CO\TRIBCTIO\S F R O M T H E M I S E U M O F PAI_EO\TOLOGY
THE UYIVERSITY OF M I C H I G A N
VOI 27. \ O 3. p 73-85 (4 Figures)
August 16. 1985
NEWFOUND EARLY CRETACEOUS DINOSAURS A N D OTHER
FOSSILS IN SOUTHEASTERN IDAHO A N D WESTERNMOST
WYOMING
BY
J O H N A. DORR. J R .
MUSEUM OF PALEONTOLOGY
T H E UNIVERSITY O F MICHIGAN
ANN ARBOR
CONTRIBUTIONS FROM T H E MUSEUM O F PALEONTOLOGY
Philip D. Gingerich. Director
Gerald R. Smith, Editor
This series of contributions from the Museum of Paleontology is a medium for the publication
of papers based chiefly upon the collections in the Museum. When the number of pagesissued is
sufficient t o make a volume, a title page and a table of contents will be sent to libraries on the
mailing list, and to individuals upon request. A list of the separate papers may also be obtained.
Correspondence should be directed to the Museum of Paleontology, The University of
Michigan, Ann Arbor, Michigan, 48 109.
VOLS. 11-XXVI. Parts of volumes may be obtained if available. Price lists available upon
inquiry.
N E W F O U N D E A R L Y CRETACEOUS D I N O S A U R S A N D OTHER FOSSILS IN
S O U T H E A S T E R N I D A H O A N D W E S T E R N M O S T WYOMING
J o h n A. Dorr. .Jr.
Department of Geological Sciences.
The University of Michigan. A n n Arbor. M I 48109
Ahstracr-Early
Cretaceous, wet alluvial fan deposits of the Gannett a n d
Wayan formations in southeastern l d a h o a n d westernmost Wyoming were
derived by erosion from highlands uplifted by movements o n the Paris '1-hrust
in the Sevier Orogenic Belt. Newfound fossils indicate t h a t the environment of
deposition of the Wayan (and probably also the Gannett) formation provided
conditions favorable f o r habitation by a n a b u n d a n t and diverse biota,
including ferns a n d dicotyledonous plants. freshwater molluscs, aquatic turtles
a n d crocodilians, a n d dinosaurs. Abundant eggshell fragments indicate that a
variety of types a n d sires of dinosaurs nested o n the interfluves of the fan
uplands, taking advantage of the combination of relatively low watertable, d r y
soil conditions, a b u n d a n t plant food supply. a n d easily accessible, perennial,
surface freshwater supplies. Analogous lithotopes a n d biotopes occur o n the
wet alluvial megafans of the modern Indogangetic Plain.
INTRODUCTION
T h e fragmentary fossil specimens listed below include the first identifiable remains of
dinosaurs a n d certain o t h e r vertebrates t o be reported from the W a y a n Formation. They also
include the first identifiable dinosaur remains of a n y kind t o be reported from Idaho. Together
with the fossil invertebrates a n d plants also listed. the fossils provide clues t o the environment of
deposition of the rocks in which they occur.
GEOLOGICAL SETTING
Recurrent movements o n the Paris Thrust, first and westernmost of a progressive sequence of
overthrusts (Figure I). produced a n episodically uplifted (Figure 2 ) sedimentary source area in
southeastern Idaho. T h e Early Cretaceous. synorogenic clastic sediments derived from t h a t
highland were transported eastward and deposited in a tectonic foredeep in southeasternmost
l d a h o a n d westernmost Wyoming (Wiltschko a n d Dorr. 1983). Crustal subsidence beneath the
foredeep mainly was caused by thrust loading ( J o r d a n . 198 I). T h e nonmarine sediments were
deposited by braided streams proximal t o the source area a n d by meandering streams distally
(Schmitt. Sippel and Wallem, 1981; Sippel. Schmitt a n d Wallem. 198 1: Schmitt a n d M o r a n ,
74
FIG I
.J.A. DORR, J R .
0
5
10
L
I
I
20 M ~ l e s
I
Index m a p of Idaho-\\'yorn~ngthrust belt. Stars dcnote l'oi;ril localit~es.
HOGBACK BASIN
(Northern end of Green River
Basin AND THE ADJACENT
BEAR RIVER FM.
PARIS THRUST
EPHRAIM FM. ( Lower part. Nearshore marine sh.)
OXFORDIAN
STUMP FM.
DOMINANTLY FLUVIATILE
[
. :I
DOMINANTLY LACUSTRINE
SUNDANCE FM.
MARINE AND/OR BRACKISH
Markedly conglomeratic
LL
-
/
IblC;. 2
Sandstones and finer clastics
Stratigrirphic correlation c1ial.t. 1-roni R u b c ) . 1973: Schmitt and Moran, 1982: M'iltscl1h.o a n d 1101.r. 198.7:
13crrnnrl. \Vilkinsorl a n d Dorl-. 1984.
76
J.A. DORR. J R .
1982; Schmitt a n d Sippel. 1983). T h e sediments accumulated o n a succession of eastwardly and
southeastwardly prograding alluvial fans (Armstrong and Oriel, 1965; Eyer, 1969) during
deposition of the Ephraim, Bechler, Wayan (including T h o m a s Fork a n d Quealy). Sage Junction
a n d lower part of the Frontier formations. Fan progradations were interrupted b y lacustrine
episodes of deposition (Peterson a n d Draney-Smoot) a n d by marginal marine incursions
(Smiths a n d Cokeville). At first, during deposition of the Gannett G r o u p , the alluvial f a n
deposits graded into the thinner, coeval Morrison a n d Cloverly formations deposited o n a
lowland alluvial plain (Figure 2). Later f a n deposits (Wayan a n d Sage Junction) graded into
marginal marine a n d marine deposits of the upper Bear River and Aspen formations.
l'he general locations of the fossil vertebrate sites reported here a r e indicated o n Figure 1 .
More detailed locality d a t a a r e given in the text. T h e fragmentary fossil remains, n o n e worthy of
separate catalogue n u m b e r o r detailed description, a r e conserved under a single n u m b e r
(UM78899) in the University of Michigan Museum of Paleontology. Fossils a r e listed by
stratigraphic unit in ascending stratigraphic order.
GANNETT GROUP
T h e Gannett G r o u p h a s yielded very little fossil vertebrate material, all of it very fragmentary
a n d specifically unidentifiable, in contrast with the partially coeval Cloverly Formation which
has produced a b u n d a n t a n d diverse material of excellent quality in central Wyoming (Ostrom,
1970). Mansfield (1927) reported unidentified fossil b o n e from the Gannett G r o u p a l o n g Tincup
Creek (Figures 1 a n d 3) in southeastern Idaho, b u t the exact stratigraphic a n d geographic
provenance of that material is uncertain. S.S. Oriel of the U . S. Geological Survey (pers. c o m m . )
reports a recent discovery of dinosaur bone in t h e Gannett in the Blackfoot Range of Idaho, but
that material has not been identified more exactly. 1 have found large, but unidentifiable reptile
limb b o n e fragments a n d pieces of turtle carapace in the upper part of the group, close beneath
the Smiths Formation, north of Idaho Rd. 3 4 a n d Pine Bar Campground.alongTincup Creek in
the Caribou Range of I d a h o (Figure 3a).
Paleontological evidence for the ages of the several formations of the Gannett G r o u p was
summarized by Eyer (1969). T h e basal 15 m of red shale, called "Lower Ephraim," contain
belemnites a n d oysters of latest Jurassic age a n d marginal marine origin, but these shales might
better be considered a s representing the waning phase of deposition of the marine S t u m p
Formation. Aptian charaphytes occur in t h e upper part of the Ephraim, Peterson, Bechler,
Draney a n d lower part of the S m o o t formations. T h e upper part of the S m o o t contains
charaphytes and ostracods of a n age spanning the Aptian-Albian boundary. Unidentified
freshwater molluscs have been reported (Wanlcss cr 01.. 1955)from the g r o u p within the Hoback
Range south of .Jackson. Wyoming. Collectively. the fossils indicate that deposition of the
remainder of the g r o u p , after the "Lower Ephraim", occurred in nonmarine environments.
S M I I H S A N D L O W E R REAR R I V E R F O R M A T I O N S
Rube) (1973) and Durkee (1979) described the stratigraphy and sedimentology of the Smiths
Formation. The Bear River Formation is discussed in M'anless pt 01. (1955). l ~ h eS m i t h s
Formation is a coeval. western. stratigraphic extension of the black shales a n d oberlying
EARI-J' CRET.I\CEOL'S DIXOSAL'RS I \ IDAHO A S D \!'\r'OMI\G
77
erman
ic'
I
.
.
\trial p h o t o g r a p h \ . cnlaryed r ~ h:tr
c \ c a l c \ ~f r o m 1 .S.l)cp;irtrncnt 01 I n t c r ~ o r .( i c o l o i c ; i l \uric!. f l<O\
1)at;i ('enter Image\ I K 11 \l'~OOOOOYh r' 2' 19\0) a n d 1 \ f f \1'voooo lYh ( Y 2 2 IY\OI.
( a ) l-o\\il \Ite\ ,\-.I in \\a!;in 1 - o r m a t ~ o na n d a 41nglc \ltc in (;annett (irotip.
I h ) 1)ctall 01 ? a . Site\ .\-.I ; i l o n ~uppt'r p;irt of 1 incup C'rcch. \cction\ 14. 15. 2 2 . 23 a n d 24. 155-1<J41 .
C'arihou C'or~nt!. I d a h o .
( c ) \ I I C K In \\ a!an 1-orrn;it1ori o n \ l ~ n c r \ 1 ) e l i ~ h t('reek. C'arihou H;i\in. \I 1 ?. 5c.c.. 23. I ?\-l<J41 .
13onne\ illc C'ount!. Id;i ho.
Kg-(iannctt ( i r o t ~ p .K\-\rnith\ I-orm;ition. Ki\-\\;i!;in 1 - o r n ~ a t i o n .
K\i-\;igc .luncrion 1 - o r r n a t ~ o n()-()r~:itcrn:tr\.
.
1 \I-1 a t e ('crio/oic
\;ill
1 a h e I - ~ r r i i a t ~(';ipit;tl
~n.
letter\ (11 h ~ r eo r black I - ~ . o \ \\I~~t c \ .
78
J.A. DORR, J R .
sandstones of the lower part of the Bear River Formation. Rubey ( 1973) a n d McGookey (1972)
place t h e Smiths a n d Bear River formations in the Early Cretaceous (Albian).
Fossils from the lower, black shale member of the Smiths Formation include the following
( D u r k e e , 1979; Rubey, 1973): plant fragments, small, a b u n d a n t , widespread; thin coal lenses,
small, local; worm burrows, trails a n d o t h e r extensive bioturbation features; mollusks including
Corbicula, Unio ( 2 types), Vivipurus, "Lioplacodes" (may be Vi\~iparus),Goniohasi.~,and
Can~peloma.The first two mollusks a r e clams, the others snails. Corhi~~ula
may have been a
brackishwater form, but the rest of the mollusks are freshwater types.
Wanless er 01. (1955) reported a scant, poorly preserved, freshwater mollusk fauna from the
lower Bear River Formation along Greys River in the S n a k e River Range. Thin coals a r e present
in the lower Bear River. I have found the following in it: plant fragments,abundant, widespread,
including stem, twig and leaf impressions; worm trails a n d burrows; fish bone fragments
including a lowerjaw with a few teeth f r o m a roadcut on the north side of U.S. 26-89 in the Snake
River Canyon just west of Keyser Creek which lies east of t h e Absaroka Thrust (Figure I).
WAYAN A N D SAGE JUNCI'ION FORMAI'IONS A N D COEVAL UNITS
General Description
D u r i n g the middleand late Albian, the margin of the M o w r y Seaway fluctuated in a n east-west
direction across much of western Wyoming, a s recorded in the upper part of the Bear River
F o r m a t i o n and the overlying Aspen Formation in the H o b a c k , Wyoming and S n a k e River
ranges. Freshwater a n d brackishwater mollusks, including Ostrea, alternate stratigraphically
there (Wanless er al., 1955). Royse et al. (1975) reported a b u n d a n t marine microfossils of several
types a n d from several levels elsewhere in the upper part of the Bear River Formation.
Contemporaneously, accelerated clastic sediment influx off the reelevated Paris Thrust
(Sippel et a/., 1981; Wiltschko a n d D o r r , 1983) generated a second alluvial fan complex. In the
Caribou Range of southeastern Idaho, this clastic wedge consists of the Wayan and Sage
Junction formations a n d the basal part of the Frontier F o r m a t i o n . It prograded eastward,
excluding the rising Mowry Sea f r o m much of westernmost Wyoming a n d southeastern Idaho.
-l-liis second wedge (the first was that formed by the Gannett G r o u p ) graded into the upper Bear
River a n d Aspen formations ( R u b e y , 1973), but uplift a n d erosion of the Absaroka Thrust plate
during the latest Cretaceousand Paleocene subsequently disrupted the original continuity of that
facies relationship a n d a t the same time telescoped the facies eastward from their original
relationship to one a n o t h e r (Wiltschko and Dorr, 1983). 'l'he T h o m a s Fork and Quealy
formations a r e southwardly a n d southeastwardly extended tongues of the Wayan Formation
( R u b e y , 1973; Schmitt a n d M o r a n , 1982) separated by the Cokeville Formation of b o t h brackish
a n d freshwater origin which records a minor, temporary, fluctuating, westward transgression of
the coastal environments of the M o w r p (upper Bear River a n d Aspen) Sea.
T h e T h o m a s Fork. Cokeville, Quealy. a n d Sage .Junction formations a r e best exposed along
the Smiths Fork and 1-homas F o r k rivers in westernmost Wyoming (Figure I and Rubey, 1973).
Detailed lithologic descriptions. measured sections and discussions of stratigraphic a n d facies
relationships for the a b o v e units a r e given by Rubey (1973). M o s t significantly. for the purposes
of this paper, the Wayan. T h o m a s Fork. a n d Quealy formations a r e distinctly color-variegated,
c o m m o n l y reddened. a n d include a b u n d a n t calcareous soil nodules a t frequent intervals. all
indicating the presence of numerous paleosols. These ancient soils formed by weathering under
EARLY CRETACEOUS DINOSAURS I N IDAHO AND WYOMING
79
oxidizing conditions in well drained areas where watertables were relatively low and where
sedimentation was interrupted for significant periods of time. The Gannett Group similarly
contains reddened and color-variegated strata. In contrast, the Smiths, Cokeville. Bear River.
and Aspen formations are drab colored and lack paleosols and calcareous soil nodules.
Thomas Fork Formation
The type locality of the Thomas Fork Formation (Rubey, 1973) lies along the north side of
Thomas Fork Creek, about 23 miles (37 Km) south of Afton, Wyoming. The following fossils
have been found there, those with asterisks being new reports, the others previously reported by
Rubey:
-Gastropods, small, unidentified.
*Unionid pelecypods, partial shells and shell fragments, indicating perennial freshwater
environment of deposition.
-Fish scales, unidentified.
-Bone fragments, unidentified.
*Gastroliths, 2 to-3 mm. sized.
*Turtle carapace fragments of two types:
a . Patterned; surface ornamentation of "trionychid type " but not trionychid. Imply
presence of perennial, surface freshwater, at least locally.
b. Unpatterned type. May or may not have been aquatic turtles.
*Reptilian bone fragments, large enough to have been of dinosaurian origin but not specifically
identifiable. Found as weathered-out fragments near base of formation, between 10 and 30
meters above road along north side of Thomas Fork Creek in Unit 5 of type section in center of
N-112, Sec. 26, T28N-R119W, Lincoln County, Wyoming (for location see Rubey, 1973, p. 14
and Figure 4).
*Dinosaur eggshell fragments, abundant, ubiquitous, resembling those described below from the
Wayan Formation, probably ornithischian and possibly ornithopodan dinosaur (iguanodontid
or hadrosaurid). Also occur in upper 49 meters (160 feet) of the same formation along Smiths
Fork River east of Cokeville.
Cokeville Formation
Porcelanites within the Cokeville Formation suggest a temporal correlation principally with
the Aspen Formation to the east, although a single, thin porcelanite bed occurs in a limited area
in the uppermost part of the Bear River Formation below. The type locality of the Cokeville
Formation is along the north side of the Smiths Fork River, 2 miles (3.2 Km) northeast of
Cokeville, Wyoming, in the SW 112 of Sec. 36, T25N-RI 19W. Lincoln County, Wyoming
(Figure 1 and Rubey, 1973). No fossil vertebrates have been found in the formation, although
gastroliths (possibly of reptilian origin) are abundant at many levels. Fossil invertebrates found
at the type locality are:
-O.~trea,I foot thick bed of coquina, in upper third of formation. Oyster beds also occur in the
coeval Aspen and upper part of the Bear River formations.
-Pi,rguli/era, freshwater snail. near top of lower third of formation, also occurs in upper part of
Bear River Formation.
-Ca~npeloma.freshwater snail, occurs just below P\.rgulifera. Also occurs in Smiths Formation.
J.A. D O R R , J R .
FIG. 4
Some fossil vertebrate specimens. mentioned in text, from the Early CI-etaceous W a y n F o r m a t ~ o n .All
specimens collectively numbered 11M78899 in Oniversityof Michigan Museum of I'aleontology. Ann Arbor.
Michigan.
A. B, and C. Caudal vertebra of ornithopodan ornithischian dinosaur, r ~ g h and
t
left lateral a n d articular
views, approximately 1 / 3 natural size (see c m scale). from Sitc I.
D. E. and F. Tooth of ankylosaurian dinosaur, right a n d left lateral and occlusal vicws, approximately 10
times natural size. from Site A .
G and H . Tooth ofthe iguanodontid dinosaur-, 7i~r7on/osaurus,
right and left lateral views, appl-oximately 2.5
times natul-al size. from Site C.
I and J . CI-ocodiliancrushingtooth. lateraland cro\+n views.approximateiy2.27 timcs natural size. from Site
B.
K , L, and M . 1 wo typical c x a ~ n p l e sof dinosaur cggshell Cragmcnts from the Wayan Formation. K. crosssections: L , convex exteriors with ornarnentation: M , concave interiors, minutely pebbled. All
approx~rnately2.5 times natural sire (see cm scale).
8I
E:IRLJ' CRET.;ZCEOUS DIY0S:IC'RS I \ IDAHO AYD iI'I'O\II\G
%--
:
--,
- 4a,#!@5
--
F
-_
t
L
i l i l \ l l ! ! l ~
METRIC
cml
+---
-
82
J.A. DORR. J R .
1 found n o fossils in this redbed-rich, color-variegated deposit in which calcareous soil nodules
a n d paleosols are c o m m o n . However, Rubey (1973) reported the presence of fossil"fa1se trunks"
of the Early Cretaceous fern. I'ernpskj.~,which also occurs in the Sage .Junction Formation
above. a s well a s in the Wayan a n d Aspen formations.
Waj,an Fortnation
T h e Wayan Formation occurs in the Caribou Range and along the western flank of that range
in southeastern Idaho. T h e type locality is along upper Tincup Creek, a b o u t 5 miles (8 K m ) east
of the town of Wayan, I d a h o (Figures 1 a n d 3). Most of the strata that yielded the fossils listed
below lie west of the structurally complex Caribou Range, although one locality (Site ti,Figure
3c) is in the Caribou Basin within that range. l'he Wayan F o r m a t i o n is fluviatile in origin. Fossilproducing strata a r e conspicuously color-variegated, including bright red siltstones and
claystones which dominate the sequence, alternating with relatively thinner sandstones a n d
conglomeratic sandstones ranging in color from medium brown t o reddish-brown. Calcareous
soil nodules a b o u n d in b o t h red a n d gray, fine-grained, clastic units throughout the formation.
Nodules a r e more rare in the sandstones, but d o occur as basal channel lag deposits, reworked
f r o m soils of upstream or. adjacent levee a n d overbank deposits.
T h e late Early Cretaceous (Albian) age assigned t o the Wayan Formation (Figure 2) is based
partly o n its stratigraphic position above the Gannett G r o u p a n d below the Sage Junction
Formation, a n d its inferred intergrading relationship with the well-dated upper Bear River a n d
Aspen formations. In addition, a nonmarine black shale within t h e Wayan Formation, a b o u t 440
meters a b o v e the base along McCoy Creek in the Caribou Basin, has been dated a s Middle
Albian (upper Bear River-lower Aspen) o n the basis of the palynomorphs Taurocus/~oritc<s
.s/~ackt?iuniand cf. Ven-icosisporites nhsc~~rilaesuratus
(Schmitt a n d M o r a n , 1982). Also, the
minor, occurs in b o t h the Wayan a n d Aspen formations. Although the
fossil fern, Ter~~pskjla
newfound fossil vertebrates from the formation a p p e a r to have their closest affinities with those
from the Cloverly Formation of Aptian age, this does not necessitate age equivalence because the
fossils a r e t o o fragmentary f o r specific identification and terrestrial vertebrates a r e u n k n o w n
f r o m the succeeding Bear River a n d Aspen formations.
T h e fragmentary fossils from the Wayan Formation are from I 1 sites (Figure 3a,b,c). l'en sites
( A - J ) occur close together in roadcuts a n d meander scars along upper T i n c u p Creek for a b o u t 2.5
miles (4 K m ) from Idaho Road 34 northwestward along the gravel side road t o Gray t o the first
bridge crossing Tincup Creek. l ' h e 11th site ( K ) is a b o u t 12 miles ( I 9 Km) d u e north from there,
along Miners Delight Creek within the Caribou Basin (Figure 3c). Fossils were first found a t Site
A by surface prospecting a n d subsequently by washing 50 burlap sacks of matrix through
flyscreen, then sorting the concentrate under a binocular microscope. Fossils from all other sites
were found by surface prospecting alone. Fossils,in the following categories, occur a t one o r
more of the lettered sites a s indicated. All a r e new reports f o r t h e Wayan Formation.
-Snail operculae, calcareous. 5 m m m a x i m u m diameter. n u m e r o u s in screenwashed concentrate,
indicate perennially available surface water a t least a t some places o n the Wayan alluvial fans.
Site A .
-.I-urtle, carapace fragments. unpatterned type. average 5.5 m m . thick. probablyaquatic. Sites A
a n d ti.
-Reptilian limb bone fragments. large. probably dinosaur 01- large crocodilian, otherwise
unidentifiable. Sites D. 1:. F. H. ti.
E A R L Y C R E T A C E O C ' S D I X O S A U R S 1Y I D A H O A \ D W Y O M I U G
83
-Crocodilian teeth of two types. ( a ) small. conical. resembling the "Gonic,1/~l7olis"type from
Morrison and Clolerly formations (Ostrom. 1970). Sites A a n d G:(b) large. blunt, low-cro~vned.
similar t o type from Cloverly Formation ( O s t r o m . 1970). Site R.
-Tenonto.vuur~ts.sp. indet.. a n iguanodontid dinosaur. single tooth. genus also occurs in Cloverly
Formation (Ostrom. 1970). Site C.
-Ankylosaurian dinosaur, single. small tooth. possibly juvenile but worn. genus and species
indeterminate. Ankylosaurs also occur in the Cloverly Formation (Ostrom, 1970). Site A .
-Ornithopod, ornithischian dinosaur. caudal vertebra, very large, weather-checked a n d abraded
prior t o burial. hence transported downstream f r o m higher on alluvial fan upland. Site I.
-Reptilian caudal vertebrae. identity indeterminate. 2 specimens (left in s i t ~ i )Site
. K on Miners
Delight Creek.
-Miscellaneous, indeterminate, medium-sized b o n e f r a g m e n t s , p r o b a b l y d i n o s a u r i a n o r
crocodilian. Sites G, H, J.
-Very small, hollow, thin-walled vertebrate limbbone fragments found only in screen-washed
concentrate from Site A . Possibly frog bones.
-Gastroliths?, possibly reptilian, pinhead sized t o a b o u t 2 cm. in maximum diameter. Site A.
-Dinosaur eggshell fragments. (Note that these also occur in the -1-homas Fork Formation. see
earlier in this paper.)
( a ) Sites A , G, and H. Very a b u n d a n t ; ranging in thickness from 0.2 to 2.0 mm.: curvatures
suggesting whole egg minimum diameters ranging from robin egg size u p t o 7.7 c m . ( 3 inches);
including a t least six varieties of exterior surface textures ranging from pebbled t o ridged. Large
types probably from iguanodontid eggs.
( b ) Sites I, J, and K (Miners Delight Creek), occasional fragments.
T h e a q u a t i c snails, turtles a n d crocodilians suggest that surface water was perennially
available a t least locally o n the alluvial fans. A variety of small t o large dinosaurs also lived there.
1-he eggshell fragments indicate that dinosaurs of several sizes and types nested there, probably
o n the relatively dry, better-drained interfluvesadjacent to more heavily vegetated stream banks,
o x b o w lakes and sloughs. Such physical conditions and features exist in close proximity t o one
a n o t h e r a n d support ecologically similar biotas o n the wet alluvial megafans o f the modern
Indogangetic Plain ( D o r r , 1983).
SAGE JUNCTION FORMATION
T h e type locality of the Sage Junction F o r m a t i o n is 1.5 miles (2.4 Km) west of Sage. Wyoming
( R u b e y . 1973) where the formation now is only poorly exposed. Numerous thin porcelanite beds
occur t h r o u g h o u t the formation there a n d a few beds of coal a r e present in the lower part.
Porcelanites also occur in the formation east of Wayan. Idaho. 85 miles (137 Km) t o the north.
There it is described by Oriel and Platt (1980. Preston Quadrangle) a s "gray a n d tan siltstone and
sandstone, minor quartzite. porcelanite. limestone. conglomerate a n d coal." In contrast with the
underlying Wayan Formation, it lacks the variegated bright red, pink a n d brown hues typical of
the former. a n d calcareous soil nodules occur only as basal channel lag deposits. No eggshells
were f o u n d in the Sage Junction F o r m a t i o n despite intensive search. My interpretation is that by
Sage J u n c t i o n time the alluvial fan environment had contracted well to the west. closer t o the by
then erosionally much reduced highlands of t h e Paris Thrust. hence the environment of
deposition of the Sage Junction Formation was relativel!! distal on the fans o r perhaps even had
become a n alluvial plain of much lower elevation and gradient.
J . A . D O R R . JR
The following fossils occur in the formation, those with asterisks being new reports, the other-s
previously reported by Rubey (1973):
-Nonmarine mollusks, unidentified.
which also occurs in the Aspen Formation to
-"False trunks" of the Cretaceous fern. Trtn~~.rkl~a,
the east.
-Leaves of of Nil.csoniu, Platan~cs,Ar!oca,p~c.c.and Lirioclen~lron,and fragments of stems and
roots.
* Unionid clams
*Bone fragments, rare, unidentifiable.
*Crayfish burrows, probably excavated in stream channel banks o r levees.
1he porcelanites and T e m p s k ~ zsuggest a n age corrclation with the Aspen Formation.
According to Rubey, the leaves in the upper part of the formation could be young enough to
make the uppermost part of the formation early Late Cretaceous, but the temporal ranges of the
taxa extend back into the late Early Cretaceous The clams and crayfish burrows indicate the
presence of perennial bodies of freshwater a t the surface, a t least locally.
S U M M A R Y A N D CONC1,IJSIONS
The Early Cretaceous Gannett Group and the Wayan-Sage Junction couplet with its related
tongues are two successive, complex, synorogenic clastic wedges comprised of sediment that was
derived from highlands produced by uplift of the Paris 'I-hrust plate. Deformation occurred
during a n early phase of the Sevier Orogeny. Deposition took place in a foredeep created by
crustal loading by that overthrust plate. l h e eastwardly prograding, wet alluvial fans in that
tectonic setting encompassed both relatively dry interfluves and adjacent, perennial surface
freshwater environments a t least locally.
The fossil record now available indicates that those physical conditions favored a rich and
diverse biota. The Gannett record is sparse, but indicates the presence of charaphytes, mollusks,
ostracods and large reptiles including turtles and probably also dinosaurs. The Wayan-Sage
Junction biota included ferns, various dicotyledonous plants, freshwater clams and perennially
aquatic snails, crayfishes, aquatic turtles, two types of crocodilians, and a variety of other small
to large reptiles such as iguanodontid and ankylosaurian dinosaurs. Dinosaur eggshell
fragments, ranging from small to large and of a variety of surface ornamentation types are
abundant and ubiquitous in both the Wayan Formation and in its lower tongue, the Thomas
Fork Formation. Those formations characteristically are reddened, color-variegated, and
contain abundant and widespread calcareous soil nodules a t many levels indicating the presence
of paleosols formed under conditions of low soil moisture. relatively low watertable and
oxidizing environment. Numerous dinosaurs of various types and sizes favored these conditions
for reproductive purposes, nesting on the interfluves of the alluvial fan uplands adjacent to the
Paris Thrust.
The inferred sedimentologic and biologic features of that ancient setting are closely analogous
to those on the wet alluvial megafans of the Quaternary Indogangetic Plain.
E A R L Y C R E T A C E O U S D I N O S A U R S IN I D A H O A N D W Y O M I N G
I thank the following f o r help in identifying fragmentary fossil material: F. Fursich. University
of M u n i c h ; R . M . G a l t o n . Yale University; J . R . H o r n e r . M o n t a n a S t a t e UniversityB0zeman;J.H. Hutchison, University of California-Berkeley; N. Hotton. U.S. National
Museum: F.A. Jenkins, J r . , Harvard University: J . H . Ostrorn, Yale University; Hans-Dieter
Sues, Harvard University; H. Van d e r Schalie, University of Michigan. Partial support for field
work came from the T u r n e r Fund. Dept. of Geological Sciences. T h e University of Michigan.
REFERENCES CITED
Armstrong, F.C. and Oriel. S.S., 1965. Tectonic development of the Idaho-Wyoming thrust belt: American Association
of Petroleum Geologists Bulletin. v. 49. p. 1847-1866.
Derman. A.S.. Wilkinson. B.H. and Dorr. J.A. Jr., 1984. Jurassic-Cretaceous nonmarine foreland basin sedimentation
in western United States: American Association of Petroleum Geologists Bulletin. v. 68 (Convention Issue). p.
4 7 0 4 7 1.
Dorr. 5 . 4 . Jr., 1983, Early Cretaceous stratigraphy, paleontology and sedimentary tectonics in the Paris Overthrust
foredeep (western Wyoming a n d southeastern 1daho)compared with Quaternary featuresof Indo-gangetic Plain:
p. 7 in American Association of Petroleum Geologists Rocky Mountain Section Meeting. Billings. Montana,
Book of Abstracts. 34 p. (unnumbered).
Durkee. S.K., 1979, Depositional environments of the Lower Cretaceous Smiths Formation within a portion o f the
Idaho-Wyoming Thrust Belt: Thesis. MS in Geology. ldaho State University. 70 p.
Eyer, J.E., 1969. Gannett group of western Wyoming and southeastern Idaho: American Association of Petroleum
Geologists Bulletin, v. 53. p. 1368-1390.
Jordan. I-.,1981, Thrust loads and foreland basin evolution. Cretaceous. western United States: American Association of
Petroleum Geologists Bulletin, v. 6 5 , p. 2506-2520.
Mansfield, G.R., 1927, Geography, geology, and mineral resources of part of southeastern Idaho: U.S. Geological
Survey Professional Paper 152, 453 p.
McGookey, D.P., 1972. Cretaceous System: p. 190-228 in Rocky Mountain Association of Geologists. Geologic Atlas of
the Rocky Mountain Region, 331 p.
Ostrom. J . H.. 1970. Stratigraphy a n d paleontology of the Cloverly Formation (Lower Cretaceous) ofthe Bighorn Basin
area, Wyoming: Peabody Museum of Katural History Bulletin 35. 234 p.
Rubey, W.W., 1973. New Cretaceous formations in the western Wyoming thrust belt: U.S. Geological Survey Bulletin
1372-1, 35 p.
Schmitt, J .G. and Moran. M.E.. 1982. Stratigraphy of the Cretaceous Wayan Formation. Caribou Mountains.
southeastern ldaho thrust belt: University of Wyoming Contributions to Geology. v. 21. p. 55-71.
Schmitt. J.G. and Sippel. K.B.. 1983. Synorogenic sedimentation associated with development of Paris-Willard thrust
system. Wyoming-Idaho-lltah thrust belt: American Association of Petroleum Geologists. Rocky Mountain
Section Meeting. Billings. Montana. p. 26-27 in Book of Abstracts (34 unnumbered p.).
D.B.. 1981. Upper Jurassic through lowermost upper Cretaceous
Schmitt. J.G.. Sippel. K.N. and \!'allem.
sedimentation in the Wyoming-Idaho-l!tah thrust belt-I: Depositional environments and facies distribution: p.
26-27 in Sedimentary Tectonics: Principles and Applications.abstracts. compiled b y J . R . Steidtmann. University
of Wyoming. Joint Meeting of the Dept. of Geology. Uni\. U'yoming-Wyoming Geol. Asroc.-Geol. Survey
Wyoming. 40 p.
Sippel.. K.U.. Schmitt. J . G . a n d M'allem. D.B.. 1981. lipper Jurassic through lowermost upper Cretaceous
sedimentation in the Wyoming-ldaho-Ltah thrust belt-11: Provenance and tectonic implications: p. 28-29 irz
Sedimentary Tectonics:Principles and Applications. abstracts. compiled by J . R . Steidtrnann. I:niversity of
Wyoming. Joint meeting of the Dept. of Geolo_e>. U n i ~ .Wyoming-\Vyoming Geol. Assoc.-Geol. Survey
Wyoming. 40 p.
\','anless, H.R.. Belknap. R.L. and Foster. H.. 1955. Paleozoic and Meso7oic rocks of the Gros i'entre. Teton. Hoback
and Snake River ranges. LVyoming: Geological Society of America Memoir 63. 90 p.
l\'iltschko. D.V. and Dorr. J . A . Jr.. Timing of deformation in O\.erthrust Belt and Foreland of Idaho. Li'50rning and
I'tah: American Association of Petroleum Geologists Bulletin. \ . 67. p. 1304.1322.