Geology of a portion of the Pine Creek Quadrangle, Teton and Lincoln counties, Wyoming
by Robert Arthur Lunceford
A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE
in Earth Sciences
Montana State University
© Copyright by Robert Arthur Lunceford (1976)
Abstract:
The Pine Creek Quadrangle lies in western Wyoming in the transition between the Wyoming and
Snake River ranges at the north end of the Wyoming overthrust belt.
Roughly twenty-six Holocene landslides were mapped in the central and western parts of the area,
which are almost exclusively associated with the shale and mudstone of the Cretaceous Bear River and
Aspen formations. The Pleistocene Bailey Creek landslide lies in the northeastern corner of the map
area; the development was a complex event involving at least two separate sliding episodes.
The older landslide dammed Bailey Creek and the Snake River causing the bed loads to be deposited
upstream.
Approximately 12,250 feet of Mississippian through Lower Cretaceous strata crop out in the map area.
Paleozoic strata consist of limestone of the Mississippian Mission Canyon Limestone of the Madison
Group; shale and quartzitic sandstone of the Mississippian, Pennsylvanian, and Permian Wells
Formation; and chert, sandstone, and phosphatic mudstone of the Permian Phosphoria Formation.
Triassic age strata include, in ascending order, siltstone and limestone of the Dinwoody Formation;
sandy siltstone and shale of the Woodside Formation; sandstone and limestone of the Thaynes
Formation; siltstone and sandstone of the Ankareh Formation; and sandstone of the Triassic (?) Jurassic (?) Nugget Sandstone. Strata of Jurassic age comprise the Twin Creek Limestone, chiefly
consisting of shaly limestone; sandstone and siltstone of the Preuss Sandstone; and limestone and
sandstone of the Stump Sandstone, in ascending order. Lower Cretaceous strata consist of, in ascending
order, sandstone, limestone, and shale of the Gannett Group; shale and sandstone of the Bear River
Formation, and overlying Aspen Shale. Conglomerate also occurs in the upper Aspen which is
interpreted to be a tongue of the overlying Frontier Formation exposed to the north and south of the
map area.
Mississippian through Early Triassic age strata were deposited in a transitional area that included the
overthrust belt between a miogeosyncline on the west and a shelf area that covered most of Wyoming.
The miogeosyncline began to be deformed in Late Triassic time and a high area on the west rose and
shed detritus eastward into the marginal basin in southeastern Idaho and western Wyoming.
The map area is situated between the eastward moving Absaroka and Darby thrusts which lie just off
the western and eastern margins, respectively. The Little Greys fault has a minimum displacement of
1,500 feet of Aspen Shale and resulted from overturning along the associated Little Greys anticline.
The central part of the map area, consisting of 7,000 feet of Aspen Shale, is probably further deformed
by overturned folding not evident in the outcrop. STATEMENT OF PERMISSION TO COPY
In p re s e n tin g t h is th e s is in p a r t ia l f u l f i l l m e n t o f the
requirem ents f o r an advanced degree a t Montana S ta te U n iv e r s ity , I
agree th a t th e L ib r a r y s h a ll make i t f r e e ly a v a ila b le f o r in s p e c tio n .
I f u r th e r agree th a t perm ission f o r e x te n s iv e copying o f t h is th e s is
f o r s c h o la rly purposes may be granted by my m ajor p ro fe s s o r, o r , in
h is absence, by th e D ir e c to r o f L ib r a r ie s .
I t is understood th a t
any copying o r p u b lic a tio n o f t h is th e s is f o r fin a n c ia l g ain s h a ll
not be allo w ed w ith o u t my w r it t e n perm ission.
t /I sb^ucArItC.
S ig n a tu re
Date
A c,
3
/ f 7 < £ _________________
GEOLOGY OF A PORTION OF THE PINE CREEK
QUADRANGLE, TETON AND LINCOLN
COUNTIES, WYOMING
by
ROBERT ARTHUR LUNCEFORD
A th e s is subm itted in p a r t ia l f u l f i l l m e n t
o f th e requirem ents f o r th e degree
of
MASTER OF SCIENCE
in
E arth Sciences
Graduate Dean
MONTANA STATE UNIVERSITY
Bozeman, Montana
December, 1976
iii
ACKNOWLEDGMENTS
Deep a p p re c ia tio n and g r a titu d e is extended to P ro fess o r
:
‘
..................
;'
Donald L. Smith f o r h is a s tu te e d i t o r i a l comments and. h elp throughout
the d u ra tio n o f th e p r o je c t .
Dr. Smith served as committee chairman
and f a c u lty a d v is o r as w e ll .
P ro fess o r John Montagne a ls o deserves
re c o g n itio n f o r h is comments concerning the B a ile y Creek la n d s lid e
and f o r s e rv in g on the w r i t e r 's c o m m itte e .. The a d d itio n a l members o f
the com m ittee. P ro fe s s o r Robert Chadwick, P ro fess o r Joseph Ashley
( o f th e Geography Departm ent) and P rofessor Donald Reichmuth (o f the
C iv il E n gineering Departm ent) a re thanked f o r s e rv in g o n .th e com­
m itte e .
Mr. M ilto n E d ie , Mr. Robert T a y lo r and the s t a f f o f the
E a rth Sciences Department a ls o provided help and s u p p o rt.
.
G ra te fu l acknowledgment is extended to D aniel Jcbin and
M arvin Schroeder o f th e U .S. G eological Survey f o r s a la r ie d funding
and h elp d u rin g th e f i e l d
in v e s t ig a t io n .
The many h e lp fu l discussio ns
and comments o f U .S. G eo lo g ical Survey g e o lo g is ts Howard Albee and
J. D. Love a re a ls o a p p re c ia te d .
R ecognition is a ls o given to f i e l d a s s is ta n ts Bruce and Pody
Anderson, and Cody Rama.
Dick and K a tie Hagan provided moral support
d u rin g th e concluding stages o f th e p r o je c t .
TABLE OF CONTENTS
Page
LIST OF FIGURES........................................................................................................v i i
LIST OF TABLES
........................................................................................................
ix
LIST OF PLATES
........................................................................ ...............................
x
ABSTRACT
. . . . . . . . . . . . .
INTRODUCTION
...........................................................
xi
. . ....................................
I
L ocation and Access ...........................
I
P r o c e d u r e ..............................................................
I
Purpose .....................................................................................................................
3
Previous W o r k ........................................................................................................
3
CEOMORPHOLOGY .............................................................................................................
6
Geomorphic S e t t i n g ......................................................................
6
Lan dslides
.............................................................................................................
9
Small L a n d s l i d e s .................................................................................
Large Lan dslides — B a ile y Creek L an d slid e .......................................
9
10
T e r r a c e s .................................................................................................................
15
STRATIGRAPHY
.........................................
. ...........................
. . . . . . .
17
I n t r o d u c t i o n .................................. ...... ...............................................................
17
P a le o zo ic R o c k s .................................................................................
19
In tro d u c tio n
....................................................................................................
M is s is s ip p ia n S t r a t a — Madison Group ................................................
Pennsylvanian S tr a ta — W ells Form ation ...............................................
Permian S tr a ta - - Phosphoria Form ation ............................................
19
19
22
26
V
Page
Mesozoic Rocks
................................
.......................
. . . . . . . . .
32
In tro d u c tio n
.......................................................................................................
T r ia s s ic S tr a ta — Previous Work ..........................................................
Dinwocdy Form ation ..........................................................................................
Woodside Form ation ..........................................................................................
Thaynes F o r m a tio n .................................................................
Ankareh Formation ...............................................................................................
J u ra s s ic S tr a ta — Previous Work ..........................................................
Nugget Sandstone ...............................................................................................
Twin Creek L i m e s t o n e ......................................................................................
Preuss Sandstone ...............................................................................................
Stump S a n d s to n e ...................................................................................................
Cretaceous S tr a ta — Previous Work ..................................... . . .
G annett Group ........................................................................................................
Bear R iv e r F o r m a t i o n ............................................................
Aspen Shale .....................................................................................
Cenozoic Rocks
32
32
34
38
42
45
49
50
53
55
58
60
61
66
74
.......................................................................................................
87
C o n g lo m e r a te ..........................................................................
B r e c c i a .....................................................................................................................
C o llu v iu m .............................................................................................................
A l l u v i u m .....................................................................................
T e rra c e Deposits
...........................................................................................
88
88
88
90
87
STRUCTURAL GEOLOGY......................
Regional S tru c tu re
...............................................................
91
. . . . . .
91
Local S t r u c t u r e ....................................................................................................
95
In tro d u c tio n
....................................................................................................
95
F a u l t i n g ....................................
98
F o l d i n g .......................................................................................................................101
ECONOMIC GEOLOGY
......................................................................................................
SUMMARY................................ ; ..................................................................................... 108
106
vi
Page
NEW CONCEPTS.................................................
Ill
Geom orphology.................................................
Ill
S t r a t i g r a p h y ...............................
Ill
S t r u c t u r e .......................................................................................................
112
REFERENCES C I T E D ....................................
113
A P P E N D IX ........................................................................................................................... 124
v ii
LIST OF FIGURES
Figure
Page
1.
Index map. Pine Creek Quadrangle
..............................................
2.
Index map o f pub lished and in -p ro g re s s g eo lo g ic
quadrangles a d ja c e n t to Pine Creek Quadrangle . . . .
2
4
3.
Upper la n d s lid e and o ld e r , low er la n d s lid e
........................
14
4.
H y p o th e tic a l development o f B a ile y Creek
la n d s lid e and d a m .............................................................................
16
5.
G e n e ra lize d s t r a t ig r a p h ic s e c tio n ..............................................
18
6.
Nomenclature and in te rto n g u in g r e la tio n s h ip s
o f rocks o f Permian a g e .................................................
29
7.
Index map f o r F ig u re 6
....................................................................
30
8.
W est-e ast c ro s s -s e c tio n showing s t r a t ig r a p h ic
r e la tio n s h ip s f o r T r ia s s ic s t r a t a .........................................
33
In te rto n g u in g r e la tio n s h ip s o f Dinwoody
and Woodside fo rm atio n s ...............................................................
39
Nomenclature and s t r a t ig r a p h ic c o r r e la tio n s
o f M idd le and Upper T r ia s s ic fo rm ations ............................
41
11.
C o r r e la tio n diagram f o r Lower Cretaceous s t r a t a . . . .
68
12.
S and-shale c o n ta c t in Aspen Shale . . .....................................
77
13.
Photomicrographs o f sandstone from Bear R iver
Form ation and Aspen Shale ...........................................................
79
14.
C h ert pebble conglom erate in Upper Aspen
82
15.
B rec cia u n it w it h in B a ile y Creek la n d s lid e d ep o sits . .
89
16.
T e c to n ic map o f n o rth end o f o v e rth ru s t b e l t
...................
93
17.
S tru c tu re map o f Pine Creek Quadrangle and
a d ja c e n t a r e a ......................................................................................
96
9.
10.
............................
v iii
Figure
k -»
18.
9.
20.
Page
Development o f L i t t l e Greys a n t i c li n e and
a s s o ciate d f a u l t
.............................................................................
102
L i t t l e Greys a n t i c l i n e , view towards th e n orth
103
. . . .
Composite o f dips along north and south end
o f L i t t l e Greys a n t i c li n e ...........................................................
104
ix
LIST OF TABLES
Table
I.
Page
Volume precentages o f g ra in c o n s titu e n ts ,
cementing ag e n ts , and m a trix from sandstone
and s i 't s t o n e o f th e Bear R iv e r and Aspen
f o r m a t i o n s ..........................................................................................
71
X
L IS T o r PLATES
P la te
I.
G eologic map o f a p o rtio n o f th e Pine Creek
Quadrangle ................................................................
( i n p ocket)
xi
ABSTRACT
The Pine Creek Quadrangle l i e s in w estern Kycming in the
t r a n s it io n between th e Wyoming and Snake R iv e r ranges a t th e north
end o f th e Wyoming o v e rth r u s t b e l t .
Roughly tw e n ty -s ix Holocene la n d s lid e s were mapped in the
c e n tra l and w estern p a rts o f the a r e a , which are alm ost e x c lu s iv e ly
ass o ciate d w ith th e s h a le and mudstone o f th e Cretaceous Bear R iv e r
and Aspen fo rm a tio n s .
The P le is to c e n e B a ile y Creek la n d s lid e l i e s
in th e n o rth e a s te rn c o rn e r o f th e map a re a ; th e development was e
complex event in v o lv in g a t le a s t two sep arate s lid in g episodes.
The o ld e r la n d s lid e dammed B a ile y Creek and th e Snake R iv e r causing
the bed loads to be dep o sited upstream .
A pproxim ately 1 2 ,2 5 0 f e e t o f M is s is s ip p ia n through Lower
Cretaceous s t r a t a crop o u t in th e map a re a .
P a le o zo ic s t r a t a c o n s is t
o f lim esto n e o f th e M is s is s ip p ia n M ission Canyon Limestone o f the
Madison Group; sh a le and q u a r t z i t i c sandstone o f th e M is s is s ip p ia n ,
P e n n sylvan ian , and Permian W ells Form ation; and c h e r t , sandstone, and
phosphatic mudstone o f th e Permian Phosphoria Form ation.
T r ia s s ic
age s t r a t a in c lu d e , in ascending o r d e r , s ilt s t o n e and lim estone o f
the Dinwoody Form ation; sandy s ilt s t o n e and s h a le o f th e Woodside
Form ation; sandstone and lim esto n e o f th e Thaynes Form ation; s i l t ­
stone and sandstone o f th e Ankareh Form ation; and sandstone o f th e
T r ia s s ic (? ) - J u ra s s ic (? ) Nugget Sandstone. S tr a ta o f J u ra s s ic age
comprise th e Twin Creek Lim estone, c h i e f ly c o n s is tin g o f s h a ly lim e ­
s to n e; sandstone and s i lt s t o n e o f th e Preuss Sandstone; and lim estone
and sandstone o f th e Stump Sandstone, in ascending o rd e r.
Lower
Cretaceous s t r a t a c o n s is t o f , in ascending o r d e r , sandstone, lim esto n e,
and sh a le o f th e G annett Group; sh a le and sandstone o f th e Bear R iv e r
Form atio n, and o v e rly in g Aspen S h a le .
Conglomerate a ls o occurs in th e
upper Aspen which is in te r p r e te d to be a tongue o f th e o v e rly in g
F r o n tie r Form ation exposed to th e n o rth and south o f the map a re a .
M is s is s ip p ia n through E a rly T r ia s s ic age s t r a t a were deposited
in a t r a n s it io n a l area t h a t in cluded the o v e rth ru s t b e lt between a
m iogeosyncline on th e w est and a s h e lf area t h a t covered most o f
Wyoming. The m iogeosyncline began to be deformed in L ate T r ia s s ic
tim e and a high area on th e w est rose and shed d e t r it u s eastw ard in to
the m arginal basin in so u th e astern Idaho and w estern Wyoming.
The map area is s itu a te d between th e eastw ard moving Absaroka
and Darby th ru s ts which l i e j u s t o f f the w estern and e a s te rn m argins,
r e s p e c tiv e ly .
The L i t t l e Greys f a u l t has a minimum displacem en t o f
1 ,5 0 0 f e e t o f Aspen S h ale and re s u lte d from o v e rtu rn in g along the
ass o ciated L i t t l e Greys a n t i c l i n e .
The c e n tr a l p a r t o f th e map a r e a ,
c o n s is tin g o f 7 ,0 0 0 f e e t o f Aspen S h a le , is p robably f u r t h e r deformed
by o vertu rn ed fo ld in g n o t e v id e n t in th e o u tcro p .
INTRODUCTION
Location and Access
The map area l i e s
in w estern Wyoming between th e Wyoming and
Snake R iv e r ranges which compose p a r t o f th e Wyoming o v e rth ru s t b e l t .
I t is bordered on the n o rth by the Snake R iv e r and on the south by
th e L i t t l e Greys R iv e r and comprises th e c e n tra l t h r e e - f i f t h s o f the
Pine Creek Quadrangle in c lu d in g p o rtio n s o f T. 36 and 37 N. and R. 117
and 118 W ., Teton and L in c o ln c o u n tie s , Wyoming ( F ig . I ) .
Most o f
th is area is g e n e r a lly in a c c e s s ib le w ith few roads p re s e n t.
The
L i t t l e Greys R iv e r road borders th e southern m argin o f th e map a r e a ,
and w ith perm ission o f the landow ner, access can be gained to the
n o rth e a s te rn co rn e r by a p r iv a t e road on the e a s t s id e o f th e Snake
R iv e r.
A m ajor p a r t o f th e area is a c c e s s ib le by th e use o f pack and
game t r a i l s .
A d d it io n a lly , r e l a t i v e l y easy access to th e n o rth e rn
margin is a t ta in a b le by cro ssin g the Snake R iv e r in a boat o r r a f t .
Procedure
Mapping o f th e Pine Creek area was done on U .S .G .S . 1 :2 4 ,0 0 0
topograp hic maps, and b la c k and w h ite a e r ia l photographs o f a p p ro x i­
m ately th e same s c a le .
to September.
o f 1976.
F ie ld work began in June 1975 and continued
An a d d itio n a l week was spent in th e f i e l d
in August
Traverses were made every o n e -h a lf to o n e -fo u rth m ile
along rid g e to p s , although th is spacing v a rie d somewhat w ith the
amount o f tr e e cover and a v a ila b le outcrops.
HO0 45'
4 3 ° 13'
MO0 M 1SO"
4 3 ° 15'
4 3 ° 0 7 'SO"
MO0 45'
4 3 ° 0 7 '3 0 "
IIO0 SZ i SO"
MILES
Figure I .
Index Map, Pine Creek Quadrangle.
Map area shaded.
LIGHT* DUTY
ROAD
WYOMING
3
Purpose
The p rim ary purpose o f t h is study is to pro vid e a d e t a ile d
g eo lo g ic map o f th e a re a .
The need f o r the map is tw o fo ld :
(I)
to
provide in fo rm a tio n on th e geology o f the Pine Creek Quadrangle which
rep resen ts a s i g n i f i c a n t gap in the p re v io u s ly mapped p o rtio n s o f the
surrounding o v e rth r u s t b e l t ( F ig . 2 ) and (2 ) to co n tin u e th e ongoing
U .S .G .S . in v e s tig a tio n in to the coal and phosphate resources o f th is
re g io n .
A second purpose is to p ro vid e a d e ta ile d summary o f
s t r a tig r a p h ic work in th e re g io n o f the o v e rth ru s t b e l t .
Previous Work
The geology o f th e Pine Creek Quadrangle was f i r s t described
by g e o lo g is ts o f th e Hayden surveys in the l a t t e r p a r t o f th e 19th
cen tu ry (see S c h u ltz , 1 9 1 4 .)
This area was l a t e r in v e s tig a te d in
g r e a te r d e t a il by S c h u ltz (1 9 1 4 ), Boeckerman and E ard ley (1 9 5 6 ),
and by Ross and S t. John (1 9 6 0 ).
In a d d it io n , numerous theses on the
geology a d ja c e n t to th e Pine Creek Quadrangle have been completed by
students a t th e U n iv e rs ity o f M ichigan (see W anless, e t a l_ ., 1955,
and Goeckerman and E a rd le y , 1 9 5 6 ).
Reports on th e economic resources
and geology o f the nearby re g io n , u se fu l because o f th e in cluded
s t r a t ig r a p h ic in fo r m a tio n , were pub lished by Veatch (1 9 0 7 ), M a n s fie ld
(1 9 2 7 ), and S ta a tz and Albee (1 9 6 6 ).
The s tr a tig r a p h y o f th e map
4
110*52'30"
OBSERVATION
PEAK
ALBEE
110*45'
HUNGER MOUNTAIN
ALBEE (1968)
CAMP
DAVIS
SCHROEDER
(1 9 7 4 )
---------------- 4 3 * 1 5 '
(1 9 7 3 )
4 3 * 1 5 ''
ALBEE
FERRY
PEAK
(UN PUB.)
JOBIN
PINE
(1 9 7 2 )
CREEK
BAILEY
LAKE
SCHROEDER
(IN PROGRESS)
(T H IS PAPER)
4 3 * 0 7 '3 0 '
STEWART
PEAK
(UNMAPPED)
DEER
CREEK
(UNMAPPED)
110* 5 2 ' 3 0 "
Figure 2.
PICKLE
4 3 * 07* 30"
PASS
SCHROEDER
(IN PROGRESS)
110* 45 '
Index map o f published and in -p ro g re s s g eo lo g ic quadrangles
a d jace n t to Pine Creek Quadrangle.
Map area shaded.
5
area and the re g io n a d ja c e n t to i t was stu d ie d e x te n s iv e ly by Wanless
et aL
(1 9 5 5 ).
Several g e o lo g is ts have in v e s tig a te d th e te c to n ic s o f the
o v e rth ru s t b e l t and a number o f n o ta b le re p o rts have been p u b lish ed .
E ard ley (1 9 6 0 , 1967) and Crosby (1 9 6 8 , 1969) in v e s tig a te d th e phases
o f orogeny and p a tte rn s o f movement; th e mechanics o f deform ation
were stu d ie d by Rubey and Hubbert (1 9 5 9 ); and Armstrong and O rie l
(1965 ) summarized the te m p o ra l, s p a t i a l , and s t r a t ig r a p h ic r e la tio n s
o f the o v e rth ru s t b e l t .
GEOiIORPHOLOGY
Geomorphic S e ttin g
The study area l i e s in th e M idd le Rocky Mountain Province o f
the Rocky Mountain System, and a t th e t r a n s it io n between the n o rth e rn
end o f the Wyoming Range and the southern end o f th e Snake R iv e r
Range.
T o p o g ra p h ic a lly a m ajor p a r t o f the area is c h a ra c te riz e d by
p a r a l l e l , n o rth w e s t-tre n d in g rid g es and v a lle y s , developed in response
to the interbedded r e s is t a n t and n o n re s is ta n t s t r a t a in v o lved in th e
re g io n a l n o rth w a rd -tre n d in g s t r u c t u r a l g ra in o f the Wyoming c v e r th r u s t
b e lt.
The subsequent drainages which fo llo w the s tr u c tu r e a r e , th e r e ­
f o r e , p a r a lle l over much o f th e a re a .
These streams have not a tta in e d
any graded s t a t e , as evidenced by the la c k o f flo o d p la in s and by
e x te n s iv e headward e ro s io n .
Because o f the y o u th fu l s ta te o f i t s
d rain ag e much o f th e area remains as h ig h lan d s.
The Snake and L i t t l e Greys r i v e r s , and B a ile y Creek over p a r t
o f i t s le n g th , d i r e c t l y cro ss cu t th e s tr u c tu r e and p re s e n t an i n t e r ­
e s tin g geomorphic problem .
I t is suggested here t h a t these streams
may have developed by s u p e rp o s itio n from a M iddle P lio c e n e basin f i l l
o r la k e le v e l.
S everal lin e s o f evidence le a d to t h is s p e c u la tiv e co n clu sio n .
The n e a re s t T e r t ia r y m a t e r ia l, th e M iddle P lio c e n e Teew inot Form atio n,
is exposed n o rth o f th e Pine Creek Quadrangle in Jackson Hole (L o v e ,
1956a) and 7 m ile s w e s t, in th e A lp in e a re a ( M e r r i t t , 1 9 5 6 ).
I t is
7
not known w hether these form ations a re c o r r e la t iv e .
However, they dc
have s im ila r l it h o lo g ie s and f o s s i l s , and both a re suggested to have
formed in a la c u s tr in e environm ent (Love, 1956a, M e r r i t t , 1 9 5 6 ).
The
Teewinot Form ation a t A lp in e has conglom erate beds ( M e r r i t t , 1956)
u n lik e th e Teew inot exposed in Jackson Hole (L ove, 1956a) suggesting
th a t th e Snake R iv e r Range was a highland area p r io r to M iddle
P lio cen e tim e .
F u rth e r evidence o f high topography in t h is area is
im p lie d by th e occurrence o f la rg e s lid e blocks w it h in th e Teewinot
which a re in te r p r e te d to have s l i d westward o f f th e Snake R iv e r Range
(L o ve, 1956b).
I f a connection between th e Teew inot a t A lp in e and
Jackson Hole areas e x is te d north o f th e Snake R iv e r Range, then i t
seems l i k e l y t h a t Teew inot s t r a t a would have been preserved in th e
downwarped Teton Basin d i r e c t l y west o f th e Teton Range.
Love (1956a)
d id not m ention any exposures o f Teew inot s t r a t a in t h is a re a .
There­
f o r e , the probable connection between Jackson Hole and A lp in e during
d e p o s itio n o f th e Teew inot was through th e south end o f th e Snake
R iv e r Range.
This co n clu sion im p lie s t h a t a M iddle P lio cen e cover
may have extended o ve r the study area and th a t th e Snake and L i t t l e
Greys r iv e r s could have been lowered over the b u ried topography.
A lt e r n a t e ly th ese d rainages may have developed from th e la k e le v e l
w ith o u t g r e a t accum ulations o f la c u s tr in e m a te ria l as in th e deeper
basins in A lp in e and Jackson H o le.
During th e P le is to c e n e th e e ro s iv e
power o f these r iv e r s g r e a t ly increased as pre-W isconsin piedmont ic e
8
m elted.
Such ic e e x is te d a t le a s t as near as Munger Mountain
( Montagne, 1976, personal com m unication), 6 m ile s north o f the map
a re a .
I f i t can be proven c o n c lu s iv e ly th a t the Teew inot a t Jackson
Hole and the Teew inot a t A lp in e were n o t co n tin u o u s, then a mechanism
o th e r than s u p e rp o s itio n must be con sid ered.
One p o s s ib il it y may be
the estab lish m en t o f the Snake R iv e r drainage as the Teew inot la k e
a t Jackson Hole s p ille d over i t s bank a t the south end.
As an
a lte r n a te hypothesis th e Snake and L i t t l e Greys r iv e r s may have
developed by headward e ro s io n across th e P lio cen e topography which
c e r t a in ly was more subdued than i t
is a t p re s e n t, and d rain ed in to
the Teewinot la k e on the dow nfaulted block o f A lp in e .
F u rth e r in ves­
t ig a t io n is needed to determ ine w hether o r not the Teew inot sediments
in both th e Jackson Hole and A lp in e areas a re c o r r e la t iv e s .
M ass-wasting is th e most dynamic and n o ta b le geomorphic pro­
cess in th e a re a .
A pproxim ately tw e n ty -s ix la n d s lid e s were mapped,
both a n c ie n t and re c e n t.
Most o f these la n d s lid e s a re lo c a te d in the
c e n tr a l and w estern p a rts o f the map area and a re alm ost e x c lu s iv e ly
asso ciated w ith sh a le and madstone o f th e Cretaceous Bear R iv e r and
Aspen fo rm a tio n s .
9
Landslides
Small Landslides
S m aller la n d s lid e s w it h in th e Pine Creek Quadrangle a re a l l
f a i r l y recent, and most probably a re a t le a s t 50 yea rs o ld ju d g in g from
the th ic k growth o f aspen and lodgepo le pine on some o f th e d e p o s its .
They range in s iz e from sm all d ep o sits ap p ro xim ately 600 f e e t long and
300 f e e t across to la r g e r la n d s lid e s ap p ro xim ately 8 ,0 0 0 f e e t long and
2 ,0 0 0 f e e t across.
The la r g e s t o f these sm all la n d s lid e s is v i s i b l e
from U.S. Highway 26-89 j u s t w est o f Elbow Campground and is a p p ro x i­
m ately \ h square m ile s in a re a .
A nother la rg e la n d s lid e is lo c a te d
on the west s id e o f Cow Camp Creek near th e n o rth ern margin o f th e
map a re a .
A ll o f these la n d s lid e s a re o f the slump type (Thornbury,
1969, p. 4 6 - 6 7 ) , a lth o u g h , in some cases, th e upper su rfa c e o f the
s lid e d e b ris has been subsequently m o d ifie d by mudflows as evidenced
by the hummocks and sparse v e g e ta tio n .
Small springs and ponds have
developed on th e s u rfa c e o f th e la r g e r s lid e s .
O th e rs , such as the
la rg e s lid e west o f Iro n Rim C reek, near the w estern m argin o f the map
a r e a , appear le s s m o d ifie d by continued downs!ope movement o f d e b r is ,
and th e s u rfa c e is q u ite subdued w ith a th ic k growth o f aspen and
lodgepole p in e .
Along th e break-aw ay scarps o f most o f th e s lid e s
in th e area a re s e v e ra l la r g e a rc u a te te n s io n a l cracks along which
m a te r ia l has moved do w n h ill but w ith no r o t a tio n a l component.
Most
10
o f th e s lid e s formed on Bear River-Aspen d ip slopes and probably
re s u lte d from w a te r s a tu r a tio n along bedding planes and j o i n t s .
However, th re e o f the la r g e r la n d s lid e s along the Snake R iv e r moved
p a r a lle l to th e s t r ik e o f the beds and probably re s u lte d from a
com bination o f oversteepened canyon w a lls , and s a tu ra te d bedding
and j o i n t s .
One exception to th e Bear River-Aspen la n d s lid e a s s o c ia tio n
is th e s lid e t h a t occurred in the breached core o f the L i t t l e Greys
a n t i c li n e and t h a t is c o in c id e n t w ith th e a x ia l tra c e (F ig . 1 9 ).
It
in v o lv e s the sandstone and s h a le o f the Lower G annett Group, Stump,
Preuss, and Twin Creek fo rm atio n s and is probably a d ir e c t r e s u lt o f
oversteepening by th e L i t t l e Greys R iv e r and co n cen trate d f r a c tu r in g
in the core o f th e a n t i c li n e .
Large L a n d s lid e s —
B a ile y Creek L an d slid e
The B a ile y Creek la n d s lid e , named by Love and Montagne (1 9 7 5 ,
personal communication) l i e s on th e south bank o f th e Snake R iv e r in
th e n o rth e a s te rn p a r t o f th e map area ( P I . I ) .
T his P le is to c e n e
la n d s lid e was i n i t i a t e d on th e w est f la n k o f Grayback Ridge w ith in
lim esto n e and q u a r t z it e o f th e Madison Group and W ells Form ation.
It
is a complex f e a t u r e , in v o lv in g a t le a s t two s e p a ra te s lid in g e v e n ts ,
3
’
o f which th e e a r l i e r dammed both the Snake R iv e r and B a ile y C reek,
11
r e s u lt in g in d e p o s itio n o f th e Led loads upstream and the fo rm a tio n
o f a la k e in the Snake R iv e r Canyon.
S everal o b s ervatio n s reg a rd in g the gen eral appearance o f th e
s lid e a re s ig n if ic a n t in a n a ly z in g i t s o r ig in and developm ent.
The
f l a t to subdued s u rfa c e o f the la n d s lid e is covered w ith a th ic k
growth o f lo dgepo le p in e , and ty p ic a l signs o f l a n d s l i d in g , such as
ponds and s p rin g s , a re absent.
The la n d s lid e d e b ris , which reaches
a maximum th ic kn ess o f ap p ro x im a te ly 100 f e e t near the n o rth ern
m argin o f the Snake R iv e r , p a r t i a l l y covers Thaynes, Ankareh, Nugget,
and Twin Creek s t r a t a .
o f th e Snake R iv e r.
No la n d s lid e d eb ris occurs on the w est sid e
The m argins o f th e la n d s lid e have been in c is e d
by one la rg e and one sm all canyon.
A w e l l - l i t h i f i e d b re c c ia u n it
(F ig . 1 5 ) , composed p r i n c i p a ll y o f Madison lim esto n e and W ells
q u a r t z it e (see Cenozoic s t r a t a s e c t io n ) , crops o u t along the n orth
w a ll o f th e s m a lle r o f these canyons ( P I.
la n d s lid e d e b ris .
I)
in th e m iddle o f th e
In a d d it io n , a conglom erate u n i t , w ith n e a rly
id e n t ic a l lit h o lo g y to t h a t o f th e b re c c ia u n i t , is exposed along
B a ile y Creek a t th e southern m argin o f th e s lid e ( P I .
I).
This u n it
th ic ken s downstream and the s o r t in g , s t r a t i f i c a t i o n , and slope im ply
th a t i t is a f l u v i a l u n i t .
Fragments o f the Madison Group and W ells
Form ation a re a ls o dep o sited 2% m ile s south o f the la n d s lid e along
B a ile y Creek in a s e r ie s o f re c e n t mudflows.
Love (1 9 7 6 , personal
12
communication) mentioned t h a t s e v e ra l break-away scarps are app arent
along Grayback Ridge in t h is general a re a .
O ther d ep o sits in th e area a d ja c e n t to th e "landslide nave
im p o rtan t im p lic a tio n s reg a rd in g i t s developm ent.
G ra v e l, which may
a t t a in thicknesses o f 400 f e e t (A lbee et^ al_., 1975, p. 1 7 ) , is
deposited from 25 to 50 f e e t above the le v e l o f the Snake R iv e r
n o rth o f the B a ile y Creek la n d s lid e .
A d d it io n a lly , la c u s tr in e
d ep o sits crop o u t above th e Snake R iv e r north o f Hoback Jun ction 7%
m iles north (L o ve, 1976, personal com m unication).
Based on th e p h y s ic a l c h a r a c t e r is t ic s o f th e s lid e and the
nature o f the d ep o sits a d ja c e n t to i t ,
i t is c le a r t h a t th e o r ig in
and development o f the B a ile y Creek la n d s lid e was complex.
I t has
been suggested t h a t th e la n d s lid e re s u lte d in the damming o f B a ile y
Creek and the Snake R iv e r.
T h is is im p lie d by the g ra v e l and
la c u s tr in e d ep o sits along th e Snake R iv e r and the conglom erate u n it
along B a ile y Creek.
The la n d s lid e d e b r is , upon d e p o s itio n , must have
been s tro n g ly l i t h i f i e d
according to Love (1 9 7 6 , personal communica­
t i o n ) , form ing a d u rab le dam in the Snake R iv e r and B a ile y Creek.
The la n d s lid e o r ig in a te d high on the w est f la n k o f Grayback
Ridge where s t r a t a from th e Madison Group and W ells Form ation a re
exposed.
Recent mudflows and break-away scarps a t t e s t to th e b as ic
i n s t a b i l i t y o f these s t r a t a where th ey are exposed on d ip slo p es .
The la n d s lid e may have been i n i t i a t e d by o versteepening r e s u lt in g
13
from e ro s io n by B a ile y C reek, s a tu r a tio n o f bedding p la n e s , and
jo in t in g normal to bedding p lan es .
C o nsiderable tim e elapsed between d e p o s itio n c f the land­
s lid e u n its u n d e rly in g and o v e rly in g th e b re c c ia u n it (F ig . 3 ) as
suggested by th e s tro n g l i t h i f i c a t i o n o f the b re c c ia compared to th e
a d ja c e n t la n d s lid e d e b ris .
Sheetwash g r e a t ly m o d ifie d and reworked
th e s u rfa c e o f th e i n i t i a l
s lid e a llo w in g f o r l i t h i f i c a t i o n . t o occur
b efo re th e o v e rly in g s lid e covered t h is s u rfa c e .
Based on th e f i e l d r e la tio n s h ip s , th e fo llo w in g h is to r y o f
the B a ile y CreeK la n d s lid e is suggested.
During the P le is to c e n e , a
la rg e s l i p s u rfa c e developed in th e w estw ard-dipping lim esto n e and
q u a r t z it e o f the Madison Group and W ells Form ation.
A la r g e mass
o f t h is w a te r-s a tu r a te d m a te r ia l moved down th e w est f la n k o f Grayback
Ridge and along B a ile y Creek and came to r e s t near th e mouth o f B a ile y
Creek, co m p letely c o v erin g s t r a t a o f th e Ankareh, Nugget and Twin
Creek fo rm a tio n s .
As a consequence, B a ile y Creek and th e Snake R iv e r
were dammed by th e s lid e d e b r is ; coarse cobbles and boulders o f
P a leo zo ic and Mesozoic sandstone and q u a r t z it e accumulated along th e
Snake R iv e r; and q u a r t z it e and lim esto n e g rave l along B a ile y Creek.
M a te ria l d e riv e d from th e la n d s lid e was reworked and dep o sited by
sheetwash processes and some o f the d e b ris became l i t h i f i e d
and d e s s ic a tio n .
by ponding
F o llo w in g t h i s , a new s lid e from Grayback Ridge
covered the subdued s u rfa c e .
Erosion continued to m odify the upper
14
UPPER
SLIDE
breccia
LOWER
Figure 3.
SLIDE
Upper la n d s lid e and o ld e r lower la n d s lid e separated by
b re c c ia u n it .
Note strong l i t h i f i c a t i o n o f b re c c ia u n it
compared to a d ja c e n t la n d s lid e d e b ris . Jtn is Nugget
Sandstone.
15
su rfa c e o f t h is l a t e r s lid e and l a t e r a l streams developed which
in c is e d th e m argins, and th e l a s t v e s tig e s o f th e dam were removed
by the Snake R iv e r.
These s e q u e n tia l events a re i l l u s t r a t e d
in
Fig u re 4.
Terraces
Several te rra c e s b o rd er the Snake R iv e r Canyon in th e map
area and n o rth in the Munger Mountain Quadrangle ( A lbee, 1 9 5 8 ).
The
nature o f the d ep o sits form ing on th e te rra c e s is discussed below
(see Cenozoic s t r a t a s e c tio n , page 8 7 ) b u t they g e n e r a lly a re covered
by w e ll rounded boulders and cobbles.
The two te r ra c e sets occur a t
d i s t in c t le v e ls ; an o ld e r h ig h e r s u rfa c e 200-250 f e e t above the
p rese n t r i v e r le v e l and a low er s u rfa c e 10-25 f e e t above th e r i v e r .
Four m iles upstream in th e v i c i n i t y o f A s to ria Hot S p rin g s , Albee
(1 9 6 8 ) mapped two te rra c e s o f th e o ld e r , h ig h er s e t which are
c o r r e la ta b le w itn th e te r r a c e along th e w est m argin o f th e B a ile y
Creek lu n d s lid e , based on th e s i m i l a r i t y o f th e e le v a tio n s above
the Snake R iv e r.
Albee (1 9 5 8 ) suggested t h a t these g rave l te rra c e s
r e s u lte d from th e damming o f th e Snake R iv e r a t th e mouth o f B a ile y
Creek.
16
SNAKE
RIVER
nw
iv \ ^ 4
A. P r e -la n d s lid e topography
B. Lower s lid e and dam
C. Subdued s u r fa c e , development o f b re c c ia
D. Upper s lid e
E. P resent topography
Figure 4.
H y p o th e tic a l development o f B a ile y Creek la n d s lid e and dam.
Formations a re H pPw) W ells Form ation, (p P ) Phosphoria Forma­
t io n , ("Rd ) Dinwoody Form atio n, ("Aw) Woodside Form ation,
( T t t ) Thaynes Form ation, (Tta ) Ankareh Form atio n, (A n )
Nugget Sandstone, ( j t ) Twin Creek Lim estone. S cale approxim ate.
STRATIGRAPHY
In tro d u c tio n
The s t r a t ig r a p h ic s e c tio n w ith in th e map area c o n sis ts o f
M is s is s ip p ia n through Cretaceous s t r a t a (F ig . 5 ) .
The s e c tio n is
predom inantly m a rin e , although nonmarine s t r a t a were deposited d uring
the E a rly T r ia s s ic and E a rly Cretaceous.
C la s tic rocks dominate the
s e c tio n , although carbonate d e p o s itio n occurred d uring the
M is s is s ip p ia n , E a rly T r ia s s ic and M idd le J u r a s s ic , r e f le c t i n g th e
te c to n ic h is to r y o f th e o v e rth ru s t b e l t and a d ja c e n t p a rts o f
Wyoming, Id ah o , and Utah.
The elem ents o f t h is te c to n o -sed im en tary system c o n s is t o f
a s h e lf on th e e a s t where the s t r a t a a re t h in , and a m iogeosyncline
on the w est where th e rocks a re t h ic k , and a t r a n s it io n a l area
between, which in c lu d es th e o v e rth r u s t b e l t .
The p o s itio n o f the
t r a n s it io n a l area s h if t e d throughout the P a leo zo ic and Mesozoic w ith
m ajor im pact on th e lit h o lo g ie s and s ite s o f maximum d e p o s itio n .
In
Late T r ia s s ic tim e , th e m iogeosyncline began to break up and a d i f ­
fe r e n t p a tte rn emerged whereby a high area on th e west rose and shed
d e t r it u s eastward in to th e m arginal b a s in .
D e s tru c tio n o f the
m iogeosyncline in L ate Mesozoic tim e was a p recu rs o r to th e develop­
ment o f la rg e n o rth -s o u th tre n d in g fo ld s and eastward moving t h r u s t
f a u lt s which e v e n tu a lly r e s u lte d in the deform ation o f th e Pine
Creek area (Armstrong and O r i e l , 1 9 6 5 ).
18
" - p i— ™-1p e
ABBREVIATED LITHOLOGY
GREEN-GREY, SPLINTERY. OCCASIONALLY CALCAREOUS. SILICEOUS SHALE, INTERBEDDED GREY-GREEN.
FINE- TO MEDIUM-GRAINED. THIN-BEDDED TO MASSIVE. AND CROSS-BEDDED. OCCASIONALLY
CALCAREOUS, "SALT AND PEPPER" SANDSTONE. AND BLUE, PINK, GREEN. GREY, RED. BLUE-GREY,
BANDED. SPOTTED. SPECKLED. CONCHOI DAL FRACTURING, PORCELANITE
PREDOMINANTLY BLACK TO DARK-GREY SHALE. IDENTICAL TO SHALE IN LOWER BEAR RIVER. INTERBEDDED WITH LIGHT-GREY. FINE-GRAINED, SANDSTONE AND SILTSTONE
'LIGHT-GREY. BUFF-GREY-WEATHERING, FINE- TO MEDIUM-GRAINED, SUBROUNDED TO SUBANGULAR.
MASSIVE AND CROSS-BEDDED, LIMONITIC, QUARTZOSE, RESISTANT SANDSTONE
DARK-GREY TO BLACK. HARD, SPLINTERY, LIMONITIC. POORLY EXPOSED SHALE. AND INTERBEDDED
DARK-GREY, MEDIUM-GREY, GREEN-GREY, THIN- TO MEDIUM-BEDDED, OCCASIONALLY CALCAREOUS,
NODULAR, LIMONITIC. SILTY MUDSTONE. SILTY SANDSTONE, AND FINE-GRAINED SANDSTONE, WITH
BIOTURBATION STRUCTURES. AND SOLE MARKINGS
BUFF-GREY. FINE- TO MEDIUM-GRAINED. CALCAREOUS. QUARTZOSE SANDSTONE AND GREY-PURPLE TO
TANN I SH-GREY, WHITE-WEATHERING, MICRITIC LIMESTONE
- RED-PURPLE TO RED-BROWN, VERY FINE- TO MEDIUM-GRAINED SANDSTONE, AND ASSOCIATED CHERT
PEBBLE CONGLOMERATE
'GREY-GREEN, MEDIUM-GRAINED. GLAUCONITIC, CALCAREOUS, CLIFF-FORMING
CL
SANDSTONE
BROWN-GREY, OOLITE BEARING. COQUINOID, SANDY LIMESTONE
JlREEN-GREY, VERY FINE-GRAINED, CALCAREOUS SANDSTONE
"RED-BROWN, FINE-GRAINED, THINLY BEDDED TO LAMINATED SANDSTONE AND SILTSTONE
LIGHT-GREY. THINLY BEDDED, SHALY LIMESTONE. AND A FEW INTERBEDS OF GREY- TO BLUE-GREY,
FINE-GRAINED. OOLITIC, COQUINOID, LEDGE-FORMING LIMESTONE
BLUE-GREY, THINLY BEDDED LIMESTONE AND OVERLYING RED SHALE
WHITE. PI NKI SH-ORANGE. AND LIGHT-TAN, BROWN-WEATHERING, MEDIUMj GRAINED, MASSIVE,
OCCASIONALLY CROSS-BEDDED. RESISTANT, RI DGE-FORM I NG SANDSTONE
INltKDtUUtU HHKUUN 3 ILI3 IUNt , rt" D
tU
JU
r ntl
WITH GREY, WELL DEFINED, CALCAREOUS NODULES
RED BROWN, VERY FINE-GRAINED. NONRESI STANT SANDSTONE
THAVNES
FM
INTERBEDDED GREY. VERY THINLY BEDDED LIMESTONE. AND YELLOW-TAN, VERY FINE-GRAINED.
CALCAREOUS SANDSTONE
RED-BROWN, VERY FINE-GRAINED SANDSTONE
INTERBEDDED MEDIUM-GREY LIMESTONE AND VERY FINE GRAINED. VERY THINLY BEDDED SANDSTONE
WOODSIOE
FM
RED-BROWN, VERY FINE-GRAINED. POORLY EXPOSED SANDY SIlTSTONE AND SHALE
BLUL-GPEv , LITHOGRAPHIC LIMESTONE
CNNWOOOY
GREY. SILICEOUS. SILTSTONE
FM
LIGHT-GREY, VERY FINE-GRAINED, CALCAREOUS SANDSTONE
150'
1250'
' INTERBEDOED YELLOW-BROWN. FINE-GRAINED. QUARTZOSE SANDSTONE, GREY-BROWN DOLOMITE, DARK___ BROWN-GREY MUDSTONE. SHALE . SILTSTONE. AND YELLOW-BROWN, BEDDED CHERT
DARK-GREY, PHOSPHORITE AND MUDSTONE AND INTERBEDDED BLACK, ARGILLACEOUS DOLOMITE
LIGHT- TO YELLOW-GREY. FINE-GRAINED, CROSS-BEDDED, QUARTZITIC SANDSTONE. AND INTERBEDDED
LIMESTONE
MEDIUM- TO DARK-GREY. MEDIUM-GRAINED LIMESTONE, AND INTERBEDOED DARK-GREY LIMESTONE
INTERBEDDEO DARK-GREY LIMESTONE. RED SHALE. CALCAREOUS S I LTSTONE. AND SANDSTONE
C
Figure 5.
T M
, r L
^ T
V
^ ^
T° COARSE-GRAINED. MASSIVE TO THICK-BEDDED. BIOCLASTIC.
G en eralized s t r a tig r a p h ic s e c tio n . Pine Creek Q uadrangle,
south o f Snake R iv e r.
Not to s c a le .
19
P aleo zoic Rocks
.
In tro d u c tio n
Tho exposed P a le o zo ic s e c tio n is ap p ro x im a te ly 2 ,2 6 0 f e e t
th ic k in the map area and in c lu d es lim esto n e o f th e M ission Canyon
o f the Madison Group o f M is s is s ip p ia n ag e , e la s t ic s and carbonates
o f the W ells Form ation o f M is s is s ip p ia i, P en n sylvan ian , and Permian
age, and phosphatic mudstone and e la s t ic s o f th e Permian Pliosphoria
Form ation.
Exposures o f these s t r a t a are co n fin ed to the n o rth ­
e a s te rn corner o f th e map area where they form r e s is t a n t outcrops
along the f la n k o f Grayback Ridge.
M is s is s ip p ia n S tr a ta — Madison Group
Previous Work.
The Madison Group, in c lu d in g th e o v e rly in g
M ission Canyon Limestone and u n d e rly in g Lodgepole Lim estone, has been
e x te n s iv e ly s tu d ie d throughout i t s e x te n t in Montana, th e Dakotas,
U tah, Idaho, and Wyoming.
Andrichuk (1 9 5 5 ) s tu d ie d th e s tr a tig r a p h y
and sed im entatio n o f th e Madison Group in Wyoming and southern
Montana.
S tr ic k la n d (1 9 5 6 ), and Sando and Dutro (1 9 6 0 ) in v e s tig a te d
the Madison in w estern Wyoming, and Sando (1 9 6 7 a ) stu d ie d th e Madison
in p o rtio n s o f the o v e rth ru s t b e l t , in c lu d in g areas a d ja c e n t to the
Pine Creek Quadrangle.
Wanless et^al_. (1 9 5 5 ) measured s e c tio n s o f
the Madison Group a t Pow Wow P o in t one m ile e a s t o f the n o rth e a s t
co rn e r o f the Pine Creek Q uadrangle, a t Hoback Canyon e a s t o f th e
20
map a r e a , and a t o th e r l o c a l i t i e s
in th e T e to n , Cros V e n tre , Lnd
Snake R iv e r ranges.
Age ard Contact s .
The age o f th e Madison Group has been
w e ll documented by abundant f o s s il data and rep res en ts an in te r v a l
o f v i r t u a l l y continuous d e p o s itio n from e a r ly Kinderhook to e a r ly
Mcramec tim e (Sando, 1967b ).
The c o n ta c t o f the Madison w ith the
u n d erlyin g Darby Form ation o f Devonian age Is a re g io n a l unconform ity
{Benson, 1 9 6 6 ).
A d ark s h a le u n it o v e r lie s th e Darby and u n d e rlie s
th e Lodgepole throughout th e t h r u s t b e l t and southw estern Montana
(Benson, 1966, F ig . 2 ) th a t should be in clu d ed w ith th e Madison in
w estern Wyoming (Benson, 1 9 6 6 ).
The c o n ta c t o f t h is u n it w ith th e
o v e rly in g Madison Grouo is a d is c o n fo rm ity , alth ough the tim e i n t e r ­
val represented by th e gap is s h o rt (Haun and K ent, 1 9 6 5 ).
This
sh a le u n it was d ep osited a t th e same s t r a t ig r a p h ic p o s itio n as th e
Cottonwood Canyon member o f th e Madison Limestone o f w e s t-c e n tra l
Wyoming (Love and K e e fe r, 1 9 6 9 ).
C o rr e la tio n s .
The Madison Group has had a confusing h is to r y
o f nom enclature as o u tlin e d by Sando and Dutro (1 9 6 0 , 1 9 7 4 ).
C o ll ie r
and C a th c a rt (1 9 2 2 ) were th e f i r s t to use th e name Madison as a
group in t h e i r work in th e L i t t l e Rocky Mountains o f Montana and
d iv id e d i t in to an o v e rly in g M ission Canyon Lim estone and u n d e rly in g
Lodgepole Lim estone.
Andrichuk (1 9 5 5 ) and S tr ic k la n d (1 9 5 6 )
separated the Madison Group in to a t r i p a r t i t e d iv is io n but Sando
21
and Dutro (1 9 6 0 ) r o je c ta d th ese s u b d iv is io n s ?rd recognized o n ly the
Lodgepols Limescone and M ission Canyon Limestone in w estern '.iyuning.
This tw o fo ld nom enclature has p e rs is te d and is used throughout
Montana as w e ll.
East o f th e o v e rth ru s t b e U , th e name Madison Lime­
stone is used because th e Lodgepole" and M ission Canyon Limestone are
not re c o g n iza b le as d i s t i n c t l i t h i c un1*ts (Sando, 1967a, p. 5 3 7 ).
West o f the t h r u s t b e l t in so u th eastern Idaho and northw estern U ta h ,
th e Lodgepole Limestone name is used and th e B raze r Dolom ite is th e
approxim ate tem poral and l i t h i c e q u iv a le n t o f th e M ission Canyon
Limestone (Sando, 1967b, p. 3 5 ).
L ith o lo g y .
Only th e upper 800 f e e t o f th e M ission Canyon
Limestone is exposed in th e extreme n o rth e a s te rn p a r t o f th e map a re a .
H e re , i t c o n s is ts o f medium- to d a rk -g re y , medium- to c o a rs e -g ra in e d ,
m assive- to th ic k -b e d le d , b io c la s t ic lim esto n e t h a t forms prom inent
c liffs .
The upper p a r t o f th e M ission Canyon co n tain s a few d o lo m itic
lim estone and b te c c ia te d lim esto n e beds.
The Lodgepole in th e a d ja ­
cen t F e rry Peak Quadrangle is composed o f d a rk -b lu e -g re y to mediumg re y , t h in - to medium-bedded, v e ry fin e -g r a in e d lim estone w ith
abundant b io c la s t ic beds in th e upper p a r t (J o b in , 1 97 2).
The lit h o lo g y o f th e Madison Group is rem arkably uniform
throughout i t s e x te n t c o n s is tin g m ain ly o f carbonate s t r a t a w ith very
few c la s t ic in te rb e d s .
The most s ig n if ic a n t change in lit h o lo g y is
the high percentage o f d o lo m ite in th e area which ro u g h ly corresponds
22
w ith the-Wyoming s h e lf .
In so u th eastern Id ah o , th e o v e rth ru s t b o l t ,
and southwestern Montana, d o lo m ite is a m inor l it h o l o g i c component
(A n iric h u k , 1S55).
L o c a lly , e a s t o f th e map area near Cream P u ff
Mountain in th e low er end o f Hoback Canyon, th e M ission Canyon Lime­
stone co n tain s s e v e ra l beds o f gypsum up to 50 f e e t th ic k (Wanless
et a l. ,
1 9 5 5 ).
Environment o f D e p o s itio n .
The d e p o s itio n a l environm ent o f
the Madison Group in th e study area was open m arine w ith m oderately
deep w a te r d u rin g d e p o s itio n o f the Lodgepole and sh a llo w e r w a te r
during d e p o s itio n o f the M ission Canyon.
During th e Late
M is s is s ip p ia n re g re s s io n (Haun and K en t, 1 9 6 5 ), p a rts o f the sea
became b arred (lo w e r Hcback Canyon a re a ) and e v a p o rite s were p r e c ip i­
ta te d in r e s t r ic t e d b as in s .
E v e n tu a lly , a k a r s t s u rfa c e developed
on th e exposed Madison s t r a t a and th e ensuing s o lu tio n e f f e c t s
extended down to the e v a p o r ite beds, le a c h in g o u t s o lu b le c o n s titu e n ts
and producing c o lla p s e b re c c ia s (Sando, 196 7b ).
Pennsylvanian S tr a ta — W ells Form ation
Previous Work.
Not much s ig n if ic a n t work has been done on
th e Upper M is s is s ip p ia n to Lower Permian W ells Formation s in ce i t was
named by Richards and M a n s fie ld (1 9 1 2 ) f o r exposures in W ells Canyon,
Idaho.
However, se v e ra l papers have been published on th e l i t h o ­
l o g ic a ll y and te m p o ra lly e q u iv a le n t Amsden and Tensleep fo rm a tio n s o f
23
w e s t-c e n tra l and c e n tr a l Wyoming (see M a llo r y , 1 9 5 7 ).
Wanless e t a l .
(1955 ) u t i l i z e d Amsden and Tensleep term in o lo g y and measured a
s e c tio n on th e w est f la n k o f Grayback R idge, d i r e c t l y across from
Cabin Creek on the n o rth e rn border o f th e map a r e a , and a t Hoback
Canyon, f i v e m ile s to the n o rth e a s t.
Ags and C o n ta cts.
The age o f the W ells Form ation is com pli­
cated by th e la c k o f d ia g n o s tic fau n al data and is based on th e ages
o f its
temporal and l i t h i c e q u iv a le n ts .
The W ells is considered to
be M is s is s ip p ia n to Permian in age by U.S. G eological Survey g eo lo ­
g is ts in the area ( e . g . , Al bee, 1968, J o b in , 1 9 7 2 ).
The
M is s is s ip p ia n (C h e s te r) age is based on the age assignment o f the
u n d erlyin g Amsden Form ation ( M a llo r y , 1967) which was in clu d ed in
th e W ells in th e map a re a .
The l i t h o l o g i c a l l y and te m p o ra lly equ iva­
le n t Tensleep Sandstone is lowermost Permian (Wolfcamp) a t the
w estern l i m i t o f i t s exposure ( M a llo r y , 1 9 6 7 ).
A Permian age is als o
in d ic a te d by the conform able c o n ta c t o f the W ells w ith th e o v e rly in g
Grandeur Member (Leonard) o f th e Park C ity Form ation in so u theastern
Idaho (McKelvey e t a l_ ., 1959) which was a ls o mapped w ith th e W ells
in the Pine Creek a re a .
A re g io n a l d is c o n fo rm ity is p re s e n t a t th e
base o f the W ells where th e Amsden is in c o n ta c t w ith th e u n d e rly in g
Madison Group, although th e n a tu re o f t h is c o n ta c t is not d is c e rn a b le
in th e study a re a .
24
C o r r e la tio n s .
Use o f th e name W ells Formation is con fined
to westernmost Wyoming south o f Jackson, extrem e so u th eastern Id ah o , •
and n o rth e rn Utah.
Amsden and Tensleep term in o lo g y is used in the
Gros V entre Range and eastw ard f o r s t r a t a dep o sited d u rin g th e same
tim e as th e W e lls l
In southw estern Montana and Yellow stone P a rk ,
th e Quadrant Formation and u n d e rly in g Amsden are e q u iv a le n t to th e
W e lls .
L ith o lo g y .
In the map area th e W ells Form ation is a p p ro x i­
m ately 1 ,2 5 0 f e e t t h ic k and can be d iv id e d in to two m ajor u n it s .
The
lower u n it o f the W ells c o n s is ts o f medium- to d a r k -g r e y , medium­
grain ed lim estone and in terb ed d ed d a rk -g re y lim e s to n e in the upper
p a r t and interb edded d a rk -g re y lim e s to n e , red s h a le , and y e llo w -g re y
to re d , calcareous s i lt s t o n e and sandstone in th e low er p a r t (J o b in ,
1 9 7 2 ).
The upper u n it predo m inan tly c o n sis ts o f l i g h t - to y e llo w -
g re y , f in e - g r a in e d , cross-bedded, q u a r t z i t i c sandstone and some i n t e r
bedded, m edium -grey, w h ite -w e a th e rin g , m assive, c h e rty d o lo m ite and
d o lo m itic lim e s to n e .
Sandy, massive lim esto n e beds, probably equ iva­
l e n t to the Grandeur tongue o f the Park C ity F orm atio n, were included
w ith th e upper few f e e t o f th e W ells in the map a re a .
A t th e type l o c a l i t y , th e W ells in clu d es a low er sandy and
c h e rty lim estone u n i t , a m id dle sandy u n i t , and an upper calcareous
sandstone o r s ilic e o u s lim esto n e u n it (R ichards and M a n s fie ld , 1 9 1 2 ).
McKelvey e t al_. (1 9 5 9 , p. 15) l a t e r assigned the upper s ilic e o u s
<
25
lim estone to tn e Grandeur Member o f the Park C ity Form ation.
Although Richards and M a n s fie ld 's type s e c tio n d e s c rip tio n is
g e n e ra liz e d , t h e i r m iddle u n it is somewhat less q u a r t z i t i c w ith
calcareous sandstone and lim esto n e predom inating and t h e i r upper u n it
is dominated by lim e s to n e , th e o p p o site o f t h a t found in th e W ells in
th e map a re a .
This tre n d con tinues f a r t h e r to th e w est where the
O quirrh Formation o f so u th eastern Idaho is predom inantly lim estone
and sandy lim e s to n e , in te r c a la te d w ith minor amounts o f calcareous
sandstone (Beus, 1968, F ig . 1 0 ).
East and north o f th e Pine Creek
area th e W ells e q u iv a le n ts a re l i t h o l o g i c a l l y s im ila r to the W ells
in the study area (see Uanless e t a l_ ., 1955, p. 3 1 -3 4 , P la te 1 8 ).
The u n d e rly in g Amsden Form ation throughout i t s e x te n t in
:
*
:
^ ,
"
. . . . . . .
Wyoming can be separated in to th re e l it h o l o g i c d iv is io n s :
,
(I) a
basal sandstone, th e Darwin Member, ( 2 ) a m edial red s h a le u n i t , and
(3 ) an upper c h e rty lim esto n e u n it (M a llo r y , 1 9 6 7 ).
The Tensleep
Sandstone is predom inantly sandstone and q u a r t z it e w ith b ro ad ly
l e n t ic u la r carbonate beds com prising less than 20 p erce n t o f th e
to ta l
( M a llo r y , 1 9 6 7 ).
Environment o f D e p o s itio n .
W ells s t r a t a were d ep osited on
a broad s h e lf in w estern and c e n tr a l Wyoming.
D e tr itu s was shed from
w estern and e a s te rn sources (Arm strong and O r i e l , 1965) in to a b a s in a l
area in so u th eastern Idaho which was a p p re c ia b ly more calcareous than
the m argins.
E a rly unstableness re s u lte d in th e emergence and
26
submergence o f th e s h e lf area which g ra d u a lly gave way to a p a r t ia l
w ithdraw al o f th e sea in Late Pennsylvania tim e (M a llo r y , 1 9 /2 ) .
Limestone was d ep o sited a l t e r n a t e ly w ith sandstone in th e study area
as m inor flu c tu a tio n s in th e w a te r depth o ccurred.
Wind and c u rre n t
d is t r ib u t io n and o s c illa t io n s o f the sea c o n s ta n tly s h ifte d a system
o f dunes, beaches, b a r r ie r is la n d s and carbonate s h o a ls , producing
complex in te rb e d d in g .
Permian S tr a ta — Phcsphoria Form ation
Previous Work.
Permian age s t r a t a a re rep resen ted by the
Fhosphoria Form ation which has been subdivided in to two u n its which
in c lu d e s t r a t a from th e in te rto n g u in g Shedhorn Sandstone and Park
C ity Form ation.
S everal s tu d ie s have been undertaken on these rocks
since the U .S. G eo lo g ical Survey began in v e s tig a tin g th e w estern
phosphate f i e l d
p r io r to 1910.
A d e ta ile d l i s t i n g o f these e a r ly
c o n trib u tio n s is beyond th e scope o f t h is paper but an e x c e lle n t
review can be found in Sheldon's (1963 ) work on the m in eral resources
and s tr a tig r a p h y o f the Permian rocks o f w estern Wyoming.
re c e n t work on th e Phosphoria Form ation and i t s
More
e q u iv a le n ts which
in clu d es the area o f t h is study has been undertaken by Sheldon (1 9 5 5 ,
1956, 1 9 5 7 ), McKelvey e t al_. (1 9 5 6 , 1 9 5 9 ), and McKee e t al_. (1 9 6 7 ).
Wanless jat a L
(1 9 5 5 ) measured s e c tio n s o f the Phosphoria Formation
27
a t M a rtin C reek, j u s t to th e n o rth 'o f th e map a r e a , and in the a d ja ­
cen t Snake R iv e r and Hoback ranges.
Age and C o n tacts.
The Phcsphoria Form ation and the rocks
th a t in te rto n g u e w ith i t a re considered to be Permian in age based
on abundant f o s s il data (McKelvey e t a ] L , 1 9 5 9 ).
The low er c o n ta c t
w ith the W ells Form ation in the Pine Creek Quadrangle is not exposed
due to cover so i t
conform able th e r e .
is undeterm ined w hether or not t h is c o n ta c t is
However, in th e n o rth p a r t o f the a d ja c e n t
Wyoming Range, Sheldon (1 5 6 3 , p. 8 4 ) in d ic a te d t h a t th e Meade Peak
Member o f th e Phosphoria Form ation r e s ts w ith sharp d is c o n fo rm ity on
th e W e lls .
Richards and M a n s fie ld (191.2, p. 692) noted in t h is same
reg io n th e absence o f th e Grandeur Member and the presence o f a basal
b re c c ia .
This e ro s io n a l h ia tu s in creases in magnitude from th e study
area to the Big Horn Basin o f c e n tr a l Wyoming where as much as 130
f e e t o f Tensleep Sandstone may have been eroded (A g a ts to n , 1 9 5 4 ).
C o rr e la tio n s .
Formation nom enclature.
A severe problem has e x is te d w ith Phosphoria
A discu s sio n o f the problem is beyond the
scope o f t h is paper but an e x c e lle n t d e s c r ip tio n is provided by
McKelvey e t al_. (1 9 5 9 ) and Sheldon (1 9 5 7 ) and a s o lu tio n and j u s t i f i ­
c a tio n a re presented by McKelvey (1 9 5 9 ).
The problem arose because
o f th e in te rto n g u in g o f members and tongues o f th e P hosphoria, Park
C it y , and Shedhorn fo rm a tio n s , and th e Tensing n atu re o f some o f the
beds.
These s t r a t a in c lu d e , from base to to p , the low er c h e r t , Meade
28
Peak Phosphatic S h a le , Rex C h a rt, R e tc r t Phosphatic S h a le , and Tosi
C hert members o f th e Fhosphoria Form ation.
The G randeur, Franson,
and Ervay members make up th e Park C ity Form ation from base to to p ,
and the Shedhorn Sandstone c o n s is ts o f the low er and upper members.
The nom enclature and in te rto n g u in g r e la tio n s h ip s a re summarized in
Figures 6 and 7.
F o llo w ing th e precedent s e t by U.S. G eological Survey g eo lo ­
g is t s , the Phosphoria Form ation was d iv id e d in to low er and upper u n its
f o r purposes o f mapping in th e Pine Creek Quadrangle.
The low er u n it
c o n s is ts o f the Meade Peak Member, and th e upper u n it in clu d es the
Rex C h ert Member, R e to rt Phosphatic Shale Member, the low er tongue
o f the Shedhorn Sandstone, and th e Franson Tongue o f the Park C ity
Form ation.
A ll o th e r members were n o t p rese n t in th e map a re a .
L ith o lo g y .
The low er Phosphoria in th e Pine Creek Quadrangle
c o n s is ts o f 60 f e e t o f d a rk -g re y to dark-brown pho sphorite and mud­
stone w ith a few t h in in te rb e d s o f b la c k , a rg illa c e o u s d o lo m ite .
The
pho sphorite occurs as o o l it e s , p i s o l i t e s , p e l l e t s , and as dense
s tr u c tu r e le s s typ es.
The low er Phosphoria does not c o n ta in any
r e s is t a n t rocks and forms a lo w , densely veg etated swale t h a t is
u n d e rla in by b la c k s o i l .
The upper Phosphoria is 150 f e e t th ic k and
in cludes d ark -b ro w n is h -g re y mudstone, s h a le , and s ilt s t o n e w ith i n t e r bedded pho sphorite o f the R e to rt Phosphatic Shale Member, f r i a b l e ,
y e llo w -b ro w n , f in e - g r a in e d , q u a rtzo se sandstone o f th e low er tongue
I
Yellowstone and
Teton Parks, Wyo
2
Southern Teton
Range. W yo.
3
Big Hole Range
Idaho
6
Hoback Range,
Wyo
5
Snake River
Range, W yo.
4
C aribou Range.
7
W yom ing Range.
W yo.
8
Gros Ventre
Range. Wyo
9
Eastern W ind River
Range. Wyo.
10
Owl Creek
Range. Wyo
11
I anticline, W yom ing
Dinwoody form ation of T nassic age
IiU
Quadrant quartzite
or Tensleep sand­
stone, both of
Pennsylvanian age
(u p p e r beds)
E
23
Phosphona form ation
o f Perm ian age
Fig u re 6.
P ark C ity form ation
o f Perm ian age
(G randeur m em ber locally
m ay include beds o f
P ennsylvanian age)
X
P
L
A
Shedhorn sandstone
o f Perm ian age
N
A T I
Facies change
O N
m
Erosion surface
Nomenclature and in te rto n g u in g re la tio n s h ip s o f rocks o f Permian age o f
western Wyoming and sou theastern Idaho.
R efer to Figure 7 f o r index map
(Sheldon, 1963).
30
Figure 7
Index map fo r Fig u re 6.
Symbols and p a tte rn s same as f o r
Figure 6 (S heldon, 1 96 3).
Pine Creek Quadrangle o u tlin e d .
31
o f th e Shedhorn Sandstone, grey-brow n, massive d o lo m ite o f th e Franson
Tongue, and yellow -brow n to y e llo w , bedded c h e rt o f th e Rex C hert
Member.
The upper u n i t o f th e Phosphoria is o n ly s l i g h t l y more
r e s is t a n t than th e low er u n it .
The Phosphoria Form ation and ass o ciate d rocks o f Phosphoria
age show a w ide l it h o l o g i c v a r ia t io n .
G e n e ra lly the dominant fa c ie s
in southw estern Id ah o , w estern Wyoming, southwestern Montana, and
northw estern Utah in clu d es dark s h a le -,-p h o s p h o rite , and c h e r t ; in
northw estern Wyoming, sandstone; in w e s t-c e n tra l and n o rth e rn U tah,
carb o n ate; and in c e n tra l and e a s te rn Wyoming, lig h t - c o lo r e d g reen ish
and reddish s h a le .
These fa c ie s i n t e r f i n g e r , and tongues o f each
fa c ie s type extend long d is ta n c e s in to areas dominated by o th e r types
(Sheldon, 1 9 5 3 ).
In a d d itio n to these g e n e ra liz e d fa c ie s ty p e s ,
Sheldon (1 9 6 3 , p. 74) noted an in te r e s tin g r e la tio n s h ip between c h e rt
and a p a t it e .
R e g io n a lly , the d is t r ib u t io n o f a p a t it e and c h e rt
increases to th e w e s t, but where a p a t it e is l o c a l ly c o n c e n tra te d ,
c h e rt is im poverished.
C hert and d ark mud have a s im ila r in v e rs e
r e la tio n s h ip but c h e rt extends f a r t h e r e a s t than e it h e r dark mud o r
a p a t it e and th e q u a n tity o f dark mud is g r e a te s t in so u th eastern
Idaho.
Environment o f D e p o s itio n .
The environm ent o f d e p o s itio n o f
the Phosphoria Form ation and as s o c ia te d Permian rocks in th e study
area was extrem ely v a rie d b u t, in g e n e r a l, was open m arine w ith the
32
deepest p a rts in e a s t-c e n tr a l Idaho and a d ja c e n t p a rts o f Montana
and Utah (MeKelvey e t a j_ ., 1 95 9).
S hoaling o f th e sea f lo o r increased
to the e as t w ith th e e a s te rn m argin represented by r e s t r ic t e d shallow
basins.
Due to te c to n ic movements, th e above-described fa c ie s tra n s ­
gressed and regressed across w estern Wyoming two tim e s , and minor
flu c tu a tio n s o f c lim a t ic and oceanographic c o n d itio n s produced the
i n t r i c a t e in te rb e d d in g (McKelvey e t a l_ ., 1 9 5 9 ).
Mesozoic Rocks
In tro d u c tio n
The Mesozoic s e c tio n in th e map a re a , in excess o f 10,000
f e e t t h ic k , in c lu d es s i I t s t o n e , sandstone, and lim esto n e o f the
T r ia s s ic Dinwoody, Woodside, Thaynes and Ankareh fo rm a tio n s ; the
T r ia s s ic (? ) - J u ra s s ic (? ) Nugget Sandstone; and lim esto n e o f the
J u ra s s ic Twin C reek, P reu ss, and Stump fo rm a tio n s ; and th e s h a le and
sandstone o f th e Cretaceous G annett Group and Bear R iv e r and Aspen
form ations ( F ig . 5 ) .
These Mesozoic rocks cover th e m ajor p o rtio n
o f the P ine Creek Quadrangle from th e fla n k o f Grayback Ridge to the
Absaroka t h r u s t , w est o f th e border o f th e map.
T r ia s s ic S tr a ta — Previous Work
S tr a ta o f T r ia s s ic age in c lu d e , in ascending o r d e r , th e
Dinwoody, Woodside, Thaynes, and Ankareh fo rm a tio n s ( F ig . 8 ) .
ankareh
FORMATION
MONTANA
WYOMING
V E R T IC A L SCALE
FEET
CO
CO
V
2 0 0 0 -1
in e c r e e k q u a d .
SWIFT CREEI
SHEEP"
CREEK
IS O O -
LANOER
*NORTH MNEY
CREEK
IO O O -
UTAH
M IL E S
h o r izo n t a l
F ig u re
W est-east c ro s s -s e c tio n showing s t r a tig r a p h ic re la tio n s h ip s f o r the T r ia s s ic
o f w estern Wyoming and sou theastern Idaho.
Note In te rto n g u in g r e la t io n ­
ships and onlap o f Dinwoody over Phosphoria and Thaynes over Woodside ( a f t e r
Kummel, 1954, 1 9 5 5 ).
34
P revio u r work on these fo rm a tio n s has co n sisted o f re g io n a l
s t r a tig r a p h ic s tu d ie s covering w estern Wyoming and a d ja c e n t areas o f
Idaho.
Newell and Kummel (1 9 4 2 ) con cen trated on Lower T r ia s s ic s t r a t a
o f th e th r u s t b e l t re g io n and M a n s fie ld (1 9 2 0 ) and Kuwimel (1 9 5 4 )
re p o rte d on th e T r ia s s ic s e c tio n throughout the o v e rth ru s t b e l t and
a d ja c e n t p a rts o f so u th e astern Idaho.
on the Thaynes Form ation and i t s
P icard jr t al_* (1 9 5 9 ) re p o rte d
e q u iv a le n ts , from extreme e a s te rn
Idaho to w e s t-c e n tra l Wyoming, and High and P icard (1 9 6 9 ) examined
th e Ankareh and i t s
l i t h o l o g i c and tem poral e q u iv a le n ts a t H u n g e r
M ountain, 6 m ile s n o rth o f th e study a r e a , and a t o th e r l o c a l i t i e s
in c e n tra l Wyoming.
Newell and KuiTimel (1942 ) measured a p a r t i a l
s e c tio n o f T r ia s s ic s t r a t a w ith in th e map area j u s t to th e n o rth and
e a s t o f the B a ile y Creek la n d s lid e along th e w est f la n k o f Grayback
Ridge.
Wanless e t al_. (1 9 5 5 ) measured T r ia s s ic s e c tio n s a t Hunger
M ountain, Red Pass, 4% m ile s n o rth o f the map a r e a , and a t Hoback
Canyon. .
Di nwoo dy Fe m a t I on
Age and C o n ta c ts .
The E a rly T r ia s s ic (O to c e ra ta n to
Flem ingtan) age o f th e Dinwoody Form ation has been w e ll documented
by fau n al evidence ( Kummel, 1 9 5 4 ).
The c o n ta c t w ith th e u n d e rly in g
Phosphoria Formation appears in some places to be conform able and
in o th ers d isco n fo rm ab le.
In so u th eastern Id ah o , th e c o n ta c t w ith
35
th e Phosphoria is n o t w e ll exposed but where i t i s , i t appears to be
g ra d a tio n a l
( Kummel, 1 9 5 4 ).
Although the c o n ta c t w ith th e Phosphoria
was obscured in th e study a r e a , Wanless e t aj_. (1 9 5 5 , p. 41) mentioned
th e presence o f a basal conglom erate a few inches th ic k " a t many
places" in th e area a d ja c e n t to the Pine Creek Quadrangle.
Love
(1 9 3 9 , 1948) als o noted evidence o f a lo c a l unconform ity between the
Phosphoria and Dinwoody fo rm ations in th is general a re a .
In w estern
Wyoming, Newell and Kummel (1 9 4 2 , p. 938 -9 39) o u tlin e d evidence f o r
an unconform ity a t th e base o f th e Dinwoody as ( I ) marked le a c h in g
o f c h e rt beds a t th e top o f th e Phcsphoria Form atio n, ( 2 ) marked
northeastw ard o v e rla p o f lo w er Dinwoody s t r a t a by upper Dinwoody on
the Phosphoria s u rfa c e from southw estern Wyoming in to c e n tr a l
Wyoming, and (3 ) d is c o v e ry by A lfre d F is c h e r (personal communication
in Newell and Kummel, 1942) t h a t upper beds o f the Phosphoria are
lo c a l ly tru n c a te d by basal beds o f th e Dinwoody Form ation.
In
n o rth ern U tah , j u s t e a s t o f Provo, th e re is s tro n g e r evidence o f an
unconform ity where th e Woodside re s ts disconform ably on the
Phosphoria .
South, in c e n tra l U ta h , th e re is als o evidence o f an
e ro s io n a l d is co n fo rm ity between th e Permian Kaibab Limestone and
o v e rly in g T r ia s s ic Moenkopi Form ation (N ew ell and Kummel, 1942,
p. 9 3 8 ).
These r e la tio n s h ip s in d ic a te a re g io n a l unconform ity
between th e T r ia s s ic and Permian t h a t probably in crease s in magnitude
between th e study area and n o rth e rn U tah.
However, O rie l
( i n McKee
36
e t a l_ ., 1959, p. 3 - 4 ) o ffe re d an a lt e r n a t iv e hypothesis and suggested
th a t the c o n ta c t between the Phosphoria and Dinwoody could be
ex p la in e d by re g re s s iv e o v e rla p .
I f t h is is t r u e , then l i t t l e , i f
any, tim e elapsed between d e p o s itio n o f these u n it s .
Continuous
d e p o s itio n is a ls o suggested by a crude s i m i l a r i t y o f th e fa c ie s
p a tte rn s between Dinwoody and Phosphoria rocks produced by re g re s s iv e
o v e rla p (S heldon, 1 9 6 3 ).
The problem remains unresolved and f u r t h e r
s tu d ie s on th e n a tu re o f t h is c o n ta c t in th e n o rth ern p a r t o f the
o v e rth ru s t b e l t a re needed.
C o rr e la tio n s .
The Dinwoody Formation was named by B lackw elder
(1918 ) f o r exposures in Dinwoody Canyon in th e Wind R iv e r Range.
Dinwoody nom enclature is used throughout th e t h r u s t b e l t , so u th eastern
Idaho, extreme southw estern Montana, and c e n tra l Wyoming.
L ith o lo g y .
In th e map a r e a , th e Dinwoody F o rm atio n, roughly
600 f e e t t h ic k , c o n s is ts o f v e ry l ig h t - g r e y , v e ry f in e -g r a in e d ,
calcareous sandstone in the lo w er p a r t .
The upper p a r t in c lu d e s g re y ,
s ilic e o u s s i lt s t o n e , and o ccasional beds o f b lu is h -g r e y , lith o g r a p h ic
lim e s to n e .
The s ilt s t o n e and sandstone beds a re very t h in ly bedded
and r e s is t a n t , form ing d i s t i n c t i v e t a lu s .
S h a le , which is common in
th e m iddle p a r t o f th e Dinwoody in th e area a d ja c e n t to th e Pine
Creek Quadrangle (see Wanless e t a L , 1 9 5 5 ), was n o t encountered in
the f i e l d a r e a , probably due to th e e x te n s iv e ta lu s cover from the
o v e rly in g p a r t o f th e Dinwoody.
37
R e g io n a lly , th e l it h o l o g i c v a r ia t io n in th e Dinwoody is not
s ig n if ic a n t .
Newell and Kuraiel (1 9 4 2 , p. 941) subdivided th e Dinwoody
in to th re e m a jo r, l i t h o l o g i c a l l y d i s t i n c t u n its which a re f a i r l y
e x te n s iv e .
The low est
u n it,
th e basal s i l t s t o n e , c o n sis ts o f
f r i a b l e , u n f o s s ilif e r o u s , b u f f s i lt s t o n e .
This sequence has not been
observed in southw estern Id ah o ; th e fa c ie s e q u iv a le n t th e re is re p re ­
sented by a b u ff s i l t y s h a le .
The m edial u n it is th e L in g u la zone
which co n sis ts predo m inan tly o f s i l t y , o l iv e - b u f f to grey s h a le i n t e r c a la te d w ith t h i n , blocky lim e s to n e , ranging from d a r k -b lu is h -g r e y
to brown.
L in g u la .
These s t r a t a a re c h a ra c te riz e d by p rofuse w e ll-p re s e rv e d
The upper u n i t , the C la r a ia zone, th e most e x te n s iv e
sequence, is t y p i f i e d by lo c a l ly abundant molds o f the pelecypod
C la r a ia .
L i t h o lo g ic a ll y , i t c o n s is ts o f r e s i s t a n t , lig h t-b r o w n ,
calcareous s ilt s t o n e beds le s s than one fo o t t h ic k .
This u n it a ls o
con tains l o c a l , in te rb e d d e d , l ig h t - g r e y , s i l t y lim esto n e and is
d if f e r e n t ia t e d from the m edial zone b} th e sm all amount o f s h a le .
These s t r a t a a re d ep osited in an onlap r e la t io n as i l l u s t r a t e d
F ig u re 8 .
in
In the southern Wind R iv e r M ountains, th e upper C la r a ia
zone re s ts d i r e c t l y on th e Phosphoria Form ation (N ew ell and Kummel,
1 94 2).
Environment o f D e p o s itio n .
During th e e a r ly T r ia s s ic , a
tra n s g re s s io n o f th e sea re s u lte d in open m arine c o n d itio n s in south­
eas te rn Idaho and w estern Wyoming.
W ater depth was g r e a te s t in
38
so u theastern Idaho where s h a le was d e p o s ite d .
Kost o f w estern Wyoming
was a broad s h e lf w ith sh allo w w a te r, a w e ll-a e r a te d s e a - f lo o r , and
a c tiv e bottom c u rre n ts ( Kummel, 1 95 5).
Woodside Formation
Age and C o ntacts.
o f fo s s ils , i t
Although th e Woodside Formation is b arren
is considered to be o f E a rly T r ia s s ic ag e, based on
i t s s t r a t ig r a p h ic r e la tio n s h ip w ith the o v e rly in g E a rly T r ia s s ic
Thaynes Form ation.
F u rtherm ore, in so u th eastern Id ah o , th e low er
h a l f o f th e Woodside is th e tim e e q u iv a le n t o f th e Lower T r ia s s ic
Dinwoody Form ation ( F ig . 9 ) on th e b as is o f th e in te rto n g u in g
r e la tio n s h ip s o f th e u n its
( NewelI and Kummel, 1 9 4 2 ).
A zone o f
in te rto n g u in g o f th e Dinwoody and Woodside fo llo w s a l in e from south­
w estern Montana along th e Idaho-Wyoming border t h a t tu rn s a b ru p tly
westward in n o rth e rn U tah.
Red beds a re predom inant e a s t o f t h is
l i n e , and su b o rd in a te to th e w est ( Kummel, 1 9 5 5 ).
The n a tu re o f th e
co n tac t o f th e Woodside and Dinwoody fo rm atio n s w ith in th e f i e l d area
is in d e te rm in a b le because o f ta lu s cover.
Cor r e l a t i o n s .
The Woodside Form ation was named by Boutw ell
(1907 ) f o r s t r a t a exposed in Woodside Canyon near Park C i t y , Utah.
Woodside term in o lo g y is u t i l i z e d throughout th e t h r u s t b e l t , n o rth e rn
U tah, and so u th eastern Idaho because th e Woodside r e ta in s i t s
lo g ic i n t e g r i t y over t h is a r e a .
lith o ­
E ast o f th e th r u s t b e l t in c e n tr a l
39
Spanish
Fork
Scotls
Drow
CO
Scale
1500
CREEK
"
QUADRANGLE
P IN E
-
Bear Creek
Dry Ridge
IDAHO
iooo -
Hot Spring!
WYOMING
UTAH
500
Red beds
Pork City
fs c o lt Draw
!Spanish Fork
Figure 9.
C o rr e la tio n diagram o f Dinwoody and Woodside form ations
showing in te rto n g u in g r e la tio n s h ip s between Provo, Utah
and Henry, Idaho and the r e s u lta n t tim e eq u ivalen cy o f
th e low er p a rt o f these u n its ( Kummel, 1 95 3).
-
40
Wyoming, th e Woodside i s p a r t ly te m p o ra lly e q u iv a le n t to th e Red Peak
Formation (F ig .
10) o f the Chugwater Group (P ic a r d , e t a l_ ., 1 9 5 9 ).
L ith o lo g y .
In th e map a r e a , th e Woodside Form ation c o n sis ts
o f 640 f e e t o f red-brow n, v e ry f in e -g r a in e d , sandy s i lts to n e and
s h a le .
These lit h o lo g ie s a re g e n e r a lly very p o o rly exposed but th e
fo rm a tio n is e a s ily mapped on th e basis o f the red c o lo r o f th e s o i l .
Throughout i t s area o f exposure, the Woodside shows n e g lig ib le
v a r ia t io n in lit h o lo g y .
Newell and Kummel (1 9 4 2 ) re p o rte d th e p res­
ence o f a few t h in beds C f lim esto n e in Woodside s e c tio n s in the
Hoback and Gros V entre ranges and Kumtnel (1 9 5 4 , p. 171) mentioned
a few t h in non-red beds in th e S a lt R iv e r Range.
In n o rth ern Utah
and in th e U in ta and Wasatch ran g e s, th e Woodside c o n s is ts almost
e n t i r e ly o f red beds; o n ly a few t h in non-red beds a re p rese n t
( Kummel, 1 9 5 4 ).
I t is ex tre m e ly probable t h a t these non-red
lit h o lo g ie s re p re s e n t a tongue o f th e u n d e rly in g m arine Dinwoody.
P icard e t al_.
(1 9 6 9 , p. 2278) sp ecu lated th a t th e Woodside a t the
Hunger Mountain s e c tio n is probably c o r r e la t iv e w ith p a r t o f the
low er p la t y fa c ie s and u n d e rly in g s i l t y c la y s to n e fa c ie s o f the Red
Peak Form ation o f w e s t-c e n tr a l Wyoming (F ig .
Environment o f D e p o s itio n .
1 0 ).
The environm ent o f d e p o s itio n o f
the Woodside was c o n tin e n ta l on w estward- and n o rth w ard -p ro g rad in g
d e lta s and c o a s ta l p la in s .
The presence o f occasional beds o f m arine
WESTERN WYOMING
WEST-CENTRAL WYOMING
NUGGET
NUGGET
SANDSTONE
SANDSTONE
Garb.
C a rb .
O cher
U n it
O cher
U n it
P u r p le
U n it
P u r p le
U n it
Low er
C a rb .
U n it
Lower
C a rb .
U n it
"J E L M "
EQUIVALENT
JELM
FORMATION
CROW
MOUNTAIN
FM.
S a n d s to n e
and
L im e s to n e
A lc o v a
Ls.
M b r.
V a r ie g a te d
Sandy
F a c ie s
U p p e r B la c k
L im e s to n e
Tan S i l t y
L im e s to n e
Lower
L im e s to n e
WOODSI DE
FM.
F a c ie s
A lte r n a tin g
F a c ie s
Lower
P la ty
F a c ie s
S ilt y
C la y s t o n e
F a c ie s
DINWOODY
FM.
Figure 10.
Nomenclature and s t r a tig r a p h ic c o r r e la tio n s o f M iddle
and Upper T r ia s s ic fo rm a tio n s in western and w e s t-c e n tra l
Wyoming ( a f t e r P icard e t a l . , 1969, and High and P ic a rd ,
196 9).
42
lim estone suggest t h a t te c to n ic o s c illa t io n s allow ed th e Dinwoody sea
to p e r io d ic a lly invade t h is broad c o a s ta l p la in - d e lt a complex.
Thaynes Formation
Age and C o n ta cts.
The Thaynes Formation is considered to be
E a rly T r ia s s ic in age according to Kumrnel (1 9 5 4 , 1955) on th e basis
o f f o s s il d a ta .
D ating o f t h is u n it is made more d i f f i c u l t by th e
in te rto n g u in g r e la tio n s h ip w ith the o v e rly in g Ankareh and th e under­
ly in g Woodside fo rm a tio n s .
A fa c ie s d iv id in g l i n e , s im ila r to th a t
o f the Woodside, e x is ts f o r th e Thaynes Form ation, and passes south­
ward from th e Idaho-Wyoming boundary through th e Wasatch Mountains o f
Utah.
East o f t h is l i n e , red beds a re common, and to th e w e s t, red
beds a re absent o r o f m inor im portance ( Kummel, 1 9 5 5 ).
Com plications
o f t h is p a tte rn a re c re a te d by an eastw ard -exten d in g m arine tongue o f
the Thaynes, th e Alcova Lim estone, which a t v ario u s tim es has been
c o r r e la te d w ith many p a rts o f th e Thayr.es and post-Thaynes rocks but
is now considered by P icard e t al_. (1 9 6 9 ) to be an upper tongue o f
the Thaynes.
To th e w e s t, th e Lanes Tongue o f the o v e rly in g Ankareh
Formation extends in to the upper Thaynes but is not p rese n t as f a r
west as F o rt H a l l , Idaho ( F ig . 8 )
( Kummel, 1954, 1 9 5 5 ).
This tongue
may be rep resen ted in the map area by th e red -b ro w n , very f i n e ­
g rain ed sandstone t h a t occurs n ear th e m iddle to upper p a r t o f the
Thaynes.
43
The Thaynes is in an onlap r e la tio n s h ip w ith th e Woodside
on the e a s t.
T his p a tte r n is co m p lic a te d , however, by in te rto n g u in g
r e la tio n s h ip s and the s t r a tig r a p h ic p o s itio n o f th e eastward extending
Alcova Lim estone.
These r e la tio n s h ip s a re i l l u s t r a t e d
in F ig u re 3.
This co n ta c t was obscured in the study a re a .
C o rr e la tio n s .
Boutw ell
(1 9 0 7 ) named th e Thaynes f o r exposures
in Thaynes Canyon, near Park C it y , Utah.
C o rre la tio n s based on
s t r a tig r a p h ic p o s itio n o f th e Thaynes Formation w ith e q u iv a le n ts in
surrounding regions is made more d i f f i c u l t by in te rto n g u in g and fa c ie s
changes.
M a n s fie ld (1 9 1 6 ) r a is e d th e Thaynes Form ation to Group rank
and design ated th re e fo rm a tio n s , in ascending o r d e r , the Ross Fork
Lim estone, th e F o rt H a ll F o rm atio n, and th e P o rtn e u f Lim estone.
The
la c k o f p e r s istance o f these fo rm a tio n s , however, re s u lte d in the
abandonment o f M a n s fie ld 's scheme, although the name P o rtn e u f Lime­
stone was given member s ta tu s by Kummel (1 9 5 4 , p. 172) because i t
more p e r s is te n t than th e o th e r two u n it s .
is
Kummel (1 9 5 4 , p. 172)
a ls o included th e Tim othy sandstone member in the upper Thaynes in
sou theastern Idaho ( F ig . 8 ) .
East o f the th r u s t b e l t in c e n tr a l
Wyoming, the Thaynes is the p a r t i a l tem poral e q u iv a le n t o f th e Red
Peak and Crow Mountain fo rm a tio n s (F ig .
(P ic a rd evt j L L , 1 9 6 9 ).
10) o f th e Chugwater Group
The Alcova Limestone in t h is re g io n is a ls o
c o r r e la te d w ith the upper Thaynes.
44
L ith o lo g y .
In th e Pine Creek Q uadrangle, the Thaynes Forma­
tio n co n sis ts o f a low er u n it o f in te rb e d d e d , m edium -grey, mediumbedded, lim estone and very f in e - g r a in e d , v e ry t h in ly bedded sandstone;
a m edial u n it o f red -b ro w n , v e ry fin e -g r a in e d sandstone; and an upper
u n it o f g re y , v e ry t h i n l y bedded lith o g r a p h ic lim e s to n e , and y e llo w ta n , very f in e - g r a in e d , calcareous sandstone.
In a d d it io n , a 4 fo o t
th ic k basal b re c c ia u n it occurs in the Thaynes Form ation a p p ro xim ately
o n e -h a lf m ile south o f th e B a ile y Creek la n d s lid e .
H ere, th e a n g u la r
and o c c a s io n a lly subrounded c la s t s , up to 3 k inches
in d ia m e te r, a re
imbedded in a s i l t y , calcare o u s m a trix .
north o f t h is l o c a l i t y .
This u n it was not observed
The Thaynes Form ation is a p p ro xim ately 950
f e e t th ic k in th e Pine Creek Q uadrangle, though poor exposure o f the
upper c o n ta c t w ith the Ankareh made acc u rate measurements im p o ssib le .
In th e re g io n a d ja c e n t to th e map a r e a , the Thaynes Formation
does not show s ig n i f i c a n t l it h o l o g i c v a r i a t i o n . . Kummel (1 9 5 4 , p. 173)
proposed t h a t th e Thaynes Form ation in sou th eastern Idaho be sub­
d iv id e d in to seven l i t h o l o g i c u n its which a r e , in ascending o rd e r:
(I)
low er lim e s to n e , ( 2 ) low er b la c k lim e s to n e , ( 3 ) tan s i l t y
lim e ­
s to n e , (4 ) upper b lack lim e s to n e , ( 5 ) sandstone and lim e s to n e ,
(6 ) the P o rtn e u f Lim estone, and ( 7 ) th e Timothy Sandstone Member.
P ic a rd ,
al_. (1 9 6 9 , p. 228 0-2281) suggested th a t Kummel1s l it h o l o g i c
d iv is io n s , w ith th e ex c e p tio n o f th e P o rtn e u f Lim estone, can be
45
c o rr e la te d between so u th eastern Idaho and w estern Wyoming, based on
lit h o l o g i c s i m i l a r i t y , th ic kn ess changes, and in te r p r e te d f a c ie s .
Environment o f D e p o s itio n .
A second advance o f the E a rly
T r ia s s ic sea re s u lte d in d e p o s itio n o f the Thaynes Form ation in
.
w estern Wyoming and th e in t e r f in g e r in g o f th ese m arine d ep o s its w ith
c o n tin e n ta l rocks along th e m argins o f the sea.
Due to th e abundance
o f d o lo m ite and gypsum in the Hcback and Hunger Mountain s e c tio n s ,
Picard e t al_.
(1969) proposed t h a t th e Thaynes in t h is area was
d ep osited in a s h a llo w -w a te r m arine environm ent t h a t was r e s t r ic t e d
by carbonate banks in e a s te rn Idaho.
The basal b re c c ia u n i t in th e Thaynes in th e mao a re a may
have re s u lte d from a lo c a l s h o a lin g , suggesting a d is c o n fo rm ity
between t h is u n it and th e u n d e rly in g Woodsid e .
I f t h is shoal were
exposed f o r a s u f f i c i e n t p e rio d o f tim e , d e s ic c a tio n o f th e Woodside
sediments would have o cc u rre d .
Coarse c la s t s , removed by s u b a e ria l
e ro s io n , would have been tra n s p o rte d s h o rt d is ta n c e s and d ep osited
in th e surrounding b a s in .
Ankareh Formation
Age and C o ntacts.
The age o f th e Ankareh Form ation is
q u e s tio n a b le because no d ia g n o s tic f o s s ils have been found b u t i t
is
considered to be o f M id d le o r L a te T r ia s s ic age by Kummel (1 9 5 4 ),
based on i t s s t r a t ig r a p h ic p o s itio n .
In c e n tra l Wyoming, th e p a r t ly
46
te m p o ra lly e q u iv a le n t Grow Mountain and Jelm fo rm a tio n s a re separated
by a pronounced d is c o n fo rm ity according to High and P icard (1 9 6 3 ,
p. 1 0 9 5 ).
They suggested t h a t t h is M idd le T r ia s s ic h ia tu s can be
c o r r e la te d w ith a s im ila r d is c o n fo rm ity in n o rth e a s te rn Utah t h a t
sep arates the T r ia s s ic Moenkopi and G arta fo rm a tio n s .
Furtherm ore,
th e Timothy Sandstone is u n co n fo m ab ly o v e r la in by the Higham G r i t ,
suggesting t h a t t h is h ia tu s is p rese n t in so u th eastern Idaho ( Kummel,
1 95 4).
No evidence o f an unconform ity was noted between the Ankareh
and Thaynes in th e study a r e a , b u t based on th e d iscon form able
r e la tio n s h ip s in th e surrounding re g io n , i t
.
is probable t h a t th e
c o n ta c t between these two fo rm a tio n s is not conform able.
C o r r e la tio n s .
The Ankareh Formation was named by Boutw ell
(1907 ) f o r s t r a t a exposed near Park C it y , Utah.
He o r i g i n a l l y
included an o v e r ly in g , prom inent w h ite sandstone, th e Nugget, but
l a t e r (1 9 1 2 ) r e s t r ic t e d th e name Ankareh to in c lu d e a l l s t r a ta o v e rly in g th e Thaynes and u n d e rly in g th e Nugget.
In southw estern Id ah o ,
M a n s fie ld (1 9 2 7 ) recognized the fo llo w in g post-Thaynes T r ia s s ic rocks:
Timothy Sandstone, Higham G r i t , Deadman Lim estone, and Wood S h a le , in
ascending o rd e r ( F ig . 8 ) .
To avo id
c o n fu s io n , Kummel (1 9 5 4 , p. 179)
proposed reducing a l l p re v io u s ly named post-Thaynes s t r a t a in n o rth e rn
Utah and w estern Wyoming" to member rank and using th e name Ankareh
f o r these ro cks.
In a d d it io n , he assigned th e Timothy Sandstone to
th e uppermost p a r t o f th e Thaynes, designated th e Higham G r i t and
47
Dcadman Limestone as independent fo rm a tio n s , and considered the Wood
Shale to be a w estern extend ing tongue o f th e Ankareh (F ig . 8 ) .
East
o f th e th r u s t b e l t in c e n tra l Wyoming, the Ankareh is th e temporal
e q u iv a le n t to th e Popo Agie and u n d e rly in g Jelm fo rm atio n s (F ig .
10)
o f the Chugwater Group (H igh and P ic a rd , 1 9 5 9 ).
L ith o lo g y .
The Ankareh is g e n e ra lly very p o o rly exposed
w ith in th e map a r e a , concealed beneath a ta lu s cover from th e o v e rly in g Nugget.
At th e b e s t exposure on the n o rth e rn m argin o f the
B a ile y Creek la n d s lid e , i t c o n s is ts o f a lo w e r u n it o f red -b ro w n ,
very f in e -g r a in e d sandstone and an o v e rly in g u n it o f maroon s i l t s to n e , both o f which w eather to a red s o i l .
G rey, round, w e ll
d e fin e d , calcareous nodules and a fe w , t h i n , g re y , m edium -grained
lim estone beds occur in the upper s i lts to n e u n it a t th e mouth o f
Cabin Creek along th e northw estern border o f th e map area and f a r t h e r
north a t Munger M ountain.
W ith in th e map a r e a , the Ankareh Forma­
t io n is estim ated to be 350-400 f e e t t h ic k , although a c c u ra te measure­
ments were d i f f i c u l t to o b ta in because o f th e poor exposure.
R e g io n a lly , th e Ankareh shows s e v eral s ig n i f i c a n t l it h o l o g i c
changes.
In c e n tr a l and w e s t-c e n tra l Wyoming, th e Jelm Formation
co n sists o f a r g illa c e o u s lim e s to n e , carbonate-cem ented sandstone,
and red s i l t s tone and sandstone (H igh and P ic a r d , 1 9 6 9 ).
A t Munger
M ountain, north o f th e map a r e a , th e low er p a r t o f th e Ankareh
in cludes a tongue o f th e Jelm which c o n s is ts o f r e d , p i a ty s i lts t o n e .
48
The m iddle beds here c o n s is t o f th e low er carbonate u n it o f ih o Popo
Agie Formation w h ic h , according tc High and P ic a rd (1 9 6 9 , p. 1 3 9 6 ),
is l i t t l e
changed from the e a s te rn s e c tio n s o f c e n tr a l Wyoming.
The
upper Ankareh a t Hunger Mountain in clu d es lim esto n e and s i lt s t o n e ,
and pebbly conglom erate which is in te r p r e te d to be a fa c ie s change
in the ocher uni"t o f th e Popo Agie o f w e s t-c e n tra l Wyoming (High and
P ic a rd , 1 9 6 9 ).
F ig u re 10 summarizes these r e la tio n s h ip s .
Love (1 9 4 3 ,
p. 9 9 -1 0 0 ) described the Popo Agie Formation in th e area from e a s te rn
Jackson Hole to the Wind R iv e r Mountains as:
...o c h e r c o lo re d , o o l i t i c , s ilic e o u s ; d o lo m itic c la y s to n e ,
w ith lim estone p e l l e t conglom erate, p u rp le and red s h a le ,
and red s i l t y sandstone.
A widespread zone o f h ig h ly
s ilic e o u s , b r i g h t , o c h e r-c o lo re d d o lo m itic c la y s to n e con­
ta in in g numerous s ilic e o u s and lim y geodes and s ilic e o u s
o o lit e s in g re a t abundance is p re s e n t near th e top o f the
member.
T his lit h o lo g y is s im ila r to th e Ankareh in th e reg io n a d ja c e n t to
the map a re a .
The Deadman Limestone and Timothy Sandstone o f south­
e a s te rn Idaho a r e , according to Kurmiel (1 9 5 4 ), c o r r e la t iv e to s im ila r
sec tio n s o f Ankareh measured by Wanless e t al_. (1 9 5 5 ) in th e v i c i n i t y
o f the map a re a .
Environment o f D e p o s itio n .
The Ankareh Form ation records a
v a r ia b le and changing d e p o s itio n a l environm ent in so u th eastern Idaho
and w estern Wyoming.
West o f th e b a s in , in c e n tr a l
Id ah o , a n o rth eas t­
tre n d in g rid g e rose in e a r ly L ate T r ia s s ic tim e , shedding coarse
d e tr itu s eastward to form the Higham G r i t (McKee e t a l_ ., 1959, p. 1 7 ).
49
This event transform ed th e shallow m arine and para l i e c o n d itio n s th a t
p re v a ile d in w estern Wyoming d u rin g d e p o s itio n o f th e low er Ankareh
to f l u v i a l and la c u s tr in e environm ents dominant during d e p o s itio n c f
the upper Ankareh (High and P ic a r d , 1 96 9).
J u ra s s ic S tr a ta — Previous Work
J u ra s s ic s t r a t a exposed w it h in the study area in c lu d e the
Nugget Sandstone ( T r ia s s ic ? and J u ra s s ic ? ) , th e Twin Creek Lime­
s to n e , th e Preuss Sandstone, and th e Stump Sandstone ( F ig . 5 ) .
J u ra s s ic s t r a ta were examined by M a n s fie ld (1 9 2 0 ) in so u theastern
Idaho, by Im lay (1 9 5 0 ) in th e o v e rth ru s t b e l t , and by P ip irin g o s
(1 9 5 7 , 1968) in s o u th -c e n tra l Wyoming.
A d d it io n a lly , Dobrovolny
(1 9 4 1 ) s tu d ie d th e J u ra s s ic and Cretaceous sequence in th e Camp Davis
a r e a , 2 m iles n o rth e a s t o f th e map a re a .
Wanless
al_. (1955 )
measured J u ra s s ic s e c tio n s a t Cabin Creek on the n o rth e rn border o f
th e map a r e a , a t Hunger M ountain, and a t o th e r l o c a l i t i e s
Gros V e n tre , and Hoback ranges.
in the .T e to n ,
S ig n if ic a n t re g io n a l work th a t
in clu d ed th e study area was undertaken on the Twin Creek by Im lay
(1 9 5 3 , 1 9 6 7 ), on th e Preuss by Im lay (1 9 5 2 ), and on th e Preuss and
Stump in the area a d ja c e n t to th e Pine Creek Quadrangle by students
from th e U n iv e rs ity o f M ichigan (O re , 1975, personal com m unication).
50
Nugget Sandstone
Age and Co n ta c ts .
The tru e age o f th e Nugget Sandstone is
unknown due to the la c k o f d ia g n o s tic f o s s il eviden ce.
The o v e rly in g
Twin Creek Lir.estone was dated as M idd le J u ra s s ic and th e u n d e rly in g
Popo Agie Member o f the Chugwater Group was dated an Late T r ia s s ic
(S ta a tz and Al bee, 1 9 6 6 ), in d ic a tin g t h a t th e Nugget could be Late
T r ia s s ic , o r E a rly J u r a s s ic , o r both.
On the basis o f an in te rto n g u in g
r e la tio n s h ip w ith th e T r ia s s ic Pcpo Agie Member, Love (1 9 5 7 ) suggested
th a t the Nugget was T r ia s s ic .
However, High and P icard (1 9 6 5 ) demon­
s tr a te d t h a t th e Nugget was separated from th e Pcpo Agie by a
d is c o n fo rm ity .
Some w orkers ( P ip ir in g o s , 1968, O r ie l i_n McKee e t a l . ,
1959) concluded t h a t th e T r ia s s ic -J u r a s s ic boundary l i e s somewhere
w ith in th e Nugget.
High and P icard (1 9 6 9 ), however, p o s tu la te d a
Late T r ia s s ic and E a rly J u ra s s ic te c to n ic e ve n t in Wyoming t h a t
re s u lte d in th e fo ld in g and tru n c a tio n o f th e Popo A g ie .
They con­
cluded , t h e r e f o r e , t h a t the Nugget should be assigned a J u ra s s ic age
because o f the tim e in v o lved in th e fo ld in g and tru n c a tio n o f th e
Popo A g ie.
They extended t h is p o s tu la te d e ro s io n a l unconform ity to
w estern Wyoming to sep a ra te th e Ankareh and o v e rly in g Nugget.
However, no evidence o f t h is r e la tio n s h ip can be seen in the map a re a .
C o r r e la tio n s .
Veatch (1 9 0 7 ) named th e Nugget f o r s t r a ta
exposed in southw estern Wyoming and d e fin e d i t as in c lu d in g a low er
red-bed member and an upper lig h t - c o lo r e d sandstone member.
Gale
51
ar-d Richards (1 9 1 0 , p. 4 7 9 -4 8 0 )
l a t e r r e s t r ic t e d the name Nugget to
the upper sandstone member and in cluded the red-bed sequence in th e
Ankareh.
Because th e Nugget r e ta in s i t s l i t h o l o g i c c h a ra c te r in
s o u th -c e n tra l and w estern Wyoming, so u th eastern Idaho, and n o rth ­
e as te rn U tah, the name Nugget is used throughout t h is re g io n .
The
Nugget is th e p a r t ia l tem poral and l it h o l o g i c c o r r e la t iv e o f the
Navajo Sandstone o f c e n tr a l U ta h .(H a rs h b s rg e r, Repenning, and Ir w in ,
1 95 7).
L ith o lo g y .
The Nugget in the map area is a brow n-w eathering,
w h ite , p in k is h -o ra n g e , and l i g h t - t a n , m edium -grained, m assive,
q u a r t z i t i c sandstone.
It
is o c c a s io n a lly cross-bedded, and r ip p le
marks have been observed in the Nugget a d ja c e n t to the Pine Creek
Quadrangle (Wanless e t aJL, 1955, p. 4 7 -4 8 ).
I t is a prom inent rid g e
form er and produces a c o a rs e , d i s t i n c t i v e , brown t a lu s .
In th e map
a r e a , th e Nugget Sandstone is 550 f e e t th ic k where the most accu rate
measurement was ob tain ed along th e n o rth s id e o f th e B a ile y Creek
la n d s lid e .
This th ic kn ess is c o n s is te n t w ith Al b ee 's (1 9 6 8 ) measure­
ments in th e a d ja c e n t Hunger Mountain Q uadrangle.
Wanless e t al_.
(1955 ) measured a p p ro xim ately 275 f e e t o f Nugget a t Cabin Creek on
the north border o f th e map a r e a , suggesting t h a t t h is u n it th ic ken s
and th in s along i t s s t r i k e .
The Nugget in th e map area is l i t h o l o g i c a l l y s im ila r to th a t
found throughout i t s area o f exposure.
Wanless e t a l .
(1955)
52
in d ic a te d t h a t th e Nugget is w e ll cemented in th e Iioback and Snake
R fver ranges a n d .le s s t i g h t l y cemented in th e Gros V entre and Tetcn
ranges. . In the n o rth ern Snake R iv e r Range th e Nugget is very f i n e ­
grained and l o c a l l y calcareous (S ta a tz and A lb e e , 1 9 6 6 ).
In
s o u th -c e n tra l Wyoming th e Nugget is s o f t and f r i a b l e , and predomi­
n a n tly very f in e -g r a in e d
( P ip ir in g o s , 1 95 7).
Environment o f D e p o s itio n .
The environm ent o f d e p o s itio n o f
th e Nugget is q u e s tio n a b le and was e it h e r m arine o r e o lia n o r both.
The NuggetrNavajo sandstone body has been regarded by many (H arshbarger
e t a l_ ., 1557, S tokes, 1961) as a c la s s ic example o f an e o lia n ,
i n t e r io r - d e s e r t f a c ie s .
However, W righ t and Dickey (1963 ) suggested,
p r im a r ily on the basis o f in te rto n g u in g r e la tio n s h ip s c f th e Navajo
w ith the m arine Carmel Form atio n, t h a t p a r t o f the Navajo was
m arginal m arine.
M a rz o lf (1 9 6 9 ) a ls o concluded t h a t th e basal p o rtio n
o f the Navajo could be m arine o r m arginal m arine based on p rim ary
sedim entary s tr u c tu r e s .
S taaz and Albee (1 9 6 6 ) and P ip irin g o s (1 9 6 8 )
a ls o suggested th a t th e Nugget could be the product o f subaqueous
d e p o s itio n .
S ta n le y et^ al_. (1 9 7 1 , p. 13) concluded t h a t " e o lia n con­
d itio n s p re v a ile d w ith in a v a r ia b le b e l t o f c o a s ta l dunes a d ja c e n t
to a very shallow sea which g r a d u a lly tran sg ressed across the
c r a to n ic m arg in ."
T h e ir , re c o n s tru c tio n s a re g e n e ra liz e d and la r g e ly
conceptual but th e im p lic a tio n is t h a t p a r t o r a l l o f th e Nugget could
be m arine in o r ig in .
53
Twin Creek Limestone
Age and C o n tacts.
The Twin Creek Limestone is M id d le to Late
J u ra s s ic (E a r ly to L ate B ajo cian to E a rly C a llo v ia n ) in age based cn
f o s s il data ( Im la y , 1 9 6 7 ).
Although a n g u la r ity is r a r e ly seen
(P e te rs o n , 1 9 7 2 ), th e c o n ta c t w ith th e u n d e rly in g Nugget Sandstone
is a s i g n i f i c a n t re g io n a l d is c o n fo rm ity which has long been recognized
( e .g . M a n s fie ld , 1 9 2 0 ).
T h is sharp c o n ta c t, marked by a zone o f
leach in g in the l a s t few f e e t o f the Twin C reek, is w e ll exposed on
U.S. Highway 26-89 about I m ile south o f the mouth o f Cabin Creek a t
the n o rth border o f th e map a re a .
C o r r e la tio n s .
'
-
.
The Twin Creek was named by Veatch (1 9 0 7 ) f o r
s t r a t a exposed in southw estern Wyoming.
The name Twin Creek is used
throughout wester:*, Wyoming, s o u th e astern Id ah o , and n o rth -e a s te rn
Utah.
The Carmel Form ation and Tw elvem ile Canyon Member o f the
A rapien Form ation o f c e n tr a l and n o r th -c e n tr a l Utah a re th e p a r t ia l
temporal e q u iv a le n ts o f the Twin Creek.
East o f th e th r u s t b e l t , the
basal Twin Creek is known as th e Gypsum Spring Form ation and the o v e rly in g beds a re p a r t ly te m p o ra lly e q u iv a le n t to th e Lower Sundance
Form ation ( Im la y , 1 9 6 7 ).
L ith o lo g y .
W ith in th e map a r e a , th e Twin Creek Limestone is
g e n e r a lly p o o rly exposed.
The basal p a r t o f th e Twin Creek a t Cabin
Creek along U .S . Highway 2 6 -8 9 c o n s is ts o f b lu e -g r e y , t h i n l y bedded
lim esto n e and an o v e rly in g bed o f red s h a le .
P e c u lia r ly , th e re is
54
no basal lim estone b re c c ia as a t o th e r l o c a l i t i e s
reg io n (see Wanless et_ a l_ ., 1 9 5 5 ).
in the a d ja c e n t
The m edial and upper p a rts o f th e
Tw in Creek c o n s is t o f l ig h t - g r e y , t h i n l y bedded, s h a ly lim estone t h a t
breaks in to d i s t i n c t i v e " p e n c il"-s h a p e d fragm ents.
T his d e t r it u s
weathers to a lig h t - g r e y s o il devoid o f much v e g e ta tio n .
Interbedded
w ith th e s h a ly lim esto n e a re th re e o r more beds o f I e d g e-fo rm in g ,
g re y - to b lu e -g r e y , m assive- to t h ic k ly bedded, fin e -g r a in e d lim e ­
stone.
W ith in these fin e -g r a in e d lim esto n e beds a re 1 -2 f o o t th ic k
beds o f f i n e - to m edium -grained o o lit e s and a few coquina beds.
In
the map a re a , the Twin Creek Limestone is ap p ro x im a te ly 1 ,1 0 0 f e e t
t h ic k , s i g n i f i c a n t l y more than th e 871 f e e t measured by Wanless
e t al_.
(1955 ) a t Cabin Creek a t th e north border o f th e Pine Creek
Quadrangle.
Albee (1 9 6 8 ) measured 950 f e e t , and Jobin approxim ated
the th ic kn ess a t 9 0 0 -1 ,0 0 0 f e e t in th e Hunger Mountain and F e rry Peak
quadrangles, r e s p e c tiv e ly .
In th e map a r e a . Twin Creek s t r a t a a re l i t h o l o g i c a l l y s im ila r
to those in the a d ja c e n t re g io n .
Wanless ert al_. (1 9 5 5 ) d iv id e d th e
Twin Creek in to e ig h t c h a r a c t e r is t ic u n its which a r e , in ascending
o rd e r, ( I ) o o l i t i c
lim e s to n e , ( 2 ) s h a le , dark calcareo u s f o s s i l i f -
erous, (3 ) s h a le , c a lc a re o u s , r e d d is h , ( 4 ) lim e s to n e , o o l i t i c , g re y ,
( 5 ) s h a le , c a lc a re o u s , le s s f o s s i l ife r o u s than u n it 2 , (6 ) lim e s to n e ,
o o l it e b e a rin g , ( 7 ) Gryphaea s h a le zone, and (8 ) o o l i t i c lim estone
w ith some interb edded s h a le .
In h is re g io n a l s tu d y , Im lay (1 9 6 7 )
55
d iv id e d th e Twin Creek in to seven members which from bottom to top
a re named Gypsum S p rin g , S lid e ro c k ( u n it I a b o v e ). Rich ( u n i t 2 ) ,
boundary Ridge ( u n i t 3 ) , Watfon Canyon (u n its 4 , 5 , 6 ) , Leeds CvF.ek
( u n it 7 ) , and G ir a f f e Creek ( u n it 8 ) .
R e g io n a lly , these members show
s ig n if ic a n t l it h o l o g i c v a r ia t io n which Im lay (1 9 6 7 ) discussed in g re a t
d e ta il.
Environment o f D e p o s itio n .
The Twin Creek was dep osited
during th e f i r s t m arine tra n s g re s s io n from th e n o rth during M iddle
T r ia s s ic tim e.
The g r e a te s t subsidence and r e s u lt in g d e p o s itio n
occurred in th e Twin Creek trough o f so u th eastern Id a h o , w estern
Wyoming, and n o rth e rn Utah.
The sea was warm and shallow w ith p re ­
v a i l i n g , dry c lim a t ic c o n d itio n s and as w a te r depth v a r ie d , d e p o s itio n
in lagoonal environm ents occurred ( Im la y , 1 9 6 7 ).
Preuss Sandstone
Age and C o n ta ct.
Im lay (1952 ) suggested t h a t th e Preuss
Sandstone is Late J u ra s s ic (M id d le to Late C a llo v ia n ) in age.
He
based t h is conclu sion on th e f o s s ils found in o v e rly in g and u n d e rly in g
u n its and on re g io n a l s t r a t ig r a p h ic r e la tio n s h ip s .
The c o n ta c t w ith
th e u n d e rly in g Twin Creek Limestone is g ra d a tio n a l and, in most
p la c e s , occurs in le s s than 10 f e e t (Im la y , 1 9 5 0 ).
T his c o n ta c t is
w ell-exp o sed in th e core o f th e L i t t l e Greys a n t i c li n e along th e
L i t t l e Greys Road and along th e same a n t i c li n e on th e south bank o f
56
the Snake R iv e r.
The red-brown c o lo r o f the Preuss makes the c o n ta c t
w ith th e g re y , calcareous s h a le o f the u n d e rly in g Twin Creek e a s ily
d is c e rn a b le .
C o r r e la tio n s .
M a n s fie ld and Roundy (1 9 1 5 ) named th e Preuss
Sandstone f o r exposures n o rth e a s t o f M o n tp e lie r , Idaho.
Preuss
Sandstone term in o lo g y is a p p lie d in the same area as t h a t o f the Twin
Creek Lim estone, e a s te rn Id ah o , westernmost Wyoming, and n o r th -c e n tr a l
Utah (Im la y , 1 9 5 2 ).
Based on s t r a t ig r a p h ic p o s it io n , th e Prerss is
c o r r e la te d w ith the Entrada Sandstone o f s o u th -c e n tra l Wyoming and is
p a r t i a l l y te m p o ra lly e q u iv a le n t to th e Sundance Formation o f c e n tr a l .
Wyoming (Im la y , 1 95 2).
L ith o lo g y .
W ith in th e map a r e a , th e Preuss c o n s is ts o f re d -
brown, f in e -g r a in e d , c a lc a re o u s , t h in ly bedded to lam in ated sandstone
and s ilt s t o n e .
S a lt casts a re found in some o f the low er beds
exposed on th e e a s t f la n k o f th e L i t t l e Greys a n t i c li n e along th e
L i t t l e Greys R iv e r.
The Preuss is g e n e r a lly n o n -r e s is ta n t cropping
out o nly where steep scarp slopes r e s t r i c t v e g e ta tio n .
In th e Pine
Creek a r e a , the Preuss Sandstone was mapped w ith th e o v e rly in g Stump
Sandstone because o f i t s th in n e s s .
Preuss and Stump thicknesses
combined a re 300 f e e t a t th e n o rth end o f th e L i t t l e Greys a n t i c l i n e ,
450 f e e t a t the south end, and 300 f e e t in th e n o rth e a s te rn co rn e r
o f th e map a re a .
The th ic k n e s s o f these u n its ranges from 190-400
57
f e e t in the Hunger Mountain Quadrangle (A lb e e , 1968) to 225-275 f e e t
in the F erry Teak Quadrangle (J o b in , 1972).
R e g io n a lly , se v e ra l im p o rta n t l it h o l o g i c tre n d s occur w ith in
the Preuss Sandstone.
In th e Wasatch Mountains o f n o rth e rn U tah , the
Preuss is s o f t e r , s i l t i e r , and d a rk e r red than in Wyoming but i t is
s till
predom inantly a f in e -g r a in e d sandstone (Im la y , 1 9 5 2 ).
West o f
the Bannock th r u s t in s o u th e astern Id a h o , a m arine tongue, th e
W olverine Canyon Lim estone, is p re s e n t j u s t below th e m id d le o f th e
Preuss (Im la y , 1952, p. 1 7 4 ).
I t c o n s is ts p r i n c i p a ll y o f y e llo w is h -
g re y , sandy lim e s to n e , y e llo w is h sandstone and one o o l it e bed (Im la y ,
1 9 5 2 ).
Im lay re p o rte d exposures o f t h is member o n ly w est o f the
Bannock t h r u s t.
However, Kirkham (1 9 2 4 ) noted th e presence o f 18
f e e t o f grey crossbedded lim esto n e 3.70 f e e t above the Preuss on F a ll
C reek, B o n n e v ille County, Idaho t h a t Im lay thought may be a th in
extension o f th e W olverin e Canyon Member.
W anless, e t al..
(1 9 5 5 )
mentioned a 5 to 8 fo o t th ic k " n e a rly w h ite sandstone w ith s t r ik in g
c u rre n t r ip p le marks" t h a t occurs near th e m iddle o f the Preuss in
a l l measured s e c tio n s a d ja c e n t to th e Pine Creek area
th a t is
probably the sandstone u n it o f th e W olverine Canyon Lim estone.
The
sandstone was not observed in the map area but i t is probably p rese n t
but concealed because o f poor exposure.
Environment o f D e p o s itio n .
The presence o f m arine lim estone
suggests th a t th e Preuss is o f m arine o r ig in o r was d ep osited in
58
lagocns connecting w ith th e sea.
The red sandstone and s a l t beds
probably formed in a s e rie s o f h ig h ly s a lin e lagoons b o rd erin g a
p o s itiv e area in c e n tr a l Montana.
L a t e r i t i c s o i l s , developed as a
r e s u lt o f a warm and humid c lim a te on th e is la n d , were th e main source
o f iro n oxide and sand in th e Preuss ( Im la y , 1 9 5 2 ).
In e a r ly Late
J u ra s s ic tim e th e n o rth e a s t-tre n d in g high on th e w est again ro s e ,
supplying a d d itio n a l d e t r it u s to th e Preuss and o v e rly in g Stump
fo rm a tio n s .
Stump Sandstone
Age and C o n ta c t.
The age o f th e Stump Sandstone is m iddle
Late J u ra s s ic (O x fo rd ia n ) ( Im la y , 1 9 5 0 ).
The c o n ta c t w ith th e under­
ly in g Preuss Sandstone is considered to be discon form able ( Im la y ,
1 95 2).
A w e ll-e x p o s e d , sharp c o n ta c t occurs on th e e a s t fla n k o f
the L i t t l e Greys a n t i c l i n e along U.S. Highway 26-89 and both north
and south banks o f the Snake R iv e r a t t h is lo c a tio n .
mapping the c o n ta c t in th e f i e l d
For purposes o f
area was placed a t th e f i r s t ,
r e s i s t a n t , g re y -g re e n , g la u c o n itic sandstone bed.
C o r r e la tio n s .
M a n s fie ld and Roundy (1 9 1 6 ) named th e Stump
Sandstone f o r exposures near Stump Peak in so u th eastern Idaho.
It
is found in so u th e astern Id ah o , w estern Wyoming, and n o rth e a s te rn
Utah and is not as widespread as the Preuss and Twin Creek (S ta a tz
and Al bee, 1 9 6 6 ).
The Sum m erville and C u rtis fo rm a tio n s o f n o rth e rn
59
Utah; th e Redwater Shale Member o f the upper Sundance o f c e n tra l and
e as te rn Wyoming, a re tem poral and l i t h i c e q u iv a le n ts o f the Stump
Sandstone (P e te rs o n , 1 9 7 2 ).
L ith o lo g y .
The Stump Sandstone can be subdivided in to th re e
l i t h i c u n its w ith in the study a re a ; a basal u n it c o n s is tin g o f a
g re e n is h -g re y , very f in e - g r a in e d , calcareous sandstone; a m edial u n it
o f brow n-grey, o o lit e - h e a r in g , c o q u in o id , sandy lim e s to n e ; and an
upper u n it dominated by g re y -g re e n , m edium -grained, g la u c o n it ic ,
calcareous sandstone.
The upper sandstone u n it is a prom inent c l i f f
fo rm e r, and the n o n -r e s is ta n t basal and m edial u n its a re p a r t i a l l y
obscured by i t s p la t y t a lu s .
Throughout i t s
e x te n t th e Stump is c h a ra c te riz e d by coarse­
grained sandstone and a co n sta n t san d-shale r a t i o .
Eastw ard, in
c e n tra l Wyoming and Montana, th e c o a rs e r c l a s t ic rocks grade to a
grey and g reen -g rey sh a le fa c ie s w ith lim esto n e and sandstone being
m inor components.
In th e southw estern p a r t o f c e n tr a l Wyoming,
m arine lim estone is the predominant fa c ie s typ e (P e te rs o n , 1 9 7 2 ).
Environment o f D e p o s itio n .
The Stump Sandstone was deposited
during th e most e x te n s iv e o f the J u ra s s ic tra n s g re s s io n s o f th e A r c t ic
Sea.
The o o l i t i c , c o q u in o id , sandy lim estone is in d ic a t iv e o f a
shallow depth o f w a te r, a t le a s t d uring d e p o s itio n o f these sedim ents.
Brenner and Davies (1973 ) b e lie v e d t h a t the b io c la s t ic components
were r e d is t r ib u t e d by in te n s e storms which a g ita te d th e shallow w a te r.
60
The even-bedded c h a ra c te r o f much o f th e rem ainder o f th e Stump in
th e study area suggests a s l i g h t l y g re a te r depth o f w a te r w h ere,
c u rre n t and wave a c tio n was not e f f e c t i v e in tra n s p o rtin g d e t r it u s . •
Cretaceous S tr a ta — Previous Work
Cretaceous age s t r a t a exposed w ith in th e map area in c lu d e the
Gannett Group, th e Bear R iv e r F o rm atio n , and th e Aspen Shale ( F ig . 5 ) .
Follow ing the precedent o f U .S. G eological Survey g e o lo g is ts in the
a re a , the Gannett Group was sep arated in to a low er u n i t , th e Ephraim
Conglom erate, and an upper u n it in c lu d in g , in ascending o r d e r , th e
Peterson Lim estone, B e ch ler F o rm atio n , and Draney Lim estone.
The
Bear R iv e r Form ation was d iv id e d in to a low er u n it which in clu d es
th e Muddy Sandstone and u n d e rly in g dark sh a le sequence, and an upper
u n it composed o f b la c k s h a le .
The Aspen Shale was n e t subdivided in
the map area as i t has been to th e n o rth because o f the th in n ess o f
the p o r c e la n ite bed which has been used to s e p arate the low er and
upper u n it s .
Previous work on Cretaceous s t r a t a in clu d es re g io n a l s tu d ie s
in so u theastern Idaho and a d ja c e n t areas by M a n s fie ld (1 9 2 0 ) and
M o ritz (1 9 5 3 ).
S t r a t ig r a p h ic s tu d ie s on Cretaceous s t r a t a which
in c lu d e th e map area o r the re g io n a d ja c e n t to i t were pub lished by
Eyer (1969 ) on the G annett Group; by LaRocque and Edwards (1 9 5 4 ) on
the Bear R iv e r and Aspen fo rm a tio n s ; and by Yen (1 9 5 2 ) who discussed
61
th e age o f the Bear R iv e r .
An ongoing in v e s tig a tio n o f the Aspen and
Bear R iv e r fo rm a tio n s in th e area d i r e c t ly a d ja c e n t to the Pine Creek
Quadrangle is being undertaken by Nazeeh Abraham o f the U n iv e rs ity o f
M ichigan.
Wanless e t al_.
(1 9 5 5 ) measured s e v eral s e c tio n s o f
Cretaceous s t r a t a a d ja c e n t to th e map area and a t o th e r l o c a l i t i e s
in th e T e to n , Hoback, and Gros V en tre ranges.
Gannett Group
Age and C o n tacts.
M a n s fie ld (1 9 2 7 ) assigned th e e n t i r e
Gannett Group to the E a rly Cretaceous.
On th e b as is o f f o s s il e v i­
dence, Stokes (1 9 4 4 ) and M a n s fie ld (1 9 5 2 ) placed th e low er p a r t o f
the Ephraim in the Late J u ra s s ic .
Peck and C raig (1 9 6 2 ) and Eyer
(1969) re p o rted species o f charophytes t h a t dated the upper p a r t o f
the Ephraim Conglomerate as E a rly C retaceous.
T h e re fo re , th e evidence
in d ic a te s t h a t the J u ra s s ic -C re ta c e o u s boundary l i e s in th e Ephraim
Conglomerate.
The low er c o n ta c t o f the Gannett Group is conform able
w ith the Stump Sandstone and th e fau n al evidence supports t h is con­
c lu s io n ( E y e r, 1 9 6 9 ).
The c o n ta c t is n o t exposed in the f i e l d
area
due to a covered sh a le in te r v a l above th e l a s t g la u c o n itic sandstone.
The Smoot Form ation, d esign ated by Eyer (1969 ) as p a r t o f th e G annett
Group, b u t mapped w ith th e o v e rly in g Bear R iv e r Form ation by the
w r i t e r , con tains fauna t r a n s it io n a l
the A lb ia n Bear R iv e r Form ation.
from th e A p tian G annett Group to
62
C o rr e la tio n s .
The Gannett Group is o n ly recognized w ith in
the th r u s t b e l t but based on s t r a tig r a p h ic p o s itio n e q u iv a le n t s t r a t a
are recognized in surrounding a re a s .
In th e Gros V en tre Range,
Love e t aj_. (1948 ) subdivided th e C lo v e rly Form ation in to low er and
upper u n its .
They considered the boundary between these u n its to be
e q u iv a le n t to th e G annett-B ear R iv e r c o n ta c t.
In support o f t h is
c o r r e la t io n , Eyer (1 9 6 9 ) considered th e upper C lo v e r ly , known as
the " ru s ty beds," to be e q u iv a le n t tc the Smoot Form ation.
F u rth e r­
more, the low er C le v e r ly , c o n s is tin g o f lim e s to n e , mudstone, and
s h a le , is probably e q u iv a le n t to a l l but th e lowermost p a r t o f the
Gannett (E y e r, 1 9 6 9 ).
Furer (1 9 7 0 ) suggested t h a t th e low er Ephraim ,
composed o f shale and s ilt s t o n e w ith minor interb edded sandstone, is
te m p o ra lly and l i t h o l o g i c a l l y e q u iv a le n t to th e Upper J u ra s s ic
M orrison Form ation.
L ith o lo g y .
Throughout the map a r e a , th e Ephraim Conglomerate
con sists o f l ig h t - p u r p le to w h ite , m edium -grained, q u a r t z i t i c sand­
stone (" q u a rtz c r y s ta l sandstone" o f Wanless e t a l_ ., 1955) w ith
o v e rly in g u n its o f re d -p u rp le to red-brow n, v e ry f i n e - to medium. grain ed sandstone w ith a s s o ciate d conglom erate le n s e s .
Several
covered in te r v a ls probably re p re s e n t shale and c la y s to n e u n its .
Conglomerate occurs in the Ephraim over most o f the map area but
is b est exposed along th e e a s t fla n k o f th e L i t t l e
Greys a n t i c li n e
where th e Gannett Group was measured (see Appendix, page 1 2 4 ).
Here
63
i t co n sis ts o f subrounded- to a n g u la r c la s t s , up to 2 inches in
d ia m e te r, composed o f c h e r t , q u a r tz , and o c c a s io n a lly lim e s to n e .
These conglom erate beds are n o t more than 2 f e e t th ic k and occur as
conglomerate lenses in sandstone 200 f e e t above th e Stump-Ephraim
c o n ta c t.
A 22 fo o t t h ic k bed o f p u rp le c laysto n e w ith g re y , calcareous
nodules is p re s e n t a t the Ephraim -Peterson Limestone c o n ta c t.
The measured s e c tio n o f th e G annett Group along th e e a s t lim b
o f the L i t t l e Greys a n t i c li n e is 532+ f e e t t h ic k , in c lu d in g 448 f e e t
o f Ephraim.
On th e n o rth e rn m argin o f the map a r e a , along th e Snake
R iv e r , th e Ephraim Conglomerate is 275 f e e t t h ic k and th e upper
Gannett is 225 f e e t th ic k .
Wanless e t a h
(1955 ) measured 780 f e e t
o f Gannett s t r a t a a t Cabin Creek and t h is th ic kn ess is c o n s id e ra b ly
more than e it h e r Albee (1 9 6 8 ) (435 f e e t ) o r Jobin (1 9 7 2 ) (550 f e e t )
measured.
The G annett Group reaches maximum th ickn ess near th e type
s e c tio n in sou theastern Idaho (E y e r, 196 9).
The u n its exposed in the study area a re ty p ic a l o f lit h o lo g ie s
found elsew here in th e Ephraim Conglomerate.
G e n e ra lly , g ra in s iz e
decreases to th e n o r th , s o u th , and e a s t away from th e type s e c tio n a t
Red Mountain in sou th eastern Idaho (E y e r, 1969) evidenced by th e la c k
o f conglomerate e a s t and n o rth e a s t o f th e Camp Davis area (Wan!ess
e t a j_ ., 1 95 5).
At Cabin Creek on the n o rth e a s te rn boundary o f th e
map a re a , two conglom erate beds t o t a lin g 30 f e e t , w ith pebbles to
h inch in d ia m e te r, occur in th e Ephraim.
64
The upper Gannett Group w it h in the map area in c lu d e s , in
ascending o r d e r , th e Peterson Lim estone, B ech ler Form ation and Dtuney
Lim estone.
The l i t h o l o g i c a l l y s im ila r Draney and Peterson Limestone
c o n s is t o f g re y -p u rp le to ta n n is h -g r e y , w h ite -w e a tn e rin g , mi c r i t i c '
lim estone w ith a few c h e rt nodules.
The P e ters o n , the p r in c ip a l
lim estone in th e G annett Group, is presen t throughout th e map a re a .
The Draney, however, is not p re s e n t over th e e n t i r e Pine Creek
Quadrangle as In d ic a te d by Eyer (1 9 6 9 ).
Because o f e x te n s iv e f o r e s t
cover i t was d i f f i c u l t to d eterm in e th e p re c is e lo c a tio n o f the Draney,
but i t is c le a r ly not p re s e n t in th e so u theastern t h ir d o f th e map
a re a .
In th e map a re a , th e B ech ler Formation c o n s is ts o f b u f f -g r e y ,
c a lc a re o u s , f i n e - to m edium -grained, q u a rtzo se sandstone which is
o n ly o c c a s io n a lly p re s e n t.
R e g io n a lly , throughout th e rem ainder o f the o v e rth r u s t b e l t ,
th e re are in te rb e tid e d , grey and r e d , calcareous shales in the Draney
and Peterson Lim estone.
The B e ch ler c o n sis ts o f red and maroon
s ilt s t o n e and s h a le , w ith in te rb e d d e d , n o d u lar lim esto n e and grey
and re d d is h -g re y sandstone.
There is als o a t h in conglom erate bed
w ith c la s ts up to 2 inches in d ia m e te r found lo c a l ly in the B echler
a t the type s e c tio n (E y e r , 1 9 6 9 ). . These le s s - r e s is t a n t s t r a t a a re
undoubtedly p rese n t in th e map a re a but a re g e n e r a lly concealed by
slumps and mudflows.
65
Environment o f D e p o s itio n .
The low er p a r t c f th e Ephraim
Conglomerate was dep o sited under open m arine c o n d itio n s during the
Late J u ra s s ic tra n s g re s s io n o f the A r c t ic Sea.
This environm ent is
in d ic a te d f o r these s t r a t a based on m arine J u ra s s ic f o s s ils found 50
f e e t above th e base o f th e Ephraim in so u th eastern Idaho (M a n s fie ld ,
1952, p. 4 2 ).
The rem aining G annett Group is c l e a r l y nonm arine,
evidenced by f o s s il types and l i t h o l o g i c a s s o c ia tio n s such as the
th ic k conglom erate and sandstone u n its , and red-bed sequence.
The
change from m arine to nonmarine c o n d itio n s p robably r e s u lte d from
strong te c to n ic movements in so u th e astern Idaho th a t caused th e sea
to regress (Armstrong and O r i e l , 1 9 6 5 ), and t h a t c re a te d a w estern
sediment source.
The d e p o s itio n a l environm ents o f the upper Ephraim and B echler
Formation were s i m il a r .
Both were d ep osited in a l l u v i a l fans and
f l u v i a l systems a d ja c e n t to the r is in g land mass to th e w est (E y e r,
1 9 6 9 ).
The a n g u la r ity o f some o f th e pebbles in th e Ephraim Conglom­
e r a te in the Fine Creek area suggests th a t p a r t o f the m a te ria l in
these fans was lo c a l ly d e riv e d .
In the study a r e a , low er energy
c o n d itio n s p re v a ile d d u rin g d e p o s itio n o f th e B ech ler Form atio n,
evidenced by th e la c k o f conglom erate in th is u n i t .
The Draney and
Peterson lim estones were dep o sited in fre s h w a te r lakes in which th e
w ate r depth d id not exceed 50 f e e t , based on th e presence o f
charophyte f o s s ils o f fre s h -w a te r o r ig in (E y e r, 1 9 6 9 ).
66
Bear R iv e r Formation
.
Age and C o n tacts.
u n s e ttle d problem.
I
The age o f th e Bear R iv e r Form ation is an
P re v io u s ly , th e Bear R iv e r was assigned to the
Late Cretaceous ( e .g . Hayden 1869, Stanton 1 8 9 2 ).
On th e b asis o f
th e Bear R iv e r fa u n a . Yen (1 9 5 2 ) r e fin e d t h is d e s ig n a tio n , assign ing
the Bear R iv e r to th e e a r l i e s t Late Cretaceous (Cenomanian S ta g e ).
However, Cobban and Reeside (1 9 5 2 ) and, more r e c e n t ly , Cobban ( 1 9 /y )
placed th e Bear R iv e r in th e l a t e s t E a rly Cretaceous ( A lb ia n S ta g e ),
in agreement w ith Eyer (1 9 6 9 ).
The lo w er c o n ta c t o f th e Bear R iv e r
is considered by Eyer (1 9 6 9 ) to be conform able w ith th e u n d erlyin g
G annett Group on both l it h o l o g i c a l and p a le o n to lo g ic grounds.
The
c o n ta c t in the map area is g e n e r a lly concealed by mudflows and
slumps.
C o rr e la tio n s .
The Bear R iv e r Formation was named by Hayden
(1 8 6 9 ) f o r exposures near Old Bear R iv e r C it y , Wyoming.
is f a i r l y lo c a l
T h is u n it
in e x te n t and is m ain ly found in th e th r u s t b e l t o f
westernmost Wyoming and in th e Snake R iv e r Range in Idaho (S ta a tz
and A lb ee , 1 9 6 6 ).
The l i t h i c and temporal e q u iv a le n ts o f th e Bear
R iv e r a re in e x t r ic a b ly lin k e d to a nom enclature problem o f th e M iddle
Cretaceous rocks o f th e o v e rth r u s t b e l t re g io n and a discu s sio n o f
t h is problem is w arranted h e re .
The Thenropoli s ; Shale has commonly
been considered to c o n s is t o f th re e u n it s ; a low er dark s h a le u n i t ;
a m iddle sandstone, w id e ly known as th e Muddy Sandstone; and an upper
67
dark sh a le u n it (Wan!ess e t a l . ,
1 9 5 5 ).
These correspond to the
th re e s t r a tig r a p h ic u n its o f th e Bear R iv e r in th e Pine Creek a re a .
East o f the study area in th e Wind R iv e r Basin o f Wyoming, Love (1 9 4 3 )
(I)
r e s t r ic t e d th e term Therm opolis to th e low er s h a le u n i t , (2 )
suggested t h a t th e muddy Sandstone be viewed as a s e p a ra te fo rm a tio n ,
and (3 ) r e fe r r e d th e upper s h a le u n it to the basal p a r t o f th e o v e rly in g Mowry S h a le , the l i t h i c
S h ale.
and temporal e q u iv a le n t o f the Aspen
The Wyoming G eo lo g ical A s s o c ia tio n S t r a t ig r a p h ic Nomenclature
C hart (1 0 7 1 ) f u r t h e r com plicates th e nom enclature! p ic tu r e by equating
the Bear R iv e r w ith the Dakota Sandstone, Therm opolis S h a le , and Muddy
Sandstone.
The eq u iva len cy o f the Bear R iv e r Form ation w ith these
u n it s , as d e fin e d by Love (1 9 4 8 ) and th e Wyoming G eo lo g ical A ssocia­
t io n (1 9 7 1 ), is c o n tra ry to th e U .S . G eo lo g ical Survey s t r a t ig r a p h ic
scheme in th e map area and the re g io n a d ja c e n t to i t .
They subdivided
th e Bear R iv e r in to two u n it s , p la c in g th e c o n ta c t between these u n its
on th e top o f the Muddy Sandstone as mapped to th e e a s t, and included
the upper dark sh a le u n it in th e Bear R iv e r in s te a d o f th e o v e rly in g
Aspen S h ale.
R icher (1962 ) in an e f f o r t to re s o lv e t h is c o n f l i c t ,
in trod uced a new te rm , " S h e ll Creek Shale" f o r th e in t e r v a l between
the s ilic e o u s Mowry (Aspen) and the top o f th e Muddy Sandstone.
These s t r a t ig r a p h ic r e la tio n s h ip s a re summarized in F ig u re 11.
West o f th e map a r e a , in so u th eastern Id ah o , th e Bear R iv e r
Formation is l i t h o l o g i c a l l y and te m p o ra lly e q u iv a le n t to th e low er
Moritz (1953),
Randall (1960)
southeastern
Idaho, Freedom
area
Prior to
Love (1948)
Gros Ventre
Ra. & east
Love (1948)
Gros Ventre
Ra. & east
Eicher (1962)
east of
overthrust
b e lt
WGA Chart
(1971) for
north and
east Green
River Basin
This Paper
MOWRY
SHALE
ASPEN
SHALE
FRONTIER SANDSTONE
WAYAN
FORMATION
Unit E~
Unit D
Unit C
Unit B
Unit A
Fig u re 11.
MOWRY
SHALE
MOWRY
SHALE
upper
dark
shale
upper
dark
shale
SHELL
CREEK
SHALE
MUDDY
SANDSTONE
MUDDY
SANDSTONE
MUDDY
SANDSTONE
MUDDY
SANDSTONE
dark
shale
THERMOPOLIS
SHALE
THERMOPOLIS
SHALE
THERMOPOLIS
SHALE
MOWRY
SHALE
upper
dark
shale
"DAKOTA"
SANDSTONE
C o rre la tio n diagram f o r Lower Cretaceous s t r a t a in western
Wyoming and ad ja c e n t are a s .
sandstone
and
lower
dark
shale
69
fo u r u n its o f the Wayan Formation ( F ig . 11) as d e fin e d by M o ritz
(3 9 5 3 ).
The Tygee Member o f th e Bear R iv e r Formation was o r i g in a ll y
assigned by M a n s fie ld and Roundy (1 9 1 6 ) to th e G annett Group.
As
i n i t i a l l y d e fin e d , i t c o n sis ted o f o n ly the sandstone u n i t , b u t is
now considered to in c lu d e the upper sandstone u n i t , l i t h o l o g i c a l l y
and te m p o ra lly e q u iv a le n t to th e m u d d y sandstone (E y e r , 1 9 6 9 ), and
lower dark shale u n i t .
Tygee te rm in o lo g y is used in extrem e w estern
Wyoming and in so u th eastern Idaho (R a n d a ll, 1 9 6 0 ).
L ith o lo g y .
In th e map a r e a , th e dark sh a le in the low er
Bear R iv e r is interbedded w ith s i l t y mudstone, s i l t y sandstone, and
fin e -g r a in e d sandstone.
Although these l it h o l o g i c types are found
everywhere in the map a r e a , they a re p a r t i c u l a r l y w e ll developed on
th e west lim b o f the L i t t l e Greys a n t i c li n e a t the southern b o rd e r.
T y p ic a lly , the s i lts to n e and fin e -g r a in e d sandstone u n its a re d a rk g re y , m edium-grey, g re e n -g re y , t h in - to medium-bedded, o c c a s io n a lly
c a lc a re o u s , n o d u la r, and l im o n i t i c , w ith abundant b io tu r b a tio n
s tru c tu re s and so le m arkings.
They a re composed o f q u a r t z , c h e r t ,
and v o lc a n ic (? ) rock fragm ents.
One e x c e lle n t exposure o f th is
lit h o lo g y occurs south o f th e L i t t l e Greys R iv e r on th e w est fla n k
o f th e a n t i c li n e .
Here medium- to b u f f -g r e y , m assive, cross-bedded,
muddy s i lts to n e and f in e -g r a in e d sandstone forms a prom inent 60 fo o t
ledge.
Black shale is th e predeom inant rock type in th e low er Bear
R iv e r over much o f the rem ainder o f the map a re a .
The s h a le is
70
d a rk -g re y - to b la c k , h a rd , s p l i n t e r y , l im c n it ic on th e w eathered
s u rfa c e s , and g e n e r a lly p o o rly exposed, form ing a d i s t in c t i v e b lack
s o il.
Sandstone makes up th e upper p a r t c f th e low er Bear R iv e r a t
a ll
lo c a litie s .
T y p ic a lly t h is sandstone is l ig h t - g r e y , w eath erin g
b u f f -g r e y , f i n e - to m edium -grained, subrounded to s u b an g u lar, massive
and crosshedded, lim o n ite s ta in e d , q u a rtz o s e , and r e s is t a n t .
It
is
an extrem ely clean sandstone, composed o f q u a r t z , c h e rt and v o lc a n ic
(? ) rock fragm ents (T b !. I ) .
This sandstone is b es t developed in
the northw estern p a r t o f th e map area on th e west f la n k o f the L i t t l e
Greys a n t i c li n e along Iro n Rim Creek ( P I .
I)
and to th e north along
U.S. Highway 26-89 on th e border o f th e map a re a .
The upper Bear R iv e r , which is p a r t i c u l a r l y w e ll exposed in
the v i c i n i t y o f th e measured s e c tio n o f the o v e rly in g Aspen Shale
(see Appendix, page 1 2 4 ), c o n s is ts predo m inan tly o f b la c k - to d a rk grey s h a le , s im ila r in a l l resp ects to th e s h a le in the low er Bear
R iv e r.
In th e map a r e a , a few p o o rly exposed beds o f l ig h t - g r e y ,
f in e -g r a in e d , sandstone and s ilt s t o n e a re in te rb ed d ed w ith t h is
s h a le .
A few th in beds o f m edium -grey, d ark -b ro w n -w e a th e rin g ,
m ic r i t ic lim esto n e a re p rese n t near the c o n ta c t w ith th e Aspen S h ale.
The th ic kn ess o f the Bear R iv e r Form ation, e s p e c ia lly the
upper u n i t , is v a r ia b le throughout the map area , in c re a s in g to the
south and w est.
Maximum th ic kn ess is a tta in e d on th e southwest lim b
Tab le I .
Volume percentages o f g ra in c o n s titu e n ts , cementing ag e n ts , and m a trix
from s e le c te d th in sec tio n s from sandstone and s ilt s t o n e o f the Bear
R iv e r and Aspen fo rm a tio n s .
CHERT
ROCK
FRAGS.
( P r im a r ily ]
[V o lc a n ic J
55-60
25
5
<1
SANDSTONE
(a sso c, w ith
c o n g .)
40
35
<10
10
<5
SILICA
CALCITE (s e co n d a ry)
SILTSTONE
70
SILICA
CALCITE (s e c o n d a ry )
SILTSTONE
(fro m lo w e r]
[B ear R iverJ
90
QUARTZ
BEAR RIVER
ASPEN
SANDSTONE
SANDSTONE
(fro m upper
sandstone u n it In
Tygee Sandstone
65
»
20
FELDSPAR
10-15
r
S3
1
I
25
,r
1
<1
<5
15
CEMENT
MATRIX
CALCITE
HEMATITE
SILICA
CALCITE (s e c o n d a ry )
SILICA
72
o f the L i t t l e Greys a n t i c li n e where the lo v e r and upper Bear R iv e r ,
a re 450 and 800 f e e t th ic k r e s p e c tiv e ly .
A t the north border o f the
map a r e a , the th ic kn ess decreases to 400 and 500 f e e t , r e s p e c tiv e ly .
In the n o rth e a s t p a r t o f th e map area the low er Bear R iv e r is
»00
f e e t th ic k and th e upper is 425 f e e t and south o f t h is the thickness
increases to 450 and 700 f e e t f o r th e low er and upper u n it s ..
In th e area a d ja c e n t to th e o v e rth r u s t b e l t , fa c ie s v a r ia tio n s
in the l i t h i c and temporal e q u iv a le n ts o f th e Bear R iv e r a re not
s ig n i f i c a n t .
In the Big Horn Basin o f c e n tr a l Wyoming, th e Thermopolis
Shale co n sis ts o f d a rk -g re y s h a le and in terb ed d ed s ilt s t o n e and sand­
stone.
The Muddy Sandstone here is g e n e r a lly f i n e r g rain ed than th a t
in the map area and is comprised o f in te rb ed d ed s i l t s t o n e , sandstone
and shale (E ic h e r , 1 9 6 2 ).
West o f th e study area in n o rth e a s te rn
Idaho, the Wayan Formation is s im ila r to th e Bear R iv e r in th e Pine
Creek Quadrangle alth ough red and v a rie g a te d sandstone and mudstone
make up a s ig n if ic a n t p a r t o f the s e c tio n ( M o r it z , 1 9 5 3 ).
Environment o f D e p o s itio n .
D e p o sitio n o f the Bear R iv e r .
Formation occurred d u rin g th e i n i t i a l stages o f th e E a rly Cretaceous
tra n s g re s s io n t h a t culm inated in the
Mowry-Aspen sea.
Fresh
and
open m arine c o n d itio n s o f the
b ra c k is h w a te r fauna were c o lle c te d from
the upper Bear R iv e r by LaRocque and Edwards (1 9 5 4 ) in th e W illo w
Creek a r e a , 2 m iles n o rth e a s t o f th e Pine Creek Quadrangle.
Wanless
e t al_. (1 9 5 5 ) c o lle c te d m arine forms from th e upper Bear R iv e r in
73
s e v eral s e c tio n s in th e area a d ja c e n t to the Pine Creek Q uadrangle,
although th e low er Bear R iv e r is n e a rly u n fo s s ilife r o u s in t h is same
a re a .
E ich e r (1962 ) a t t r ib u t e d th e la c k o f fauna in the Bear R iv e r
e q u iv a le n ts in th e Big Horn Basin to b rack ish w a te r c o n d itio n s .
The environm ent o f d e p o s itio n o f the Bear R iv e r w ith in th e
map area can be bro ad ly c h a ra c te riz e d as m arginal m a rin e , in flu e n c e d
by periods o f emergence and submergence.
R ip p le m arks, b ic tu r b a tio n
s tr u c tu r e s , and the l it h o l o g i c a s s o c ia tio n s such as th e b lack s h a le ,
and sandy mudstone and s i lts t o n e suggest t h a t the w a te r depth was
q u ite sh allo w .
The environm ent flu c tu a te d from perio d s o f r e l a t i v e
s t a b i l i t y during which the more w e ll-s o r te d s ilt s t o n e and sandstone
beds accumulated to more u n s ta b le c o n d itio n s when arenaceous and
a rg illa c e o u s fr a c tio n s were m ixed.
This was, perhaps, due to a
v a r ia b le depth o f w a te r r e s u lt in g from the in te r a c tio n o f tra n s g re s ­
sion and p ro g ra d a tio n .
E u xin ic c o n d itio n s , evidenced by th e th ic k
>
■
■
i
accum ulation o f b lack s h a le , p r e v a ile d during d e p o s itio n o f the
m iddle p a r t o f the low er Bear R iv e r.
During th e c lo s in g stages o f
low er Bear R iv e r d e p o s itio n , however, open m arine c o n d itio n s were
dominant
as suggested by th e t h i c k , c le a n , q u a rtz o s e , m ature sand­
stone in the upper p a r t o f th e Tygse Sandstone.
The sandstone
sequence developed as a p r o -d e lta accum ulation when p ro g ra d a tio n was
not o c c u rrin g .
C u rren t and wave a c t io n , which winnowed out th e f i n e ­
grained sed im ent, was e f f e c t i v e in tra n s p o rtin g and r e d is t r ib u t in g
74
the co arser sedim ent.
The environm ent o f d e p o s itio n o f th e upper
Bear R iv e r was much th e same as d u rin g d e p o s itio n o f th e m iddle
sequence c f th e low er Bear R iv e r when th e t h ic k b la c k sh a le u n it
was d ep o sited .
The general s e d im e n ta ry -te c to n ic p a tte r n d u rin g d e p o s itio n
o f the Bear R iv e r is a d e lta and a s s o c ia te d t e r r e s t r i a l environm ent.
Much o f the s t r a t a accumulated as a flo o d p la in and t i d a l f l a t
sequence w ith ass o ciate d fre s h w a te r lakes and lagoons t h a t were
p e r io d ic a lly b a rred .
Aspen Shale
Age and C o n ta cts.
The age o f th e Aspen is u n s e ttle d because
o f the con troversy surrounding th e age o f th e u n d e rly in g Bear R iv e r.
The l i t h o l o g i c a l l y and te m p o ra lly e q u iv a le n t Mowry Shale o f Montana
and Wyoming is E a rly Cretaceous in age on th e b asis o f species o f
G a s tro p lite s and N e o g a s tro p lite s (Cobban and R eeside, 1 9 5 1 ).
The
low er co n ta c t o f th e Aspen w ith th e Bear R iv e r is considered to be
conformable by a l l workers ( e .g .
195 3).
LaRocque and Edwards, 1954, M o r it z ,
D if f e r e n t workers in th e a d ja c e n t area have placed t h is con­
t a c t a t s l i g h t l y d i f f e r e n t s t r a t ig r a p h ic p o s itio n s .
M o ritz (1953 )
placed the c o n ta c t a t the f i r s t s ilic e o u s s h a le bed, and LaRocque and
Edwards (1 9 5 4 , p. 320) placed the boundary "above the t h ic k dark
s p lin te r y s h a le o f Bear R iv e r a s p e c t...a n d below th e f i r s t s a l t and
75
pepper sandstone."
The c o n ta c t was drawn by S ta a tz and Albee (1 9 6 6 )
a t th e f i r s t prom inent sandstone ledge below th e lo w est p o r c e la n ite .
W ith in the map area the c o n ta c t is g ra d a tio n a l over 40 to 50 f e e t
and i t is placed b e fo re the l a s t b lack s h a le , above in te rb e d s o f
g re y -g re e n , f in e - g r a in e d , thin -bedded sandstone, and below th e f i r s t
g rey-green sandstone w ith medium g ra in s o f b la c k c h e r t.
C o rr e la tio n s .
The Aspen Shale was named by Vcatch (1 9 0 7 )
f o r s t r a t a exposed near Aspen S t a t io n , U in ta County, Utah.
Aspen
term in o lo g y is r e s t r ic t e d to th e t h r u s t b e l t between the Absaroka
th r u s t on th e west and southw est, and th e edge o f the o v e rth r u s t b e lt
on the e a s t and n o rth e a s t (S ta a tz and Al bee, 1 9 6 6 ).
The Wayan Forma­
t io n o f extreme western Wyoming and so u theastern Idaho is the l i t h i c
and p a r t ia l tem poral e q u iv a le n t o f th e Aspen ( M o r it z , 1 9 5 3 ).
East
o f the map area o v e r much o f c e n tr a l Wyoming and Montana, th e Mowry
Shale is l i t h o l o g i c a l l y and te m p o ra lly e q u iv a le n t ( F ig . 11) to the
Aspen Shale (Cobban and R eeside, 1 9 5 2 ).
L ith o lo g y .
The Aspen S h a le , th e most w idespread u n it in th e
map a re a , crops out on both fla n k s o f th e L i t t l e Greys a n t i c li n e in
a broad outcrop band co verin g th e c e n tr a l p o rtio n o f the Pine Creek
Q uadrangle, and on the w est lim b as a wide b e l t extend ing to the
Absaroka th r u s t (F ig .
1 7 ), (P I.
I).
The Aspen c o n s is ts o f a monoto­
nous sequence o f interb edded s ilic e o u s s h a le , sandstone, and
p o r c e la n ite .
In a d d it io n , a t h in pebbly conglom erate u n it occurs
76
w ith in ths upper Aspen in both th e c e n tra l and w estern outcrop b e lt s .
The tr u e th ickn ess o f the Aspen Shale in th e map area is unknown
because s tr u c tu r a l involvem ent makes an acc u ra te measurement impos­
s ib le .
The b es t e s tim a te , however, is t h a t th e Aspen is on the
o rd e r o f 4 ,0 0 0 to 4 ,5 0 0 f e e t t h ic k .
T his is not unreaso n ab le, when
compared to the 3 ,9 0 0 f e e t th ic kn ess measured by Albee (1 9 6 8 ) in th e
Munger Mountain Quadrangle.
Wanless e t aJL (1 9 5 5 ) did n o t measure
a complete se c tio n o f Aspen but the r e s u lts o f t h e i r in v e s tig a tio n
in d ic a te th a t the Aspen th ic ken s to th e south and w est.
The sandstone o f th e Aspen Shale is t y p i c a l l y g re y -g re e n ,
f i n e - to m edium -grained, t h i n l y bedded to massive and cross-bedded,
o c c a s io n a lly c a lc a re o u s , and g e n e r a lly more r e s is t a n t than th e i n t e r ­
beds o f shale (F ig .
1 2 ).
Although most are t i g h t l y cem ented, some
o f the sandstone is m o d erately f r i a b l e .
G rain c o n s titu e n ts a re
q u a rtz , c h e r t, and v o lc a n ic (? ) rock fragm ents w ith m inor amounts o f
fe ld s p a r , g iv in g some o f th e sandstone a " s a lt and pepper" appearance.
Most o f th e g ra in s are subangular to subrounded, although a bimodal
d is t r ib u t io n is e v id e n t w ith some g ra in s being v e ry w e ll rounded.
The percentage o f fe ld s p a r in th e sandstone and s ilt s t o n e o f the
Aspen is s im ila r to t h a t o f the Bear R iv e r s t r a t a , although the
fe ld s p a r co n ten t is g r e a te s t (1 0 p e rc e n t) in the sandstone ass o ciate d
w ith th e conglom erate.
Tab le I compares estim ated g ra in c o n s titu e n ts ,
cement ty p e s , and m a trix volumes f o r s e le c te d samples o f the sandstone
77
Figure 12.
Sand-shale co n ta c t in Aspen S hale.
o f s ilic e o u s s h a le .
Note s p lin t e r y nature
73
and s i Its to n e o f th e Hear R iv e r and Aspen fo rm a tio n s g e n e r a lly
suggesting t h a t both w a te r depth and v o lc a n ic a c t i v i t y
during d e p o s itio n o f th e Aspen S h ale.
increased
F ig u re 13 shows com parative
photomicrographs o f the sandstone from these fo rm a tio n s .
In te rb e d s
o f g re y -g *e e n , sometimes g la u c o n it ic , t h in ly bedded s l l t s t o n e , and
an occasional th in ( I fo o t t h ic k ) bed o f m i c r i t i c lim esto n e and
s ilty
lim estone a ls o occur w ith the sandstone.
The r i l t s t o n e u s u a lly
grades upward in to g re y-g ree n s h a le o r f in e -g r a in e d sandstone.
S h a le , which is the most common l i t h o l o g i c type in the map
a re a , is c h a r a c t e r is t i c a l ly g re e n -g re y , s p l i n t e r y , o c c a s io n a lly
c a lc a re o u s , s ilic e o u s , the re s is ta n c e in c re a s in g w ith th e s i l i c a
c o n te n t.
D ark-g rey s h a le is common near the c o n ta c t w ith th e Bear
R iv e r Form ation.
P o rc e la n ite is an o th er ty p ic a l lit h o lo g y o f the Aspen.
It
is v a r ic o lo r e d , o c c u rrin g in b lu e , p in k , g re e n , g re y , r e d , and b lu e grey hues.
It
is commonly banded, s p o tte d , and s p e c k le d , and is
e it h e r found as s in g le w e ll-d e v e lo p e d beds or as t h in in te rb e d s w ith in
sandstone and s ilic e o u s s h a le .
I t is composed o f c r y p t o c r y s ta llin e
q u a rtz and breaks w ith a cor.choidal o r s p lin t e r y f r a c t u r e .
The most
common and d i s t in c t i v e p o r c e la n ite is the s p o tte d type t h a t occurs
as amygdules o f grey in a w h ite background o r v ic e v e rs a .
Ju s t to
the n o rth o f th e map a r e a , the Aspen has been subdivided in to low er
and upper u n its by U .S .G .S . g e o lo g is ts on the basis o f a th ic k bed
79
Figure 13.
Photomicrographs o f sandstone from upper sandstone u n it
in lower Bear R iv e r Formation (upper photograph) and
Aspen Shale (lo w e r photograph).
Note clean n atu re o f
sandstone in Bear R iver as opposed to sandstone in Aspen
S h ale.
C o n stitu en ts are (c ) c h e rt and (q ) q u a rtz .
Also
see Table I f o r volume a n a ly s is o f g ra in c o n s titu e n ts
o f these sandstones.
80
o f th e sp o tted type p o r c e la n ite which occurs near th e m id dle o f the
Aspen th e r e .
In the map a r e a , however, t h is p o r c e la n ite bed pinches
out and the Aspen has been mapped as a s in g le u n i t .
Although the
in d iv id u a l p o r c e la n ite beds a re t h i n , s e v eral occur to g e th e r in *
" p o rc e la n ite zone" about 2 ,0 0 0 f e e t above th e Bear R iv e r , t h a t could
have been used as a m arker h o rizo n in much o f th e e a s te rn p a r t o f th e
c e n tr a l outcrop b e lt ( P I.
I).
S tr u c tu r a l involvem ent o r l a t e r a l
t h in ­
ning may have prevented t h is zone from being observed in th e w estern
p a r t o f the map a re a .
An e x c e lle n t exposure o f th e conglom erate occurs t w o - f if t h s
o f a m ile upstream from the mouth o f F ir e Box Creek where i t
exposed on th e e a s te rn w a ll o f the canyon ( P I .
I).
is •
I t crops o u t as
conglom erate lenses up to 4 f e e t t h ic k w ith in a conglom erate sand­
sto n e , th a t has a t o t a l th ic kn ess exceeding 7 f e e t .
The conglom erate
is exposed d is c o n tin u o u s ly along s t r ik e and in d iv id u a l beds pinch out
w it h in s e v eral hundred f e e t .
Exposures a re found in both the north
and south p o rtio n s o f the map a r e a , on both sides o f th e L i t t l e Greyn
R iv e r in the c e n tr a l outcrop b e l t , and north o f th e r i v e r in the
w estern outcrop b e l t .
p a r t o f the Aspen.
The conglom erate c le a r ly occurs in the upper
In th e map a r e a , on the w est s id e o f the L i t t l e
Greys a n t i c li n e i t is exposed ap p ro x im a te ly 3 ,0 0 0 f e e t above the base
o f the Aspen.
Reconnaissance work in th e c e n tr a l outcrop b e l t
81
suggests th a t the conglom erate may occur as a s e rie s o f lenses w ith in
a broad horizon from 500 to 1 ,0 0 0 f e e t t h ic k .
The conglom erate in th e hand specimen is id e n t ic a l to the
conglom erate w ith in th e o v e rly in g F r o n tie r Form ation which is exposed
in the area a d ja c e n t to the Pine Creek Quadrangle ( A lbee, 1975,
personal com m unication).
I t c o n s is ts m ain ly o f w e ll-ro u n d e d pebbles
o f g re y , brown, and w h ite c h e r t , and w h ite and brown q u a r t z it e
(F ig u re 1 4 ).
No lim esto n e pebbles were n oted, which a re t y p ic a l o f
the F r o n tie r conglom erate in the Garns Mountain Quadrangle n o rth o f
th e map area (S ta a tz and A lb e e , 1 9 6 6 ).
The average pebble is h inch
in d iam eter but they range up to 2 h inches.
The m a trix volume is
20 p erce n t in the t i g h t l y packed conglom erate and t h is in crease s to
8 0 -9 0 p erce n t in th e co n g lo m eratic sandstone.
S o rtin g o f th e pebbles
ranges from very good to m oderate w ith the la r g e s t pebbles o c c u rrin g
in th e most p o o rly so rte d conglom erate.
The sandstone a s s o c ia te d w ith
the conglom erate is g r e y - b u f f , medium- to c o a rs e -g ra in e d , sub angular,
o c c a s io n a lly calcareous and cross-bedded, f e ld s p a th ic (up to 10
p e r c e n t), and s tro n g ly r e s is t a n t .
The sandstone u n i t i s not c o n tin u ­
ous along s t r ik e and is p rese n t o n ly where th e conglom erate beds a te
t h ic k e r a t F ir e Box Creek and on the w estern border o f the map area
( P I.
I).
A t o th e r l o c a l i t i e s
the conglom erate forms a r e s is t a n t 2
to 4 fo o t bed between in terb ed d ed s ilic e o u s s h a le , p o r c e la n it e , and
g re y -g re e n , " s a l t and pepper" sandstone.
82
Figure 14.
Chert pebble conglom erate in upper Aspen.
83
Reconnaissance work by th e w r i t e r so u th east o f th e study area
in the Deer Creek and P ic k le Pass quadrangles ( H g .
2) in d ic a te s t h a t
th is conglom erate is most c o r r e c t ly in te r p r e te d as a tongue o f the
Upper Cretaceous F r o n tie r Form ation (F ig . 1 1 ).
The conglom erate can
be tra c e d along s t r ik e to the P ic k le Pass Quadrangle where y e llo w is h orange sandstone o f F r o n t ie r c h a ra c te r is found both above and below
beds o f pebbly conglom erate id e n t ic a l to th a t in th e nap a re a .
The
asso ciated sandstone h o rizo n pinches o u t northw ard, a p p ro x im a te ly
I h m iles south o f th e L i t t l e
Greys R iv e r.
North o f th e Pine Creek
Q uadrangle, t h is in te rto n g u in g r e la tio n s h ip is le s s c le a r .
In the
Garns Mountain Q uadrangle, S ta a tz and Albee (19G 5, p. 72) placed the
low er c o n ta c t o f th e F r o n t ie r a t th e base o f a p ro m in en t, r id g e jrOvmingl fe ld s p a th ic sandstone which is probably th e same as t h a t
used by LaRocque and Fdvards (1 9 5 4 ) in the W illo w Creek area two m iles
n o rth e a s t o f th e mop a re a .
However, in th e Munger Mountain Quadrangle,
AlLee (1968 ) c a lle d beds above the fe ld s p a th ic sandstone Aspen Shale
and placed the basal c o n ta c t o f th e F r o n tie r Form ation ap p ro xim ately
2 ,0 0 0 f e e t h ig h e r in the s e c tio n a t a pebbly conglom erate bed
ass o ciated w ith th e ty p ic a l y e llo w is h -o ra n g e w eath erin g sandstone.
This r e la tio n s h ip suggests t h a t th e re may be a fa c ie s change between
the fe ld s p a th ic sandstone and th e conglom erate o r th a t in te rto n g u in g
is o cc u rrin g between Munger M ountain and Cams M ountain.
Another
example o f in te rto n g u in g between th e Aspen Shale and F r o n tie r
84
Formation occurs in the v i c i n i t y o f Cumberland Gap ap p ro xim ately 100
m iles south o f th e Pine Creek Q uadrangle.
South o f Cumberland Gap,
the co n ta c t between th ese u n its i s e a s ily d is c e rn a b ie where the s i l v e r
grey hogbacks o f p o r c e la n ite and s ilic e o u s sandstone o f th e Aspen
Shale a re c le a r ly d i v i s ib l e from th e n o n s ilic e o u s , b u f f sandstone and
medium-grey s h a le o f the F r o n tie r Form ation.
North o f Cumberland
Gap, however, p o r c e la n ite and p o r c e la n it ic s i U s to n e crops o u t in th e
basal F r o n tie r and th e c o n ta c t between these fo rm a tio n s is much less
d e f i n i t i v e , suggesting in te rto n g u in g .
These r e la tio n s h ip s su g g est, t h e r e f o r e , t h a t in te rto n g u in g
occurs between th e basal p a r t o f th e F r o n tie r Formation and th e top
o f the Aspen S h a le , im p lyin g t h a t these u n its a re p a r t ia l tem poral
e q u iv a le n ts .
F u rth e r s tu d ie s on th e f o s s ils and s tr a tig r a p h y o f
these form ations a re needed to s u b s ta n tia te t h is th e o ry .
The Aspen Shale shows no im p o rtan t fa c ie s v a r ia t io n s in the
re g io n around th e map a re a .
In g e n e r a l, i t has been described by
Rubey (1931 ) as c o n ta in in g p r o p o r tio n a te ly more u n s i l i c i f i e d sh a le
and sandstone than the Mowry Shale and th e conspicuous p o r c e la n ite
beds have less nonvolcanic d e b ris than those in th e Mowry.
The
i '
Aspen in the reg io n a d ja c e n t to th e Pina Creek Quadrangle co n tain s
more sandstone than th e Aspen in southw estern Wyoming ( Reeside and
Cobban, 1960, F ig . 3 ) .
West o f th e map a r e a , th e interb edded
85
sandstone and sh a le beds o f th e Wayan Form ation a re not s i g n i f i c a n t l y
d i f f e r e n t than those o f the Aspen Shale ( M o r it z , 1 9 5 3 ).
Environment o f D e p o s itio n .
As the E a rly Cretaceous tr a n s ­
gression o f the A r c tic sea c o n tin u e d , the m arginal m arine environm ent,
recorded in th e Bear R iv e r s t r a t a changed to more open m arine co n d i­
tio n s during d e p o s itio n o f th e Aspen S h ale.
M a rin e , b ra c k is h , and
fre s h w a te r faunas have been c o lle c te d from th e Aspen in th e W illo w
Creek a re a , 2 m ile s n o rth e a s t o f th e map area (LaRocque and Edwards,
195 4).
In the study a r e a , open nea r-sh o re m arine c o n d itio n s p re ­
v a ile d and the a lt e r n a t in g sequence o f sandstone and sh a le suggests
th a t the base le v e l flu c tu a te d c o n s id e ra b ly .
A rg illa c e o u s and
arenaceous fr a c tio n s a re not mixed as d uring d e p o s itio n o f th e low er
Bear R iver in th e map a r e a , suggesting t h a t wave and bottom c u rre n ts
were probably e f f e c t i v e in tra n s p o r tin g and r e d is t r ib u t in g th e f i n e ­
grain ed sedim ent.
A s e rie s o f o ffs h o re bars was
p robably c o n tin u a lly
being developed and destroyed by th e increased wave a c t i v i t y due to
f lu c tu a tin g w a te r depth.
Shale was dep osited in th e q u ie t w a te r o f
lagoons and o ffs h o re in deeper w a te r.
On th e s h o r e lin e , beach s e d i­
ment was reworked by c u rre n ts and wave a c tio n .
Lakes and lagoons,
th a t were p e r io d ic a lly b a rre d , e x is te d m arginal to th e s h o re lin e .
V o lca n ic a c t i v i t y increased d u rin g d e p o s itio n o f th e Aspen Shale
and v o lc a n ic e je c ta was in t e r m i t t e n t l y d ep osited in th e b as in .
86
Rubey ( lv 2 9 ) a t t r ib u t e d th e high s i l i c a c o n ten t o f the Mowry Shale to
v o lc a n ic ash but suggested t h a t th e sh a le was enriched in s i l i c a by
chemical p r e c ip it a t io n from sea w a te r in the presence o f decaying
org an ic m a tte r.
E ic h e r (1 9 6 2 ) suggested th a t much o f the sand and
s i l t su p p lied to th e basin may a ls o be v o lc a n ic shards in s te a d o f
te rrig e n o u s e la s t ic s .
Gravel was su p p lied to th e map area d u rin g the c lo s in g stages
o f Aspen d e p o s itio n as a consequence o f a stro n g te c to n ic pu lse and
r e s u ltin g p ro g ra d a tio n .
The conglom erate and con glom eratic sandstone
suggest a f l u v i a l type d e p o s it in which the g ra v e l accumulated as
lag d e p o s its .
P a rt o f th is conglom erate may have been reworked as
stran d l in e d ep o sits evidenced by th e sharp l it h o l o g i c break and lack
o f channeling ass o ciated w ith some o f th e conglom erate (sec D a r r e l l ,
192 9).
The s e d im e n ta ry -te c to n ic p a tte r n e x is tin g d u rin g d e p o s itio n
o f th e Aspen Shale was s im ila r to t h a t o f the Bear R iv e r , namely th a t
the Aspen accumulated as a d e lt a sequence w ith m arginal t e r r e s t r i a l
d e p o s itio n .
I t was, however, g e n e r a lly c h a ra c te riz e d by a s l i g h t l y
g r e a te r depth o f w a te r and more open m arine c o n d itio n s as w e ll as
increased te c to n ic a c t i v i t y .
87
Cenozoic Rocks
Cenozoic s t r a ta in th e map area in c lu d e Q uaternary la n d s lid e
and te r ra c e d e p o s its , a llu v iu m and c o llu v iu m , and a lo c a l conglom erate
and b re c c ia u n it .
The la n d s lid e s a re th e most s p e c ta c u la r Q uaternary
fe a tu r e in th e area and are alm ost w ith o u t e x c e p tio n co n fin ed to
the Cretaceous sh a le o f the Bear R iv e r and Aspen fo rm a tio n s .
The
conglom erate and b re c c ia a re ass o ciate d w ith th e o ld e r B a ile y Creek
la n d s lid e .
The t e r r a c e , a llu v iu m , and co llu viu m u n its a re stresm -
and r iv e r - r e l a t e d d e p o s its .
Conglomerate
The Conglomerate is exposed along th e e a s t s id e o f B a ile y
Creek from near the con fluence w ith Dry Wash to a p p ro xim ately 1 .2
m iles upstream , dropping 350 f e e t in e le v a tio n over i t s h o riz o n ta l
d is tan ce ( P I.
I).
I t forms a r e s is t a n t ledge ap p ro x im a te ly 20 f e e t
th ic k a t i t s maximum which th in s upstream .
At the exposure near Dry
Wash the lower 5 f e e t is unsorted and ungraded, and i t becomes more
so rted and graded in .t h e upper 14 f e e t .
I t is composed alm ost
e x c lu s iv e ly o f subangular to a n g u la r blocks o f Madison lim estone and
W ells q u a r t z it e .
2 f e e t in d ia m te r.
They range in s iz e from pebbles to boulders up to
The more so rte d p o rtio n s a re composed o f 3 inch
cobbles in a calcareous m a trix .
88
B reccia
The b re c c ia u n it crops o u t on th e n o rth w a ll o f a small
canyon in th e m iddle o f th e B a ile y Creek la n d s lid e ( P I .
I).
I t is
composed p r in c ip a lly o f a n g u la r, unsorted c la s ts o f Madison lim esto n e
and W ells q u a r t z it e alth ough th e re a re a ls o a few cobbles o f Nugget
and Ankareh sandstone.
I t is u rs o rte d and u n s t r a t if i e d w ith c la s ts
to 2 f e e t in diam eter (F ig . 1 5 ).
The m a trix c o n te n t, which approaches
30 percen t in volume, is composed o f salmon c o lo re d , calcareo u s mud­
stone.
The d e p o s it is not o ver 3 f e e t t h ic k and has an ap p aren t d ip
o f 5 degrees to th e e a s t ( F ig . 3 ) .
Colluvium
Colluvium as shown on P la te I in cludes s e v e ra l d i f f e r e n t
types o f unconsolidated sediments from s o il to g ra v e l and ta lu s
d ep o sits th a t cover th e low er slopes o f the h i l l s
stream courses.
and mountains along
Much o f th e c o llu v iu m is d ep o sited along the L i t t l e
Greys R iv e r , formed from th e d is in te g r a tio n o f sandstone and shale
o f th e Aspen and Bear R iv e r fo rm a tio n s .
A lluvium
A lluvium in the map area in c lu d es c la y - to b o u ld e r-s iz e d
d e t r it u s deposited in the Holocene as bars along stream courses.
39
Figure 15.
B reccia u n it exposed in canyon w ith in B a ile y Creek
la n d s lid e d e p o s its .
Also see F ig u re 3.
90
Terrace Deposits
T errac e dep osits as mapped along f l a t ly in g areas a d ja c e n t
to the Snake R iv e r a re o f two d i f f e r e n t ages (see Geornorpholcgy
S e c tio n , page 6) but in c lu d e b o u ld er to s i l t s ize d fragm ents.
w ell-ro u n d ed boulders c o n s is t o f d u rab le P a le o zo ic and Mesozcic
q u a r t z it e and sandstone.
The
STRUCTURAL GEOLOGY
Regional S tru c tu re
The study area l ie s
C o rd ille re n o v e rth ru s t b e l t .
in th e w estern Wyoming s a l i e n t o f the
The rocks o f t h is area a re u n lik e many
in o th e r w e ll known th r u s t b e lts in t h a t they have undergone K t t i c
metamorphism o f even th e lo w e st grade ( Rubey and H u b b ert, 1 9 5 9 ).
In a d d itio n , c r y s t a l li n e basement rock has played a p assive r o le and
is not in vo lved in any o f the th r u s ts .
The o v e rth ru s t b e l t emerges
from beneath the b a s a lts o f th e Snake R iv e r P la in , tren d s south o f
the Teton Range to the l a t i t u d e o f Jackson, and fo llo w s southward
along both sides o f the Idaho-Wyoming s t a t e l in e to LaBarge, Wyoming
where i t turns southwestward and e n te rs Utah e a s t o f th e southw estern
corner o f Wyoming and n o rth o f th e U in ta Range.
T his a rc u a te b e l t
is about 60 m iles in w idth and 250 m iles in le n g th along a curving
arc o f 120 degrees ( Rubey and H u b b ert, 1 9 5 9 ).
I t is i n d i s t i n c t l y
bounded on th e w est b u t is bordered on th e e a s t by the Green R iv e r
Basin.
The th r u s t b e l t is composed o f s u b p a ra lle l mountain ranges
th a t are g e n e ra lly bordered on th e e a s t by m ajor th r u s t f a u l t s and
on the west by h ig h -a n g le normal o r re v e rs e f a u l t s .
Between these
m ajor bordering f a u l t s , the s t r a t a a re deformed by m inor t h r u s ts ,
la rg e and small f o ld s , and diagonal tra n s v e rs e f a u l t s
H ubbert, 195 9).
( Rubey and
92
M ajor o v e rth ru s t f a u l t s in th e o v e rth r u s t b e l t a r e , from w est
to e a s t, th e P a r is , Meade, C raw ford, Absaroka, Darby, P ro sp ect, and
Hogsback (F ig . 1 6 ) , in app arent age sequence w ith the o ld e r th ru s ts
on th e w est (Armstrong and O r i e l , 1 9 6 5 ).
The p r in c ip a l movement on
these th ru s ts ranges from l a t e s t J u ra s s ic t c m id -E a rly Eocene
(Armstrong and O r i e l , 1 9 6 5 ).
S t r a t ig r a p h ic throw on each o f th e
m ajor th ru s ts is about 2 0 ,0 0 0 -2 5 ,0 0 0 f e e t (C rosby, 1968) and they
in v o lv e s u c c e s s iv e ly younger s t r a t a to th e e a s t (Armstrong and O r i e l ,
1 9 6 5 ).
Rubey and Hubbert (1 9 5 9 , p. 187) have estim a te d h o r iz o n ta l
movement to be on th e o rd e r o f 10-15 m ile s , based on c a r e f u l ly drawn
s tr u c tu r e s e c tio n s .
A lt e r n a t iv e in te r p r e ta t io n s by them suggest t h a t
minimum movement may be about 5 -8 m ile s and maximum displacem en t may
be as g re a t as 2 0 -3 0 m ile s .
Although th ey commonly in t e r s e c t the
s u rfa c e a t h ig h e r a n g le s , th e o v e rth ru s ts are bedding p lan e t h r u s t s ,
evidenced by the p a r a lle lis m o f f a u l t and s t r a t ig r a p h ic su rfaces
across e x te n s iv e areas (C rosby, 1 9 6 8 ).
Stresses re s p o n s ib le f o r th e d eform ation o f the o v e rth ru s t
b e l t may be c a te g o riz e d as e i t h e r boundary fo rc e s o r body fo rces
(C rosby, 1 9 6 9 ).
Boundary fo rc e s may be equated to re g io n a l compres­
s io n , a "push from th e r e a r"
g r a v it a tio n a l s lid in g .
(C rosby, 1 9 6 9 ), and body fo rces to
Rubey and Hubbert (1 9 5 9 ) r e je c t e d a p u re ly
g r a v it a tio n a l g lid in g o r re g io n a l compression o r ig in f o r f a u lt s in
th e o v e rth ru s t b e l t , as u n te n a b le , based on ap p aren t absence o f
I
I
Figure 16.
T ecto n ic map o f north end o f the o v e rth ru s t b e lt .
P rin c ip a l th ru s ts are la b e le d ; sawteeth on upper p la te
( a f t e r Armstrong and O r i e l , 1965, Crosby, 1 9 6 8 ).
Pine
Creek area shaded.
94
p u ll- a p a r t r i f t s
t h a t should be developed in g r a v it y s lid e s and th e
nonexistence o f any ro o t t h a t could have produced th e re q u ire d shallow
compressive s tr e s s .
They concluded t h a t the most l i k e l y mechanism
may have been a com bination o f the two fo rc e s .
Crosby (1 9 6 9 ) l i k e ­
w ise rep u d iated a boundary fo rc e o r ig in m ostly on th e same la c k o f
any p hysical boundary a t th e back o f the s a l i e n t .
In s te a d , Crosby
(1968 ) proposed th a t g r a v it a t io n a l g lid in g was th e mechanism o f
d efo rm atio n .
He p o s tu la te d th e presence o f an u p l i f t w ith an apex
t h a t roughly c o in cid ed w ith th e depocenter o f th e maximum th ickn esses
o f P aleo zo ic and Mesozoic s t r a t a in sou theastern Idaho.
This a r e a ,
according to him, rose in response to is o s t a t ic rea d ju s tm e n t.
High
pore press u res, developed d u rin g th e e a r l i e r d e p o s itio n a l phase,
enabled th e sedim entary pack to move away from th e high in a r a d ia l
and d iv e rg in g p a tte r n (C rosby, 1969) under a p u re ly g r a v it a t io n a l
in flu e n c e .
L a te r e ro sio n o f th e high would e f f e c t i v e l y remove the
pul I - a p a r t gaps o r r i f t s , th e la c k o f which Rubey and Hubbert (1959 )
used to d is q u a lif y th e g r a v it y g lid in g mechanism.
The e a r ly d e p o s itio n a l phase in which the sediments accumu­
la te d in the m io geosynclinal p o rtio n o f th e g eo syn clin e was fo llo w e d
by th e two p a r t d e s tru c tio n a l phase known as th e Laramide Orogeny.
E a rly th r u s tin g and fo ld in g was succeeded by b lo c k f a u lt in g which
began in the Eocene and has continued to th e Recent.
Recent move­
m ent, on both north and e a s t-tr e n d in g f a u l t s e t s , is in d ic a te d by
95
broken a l lu v ia l fa n s , d is p la c e d b a s a lt flow s le s s than 2 7 ,0 0 0 years
o ld , and earthquakes (Armstrong and O r i e l , 1 96 5).
Local S tru c tu re
In tro d u c tio n
The map a re a l i e s on th e upper p la te o f th e Darby th r u s t and
th e low er p la te o f the Absaroka th r u s t (F ig .
1 7 ).
The Absaroka th r u s t,
w ith in I m ile o f th e w estern m argin o f th e map a r e a , places Madison
lim esto n e on the Aspen S h ale.
Jobin (1 9 7 2 ) showed t h is f a u l t to be
an extrem ely f l a t t h r u s t , d ip p in g a few degrees to th e w est.
The
Darby t h r u s t , a p p ro xim ately 1 -2 m ile s e a s t o f the map a r e a , has moved
Bighorn Dolom ite over Aspen and Bear R iv e r s t r a t a .
Ross and S t. John
(1 9 6 0 ) in d ic a te d t h a t the d ip o f th e Darby o v e rth ru s t is 30° to 35°
in th e re g io n a d ja c e n t to th e map a r e a , although t h is p robably re p re ­
sents a n e a r-s u rfa c e phenomenon as th e th r u s t undoubtedly f la t t e n s
a t depth.
Both o f these th ru s ts can be tra c e d tens o f m ile s north
and south o f th e map area ( F ig .
1 6 ).
W ith in th e map a r e a , th e r e is one la r g e f o l d , two sm all
f o ld s , and a la r g e re v e rs e f a u l t , a l l o f which a re r e la te d to the
e a r l i e r congressional phase o f th e Laramidc Orogeny.
These s tru c tu re s
fo llo w th e re g io n a l northw est tre n d and, as found elsew here in th e
o v e rth r u s t b e l t , th e fo ld s a re m o d erately to s tr o n g ly o v e rtu rn ed to
th e e a s t.
Three sm all cross f a u l t s a re a ls o found in th e map area
96
I- 0<WI D
Figure 17.
S tru c tu re map o f Pine Creek Quadrangle and a d ja c e n t a re a .
Map area shaded.
Geology by Jobin (1972 ) on w est; Ross
and S t. John (1 9 6 0 ), e a s t; Albee (u n p u b .), n o rth .
97
which a re contemporaneous w ith o r post date the f o ld in g - t h r u s t in g
phase.
In a d d itio n to these s tr u c t u r e s , fo ld s a re p robably p re s e n t
in th e s o u th -c e n tra l p a r t o f th e map area where the Aspen Shale is
exposed.
The Aspen here is n e a rly 7 ,0 0 0 f e e t t h ic k when measured
from th e e a s te rn c o n ta c t w ith the Bear R iv e r to th e tra c e o f the
L i t t l e Greys f a u l t ( P I .
I).
Albee (1968 ) approxim ated th e thic kn ess
o f Aspen Shale a t 4 ,0 0 0 f e e t in th e Hunger Mountain Q uadrangle to
th e n o rth , in d ic a tin g th a t ro u g h ly 3 ,0 0 0 f e e t o f s e c tio n is repeated
in the s o u th -c e n tra l p a r t o f the map a re a .
p a r t ly be due to f a u l t i n g .
This d iscrep an cy may
However, th e evidence in the a d ja c e n t
areas suggests t h a t o vertu rn ed fo ld in g is probably re s p o n s ib le f o r
th e excessive th ic k n e s s o f Aspen.
One evidence o f fo ld in g may be
th e two s m a ll-a m p litu d e fo ld s mapped along th e Snake R iv e r ( F ig .
which could extend to th e s o u th -c e n tra l p a r t o f th e map a re a .
17)
This
im p lie s t h a t these fo ld s become s tro n g ly o v e rtu rn ed in the a p p ro x i­
mate m iddle o f th e Pine Creek Q uadrangle.
A l t e r n a t e ly , Schroeder
(1 9 7 5 , personal com m unication) mapped a la rg e o ve rtu rn ed s y n r lin e in
the P ic k le Pass Quadrangle to th e so u th east ( F ig .
2 ) whicn may
co n tin u e to the s o u th -c e n tra l p a r t o f the map a re a .
U n fo r tu n a te ly , th e re i s no stro n g f i e l d
evidence such as
fo ld in g o r o vertu rn ed bedding in th e s o u th -c e n tra l p a r t o f th e map
area to support t h is th e o ry .
It
is l i k e l y , however, th a t crum pling
98
and deform ation has occurred in th e incom petent sandstone and shale
o f the Aspen which r e s u lte d from d eform ation o f th e a d ja c e n t L i t t l e
Greys a n t ic lin e and r e la te d f a u l t .
F a u ltin g
Normal F a u lts .
Three sm all t e a r f a u l t s occur in the map a r e a ,
two o f which a re lo c a te d on th e w est fla n k o f th e L i t t l e Greys a n t i ­
c lin e .
These f a u lt s tre n d ap p ro x im a te ly N 35° to 65° W and th e s t r ik e
s l i p o f f s e t has been on th e o rd e r o f 100 to 200 f e e t .
over 1 ,2 0 0 f e e t in le n g th .
N e ith e r a rc
They appear to be c lo s e ly r e la te d in
both tim e and in the mechanics o f t h e i r fo rm a tio n and I suggest th a t
they a rc contemporaneous w ith th e f o l d , form ing on th e f la n k o f the
L i t t l e Greys a n t i c li n e from sim ple s tre s s re le a s e as the fo ld
developed.
The t h ir d f a u l t , v i s i b l e from U .S . Highway 2 6 -8 9 , l i e s
near the n o rth e a s te rn c o rn e r o f th e map a re a .
T his f a u l t tren d s
N 40° E and th e d i p - s l i p movement o f f s e t th e Craney and Peterson
lim estones ap p ro xim ately 5 0 -75 f e e t .
Reverse F a u lts — L i t t l e Greys F a u lt .
The f a u l t t h a t runs
e a s t o f th e a x is o f the L i t t l e
Greys a n t i c li n e ( F ig .
named th e L i t t l e Greys f a u l t .
I t tre n d s a p p ro x im a te ly N 20° W and
its
17) is here
tra c e is p a r a l l e l to th e o v e r a ll s tr u c t u r a l g ra in o f th e a re a .
The le n g th o f the f a u l t is in excess o f 4 m iles w ith in the map area
and i t extends a t le a s t 3 m ile s south o f the L i t t l e Greys R iv e r.
99
N orthw ard, t h is f a u l t may connect w ith one mapped by A lte e (1 9 7 5 ,
personal communication) t h a t continues in to th e Hunger Mountain
Quadrangle ( F ig . 1 7 ).
More d e f i n i t i v e d e t a il is not p o s s ib le as
th e f a u l t l i e s e n t i r e l y w it h in th e Aspen S hale which is n o t separated
in to low er and upper u n its in the map area as i t has Leen t c the n o rth
(see. s e c tio n on Aspen S h a le , page 7 4 ) .
S tr u c tu r a l d efo rm atio n in th e beds a d ja c e n t to the tra c e o f
th e f a u l t im ply i t s
e x is te n c e .
E r r a t ic dips a re common in th e s t r a t a
n ex t to the f a u l t .
Two m ile s south o f th e L i t t l e Greys R iv e r , over
a 150 fo o t h o riz o n ta l d is ta n c e , th e s t r ik e o f th e beds is c o n s is te n t
but the dips a re 55° W, 22° W, 6 5 ° W, v e r t i c a l , and 55° W from w est
to e a s t, r e s p e c tiv e ly .
In a d d it io n , v e r t ic a l to o vertu rn ed beds occur
along the f a u l t tra c e in the rid g e j u s t to th e e a s t o f the mcuth o f
Cow Camp Creek w ith the L i t t l e Greys R iv e r ( P I .
I).
V e r t ic a l to
overturned bedding is ap p aren t n o rth o f th is l o c a l i t y as w e ll
( P I.
I).
The f a u l t is a ls o suggested by th e ap p aren t tru n c a tio n o f a s y n c lin e
mapped by Albee (1 9 7 5 , personal communication) d i r e c t l y e a s t o f
S ta tio n Creek, n o rth o f th e Snake R iv e r (F ig .
1 7 ).
This s y n c lin e
trends d i r e c t l y in to th e sm all a n t i c l i n e w est o f Pine Creek in the
map a re a .
The s y n c lin e mapped by Albee is a p p a re n tly th e same
s y n c lin e mapped south o f the Snake R iv e r ( F ig .
17) and the o f f s e t is
a r e s u lt o f e ro s io n o f th e upthrown s id e o f th e f a u l t .
A d d itio n a l
evidence f o r the f a u l t was noted by N ig e r (1 9 5 5 ) who mentioned th a t
ICO
in a t e s t d r i l l e d a t th e southern end o f th e L i t t l e Greys a n t i c li n e
ju s t to th e n o rth o f the L i t t l e
Greys R iv e r , th e h ole bottomed in
th e Woodside Form ation a f t e r f a u l t i n g o u t o f what was in te r p r e te d
to be the Phosphoria Form ation.
S t r a t ig r a p h ic evidence a ls o supports the e x is te n c e o f the
fa u lt.
The th ickn ess o f Aspen Shale is ap p ro xim ately 8 ,5 0 0 f e e t when
measured across th e southern end o f the c e n tra l outcrop b e l t ,
exceeding tw ic e th e th ickn ess o f Aspen (4 ,0 0 0 f e e t ) in the Hunger
Mountain Quadrangle ( A lbee, 1568) to th e n o rth .
If
i t can be assumed
t h a t a f o ld rep ea ts 3 ,0 0 0 f e e t o f s e c tio n e a s t o f th e L i t t l e Greys
f a u l t (see Local S tr u c tu r e , In tr o d u c tio n , page 5 5 ) then th e throw is
c o n s e rv a tiv e ly estim a te d a t 1 ,5 0 0 f e e t .
The d ip o f th e L i t t l e Greys f a u l t in creases to the so u th .
Bedding dips in d ic a te t h a t th e f a u l t plane dips 4 0 ° to 60° in th e
north and 6 0 ° to 8 0 ° in th e so u th .
These amounts a re not re p re s e n ta ­
t i v e o f the s te e p e r in te r s e c t io n a t th e s u rfa c e p a r t i c u l a r l y in the
south where th e f a u l t plan e is v e r t i c a l .
It
is suggested t h a t the
d iffe r e n c e in th e d ip o f th e f a u l t along th e tra c e is due p r im a r ily
to i t s p ro x im ity t o th e Absaroka th r u s t where o v e rtu rn in g in creases
on the a d ja c e n t L i t t l e Greys a n t i c l i n e a t th e n o rth end o f th e map
area (F ig .
1 6 ).
The L i t t l e Greys f a u l t p ro b ab ly developed as a " s tre tc h
th r u s t"
(Bacigley, 1965, p. 194) r e s u lt in g from weakening o f the
1 01
fo re lim b in th e incom petent Aspen Shale ( F ig . 1 8 ) .
T h is would im p ly ,
th e r e f o r e , th a t th e fo ld in g o f L i t t l e Greys a n t i c l i n e s l i g h t l y p re ­
dates the f a u l t i n g .
Folding
L it t l e
Greys A n t ic lin e .
The L i t t l e Greys a n t i c li n e was f i r s t
mapped by S c h u ltz (1 9 1 4 ) and l a t e r by Boeckerman and E a rd le y (1 9 5 6 ).
The a x ia l tra c e tren d s a p p ro xim ately N 20 W and is exposed over th e
e n t ir e le n g th o f th e map a re a .
J u s t to the n o rth o f th e map a re a th e
f o ld is c u t o f f by th e Absaroka t h r u s t , and th e f o ld f la t t e n s a p p ro x i­
m ately 5 m ile s south o f th e map area (N ig e r , 1 9 5 6 ).
S tr u c tu r a l
clo s u re on t h is s tr u c tu r e has been estim ated to be on th e o rd e r o f
1 ,5 0 0 -2 ,0 0 0 f e e t ( N ig e r , 1 9 5 5 ).
The L i t t l e Greys a n t i c li n e is complex throughout i t s
o f exposure w it h in th e map a re a .
le n g th
In th e southern p a r t o f th e map
a r e a , small fle x u r e s a re p re s e n t on both lim bs ( F ig . 2 0 ).
A t the
southern border o f th e map area along the L i t t l e Greys ro a d , a s m a ll,
t i g h t l y fo ld e d s y n c lin e developed on th e e a s te rn lim b w ith in 300 f e e t
o f n e a rly h o r iz o n ta l beds ( F ig .
1 9 ).
One m ile northw est o f th is
l o c a l i t y , g e n tly d ip p in g Stump and Preuss sandstone and low er G annett
s t r a t a a re exposed on th e w estern lim b where slope angles exceed the
d ip ( P I.
I).
Boeckerman and E a rd le y (1 9 5 6 , p. 182) suggested th a t
102
incomoetcnTcoiYtperefflT
Figure 18.
Development o f the L i t t l e Greys a n t ic lin e and associated
fa u lt.
As s tre s s (—») was a p p lie d , th e competent sand­
stone in the lower Bear R iver Form ation, and the o v e rly in g
incom petent sh a le o f the upper Bear R iv e r and Aspen Shale
(A) were b ro ad ly fo ld ed ( B ) . As s tre s s c o n tin u e d , the
s t r a ta became overturned and s tre tc h in g occurred in the
shale sequence (C ).
Note th a t very l i t t l e s tre tc h in g
occurs in the competent sandstone.
E v e n tu a lly the sand­
stone f a il e d and the f a u l t developed (D) ( a f t e r B adgley,
1964).
103
Figure 19.
L i t t l e Greys a n t i c l i n e , view towards th e n o rth .
Bedding
planes are accen tu ated .
Note small s y n c lin e on eastern
limb and la n d s lid e in core ( o u t lin e d ) .
Formations are
( j t ) Twin Creek Lim estone, ( J s p ) Stump and Preuss sand­
sto n es, and (Kgi) low er Gannett Group.
104
NORTH
SOUTH
F ig u re 20.
Composite o f d ips taken across L i t t l e Greys a n t i c li n e a t
n o rth end along Snake R iv e r , and south along northw estern
tre n d near top o f E lk M ountain. A n t ic lin e o vertu rn ed a t
n o r th , r e f le c t i n g i t s p ro x im ity to Absaroka t h r u s t .
Not
to s c a le .
105
t h is f la x u re is p a r t o f th e M idd le Ridge s y n c !ir e which increases in
magnitude to th e south.
The a n t i c li n e is m o derately asymmetric in th e south w ith dips
on the w estern lim b averag in g 45° and those on th e e a s t lim b averaging
6 0 °.
In th e m iddle o f th e map a r e a , the a n t i c li n e becomes s tro n g ly
overturned to the e a s t where both e a s te rn and w estern limbs d ip 4 0 °
to the w est.
Northw ard, th e o v e rtu rn in g is somewhat less w ith dips
on th e eas te rn lim b on th e o rd e r o f 4 0 ° to 60° W.
w estern lim b do not exceed 25° to 3 0 ° W.
Those on th e
O n e -h a lf m ile n o rth o f the
study a r e a , th e am p litu d e o f the f o ld g r e a t ly dim inishes as i t g e n tly
plunges beneath th e hanging w a ll o f the Absaroka th r u s t .
Small F o ld s.
A sm all a n t i c li n e and s y n c lin e re p e a t the
Aspen s e c tio n a t th e n o rth -c e n tra I margin o f th e map area ( F ig .
1 7 ).
They tre n d N 30° W and both a re not apparent a m ile to the south.
They plunge ap p ro x im a te ly 14° to the n o r th , determ ined by a measure­
ment o f the a x ia l c r e s t where the a n t i c li n e is exposed along the
Snake R iv e r.
These fo ld s a re s tro n g ly asymmetric w ith dips on the
western lim b averagin g 3 5 ° , and 70° on th e e a s te rn lim b .
ECONOMIC GEOLOGY
Economic resources o f the Pine Creek Quadrangle in c lu d e
phosphate ro ck* g r a v e l, r ip r a p , road m e ta l, lim e s to n e , p la c e r g o ld ,
and p o te n tia l petroleum .
The phosphate is co n cen trated in th e Meade Peak and R e to rt
Phosphatic Shale members near the base and top o f the Phosphoria
Form ation.
These p o o rly exposed phosphate beds crop o u t on th e west
fla n k o f Grayback Ridge in th e extreme n o rth e a s te rn co rn er o f th e map
a re a .
The Meade Peak Member is a p p ro xim ately 50 f e e t t h ic k and is
p r in c ip a lly comprised o f in te r c a la te d th in beds o f p h o s p h o rite ,
phosphatic s h a le , mudstone, s i lt s t o n e , and carbonate (J o b in , 1 9 7 2 ).
The p h o sp h o rite occurs as o o l i t e s , p i s o l i t e s , p e l l e t s , and as dense
s tr u c tu r e le s s ty p e s .
The phosphate r ic h beds in th e R e to rt
Phosphatic Shale Member a re very t h in due to p o s t-tie p o s itio n a l ero sio n
(J o b in , 1 9 7 2 ).
The tru e th ickn ess o f th is u n it w ith in th e Pine Creek
Quadrangle is unknown b u t to th e w est in th e F e rry Peak Quadrangle i t
ranges from 1 -6 f e e t .
R e fer to Sheldon (1 9 6 3 ), Albee (1 9 6 3 ), and
Jobin (1 9 7 2 ) f o r a complete a n a ly s is o f PgO^ c o n c e n tra tio n s in these
members in th e area d i r e c t l y a d ja c e n t to th e Pine Creek Q u a d ra n g le .,
These members a re too th in f o r economic development under c u rre n t
c o n d itio n s .
Deposits o f g r a v e l, r ip r a p , road m e ta l, and lim esto n e are
abundant w ith in th e map a re a .
The M ission Canyon Limestone and low er
107
p a r t o f the W ells Form ation p ro v id e r e l a t i v e l y pure Limestone (J o b in ,
1972) although these fo rm atio n s a re confined o n ly to the n o rth e a s te rn
corner o f the map a re a ,
Magnesium r ic h lim esto n e can be q u a rrie d
from th e Draney and Peterson lim estones along th e L i t t l e Greys R iv e r.
Gold bearing g ra v e l from th e te rra c e s along the Snake R iv e r
have been p lacered in t e r m i t t e n t l y f o r more than 100 y e a rs .
Values
averaged 10 to 14 cents a cub ic y ard (A lbee e t a h , 1 97 5).
O il p o te n tia l w ith in th e area is unknown.
The L i t t l e Greys
a n t i c li n e along the L i t t l e Greys R iv e r has been d r i l l e d a t le a s t th re e
tim e s , two o f which a re on re c o rd .
Wiger (1 9 5 5 ) re p o rte d cn these
te s ts both o f which occurred p r i o r to 1951.
The f i r s t t e s t bottomed
in the Thaynes Formation a t 2 ,7 5 2 f e e t and no o i l shows were re p o rte d .
The second t e s t was d r i l l e d to 4 ,6 9 9 f e e t to th e Woodside Form ation
a f t e r f a u lt in g out o f what was in te rp re te d to be the Phosphoria Forma­
t io n .
T his second t e s t had dead o i l s ta in in the Phosphoria (? ) a t
4 ,4 0 0 f e e t in a s l i g h t l y vuggy, su c ro s ic d o lo m ite .
I t is im p o rtan t
to note t h a t a f a u l t , probably the L i t t l e G reys, was in te rs e c te d in
t h is second t e s t .
T h e re fo re , th e L i t t l e Greys a n t i c li n e is probably
a s m a lle r s tr u c tu r a l tra p than was p re v io u s ly th o u g h t.
The probable
overturned fo ld s o c c u rrin g in th e c e n tr a l p a r t o f th e Pine Creek
area (see Local S tr u c tu r e , In tr o d u c tio n , page 95) may p ro vid e
p o te n tia l petroleum tr a p s .
SUMMARY
Three stages are e v id e n t in th e g e o lo g ic development o f the
map a re a .
F i r s t , th e re was an e a r ly d e p c s itio n a l phase in which s e d i­
ment accumulated in the t r a n s it io n a l area between th e m iogeosyncline
on the w est and th e c o n tin e n ta l p la tfo rm on th e e a s t; second, la r g e
n o rth w a rd -tre n d in g th ru s ts and ass o ciated fo ld s were developed; and
t h i r d , the geomorphic development o f th e area in which s e v e ra l p ro ­
cesses in te ra c te d to a l t e r the landform s produced d uring the f i r s t two
phases.
M is s is s ip p ia n — M arine lim estone was dep o sited in th e
m iogeosynclinal and s h e lf areas d u rin g th e E a rly M is s is s ip p ia n advance
o f the sea (Kaun and Kent, 1 96 5).
Regression o f th e sea in l a t e
M is s is s ip p ia n tim e re s u lte d in th e development o f a k a r s t s u rfa c e
on the exposed M ission Canyon Lim estone.
Pennsylvanian — D e tr itu s was d e riv e d from e a s te rn and
western sources and deposited in a m arginal b a s in a l area in south­
e as te rn Idaho which was a p p re c ia b ly more calcareous than i t s m argins.
E p eirog enic u p l i f t g ra d u a lly gave way to a p a r t i a l w ith d raw al o f the
sea in Late Pennsylvanian tim e ( M a llo r y , 1 9 7 2 ).
Permian — Due to te c to n ic movements the Phosphoria sea
tw ic e transgressed and regressed across w estern Wyoming, and m inor
flu c tu a tio n s o f c lim a t ic and oceanographic c o n d itio n s produced
i n t r i c a t e in te rb e d d in g (McKelvey e t a l_ ., 1 9 5 9 ).
109
T r ia s s ic — Two m arine advances d u rin g the E a rly and M iddle
T r ia s s ic r e s u lte d in th e d e p o s itio n o f c l a s t ic and carbonate s t r a t a
o f the Dinwoody and Thaynes fo rm a tio n s .
Between m arine advances
d e lta s were prograd ing westward and northward producing in te rto n g u in g
o f marine and c o n tin e n ta l d e p o s its .
c e n tra l
West o f the b a s in , in sou th-
Idaho, a la rg e n o rth e a s t tre n d in g r id g e rose in e a r ly Late
T r ia s s ic tim e shedding d e t r it u s eastw ard.
J u ra s s ic — The shallow m arine environm ent o f th e Twin Creek
Limestone g ra d u a lly gave way to open m arine c o n d itio n s d u rin g dep osi­
tio n o f th e Upper J u ra s s ic Stump sandstone as the m arine in c u rs io n s
o f tne A r c t ic sea spread s u c c e s s iv e ly f a r t h e r across Wyoming.
high area in s o u th -c e n tra l
The
Idaho again rose in e a r ly Late J u ra s s ic
tim e spreading a l l u v i a l d e t r it u s across th e study a re a .
Cretaceous — The a l l u v i a l fans which developed in th e study
area were g ra d u a lly inundated by another m arine in c u rs io n in m iddle
E a rly Cretaceous tim e .
Although both the Bear R iv e r and Aspen forma­
tio n s were deposited in d e lt a ic and ass o ciated t e r r e s t r i a l environments
th e w ate r depth and v o lc a n ic a c t i v i t y increased d u rin g d e p o s itio n o f
th e Aspen S hale.
Late Cretaceous - E a rly T e r t ia r y — S tr u c tu r a l d eform ation in
the area r e s u lte d from la rg e eastward moving th r u s t p la te s which
emanated from a high area in sou theastern Idaho.
A la r g e fo ld
developed w ith in th e map area from movement on th e a d ja c e n t Absaroka
HO
T h ru s t.
As d efo rm atio n continued th e f o ld Decame o v e rtu rn ed and the
shales o f the Bear R iv e r and Aspen fo rm atio n s were s tre tc h e d .
ment on the L i t t l e
Move­
Greys f a u l t occurred as the sandstone bed in the
upper p a r t o f the lower Bear R iv e r Formation f a i l e d .
Late T e r t ia r y - Q u arte rn ary - -
During M iddle P lio c e n e time,
a la rg e la k e in which f in e g rain ed d e t r it u s was dep osited may have
occupied the study a re a .
The Snake and L i t t l e Greys R ivers could
have developed on t h is basin f i l l
o r la k e le v e l and eroded through
th e u n d e rly in g topography by s u p e rp o s itio n .
During th e P le is to c e n e
a la rg e la n d s lid e o r ig in a te d on th e w est f la n k o f Grayback Ridge and
moved w a te r-s a tu ra te d m a te ria l down B a ile y Creek damming i t and the
Snake R iv e r causing th e bed loads to be deposited upstream .
This
s lid e s u rfa c e was m o d ified o ver tim e and then covered by a second
la n d s lid e t h a t a ls o o r ig in a te d on th e fla n k o f th e rid g e .
NEW CONCEPTS
Several n o ta b le conclusions reg ard in g th e geomorphology,
s tr a tig r a p h y , and s tr u c tu r e o f the Pine Creek area have re s u lte d
from t h is study.
I t is hoped th a t these w i l l c o n tr ib u te to the
general understanding o f th e geology o f the n o rth e rn p a r t o f th e
Wyoming o v e rth ru s t b e l t .
Geomorpholcgy
The B a ile y Creek la n d s lid e o r ig in a te d on th e west f la n k o f
Grayback Ridge w ith in the Madison and W ells fo rm a tio n s , moving d e b ris
down B a ile y Creek.
This re s u lte d in the damming o f B a ile y Creek and
the Snake R iv e r causing th e bed loads to be dep o sited upstream .
The
su rfa c e o f th e s lid e d e b ris was m o d ified over tim e which allo w ed f o r
some o f the d e t r it u s to become l i t h i f i e d .
This s u rfa c e was l a t e r
covered by a second la n d s lid e t h a t als o o r ig in a te d w ith in th e Madison
lim estone and W ells q u a r t z it e .
S tra tig ra p h y
I.
A basal b re c c ia was found w ith in th e Thaynes Formation
which may in d ic a te t h a t a lo c a l shoal e x is te d in th e Pine Creek area
during d e p o s itio n o f the low er p a r t o f t h is u n it .
112
2.
The Draney Limestone o f the Gannett Group is present in
the northw estern p a r t o f th e map area and is absent to the s o u th e a s t,
c o n tra ry to conclusions reached by Eyer (1969 ) who in d ic a te d th a t
th e Draney was p rese n t over the e n t i r e map a re a .
3.
The low er Bear R iv e r sequence, c o n s is tin g o f s i l t s t o n e ,
sandstone, mudstone, and b la c k s h a le is anomalously th ic k and w e ll
developed in th e southw estern p a r t o f the map area on the w est lim b
o f th e L i t t l e Greys a n t i c l i n e .
The t o t a l th ic kn ess (1 ,2 5 0 f e e t ) o f
the Bear R iv e r here is th e g r e a te s t in che Pine Creek Quadrangle and
a d ja c e n t a re a .
4.
A pebbly conglom erate u n it was found w ith in the upper
Aspen Shale in the c e n tr a l and w estern outcrop b e lts and south o f
the L i t t l e Greys R iv e r.
The conglom erate is most c o r r e c t ly i n t e r ­
preted as a tongue o f the o v e rly in g F r o n tie r Form ation to which the
conglom erate can be tra c e d along s t r ik e to th e south.
S tru c tu re
The L i t t l e Greys re v e rs e f a u l t runs e a s t o f the a x is o f the
L i t t l e Greys a n t i c li n e and
rep ea ts
p a r t o f the Aspen s e c tio n .
I t is
l i k e l y , however, t h a t the s o u th -c e n tra l p a r t o f th e map area is
fu r th e r com plicated by o vertu rn ed fo ld in g not e v id e n t in th e ou tcro p .
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S ta n le y , K. O ., W. M. Jordan, and R. H. D o tt J r . , 1971, Mew hypothesis
o f E a rly J u ra s s ic paleogeography and sediment d is p e rs a l f o r
w estern U n ited S ta te s : Amer. Assoc. P e t r o l. G eol. B u l l . , V. 55,
p. 10-19 .
S ta n to n , I . W ., 1892, The s t r a t ig r a p h ic p o s itio n o f th e Bear R iv e r
Form ation: Amer . Jour. S c i. V. 4 3 , p. 9 8 -1 1 5 .
Stokes, W. L . , 1944, M orrison Form ation and r e la te d d ep o sits in and
a d ja c e n t to the Colorado P la te a u :
G eol. Soc. Amer. B u l l . , V. 55,
p. 951-992.
_________, 1961, F lu v ia l and e o lia n sandstone bodies in Colorado
P la te a u , i_n Geometry o f sandstone bod ies: Amer. Assoc. P e tr o l.
G eol. B u l l . , p. 151-178.
S tr ic k la n d , J. W ., 1956, M is s is s ip p ia n s t r a tig r a p h y , w estern Wyoming:
Wyoming G eol. Assoc. Guidebook I l t h Ann. F ie ld C o n f., Jackson
H o le , 1956: p. 5 1 -5 7 .
Thornbury, W. D ., 1969, P r in c ip le s o f geomorphology, 2nd e d . :
W ile y and Sons, I n c . , New Y o rk , 594 p.
John
V eatch, A. C ., 1907, Geography and geology o f a p o rtio n o f south­
w estern Wyoming and s p e c ia l re fe re n c e to coal and o i l :
U .S . G eol.
Survey P r o f. Paper 56, p. 1 -1 7 8 .
Wanle ss , H. R ., R. I . B elknap, and Helen F o s te r, 1955, P a le o zo ic
rocks o f Gros V e n tre , T e to n , Hoback and Snake R iv e r ranges,
Wyoming: G eol. Soc. Am. Mem. 6 3 , 90 p.
W ig er, D. W ., 1956, L i t t l e Greys R iv e r a n t i c l i n e , L in c o ln County,
Wyoming in Wyoming G eol. Assoc. Guidebook I l t h Ann. F ie ld C o n f.,
Jackson H o le , Wyoming, 1956: p. 196-197.
W rig h t, J . C ., and D. D. D ic k e y , 1963, R e la tio n s o f the Navajo and
Carmel fo rm a tio n s in southwest Utah and a d jo in in g A rizo n a :
U .S. G eol. Survey P ro f. Paper 4 5 0 -E , p. 6 3 -6 7 .
123
Wyoming G eological A s s o c ia tio n , 1 9 /1 , S tr a tig r a p h ic nom enclature c h a rt
In^ Wyoming Geol. Asscc. Guidebook 23rd Ann. F ie ld C o n f., Symposium
on Wyoming Tectonics and t h e i r Economic S ig n ific a n c e , 1971: p. 3.
Yen, I . C ., 1952, Age o f th e Bear R iv e r Form ation, Wyoming:
Soc. Amer. B u l l . , V. 6 3 , p. 757-764.
G eol.
APPENDIX
GANNETT GROUP SECTIONS
This p a r t ia l s e c tio n o f the G annett Group is lo c a te d on the
south fa c in g h i l l j u s t to the e a s t o f th e a x is o f the L i t t l e Greys
a n t i c l i n e , d i r e c t l y north o f the L i t t l e Greys Road, and 1 ,0 0 0 f e e t
northw est o f th e p o in t where th e road crosses the f i r s t creek w est
o f Cow Camp Creek a t 43° 8'
55" la t i t u d e and H O 0 48' 45" lo n g itu d e .
GANNETT GROUP:
U n it
Thick
(fe e t)
Cumul.
Th ick
(fe e t)
40+
672+
b4
532
Calcareous c la y s to n e — b ro w n -p u rp le,
weathers same, a few coarse g rain s
o f sand, lim estone n o d ules, cal c i t e
f i l l i n g o f vugs, m assive, becomes
b re c c ia te d near to p , and very nod ular
w ith s t r a ig h t c o n ta c t w ith u n it 17
above - - ------------— ---------------------- -----------
22
448
15.
Concealed
34
426
14.
Sandstone — medium p u r p le , weathers
brown p u rp le , f i n e - to very f i n e ­
g ra in e d , v e ry t h in ly bedded - - - --------
5
392
B echler Conglomerate:
18.
Concealed - - - - - - - - - - - - - - -
Peterson Lim estone:
17.
Limestone - - m edium -grey, weathers g re y p u rp le a t base, becomes lig h t-c r e a m g re y , w eatherin g w h ite -g re y near m id d le ,
mi c r i t i c , s p a r it e c r y s ta ls ap p a re n t,
m assive, c h e rt nodules ------------ ------------
Ephraim Conglomerate:
16.
—
- --------------- —
-
126
GANNETT GROUP continued
U n it
Thick
(fe e t)
Cumul.
Thick
(feet)
13.
Concealed - - - - - - - - - - - -
—
-
103
387
12.
Sandstone - - p u r p le -g r e y , w eathers
m edium -purple, f i n e - to very f i n e ­
g ra in e d , a few grey lim estone
n o d u les, becomes grey lim estone
a t top - - - - — — - — — —
-
12
284
11.
Concealed - - - -----------------------------------------
42
272
10.
Sandstone - - as u n it 12 above - - —
-
2
230
- ------------
18
228
9.
Concealed —
8.
Sandstone — m edium -purple, w eathers
same, f i n e - to very f in e -g r a in e d ,
m assive, a few % in c h , subrounded,
c h e rt pebbles a t base - — — - - —
10
210
Sandstone and con glom eratic sandstone —
sandstone, brow n-red, w eathers w h ite ,
medium- to c o a rs e -g ra in e d , " c le a n ,"
q u a rtzo s e , grades to sandstone, very
f in e -g r a in e d , la m in a te d , near to p ,
conglom erate, brow n-red, w eathers same,
m a trix 20%, c la s ts a re brown c h e r t ,
subangular to subrounded, % inch to
2 in c h e s , s o rtin g in m a trix good to
p o o r, sandstone grades to con glom eratic
sandstone to conglom erate
l e n t i c u l a r ----------------------- -------------- -----------
19
200
6.
C o n c e a le d -------- -------------- --- -------------- -----------
33
181
5.
Sandstone — p u rp le , w eathers p u rp le r e d , very f in e - g r a in e d , very t h in ly
bedded — - - - — - --------------- -----------
11
148
7.
-------- --- —
—
127
GANNETT GROUP continued
U n it
Th ick
(fe e t)
4.
Sandstone — l i g h t - p u r p l e , w eathers
same, f in e -g r a in e d , w e ll s o rte d .
c r c s s - b e d d e d -------- --- — - - - — - - —
3
137
41
134
3.
Concealed - - - - - - - - - -
2.
Sandstone - - very lig h t - p u r p l e ,
weathers same, m edium -grained,
la m in a te d - to t h in ly bedded,
" c le a n ," q uartzose - - - - — ------------
22
93
Concealed - ------------------- —
71
71
10+
10+
I.
—
Cumul.
Thick
(fe e t)
- ---------------
STUMP SANDSTONE
I.
Sandstone — medium g re y , weathers
brow n-grey f in e -g r a in e d , m assive,
g la u c o n itic ------------------- -----------------------------
128
The second p a r t ia l s e c tio n o f th e G annett Group occurs on
tha h i l l , 200 f e e t above U.S. Highway 2 6 -8 9 , d i r e c t l y a d ja c e n t to
Elbow Campground a t 43° 12' 45" l a t i t u d e and H O 0 47' 22" lo n g itu d e .
GANNETT GROUP:
U n it
Thick
(fe e t)
6.
Concealed - - - - - - - - - - - - - - -
Cumul.
Thick
(fe e t)
35+
318+
70
283
Draney Limestone:
5.
Limestone — m edium -grey, weathers
w h ite , m i c r i t i c , m assive, few
coarse c r y s ta ls o f s p a r it e as
v e in f i l l i n g
— — --------------------------------
B echler Conglomerate:
4.
Concealed — s o il lig h t - r e d - p u r p le
- -
87
213
3.
Sandstone - - b u ff-g r e y , w eathers
same, v e ry f in e g ra in e d , t h in ly
bedded to la m in a te d , q u a rtzo se - - —
4
129
100
125
Peterson Lim estone:
2.
Limestone - - as Draney Limestone
above - --------------- --- — - —
- —
Ephraim Conglomerate:
I.
Concealed - - - ---------------- -------------- --- —
25+
25+
129
ASPEN SHALE SECTION
This p a r t ia l s e c tio n o f Aspen Shale occurs in th e w estc e n tra l p a r t o f the quadrangle j u s t to the south o f the L i t t l e Greys
R iv e r on th e e as t fa c in g slo p e .
I t begins 2 ,5 0 0 f e e t southwest o f
the p o in t where th e L i t t l e Greys Road crosses S q u irre l Creek and
2 ,0 0 0
f e e t n o rth e a s t o f the 7 ,4 4 9 fo o t peak, a t 4 3 ° 8 ' 55" la t i t u d e
and H O 0 50' 45" lo n g itu d e .
-
U n it
Thick
(fe e t)
Cumul.
T h ick
( f e e t)
ASPEN FORMATION:
74.
P o rc e la n ite — g re y -g re e n , w h ite
s p o ts , t h in ly bedded - -------------------- - -
I
864+
73.
C o n c e a le d -------- --- - —
I
863
72.
P o rc e la n ite - - g re y -g re e n , massive
1 .5
862
71.
C o n c e a le d ------------------------------------------ -----------
70.
Sandstone— g re y -g re e n , w eathers same
s i l t - to f in e -g r a in e d , a r g illa c e o u s ,
m a s s iv e ----------------— --- ---------------------- —
—
-------------------—
185
8 6 0 .5
10
6 7 5 .5
-
5
6 6 5 .5
68.
Concealed - - - - - - - - - - - - - - -
14
6 6 0 .5
67.
Sandstone - - as u n it 69 above ----------------
3
6 4 6 .5
66.
Concealed - - --------------- --- -------------- -----------
11
6 6 3 .5
69.
Sandstone — g re y -g re e n , weathers
same, m edium -grained, " s a l t and
Pepper," cross-bedded - - ------------—
130
ASPEN SHALE continued
Unit
Thick
(feet)
65.
Cumul.
Thick
(feet)
S i l t y c l aystone - - g re y -g re e n ,
weathers same, p o o rly exposed -------- —
I
632 .5
64.
Concealed —
9 .5
631 .5
63.
Sandstone — g re y -g re e n , w eathers
same, s i l t - to fin e -g r a in e d in
a rg illa c e o u s m a tr ix , p o o rly s o rte d ,
m assive, becomes s i l t y c la y s to n e ,
g re y -g re e n , weathers same, in l a s t
few f e e t -------- --- — - — -------------------
1 3 .5
622
Sandstone — l ig h t - g r e y , weathers
same, m edium -grained, " s a l t and
pepper," s im o n itic , massive - -------- - -
11
6 0 8 .5
S ilts t o n e — g re y -g re e n , w eathers
lig h t - g r e y - --------------------------
75
5 9 7 .5
62.
61.
60.
Sandstone — as u n it 70 above - - —
-
1 .5
590
59.
Sandstone — g re y -g re e n , w eathers
same, v e r y -f in e -g r a in e d - to s i l t ,
t h ic k ly bedded to massive -----------------------
9 .5
5 8 8 .5
Sandstone — l i g h t g re y , weathers
g re y -g re e n , medium g ra in e d , massive - -
I
579
I
578
58.
57.
56.
55.
54.
C oncealed---- -----
—
- - - - - -
C laystone — m edium -grey, weathers
g re y -g re e n , b l o c k y -----------------------
12
Concealed - - - - - - - - - - - - - - Sandstone — g re y -g re e n , w eathers same,
f i n e - to v e r y -f in e -g r a in e d , a rg illa c e o u s
m a t r ix , becomes m edium -grained near
t o p ................ ......................... ............. ......................
577
io
565
6
555
131
ASPEH SHALE continued
- -
Cumul.
Thick
(feet)
39
549
53.
Concealed - - - - - - - - - - -
52.
S ilts t o n e — g re y -g re e n , w eathers
same, blocky — --------------
3 .5
510
Sandstone - - lig h t - g r e y - g r e e n ,
w eathers g re y -g re e n , m edium -grained,
m a s s iv e -------- --- - --------------
3 .5
5 0 6 .5
51.
—
Unit
Thick
(feet)
50.
C o n c e a le d -----------------------------------------------------
71
503
49.
Sandstone and S ilt s t o n e , interbedded —
I fo o t to 2 fo o t beds, sandstone,
medium -grey, weathers g re y -g re e n , very
f in e -g r a in e d , m assive, s i lt s t o n e , g re y g reen , w eathers same, b lo c k y ----------- --- -
10
432
Concealed — a l i t t l e dark grey-g reen
sh a le near top - -------------------------
1 5 .5
422
48.
47.
46.
45.
Sandstone - - g re y -g re e n , w eathers same,
m edium -grained, " s a l t and pepper",
massive - - — — -—
— —
- -
2 .5
4 0 6 .5
---------------- ----------------------
8 .5
404
Sandstone — g re y -g re e n , weathers
same, f i n e - to m edium -grained,
p o o rly cemented
---------------------------------------
3 .5
3 9 5 .5
5
392
Concealed —
-
44.
C o n c e a le d ............ ......................................................
43.
Sandstone — g re y -g re e n , w eathers same,
m edium -grained w ith some f in e g ra in s ,
" s a l t and p ep p er", t h in ly bedded and
c r o s s - b e d d e d -------------------------------------------
42.
Sandstone — g re y -g re e n , w eathers same,
very f in e -g r a in e d , t h in ly bedded
—
-
4
2
387
383
132
ASPEN SHALE continued
U n it
Thick
(fe e t)
41.
Concealed —
- ---------------
4
381
40.
Sandstone — l i g h t g re y , w eathers
g re y -g re e n , m edium -grained, " s a lt
and pep per", massive - — — -------- ---
4
387
46
383
Claystone and s i It s t o n e , interbedded r g re y -g re e n , w eathers same, m o ttle d ,
b lo c k y , in 4 inch to 6 inch beds - - -
9
337
Sandstone — g re y -g re e n , w eathers
same, f in e - g r a in e d , massive — ------------
3
328
Claystone - - g re y -g re e n , weathers
s a m e -------------------------------------------------------------
9
325
Limestone — g re e n -g re y , weathers
medium-brown, m i c r i t i c , massive -------- -
I
316
34.
Concealed ------------ --- - - —
- -
2
315
33.
Sandstone — l ig h t - g r e y , weathers
g re y -g re e n , m edium -grained, " s a lt
and p e p p er", m assive, becomes f in e r
g rain ed l a s t 15 f e e t and c ro ss bedded 3 f e e t -------- --- ----------- --- ---------------
45
313
Concealed — a l i t t l e s h a le , g re y green p rese n t ------------------------------------------ -
49
268
S ilts t o n e — dark g re e n -g re y , w eathers
same, few p la n t frag m en ts, blocky — -
2
219
Concealed —
2
217
39.
38.
37.
36.
35.
32.
31.
. 30.
- —
- - —
Cumul.
Thick
(fe e t)
Concealed — a l i t t l e o liv e -g r e y
s h a le p re s e n t - - - --------------- --- —
------------ —
—
- - —
—
------------------
133
ASPEN SHALE continued
U n it
Thick
(fe e t)
29.
Cumul.
Thick
(feet)
Sandstone — l i g h t g re y , weathers
same, medium g rain ed to f in e
g ra in e d , m assive, occurs as
lenses - - - - - - - — - - —
- -
2
215
28.
Concealed - - - - - - -
- -
9
213
27.
Shale — medium g re y , w eathers same,
f i s s i l e , becomes blocky up s e c tio n —
6 .5
204
Sandstone - - g r e y - b u f f , w eathers
brow n-grey, m edium -grained, t h ic k ly
bedded - — - — - - --------------- -
I
1 9 7 .5
S ilts t o n e — g re y -g re e n , weathers
same, very t h in ly bedded- to s h a ly ,
grading to v e ry f in e -g r a in e d sandstone
a t t o p ---------------- ----------------------------- , ---------
14
1 9 6 .5
Sandstone — g re y -g re e n , w eathers same,
f i n e - to m edium -grained, lim o n t ic ,
massive - --------------- - - — - ---------------
3
132 .5
23.
C o n c e a le d ------------ ------------------ - - - —
-
4
179 .5
22.
Claystone — g re e n -g re y , weathers
medium-brown, blocky
-------- --- --------------
I
175 .5
21.
Concealed - - - - - - - - - - -
- -
7 .5
1 /4 .5
20.
Sandstone - - g re e n -g re y , w eathers
same, f in e - g r a in e d , cross-bedded —
-
4 .5
167
26.
25.
24.
—
- - —
—
19.
Concealed - - - - - - - - - - -
—
- -
8
1 6 2 .5
18.
Sandstone - - g re y -g re e n , w eathers
same, very f in e -g r a in e d , t h in ly
bedded, occurs as lenses -------------------- -
I
154 .5
134
ASPEN SHALE continued
Unit
Thick
(feet)
17.
16.
15.
14.
13.
12.
11.
10.
9.
8.
7.
Cumul.
Thick
(feet)
Shale — medium g re y , weathers
same, f i s s i l e - - — ------------------- -----------
7
1 53 .5
Sandstone - - l i g h t g re y , weathers
g re y -g re e n , m edium -grained, " s a lt
and p ep per", m assive, becomes
t h in ly bedded a t top - - --------------- —
3 .5
146 .5
Shale — d a rk -g re y , w eathers same,
f i s s i l e .....................................................................
3 .5
143
Sandstone * - g re y -g re e n , weathers
same, f i n e - to m edium -grained, " s a lt
and p ep p er", lim o n it i c , massive - --------
2 .5
1 3 9 .5
Shale — g re y -g re e n , w eathers same,
f i s s i l e , becomes blocky up s e c tio n
- -
Concealed - - a l i t t l e s h a le , g re y green p rese n t - ----------------------
6
17
137
131
Sandstone - - g re y -g re e n , weathers
same, m edium -grained, " s a l t and
p e p p e r" , w isp y, l e n t i c u l a r ,
lim o n it ic — - ------------------- ------------—
2
114
C o n c e a le d ------------ ------------------ -------------- —
21
112
S i l t y lim esto n e - - g re y , weathers
brown, uneven bedding, l e n t i c u l a r --------
3
91
Sandstone - - g re y -g re e n , w eathers same,
m edium -grained, t h in ly bedded - - --------
2
83
11
86
S ilts t o n e - - g re y -g re e n , weathers
same, t h in ly bedded, g la u c o n it ic ,
grades to s h a le , d a r k -g r e y , near
t o p ------------ ---------------------
135
ASPEN' SHALE continued
6.
Sandstone — very lig h t - g r e y , weathers
g re y -g re e n , m edium -grained, " s a lt
and pepper" ^ p o o rly cemented
------------
5.
Concealed —
—
- - —
- -
------------
4.
S ilts t o n e — g re y -g re e n , weathers
same, t h in ly bedded, g la u c o n it ic ,
grades to sandstone, g re y -g re e n ,
very fin e -g r a in e d , t h in ly bedded
to very th in ly -b e d d e d near top —
—
Cumul.
Thick
(feet)
I
75
19'
74
. 1 2 .5
3.
C o n c e a le d ---------------------------------------------------------
2.
S hale — b la c k , w eathers d a rk -g re y ,
f i s s i l e --------------------------------------------
I.
Unit
Thick
(feet)
28
55
4 2 .5
5 1 4 .5
Sandstone — g re y , w eathers g re y g reen , m edium -grained, " s a lt and
pep per", t h in ly bedded, becomes
t h ic k ly bedded near t o p -------- ------------------
9 .5
9 .5
BEAR RIVER FORMATION:
5.
4.
3.
Shale — d a rk -g re y , w eathers b la c k ,
s ilt y , f is s ile
---------------------------------Shale — as above but w ith
f o s s ilif e r o u s bed 6 inches from base
13 60+
-
14
Sandstone - - g re y -g re e n , weathers
same, f in e -g r a in e d , p la n t frag m en ts,
t h in ly bedded, becomes t h ic k ly bedded
near t o p ................... - ........................................
11
47
33
136
ASPEN SHALE continued
2.
I.
Shale — b la c k , w eathers same, w ith
coquina f l o a t Sandstone — as u n it 3 above
- —
-
U n it
Thick
(fe e t)
Cumul.
Thick
(fe e t)
16
22
6+
6
.
HO045
43°I5'
PLATE I
•x
:< ■<%■
EXPLANATION
ALLUVIUM
Q ol
GEOLOGIC MAP OF A PORTION OF
COLLUVIUM
Qc
h
Q t2
THE PINE CREEK QUADRANGLE,
TERRACE
QUATERNARY
DEPOSITS
Q t1
X:
Q ls
LANDSLIDE
Qb
BRECCIA
Q co
CONGLOMERATE
TETON AND LINCOLN COUNTIES,
ASPEN
~Ko
0—
P
DERIVED FROM
BAILEY CREEK
LANDSLIDE
SHALE
PORCELANITE, C CONGLOMERATE
UPPER — i
Kbu
CRETACEOUS
DEPOSITS
— BEAR
Kbl
RIVER
FORMATION
LOWER-J
UPPER— I
Kgu
L- GANNETT
Kgl
GROUP
LOWER—*
STUMP SANDSTONE
Jsp
JURASSIC
PREUSS
Jt
TWIN
An
NUGGET
—
SANDSTONE
CREEK
LIMESTONE
SANDSTONE
ANKAREH
FORMATION
T HAYNES
FORMATION
\
\
4 3 ° I0 I50"
TRIASSIC
\\
\
WOODSIDE
FORMATION
DINWOODY
FORMATION
\
\
UPPER—
PHOSPHORIA
"ASSOCIATED
PERMIAN
LOWER-
PENNSYLVANIAN
PPMw
M IS S IS S IP P I
Mm
WELLS
FORMATION
MISSION
CANYON
CONTACT,
z
z
X
LIMESTONE
DASHED WHERE
APPROXIMATELY
LOCATED
FAULT,
WHERE
DASHED
APPROXIMATELY
LOCATED
U
UPTHROWN
SIDE
D
DOWNT HROWN
SIDE
ANTICLINE
Z ^
X
OVERTURED
ANTICLINE
SYNCLINE
STRIKE
£
$
AND
DIP
OF
INCLINED
OVERTURNED
VERTICAL
4 3 e0 8 ,45"
II0 °5 2 '3 0 "
GEOLOGY
BY
ROBERT
A.
LUNCEFORD
SUBMITTED IN PARTIAL FU LFILLM EN T OF
THE REQUIREMENTS
FOR THE
DEGREE
OF MASTER OF SCIENCE
IN EARTH
SCIENCES
AT MONTANA
STATE
UNIVERSITY
1976
MILES
5000
4 3 ° 0 7 , 30"
IIOe45'
INDEX
MAP
FORMATION
ROCKS
AND
MONTANA STATE UNIVERSITY LIBRARIES