )
a n d smallamountsof
t h e M. S . t h e s i s map of R o t h (1980)and
the
I n a d d i t i o n ,t h e
d i s s e r t a t i o n map ofChamberlin(1980)
s o u t h e r nt h i r do f
t h e q u a d r a n g l e was mappedbyOsburnduring
1 9 7 8 and 1 9 7 9 w h i l e employed by t h e N e w MexicoBureau of M i n e s
and Mineral R e s o u r c e s .
These a r e a s ofmapping
r e s p o n s i b i l i t ya r e
shown on f i g . 1 ( P l a t e 2 ) . Mapping i s a v a i l a b l e f o r much o f t h e
s u r r o u n d i n g a r e a s , m a i n l y a s t h e s i s maps o n open f i l e w i t h t h e
N e w Mexico B u r e a u ofMines and M i n e r a l Resources.
An i n d e x t o
a
t h i s mapping .is i n c l u z e d o n S t r a t i g r a p h i c C h a r t 1 s f i g . 2 .
-
ACKNOFiLEDGMENTS
The a u t h o r s a r e i n d e b t e d to many p e o p l e whose e f f o r t s and
t h i s p u b l i c a t i o n . We owe a major
s p o r th a v eg r e a t l yi m p r o v e d
d e b t t o t h e many workers who have e s t a b l i s h e d t h e s t r a t i g r a p h i c
b a s e w h i c k made p o s s i b l e ths mappir:g and i n t e r p r e t a t i o 2 of
s t r s t i g r a p h i cr e l a t i o n s h i p s ir, t h i s vel:\; complex t e r r a i n . T h e s e
e a r l y workers a r e e a s i l y f o r g o t t e n s i n c e
marly of t h e i r
i n t e r p r e t a t i o n s h a v e been changed w i t h . t h e a c q u i s i t i o n of
a d d i t i o n a ld a t a .I n d i v i d u a l
workers and t h e i rs t u d y areas a r e
d e t a i l e d i n OsburnandChapi'n,1981
( N e w Mexico B u r e a u of Mines
and Mineral Resources, S t r a t i g r a p h i c C h a r t 1) We would a l s c l i k e
t o t h a n k Sinokey Pound and t h e ------ ------- C a t t l e company f o r
access to t h e i r p r i v a t e l a n d s an2Tenneco M i n e r a l s f o r p e r n i s s i o n
t o map areas i n w h i c h t h e y own t h e mineral r i g h t s . T h e Xew
Mexico Bu r e a u o fM i n e sa n dM i n e r a lR e s o u r c e sp r o v i d e df i e l d
s u p p o r t f o r t h e s i s s t u d i e s and a d d i t i o n a lm a p p i n g .
.
-
3 -
STRATIGRAPHICUNITS
A l l o ft h er o c k se x p o s e d
i n t h i s q u a d r a n g l ea r ee i t h e r
T e r t i a r y v o l c a n i c rocks o rs e d i m e n t a r y
rocks d e r i v e d from t h e
v o l c a n i cr o c k s .
T h e o l d e s t and most v o l u m i n o u sr o c k sa r e
two
O l i g o c e n ec a u l d r o n - f a c i e sa s h - f l o wt u f f s
and t h e i r r e l a t e d
c a u l d r o n - f i l ls e q u e n c e s .T h e s ea r ec l o s e l yf o l l o w e d
i n time by
two major o u t f l o w - f a c i e s a s h f l o w s
a n db yi n t e r b e d d e dm a f i cl a v a
f l o w s . The l e s sv o l u m i n o u s Mioceneand
P l i o c e n ev o l c a n i cr o c k s
a r e m o s t l y b a s a l t and r h y o l i t e l a v a f l o w s w h i c h a r e i n t e r c a l a t e d
w i t h w i t h b a s i n - f i l l s e d i m e n t of t h e S a n t a FeGroup.
Short
u n i t a r eg i v e ni nt h e
d e s c r i p t i o n s o fe a c hs t r a t i g r a p h i c
e x p i a n a t i o nw i t h t h i s map a n d ,f o rm o s t
u n i t s , a more d e t a i l e d
s t r a t i g r a p h i cd e s c r i p t i o n
is n o t i n c l u d e d i n t h i s t e x t . T h e
r e a d e rs e e k i n g more i n f o r m a t i o n is d i r e c t e d t o S t r a t i g r a p h i c
C h a z t #1, (Osburn and C h a p i n , 1 9 8 1 ) o rt ot h ea p p r o p r i a t e
c i r c u l a rd e s c r i b i n gt h es p e c i f i c
u n i t ( t h e s e t o be r e l e a s e d i n
p a r t s b e g i n n i n g i n 193lj.
Ask-flow t u f fc a c r l d r o n s ,w h i l es t r u c t u r a l
i n n a t u r e ,c a u s e
this
f a c i e s r e l a t i o n s h i p s w h i c hd o m i n a t et h es t r a t i g r a p h yo f
2 s h o w st h er e l a t i o n s h i p
of t h eM o l i n o Peak
a r e a .F i g u r e
q u a d r a n g l e t o t h es u r r o u n d i n gc a u l d r o r ,c o m p l e x
and f i g . 3 ( P l a t e
2 ) i s a g e n e r a l i z e dg e o l o g i c map of t h eq u a d r a n g l e s h o w i n g i n a
of: t h er o c k sr e l s t e dt o
s i m p l i f i e d manner t h er e l a t i o n s h i p s
t h e s e two c a u l d r o n s . T h i s q u a d r a n g l e is e n t i r e l y w i t h i n t h e
l a r g eS o c o r r oc a u l d r o n
which e r u p t e d t h e H e l l s
Mesa Tuff andwas
u n i t s , t h eo l d e s t
f i l l e d by t h e L u i s LopezFormation.These
r o c k se x p o s e d
i n t h e map a r e a , a r e now r e s t r i c t e d i n e x p o s u r e
b e c a u s e i n t h e not t h e r n two t h i r d so ft h ea r e at h e yh a v eb e e n
downfaultedby
t h e youngerSawmillCanyoncauldron.
The Sawmill
Canyon c a u l d r o ne r u p t e do n e
member o f t h e La J e n c i a T u f f
ar,d was
f i l l e d by t h e S a w m i l l Canyon F o r m a t i o n .
- 4 -
"
FIGLIRE 2 .
L o c a t i o n map showicg t h e r e l a t i o n s h i p ofmajor
v o l c a n i cs t r u c t u r e sa n dt h et r a n s v e r s es h e a rz o n et ot o p o g r a p h i c
and c u l t u r a lf e a t u r e s .B a s e
is reproducedfrom
a NASA S k y l a b
i n f r a r e dp h o t o g r a p h
(GXAO26195GOO).
S o l i d l i n e s mark e x p s e d
c a u l d r o n - w a l ls e g m e n t s ;c a i l l d r o r .m a r g i ni n t e r v a l si n f e r r e d
beneathyounqer
u n i , t s a r ed o t t e d .
The m a r g i n so ft h en o r t h e r n
h a l fo ft h eN a g d a l e n ac a u l d r o n
! 3 b ) a r e well l o c a t e db u t of
p r o b l e m a t i ci n t e r p r e t a t i o n .
' T h i s m a r ~ i nis s h o w , a s a d a s h e d
l i n e . T h e S o c o r r oc a u l d r o n
(1) i s t h e source f o rt h e
Hells Mesa
(2, 3
T u f f , and t h ec o m p o s i t eS a w x i l lC a n y o n - M a g d a l e n ac a u l d r o n s
and 35) a r et h o u g h tt ob et h es o u r c e sf o rt h e
La J e n c i aT u f f .
T h en o r t hh a l fo ft h eM a g d a l e n ac a c l d r o n
( 2bj is a p p a r e n t l y a
s t r u c t u r a l bench w h i c h u n d e r w e n tr e l a t i v e l y
minor c o l l a p s e a f t e r
e r u p t i o n .S o u r c ec a u l d r o n sf o rt h eL e m i t a r
and C h o c l eW e l lT u f f s
a r et h o u g h t
from r e c o n n a i s s a n c e to be i n the n o r t h e r n and c e n t r a l
S a n MateoMountains.The
t r a n s v e r s es h e a rz o n er e p r e s e n t s
a
domainboundarybetween
f i e l d s of t i l t e d f a u l t b l o c k s t h a t h a v e
u n d e r g o n er o t a t i o n
i n o p p o s i t e d i r e c t i o n s ( s e eC h a p i n and o t h e r s ,
1978).
'
.- 5
-
S o c o r r o CaUldKOn
C a u l d r o n f a c i e s H e l l s Mesa T u f f and t h e L u i s LopezFormation
c o m p r i s e t h e S o c o r r o c a u l d r o nr o c k s exposed i n t h i s q u a d r a n g l e .
The H e l l s Mesa T u f f c r o p s o u t s p o r a d i c a l l y a l o n g
Ryan H i l l Canyon
f o ra b o u tt h r e em i l e s .T h e
L u i s LopezFormation
is exposedalong
t h i s same t r e n d and i ns c a t t e r e do u t c r o p se a s t w a r dt ot h ee d g eo f
t h i s map.
O n l yo n et h i c ke x p o s u r eo fH e l l s
Mesa Tuff is p r e s e n t
i n t h i s q u a d r a n g l e( s e c .
7 , T. 5 S., R. 2 W.)
This expsure
in
c o n t a i n s two d i s t i n c t i v ez o n e s w h i c h a r es i m i l a rt oz o n i n g
more e x t e n s i v e o u t c r o p s i n t h e C h u p a d e r aM o u n t a i n sf u r t h e re a s t
( s e ef i g s .
4 & 5)
T h i sc o r r e l a t i o nc o n f i r m st h a tt h ee x t e n s i v e
o u t c r o p s i n t h eC h u p a d e r aM o u n t a i n sa r eX e l l s
Mesa T u f f r a t h e r
t h a nL e m i t a rT u f f
19EO).
a sp r e v i o u s l yh y p o t h e s i z e d( C i r a m b e r l i n ,
is u s u a l l yd a r kr e d
to brcwn,denselywelded,and
Thelowerzone
q u i t e l i t h i c r i c h ( 5 t o 30%). Common l i t h i c f r a g m e n t y p e s
i n c l u d e r h y o l i t i c and a n d e s i t i c l a v a s and s e v e r a lP r e c a m b r i a n
p l u t o n i c and m e t a m o r p h i cl i t h o l o g i e sT
. h i sl o w e zr o n e
is
u n i t which c o n t a i n s
o v e r l a i n by a l i g h t - g r a y ,r o o s e r a t e l yw e l d e d ,
numerous a n g u l a r to p a r t i a l l y f l a t t e n e c ! c l a s t s
Gf Hells Mesa
l i t h o l o g y ,b u t
few o t h e r l i t h i c f r a q n s n t s . T h e c l a s t sa r e
t y p i c a l l yd a r k e rr e dt h a nt h em a t r i x ,b u ti n d i s k i n g u i s h a b l e
been i n t e r p r e t e d( C h a r c b e r l i n r
1980)
o t h e r w i s e . T h i s d e p o s i th a s
a s a " l a g - f a l l "d e p o s i t( W r i g h t
and Walker, 1 9 7 8 ) o fp a r t i a l l y
s o l i d i f i e d c l o t s of
H e l l s Nesa magma w h i c h weredropped
early
f r o mt h ea s h - f l o wc l o u db e c a u s e
of t h e i rg r e a t e rd e n s i t y .
The
m a t e r i a l may h z v e b e e n p a r t i a l l y s o l i d i f i e d H e l l s
Mesa magma
whichaccumulated
i n a v e n to rm a t e r i a ld i s r u p t e d
from a
h y p a b y s s a li n t r u s i v e ,e i t h e ro fw h i c hc o u l dh a v ef o r m e dd u r i n g
a
h i a t u si ne r c p t i o n
andthenbeenfragmented
by c o n t i n u i n g
volcanism.
.
.
'
L u i s LopezFormation
within this
E x p o s u r e so ft h e
q u a d r a n g l e ,e x c e p tf o rt h e
two n o r t h e r n o u t c r o p s i n Ryan H i l l
Canyon, a r e a r e l a t i v e l ys t r a i g h t - f o r w a r dl a y e r e ds e q u e n c e .
They
consist of a l i t h i c - r i c h ,p o o r l yw e l d e d ,c r y s t a l - p o o rt u f f ,
or more a n d e s i t i c l a v a f l o w s
and a t h i c k
o v e r l a i n i n t u r n byone
sequence of r h y o l i t i cl a v a s
which a r eo f t e nu n d e r l a i nb ya n
i n Ryan H i l l Canyon
a s s o c i a t e da s h - f l o wt u f f .
The r h y o l i t el a v a
is d i s c o r d a n t t o t h e
p r o b a b l y r e p r e s e n t s a dome complexwhich
s e c t i o nd e s c r i b e da b o v e .
On a l a r g e rs c a l e ,
t h e L u i s Lopez
F o r m a t i o nv a r i e sl a t e r a l l yi n
a complexmanner.
T h i s complexity
t o g e t h e rw i t hl i m i t e de x p o s u r e sm a k e s
a d e t a i l e d u n d e r s t a n d i n g of
t h i sf o r m a t i o nv i r t u a l l yi m p o s s i b l e .
The b e s te x p o s u r e s
of t h e
L u i s LopezFormationare
i n t h e ChupaderaMountainsandare
d e s c r i b e d i n d e t a i l byChambe'rlin,
1980, Eggleston, i n p r o g r e s s ,
andOsburnand
others, i n preparation.
- 6 -
La J e n c i a T u f f
The upper member ( o u t f l o w )o f
t h e La J e n c i aT u f fc r o p so u t
map.
i n o n l y one a r e a i n t h e e x t r e m e s o u t h e a s t e r n c o r n e r o f t h e
Thelower
member is p r e s e n t i n t h i s o u t c r o pa r e a ,
and i n s e v e r a l
o t h e rs m a l lo u t c r o p sa l o n gt h es o u t h e r ne d g eo ft h eq u a d r a n g l e .
Thelower member h a s s t r o n g l y l i n e a t e d
pumice w h i c h y i e l d
t r a n s p o r td i r e c t i o n ss o u t h
and s o u t h e a s t( r a d i a l l y ? )
away from
t h e S a w m i l l Canyon c a u l d r o n .
S a w m i l l Canyon C a u l d r o n
The c a u l d r o n - f a c i e s La J e n c i a T u f f and t h e S a w m i l l Canyon
F o r m a t i o n c o m p r i s e t h e Sawmill Canyon c a u l d r o n r e l a t e d r o c k s
of
exposed i n t h i s q u a d r a n g l e .L a r g ea n dv e r yt h i c ke x p o s u r e s
c a u l d r o n - f a c i e s La J e n c i a T u f f a r e f o u n d a l o n g
Ryan H i l l Canyon
a l o n gt h ew e s ts i d e
of t h i s q u a d r a n g l e and i n S a w m i l l Canyon j u s t
t o t h ew e s t( s e ef i g .
2 ) . T h e s er o c k sa r et e n t a t i v e l yc o r r e l a t e d
w i t ht h el o w e r
member o f t h e La J e n c i a T u f f b e c a u s e o f t h e
p r e s e n c e of s t r o n g l y l i n e a t e d pumicewhich
is c h a r a c t e r i s t i c of
p a r t s of t h el o w e r member. Both members of t h e La J e n c i aT u f f
c h a r a c t e r i s t i c s and no s t r a i g h t - f c r w a r d
h a v es i r r i l a rp e t r o g r a p h i c
d i s c r i m i n a t i o n method is known.
I n c o n t r a s tt ot h e" d i r t y "
( l i t h i c - r i c h ) cauldron-facies
is r e m a r k a b l y
H e l l s Mesa T u f f , t h e i n t r a - c a u l d r o n
La J e n c i a T u f f
c l e a nt h r o u g h o um
t ost
of i t s e x p o s u r eA
. l t h o u g hf e ws m a l l
l i t h i c - f r a g m e n t sa r ep r e s e n t ,s e v e r a ll a r g e" m e g a - b l o c k s "a r e
p r e s e n t i n t h eS a w m i l l Canyon a r e a ,
and i n b o t hc a n y o n s a t h i n
r h y o l i t el a v ah a sb e e n
mapped w i t h i n t h e Epper p a r t of t h e t u f f .
T h i sl a v a may cccupy t h eb r e a k betweenlowerandupper
members
o r , a l t e r n a t i v e l y , may h a v eb e e ne r u p t e dd u r i n g
a h i a t u si n
e r u p t i o n of t h e lower member.
An a n o m a l o u s l yc r y s t a l - r i c h
(15-35%) zone is p r e s e n t at- t h e t o p of t h ec a u l d r o n - f a c i e s La
J e n c i aT u f f
i n a few p l a c e s( B o w r i n g ,
1 9 8 0 ) ; however, t h i s zone
h a sn o t been mapped s e p a r a t e l y .
T h e c a u l d r o n - f i l l i n g S a w m i l l Canyon F o r m a t i o n ,w h e r e
i t is
exposed i n t h e western t h i r d of t h ec a u l d r o n ,
i s a s e q u e n c eo f
a n d e s i t i c and r h y o l i t i cl a v a s ,s e d i m e n t a r yr o c k sa n da s h - f l o w
t u f fTso. g e t h e r
t h e u n i t s a ra et
l e a s t 8 0 0 m , and p o s s i b l y 1 0 0 0
m i nt h i c k n e s s .
W i t h i n t h e lower two t h i r d s of t h i s s e c t i o n ,
a n d e s i t i cl a v a s whichpredominate
i n t h en o r t hi n t e r f i n g e ri n
a
w i t h r h y o l i t i c l a v a s and t u f f s which a r e more
complexmanner
a b u n d a n t i n t h es o u t h .T h r o u g h o u tm o s t
of t h ea r e a , a f a i r l y
e x t e n s i v e and t h i c k " m o a t - f i l l ' 't u f f ,t h eT u f fo fC a r o n i t a
Canyon
makes up t h e u p p e r t h i r d o f t h e s e c t i o n .
T h e SawmillCanyonFormationpinches
o u t s o u t h w a r da g a i n s t
t h e s o u t h e r nt o p o g r a p h i cw a l lo ft h eS a w m i l l
Canyon c a u l d r o n .
- 7 -
T h i s nor t h - s l o p i n gu n c o n f o r m i t yt r e n d sn o r t h e a s t w a r d
across t h e
s o u t h e r n p a r t of t h i s map a r e a ,b u t
is v e r y i r r e g u l a r i n d e t a i l
due to l a t e r s t r u c t u r a l o f f s e t and o r i g i n a ls c a l l o p i n g .T h e
rocks e x p o s e db e n e a t ht h i su n c o n f o r m i t y
are t h e Hells Mesa T u f f
a n dt h eh e t e r o l i t h i c
L u i s LopezFormation.
A c o n s p i c u o u sn o r t h w a r dt h i c k e n i n g
of t h eS a w m i lC
l anyon
F o r m a t i o no f fo ft h et o p o g r a p h i c
wall can b es e e nb yc o m p a r i n g
thestratigraphicinterval
between t h eL u i sL o p e zF o r m a t i o n
and
sec. 9 , T. 5 S . , R. 2 W. w i t h
t h e o v e r l y i n g lower L e m i t a rT u f fi n
t h e same i n t e r v a lf a r t h e rn o r t ha l o n g
Ryan H i l l Canyon. I n
s e c t i o n 9, t h i si n t e r v a lc o n s i s t so fa b o u t
50 m o f L a J e n c i a
T u f f : whereas, f a r t h e r n o r t h a b o u t
800 m o fS a w m i l l Canyon
no
F o r m a t i o n o v e r l i e s a t l e a s t 800 m o f L a J e n c i a T u f f w h i c h h a s
L a J e n c i aT u f fo u t c r o p s
occur j u s t o f f
e x p o s e db a s e( t h e s et h i c k
t h ew e s t e r ne d g e
of t h e Molino P e a k q u a d r a n g l e ; see P e t t y ,
1979).
The actLial p i n c h - o u t of t h e S a w m i l l Canyon F o r m a t i o n c a n b e
s e e n a t two l o c a t i o n s west o f ,a n d one l o c a t i o n n o r t h e a s t OE
T o r r e o nS p r i n g s
(sec 8 , T. 5 S . , R . 2 W.). The reader is
c a u t i o n e dt h a tt h e s er e l a t i o n s h i p s
show b e t t e r a t map s c a l e t h a n
on t h eg r o u n d .
Many c a t c r o p s are poor i n t h i s a r e a o f low r e l i e f
a n d , more i m p o r t a n t l y , t h e rocks of t h e L u i s Lopez F o r m a t i o n and
are q u i t e sirn.lar l i t h o l o g i c a l l y . A
t h eS a w m i l lC a y o i lF o r m a t i o n
d e t a i l e du n d e r s t a n d i n go f
t h e l o c a l s t r a t i g r a p h y is , r e q u i r e d i n
o r d e r t o p r o p e r l y s e p a r a t e t h e v a r i o u s rock u n i t s a n d to f i l t e r
o u t t h e many p o s t - c a u l d r o n s t r u c t u r e s .
A t t h e s ep i n c h - o u t s ,
t h e T u f f o fC a r o n i t aC a n y o nc a n
be s e e n
t o t h i n and p i n c h out w h i l e t h e o v e r l y i n g Lemitar T u f f c o n t i n u e s
across t h e c o n t a c ta 2 : p a r e n t l yu n c h a n g e d .A c t u a l l y ,t h e
Lemitar
T u f fa p p r o x i m z t e l yd o u b l e si nt h i c k n e s si n
a d i s t a n c eo fa b o u t
o n e mile,
and t h u ss e r v e d
as t h e l a s t f i l l o ft h eS a w m i l l
Canyon
cauldron.
Outflow
O u t f l o w s t r a t i g r a p h i c u n i t s w h i c hp o s t - d a t et h ef i l l i n go f
t h e S a w m i l l Canyon c a u l d r o n are t h e L e m i t a r a n dC h o c l eW e l lT u f f s
a n da ni n t e r l a y e r e dt o n g u eo f
L a Jara Peak Basaltic Andesite.
B o t ho ft h et u f f s
are t e x t u r a l l y zonedupward
from c r y s t a l - p o o r
t o more c r y s t a l - r i c h .I na d d i t i o n ,t h e
Lemitar Tuffshows
from a b a s a l h i g h - s i l i c a r h y o l i t e
upward
c o m p l e xc h e m i c a lz o n i n g
to a r h y o l i t i c c o m p o s i t i o n
t h r o u g h a q u a r t z - l a t i t ei n t e r v a lb a c k
a t t h et o p .T h et e x t u r a lz o n i n gi nb o t hu n i t sa n dt h ec h e m i c a l
z o n i n go ft h e
Lemitar T u f ff r o mr h y o l i t e
upward to q u a r t z l a t i t e
c a nb ee x p l a i n e du s i n g
a r e l a t i v e l y s i m p l e zoned-magma-chamber
model ( s e e Lipmanand
o t h e r s , 1 9 6 6 ) ; however, t h e c h a n g ei nt h e
to r h y o l i t e
u p p e r p a r t o f t h e Lemitar from q u a r t z - l a t i t e b a c k
r e q u i r e s a more c o m p l e xe x p l a n a t i o n .
The c o n c u r r e n te r u p t i o n
two magma s o u r c e s is a p o s s i b l e e x p l a n a t i o n .
B a s i n - F i l lS e d i m e n t a r y
and i n t e r l a y e r e dv o l c a n i c
of
rocks
D e p o s i t so v e r l y i n gt h eC h o c l e
Well T u f f , c o n s i s t i n g o f
b a s i n - f i l ls e d i m e n t a r y
rocks and s e v e r a li n t e r b e d d e dv o l c a n i c
members,comprisetheSantaFeGroup
w i t h i n t h i sq u a d r a n g l e .
In
d e t a i l ,t h es e d i m e n t a r yd e p o s i t sa r eq u i t ec o m p l e x .T h el o w e s t
s e d i m e n t a r yi n t e r v a lc o n s i s t s
of c o a r s e r e d , w e l l - i n d u r a t e d
thick i n
mudflow d e p o s i t s a n dc o n g l o m e r a t e s .T h e s ed e p o s i t sa r e
t h e n o r t h e a s t and s o u t h w e s t e r n p a r t s o f t h e q u a d r a n g l e
and j u s t
n o r t h of t h e n o r t h w e s t e r n c o r n e r o f t h e
map onWaterCanyonMesa.
W i t h i nt h e s ea r e a st r a n s p o r td i r e c t i o n s
i n t h en o r t h e r na r e a s
is
n o r t h w a r d and i n s o u t h e r na r e a s
is s o u t h w a r d T
. h e s eo p p o s i n g
t r a n s p o r td i r e c t i o n ss u g g e s tt h ep r e s e n c e
of a h i g h l a n d i n t h e
c e n t r a l p a r t of t h eq u a d r a n g l ed u r i n ge a r l yS a n t a
Fe time. There
of t h i s p r o p o s e d
a r e a few outcrops of P o p t o s a w i t h i n t h e a r e a
h i g h l a n d ;h o w e v e r ,t h e s ea p p e a r
t o b el o c a l i z e d
i n paleovalleys.
!
:
'
I n t h en o r t h e a s t e r np a r t
of t h e q u a d r a n g l e and i n a d j a c e n t
a r e a sf u r t h e rn o r t h( C h m b e r l i n ,
1980), t h e r e d mudflow d e p o s i t s
a r eo r r e r i ? i nb yr e d ,
brcwn o rg r e e n i s hc l a y s t o n e s .
These u n i t s
a r e niembers o ft h e PoFotosr-.Formation(Denny,
1.940; M a c h e t t e ,
1978).
I n t h es o u t h w e s t e r np a r t
of t h e q u a d r a n g l e t h e r e d
which
mudflow d e p o s i t s a r e o v e r l a i n b y
a w h i t e ,c r y s t a l - p o o rt u f f
i s t e n t a t i v e l yc o r r e l a t e d w i t h t h e t u f f s a s s o c i a t e d w i t h t h e
Pound
Ranch
R h y o l i t e . T h i s t u f f is o v e r l a i n b y b u f f t o t a n ,
p o o r l yt om o d e r a t e l yi n d u r a t e df a n g l o m e r a t e sS. i m i l a r
f a n g l o m e r a t e s d i r e c t l y overllr t h e b a s a l t of MaderaCanyon
i nt h e
s o u t h e a s t e r nc o r n e ro ft h i sq u a d r a n g l e .O i p sw i t h i nt h e s e
f a n g l o m e r a t e sf l a t t e n c p w a r dt on e a r l yh o r i z o n t a l
and t h e
h i 9 h e s . t m e s a - c a p p i n gb a s a l t
d e p o s i t s e x t e n t to t h e b a s e c f t h e
flow i n t h ee a s t e r np a r t
of t h e a r e a and t o t h e t o p s of t h e
h i g h e s tp i e d m o n ts l o p e si nt h ew e s t .
The o l d e s t of t h e s eu p p e r
f a n g l o m e r a t e sa r ec l e a r l yP o p o t o s a
and t h e t o p s a r e a t l e a s t a s
young a s p a r t of t h eS i e r r aL a d r o n e sF o r m a t i o n .
Nc lithologic
b r e a k s or s h a r p a n g u l a r r e l a t i o n s h i p
i s p r e s e n t to m a r k t h e
b e g i n n i n g of S i e r r aL a d r o n e st i m e ;t h e r e f o r e ,t h e s eu p p e r
f a n g l o m e r a t e s a r e mapped a 5 a s i n g l e u n i t -- u p p e r S a n t a Fe
g r a v e l s .T h e s eg r a v e l so v e r l yt h e
Pound
Ranch
R h y o l i t et u f f s ,
b a s a l t ofMadera
Canyon, or t h e b a s a l t ofBearCanyon
and
P o p o t o s ac l a y s t o n e s i n t h e s o u t h w e s t ,s o u t h e a s t
and n o r t h e a s t
p a r t so ft h eq u a d r a n g l er e s p e c t i v e l y .
S e v e r a li n f o r m a lv o l c a n i c
u n i t s and o n ef o r m a t i o n a r e mapped
w i t h i n t h eS a n t aF eG r o u p
i n t h i s a r e a . The r h y o l i t i c l a v a s i n
thecenterpart
of t h e q u a d r a n g l ea r e here c a l l e d t h e PoundRanch
R h y o l i t ef o re x p o s u r e ss o u t h
of
pound
Ranch.
This rhyolite
a f a i r l ye x t e n s i v e
c o n s i s t s of two s m a l l domes (lowermember),
- 9 -
u p p e rl a v af l o w( u p p e rm e m b e r ) ,a n dt h i na s s o c i a t e da s h - f l o w
i n t h e s o u t h w e s t e r nc o r n e ro f
t u f f s .E x p o s u r e s
o fa s h - f l o wt u f f s
i n t h e u p p e rS a n t aF e
t h eq u a d r a n g l e ,w h e r et h e ya r ei n t e r b e d d e d
g r a v e l s and p h y s i c a l l y i s o l a t e d f r o m t h e r h y o l i t i c l a v a s f l o w s ,
w i t h t h e PoundRanch
R h y o l i t eb e c a u s e
aretentativelycorrelated
o fs i m i l a rp h e n o c r y s t sc o n t e n t
and s t r a t i g r a p h i c p o s i t i o n .
A t l e a s tt h r e eb a s a l t i cl a v af l o w sa r ei n t e r b e d d e d
in the
S a n t aF ed e p o s i t s .T h el o w e r m o s t
of t h e s e is h e r e named t h e
b a s a l t ofMadera
Canyon f o re x p o s u r e ss o u t h
and e a s t ofMadera
Canyon i n t h ec e n t r a lp a r t
of t h i sq u a d r a n g l e .
This basalt
n o r m a l l y l i e s , w i t h s l i g h ta n g u l a ru n c o n f o r m i t y ,o nt h ee r o d e d
i t is u n d e r l a i nb y
t o p of t h eC h o c l eW e l lT u f f :h o w e v e r ,l o c a l l y
P o p o t o s as e d i m e n t a r yr o c k si np a l e o v a l l e y s .
T h es e c o n dm a f i cl a v a ,t h eb a s a l t
of BearCanyon
( C h a m b e r l i n , 1980), is i n t e r b e d d e di nP o p o t o s aF o r m a t i o n
c l a y s t o n e si nt h en o r t h e a s t e r np a r t
of t h e q u a d r a n g l e .T h i s
b a s a l t i c l a v a is t r a c e a b l es o u t h w a r di ns c a t t e r e do u t c r o p st o
t h e map and a b a s a l t i c
Broken Tank i n t h e e a s t c e n t r a l p a r t o f
j u s t off
l a v af l o w is found i n a s i m i l a r s t r a t i g r a p h i c p o s i t i o n
No c l a y s t o n e s a r e
t h es o u t h e a s k e r nc o r n e ro ft h eq u a d r a n g l e .
e x p s e da tt h i ss o u t h e r ne x - m s u r e
and t h e t h i n - s e c t i o n t e x t u r e s
a r e s o n e w h a td i f f e r e n t ;t h e r e f o r e ,
no d i r e c tc o r r e l a t i o n
is
possible.
T h ey o u n g e s tb a s a l t i cl a v af l o wi nt h ea r e a ,t h eb a s a l t
of
BrokenTank,
i s h e r ei n f o r m a l l y named f o r BrokenTank
in the
e a s t - c e n t r a lp a r t
of t h e q u a d r a n g l e .
Rere, i t f o r m st h e
mesa
r i m r o c k ,o v e r l y i n gs e v e r a lh u c d r e df e e t
o fu p p e rS a n t aF e
t h e e a s tt h eb a s e l tf l o wl a p sa c r o s s
a
g r a v e l s . One m i l et o
m a j o r f a u l t and d i r e c t l y o v e r l i e s t h e
H e l l s Mesa T u f f ( f i g .
) .
T h i s same b a s a l t i n t e r v a l a l s o
cross o u t a t t h e rimrockonmesas
j u s t e a s t of t h e s o u t h e s s t e r n c o r n e r of t h e q u a d r a n g l e .
I
_
which occur
P i e d m o n ts l o p e ,a l l u v i a lf a n ,
a n ds t r e a md e p o s i t s
throughout t h e areaaremainlydepositsofoldergenerationsof
presentlyexistingdrainages
with similar.sedimentsourceareas.
A w i d e s t r i p of t h e s e d e p o s i t s o c c u r s
i n t h e v a l l e yb e t w e e nt h e
Chupadera and M a g d a l e n am o u n t a i n s .T h eo l d e s t
of t h e s ed e p o s i t s
and may be a s o l d as
have a t h i c k , w e l l - d e v e l o p e dc a l i c h ec a p
middle Pleistocene.
STRUCTURE
A l l known f a u l t s w i t h i n t h i s q u a d r a n g l e a r e y o u n g e r t h a n t h e
two c a u l d r o n sa n dh a v en o r m a ld i s p l a c e m e n t .
T h e c a u l d r o nf a u l t s
w h i c h m u s t be p r e s e n t a r e a p p a r e n t l y b u r i e d b y y o u n g e r v o l c a n i c
u n i t s . The d o m i n a n ts t r u c t u r a lt r e n d
i s N 1 0 t o 25 W andalmost
-
10
-
a l l o ft h ef a u l t sa r ed o w n - t o - t h e - w e s t .S m a l la r e a so f
d o w n - t o - t h e - e a s tf a u l t i n ga r ep r e s e n ta l o n gt h ew e s t e r ns i d eo f
t h e map ( s e c s . 2 and 11, T. 5 S . , R. 3 W . ) and ( s e c s . 1,2,11,12,
T. 4 S., R. 3 W . , u n s u r v e y e d ) .
The s o u t h e r n of t h e s e
d o w n - t o - t h e - e a s tf a u l tz o n e s
i s t h o u g h tt ob e
a s m a l la n t i t h e t i c
h o r s t and g r a b e ns y s t e mc a u s e db yd i l a t i o na l o n g
a n o r m a lf a u l t .
The l a r g e r g r a b e n j u s t s o u t h of S o u t h Canyon and t h e
it apparently
d o w n - t o - t h e - e a s tf a u l t st r e n d i n gs o u t hf r o m
p e n e t r a t e from t h en o r t h .G r a b e n i n g
i s t h e t y p i c a ls t r u c t u r a l
Mesa which l i e s j u s t across SouthCanyon to
s t y l e o n WaterCanyon
t h en o r t h .
I n t h i s a r e a ,S o u t hC a n y o nl i e s
o n t h es o c o r r o
t r a n s v e r s es h e a rz o n e ,
a s t r u c t u r a ld o m a i n boundary a c r o s s w h i c h
i n opposite directions
b e d sa n df a u l tp l a n e s
h a v eb e e nr o t a t e d
(Chapin and o t h e r s , 1 9 7 8 ) . L o c a l l y ,r e l a t i o n s h i p s
may
be
quite
c o m p l e xa l o n gt h i sd o m a i nb o u n d a r y ;t h eg r a b e n i n ga l o n gS o u t h
Canyon is t h o u g h tt ob ea na r e aw h e r es t r u c t u r a le l e m e n t sf r o m
o p p o s i t es i d e s of t h e zone i n t e r f i n g e r .A l t e r n a t i v e l y ,t h e
n o r t h e r nd o w n - t o - t h e - e a s tf a u l t s
may b ey o u n g e rs t r u c t u r e s ,
e x t e n s i o n s of t h ed o w n - t o - t h e - e a s tf a u l tt h a t
bounds t h e east
side of the northern
MagdalenaMountains.
A z o n eo fa n o m a l o u sn o r t h e a s t - t r e n d i n gs t r u c t u r e sc a n
be
t r a c e d d i a g o n a l l yn o r t h e a s t w a r df r o mt h es o u t h x e s tc o r n e r
of t h i s
b e f o l l o w e df o r
Gnly s h o r t
map. Mostof
t h e s ef a c l t sc a n
d i s t a n c e s anci i n many c a s e s t h e d i s p l a c e m e n t c a n
be shown t o join
a n o r t h - w e s tt r e p d i n gf a u l t .
T h e p r e f e r r e di n t e r p r e t a t i o nf o r
is t h a tt h e ya r ej o g s
where n o r t h - w e s t
t h e s eo f f - t r e n df a u l t s
t r e n d i n gf a u l t sh a v ea d j u s t e dl a t e r a l l ya l o n g. p r e v i o u s l ye x i s t i n g
t r a n s v e r s es t r u c t u r e s .T h e s et r a n s v e r s ef a u l t sa r et h e n ,
in
f a c t ,s e g m e n t s o fn o r t h - w e s tt r e n d i n gd o w n - t o - t h e - w e s tf a u l t s .
T h i s zone c f t r a n s v e r s e f a u l t i n g f o l l o w s q u i t e c l o s e l y t h e z o n e
betweeil t h e r i n g f r a c t G r e s
andoute::
t o p o g r a p h i c r i mo ft h e
s o u t h e r nS a w m i l l
Canyon c a u l d r o n . I t , t h e r e f o r e , seems p r o b a b l e
t h a tt h et r a n s v e r s ee l e m e n t s
of t h ey o u n q e rs t r u c t u r ea r e
reflectingthepresenceoftheoldercauldron-relatedstructures.
ALTERATION AND M I N E R A L I Z A T I O N
A l t e r a t i o n w i t h i n t h i s q u a d r a n g l e c o n s i s t s of a w i d e s p e a d
a n dp e r v a s i v ea l k a l im e t a s o m a t i s ma n dm i n o ra r e a so fp r e s u m e d
s u p e r g e n ea l t e r a t i o na l o n g
Ryan H i l l Canyon ( s e c . 1, T. 5 S . , R.
3 W.).
The a l k a l i metasomatism a f f e c t s u n i t s a s young as t h e
u p p e r member o f t h e Pound Ranch R h y o l i t e and a l l of t h e
q u a d r a n g l e n o r t h of t h e a p p r o x i m a t e t r a c e o f
t h e s o u t h e r nS a w m i l l
C a n y o nc a u l d r o nm a r g i n .R e g i o n a l l y ,t h ea r e ao fa l t e r a t i o n
i n c l u d e s m o s t of t h e Magdalena,Chupadera and Lemi t a r M o u n t a i n s
( s e eC h a p i n and o t h e r s , 1 9 7 8 ) .
-
11
-
T h i s formof
a l k a l i exchange a l t e r a t i o n c a u s e s q u i t e
d i s t i n c t p e t r o g r a p h i c and c h e m i c a l c h a n g e sb u th a s
a relatively
minor e f f e c t on
hand
s p e c i m e no ro u t c r o pc h a r a c t e r i s t i c s .M o s t
p l a g i o c l a s e f e l d s p a r is a l t e r e d to c l a y m i n e r a l s or t o a l k a l i
section
f e l d s p a r , which a r eu s u a l l yp l u c k e do u td u r i n gt h i n
p r e p a r a t i o n , and sphene is a l t e r e d to l e u c o x e n e O
. t h e rm i n e r a l s ,
i n c l u d i n ga l k a l if e l d s p a r ,b i o t i t e ,q u a r t z ,
and m a g n e t i t ea r e
a p p a r e n t l yu n a f f e c t e d .C h e m i c a l l y
t h e m a j o rc h a n g e si n c l u d en e t
a d d i t i o n of p o t a s s i u m ,a n dn e t
losses o fc a l c i u m ,s o d i u m ,
magnesium,
( s e eD e A n d r e a ,
1 9 8 1 ) . I t is somewhat
s t a r t l i n g t h a t a rockwhichhasbeenchanged
so much c h e m i c a l l y
l o o k s so f r e s h . R o c k c o l o r ,g r o u n d m a s sa n dp u m i c et e x t u r e ,a n d
. anidine
is u s u a l l y
most p h e n o c r y s t s a r e normal i n a p p e a r a n c e S
c l e a r and b i o t i t e is b l a c k or c o p p e r y and s h i n y .
R e a s o n a b l es u c c e s s i n f i e l d i d e n t i f i c a t i o n o f
t h i s t y p eo f
a l t e r a t i o n h a s been p o s s i b l e u s i n g , a s
a criterion,thepresence
of two d i s t i n c t t y p e s of f e l d s p a r i n a r o c kt h a to t h e r w i s e
is c l e a r to s l i g h t l ym i l k y w i t h
a p p e a r su n a l t e r e d .T h es a n i d i n e
good c l e a v a g e w h i l e t h e o t h e r f e l d s p a r ( p r e s u m a b l y p l a g i o c l a s e )
i s c h a l k y w i t h no c l e a v a g e . T h i s a l t e r a t i o nh a s been
h y p o t h e s i z e dt o
be t h e r e s u l t of a l k a l ie x c h a n g e i n a n a n c i e n t
geothermalsystem(Osburn,1978;Chapin
and o t h e r s ,1 9 7 8 ) .
occurs a t . s c a t t e r e d l o c a t i o n s
M a c a a n e s e - o x i d em i n e r a l i z a t i o n
and have
t h r o u g h c u t t h i s q u a d r a n g l e . Most o c c u r r e n c e sa r es m a i l
b e e ne x p l o r e db yb u l l d o z e rt r a n c e s .
Some o r eh a s
beenproduced
c u t s a l o n gC h a v e sa n d
Mo1ir.o Canyons.Another
f r o ms e v e r a lo p e n
p r o s p e c tw e s t
of Ryan Eill Canyon ( s e c . 2 , T. 5 S . , R. 2 W.) may
haveproduce2 some o r e a's t h e r e is a n a e r i a l tramway i n p ~ s i t i o n
of t h i s
t h e r e ; however, t h e amount of e x c a v a t i o n sn e a rt h eh e a d
trarnwaydoesnotsuggestvery
much p r o d u c t i o n .
Themanganese
m i n e r a l i z a t i o n occurs m a i n l y a s f r a c t u r e a n d
b r e c c i af i l l i n g so f
m a n g a n e s eo x i d e s ,b l a c k
and w h i t e c a l c i t e and
q u a r t z . Minor g a l e n a is p r e s e n ta t o n ep r o s p e c (t S e C .
2 , T. 5
S . , R. 3 W . )
The s p a c i a lc o i n c i d e n c eo ft h em a n g a n e s e
m i n e r a l i z a t i o n w i t h t h ea l k a l im e t a s o m a t i s ms u g g e s t s
a genetic
r e l a t i o n s h i p between t h e two.
.
-
12 -
REFERENCES
Bowring, S. A . , 1980, The geology of t h e w e s t - c e n t r a lM a g d a l e n a
. S. t h e s i s , New
Mountains,SocorroCounty,
New Mexico: M
Mexico I n s t i t u t e of Mining and T e c h n o l o g y , 1 2 7 p .
and s t r u c t u r e of
C h a m b e r l i n , R. M . , 1 9 8 0 , C e n o z o i cs t r a t i g r a p h y
t h e S o c o r r oP e a kv o l c a n i c
c e n t e r , c e n t r a l N e w Mexico: Ph.D.
d i s s e r t a t i o n ,C o l o r a d oS c h o o l
of Mines,495p.
C h a p i n , C . E . , C h a m b e r l i n , R. M . , Osburn, G . R . , W h i t e , D . L . ,
A. R . , 1 9 7 8 , E x p l o r a t i o nf r a m e w o r k
of t h e
a n dS a n f o r d ,
S o c o r r oG e o t h e r m a la r e a ,
New Mexico: New Mexico G e o l o g i c a l
S o c i e t y ,S p e c .
Pub. 7 , p.115-129.
D e Andrea, J . , 1981,
New
Denny, C . S . , 1 9 4 0 , T e r t i a r yg e o l o g y of t h e S a n A c a c i a a r e a ,
Mexico:
J o u r n a l of Geology,
v.
4 8 , p. 7 3-106.
E g g l e s t o n , T . , 1 9 8 1 , Geology of t h ec e n t r a lC h u p a d e r aM o u n t a i n s ,
2.1. S . t h e s i s , N e w Mexico
SOCOrrO County, New Mexico:
. .
i n s t i t u t e of Mining and Technology
K a l i s h , P . , 1 9 5 2 , Geology of t h e WaterCanyonarea,Magdalena
S . t h e s i s , New
Mountains,SocorroCounty,
New Mexico:
Mexico I n s t i t u t e of Mining and Technology,48p.
M
.
Krewedl, D . A . , 1 9 7 4 , Geology of t h e c e n t r a l MagdalenaMountains,
SocorroCounty,
New Mexico: P h . D. d i s s e r t a t i o n , U n i v e r s i t y
of A r i z o n a ,1 2 8 p .
J. T . , 1 9 6 6 , A
Lipman, P. W . , C h r i s t i a n s n , R. L., andO’Connor,
c o m p o s i t i o n a l l y zonedash-flow
s h e e ti ns o u t h e r n
Nevada:
U.
S . G e o l .S u r v e y ,P r o f .P a p e r
524-F, 47 p .
M a c h e t t e , M . N . , 1 9 7 8 ,G e o l o g i c map of t h eS a nA c a c i aQ u a d r a n g l e ,
U. S . G e o l o g i c a lS u r v e y ,
Map G Q
SocorroCounty,
New Mexico:
1415.
M i e s c h , A. T . , 1 9 5 6 , Geology of t h e L u i s Lopezmanganese
N e w Mexico Bureau of
d i s t r i c t , S o c o r r o C o u n t y , New Mexico:
l e s o u r c e sC
, irc.
38, 31p.
Minesand M i n e r a R
Osburn, G . R . , 1 9 7 8 , Geology of t h e e a s t e r n MagdalenaMountains,
to Pound Ranch,SocorroCounty,
New Mexico: X.
WaterCanyon
S . t h e s i s , New Mexico I n s t i t u t e of MiningandTechnology,
150p.
Osburn, G . R . , and C . E. Chapin, 1 9 8 1 , S t r a t i g r a p h i cn o m e n c l a t u r e
f o rC e n o z o i cr o c k s
of t h e n o r t h e a s t e r n D a t i l - M o g o l l o n
v o l c a n i c f i e l d , New Mexico: N e w MexicoBureau
of Mines and
1
M i n e r a lR e s o u r c e s ,S t r a t i g r a p h i cc h a r t
Osburn, G . R . , C h a p i n , C . E . , and E g g l e s t o n , T . , i n p r e s s , T h e
Hells Mesa T u f f and t h eS o c o r r oc a u l d r o n :
N e w MexicoBureau
of M i n e sa n dM i n e r a lR e s o u r c e s ,C i r c .
-
-
13
-
P e t t y , D . M . , 1979,Geology of t h e s o u t h e a s t e r n M a g d a l e n a
M. S. t h e s i s , New
Mountains, Socorro C o u n t y , N e w Mexico:
Mexico I n s t i t u t e of MiningandTechnology,
16s.
R o t h , S. J.,1980,Geology
of t h eS a w m i l l Canyon a r e a , Magdalena
Mountains, Socorro C o u n t y , New Mexico: M. S. t h e s i s , N e w
Mexico I n s t i t u t e of Mining
and
Technology.
P- .
W i l l a r d , M . E . , u n p u b l i s h e d report, Geology of t h eL u i sL o p e z
Manganese d i s t r i c t , N e w Mexico: N e w MexicoBureau
of Mines
a n dM i n e r a l Resources, unpub. report.
W r i g h t , J . V . , and Walker, G . PL. . ,
1 9 7 7 ,T h ei g n i m b r i t e
source
p r o b l e m :s i g n i f i c a n c e
of a c o - i g n i m b r i t el a g - f a l ld e p o s i t :
Geology, v . 5 , p. 729- 7 3 2 .
-
14
-
EXPLANAT ION
Quaternary Alluvial Deposits
[El
ALLUVIAL DEPOSITS:
Q u a t e r n a r ya l l u v i a ld e p o s i t s
w i t h i n t h i s map have b e e ns e p a r a t e di n t o
g e o m o r p h o l o g i cc l a s s e s( s u c ha sa l l u v i a lf a n ,
much
p i e d m o n ts l o p e ,o rv a l l e ya l l u v i a ld e p o s i t s )a s
as was p r a c t i c a l . Most d e p o s i t s ,e x c e p tf o r
c o l l u v i a l and t a l u s deposits, h a v ea l s ob e e n
A l l t h o s ed e p o s i t sw i t hl i t t l eo r
s e p a r a t e db ya g e .
no s o i l development are c l a s s e da s
young w i t ht h e
a d d i t i o n of a s u f f i xl e t t e r" y " .O l d e rd e p o s i t s
w i t h a p p r e c i e b l es o i ld e v e l o p m e n ta r ec l a s s e da so l d
and d e n o t e d w i t h a n " 0 " . $.$e s e q u e n c e sw i t h i n
p i e d m o n ts l o p ed e p o s i t sa r en m b e r e d
fromyoungest
to o l d e s t . Most u n i t s a r eg r e a t e rt h a n
1 meter
t h i c k where mapped and l o c a l l y i n c l u d e minor
a l l u v i a l d e p o s i t s o fo t h e rm o r p h o l o g i e s .
[Qty]
V a l l e y F.lluviurr, ( 0 - 5 0
[Qfyl
f t , 15
ALT
Sa!lds c c g
dr a v e l
i n a c t i v es t r e a mc h a n n e l s ,o rf i n e rg r a i n e dd e p o s i t s
( m a i n l y s i l t and c l a y ) i n a l l u v i a t e d v a l l e y s .
[E] FINE-GRAIND
111)
S X P J CR?A'.7EL,
COLLGVIFL DEPCS7TS:
ALLUVIAL FAN D E P O S I T S :
Minor a l l u v i u m w i t h a l l u v i a l
fan'morphologiesalongsteepscarps.
PIEDMONT SLOPE DEPOSITS (0-150 f t , 4 5 m )
CONGLOMERATES, SANDSTONES, AhG BOULDER ALLUVIUM:
F a n g l o m e r a t e s ,c o n t a i n i n g mixed c l a s t s o f a l l
r o c k st y p e se x p o s e d
i n p r e s e n th i g h l a n d s
[=I
p i e d m o n st l o p ed e p o s i t s
development
w i t h l i t t l e ,i f
major
any, s o i l
o l d e rp i e d m o n ts l o p ed e p o s i t sw i t ha p p r e c i a b l es o i l
development.
soil
[Qp02] Map u n i t s w i t h i n t h e s e d e p o s i t s a r e s e p a r a t e d b y
d e v e l o p m e n at n dr e l a t i v et o p o g r a p h i c
level. T h e s e
u n i t s are numbered f r o my o u n g e s t oo l d e s t .
[Qpol]
[Qtc]
t a l u s / c o l l u v i u m -- u n c o n s o l i d a t etda l u s ,
s o i l - s t a b i l i z e dt a l u sa n ds l o p e
wash d e p o s i t s .
[Q_nl
--
unassigned
gravels
m a i n lp
yi e d m o n t
and v a l l e y
a l l u v i u m , now i s o l a t e d w i t h i n b e d r o c ka r e a sa n d
not
r e a d i l y a s s i g n a b l e to am t h e r map u n i t .
SANTA FE GROUP
--
TertiaryBasin-FillSediments
[x]
Upper S a n t aF eg r a v e l su n d i v i d e d
FANGLOMERATES and SANDSTONES:
(0-500 f t , 150 m )
Buff t o t a n , poorly
i n d u r a t e d ,p e b b l et oc o b b l ec o h g l o m e r a t e sa n d
s a n d s t o n e sF
. ormerly
mapped a sS i e r r aL a d r o n e s
1 9 7 9 ) . The l a c k of
F o r m a t i o n( O s b u r n1, 9 7 8 P
; etty,
a c l e a r - c u tu n c o n f o r m i t yw i t ht h eu n d e r l y i n g
PopotosaFormationprevents
t h i s correlation.
19401 (0-3000 f t , 900 m )
PopotosaFormation[Denny,
FANGLOMERATES,
MUDFLOW
DEPOSITS, MUDSTONES, and
SAKDSTONES: B o l s o nd e p o s i t si n t e r b e d d e dl o c a l l y
w i t h c o n t e m p o r a n e o u sv o l c a n i c
rocks. W i t h i n t h i s
q u a d r a n g l e , t h e lowermost rocks a r eu s u a l l y red
w e l l - i n d u r a t e d mudflow d e p o s i t s which a r e o v e r l a i n
by a t h i c k s e q u e n c e o f p l a y a c l a y s t o n e s ;
r e g i o n a l l y ,h o w e v e r ,t h . e s e
li t h o i c g i e s g r a d o i n t o ,
or i r ' t e r t o n g u e with, o t h e r f a c i e s . One Iozr.;atioris
2nd s e v e r a l .i n f o r m a lv o l c e n i c
members h a v s been
mspped
iriterbedded w i t h t h eP o p o t s s aF o r m a t i o n .
[Tppl
p l a y af a c i e s
-- r e d , brown or G r e e nc l a y s t o n e w
s ith
minorgypsum.These
d e p s i t s become t h i n n e r and
p o s s i b l y ' i n t e r b e d d e d w i t h o t h e r li t h o i o o i e s t o t h e
south.
[ T p l ]
Lower P o p o t o s a -- r e d , well i n d u r a t e d mudflow
d e p o s i t s andminor
conglomerates.
VOLCANIC ROCKS INTERBEDDED I N BASIN-FILL SEDIMENTARY ROCKS
"
Pound Ranch R h y o l i t e
member [Osburn,
19781
10.5 + 0 . 4 m.y.
(0-650
f t , 2 0 0 m ) QUARTZ LATITE LAVA FLOES: Dense,
porphyriticq
, u a r t z - l a t i t el a v af l o w s T
. exturally
zoned f r o mb a s a lb l a c kv i t r o p h y r e ,
t o middle r e d ,
f i n e l y f low-foliated interval, to upper pale-red,
c r u d e l y f l o w - f o l i a t e di n - x r v a l .C o n t a i n s
10-25%
p h e n o c r y s t s of p l a g i o c l a s e ,b i o t i t e ,
and h o r n b l e n d e .
[E]
upper
lower member [Osburn,1978] 1 1 . 8 + 0 . 5 m.y. l a v a s
( 0 - 4 0 0 f t , 1 2 0 m ) RHYOLITE LAVAS: Dense,
c r y s t a l - r i c h ,p a l e - r e d - b r o w nr h y o l i t el a v a s .
A p p a r e n t l y c o n s i s t s oftwo
s m a l l domes or t h i c k l a v a
f l o w sC. r u d e lfyl o w - f o l i a t e dC. o n t a i n s
25-40%
p h e n o c r y s t s of p l a g i o c l a s e ,q u a r t z ,s a n i d i n e ,
b i o t i t e and a t r a c eo fh o r n b l e n d e .
w i t h t h e PoundRanch
a s h - f l o wt u f f sa s s o c i a t e d
Ah13
AIR-FALL
TUFFS:
TWO
R h y o l i t e -- ASH-FLOW
i n many
sequences w i t h d i s t i n c tl i t h o l o g i e sp r e s e n t
p l a c e s b, u u
t s u a l l yc o m p i l e dt o g e t h e r L
. o w e r b, g f f ,
p o o r l yw e l d e di n t e r v a lh a sm i n e r a l o g i c a lc o m p o s i t i o n
s i m i l a r t o t h el o w e rl a v a ;t h eu p p e r ,u s u a l l y
v i t r i c ,d e n s e l y
welded t u f f i s s i m i l a ri nm i n e r a l o g y
t o t h eu p p e rl a v a .
ASH-FLOW
TUFFS
(0-150 f t , 45 m ) : L i g h t - c o l o r e d ,
tuffs. C o n t a i n
c r y s t a l - p o o rp, o o r l yw e l d e da s h - f l o w
1 0 t o 20 p e r c e n t t o t a l p h e n o c r y s t s c o n s i s t i n g of
q u a r t z ,p l a g i c c l a s e ,s a n i d i n e ,b i o t i t e ,
and
h o r n b l e n d eP
. r o b a b l yc o r r e l a t i v e
w i t h Tprt.
R h y o l i t a 1airs.s of Water Cacyon Pies?. (0-560 f t , 1 5 0
m) SILICIC LilS'h FLONS: P i n k to g r s y i s h - r e d ,
p h e n o c r y s t - r i c h ,q u a r
t z - l z k i t e l a v a s .C o n t a i n s1 5
t o 40 p e r c e n t t o t a l p h e n o c r y s t s c o n s i s t i n g - o f
p l a g i o c l a s e ,b i o t i t e ,h o r n b l e n d e
q u a r t z . Most of t h i s u n i t h a s
by Kt0 metasomatism.
and t r a c e so f
b e e ns t r o n c j l ya l t e r e 2
Basaltic Lavas
B a s a l t of Broken Tank (0-150 f t , 45 m ) 6ASALTIC LAVA
FLOWS: G r a y i s h - b l a c km
, i c r o - v e s i c u l a rs, l i g h t l y
p o r p h y r i t i cb a s a l t i cl a v af l o w .C o n t a i n ss p a r s e
p h e n o c r y s t s of p l a g i o c l a s e and c l i n o p y r o x e n e i n a
c o a r s e - g r a i n e dg r o u n d m a s sw i t hs u b o p h i t i ct e x t u r e .
b a s a l t ofBear
Canyon [ C h a m b e r l i n , 19801 (0-50 f t ,
15 m ) BASALTIC LAVA FLOW:
D e n s eb
, lack,
f i n e - g r a i n e d b a s a l t w i t h well-developedophitic
texture.
b a s a l t of MaderaCanyon
[ N e w Name] (0-600 f t , 185 m )
BASALTIC LAVA FLOWS: Gray to b l a c k , d e n s e b a s a l t i c
to b a s a l t i c a n d e s i t e l a v a s c o n t a i n i n g
-
17
-
a few p e r c e n t
p y r o x e n ea n dp l a g i o c l a s ep h e n o c r y s t s .L o c a l l y
some
f l o w sc o n t a i n i n ga b u n d a n to l i v i n e
c l o t s to 2 cm.
TERTIARY ASH-FLOW
TUFFS
AND REGIONAL LAVAS
C h o c l e W e l lT u f f
26 m.y.(0-650
f t , 2 0 0 m ) ASH-FLOW
of
TUFFS: S i m p l et o
compound c o o l i n gu n i t
q u a r t z - r i c h ,o n e - f e l d s p a rr h y o l i t et u f f
Lower
member of l i g h t - g r a y to b r o w n i s h - g r a y ,c r y s t a l - p o o r
( 1 - 4 % ) t u f f and an u p p e r member ofmedium-grayto
p u r p l e - g r a y ,m o d e r a t e l yc r y s t a l - r i c h( 1 5 - 2 5 % )
one-feldspartuff
w i t h abundantchatoyantsanidine
and e u h e d r a lq u a r t z .T h e
two members a r e mapped
t o g e t h e r .S o u r c e
unknown.
-
La J a r a P e a kE a s a l t i cA R d e s i t e
Tongue(0-500
f t , 150
m j BASALTIC ANDESITE LAVAS:
Dark g r a y to p u r p l e ,
f i n e - g r a i n e d ,m a f i cl a v af l o w sU s u a l l yc o n t a i n
1-5%
r e d ,a l t e r e df e r r o - m a g .a n do c c a s i o n a l l yp l a g i o c l a s e
phenocrysts.
..
RHYOZITIC LAVA FLOWS (0-250 f t , 7 5 m ) :
P i n k t og r a y ,
c r y s t a l - p o o r , s i l i c i c l a v a flows. C o n t a i n sf e w ,
if
a n y ,p h e n o c r y s t s ,b u tu s u a l l y
c o n t z i n s prominent
o u t i n two s m a l ls e p a r a t ea r e a s
s p h e r u l i t e s .C r o p s
(sec. 19, T, 4 S . , R . 2 W., andsec:
5 , T. 4 S . , R.
3' w.j
T h e s es e p a r a t eo u t c r o p sm a y : b e
two s m a l l
dcmssor
p a r t s of a l a v af l o w which was l o c a l i z e d i n
a paleo-valley.
The s o u t h v e s t e r n of t h e s e two o u t c r o p s i s u n d e r l a i n
by a s mucn a s 3 0 0 f e e to fp i n kt ob r o w n ,
c r y s t a l - p o o r .. l i t h i c - r i c h a s h - f l o w t u f f s
and
i n t e r b e d d e dc o a r s e - g r a i n e d ,i m m a t u r es a n d s t o n e sa n d
conyiomerates.
.
2 8 m.y. (500 t o 1500 f t , 450 m ) ASHS t r o n g l yz o n e d ,s i m p l ec o o l i n g
u n i t of
a s h - f l otwu fD
f .i v i d e d
i n t o two members a t an
increase i n phenocrystcontent.
L e m i t a rT u f f
FLOW TUFFS:
member
- Medium-red
to
UPPe r
l i g h t - y e l l o w i s h - g r a yr,e v e r s e l y
z o n e dc, r y s t a l - r i c h
tuffs.
Zoned from l o w eprl ,a g i o c l a s e - r i c h ,
q u a r t z - p o o r ' q u a r t zl a t i t ea tb a s e
w h i c hc o n t a i n s
25 t o 35% t o t a l p h e n o c r y s t sc o n s i s t i n g
of
p l a g i o c l a s e ,b i o t i t e ,s a n i d i n e
and h o r n b l e n d e , and
-
18
-
t r a c e s of m a g n e t i t e , t o q u a r t z - r i crhh y o l i taet
t o p which c o n t a i n s a n i d i n eq, u a r t zb, i o t i t e ,
p l a g i o c l a s e and t r a c e so fm a g n e t i t e
and sphene.
R h y o l i t e commonly c o n t a i n sr e dc l o t s
of
of
q u a r t z - l a t i t i c magma s i m i l a r to t h e l o w e r p a r t s
t h e membe r
.
Lower member - L i g h t - g r atypoa l e - r e d ,
c r y s t a l - p o o r (5-15%), homogeneous r h y o l i t i ct u f f s ,
commonly c o n t a i n i n g a l i t h o p h y s a l z o n en e a rt h e
m i d dC
l eo. n t a i n s
5 t o 1 5s%
a n i d i nqeu, a r t z
and b i o t i t e
and t r a cpoelfsa g i o c l a ssep, h e n e
and m a g n e t i t e .
LA J E N C I A TUFF
[ N e w Name]
30-32 m.y.
(0-650
>3000
f t , 9 0 0 m--cauldron
f t , 200 m--outflow,
f a c i e s ) ASH-FLOW TUFFS:
TWO c o o l i n g u n i t s of
d e n s e lw
y e l d e dc, r y s t a l - p o o ro, n e - f e l d s p atru f f .
Both members c o n t a i r : 3 t o 10% s a n i d i n e , minor
s m a lrlo u n d e qd u a r tpz h e n o c r y s t s
and t r a c e s pf
p l a g i o c l a s eb, i o t i t e
and m a g n e t i t e . The
members,
w h i l e q u i t es i a i l a rl i t h o l o g i c a l l yc a nu s u a l l y
be
s e s a r a t e db yt e x t u r e
and s t r a t i g r a p h i c p o s i t i o n .
--
5 r a y to p u r p l e g r a y , p o o r l y
to
uppar member
d e n s e l y welZe.3 t u f f cante.:ir!Ing l a r g e p r r t i a l l y
c o l l a p s e dp u m i c ew h i c h
commonly h a v e i n t e r i o r p a r t s
of
r e p l a c e d b y l a r g ee u h e d r a lv a p o rp h a s ec r y s t a l s
q u a r t z and f e l d s p a r .T h e s ep u m i c et y p i c a l l ya r e
s u r r o u n d e d by a 1 i r ; k i t - c o l o r e dr i n d .
lower member -- l i g h t - p i n k i s h - g r a y t o l a v e n d e r t u f f
t h a t is commonly d e n s e l y welc?ed to t h e b a s e .
U s u a l l yh a ss t r o n g l yl i n e a t e dp u m i c e
and g a s
u n i t . FJithin t h i s
c a v i t i e s i n r e n t e rp a r t so f
q u a d r a n g l et h el i n e a t i o n st r e n db e t w e e n
N 20 W and N
50
W
.
c a u l d r o n - f a c i e s La J e n c i a t u f f -- E x t r e m e l y t h i c k
s e c t i o n of d e n s e l yw e l d e d ,v e r yc r y s t a lp o o r ,
p u m i c e o u sa s h - f l o wt u f f .
Commonly l i g h t t o
medium-gray w i t h dark-reddish-brown t o p u r p l e
pumice.Thepumice
a r eu s u a l l ys t r o n g l yl i n e a t e d
a g e n e r a l l ye a s tw e s td i r e c t i o n .T e n t a t i v e l y
c o r r e l a t e d w i t h t h el o w e r member b e c a u s eo ft h e
l i n e a t e d pumice.
HELLS MESA TUFF: ( C h a p i n , 1 9 7 4 ) 3 3 m.y. (>1600 f t ,
500 m ) ASH-FLOW TUFFS:
S i m p l et o
compound c o o l i n g
u n i t of c r y s t a l - r i c h ( 2 5 - 5 0 % ) q u a r t z - r i c h ,
,
-
19
-
in
t w o - f e l d s p a r r, h y o l i t et u f f s P
. ink
to reddish-brown
when f r e s h a n dd e n s e l yw e l d e d ,g r a y
when p o o r l y
welded or p r o p y l i t i c a l l y a l t e r e d ( m a i n l y i n w e s t e r n
h a l fo f
t h e c a u l d r o n ) .L i t h i c - r i c hz o n e s ,
m e s o b r e c c i a sa n dl a r g ee x o t i cb l o c k s
common, a s a r e
" l a g - f a l l ' 'b r e c c i a s( s e et e x t )n e a rt h et o p
of t h e
section.
CAULDWN F I L L UNITS
Sawmill Canyon-Xagdalena cauldron f ill
Sawmill Canyon F o r m a t i o n [New Name] (0-2500 f t , 7 5 0
m ) ANDESITE LAVAS, 2ISYOLITE LAVAS,
ASH-FLOW
TUFFS,
CONGLOMERATES, and MCDFLOW D E P O S I T S :
Heterolithic
f i l l o fS z d m i l l
Canyon C a u l d r o n .I nn o r t h e r np a r t ,
t h e f i l l c o n s i s t s l a r g e l y of a n c i e s i t i c l a v a s znc2
i n t e r b e d d e d mud- a d d e b r i s - f l o w d e s o s i t s . TO t h e
s o u t h , a n d e s i t e l a v a s i n t e r f i n g e r w i t hr h y o l i t e
l a v a sa n dc o n g l o m e r a t i cs a n d s t o n e s ,a n da r eo v e r l a i n
by a t h i c k i n t r a - c a l d e r a a s h - f l o w t u f f , t h e C a r o n i t a
2 9 . 4 m.y.
Canyon T u f f [New
Name]
Tuff of C a r o n i t a Canyon [ P e t t y , 1 9 7 9 1 2 9 . 4 + 1.1
m.y.
( 0 - 1 2 0 0 f t , 355 m ) ASH-FLOW TUFFS:
M u l t i p l e - f l o w ,s i m p l e - c o o l i n g - c n i t
of a s h - f l o wt u f f s
showing s t r o n gr e v e r s ez o n i n g .U s s a l l yd i v i d e di n t o
two members a t a s h a r p l y g r a d a t i o n a l upward i n c r e a s e
i np h e n o c r y s tc o n t e n ta n dc h a n g e
to r h y o l i t i c
m i neraiogy
.
upper member-- w h i t e t o medium g r a y , c r y s t a l - r i c h ,
m o d e r a t e l yt od e n s e l yw e l d e dt u f f C
. ontains
30-50%
p h e n o c r y s t so fs a n i d i n e ,q u a r t z ,b i o t i t e
andminor
i s o f t e nl a r g e
and p r o m i n e n t l y
m a g n e t i t e .Q u a r t z
( s e c s . 5 & 6 , T. 5 S . , R. 2
d i p y r a m i d a lL
. ocally
W.) c o n t a i n s a t l e a s t
one t h i n s a n d s t o n e p a r t i n g .
lower member -- Brown to r e d d i s h , m o d e r a t e l y
c r y s t a l - p o o r ,p o o r l yt od e n s e l yw e l d e da s h - f l o w
5 2 0 % p h e n o c r y s t so fp l a g i o c l a s e ,
t u f f s .C o n t a i n s
b i o t i t e ,m a g n e t i t e ,
and t r a c e s of c l i n o p y r o x e n e ,
q u a r t z , and s a n i d i n e .L o c a l l yh a sb l a c kb a s a l
vitrophyre.
-
20
-
-
[Txrp]
p o r p h y r i t i c r h y o l i t e l a v a ( 0 - 1 2 0 0 f t , 265 rn)
RHYOLITIC LAVA FLOWS :
[ T x r p t ] Brown t o p i n k i s h - g~ r a y ,p" o r p h y_ r i t i cl a v a
flow.
C o n t a i n s 5-30% p h e n o c r y s t s of s a n i d i n e , q u a r t z , and
minor m a g n e t i t e and b i o t i t e .U s u a l l yc o n t a i n s
1 to
a few p e r c e n t b r o w n i s h - g r a y , p a r t i a l l y
embayed
a n d e s i t e l i t h i cf r a g m e n t s .
CRYSTAL-POOR
RHYOLITIC
LAVAS,
and DOMES ( 0 - 1 0 0 0 f t ,
300 rn):
F i n e - g r a i n e d ,p i n k ,g r a y
or b r o w n ,c r y s t a l - p o o r
to
c r y s t a l - f r e e ,f l o w - b a n d e dr h y o l i t i cl a v a s ,l o c a l l y
similar l i t h o l o g y
o v e r l y i n gm i n o rt u f f so f
C o n s i s t so fs e v e r a li n t r u s i v ep l u g si nS a . m i 1 1
Canyon ( I i o t h , 1 9 8 0 ) a n dl a v a flows i nb o t hS a w m i l l
andRyan H i l l Canyons.
.
ANDESITIC LAVAS ( 0 - 1 5 0 0 f t , 450 m ) : V a r i a b l e
s e q u e n c eo f
a n d e s i t i c l a v a si n c l u d i n gb o t h
f i n e - g r a i n e d and p . o r p h y r i t i c l i t h o l o g i e s .
P l a g i o c l a s ep o r p h y r i t i cl a v a sa r ec o n c e n t r a t e di n
and
t h e nor t h e r n p a r t o f t h e c a u l d r o n e l o n g S i x m i l e
uppermost a n d e s i t e s a r es i m i l a r
S o c t hC a n y o n s T
. he
t o t h e L a J z r a Peak B a s e l t i c A R d e s i t e .
MiJDFLO'N' DEPOSITS, CONGLOMERATES, AND SANDSTGNZS
(0-650 f t , 2 0 0 m ) :
N o r t h e r n e x p s u r e s c o n s i s t of
coarse, angular, heteroli thic
mudflow d e F s i t s and
frcm t h e nortk'erncauldron
m i n o rc o n g l o m e r a t e ss h e d
margin. T h e s e a r e i n t e r b e d d e dw i t ha r d c s i t e
lavas.
S o u t h e r n d e p o s i t s c o n s i s t of c o n g l o m e r a t e s ,n t u d f l o s j
d e p o s i t sa n ds a n d s t o n e si n t e r b e d d e dw i t hr h p l i t e s
a s weli as a n d e s i t e s . C l a s t l i t h o l o g i e si n t h e
n o r t h e r n Z e p o s i t s i n c l u d eS p e a r s - t y p ea n d e s i t e s ,
Hells Mesa T u f f and r h y o l i t i cl a v a s .S o u t h e r n
depositscontainall of thelithologiesfoundinthe
n o r t hp l u sn u m e r o u s
c l a s t s of t h e L u i s L o p e z
Formationwhich crops o u t j u s t t o t h e s o u t h .
"
[El L u i s LopezFormation
[NEW
NAME]
(0-3500 f t , 1100 m )
RHYOLITE
LAVAS,
MAFIC
LAVAS,
ASH-FLOW
TUFFS, AND
SEDIMENTARY
ROCKS:
H e t e r o l i t h i c f i l l of t h eS o c o r r o
C a u l d r o n . Occurs b e t w e e nu n d e r l y i n gc a u l d r o n - f a c i e s
H e l l s Mesa and t h e o v e r l y i n g L a J e n c i a T u f f .
[ E ]
(0- lG00 f t , 5 0 0 m ) C r y s t a l - p o o r ,
R h y o l i tlea v a s
or g r a y ) ,r h y o l i t i c
v a r i e g a t e d( w h i t e ,t a n ,p i n k ,
l a v a s .U s u a l l yc o n t a i n sa b u n d a n tr e ds p h e r u l i t i c
-
21
-
[ S I
[=I
devitrificationstructuresandlocalvitriczones.
C o n t a i n st r a c e s
of b i o t i t e a n ds a n i d i n ep h e n o c r y s t s .
L o c a l l y u n d e r l a i n by:
a na s h - f l o wt u f fo fs i m i l a rl i t h o l o g y
A n d e s i t i lca v a s
(0-150 f t , 45 m ) One o lr o c a l l y
more d a r k - s r a v ,t oP u r p l e ,P l a s i o c l a s e - m r u h v r i t i c
a n d e s i t i ci a v a - f l o w s .C o n t a i n sf r o m
5 to.i5;%
p l a g i o c l a s ec, l i n o p y r o x e n e
and b i o t i t ep h e n o c r y s t s .
"
[E]
Ash-flow
tuffs
( 0- 200 f t , 6 0 m ) W h i ttetoa n ,
c r y s t a l - p o o r pumiceous, and l i t h i c - r i c h t u f f s .
Common c l a s t l i t h o l o g i e s i n c l u d e a n d e s i t i c and
r h y o l i t i cl a v a s ,H e l l s
Mesa T u f fa n ds e v e r a l
v a r i e t i e so fP r e c a m b r i a np l u t o n i ca n dm e t a m o r p h i c
r o c k s . The c l a s t sa v e r a g ea b o u t
6 i n c h e s ,b u t
may
1 m e t e r .T u f fm a t r i xc o n t a i n s
a few
be a s l a r g e a s
p 2 rc e n tq u a r t z
and s a n i d i n ep h e n o c r y s t s ,b u tt h e
pumice a r e l a r g e l y c r y s t a l - f r e e .
[E]
f t , 6 0 m ) : Y e l l o wt o
b u f f ,c r o s s - b e d d e d ,t u f f a c e o u ss a n d s t o n e sa n dt u f f s .
NaL/ be b + s e s u r g e 6 e L w s i t s a s s o c i a t e d
with T
zr.
TL'FFACEOUS SANDSTONES ( 0-200
INTRUSIVE ROCKS
[Tril
RHYOLITEINTRUSIONS:
[w]
WHITE-RHYOLITE
[Tmil
Pink totan,moderately
phenocryst-poor flow-bcp.ded r h y o l i t i ci n t r u s i o n s .
C o n s i s t s o f two s m a l l p l u g - l i k e m a s s e s
( t o 500 f t
a c r o s s )a n a
A t l e a s t two small d i k e - l i k em a s s e s .
C o n t a i n a few p e r c e n t s u b h e d r a l t o e u h e d r a l
s2nidir.e phenocrysts.
DIKES:
White to l i g h t - g r a y ,
f i n e - g r a i n e dr h y o l i t ei n t r u s i o n s T
. y p i c a l l yh a v e
l i g h t c o l o r and s i l i c i f i e dt e x t u r e .T h e r ea r e
s e v e r a lv a r i e t i e sc o n t a i n i n gv a r y i n ga m o u n t s
phenocrysts.
a
of
MAFIC D I K E S :
S e v e r a l t h i n (1 - 20 f t , 6 m ) f i n e
S i m i l e Canyon.
T h e s ea r e
g r a i n e dd i k e so c c u ra l o n g
u s u a l l yb a d l ya l t e r e d .
-
22
-
SYMBOLS
g e o l o g i cc o n t a c t ,d a s h e dw h e r ea p p r o x i m a t e
f a u l t ,d a s h e dw h e r ea p p r o x i m a t e ,d o t t e dw h e r e
o n downthrownblock,
c o v e r e d ,b a ra n db a l l
a r r o w and number g i v e d i p d i r e c t i o n
and a n g l e
offaultplane
s h e a r zone w i t h no p r o v a b l e s t r a t i g r a p h i c
off set
.,
r
+'
c.
g r a v i t ys l i d eb l o c k
'
s t r i k e and d i p ofbedfiing
or compactior.
f o l i a t i o n i n a s h - f l o wt u f f s
h o r i z o n t a l and v e r t i c a lb e d d i n g
s t r i k e and d i p of f l o w f o l i a t i o n
intrusions.
%
c
i n l a v a s and
h o r i z o n t a l and v e r t i c a l f o l i a t i o n
f l o wl i n e a t i o ni nf l o w - b a n d e da s h - f l o wt u f f s
and l a v a s
t r a n s p o r td i r e c t i o n
imbrications)
i n c o n g l o m e r a t e s( p e b b l e
adit
x
p r o s p e c t ,m o s ta r eb u l l d o z e rt r e n c h e s
c3
upen p i t e x c a v a t i o n
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