THE STRATIGRAPHY OF THE UPPER CRETACEOUS ROCKS NORTH OF THE, ARKANSAS 

RIVER IN EASTERN COLORADO 

By c. H. DANE, w. G. PIERCE, and J. B.-REESIDE, Jr. 

ABSTRACT 

A comparison of the _ stratigraphic sections of the rocks of 

Benton age in western Kansas and the southern foothill region 

of eastern Colorado indicates the probability that the lower 

"11.embers of the Greenhorn of Kansas merge westward into the 

nnper part of the Graneros shale of the foothills, the Green-

!rn of the type locality being much thinner than that of western Kansas and the Graneros of the type locality being much 

thicker than the Graneros of western Kansas. The Greenhorn 

of Prowers County, Colo., north of · the Arkansas River, has, 

however, the thickness of the Kansas Greenhorn, and the member subdivisions of the Greenhorn made in Kansas can also be 

recognized in Prowers County. 'J'he Carlile shale, which overlies 

the Greenhorn, contains at the top the persistent but variable 

Codell sandstone member. This member, which contains the 

Carlile fauna, is believed to have been deposited. in shallow 

water under conditions that were maintained fori ~onsiderable 

period of time. The faunal discontinuity between the Carlile 

and the overlying Niobrara formation ·is believed to represent 

a time lapse, although no evi~ence was seen to indicate subaerial 

erosion of the Carlile. 

In the foothill region of Colorado the Niobrara consists of 

the Timpas limestone member and the overlying Apishapa shale 

member. The Timpas includes in its upper part limy shales and 

thin limestone beds which, in Kansas, have been excluded from 

the basal Hays limestone member. The Hays limestone member appears to be a more satisfactory lithologic and faunal 

unit, and the name is therefore extended into that part of Colorado east of the foothills and north of the Arkansas River. 

Similarly, the name "Smoky Hill" is extended from the chalk 

member of that name in Kansas. to the marl member overlying 

the· Hays limestone in eastern Colorado. 

The basal portion of the overlying Pierre shale consists of 

black shale nearly devoid of fossils, to which the name "Sharon 

Springs member" is extended from the type locality in Wallace 

County, Kans. The overlying portion of the Pierre shale was 

not sufficiently studied to warrant the establishment of member 

names, although the "rusty zone", ''tepee zone", and "transition 

zone" of previous authors are recognized. 

The known invertebrate faunas of the several formations 

are briefly described, and the fauna of the overlying Fox Hills 

sandstone is also discussed beca.use of its close relationship to 

the fauna of the "transition zone" of the Pierre shale. 

INTRODUCTION 

gion were made by C. H. Dane in the fall of 1933. 

The invertebrate faunas collected during this reconnaissance have been studied by J. B. Reeside, Jr., who 

has also contributed many hitherto unpublished data. 

Although detailed work has been done in several areas 

in this region, no summary of the stratigraphy has been 

published for many years, and it has therefore seemed 

appropriate to publish the data gathered in the present 

study and to correlate them with the previous work. 

Because of the large size of the area traversed, it was 

not possible to make a rigorous examination of any 

specific problem, though considerable information . was 

obtained concerning the lower portion of the Upper 

Cretaceous. 

The location of the area within which most of the 

observations here recorded were made is shown on the 

index map (fig. 9), which also shows the location of 

some areas covered by previous reports. 

The geologic map (pl. 64) shows the areas of outcrop 

of the principal stratigraphic divisions with reference 

to the major geographic and cultural features of the 

region. The base was taken from the United States 

Geological Survey map of Colorado compiled in 1922, 

with minor modifications of land lines, drainage, and 

culture observed by the writers in the field or suggested 

by more recently compiled maps. · The mapping was 

done wholly by sketching, either on county maps _or on 

so-called military maps of the Colorado State Highway 

Commission, which show towns, railroads, and graded 

roads with considerable accuracy. 

The formations exposed are of Upper Cretaceous 

and Tertiary age. The · Cretaceous rocks were hiid 

down· in the widespread seas that covered much of 

the western interior of the · United · States· at that 

time. During the period in which the earlier deposits 

accumulated there was smne differential warping of 

the crust, but subsidence later became n1ore pronounced 

in an area centering somewhat north of Denver. · During' the epoch of subsidence a basin was formed which 

During parts of the summers of 1931 and 1932 C. H. filled with sediments as it subsided, the later Cretaceous 

Dane and W. G. Pierce spent about 8 months on a rotiks th'us having a much greater thickness toward the 

reconnaissance examination of a large area of the High ;central part of the basin. Toward the · end of the · 

Plains of eastern Colorado north of the Arkansas Riv ~ ;cretaceous and early in the Tertiary the rising Rocky 

A few additional observations on the lower part of the: iMountains shed great quantities of debris eastward to 

Upper Cretaceous section in the southern foothills re- form a series of nonmarine deposits. Although the 

207 
208 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 19 3 6 

seas had withdrawn, the basin continued to subside ceous rocks are soft and easily erodible, and even where 

until deposition ceased, probably in early Eocene time. not concealed by younger deposits they may be weathThe latest structural movements accompanying the rise ered into smooth ungullied sod-covered slopes in 

of: t:he Rocky ·Mountains completed the outline of the which the details of the lithology cannot be determined. 

sedimentary basin and made it a structural basin . as No attempt has been made to indicate on the map the 

·well. There ensued a period in which erosion was p:r:e- istri~ution of terraces, wash, or eolian deposits, which 

dominant, and the main outlines of the present areal in places conceal the Tertiary as well as the Cretaceous 

geology of the Cretaceous rocks were formed by the rocks. The extent ·of the present alluvial plain of the 

beveling of the inclined strata. Somewhat later, in Arkansas River is shown only approximately. 

middle and late Tert~ary time, , gr:avelly debris was 

I 6• 104° 102.0 

WYOMING .

! NEBRASKA 41·1--------r--~-4--,.-----,----r---.+---+1. 

.I __ j __ _ 

i fJ) 

~~lj_t ·. · .. ·.· 39° 

fJ) 

106" 

FIGURE ~Index map ~;~howing location of area in eastern C,olorado 

considered in this report (sho-wn by short-dashed lines) and ., of some 

areas described in previous reports, including folios of the Geologic 

Atlas of the United States (cross-lined) and. reports of the Colorado 

and Kansas Geologi<;al Surveys ·(dotted). 

swept out from the mountains by streams, and widespread though comparatively thin deposits of gravel 

and sand were laid down. The great plain thus built 

up sloped gently eastward, its materials concealing the 

underlying Cretaceous rocks far east . of the mountain 

front. . Renewed erosion in still later epochs has cut 

away much of thi~ plain and exposed the underlying 

rocks, . but .large areas of it still remain, and beneath 

these areas the Cretaceous rocks are wholly concealed. 

Even where the present surface has been-cut-below the 

level of the High Plains ,deposits, there are extensive 

areas where the Cretaceous rocks are concealed by relatively late terrace deposits at several levels, surface 

wash, and sand dunes, and the alluvial deposits of the-. 

larger streams. For the greater part also the CretaEARLIER WORK 

The first con1prehensive studies of the Cretaceous 

stratigraphy of the Arkansas· Valley were begun by 

G. K. Gilbert in 1893 with the mapping of the Pw3blo' 

quadrangle. 1 Mapping of the Apishapa _quadrangle 2 

:was begun in the following year, and a subsequent 

reconnaissance of the more easterly portion of the valley led to the publication in 1896 of ·Gilbert's report 

on. the underground water of the Arkansas Valley in 

eastern Colorado.3 The description of the Denver 

Basin,4 a more northerly area of the foothills aud ·. adjoining plains, was published at about the same time, 

though based on field work of the preceding decade. 

In- the succeeding years several other folios 5 were · 

issued that followed closely the outlines oft~e stratig- . 

raphy _laid down by Gilbert and that dealt with. areas. 

pf the southern foothills and adjoining plains: In 1906 

Darton's broader study 6 of the geology and underground water of the Arkansas Valley was published. 

With the appearance of the Castle Rock foljo 7 in 1915 

and the Colorado Springs folio 8 .in 1916 the earlier . 

phase of the geologic study of the region came to an end, 

and most of the larger features of the geology had been 

outlined. Several detailed .repo:cts on itreas. in the Ar~ 

kansas Valley in Colorado ha 've since app.eared," and 

some features of the .stratigrapl_lic relations have peel) 

touched upon in other' papers.· In recent ·years. several 

detailed studies have been made of the Upper Creta- ' 

ceous rocks in western Kansas. 9 In these studies fi~er 

division of the Cretaceous beds has been made th~n in · 

1 Gilbert, G. K., U. S. Geol. Survey Geol. Atlas, Pueblo folio (no. 36), 

1897. . 2 Stose, G. W., U. S. Geol. Survey Geol. Atlas, Apishapa folio (no. 

l86), 1912. . . 

· 3 Giloert, G. K., U. s: Geol. "Survey Utli Ann. Rept., pt: 2, pp. 351-601, 

:1896: 

: 4 Emmons, S. F., Cross, Whitman, and Eldridge, G. H., Geology of the 

Denver Basin in Colorado: U. S. Geol. Survey Mon. 27, 1896. 

I 5 u. s. Geol. Survey Geol. .Atlas, Elmoro folio (no. 58), 1899; 

;walsenberg folio (no. 68), 1900; Spanish Peaks folio (no. 71), 1901; 

;Nepesta folio (no. 135), 1906. . . . · ., , . · 6 Darton, .. N. H., Geology _and underground waters p! _ t4e Arkansas 

Valley in eastern -Colorado: U. ·s. Geol. Survey Prof. Paper ·52, '1906. 

' '1 U. S. Geol. Survey Geol. Atlas, Ca~tle :&ock folio (no. 198), 1915. 

, s.u. S. Geol. Survey Ge<il. Atlas, Colorado Springs folio (no. 203),-

1916. . 

• 9 Bass, N. W., Geologic investigations in western Kansas; pt. 2, Ge'. 

ology of Hamilton County : Kansas G~oi. Survey Bull. 11, 1926. Elias, . 

M. K., The geology ·of Wallace County, Kan·s.: Kansas Geoi. Survey.: 

Bull. 18, 1931. 
STRATIGRAPHY OF UPPER CRETACEOUS ROCKS. IN EASTERN . COLORADO 209 

the rocks of equivalent age in eastern Colorado. Although the observations record~d in this paper were 

made in reconnaissance, they show that some of the 

smaller units set up in Kansas can be recognized also 

· in eastern Colorado. Much of the area offers small 

·promise of results to be obtained from detailed work~ 

. but in places exposures are sufficient to justify more 

careful stratigraphic study than has yet been carried 

out. 

THE FORMATIONS 

In the area shown on plate 64-the Upper Cretaceou$ 

rocks include the formations from the Dakota sand+ 

· stone to the lower part of the Pierre shale. West and 

north of the mapped area the higher part of the Pierre 

shale · is present, overlain by the Fox Hills sandstone, 

the Laramie formation, and the Dawson arkose. Th~ 

·. uppermost beds of the Pierre shale and higher Creta~ 

' ceous rocks are 'not discussed at-length in this paper~ 

.. but certain observations, particularly the record o£ 

fossil collecti~ns, are given. ! 

The stratigraphic divisions of th~ Upper Cretaceoud 

rocks de_scribed in this paper are ·as follows: l 

sectio~ is exposed south of the Arkansas River it is described as a hard massive or qu~rtzitic sandstone.U 

Qarbonaceous and lignitic layers and fossil \ leaves of 

'Upper Cretaceous age are found locally in the sandstone. 

GRANERO.S SHALE 

E-xposures of the next overlying formation; ·the 

Graneros shale, occur in a narrow belt north of· the 

Arkansas River and extending from a point south of 

Fort Lyon on the east to a point south of Wiley ·on the · 

west, and also east of Holly in a small area near · the 

Kansas-Colorado State line. . · · 

The Graneros shale was· defined by Gilbert 12 as a 

laminated argillaceous shale fro:m 200 to 210 feet thick, 

the lowest formation of the · Benton group. It w~s 

named from a creek in the northern part of the W alsenburg quadrangle. · · 

The :formation consists predominantly o£ dark-gray 

to black fissile noncaJcareous shale. Because it is soft 

and e~sily erodible and because of the wi<lespread 

deposition ·of terrace sands _along the··Arka:risas River, 

exposures are so small and scattered that little informa- Fox Hill sandstone. 

Pierre shale : 

· Transition zone. 

tion on the details of lithology{th~ckness, 'arid strati-

-! graphic relations can be obtain~H in this' atea~ Tepee zone. ! The basal part of the· Graneros is expose=d )at· various 

Rusty zone. 

Sharon Springs shale member (barren zone). 

Niobrara formation: (Foothill region, Colo.) j 

Smoky Hill marl member.}1 {.Apis~apa shale member. ! 

Hays limestone member. Timpas limestone member. ; 

Carlile shale: · 

Codell sandstone member. 

· Blue Hill-shale member. 

places from sec. 4, ·T. 2& S., . :R. 51 W~, ea~t\fard t6 the 

southwestern part of T.' 22 · S.; R. 49 W~ ·. The rbasal 

Graneros in this area consists of well-bedded nonsandy 

shale, witp. thin bentonite beds at places. _ AlthotigP, 

the basal contact was everywhere concealed, ' there 

Fairport ·chalky shale member. 

Greenhorn limestone. 

seems to be an abrupt change i~1 lithology · from th_e 

cross~bedded sandstone of the underlying Dakota sand1 stone. In other areas there !s a transition zone of 'sahdy i 

Graneros shale . . ! shaleatthe base of the Graneros. Iri Hamilton County, 

Dakota sandstone. 

DAKOTA -SANDSTONE 

1 Kans.;the_basal 8 or 10 feet of the formation contains 

I lenses of' impure sandstone and sandy shale and layers 

t of iron concretions 2 to 8 inches in' diaineter.18 South of I 

f. the· Arkansas River, in the La· Junta area,14 several' feet · The Dakota sandstone, which is the basal formation! of alternating shales and sandstones at the top 0£ the 

of the Upper Cretaceous series of this region, crops out! Dakota form a transition to the overlying Graneros, 

·'in a narrow strip adjacent to the alluvial plain alongi ·and siniilar transitional relations h~~e been obs~rvea 

·the north side of the Arkansas River and extends from! in the ... vicinity of Pueblo15 and of Co-lorado Spribgs:~6 the_ northwestern part of T. 23 S., ·-R. 51 W., to the/ 

southwestern part o~ T. :~ S., R. 4_7 W. Only the upperj 

part _of the formatiOn _ ~ exposed. In the exposuresi 

observe~ by t~e writers ~ co~sists principally of buff; 

and white, uniformly fine-grained, cross-bedded sand-! 

stone, with weathered su faces pitted. As much as 40: 

feet of sandstone of this type is exposed at one locality,: 

but elsewhere the expose thickn~ss is much less. The 

total thickness is somewh t variable but probably does 

not exceed 100 feet.10 ere a more nearly co~plete 

I 

10 Duce, .T. T., Geology of pa ts of Las Animas, Otero, and Bent 

Counties; Colorado Geol. Survey Bull. 27, pt. 3, pp. 89-90, 1924. 

u Darton, N. H., Geology and u~dergrorind wat~r~ of the A~kansas Valley in eastern. Colorado: U. S . . Geol. Survey ·Prof. Paper 52, pp. 

25-27, 1906. 

u Gilbert, G. K., The underground water of' the Arkahs:fs ValleY' fn 

eastern Colorado : U. S. Geol. Survey 17th -Ann., Rept., pt. 2, pp. 564, 

570, 1896. 

1a Bass, N. W., ·Geologic investigations in western Kansas, pt. 2, 

Geology of Hamilton County: Kansas Geol. Survey Bull. 11, p. 72, 

1926.. ' . 

u Patton, H. B., Underground water possibilities for stock and 

domestic purposes in the La Junta area, Colo.-: .Colorado Geol. Surv:ey 

BulL 27, pt. 1, p. 14, 1924. . . 

15 Gilbert; G. K., U. S. Geol. Survey Geol. Atlas, Pue~lo folio .. (J?.O. 

36), p. 3, ~897. ' 

16 Finlay, G. I., U. S. Geol. Survey Geol. Atlas, Colorado Springs folio 

(no. 203), p. 8, 1916. 
210 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 19 3 6 

In ::flamilton County, Kans.,17 the Graneros shale is 

fro:r.16.0 to 65 feet thick. It is believed to have about the 

same thir'.kness in the extreme eastern portion of the 

Arkansas Valley in Colorado, where, in addition, the 

.:;arne divisions of the overlying Greenhorn limestone 

may be recognized as in Hamilton County. In the 

:::wrtheastern part of Bent County, Colo., however, the 

Graneros shale is estimated by the writers to be about 

200 feet thick, and although the overlying Greenhorn 

limestone is there incompletely exposed, it seems to be 

much thinner than in western Kansas. This relation 

suggests that the Graneros has thickened westward at 

the expel?-se of the Greenhorn. In the western part of 

Bent County and in Otero .County 1.s the Graneros has 

a. thickness of about 200 feet, and farther west 19 it is 

from 200 to 220 feet thick. In . a section measured by 

the writers at Colorado City, west of Colorado Springs, 

the Graneros shale is 210 feet thick. 

Lithologic subdivisions of the ·Graneros were not distinguishable in the small scattered exposures observed 

within the area covered by this report. In the region 

of La Junta and .farther west in the Arkansas Valley 20 

the middle portion of the Graneros includes nearly-black 

shales ·which contrast with ~orne what lighter colored 

shales above and below. The subdi:vision into a nearly 

black middle portion and lighter-colored upper and 

lower portions is also recorded farther south in the 

vicinity of Walsenburg and Tripidad.'

21 The thi knes~ . 

in those localities is given as. 200 to 210 feet. This it 

also ab:;ut the thickness of· the Graneros exposed at a 

locality about.10 miles northwest of Vermejo Park, on 

the .east. flank of the Sangre de Cristo Range, in New 

Me4ico near its northern boundary. A calcareous concretionary zone occurs at 30 to 40 feet above the base,: 

and a thin calcareous sandstone or sandy limestone 

o::curs .45 to 50 feet below the · top . . In the Apishapa 

quadr~ngle 2 2 a . bed of impure,-sp~ringly fossiliferour 

lin:e.:::tone 12 to-. 14 inches thick lies from 65 to 75 feet 

above the base, and a 6-inch bed of hard sandstone 

oc urs a few feet above the limestone. At 80 feet above 

the . base · ,of. a section of Graneros measured by the 

'"TitP.:rs at Colorado. City, .west" of Colorado Spring~; 

thei·ejs a prominent thin-bedded sandstone 1 foot thi<;k 

with 2 feet 6 inches of gray sandy shale below it. Over 

the western part of the area des¢ribed ip. this report a;nd 

a considerable region to the west and south the Graneros 

. 11 Bass,· N. W. , op. cit., p. 72. 18 Patton, H. B., op. cit., p. 14. 19 Gilbert, G. K., op. cit. (Pueblo folio), i>. 3. Fisher, C . .A., U. S. 

Geol. Survey Geol. Atlas, Nepesta folio (no. 135), p. 2, 1906. 20 Patton, H. B., op. cit., p. 14. Gilbert, G. K., op. cit. (Pueblo 

folio), p. 3. · Fisher, ·C. A., op. cit.', p. 2. Stose, G. w., U. s. Geol. 

Survey G~ol. Atlas, Apishapa folio (no. 186), p. 5, 1912. 21 U. S. Geol. Survey Geol. Atlas, Walsenburg folio (no. 68), p. 1, 

1900 ; Elm oro folio (no. ' 58), p. 1; 1899. 

22 Stose, G. W., op. cit., p. 5. 

seems to maintain a fairly uniform thickness, and it is 

likely that a few individual beds in it may be recognized and traced over large areas. 

Bentonite beds from a fraction of an inch to a few 

inches thick occur at several horizons within the 

Graneros. Although they afford a potentially useful 

means of detailed correlation, the inadequacy of exposures over much of the portion of eastern Colorado 

here discussed makes it unlikely that such detailed 

correlation can be effected without very careful recording of the formation where it is penetrated by wells. 

Southwest of Las Animas a bed of bentonite 3 feet 

thick 23 occurs about 85 feet above the b.ase of the 

Graneros and has been recorded as "talc" in several 

wells drilled for water in the La Junta region. No 

beds of equal thickness are known elsewhere in this 

region. Beds of similar thickness have, however, been 

recorded in the lower part of the Benton 24 shale of 

northeastern Colorado, which is the equivalent of the 

Graneros shale and the overlying Greenhorn and Carlile formations of the Arkansas Valley. 

The fauna of the Graneros shale is scanty and imperfectly known. A small simple oyster somewhat larger 

and more regular in form than Ostrea congesta is 

abundant in sandy limestone near the top of the Graneros shale in the region of the Apishapa quadrangle. 25 

Gilbert, during his work in the Ar,kansas -Valley, collected from the lower part of the Graneros the following fossils, largely unnamed species : Corals, several 

species; pelecypods, Leda sp .. , A1·ca sp., Inoceramus aff. 

!. bellvuensis Reeside, Pteria sp., Pecten sp., Luci~a 

sp., Dosinopsis sp.; scaphopod, Dentalium sp; gastropods, Turritella rwhitei Stanton, M es.ostoma occidentalis 

Stanton, Oinulia? sp., Actaeon propinquus Stanton; 

cephalopods, a nautiloid, M ammites sp., M etacalycoce:ras sp., B orissjakoceras sp., Turrilites sp. . Bass 26 

:'eported Ostrea n. sp., small simple type, and lnoceramrus, n. sp. related to I. fragilis Hall and Meek from 

western Kansas. 

A section of the Benton shale was measured by the 

writers !;\long the south fork of 'Bear Creek 1.3 miles 

sQuth of the place where the mai1~ road from Mount 

Morrison to Denver crosses the Dakota sandstone hogback. . About 10 feet above the top of the Dakota sandstone and thus in· beds equivalent to the Graneros shale 

the writers collected H olcolepis pulchellus Cockerell 

and Leucichthyops vagans Cockerell, species originally 

described from the Mowry shale. Several other small 

lots of fossils were collected at horizons 250 to 300 feet 

23 Patton, H . B., op. cit., pp. 14-15. 

24. Mather, K . F., Gilluly, James, and Lusk, R. G., Geology and oil 

and gas prospects of northeastern Colorado : U. S. Geol. Survey Bull. 

796, pp. 81-83, 1928. 25 Sto-se, G. W., op. cit., p. 6. 

26 Bass, N. W., op. cit., p. 73. 
TR TIGRAP F UPPER RETACEO S ROCKS IN EASTERN COLORADO 

cnl n in hi 

in he f ll \Yino· li .t: 

REE HORN LIME TO E 

\ 'all y in 

ol. u n • y 17th nn. R pt., pt. 2, pp. 

lion ot Bridge Or elc member ot G1·eenhor-n limestone 

on t t ide ot h y nne Or k in Prowers County, Colo. 

P' t. in. 

hard y llowi h-gray ir6 

6 

6 

ton , gray, with I noceramtts labiatttB- ------------- 2 6 al d _________ ______________ ______________________ 3 6 

6 

4 

4 

6 

8 

6 

6 

6 

8 

5 

3 

11 

5 

6 

10 

4 

5 

2 

3 
OITER TRIB TI0.1: TO GE ER L GE LOGY, 19 3 6 

Par·tiaZ section ot top of (h· nllorn 

Garlil shal ~n 8 . 7 T . 2 

Fairport balk bale member of arlil hal : 

balky hal . Ft. 

Lim tone, gray, with Ino ramus ___ ____ _________ _ 

Chalky bale------------------------------------- -

Lime toue, gray-----------------------------------

Chalky ·hale ------------------------- ------------ _ 

Lime tone, white, bard; break in urving pin . 

and flat lab · in part w ath ring to :r ll wi b gray _____________ ____ ___________________ ------

Partial tion ot top of 1· uhorn lim ton and ba · o{ 

Gar·Zile sllale in · c. 7, T. f · ., R. 44 IV.- ontinue<l 

!!'airport balky hal . m rnb r of arlil bale.- ntd. 

tbin-b dd L----------------- 3 

into thin chip -------------- 4 

Partial thi kne ---------------------------- 0 

10 

10 

4 

10 

f) 

2 

G 

1 

dant I no emtnu labiatu -------------------- --- 7 

'ba lky marl, flaky and pap r-b dd d in part_ _____ 1 

Lim t n , halk3, gray; br ak into irr o-ular flat 

hip._______________________________________ ____ 3 

halk marl, yell wi b gray, flaky and pap r-b dd d 

in p rL---------------------------------------- 1+ 

ction ot upp r part of Gr nhorn lim tone 1% 1nil 11orth 

ot M la e Ft. in. 

hal , marl ---------------------------------------- 5+ 

Lim ton ----------------- tan _______----

____________________ --------------- ------ 4 ____ 5 

Lim tone, ra ------------------------------------- 2 

hal , nl ar u ------------------------------------ 1 1 

5 Lim ton , gray, with lnocrrarnu labiatu ------------ 3 
T 

23 

s 

38 

104 

U. 8. GEOLO ICAL S RYEY PROFESSIONAL PAPER 186 PLATE 64 

E LO IC MAP OF PART OF EASTERN COLOil NORTH OF THE RK AS RIVER. 

Numbel'8 in circles indicate locat.ion ( gr phio seotio011 io figur 11 . 
• J -~ :-
STRATIGRAPHY OF UPPER CRETACEOUS ROCKS IN EASTERN COLORADO 213 

Section of upper paTt of Greenhorn limestone 1% miles north 

of McOlave-continued 

Ft. in. 

Chalky marl, tan, with shell fragments ____________ .:. __ 3 

Limestone, gray_____________________________________ 3 

Marl, tan ___________________________________________ 1 3 

Limestone, light blue gray, with Inoceramus labiatus__ 5 

Marl and shale _____________________________________ 2 

Limestone, marly___________________________________ 6 

Shale and marl _____________________________________ 1 5 

Limestone, light gray-------------------------------- 6 

Shale, calcareous ____________________________________ 3 6 

Limestone, light gray-------------------------------- 4 Marl _______________________________________________ 2 6 

Limestone, blue gray, with InocerarrtJUs labiatus_______ 10 

Marl, tan-------------------.------------------------ 10 

Limestone------------------------------~----------- 3 

Marl, tan-------------------------~----------------- 8 

Limestone, blue gray, hard-----------------~--------- 3 

Marl, with a small amount of limestone ______________ 2 

Marl and shale, buff________________________________ 8 

Limestone, gray_____________________________________ 5 

Marl--------------------·--------------------------- 1 5 

Limestone, granular, soft_ ____ ..:.______________________ 3 

Marl, shaly, tan, with Inoceramus labiatus___________ 7 

Limestone, white to light gray_______________________ 9 

Marl, with a small amount of limestone _______________ 2 10 

Limestone, gray, with Inoceramus labiatus____________ 5 

Marl, tan ___________________________________________ 1 

Limestone, white____________________________________ 6 

Marl, tan ___________________________________________ 1 3 

Limestone, blue gray-------------------------------- llh Marl _____ .:._________________________________________ 10 

Limestone-----------~----- -~---------------------- ~ 11h 

Marl,. tan ___________________________________________ 1 

Limestone, light gray-------------------------------- 6 

Marl_______________________________________________ 2 

Limestone, blue gray, hard__________________________ 1112 

Marl,· tan and light gray-~--------------------------- 1 8 

Limestone, blue gray-------------------------------- 4 

Marl, tan and dirty brown ______________________ _:_ ____ 1 ± 

Limestone, light gray, vertically jointed ___ ,___________ 4 

Marl, tan___________________________________________ 10 

Limestone; white____________________________________ 3 

Marl, tan___________________________________________ 11 

Bentonite___________________________________________ 7 

Shale, chalky _____________________________________ .:__ 7 

Limestone, white____________________________________ 3 

Shale, chalky tan ___ .:. _______________________________ 6 

Limestone, white____________________________________ 10 

Shale, chalky tan___________________________________ 6 

Limestone, white-------------------------------~---- 10 

Marly chalk------------------------~--------------- 2 

Total measured ______________________________ 56 81h 

Small exposures of the upper part of the Greenhorn 

limestone in the SW% sec. 16, T. 22 S., R. 50 W., along 

the western part of the south line of sec. 8, T. 22 S., 

R. 50 W., in the SE% sec. 11, T. 22 S., R. 51 W., and in 

the northern part of sec. 35, T. 22 S., R. 53 W., show 

that it persists westward as a lithologic unit of alternating limestone and chalky shale beds, but its thickness is not known, and exposures of the lower part were 

not observed. 

77388-37-2 

In the NW:JUNW% sec. 5, T. 24 S., R. 54 W., south of 

the Arkansas River, exposures of Greenhorn limestone 

about 30 feet thick show that it consists of beds of white 

limestone from 4 to 8 inches thick interbedded with 

gray calcareous shale in beds 6 to 12 inches thick. 

I nocera1nus labiatus is present in abundance at these 

exposures. 

In the Pueblo quadrangle 30 the Greenhorn has a 

thickness of 35 to 50 feet. East of that area, in the 

N epesta quadrangle,31 it has an aggregate thickness of 

50 feet, and to thesouth, in the Apishapa quadrangle, ~ 

it is reported to be about 30 feet thick. In the vValsenburg quadrangle it is described as consisting of layers, 

from 3 to 4 inches thick, of dove-colored limestone, 

separated by partings of gray shale. The aggregate 

thickness is about 30 feet. At a locality 10 miles northwest of Vern1ejo Park, on the east flank of the Sangre 

de Cristo Range, in New Mexico near its northern 

boundary, the Greenhorn, as separated by the writers; 

includes 25 feet of such alternating limestones and 

shales and also 25 feet of hard gray limy shale overlying them. The Greenhorn may also be recognizeLl 

farther west in southwestern Colorado and on the east 

side of the San Juan Basin in northwestern New l\1exico 

as a similar thin unit of alternating beds of limestone 

and shale. In the La Junta region 33 the total thickness 

is about· 50 or 60 feet. In view of the fact that the 

thickness of. the Greenhorn in western Kansas is from 

100 to 130 feet,. it seems likely that the lower members 

of the Gr~enhorn in Kansas merge westward into the 

upper part of the Graneros shale. This inference jg 

supported by the westward thickening of the Graneros 

shale. 

The thickness of the rocks of Benton age in the 

aggregate remains nearly the same from wes~ to east, 

as shown by the plotted logs of several wells (fig. 10) 

and also by the thicknesses given for the several formations by writers on various areas (to defer, for the 

present, consideration of an anomalously thin Carlile 

shale section in the La Junta region). The published 

descriptions of the upper portion of the Graneros where 

it has a thickness of 200 feet also suggest that its 

content of calcareous shale and limestone is greater 

than that of the Graneros of western Kansas and that 

it may represent an equivalent of the lower portion of 

the Greenhorn of Kansas. For example, in the La 

Junta region 34 the Graneros contains thin liiil.y bed,s 

40 to 50 feet below the top of the formation, and in the 

Apishapa quadrangle 35 a thin fossiliferous platy sandao Gilbert, G. K., U. S. Geol. Survey Geol. Atlas, Pueblo folio (no. 

36), p. 3, 1897. 

81 Fisher, C. A., op. cit., p. 2. 

:12 Stose, G. W., op. cit., p. 6. 

aa.patton, H. B., op. cit., p. 15. 34 Idem, pp. 14-15. 35 Stose, G. W., op. cit., p. 5. 
214 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 19 3 6 

stone is found about 45 feet below the top of the Graneros. Farther west, however, in a section measured 

by the writers at Colorado City, west of Colorado 

Springs, the upper portion of the Graneros contains 

no limy beds. In this section the Graneros is 210 feet 

thick and the Greenhorn somewhat more than 20 feet. 

The width of outcrop of the Greenhorn as shown on 

the geologic map diminishes rather abruptly westward 

from the vicinity of \iViley. -

So far as known the Greenho~n in Colorado is transitional into the overlying Carlile shale as well as into 

the underlying Graneros shale. A paleontologic distinction between Carlile and Greenhorn is reported in 

western Kansas and may exist also in eastern Colorado. 

~ <( 

a: 

(0 

0 

z 

Locality 

Lunatia'! SP------------------------------------------ 2 

ExiteZoceras pariense (White)----------------------~-- 7 

1. 15743, Mount Morrison Bear Creek locality. (See p. 2:10.) 

2. 15818, sees. 16 and 17, T. 22 S., R. 50 W. 

3. 16068, NW14 sec. 18, T. 22 S., R. 44 W., along Cottonwood 

Creek. 

4. 16009', SW14 sec. 7, T. 22 S., R. 44 ,V. 

5. 16076, NE:l4 sec. 11, T. 22 S., R. 48 W . 

. 6. 16077, NW14 sec. 30, T. 22 S., R. 46 W. 

7. 16078, NE!4 sec. 12, T. 22 S., R. 49 W. 

The rarer species, however, include a considerable 

variety of forms. Reeside has under study collections 

from the Greenhorn limestone of the Arkansas Valley 

and the foothill region of Colorado that contain the 

following forms in addition to those listed 

above: EcJ:.tinoid, Sternotaxis.~ n. sp.; brachiopod, Crania n. sp.; pelecypods, Inoceramus cf. I. lamarcki Parkinson, Ostrea 

~ sp., Sauvagesia? sp. ; gastropods, 0 eri-

~ thium? sp., Anchura.~ sp., Aporrhais 

~ (Perissoptera) prolabiata White, Anisomyon.~ sp. ; cephalopods, N eoptychoceras 

sp., Baculites gracilis Shumard, Traqodesmoceras n. sp., W atinoceras .~ coloradoense 

(Henderson), Watinoceras? n. sp., Romaniceras n. sp., N eocardioceras septemseria- · 

tus (Cragin), Thomasites n. sp., Mammites 

n. sp., N eoptychites n. sp., Scaphites n. sp., 

Pseudotissotia ( Ohotfaticeras) n. sp., M etoicoceras w1hitei Hyatt, M etoicoceras cf. M~ 

irwini Moreman. Morrow 36 records Tragodesmoceras bassi l\{orrow from Colorado. 

CARLILE SHALE 

0 so 100 

Vertical scale 

>t< Mostly outcrop measurements Kans'b:s.Geolo,gicaiSurv_ey'Bu/1 II 

vi 

<f) The Carlile shale was named by Gilbert 37 from Carlile Spring and Carlile 

station, 21 miles west of Pueblo. It was 

aescribed as a gray argillaceous shale 175 

to 200 feet thick. In the Pueblo quadFIGURE 10.-Graphic sections showing the thickness of the rocks of Brnton age at 

various places in the Arkansas . Valley as given by drillers' logs of several well f., 

with a comparison of the stratigraphic section of these rocks as divided ·in Harpilc 

· ton County, Kans., and in the Nepesta quadrangle, Colo. 

The fossils recorded from the Graneros of eastern Colo-· rangle the upper fourth contains some sand, and the 

rado are of types also found in the Greenhorn and may . topmost"" portion is described as ·a yellow friable sandtp.erefore have come from shaly beds equivalent to the . stone. Farther east "the sandstone is often replaced 

lower part ·of the Greenhorn. . . :by a purplish limestone." Large septarian calcareous 

Fossils other than a few species of Foraminifera and ; concretions occurring 20 ito 50 feet below the top of 

Inoceramus labiatus are not con1n1on in the Greenhorn 1 the Jormation are also noted. . 

li:rnestone. Seven collections made by the writers corr: . In Russell County, Kans., the Carlile shale was 

tain the following species. The large numbers (15743, ; divi~ed into two n1embers, the Blue Hill shale member 

e~c.) in .tP,is and other lists. of localities are the num- : a~o~e and the Fairport chalky shale member 38 below. 

hers in the ·United States Geological Survey Mesozoic Th~se subdivisions were later recognized in _Ellis and 

invertBbrate collection. 36 Morrow, A. ·L., Cephalopods from the Upper Cretaceous of Kansas : 

Loc(tlity Jour. Paleontology, voi. 9, no. 6, p. 468, pl. 53, fig. 4; text fig, 1, 1935, 

GZobigerina SP---------------------.----------------- 1, 2, 3, 6 87 Gilbert, G. K., Th~ underground water of the Arkansas Valley in 

GZobotruncana sp _______________________________ :...._____ 2 !eastern Colorado: U. S. Geol. Survey 17th Ann. Rept., pt. 2, pp. 

J r 1 b · t S hl th · 1 2 3 6 7 565-566, 570, 1896. · · · noce a·mus ba ~a US c 0 eiiD--------------- , , , 4, 5, , ' as R b W W d B N ur Th - 1 f R 1 C • 1 u ey, . ,, an ass, . n ., e geo ogy o usse I ounty, 

Inocera·mtts SP-------------------·--------------------- 1 ; Kans. : Kansas Geol. Survey Bull. 10, p. 33, 1925. 
STRATIGRAPHY OF UPPER CRETACEOUS ROCKS IN EASTERN COLORADO 215_ 

Hamilton Counties. 39 In Ellis County a fine-grained 

sandstone about 20 feet thick at the top of the Carlile 

. shale was named the Codell sandstone bed of the Blue 

Hill member by Bass. The Codell sandstone bed was 

also found in Hamilton County, Kans., near the Colorado State line, where it consists of sandstone about 2 

feet thick in the upper part, underlain by 20 feet of 

sandy shale. The subdivisions of the Carlile shale made 

in Kansas are distinguishable also in the Arkansas Valley in eastern Colorado. As it is now generally regarded as desirable to eliminate the application of 

names to units of less than member rank, the Codell 

sandstone as herein described is considered to be a member of the Carlile shale, equivalent in rank to the Blue 

Hill shale member, which underlies it, and to the 

Fairport chalky shale, which is the basal member of 

the Carlile shale in the area of this report. The Codell 

sandstone has previously been recognized as a member 

of the Benton shale in northeastern Colorado. 40 

FAIRPORT CHALKY SHALE MEMBER 

In Hamilton County, Kans., the Fairport chalkyshale member consists of calcareous blue-black shale in 

the upper part, which becomes more limy and somewhat lighter in color downward. Thin beds of chalky 

limestone alternate with limy shales in the basal 35 

feet. The member as a whole has a thickness of nearly 

150 feet. The contact with the overlying Blue Hill 

was not sharply distinguished. At the base the Fairport lit~1ologically resembles the upper part of the 

Greenhorn limestone, but is paleontologically distinguishable from it. 

At most places in the area shown on the map this 

lowest member. of the Carlile is poorly exposed in con1-

parison with the two overlying members. There are 

some typical exposures of the upper part of the fairport in the -NW1;.4, sec. 28, T. 22 S., R. 41 W. The exposures consist of yellowish well-bedded chalky shale 

with rather numerous specimens of Ostrea sp., Inoceramus sp., fragmentary remains of fish, and rarer 

ammonites. -

The best exposures of the Fairport member are in 

the SE1;.4, sec. 6 and the NE1;.4, sec. 7, T. 22 S., R. 44 W. 

At the base it is n1uch like the upper part of the underlying Greei1horn, as shown in the measured section on 

page 212, but has possibly a somewhat more chalky 

aspect. The proportion of limestone diminishes rapidly upward, and the bulk of the exposures consists of 

chalky shale. In the SW1;.4,SE1;.4, sec. 6 a hard thinbedded oyster-shell limestone near the top of the Fairport makes a small ledge. There are, however, some 

39 Bass, N. W., Geologic investiga,tions in western Kansas, pt. 1, 

chalky marls above it, and the contact with the overlying Blue Hill shale n1ember is not sharply distinguishable. 

Small exposures in the northeastern part ofT. 22 S., 

R. 48 W., show that much of the Fairport there consists of chalkyn1arl with lenses of hard gray crystalline limestone a fraction of an inch thick. Oyster 

shE:Jlls are abundant, as are also impressions of Inoceramus shells. Beds of limestone as much as 1 foot thick 

are locally present. 

The contact between the Fairport and the overlying 

Blue Hill in sec. 27 and the NE1;.4, sec. 34, T. 21 S., 

R. 49 W., cannot be precisely set, but near the top of the 

Fairport is a bed 1 to 6 inches thick of very fine grained 

sandy crystalline lirnestone or calcareous sandstone: 

This bed is really an aggregate of lenticular beds 1 inch 

or less thick. Some of the lenses consist of closely 

packed oyster shells, and many of them carry broken 

Inoceramus fragn1ents, worn shark teeth, and oyster 

shells. Below the bed lie slightly calcareous wellbedded shales and marly shales. There is ap_parently · 

considerable variation in the lime content of individual 

beds, which range from one-sixteenth to one-half inch 

thick. The proportion of calcareous or marly shales 

increases downward, and the lamination of the rock 

becomes less regular and less distinct. The lowest exposures consist of light-gray chalky marl, with numerous fish scales, oysters, and Inoceramus impressions. 

At least 25 feet of the upper part of the Fairport is 

exposed. 

Somewhat more than 20 feet of chalky marl of the -

Fairport is alsq exposed in the SWlM sec. 9 and the 

NE1;.4, sec. 16, T. 22 S., R. 50 W. The basal part of the 

overlying Blue Hill n1ember is concealed. 

The Fairport chalky shale member is 14 7 f-eet thick 

in Hamilton County, Kans.,41 as determined from the 

log of a water well. N'O complete measurements of the 

member were made in eastern Colorado, but the member is estimated to be from 75 to 125 feet thick. 

In the La Junta region and farther west in the 

Nepesta and Pueblo quadrangles 42 the Fairport chalky 

shale member cannot be recognized from the descriptions of the Carlile shale given in the literature. In a 

section of the Carlile measured by the writers at Cblorado City, west of Colorado Springs, 55 feet of-gray 

limy shale underlies black noncalcareous shale and overlies gray limestone assigned to the Greenhorn limestone. 

BLUE HILL SHALE ME.MBER 

The Blue Hill shale m~mber consists predominantly 

of· black fissile nonc.aJcareous shale. In the lower part 

Geology of Ellis County: Kansas Geol. Survey Bull. 11, p. 26, 1926; 41 Bass, N. W., op. cit., p. 65. 

pt. 2, Geology o( Hamilton County: Idem, p. 63. 42 Patton, H. B., op. cit., pp. 42-43~ Fisher, C. A., op. cit., p. 2. 

40Mather, K. F., Gilluly, James, and Lusk, R. G., op. cit. (Bull. 796). Gilbert, G. K., U. S. Geol. Survey Geel. Atlas, Pueblo folio (no. 36). 

p. 81. p. 3, 1897. 
216 

NOil.\f~~O.:J 

~WSOIN 3"1\fHS 

SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 19 3 6 

there is some calcareous shale, and the unit 

is not sharply separable from the underlying Fairport. The uppermost part consists of slightly sandy shale, locally as much 

as 30 feet thick. In the upper part of the 

men1ber there are almost everywhere large 

calcareous septarian concretions. These 

are commonly" several feet in diameter and 

may be as much as 10 feet. The material 

of which they are composed IS a dull 

bluish-gray dense argillaceous limestone, 

but they weather yellowish tan. They are 

abundantly seamed with septaria of calcite 

in coarse translucent tan crystals. Conein-cone structure is developed on many of 

the upper surfaces. These large septarian 

concretions niay occu.r through a zone from 

5 to 30 feet in thickness, in most places 

about 10 feet. · The stratigraphic position 

of the zone, however, seems to vary somewhat, for they may occur from 20 to 55 

feet below the top of the Carlile shale. 

(See fig. 11.) Concretions of the same 

nature and at the same stratigraphic position in the Carlile shale have been described 

as far west as the Pueblo quadrangle 43 and 

also to the east in Kansas. 44 

CODELL SANDSTONE MEMBER 

At the top of the Carlile shale is a persistent but rather variable unit consisting 

of sandstone and sandy shale. This is the 

Codell sandstone member. · Where 01·iginally described in Ellis County, Kans.,45 it 

consists chiefly of sandstone with some 

shaly sandstones interbedded. At the base 

it grades into the shale beds of the Blue 

Hill member. The Co dell becomes less 

sandy southward, and in Hamilton County, 

Kans., it IS made up of about 20 feet 

of gritty shale containing thin streaks of · 

shaly sandst{me, overlain by 2 feet of sand 

at the top. 

At the easternmost locality observed by 

~ the writers (locality 17, pl. 64), along 

g Cheyenne Creek in Kansas, a third of a 

~ mile southeast of the northeast corner of :a 

§' sec. 17, T. 22 S., R. 41 W. (Colorado), 1 the Codell consists of 22 feet of soft, 

. nodular-weathering sandy shale. Near the 

"'" ~ 

p 

0 

s .a Gilbert, G. K., op. cit., p. 3. 

«Bass, N. W., op. cit., p. 63 . . 

45 Idem, p. 28. 
STRATIGRAPHY OF UPPER CRETACEOUS ROCKS IN EASTERN -COLORADO 217 

center of sec. 21, T. 22 S., R. 42 W. (locality 16, 

pl. 64), good exposures of the upper part of the Codell 

in ,a creek bank show that it consists of regularly 

bedded gray shale and lighter-colored, fine-grained 

shaly sand, with a few lenses of yellowish-gray hard 

sandstone. 

Near the center of sec. 18, T. 22 S., R. 44 W. (locality 

14, pl. 64), the upper part of the Codell is exposed in 

the wall of the Amity Canal ditch. At this place it has 

a somewhat different aspect. (See fig. 11.) At the 

top is a bed of soft earthy sand from 6 to 12 inches 

thick. Below this is a hard calcareous sandstone or 

sandy limestone 3 feet thick, of a rusty-brown color. 

Irregular bedding is outlined by sheets and lenses of 

softer earthy sandstone, which is cross-bedded within 

lenses. Fucoids interlace through the rock in great 

numbers. It also contains the typically prismatic fragments of Inoceramus shells. Below this hard bed is 

6 to 12 inches of soft earthy sand, which is underlain 

by soft gray sandy siltstone. In sec. 6, T. 22 S., R. 

44 W., the top bed of the Codell is a_ hard brown, 

slightly sandy limestone. It is underlain by soft sandy 

siltstone. Good exposures of the Codell were not 

observed for about 20 miles west of this locality. 

In a deep gully along the east side of the section -line 

road between sees. 10 and 11, T. 22 S., R. 48 W. (loT. 22 S., R. 50 W., to less than 5 feet in the western 

part of T. 22 S., R. 51 W. (See fig. 11.) In the 

south-central part of T. 22 S., R. 53 W., and thence 

southwestward there is no appreciable sand or sandy 

shale below the hard gray limestone. The limestone 

is, however, recognized to the west, in the La Junta 

region.46 

A petrographic examination of several specimens of 

the hard bed at the top of the Carlile shows that in 

most places it is a limestone that contains 3 percent or 

less of sand, but in some places it contains about 60 

percent of sand. In theSE% sec. 21, T. 21 S., R. 49 W., 

there are lenses of bituminous limestone in a bed as 

much as 6 inches thick of shale and sandstone cemented 

with lime, which overlies a hard sandstone bed that is 

as much as 18 inches thick. (See pl. 65, D.) The upper 

bed contains less than 2 percent of sand and the lower 

bed about 60 percent. The minerals in either the predominantly limestone or predominantly sandstone beds, 

after the CaC03 has been removed, are found to be 

practically the same and in roughly the same proportions. This is also true of the Codell sand. These 

minerals and their approximate proportions, as determined by M. N. Bramlette, of the United States Geological Survey, are as follows: 

Quartz, 50 percent or more. 

cality 13, pl. 64), however, the Codell consists of gray Orthoclase, 20 percent, more or less. 

sandy clay mottled irregularly with white and light- Chert grains, 10 to 15 percent. 

gray sand, and no hard beds were observed in it. At Indeterminate aggregates, 10 to 15 percent. 

several localities in the southwestern part of T. 21 S., A little sodic plagioclase. 

R. 49 "\iV., one or more beds of hard dark brownish- Zircon, green and brown tourmaline, rare. 

gray calcareous sandstone are present in the Codell. (so-called The writers regard the hard limestone Such beds were observed as m:uch as 12 feet below "N' b . ") th t f th C l'l · th t . . w enton at e op o e ar I e In e wes ern- the top and also near or at the top. Characteristically f tl f · t f th C d ll 

they contain fish scales, :fucoids, H aly1nen.ite8 major, . most part o. le area a~ orming par o . e . o e f 

d th f ·1 · · Th f th C d ll sandstone-In fact, as bmng the sole representative o an 0 er OSSI ImpreSSIOnS. e mass 0 e 0 e . s· 'l l' · ft bl 'It d t 1 b dd d d the Codell In that area. nni ar Imestones occur 

Ifs soth crumt Y tsih Y . san s oodne, 1 

poor Y

1 

e e ' f~n within or at the top of the more typical Co dell farther 

or e Inos par aving a n u ar or umpy sur ace . d ::e f 'd h k · t' 1 th h h t th d east having the saine abun ance Ol ucoi s, s ar In ver .Ica oug somew a wea ere exposures. ' . . ·nr t f 1 l't 8 ( 1 6

·4 d fi ll) th · h d teeth, fish fragments, and Impnnts and casts of the n es o oca I y p . an g. ere IS a ar . .

1 A h b h 

gray bituminous limestone at all exposures observed. same t~pes of Inverteb~ate fossi s. s as een s own, 

This limestone ranges from a few inches to several feet the~e l~m~stones contain a small percentage. ~f sand, 

in thickness and is believed to be the bed which has whiCh In Its more general aspects of compositiOn and 

been widely termed "Niobenton." Weathering to a grain size at least is like th~t of the more .sandy ~hase~ 

rusty-brown color and having a rough granular frac- of the Codell. Moreover, limestone of this type IS not 

ture, it has the appearance of a calcareous sandstone, present in either the underlying Blue .Hill or the overbut in reality it contains only a small percentage of lying Niobrara formation. As there IS good reason to 

sand. It is characteristically interlaced with fucoids believe that the nondeposition of sand at this horizon 

and carries numerous other fossils, including shark in the La Junta region and perhaps somewhat farther 

teeth. Even where thin it is notably persistent. It west is a local phenornenon, it seems better to regard the 

is much more resistant to erosion than the underlyinl! contemporaneous limestone at the same horizon as a 

beds and forms a definite escarpment. The thickness phase of the Codell. 

of the soft sandy shale and earthy sand of the Codell 

diminishes rapidly westward from about 30 feet in (6Patton,-H. B., op. cit., pp. 17-18. 
218 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1. 9 3 6 

About 5 miles west of Pueblo, ori the north side of 

the Arkansas River, the following section of the top of 

the Carlile was measured by the writers: 

Section of Carlile shale 5 mile.s west of Pueb~o 

Niobrara formation. 

Carlile shale: Feet 

Shale, gray ----=------------------------------------ 1 

Sandstone, light gray, hard, massive; weathers brown; 

Halymenites major and many fucoids, particularly 

near the base. Makes a vertical ledge, but the top 

few feet weathers back to a slope __________________ 15 

Shale, gray, and sandstone, thin-bedded, cross-bedded; 

with large ripple marks. This unit is separated by 

prominent shale partings above and below but is 

highly variable in lithology from place to place_____ 4 

Sandstone, ·earthy; weathers dark gray to almost 

white, with the most part a yellowish tinge; 

weathers into irregular small nodular masses and 

has a "knotted" appearance· on vertical or steep 

exposures; merges downward into sandy shale _____ 20 

Shale, sandy - -------------------------------------- 30± 

Shale, gray. 

Total measured-------- --------- ---- -----~ 70± 

limestone 2 to 4 feet thick. Still farther south, in the 

Spanish Peaks quadrangle, the Carlile includes 200 feet 

of dark-gray shale which grades near the top into 10 

feet of sandy shale and friable yellowish sandstone, 

with an overlying layer of purplish bituminous limestone 1 to 2 feet thick. 

The top of the Carlile, as observed by the writers on 

the north side of the Huerfano River in the extreme 

western part of the Walsenburg quadrangle, includes 

a considerably greater thickness of sand than is given 

in published descriptions. There is at least 25 feet of 

medium-hard light-gray fine-grained sandstone, buff 

colored and nodular-weathering in the lower part. 

Above this is 9 feet of soft sand and sandy shale, and 

at the top a bed 2 feet thick of hard brown-weathering 

gray limestone, which has an irregular under surface, 

contains abundant broken fossils and shark t~eth, and 

at the top appears to be interbedded with thin streaks 

of soft sandy shale. 

Sandstone at the top of the Carlile as a persistent 

lithologic unit apparently does not extend southward 

At Colorado City, west of Colorado Springs, the top into New Mexico, however, for at a locality northwest 

bed of the Carlile is a light-gray, thin-bedded, shaly of Vermejo Park (on Gold Creek west of old Pinafore 

sandstone from a fraction of an inch to 10 inches thick, post office) the upper part of the Carlile consists of 

containing vast numbers of Inoceramus. Below it is yellowish-gray shale with septarian concretions and a 

9 feet 4 inches of hard brown calcareous sandstone with few thin beds of hard, somewhat sandy, highly fosn1any fish teeth and . scales, Ostrea sp., Inoceramus, siliferous limestone. 

probably I. fragilis, Scaphites rwarreni Meek and Hay- The Cadell sand is a source of nonflowing artesian 

den, and Prionocychts wyomi%gensis Meek. This sand- water in a large area north ·of the Arkansas River, 

stone is ripple-marked, and the ripples have a wave especially in the vicinity of Eads and Chivington, but 

length of 2 to 5 inches. Farther north, at Perry Park, the water is not -potable and in eome wells is unfit for 

in the NW% sec. 24, T. 9 S., R . .-68 W., a si1nilar hard stock use. 

l]my sandstone about 4 feet thick was-observed. Nine samples of water were collected in the vicinity 

Sandstone has been found at the top of the Carlile in of Eads and Chivington from wells that obtain water 

many wells in northeastern Colorado; 47 and the Cadell from the horizon of the Codell sand. Partial analyses 

sandstone, 3 to 20 feet or more thick, has also been by the water-resources branch of the United States Georecognized on the outcrop in· the northern foothill logical Survey show that all the samples have a large 

region.48 It has been recorded also in most of the wells amount of dissolved mineral matter. The smallest 

drilled within the area of the map. Its absence in a amount of total dissolved solids in any sample was 1,700 

driller's log (see fig. 10) does not necessarily mean that parts per million and the greatest was over 10,000 parts 

the member is not present, as it may not have been per million; most of them were between 2,500 and 6,500 

noticed or recorded. parts. In all the samples the calcimn carbonate conThe top of the Carlile shale at the type locality 49 is tent was small, which is surprisl.ng in view of the fact 

a yello!v friable sandstone, which corresponds in strati- that the Cadell is overlain by 50 feet or more of limegraphic position and· general lithologic features with stone and locally itself contains calcareous beds. The 

the Cod~ll sandstone. Similar sandstone at the top of principal mineral constituents are sodium salts, bicarthe ·carlile has also been found farther south in the bonate, chloride, and sulphate. There is, however, a 

V.V~lsenb~rg quadrangle. The Carlile is there dark- large difference in the relative an1ounts of these congray shale, 170 to 180 feet thick; with 10 to 15 ·feet" of stituents, . even in wells that are a mile or less apart, a 

yellow sandstone at the top, capped -by bituminous · difference difficult to explain unless it is assumed that 

there is little or no lateral movement in the aquifer. A 47 Waldschmidt, W. A., Characteristics of older Cretaceous formations greater number of samples and a 1nore complete analyof northeastern Colorado : Am. Assoc. Petroleum Geologists Bull vol I · 

17 ~s no. 4, . pp. 415-41?, 1933. . . ., · si~ ~f each will be necessary before any tentative conMather, K. F., GIIIuly, James, and Lusk, R. G., op. cit . . (Bull. 796), 1· cluswns can be drawn as to the nature of the water 

p. 81. 

.o Gilbert,_ G. K., op cit. (17th Ann. Rept., pt. 2), pp. 565-566, 570.1 movement. 
STRATIGRAPHY OF UPPER. CRETACEOUS ROCKS IN EASTERN COLORADO 219 

POSSIBILITY OF- UNCONFORMITY AT TOP OF CODELL 

The Codell sandstone clearly represents the widespread occurrence of a set of environmental conditions 

different from those under which the deposition of the 

underlying rocks of Benton age occurred, or from those 

under which the overlying Niobrara formation was laid 

down. The Graneros and Greenhorn formations particularly give evidence that the sediments which compose them were deposited in moderately deep water, 

almost certainly below the depth of wave agitation-for 

individual beds even of small thickness persist for considerable distances. The lower part of the Carlile is 

also evenly bedded, but much of the Codell was clearly 

deposited within the reach of wave and current agitation. This is shown not only by its .sandy composition 

but also by the irregularity and cross-bedding which in 

places appear within it. Ripple marks have been observed at some places, and the shark teeth locally present are worn by abrasion. In a larger way the differences in lithology of the member from place to place 

indicate that it was deposited under the variable conditions to be expected in a shallow-water environment.-

Although in many plac~s thin and possibly locally 

absent, the Codell is surprisingly widespread, extending over most of eastern Colorado and western Kansas, 

with little significant variation in content or bedding. 

The Codell therefore seems to represent a time when 

deposition had filled a large area of the Cretaceous sea 

to a level at which the deposited material was within 

the reach of wave agitation. There is reason to believe 

that this condition was maintained for a considerable 

period. 

Johnson 50 has already summarized the evidence for 

an unconformity at the base of the overlying Niobrara 

formation, concluding that "Sufficient time, at least 

* * * elapsed to account for a complete cessation of 

deposition of one type, its alteration, and, in pla-ees, 

partial erosion and the development of conditions under 

which sediment of a completely new type was deposited." Certainly the abrupt change in fauna from 

the Carlile to the Niobrara suggests, even if the difference in lithologic character of the formations is discounted, that there was a l::tpse of ti1ne that pern1it~ed 

the development of new fa"9-nas. 

Johnson also cites as eyidence of unconformity ~ 

"thin-conglomerate containing plentiful fish teeth, wellrounded pebbles, and phosp"Qate nodules" which "occ-urs 

at the base of the Niobrara in all the areas studied~~' 

The pebbles are described as small, smooth, and well 

rounded, some as much as 3 inches in diameter. They 

consist chiefly of black chert but also of quartzite and 

5o Johnson, J. H., Unconformity in Colorado group in eastern Colorado: Am. Assoc. Petroleum Geologists Bull., vol. 14, no. 6, "PP· 

789-794, 1930. 

white quartz, and they occur together with phosphate 

nodules and shark teeth in a matrix of gray to brown 

crystalline sandy limestone. Although pebbles are also 

reported at this horizon in southeastern Colorado, none 

were observed by the writers in the outcrops extending 

from La Junta eastward to the Kansas State line. The 

possibly similar bituminous limestone with some shark 

teeth (and phosphatic nodules?) occurring there at the 

top of the Carlile has already been described (p. 217). 

This rock is, however, faunally and lithologically -allied 

with the Codell, to which it is assigned by the writers. 

The base of the overlying Niobrara formation is for 

the most part sharp and locally slightly irregular. Angular discordance was nowhere observed. Particularly from T. 22 S., R. 53 W., toT. 22 S., R. 51 W., however the basal contact of the Niobrara is somewhat ' -

obscure. The hard brown limestone assigned to the 

Codell by the writers appears.to grade upward into the 

overlying gray or·white limestone, and locally lenses of 

hard brown limestone like the underlying rock also 

appear in the basal Niobrara. Also the brown limestone itself becomes somewhat lighter colored eastward. 

The gradation, in fact, is so pronomiced that the hard 

brown limestone has been interpreted by Patton 51 as 

merging into the basal limestone bed of the Niobrara. 

Patton supposed that the occurrence near the bottom of 

the Niobrara of a fossil identified as Inoceramus labiatus, a character·istic Benton form, reinforced this interpretation. It is now known, however, that an Inoceramus much like -Inoceramus labiatus but distinct 

from it is present in many places in the lowest beds of 

the Niobrara. On the whole the appearance of the 

contact itself as seen by the writers neither suggests nor 

disproves unconformable relations. 

In smne areas local thinning of the Carlile suggests 

the possibility that the thinning may be due to erosion 

in those areas before the deposition of the Niobrara. 

Notably in the vicinity of La Junta_ the Carlile is abnormally thin. A section measured by Patton 52 shows 

a thickness of 130 feet. The logs of wells at Cheraw 

and Swink indicate that the Carlile is about 125 feet 

thick. (See fig. 10.) The Jogs of other :wells in the 

vicinity of La Junta show that the beds of Benton age 

are fr01n 50 to 75 feet thinner than to the east_ or 

west, and this thinning presumably also is due entirely 

to thinning_ of the Carlile. To the west, the_ Carlileis 

from 210 to 225 feet thick in the Nepesta quadrangle 53 

and 200 to 232 feet thick in the Apishapa quadrangle; 54 east of Las Animas it is- probably over 200 

feet thick, and in Hamilton County, in western Kansas, 

61 Patton, H. B., op. cit., pp. 18, 21. 

52 Idem, p. 17. 53 Fisher, C. A., U. S. Geol. Survey Geol. Atlas, Nepesta folio (no. 

135)' p, 2, 1906. 

""Stose, G. "V., U. S. Geol. Survey Geol. Atlas, . Apishapa folio (no. 

186), p. 6, 1912. 
220 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936: 

about 250 feet thick. If the writers' view is accepted, 

that the hard brown limestone above described is to 

be assigned to the Codell, the thinning of the Carlile 

in the· vicinity of La Junta takes place within the 

Carlile and not as a result of erosion at the base of the 

overlying Niobrara. The thinning is thus presumably 

to be ascribed to lesser deposition in that area. Th~ 

sandy phase of the Codell thins out over the same area, 

but its diminution from 30 feet to the vanishing point 

is not adequate to explain the total thinning of 50 to 

75 feet, part of which must therefore be due to thinning of lower beds in the Carlile. Lest the thinning 

of the sandy CodeU westward be interpreted as due to 

erosional unconformity at the base of the hard brown 

limestone, it should be pointed out that the sandy phase 

appears to merge westward into nonsandy beds by 

intertonguing and also that the distinctive zone of 

septarian concretions at the top of the Blue Hill shale 

member appears to maintain approximately its vertical 

distance from the base of the Niobrara across the area 

in which there is no Codell sand. (See fig. 11.) For 

some reason, therefore, the area about La Junta appears to have received less sediment than the surrounding regions. A plausible explanation for similar 

features in the Benton stratigraphy in other areas in 

eastern Colorado has already been offered by Johnson 

and Aurand.55 They suggest that structural features 

in existence during early Cretaceous time were rising 

slowly throughout Benton time, sufficiently high to 

divert or check the velocity of the submarine currents. 

"Part of the time their tops seem to have been approximately at the plane of. equilibrium, where, though the 

waters were free to pass over them, there was·almost no 

erosion or deposition, though deposition was taking 

place around the sides." -

As neither the local thinning of the Carlile and absence of the Codell member nor the details of the contact between the Niobrara and Carlile offer incontrovertible evidence of unconformity at the base of the 

Niobrara, the writers believe that the most valid evidence of such unconformity is the faunal discontinuity 

between the two formations. There seems no reason to 

suppose that the top of the Carlile emerged above sea 

level _ and was eroded. The faunal discontinuity seems 

ra:ther to indicate a period. at which the top of the 

Carlile sediments stood at wave base, with submarine 

erosion counterbalancing deposition. This was followed by subsidence or the deepening of the sea waters 

from some more remote cause, and in these less agitated 

waters the calcareous sediments of the Niobrara were 

deposited. 

55 Johnson, J. H., and Aurand, H. A. , A preliminary contribution to 

the Benton paleogeography of eastern Colorado : Am. Assoc. Petroleum 

Geologists Bull., vol. 13, no. 7, pp. 850-853, 1929. 

. FAUNA 

Fossils collected from the Fairport and CodBll 

members include the following forms: 

Codell sandstone member : Locality 

Inoceramus fragilis Hall and Meek _______________ 1, 2, 3, 7 

Inoceramus dirnidius White________________________ 7 

Inoceramus SP------------------------------------ 6 

Ostrea lugubris Conrad ____________________________ 2, 3, 4 

Ostrea SP----------------------------------------- 1 

Gryphaea SP-------------------------------------- 3 

Scaphites warreni Meek and Hayden_,_ ______________ 1, 2, 3 

Prionocyclus wyomingensis Meek ____________ 1, 2, 3, 5, 6, 7 

LamnafSP---------------------------------------- 1,3 

Ptychodus SP------------------------------------- 3 

Fairport chalky shale member : 

Inoceramus SP----------------------------:-------- 8, 9, 10 

Ostrea SP------------------------- -- --~---------- 8,10 

Baculites SP---------~---------------------------- 8 

Exiteloceras cf. E. pariense (White)-------------- 8 

Prionotropis woolgari -(Mantell)----------------- - 8, 9, 10 

1.15746, Colorado City, west of Colorado Springs. 

2. 15758, NW%, sec. 24, T. 9 S., R. 68 W., Perry Park. 

3. 15820, SW1,4 sec. 9, T. 22 S., R. 501 W. 

4. 15823, SE%, sec. 35, T. 21 S., R. 50 W. 

5. 16066, SW%, sec. 32, T. 21 S., R. 48 W. 

6. 16070, NE%, sec. 6, T. 22 S., R. 44 W. 

7. 16084, NE%, sec. 26, T. _ 21 S., R. 49 W. 

8. 15822, NE%, sec. 16, T. 22 S., R. 50 W. 

9. 16067, SE%, sec. 27, T. 21 S., R. 49 W. 

10. 16074, northeast corner sec. 34, T. 21 S., R. 49 W. 

Bass 56 reports from the lower 18 feet of the Fairport 

shale member of Hamilton County, Kans., the following species: Globigerina bulloides D'Orbigny, Iiwceramus fragilis Hall and Meek, Inoceramus labiatus 

Schlotheim (broad variety), Ostrea cf. 0. congesta 

Conrad, Baculites gracilis Shumard, Prionotropis woolgari (Mantell), I chthyodectes? sp. From the Blue Hill 

shale member Bass 57 reports Inoceramus sp. ( fragments) and Prionocyclus wyomingensis Meek. From 

the top of the Cod ell Bass 58 reports Inoceramus fragilis Hall and Meek, Ostrea congesta Conrad (float n, 

Prionocyclus wyomingensis Meek, Ptychodus sp., 

Lamna? sp., Ooraw.fl sp., coprolites, and phosphate 

nodules. 

NIOBRARA FORMATION 

The Niobrara formation is the uppermost formation 

of the Colorado group. It is distinctly separated from 

the underlying Carlile shale but less readily separable 

from the overlying Pierre -shale, the ·lowest formation 

of the lVIontana group. It includes about 700 feet of 

beds, chiefly chalk and chalky shale but with a well-

·marked, persistent limestone member, from 50 to 65 

feet thick, at the base. This limestone is continuous in 

outcrop with the limestone member of the Niobrara 

56 Bass, N. W., op. cit., p. 66. 

117 Ideni, pp. 64-65. 

" Idem, p. 65. -
/ 

S. GEOLOGICAL SURVEY 

A. A GROUP OF "TEPEE BUTTES." 

Small conical hills in the Pierre shale formed by the greater resistance to weathering of large n;1asses of limestone. Looking north from the center of sec. 3, T. 17 S., R. 65 W. 

C. TYPICAL OUTCROP OF THE LOWER PART OF THE SMOKY HILL MARL MEMBER OF 

THE NIOBRARA FORMATION. 

Looking northwest from the sec. 16, T. 21 S., R. 49 W. 

PRO

B. DETAILED VIEW OF WEATHERED TOP OR CORE OF 

SEC. 35, T. 12 S., R. 49 

The rock is an impure limestone in which Lucina occide

D. CONTACT BETWEEN THE HAYS LIMESTONE MEM

TION AND THE CODELL SANDSTONE MEMBER OF T

SEC. 21, T. 21 S., R. 49 W. 

The hammer rests on a hard bed of calcareous sandstone within t

of the Hays limestone. 

STRATIGRAPHY OF UPPER CRETACEOUS ROCKS IN EASTERN COLORADO 221 

formation in western Kansas that has long been called 

"Fort Hays limestone" and is eq~ivalent to it in lithology, thickness, and age, so far as known. The writers 

propose that the limestone at the base of the Niobrara 

within the area which they have mapped be called the 

"Hays 59 · limestone member" and that the overlying 

portion of the Niobrara be called the "Smoky Hill marl 

member", to correspond with the usage of "Smoky Hill" 

for the upper chalk member of the Niobrara formation 

in the adjoining area of western Kansas. 

The Niobrara formation of southeastern Colorado 

has heretofore been divided into a lower member, the 

Timpas limestone, and an upper member, the Apishapa 

shale. These previously defined units differ somewhat 

from those recognized in western Kansas and from 

those recognized by the writers north of the Arkansas 

River i~ eastern Colorado. 

According to Stose;60 the Tim pas limestone was named 

by Gilbert from Timpas Creek, which flows through 

the southeast corner of the Apishapa quadrangle and 

thence into the Arkansas River. The description of 

the Tim pas limestone by Gilbert 61 is quoted below, in 

part: 

The general thickness of the Timpas is 175 feet; and it may 

be characterized as a series of limestones and calcareous shales 

with prevailing pale colors. 

At the base is a limestone series about 50 feet thick. The 

individual beds range in thickness from a few inches to 3 

feet, the average being about 1 foot. They are separated by 

layers of gray shale, usually 1 or 2 inches thick. The limestone 

has a light-gray color, which becomes creamy white on weathered surfaces. It is compact and rather fine grained and where 

exposed t~ the weather breaks up into rough flakes, of which 

the longer dimensions are parallel to the bedding. This peculiarity ordinarily serves to distinguish it from the Greenhorn 

limestone, which cleaves into vertical plates. * * * In its 

lower layers are small nodules of iron sulphide, which are converted by the chemical reaction of the air to limonite. As the 

limestone is broken up and removed by the action of weather, 

the more resistant nodules are freed from their matrix so as 

to lie loose on the surface. They are of a dark-brown color 

and of oval or cylindrical form, with a diameter of about half 

an inch. Their surfaces are not even but are set with angular 

projections, the end of crystals. * * * 

The upper limit of the limestone is indefinite. It passes gradually into a light-gray limy shale, which contains occasional 

thin beds of limestone and has a total thickness of 100 or 125 

feet, terminating at top in one or two layers of chalky limestone containing several species of fossil shells and also the 

remains of fishes. 

The Hays ·limestone n1ember as recognized by the 

writers is probably closely equivalent to the "limestone 

69 The shorter name "Hays" has been adopted for this member with 

the approval of R. C. Moore, State geologist of Kansas. The name of 

the type locality has for some time been "Hays." 60 Stose, G. W., U. S. Geol. Survey Geol. Atlas, · Apishapa folio (no. 

186)' p. 6, 1912. 61 Gilbert, G. K., The underground water of the Arkansas Valley in 

eastern Colorado: U. S. Geol. Survey 17th Ann. Rept., pt. 2, pp. 

566- 567, 1896. 

77388-37--3 

series about 50 feet thick" at the base of the Timpas as 

defined in earlier reports. In the region mapped, and 

in son1e sections examined in adjoining areas, the limestone unit about 50 feet thick forms a natural, convenient, and practicable unit. It is, moreover, the unit 

readily recognizable in records of deep wells, both in 

this area and in northeastern Colorado. 62 

The Timpas was differentiated in the La Junta 

region, 63 but farther east the limestone bed at the top 

of the Timpas was not recognized with assurance nor 

mapped by the writers. This may be in part attributable to scarcity and discontinuity of exposures. Two 

limestone beds, each 1 foot or less in thickness and separated by 12 feet of cream-colored or tan chalk, are exposed in the eastern part of sec. 23, T. 23 S., R. 55 W., 

and may lie near the top of the Timpas formation as 

previously defined. In the eastern part of sec. 27, T. 

21 S., R. 53 W., along Adobe Creek, there is a bed of 

white limestone about 4 feet thick underlain by chalk 

which may also be near the same horizon. These limestone beds are included by the writers in the Smoky 

Hill marl. Even were exposures adequate, there . is 

some doubt that the Timpas limestone as previously 

defined i~ a stratigraphic unit of widespread usefulness 

within the area described by the writers. 

Inoceramus deformis, which is abundant in the Hays 

limestone member, does not occur above it, and immediately overlying beds contain large flat I nooeramus ( H aplosoapha) grandis. These fossils appear to 

have distinct ranges over most of the region of western 

Upper Cretaceous sedimentation, regardless of lithologic environment. There is thus some suggestion that 

the lithologic unit of the Hays limestone is also a faunal 

unit. The unit named "Timpas limestone" by Gilbert 

therefore includes in its uppe,r part beds that are both 

lithologically and faunally more closely allied to the 

upper part of the Niobrara. The names "Timpas" and 

"Apishapa" have, however, been applied to mappable 

units over a large area west and southwest of the area 

in which the writers have had opportunity to make 

detailed observations and should therefore be retained 

for areas in which the propriety of distinguishing the 

Hays limestone 1nember has not yet been made evident. 

HAYS LIMESTONE MEMBER · 

The tern1 "Fort Hays" (from the :formerfort of that 

name in Ellis County, Kans.) was first used by Mudge 64 

as a division name, defined thus: "The massive stratum 

of limestone above described, together with all the deposits above the sandstone of the Dakota, I shall call 

the Fort Hays division." This included all the strata 

62 Waldschmidt, W. A., op. cit., pp. 412-415. 63 Patton, H. B., op. cit., pp. 43-44. 64 Mudge, B. F., Notes on the Tertiary and Cretaceous periods of 

Kansas: U. S. Geol. and Geog. Survey Terr. 9th Ann. Rept., p. 289, ~7~ . 
222 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 19 3 6 

from the top of the Dakota to the base of the present 

Smoky Hill member. Williston 65 later restricted the 

name to include only the present Hays limestone 

member. 

The Hays limestone member includes beds of white · 

to cream-colored, chalky limestone 6 illches to 3 feet 

thick separated by beds of gray calcareous shale 1 to 6 

inches thick. The limestone makes up nearly .threefourths of the member. Near the base there are numerous small irregular or capsule-shaped nodules of pyrite 

.(or marcasite~) from one-fourth to three-fourths of an 

inch in longest dimension. The surface of these nodules 

is made up of an aggregate of interlocking cubical.crystals. In the lower foot -or two of the member there are 

small lenses of hard gray limestone which h~ve a petroliferous odor on fresh fracture and resemble the limestone bed that in places forms the top of the Codell 

sandstone member of the Carlile. 

The following section of the Hays limestone member 

was measured approximately midway east and west 

within the area covered by the 1nap: 

Section of Hays limestone member of the Niobrara forma-tion 

in sees. 1B and 21, T. 21 S., R. 49 W. 

Niobrara formation. 

Smoky Hill marl member : 

Shale, tan; weathers yellow. Ft. in. 

Limestone, white-------------------------- 4 

Shale, chalky, gray to tan; weathers tanyellow------------.-------.--------------- 5 

Hays limestone member : 

Concealed, limestone and shale _____________ 17 

Shale, chalky, light tan ___________________ _ 

Limestone, white-------------------------- 3 

Limestone and shale, interbedded, partly 

concealed------------------------------- 4 

Limestone, white; contains Inoceramus deformis and fucoids_______________________ 2 

Limestone, white, chalky, and gray shale ___ _ 

Limestone, white, chalky, irregular bedding_ 1 

Chalk, shaly, white to gray ____________ -____ _ 

Limestone, white--------------------------

Shale, gray to tan; contains many Inocera- mus deformis? __________________________ _ 

6 

3 

4 

8 

5 

10 

5 

Limestone, white, cbalky ------------------- 1 4 

Chalk, white ----------------------------~- 2 

Limestone, white; weathers into .small tabular pieces------------------------------- 2 6 

Chalk, shaly --- --------------------------- 1 

Limestone, white----- ------------------- -- 10 

Shale, tan to gray; contains Inoceramus sp_:_ 6 

Limestone, white; lower 2 feet massive______ 3 6 

Chalk, shaly, tan to gray___________________ 11/z 

Limestone, white___________________________ 1 2 

Chalk, tan ________ --- ----~---_:-----~-------- 1 

Limestone, white___________________________ 8 

Shale, chalky, tan__________________________ 5 

Shale, blue________________________________ 3 

Limestone, white----------------~---------- 1 10 

65 Will~sto:q., S. W., Th~ Niobrara Cretaceous of western Kansas: 

Kansas Acad. Sci. Trans., vol. 13, pp. 108_:_109, 1893. 

Section of Hays limestone member of the Niobrara formati.on 

in sees. 16 and 21, T. 21 S., R. 49 W.-Continued 

Niobrara formation-Continued. 

Smoky Hill marl member-Continued. 

Chalk, tan, and limestone __________________ _ 

Limestone, white-------------------'--------

Shale, greenish gray---------------,---------

Limestone, white---------------------------

Chalk, tan ________________________________ _ 

Limestone, white __________________________ _ 

Shale, blue gray, calcareous _______________ _ 

Limestone, white; weathers into tabular 

pieces--------------------~--------~-----

Shale, gray, chalky---------------,----------

Limestone, ·white; contains abundant Inoceramus deformis----------------------------

Chalk, tan: and gray calcareous shale------ ~ Limestone, white __________________________ _ 

Chalk, tan ________________________________ _ 

Limestone, white __________________________ _ 

Shale, gray, calcareous ____________________ _ 

Limestone,- white---------------------------

Chalk, tan to gray--------------------------

Limestone, white; irregular bedding; weathers 

into tabular pieces ______________________ _ 

Shale, tan, chalky----------------------.,---- Limestone, white __________________________ _ 

Chalk, light gray, shaly ---------------------

Limestone, white, irregular~---------------­

Chalk, light gray, shaly --------------------- Limestone, white ____________________ _:_ _____ _ 

Limestone, white, and tan chalk ____________ _ 

Limestone, white __________________________ _ 

Chalk, tan, shaly -- ------------------------- Limestone, white __________________________ _ 

Shale, tan, chalky--------------------------

Limestone, white, containing capsule-shaped 

pyrite nodules ___________________________ _ 

Carlile shale: 

Codell sandstone member : 

Sandstone and shale, gray, cemented with 

Ft. fn. 

11/z 

1 5 

6 

8 

1 

2 

6 

1 1 

2 

1 3 

7 

7 

1 

3 

6 

10 

2 

1 

6 

9 

2 

2 

31/z 

1 

8 

1 6 

2 

1 3 

3 

3 

lime; contains lenses of hard limestone____ · 0-6 

Sandstone, gray to brown, hard ; contains fish 

scales, fragments of fossils, and fucoids. 

From 0 tO------------------------------- 1 6 

Sandstone; gray, fine-grained. 

Total measured ______________________ 71 8 

Thickness of Hays limestone __________ 64 4 

The thickness of the Hays in the above section is 

about 65 feet. In Hamilton County, Kans.,66 the thickness of the mmnber is 61 feet. In the Nepesta quadr-angle 67 and adjoining areas the thickness of the limestone unit at the base of the Timpas is about 50 feet. 

The Hays limestone ·· is n1uch more resistant to 

\veathering than the beds above or below and consequently generally forms an escarpment or cliff. It is 

exposed almost continuously fron1 La Junta to a point 

north of 1\'lcClave. Thence eastward, however, it is 

poorly exposed. East of Lamar the base of the lime-

. eo Bass, N. W., op. cit., p. 62. 

67 Fisher, C. A., op. cit., p. 2. 
STRATIGRAPHY OF UPPER CRETACEOUS ROCKS IN EASTERN COLORADO 223 

stone swings southward across the Arkansas River Section of Niobrara formation on Gold Creek, west of old 

hut swings back before the Kansas line is reached. Pinafore post office, northwest of Vermejo Park on the road 

to Costilla, Colfam County, N. Mem. 

SMOKY HILL MARL MEMBER 

Although the entire thickness of the Smoky Hill 

marl member is present, little is known of it in detail 

because of poor exposures (pl. 65, 0). It lies upon the 

white chalky limestone beds of the Hays member, from -

vvhich it is easily distinguishable because it is softer 

and has a characteristic yellowish-orange color. The 

Sn10ky Hill contains beds of white limestone, but they 

are in most places only a few inches thick and are 

separated by 1nuch greater thicknesses of yellowish 

chalk. Several thin bentonite beds have been noted 

within the Sn1oky Hill, as well as beds of dark-tan 

and bluish shale. Much of the Smoky. Hill has a tan 

to yellow color when fresh, and practically all of it 

has some shade of yellowish orange on weathered exposures. Another distinguishing feature is the occurrence of small white calcareous flecks throughout the 

chalk, which give it a mottled "salty" appearance. The 

total thickness of the Sn1oky Hill is not known precisely, but fron1 ·well logs it is believed to be between 

600 and 700 feet. "\Vithin probably the upper 100 feet 

of this member are chalk beds that are somewhat 

harder and purer than the beds below. On weathered 

outcrops the bedding planes have opened, and these 

horizontal or tabular spaces are loosely filled with 

needlelike interstitial calcite in which the larger dimension of the crystals is perpendicular to the bedding. As 

a whole, the Smoky Hill is well stratified and thinbedded.. It is practically all calcareous, but the larger 

part of it may be properly tern1ed marl rather than 

chalk. 

Inoceramus (Haploscapha) grandis is the n1ost diagnostic fossil of the Smoky Hill men1ber. Complete 

well-preserved specimens are seldon1 found, but in 

places large fragments covered with oyster shells are 

numerous. Fish scales are abundant in some exposures 

of the upper part of the member. 

NIOBRARA FORMATION IN SOUTHERN FOOTHILL REGION 

The Timpas limestone has been differentiated as far 

south as the area of the Spanish Peaks folio, 68 in which 

it is described as 200 feet thick, including a lower portion, 45 to 50 feet thick, consisting chiefly of limestone. Just a short distance to the south, along the 

east flank of the Sangre de -Cristo Range in extreme 

northern New Mexico, however, lin1estone forms a much 

smaller proportion of the Niobrara formatioi1, a~ 

shown in the following section ; 

68 Hills, R. C., U. S. Geol. Survey Geol. Atlas, Spanish Peaks folio 

(no. 71), p. 1, 1901. 

Pierre shale. 

Niobrara formation : 

Shale, hard, gray, calcareous; thickness ( esti- Ft. in. 

mated)-----------------------------:-------- 250 

Shale, hard, gray, calcareous, with a zone of thin 

lenticular beds of hard gray calcareous sandstone near the top ; thickness (estimated)____ 500 

Limestone, gray, in beds 4 inches to 1 foot 4 

inches thick, with intervening beds of gray calcareous shale~------------------------------ 8 

Shale, gray, calcareous _________ _: __ -___________ _ 4 

Bentonite-----~~------------------------------

Shale, gray, calcareous ________________________ _ 

Bentonite ____________________________________ _ 

Shale, gray __________________________________ _ 

Bentonite ____________________________________ _ 

Shale, gray, calc3:reous, with thin lenses and 

beds of hard gray marL _____ :_ ______________ _ 2 

Rusty streak. 

Shale, gray, calcareous _______________________ _ 1 

Bentonite ____________________________________ _ 

Shale, gray, calcareous, some thin shaly limestone beds---------------------------------- 2 

Bentonite? __________________________ ----------

Shale, gray, calcareous _______________ _: _______ _ 1 

Bentonite ____________________________________ _ 

1 

10 

5 

7 

4 

6 

3 

2 

~ 

2 

4. 

/ Thickness of Niobrara formation, about__ · 770 

Carlile shale: Gray shale with septarian concretions and thin 

beds of hard sandy limestone. 

This section is of interest in . representing the character of the Niobrara formation at a place -probably near 

the southwesterly limit at which a limestone unit equivalent to the Hays limestone of the Arkansas Valley is 

present in the .Cretaceous section. 

The rather conspicuous bentonite zone in the basal 

part of the Niobrara in the yreceding section has no£ 

been described in previously published reports and was 

not observed by the writers along the Arkansas River. 

There is a suggestion, however, that it extends some 

distance northward along the east flank of the Sangre 

de Cristo Range into Coloraao. Bentonite beds, probably in the basal p~.rt of the Niobrara, were observed ~t 

a locality about 6 1lliles south of Stonewall, in western 

Las Animas County, Colo. (west of Trinidad). Still 

farther north, on the north side of the Huerfano River 

just northeast of the bridge at Badito, there is a soft 

concealed interval-of 10 feet above the sand at the top 

of the Carlile shale. At the top of the concealed interval are soft hedged marls, and at the base of it there 

may be some bentonite. The softer beds making the 

interval of concealment were included by the writers in 

the Niobrara formation. 
224 SHORTER ·coNTRIBUTIONS TO GENERAL GEOLOGY, 19 3 6 

FAUNA 

The following fossils were collected by the . writers 

from the Niobrara formation: 

Smoky Hill marl member : Locality 

Inocerar.nus SP----------------------~------------ 2,9,10 

Inocerar.nus deforr.nis lfeek?_______________________ 8 

Inocerar.nus aff. I. stanton;£ Sokolow?_______________ 8 

Ostrea congesta Conrad ________________________ 1,2,9,10 

Baculites codyensis Reeside__________________ ______ 2 

Fish remains, undetermined _______________________ 10, 11 

Hays limestone member: 

Globigerina SP------------------------------------ 5 

Inocerar.nus 'deforr.nis Meek------------------------ 3, 4, 7 

Inocerar.nus aff. I. stantoni Sokolow---------------- 7 

Ostrea congesta Conrad___________________________ 5 

Os~rea SP--------------------------------.-------- 6, 7, 8 

Scaphites ventr"icosus Meek and Hayden____________ 3 

1. 16071, NE:l4 sec. 6, T. 22 S., R. 44 W. 

2 .. 16080, NW:l4 sec. 19, T. 20 S., R. 43 W. 

3. 15745, Mount Morrison-Bear Creek locality. (Seep. 210.) 

4. 15747, Colorado City, west of Colorado Springs. 

5. 15751, Cuesta ridge on east flank of small anticline on Arkansas River about 7 miles west of Pueblo. 

6. 15811, SE:i4 sec. 24, T. 22 S., R. 53 W. 

7. 16073, NW:l4 sec. 32, T. 21 S., R. 44 W. 

8. 16075, SW:l4 sec. 27, T. 20 S., R. 49 W. 

9. 16079, NW:l4 sec. 17, T. 19 S., R. 44 W. 

10. 16081, SE:l4 SE:l4 sec. 26, T. 20 S., R. 43. W. 

11. 16082, NW:l4 SW14 sec. 34, T. 17 S., R. 44 W. 

· The late Prof. I. A. Keyte collected from beds at a 

horizon near the top of the Apishapa shale (top of 

Smoky Hill member of this paper), southwest of the 

area treated here, the following forms : Pelecypods, 

Inoceramus sp., Turnus n. sp.; gastropod, Anchura? 

sp.; cephalopods, Eutrephoceras sp., B aculites as per 

Morton, Baculites codyensis Reeside, Scaphites vermiformis Meek and Hayden, Scaphite8 ventricosus Meek 

and Hayden with several varieties~ Placenticeras sp., 

Tewanites cf. T. pseudotexanus ( Grossouvre). G. K. 

Gilbert collected from the upper part of the Niobrara 

northwest of Pueblo a very large specimen of I noceramus undulatoplicatus Roemer. 

PIERRE SHALE 

The lower part of the Pierre shale is present in the 

area shown on the map (pl. 64). It is poorly exposed, 

but lithologic subdivisions can be recognized and cari 

be traced through the scattered outcrops available . for 

examination. Much of the upper part of the formation lies outside of the area shown on plate 64~ and the 

uppermost beds are not treated in detail .in this paper, 

.though certain data on these beds that have . been 

collected are given on pages 230-231. 

LOWER PART 

Several divisions have been recognized in the lower 

part of the Pierre shale of eastern Colorado and in 

that of western Kansas by previous students of these 

areas. It does not yet appear possible, however, to 

establish definite correlations between the series ·· of 

units set up in the several areas. As set forth below, 

the writers propose to apply in the Arkansas Valley 

oply one formal member name, the "Sharon Springs 

shale member", using for the present only informal 

names for other divisions. 

Before describing the exposures of the lower part of 

the Pierre in the mapped area, however, it seen1s best to 

describe the nature of this part of the Pierre shale 

farther west, where exposures are more complete. 

The lower part of the Pierr~ shale is well exposed 

along the south side of Little Fountain Creek in the 

northern part of sec. 18, T. 16 S., R. 66 W., about 6 

miles somewhat south of west from the town of Fountain, in the Colorado Springs quadrangle. The Pierre 

and underlying Niobrara dip generally eastward and 

northeastward ·at angles of 10° to 15°, the dip diminish.-

ing toward the east. The basal portion of the Pierre 

includes an estimated thickness of 550 feet of thinbedded dark-gray shale. There are a few thin beds of 

hard yellowish-gray sandy limestone and a few beds 

a small fraction of an inch thick of yellowish earthy 

sand, also a few beds of bentonite. The only fossil remains observed were fish scales. At the top of this 

lithologic unit, near the center of the north line of sec. 

18, there is a zone of large gray septarian concretions, 

seamed with brownish crystalline calcite. Immediately 

above this zone lie brownish-gray and dark-gray shales, 

with numerous reddish-brown calcareous beds and 

small flattish red-brown concretions. This lithology 

continues upward for an estimated thickness of 450 

feet, and at the top the shales contain numerous fossils, 

chiefly Inoceramus sagensis Owen and Baculites ovatus 

Say. 

The general subdivision of the lower part of the 

Pierre described above was also recognized by Gilbert 69 

in the vicinity of Pueblo. He says: 

The Barren zone, so called on account of the rarity of its fossil 

remains, lies at the bottom of the series and is 400 to 500 feet 

thick. It is of bluish-gray color and in its lower part resembles 

the Niobrara shale in the tendency to divide into papery layers, 

rough from the crystallization of selenite. The Rusty zone, 600 

feet thick, is aiso bluish gray in color but is comparatively free 

from gypsum. It contains many concretions composed of lime 

carbonate :and iron carbonate, and these are. of oval form, measuring, · usually, from 1 foot to 2 feet across. Their material is 

originally dark gray but under the action of the weather turns 

a rusty brown, and the soil derived from the formation is usually 

so strewn with their angular fragments as to appear reddish 

brown. The Baculite zone, 100 to 200 feet thick, is pale gray 

and is so called from the abundance of a fossil shell of that name;· 

The "Barren zone" and "Rusty zone" of the Pierre 

are also recognized and described by Lavington,70 who 

69 Gilbert, G. K., U. S. Geol. Survey Geol. Atlas, Pueblo folio (no. 

36)' p. 3, 1897. 

'l'o Lavington, C. S., Montana group in eastern Colorado: Am. Assoc~ 

Petroleum Geologists Bull., vol. 17, no. 4, pp. 3!:18-400, 1933. 
STRATIGRAPHY OF UPPER CRETACEOUS ROCKS IN EASTERN COLORADO 225 

states that they are present in the Canon City-Florence 

district. Lavington 71 believes that in northeastern Colorado the Baculite zone recognized by Gilbert is not 

persistent over widespread areas. 

In the Nepesta quadrangle, which lies to the east of 

the Pueblo quadrangle, Fisher 72 recognized in the 

Pierre a basal black shaly "barren zone", 400 to 500 feet 

thick, succeeded by 500 feet of dark-gray shale with 

numerous rusty concretions of iron and lime carbonate, 

and this in turn by 100 to 200 feet of somewhat lighter 

gray shale with numerous baculites. 

Eastward to the Kansas line in the area shown on 

the map (pl. 64) small isolated outcrops show that the 

divisions recognized above carry through eastward. 

Some 2.4 miles north of Olney Springs are outcrops of 

shale with rusty concretionary beds and gray septarian 

concretions, representing a zone 300 to 350 feet above 

the base of the Pierre shale. These outcrops are probably near the base of the "rusty zone'' and indicate a 

somewhat diminished thickness of the basal "barren 

zone", which is not exposed in this locality. Outcrops 

near the base of the Pierre in a large ditch in the southwest corner of sec. 29, T. 20 S., R. 56 W., northeast of 

Lake Henry, consist chiefly of thin-bedded gray and 

dark-gray shale that is neither sandy nor calcareous. 

One thin bed of white bentonitic clay and two beds of 

red clay less than 1 inch thick were observed, and also a 

few yellowish and slightly sandy beds. About 3 miles 

northeast of Lake Henry, in the bank of Pond Creek 

where it crosses the line between sees. 16 and 17, T. 20 S., 

R. 56 W., are outcrops of shale which are estimated to 

be not more than 300 feet above the base of the Pierre. 

The lower part of the exposure consists of gray and 

dark-gray bedded shale, slightly sandy toward the top. 

The upper part consists of gray somewhat sandy shale 

and gray shale with abundant yellow and brown resinous fragmentary remains of fishes. One reptilian rib, 

possibly that of a mosasaur, was observed. There are 

some sandy layers. At the base of the upper part is a 

layer of soft white bentonitic clay. In the upper part 

of the exposure are large dark-gray dense limestone 

concretions. This exposure apparently represents the 

top of the basal "barren zone" of the Pierre. Although 

it is not definitely known to be immediately overlain 

by beds in which the rusty-weathering carbonate concretions are abundant, the next overlying exposures 

exhibit the "rusty zone" lithology. 

The basal portion of the Pierre is exposed also west 

and northwest of Haswell. The beds are mostly dark 

nonsandy shales with numereous gypsum crystals, 

though there are a few thin purplish-brown concretionary beds and some bentonite ~ beds, of which one 

has a thickness of 3¥2 inches. In the NW1;4 sec. 16, 

n Lavington, C. S., op. cit., p. 403. 72. Fisher, C. A., op . . cit., p. 2. 

T. 18 S., R. 52 W., a zone of large gray dense septarian 

limestone concretions in gray shale is succeeded upward by shale in which the dark reddish-brown ''rusty 

zone" concretions are abundant. These exposures may 

represent the top of the basal ''barren zone" of the 

Pierre, which cannot much exceed 200 feet in thickness 

in this vicinity. 

In the area intervening between the exposures 

northeast of Lake Henry and the exposures west of 

Haswell no outcrops having the litholdgy of the basal 

Pierre were observed. In the NW1,4 sec. 14, T. 18 S., 

R. 54 W., there are exposures of shale with abundant 

rusty-brown concretions less than 2 miles west of 

topographically higher exposures of calcareous shale 

that apparently belongs to the Niobrara fonnation. It 

seems more likely that this occurrence is due to a somewhat steeper northwestward dip at this place than to 

absence of the "barren zone." 

In the western part of sec. 29, T. 15 S., R. 46 W., an 

exposure shows calcareous concretions with septaria of 

crystalline calcite embedded in gray to black nonsandy 

shale with much soft powdery gypsum. This exposure 

may also represent the top of the "barren zone" of the 

basal Pierre. 

Detailed studies in Wallace County, Kans., enabled 

Elias 73 to subdivide the lower part of the Pierre into 

several members, the lowest of which, the Sharon 

Springs member, conforms in lithology with the "barren 

zone" of the Pierre of eastern Colorado. The Sharon 

Springs member is 155feet thick. It is overlain by the 

beds called "Weskan member" by. Elias, which are succeeded by his Lake Creek member and that in turn by 

his Salt Grass member. These three members are characterized by abundant limonitic concretions, which have 

a rusty appearance. They have a combined thickness 

of 430 feet and appear to be equivalent to the "rusty 

zone" of the Pierre of eastern Colorado. 

The writers propose to extend the name "Sharon 

Springs member" into ~astern Colorado to include the 

basal black -shale member above described, which is 

equivalent to the "barren zone" previously recognized. 

They feel that the overlying "rusty zone" has not yet 

been sufficiently studied or its upper limit in Colorado 

determined with sufficient accuracy to warrant designation by a specific name. 

Although the Sharon Springs member as above defined appears to be a widespread and homogeneous unit 

of black clay shale which is present also in the northern 

foothill region and is recognized by drillers in northeastern Colorado,:4 scattered observations .indicate that 

the lowest part of the Pierre may be more variable in 

its lithologic features in the southern foothill region. 

73 Elias, M. K., The geology of Wallace County, Kans. : Kansas Geol. 

Survey Bull. 18, pp. 58-116, 1931. 

14 Lavington, C. S., op. cit., p. 399. 
226 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 19 3 6 

On the north side of Apache Creek, 1¥2 miles southwest of Hayden Butte, in the Walsenburg quadrangle, 

there are extensive exposures of an earthy sandstone 

about 60 feet thick. Near the middle is a zone of large 

limestone concretions. Below the sandstone dark shale 

with rusty concretionary beds a few inches thick is exposed for 50 feet, more or less, and above it lie black 

thin-bedded shales with sorrie rusty streaks. The exact stratigraphic position of the exposures was not ascertained, but they are clearly in the lower part of the 

Pierre, ·possibly about 500 feet above the base. I noceramus sagensis Owen and Baculites asper Morton 

were collected from concretions about 5 feet above the 

top of the sandstone. 

:On the north side of the Huerfano River 3 miles 

northeast of Badito there are exposures of an earthy 

gray and buff well-bedded sandstone, for the most part 

well indurated, with some brown concretionary beds. 

Overlying the sandstone is 5 feet of sandy shale with a 

concretionary zone at the top from which Inoceramus 

s(lgensis Owen, Baculites asper Morton~ and Scaphites 

nodosus Owen v.ar. were collected. This concretionary 

zone is overlain by black paper-bedded shales that contain a few rusty concretionary beds. Below the sandstone there is sandy shale with some rusty concretionary 

beds and a few yellow flattish concretions 1 foot thick 

and as much as 20 feet in· length. The interval from 

the sandstone described to the top of the Niobrara was 

not determined but is probably more .than 300 feet. 

The two exposures of sandstone described may be the 

Apache sandstone of Prommel. 76 

. Still farther south, at a locality 6 miles north of 

Stonewall, road cuts expose the lower part of the Pierre 

shale, which at this place dips vertically. .Although 

penetrated by sills of dark igneous rock and possibly 

s~mewhat squeezed and faulted, these exposures give a 

good idea of the lithology of the lower part of the 

Pierre. A carefully estimated section is as follows : 

Section of Pierre shale 6 miles north of Stonewall 

Pierre shale : Feet 

Shale, black----~------------~----------------------- 200 

Sandstone, fine-grained, earthy, lumpy-bedded, and 

sandy shale-----------------c---------------------- 20 

Shale, slightly sandy. In the upper part are two 

beds of. yellow-weathering c;:oncretionary· limestone 

and a few thin streaks of shaly limestone __________ 260 

Shale, light gray, lumpy-bedded, with some small rusty 

concretions --------------------------------------- 120 

Concealed------------------------------------------ · 40 

Shale, like that exposed next above _________________ 150 

Shale, black, thin-bedded. In the basal part are a very few thin sand streaks ________________________ 100 

Thickness exposed ---------------------------- 890 

Niobrara formation: Shale, calcareous, with a thin dense 

impure limestone bed in the upper part. 

75 Lavington, C. S., op. cit., p. 399. 

In the western part of the town of Pueblo, 0.6 mile 

north of the Arkansas River and 0.6 mile east of Dry 

Creek, outcrops of the basal part of the Pierre reveal 

a sandy lithology not observed in areas to the north or 

east. At this place the exposures display alternating 

beds of dark-gray shale and yellowish-weathering 

sandy shale, overlain by at least 10 feet of very fine 

grained yellow earthy sand, some beds of which are 

soft, though others are cemented by lime to a hard 

coherent rock. This sandy zone may be as much as 300 

feet stratigraphically above the highest exposures of 

Niobrara observed by the writers, but as it appears to 

lie near to or even below the Niobrara-Pierre contact 

as mapped by Gilbert, the sand presumably lies in the 

basal part of the Pierre. These beds contain fish scales 

and numerous macerated· plant remains, together with a 

few invertebrate fossils. (See collection 15753, p. 230.) 

UPPER :PART 

In the area north of the Arkansas River a wholly 

satisfactory lithologic or faunal subdivision of the 

Pierre above the "rusty zone" is difficult to make. In 

part this is due to the absence of readily distinguishable differences or reliable key beds in the thick mass of 

shaly rocks. In part also it is due to the wide expanse 

of exposure with low dip and broadly level topography, with a resulting lack of extensive vertical exposures. There· is also much concealment by younger 

unconformable Tertiary ;tnd later deposits. The differentiation of the Pierre is further complicated by the 

fact that the original thickness of the formation diminished by several thousand feet across the area . which is 

now eastern Colorado. 

Several previous writers have differentiated the 

"tepee zone" of the Pierre, distinguished by the presence of "tepee buttes"-small, sharply conical hills, 

formed by the superior resistance to weathering of 

large concretionary masses of limestone. (See pl. 65, 

.A, B.) As defined by Gilbert,76 the zone is 1,000 feet 

thick, overlying the "Baculite zone" and including the 

upper part of the Pierre as exposed i;n the Pueblo 

quadrangle. According to Fisher's description of the 

Pierre of the N epesta quadrangle, the zone is 500 feet 

thick, underlain as in the Pueblo area by about 1,200 

feet of shales but overlain by about 600 feet of lightgray sandy shales. 

Two zones of tepee. buttes were recognized near Fountain by Lavington.77 East o.f Hugo, in the southwestern part of T. 11 S.; R. 52 W., there are large concretionary masses much like tepee cores, but probably having less vertical tha·n horizontal extent. These occur 

76 Gilbert, G. K., U. S. Geol. Survey Geol. Atlas, Pueblo- folio (no. 

36)' p. 3, 1897. 

n Lavington, C. S., op. cit., p. 402. 
STRATIGRAPHY OF UPPER CRETACEOUS ROCKS- IN EASTERN COLORADO 227: 

several hundred feet above the main series of tepee seems probable to the writers that they are restricted 

buttes. to a certain zone whose limits differ somewhat from 

In the vicinity of Fountain, in the Colorado Springs place to place, that this zone diminishes southeastward 

quadrangle, the writers estimated that the "tepee zone" in thickness, and that the shales below it but above the 

was roughly 1,500 feet thick and the overlying portion "rusty zone" also diminish southeastward in thickness. 

of the Pierre shale was also 1,500 feet thick. As these - In form, the tepee buttes, as their name implies, are 

estimates agree moderately well with the thicknesses of low -conical hills rising above the general level of the 

1,275 feet for the "tepee zone" and 1,885 feet for the , surrounding country. At the top of each is an irreguoverlying Pierre shale measured by Lavington,78 the lar cap of light-gray or brown limestone, much £raewriters believe that their estimate of 2,000 feet of the tured and containing great numbers of fossil shells, · 

Pierre shale below the "tepee zone" west of Fountain among which Lucina occidentalis is everywhere· preand south of Little Fountain Creek may be correspond- dominant. The shells are more or less completely reingly reliable. The total thickness of the Pierre in the . crystallized to translucent or transparent calcite, norColorado· Springs region is therefore about 5,000 feet. · mally with a yellowish cast, and the containing rock is 

If these estimates are correct, the "tepee buttes" occur ·in places seamed with intersecting veinlets of similar 

considerably lower in the section in the Pueblo region, calcite. On some of the buttes the limestone rock rewhere they are found at horizons beginning 1,200 feet veals a poorly defined, irregular horizontal stratificaabove the base of the Pierre and only 200 feet above . tion. The slopes of most of the buttes expose the shale 

the top of the "rusty zone." in which the limestone masses are embedded, but almost 

As the total thickness of the Pierre is known to dimin- all of them are thickly strewn with disintegrated frag~ 

ish greatly southward from Colorado Springs/9 the . ments of the hard rockexposed at the top. It is obvious 

lower occurrence of "tepee buttes" in the Pueblo region that the topographic form of the buttes is due to the 

m·ay be due to thinning of the 1,000 feet of shaly beds greater resistance to erosion of the central capping mass 

below the "tepee zone" in the vicinity of Fountain to of limestone. As the result of the most critical study 

about 200 feet near Pueblo. In fact, Lavington 80 be- of the origin of the tepee buttes which has been niade, 

lieves that on the west side of Baculite Mesa, northeast Gilbert and Gulliver 81 concluded thlit the limestone 

of Pueblo, small conical buttes from the overlying masses had the general form of vertical cylindrical 

"tepee zone" actually range down into the "rusty zone." cores, and this conclusion has been followed by all -subThe "tepee zone" also apparently thins southward from sequent observers. Inasmuch as it seems to the writers 

Colorado Springs to Pueblo and eastward from Pueblo that the same topographic form might well be produced 

to about 500 feet in theN epesta region and in the region by an essentially equidimensional concretionary mass, 

north of Olney Springs, -Ordway, and Arlington. In it is unfortunate that exposures of the vertical di:rilenthis region also the interval between the base of the sion of the tepee cores are rare. The greatest height of 

"tepee zone" and the top of the "rusty zone" is appar- , a core actually observed by Gilbert was 18 feet, and. the 

ently less than 100 feet. The base of the zone in horizontal dimensions of this·core were not stated. In 

which "tepee buttes" occur is about 1,350 feet above only one tepee butte examined by the writers could it 

the base of the Pierre southwest of Boyero and about be definitely ascer-tained that the vertical dimensio~ 

1,100 feet above the base north of Kit Carson. Exclu- ; was greater than the horizontal. 

sive of the Sharon Springs n1ember and the overlying Tepee cores have, 'however, been reported to have 

"rusty zone" at these places the intervening part of the :vertical di~ensions of as much as 50 feet, 82 and the 

Pierre shales below the "tepee zone" thins eastward , shape of one core_ has been described as tapering downfrom perhaps 650 feet southwest of Boyero to 400 feet ward like an inverted cone. 

north of Kit Carson. It should be understood that . The tepee-core rock has been described as follows: 83 

the thicknesses given apove are estimates only. ; The tepee rock is essentially a calcium carbonate, the ratio 

Because the "tepee buttes" occur in widely separated -of calcium carbonate to magnesium carbonate being 18 to 1 in 

groups and because the concretions that form them are :the single sample analyzed. That sample contained also 12 perembedded in shale in which no distinguishable litho- cent of argillaceous material. E'or comparative purposes, anal1 · f 1 h - t b . . · yses were also made of, the enclosing shale and of one of the ogiC or a una zones ave ye een di.scovered, there IS ordinary. concretions of the shale, the determinations showing 

no real assurance that these concretiOns are actually that the tepee rock does not differ materially in composition 

confined to a stratigraphically definable zone in the ' from the concretions, and that the argillaceous material is 

Pierre shale. Nevertheless, from their distribution it practically identical with the shale. This permits us to regard 

81 Gilbert, G. K., and Gulliver, F. P.; Tepee buttes: Geol. Soc. America 18 Lavington, C. S., op. cit., fig. 1. Bull., vol. 6, pp. 333-342, 1895. -

79 Hills, R. C., U. S. Geol. Survey Geol. Atlas, Walsenburg folio (no. . s2 Fisher, C. A., U. S. Geol. Survey Geol. Atlas, Nepesta folio (no. 

68), p. 2, 1900. 68), p. 2, 1906. 80 Lavington, C. S., op. cit., pp. 399-400. 88 Gilbert, G. K., and Gulliver, F. P., op. cit., pp. 336-337. 
228 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 19 3 6 

the argillaceous material as included shale, and therefore an Brown, darkly translucent or black opaque organic 

impurity rather than an essential constituent of the tepee rock. matter of various types occurs in small and broken frag":' 

The rock has a coarse texture, breaks with rough fracture, ments throughout much of the rock. In some areas, 

and its general color is a light, warm gray. It is full of fossil 

shells, and the microscope shows that they are embedded in a notably in the matrix within one Luoina shell near the 

matrix which is composed of fragments of shell, water-worn hinge and within the outer calcite layer of another 

grains of calcite, Foraminifera, and clay. ·Cross sections of Luoina shell, in lines paralleling the shell banding, are 

L/ucina shells show that the original shell structure remains, minute nearly black grains, 15 to 50 microns across, 

although the lime of the shell has been recrystallized into cal- which from their crystal form were pyrite, but which 

cite. Inside of the shell wall there is a band of radiating crystals of calcite, showing well-marked spherulitic structure. The because of their slight translucency and reddish-brown 

calcareous ooze which must have at first occupied the central color in reflected light now appear to be of limonitic 

cavity of the shell has recrystallized into very pure calcite, composition. The writers' thanks are due to C. S. Ross, 

leaving the clay impurities at one side of the shell. This cen- ·of the Geological Survey, for confirmatory examination 

tral calcite crystal is the same individual which has replaced of these grains and some advisory co~ments on the 

the lime of the shell, for the two parts extinguish together, the 

cleavage cracks extend from the center through the outside, nature of the rock in general. 

and when the spherulitic band is faulted the clear calcite is The clastic content of the rock is small and variable, 

continuous through the cracks. Experiments showed the spher- some slides showing virtually none and others having 

ulitic layer to be slightly less soluble in dilute hydrochloric acid an appreciable amount of very angular grains of quartz, · than the clearer calcite. · 

In a few thin sections examined by the writers there 

is considerable variation in the nature of the rock. On 

· the whole, the proportion of shell material is m:uch 

less than half of the total bulk. In some of the Luoina 

shells there is a division of the shell into three zonesan outer band that is composed of relatively few calcite 

crystals, a wider central layer of fibrous calcite with 

flamboyant extinction, and an inner layer of variable 

thickness which consists of small calcite crystals interlocking in a granular mass that grades into the matrix 

filling the shell. This granular layer is not common, 

and where it is absent the fibrous layer grades into the 

matrix. The fibrous layer may also be absent from 

either one or both valves of the shell, but the outer 

layer of large calcite crystals retains a sharp boundary 

with the shell filling, although it may be partly or 

wholly replaced by chlorite. No central ealcite crystals 

were observed within the matrix that fills the shell~. 

The bulk of the rock is fine-grained, consisting of 

intimately intermixed clay and calcite. Although the 

distribution of these materials varies greatly, there is a 

marked tendency for the clay to occur in somewhr.,t 

darker, cloudier patches, in cross section having a circular, elliptical, or irregular shape. These clay patches 

r~nge from 0.1 to 1 millimeter in diameter in different 

slides examined but exhibit less size variation in individual slides. Although the appearance of some of 

them suggests a coprolitic origin, it seems probable that 

most_ of them may represent flocculated clay pellets. In 

some slides granular interlocking areas of calcite occur 

in a fine-grained clay-calcite matrix; darker patchm;, 

chiefly of clay, occur in the same type of matrix; and 

patches of clay occur in areas of more coarsely crystalline calcite. · Some of the clay patches are irregular and 

bounded by areas of calcite grains with crystal outlines. These irregular clay masses semn to be segregations · produced during recrystallization of the rock. 

feldspar, and accessory ferro magnesian minerals. The 

grains observed were as much as 0.2 millimeter in 

diameter. 

Foraminifera were observed in most of the slides but 

are not numerous. 

Gilbert 84 concluded that the most satisfactory explanation of the tepee cores was that each "was the site of 

a colony of Luoina and that the remains of each perishing generation furnished in some way conditions favorable to the life of the next", although he considered that 

knowledge of the tepees at that time was not sufficient 

to definitely establish this as the correct explanation. 

Some of the difficulties in accepting the theory of colonial origin, as above outlined, were pointed out by 

Gilbert. In the first place the predominant shell of 

the tepee cores, Luoina, is neither known to be a colonial 

species nor to be a species that would especially flourish 

on the presumably more stable foundatio:q afforded by 

the shells and broken shell fragments of preceding generations. Luoina occurs in some abundance in the adjoip.ing shales and is found elsewhere in sandy shales 

and sandstones. Some of the shells in the tepee cores 

are wholly embedded in the matrix and in general are 

no more commonly adjacent to or resting on other shells 

than would be expected from their relative abundance 

in the rock. Nor is it known that individuals of Luoina 

at any stage utilized or required an attachment. In 

the second place, the bulk of the material of the tepee 

cores is fine-grained calcite and clay, which gives no 

indication of being of organic origin, except for the 

possible coprolitic structures mentioned above. 

, On the other hand, the slight differences observed 

between the matrix within and outside the shells and 

other features of the rock suggest that it is an original 

sedimentary deposit rather than a concretion_ary aggregate, and the particular abundance of Luoina shells 

M Gilbert, G. K., and Gulliver, F. P., op. cit., p. 339. 
STRATIGRAPHY OF UPPER CRET.ACEOUS ROCKS IN EASTERN COLORADO 229 

indicates c~ntemporaneously favorable life conditions than their horizontal dimension, it seems that there 

of some sort for them. must have been a baJance of some sort betwe~n the rate 

It seems }?QSsible that such favorable conditions might of deposition of th~ surrounding sediments~ and the 

be provided" by submarine springs of low volume but rate of accumulation_of the tepee core rock, in 9rder that 

relatively high concentration in calcium carbonate. It the -required condit!f>ns for forming that r<? ck might 

has already' been pointed out by Gilbert 85 that springs persist in one locality through the long perio9. of time 

of sufficient'irolume to build a tufalike core would pro- that must have been required to build up thet_epee core 

duce a con~htric structure in the cores, which has not and deposit the sur!ounding shale. That t'here were 

been found: On the other hand, a spring or seep of some va-riations in conditions from t~me to time is seen 

low volume on the sea floor might simply provide an by the irregular nature of some exposed sid~. walls of 

abun_dance of mineral salts in solution, which would cores. In Gilbert's, words, they "exhibit shoulders, 

produce loc ~ily a favorable site for the growth of many shelves, and overhangs, besides being rugose in detail." 

kinds of organisms. A . feature of the distribution of In general, it may .. be concluded that such "Conditions 

the buttes, ~hich might be construed as favoring the could be maintained only in places where tlre rate Jt 

hypothesis bf submarine springs, is their tendency to shell and calcium ~arbonate accumulation could keep 

alinement irl_rows. The lines of buttes in various places pace with the rate of sedimentation: Where sediments 

trend in diy_erse directions, so that this tendency to accumulated more r~_pidly nearer the source 9;f supply, 

alinement ck>es not produce any discernible systematic such conQ.itions could not long be maintained. On the 

arrangement· of the tepees as a whole, but locally the other hand, the rate of accumulation of the sheUs would 

alinement i~ . pronounced and should be explained by also seem to be a variable one, depending on'' available 

any satisfat1tbry theory of their origin, as should also supplies of necessary materials for shell con~truction 

the tendenc:y' of the buttes to occur in groups or clusters. . The foregoing di~cu§sion of the origin of ~he tepee 

As an in~resting speculation, the writers advance cores is intended primarily to emphasize the point that 

the hypothesis that the predicated submarine springs the nature of the masses themselves indicates--that they 

arose from :t-he pressing out of connate water during represent a type of ·deposition which would ~ccur at a 

the compaction of the sediments deposited to the north certain time within a geographically limited "'belt, and 

in the more ·rapidly subsiding portion of the Denver that this belt of tolerance would be very · likely to 

Basin. The . "tepee zone" contains the same fauna migrate to and fro, J>wing to variations in th,e rate of 

in general a~ the Hygiene sandstone member and over- supply of the sandy sediment that was being deposited 

lying sandstone members in the Pierre shale of the farther north and to-variations in the rate of si!bsidence . 

northern fciothills, where the total thickness of the of the basin. If so; the shale that containsJhe tepee 

Pierre shale is much greater. These sandstones alter- cores probably has ___ ~n intertonguing re~at~on __ with the 

n,ate with i~tervening shalier zones and diminish in enclo!:)ing shales that are barren of, the tepee IB.asses. 

thickness southward and southeastward . . As they were The part of the Pierre shale above the "tepee zone" 

deposited in the m·ore rapidly subsiding portion of the is composed of sandy shale and soft sandstone, particu~ 

basin, the tapering margins of the sandy wedges would larly in the upper part. It is lithologically a :t:ransition 

gradually acquire a gentl~ upward slope to the south- unit from the dominantly fine sedimentary beds of the 

east, outwatd and upward from the basin. It seems Pierre shale to the s~ndstone of the Fox Hills; As will 

possible that with the compaction of the sediments con- be seen from the fa\lnallists below, it is likewise in its 

nate water -o·f high mineral content would be squeezed upper part a transition zone from the faunal assem-

. out of muds:··and sa.ndy silts into overlying ~ongues of blage characteristic of the Pierre , shale to th~t characsand that might then ·serve as channel courses for the teristic of the Fox Hills sandstone. Neither top nor 

movement 0_f_ water upward and south ward·, there to base of this transition zone is sharply defined~ but it is 

escape upw~rd ~hrough the soft sediments of the sea certainly some hundreds of feet thick and app~ars to be 

floor along local lines of weakness. H. F. Davies sa characterized faufut-ily by Inoceramus fibros"its (Meek 

has suggeste~ a more direct relationship of the tepee and Hayden), B aculites grand is Hall and Meek, and 

buttes to th~._Hygiene and other sandstones, supposing several species of J}_iscoscaphites. It is notabie that il} 

that they may represent offshore deposition of the col- this region in the upper part of the transition .. zone and 

loidal silica :and calcium carbonate left in solution at in the base of the 9vedying_Fox Hills sandstone an ash sociation of such forms as I nocera:mus sagensis Owen t e outer ma!giiis of deposition of the sandy materials. and B aculites gran4is Hall and Meek with ·the Disco- vVhatever-the actual mode of origin of the tepee scaphites and species of Sphenodiscus is not uncommon. 

cores, if their vertical dimension is materially greater · In other regions where Pierre and Fox Hills ~re recog-

• Gilbert, G. J{., and Gulliver, F. P., op. cit., p. 339. 111 Lavington, C. S., op. cit., p. 402. 

nized this association is so rare as to be virtually nonexistent. 
230 SHORTER CONTRIBUTIONS TO GENERAL GEOLOGY, 1936 

FAUNA 

The :: :fossils collected :from the Pierre shale by the 

writers· ·are listed below. The· first list contains :fossils 

:from the beds between· the transition ~one and the ba,s~ 

of the '"tepee 75one", with the exception o:f collectioRs 

15752;15753, .15757, 15864; and 159'62, which came :from 

.the')lowe'r part :of the :formation: The sec:ond list in·-

chides :fds~ils :fro~ the transition zone in the uppermost 

pa.rt o:f th~ Pierre. . ; 

·:;· 

'Fos'sils from the Pierre shale below the tt·ansition zone 

Localit y 

Oli,ona sp:, borings---- -' --------- :.: ----~--~-- ---~----- .:. 3i 

I nocerartiiwr baraQi;fii. ~orton __ :,.. _'""'-'-'-------- -- _:_ ______ . 3, 2!, 24 

Inoceramus sagensis Qwen -~..,.---- --~---- '.c -------------- 5, 61 

' . . '.7, 8, 9, 11,12113,15, 16, 18, 22, 26,31 

Inoceramus SP--------- -----~-----~------ 14, 20, 28, 29, 30, 31 

Ostr ··cr. · co ~ Co~ad--~--------------------- 24, 28 

Anomia tsp, probably ·new ___ · __ :__ _____ _: ..:. __ ---------- -- -- 11 

Lucina occiden~aus Morton ___ .:.:._..L__ 9, 10, 15,.17, 23, 25, 26, 28,30 

Luc~n(J ;; ubcrassa Meek and Hayden...------------~------ . 25 

Luc~n~ ~P,. ;- -..,. ;- --- --:- ;- -- ---------.:.. __ _: ____ "'"----------- -19, 31 

M actra gracilis Meek and Hayden _____________________ _; 4, 30 

Maotra ·' ca nonen~ s Meek __ ,. _:_ ___ :.._ __ _-____ ..: ____ _:_: _______ 1, 2, 4 

Deidalium gracile :· JtaU ana Meek_~ ______ :_ ______________ 11,30 

Lunatia ·.dakotenS"i's ·Henderson __ .:_ _ _:. ___ :...'..:.:.. ..: ::. _~..:-_.:..____ 30 

Aporrhai~ , sp_ ..: ~..:!... ____ ..;. ___ ..:...:. ___ ._: _________ _,_ ____ .,._~ __ _:__ 25 

~:~~:~~ri;~=~ ~~~ ~~ ~~~~ ~~:~~ ~~~~ ~~~~~~~~==- ~~. ~ Bac~iite$ comp~~ss us Say_~~ -- ~------ .: -----------,------ 9, S1 

Baculites --·ovatu:s ·s ay _____ .2~ -- ---- .:_ _: __ _:~ ------· 2, 7, 25, 30 

Baaulites·ovattis Say var. ha'resi Reeside ____ _:___________ 5, 26 

. Bacu~it ~ SJ>--- -; -~ -.::.~--..,--------------- ...: ___ 11, 12, 16, '2:7, 28, 29 

Exitelqc r.a ? s.P------:~--;~L-"" ::. -:- ..: --- -~-------------- "' -- · . -25 

Did1f."!".OPfJr.a,s cf., J!:; hfJecheri .Hyatt_____________________ 26 

Par.apachudiscus complexus (Meek)-----------~-------- 29 Acanthoscaphit ' ~odostls (Owen)' ty-'picar form- ------- ·31 

AcanthoslYaphites 'nodosus (Owen) var_.::. _.:.. __ .:_ __ .;.. 1, 9, 10, 20;· 28 

Acanihoscaphitffs' quadrangularis (Meek)':.._:.._ .... __ ,_ ____ ;__~ -24,2:7 

Acantl!-qscf?rphit(}S; sp,.,.;- --;:.. "'-~;- .,. ,....:. ________________ ,__,.. __ 15,-18, 22 

Placenticeras meelJ;.i Boehm.,...,:..·-'------------------------ 11 

nviJsqao~? (Jai~tuiu_s cock~r~iL_~"" ---- ~-~-~--~-------- · ~ 

1. 15732;' Leyd~n GUlch·; Iidrtii 'pf'Golde'n, 'about 5,000 feet above 

·; tlie base ~:( the :Pierre. ·; ·'· · · 

2 . .15733, Leyden Gulch, nearly ·.the same as 15732. 

3. '15734., rLeyden Gulch, ne_al'lY tbe .same ·as 15732. 

4. 1573q,, Leyden GulcJ;l. n~arl;v the same as 15732. 

5. 15752, oppo it~ Piiion station~ 6.2 miles north of J;!Jden on 

· , :Pueblo-C~lorado Springs highway. 

6. 15753'; :west 'of Pueblo; north o{ Arkansas River, east of 

·nry Gree~ ·· valley. . · 

7. 15757; ·nortnea,st ··corner sec. · ;18, T. 16 S.,• R. ~6 W., south of 

, .Little Fountain Creek, southwest of. Colorado Springs. 

8. 1'5759; SE~ sec: 1~, ir: 15 S., R . . 65 W., at bridge on aban~ 

· doh~d railroad grade. · · · · · · · 

9. !575o;·near center of ·sec. 3, T. 17 S., R; 65 w., 1 mile south~ 

' east of Little Buttes.* 87 ' 

10. 15809., NW-1,4 s_ec.19; T.·15 S., R. .57 W. 

11. 1.5819, sees . .14 and 23, T. 17 S., R. 55 W. 

12. 15812, NE14 sec. 27, T. 15 S., R. 55W. 

13. l584l, along h'ighway, sec. 3, T. 11 S., ~· 54 W. 

s1 Collection~ made from the core rock of tepee buttes are indicated ~¥ 

asterisks. 

Fossils from the Pierre shale below the transition zone~Conw. 

oJ ~- ' •• -~- " -: 

14. 15843, SWl4 sec. 36, T. 13 S., R. 56 W. ·' • ''f( 

15. 15847, NE14 sec. 30, T. 13 S., R. 56 W. 

16. 15854, NW~ sec. 26; T : 14 -S., R. 55 W. 

17. 15855, SW% sec. 14,· T. 14 s.,:R. 57 w. 

18. 15858, NE~ sec. 36, T. 10 S., R. 53 W· 

19. 15859, NE14 sec .. 34, T. 10 S., R. 52 W· . ; :; 

20. 15860, SEtt4 . sec. 3Q, T. 10 S., R. 5l"W . 

21. 15861, NE14 sec. 26, T. 8 s., R. 50·w . . 

22. 15·862, SE% ·sec. 35, T. 9 S., R. 51 ·w. :. :<."'~·. 

23. 15863, SE%: sec. 28, T. 11 S., R~ 52 W. . :· ~· 

24. 158M, NW* sec.: 22, T. 13 S., R. 51 W. ,c 

25. 15755, 3.1 miles north of Belle P~aine, which ~s 217 J.9.i1~~ e~:J.~tt: . 

of Fo~ntain Gre.ek at Pueblo. . . ) ~~(- ~)' 

26. 15756, same iocality ·a:s 15755, 40 feet higher~ . . ~· .. :, . 

2:7. 15808, sec. 1; T. 21 S., R. 59 W., 5.3 miies noi.-tti o( OI~ey Springs.* · , '· ··' ··: ··· : ..... ~.·· · .< 

28. 15813,2.6 miles south o~ Karval. • ·,, · ·: · ,J 

29. 15962, NEtt4 sec. 34, T. 14 S., R. 67 ,W,., 500, -.- ~~e~ ~b_<;>;v~ ~fil~:: '· 

of Pierre. , 1 . ., ··' 

30. 15963, SWl4 sec. 20, T. 14 S.,' R. 66 W., bric~ pit SQUth~~st of Colorado Springs. · · · · ·" ·· · ; ,- · \ 1 ,·" •· 

31. 16072, NW%NE% s'ec:·1, T. 13 S., R: 47 W.* ' . ,; :·r··>':1 .. , 

Fossils troni the "transition ~on~" o{ the Pi rr~ .... ·, .. : I'<: 

E::E, ::~=====~=== =====~==~======= ==~=~====;== ;f_~~-; ,: Solemya biliaJ White_..:.::.. __________ _:.::__~_ . ..:.:..·..:.:::..=:..:_..:.:.._.::: c. __ :..: ~.:_ ' '3 · 

N ucula planimarginata l\Ieek and ~ayden.:. .:: __ _:_::__:_ __ ~ ·3;· ·4; 8; J 3 

Nucula larimerensis Reeside---------~----~ ------ :--: :-'- :... , ~7~;}8 

Nucula SP----- ---- ---------------~.:.---~--- 6, 20, 22?, 26, 2.T :· .. Yoldia scitula Meek and Hayden ------------ ----- ----: . ; ~$ Yoldia evansi Meekaild Hayden_~ ____ :__.:_ __ .:_ _ 3, 4, 5, 6,_15,-19, '28 . 

Yoldia sp ______ __: ________ '-~------------~ · _________ .:..:.· ___ _:' · · ~8Y·) :. 

Perissonota? sp __________ :._ _:. __ !.. _..:. ___________ -__ ~ ____ • ___ .:_ ·"' • •; :4· 

Inocera;mus sagensis Owen..,. _ _:_ _________________ 20, 2~; .28,:31; i!_6 

Inoceran;,us ~ltus -¥eek L--- -- ,. ---:-----------:-:--'""- :_ -.:. "' . , 39 

Inoceramus fibra,sus (Meek · and Hayden)--:-:----:---: 41 6, ~, 9. . 

· · · · · · 10, 11; 12·;16, 17, 18, 22;·:25; ao, 31.· ,., 

Inoceramus SP-----------..:.~L~--~~-=- .:. ___ _:: ____ ..:_· ___ :.. · 9, 27; 3~ -:;· ;· 

Pteria nebrascana Evans-and Shumard ______ ~...: ..:: :.. .::. __ i~ ..:.:.. :'26,32 

Pteria SP----------------~--:--::--=-:----~~----------;,-----.:- : .. go 

Pecten nebrascensis Meek. and Hayden ____ _:_ _______ ...:,-,..~ ;:: 28 ... 

~:~el~ ~~u::~:~:~'M~~i{~~~d ~H-;yd~~== ==: =~;======··: ' ' · ft.•!<.:, 

Pholadornya n. sp...: ____ .:. ___ :..; __ .:_ _____ _:_:__:_,_:..:.._ ~-.:..----"' :::. J · '. 14 

Ouspidaria ventricosa Meek and Hayden~~ ___ ::__:::_ _ _-:_:.:_:;:_:.:.: · 4J 8::_ ·~ 

ni ll~ hu.milis Meek and Hayden-..,.------------------:- ,{. 19 .) .. -

Eriphyla gregat·ia Meek. and Hayden?__-:--'------;:--:-:---..,.,, , . , 3 

Lucina occidentalis Morton __ · _____ .:__~_ _..:::.. ____ _:_· ____ 10, 23, 27,30 

Lucina. sp __________ ..: _______ .:. __________ ~ ___ :__::_ ____ 3; 6/ 19,· 2M· 

Protocardia subquadt·ata ~vans and Shumard ____ ..:. ___ :.:. ,,4, 15, 17.·" 

Tellina scUula Meek and Hayden------------------,-;.,~ -:= '· ... .JQ ~ 

M actra gracilis Meek and Hayden-------- ------"'"--1, i, 1l,, ~3, 1 , 

- 22, 28, 34; 35, 36,' 38, 40, 4l . ' 

Ma.ctra canonensis Meek ____ _:_ ___________ .::, ___ ..: ;.: _:_ __ :.: i__ , · .:·\·33 [\ 

M actra sp ___________________ _: __ :.. _______ _: :_: ____ :_· ___ ..:::.: :..' '14 ?,-17o. · ·' 

Dentalium gracile ;Hall and Meek __________ :_ __ : _ _: ______ 20, ~? > · 

Dentalium SP----------------------------------------- 4 · Lunatia dakotensis Henderson ___ _::_:_ _____________ :_..., 3, 9?, 20, 33 

Lunatia sp ______ . ___ _:_ ____ .:_""_.:_':.:. _..: :.: .:..-_ ______ ..:....: ___ :..:_ _______ · 27; 37? · 

Turritella sp., probably new---------------------------- Z 

Fasciolaria'f cf. F. cheyennensi.<S Meek: ~nd,. H~x4en.:_:..~-. ?~ 20 
STRATIGRAPHY OF UPPER CRETACEOUS ROCKS IN EASTERN COLORADO 231 

Fossils from the "transition zone" of the P·ierre sha~e-Contd. 

Localitty 

Anchurar SP-------------------- -------------- ------ 31? 

Ha.minea subcylimJrica (Meek)----------·-------------- 3 

Cinulia ( OUgoptycha) concinna Hall and Meek---------- 3, 32 

Baculites grandis Hall and Meek ___ 2, 11, 12, 17, 20, 24, 25, 29?, 31 

Baculi tes SP---------------------7, 17, 28, 34, 35, 36, 37, 38, 40?. 

Discosaaph!ites o<Yn:radi (Morton)---------------------- 30, 39. Discoscaphites ch~yennensis (Owen)------------------- 3 

Discoscaphites ma'Y}danensis (Morton) ----------------'-5, 17, 22· 

Discoscaphites cf. _D. abyssinus (Morton)-------------- . 20. 

Discoscaphites cf. D. nicolleti. (Morton)---------------- 22. 

Discoscaphites sp __________ _4, 6, 7, 8, 9, 11, 16, 18, 20, 22?, 23, 27 

Acanthosca,phites SP------------------------------ 33?, 35, 37? 

Sphenodiscus lenticularis (Owen)---------------------- 6· 

B elemnitella bulbosa Meek and Hayden_________________ ·26 

Decapod crustacean, undetermined_____________________ 4 

1. 15802, north tributary of Fountain Creek, north of Colorado 

Springs. 

2. 15806, SW% sec. 35, T. 13 S., R. 58 W. 

3. 15814, 15.1 mil~s north of Limon on Bru~h road. 

4. 15815, 15.1 miles north of Limon on Brush road, above 

15814. 

5. 15816, 21.3 miles from Limon, just east of road bridge across. 

Beaver Cree){ on road to Agate. · 

6 15825, NE% sec. 24, T. 2 S., R. 55 ,W. 

7. 15826, 9.1 miles north of Last Chance store. 

8. 15827, NEIA, sec. 15, T. 3, S., R. 56 W. 

9. 15828, SW% sec. 5, T. 2 S., R. 55 W. 

10. 15830, NWIA, sec. 6, T. 10 S., R. 55 W. 

11. 15832, SEIA, sec. 36, T. 9 S., R. 55 W. 

12. 15834, NWIA, sec. 30, T. 9 S., R. 55 W. 

13. 15804, one-eigh.th mile north of southeast corner sec .. 3, T. 

14 S., R. 58 W. 

14. 15838, S'WIA, sec. 33, T. 3 S., R. 58 W. 

15. 15842, northeas~ corner sec. 1, T. 2 S., R. 58 W. 

16. 15844, SWIA, sec. 7, T. 2 S., R. 53 W. · 

. 17. 15845, SW% sec. 29, T. 11 S., R. 56 W.; East Rush Creek. ·· 

18. 15848, NWIA, sec. 6, T. 2 N., R. 55 W. 

19. 15349, southwest corner sec. 1, T. · 5 N., R. 59 W. 

20. 15850, center sec. 4, T. 13 S., R. 57 W., Rush Creek. 

21. 15851, NEIA, sec. 30, T. 13 S., R. 58 W., Little Horse Creek. 

22. 15852, S% sec. 20, T. 13 S., R. 58 W. 

23. 15853, N¥2 sec. 26, T. 12 S., R. 56 W. 

. 24. 15856, S¥2 sec. 7, T. 14 S.~ R. 57 W. 

25. 15857, NW1

4 sec. 13, T. 14 S., R. 58 W., Horse' Creek. 

26. 15875, SWIA, sec. 16, T. 8 N., R. 57 W. 

27. 15876, E% sec. 4, T. 8 N., R. 55 W., South Pawnee Creek. 

28. 15956, SWIA, sec. 31, T. 13 S., R. 66 W., Monument Creek 

north of Colorado Springs; 

29. 15961, center SW:JA, sec. 30, T. 13 S., R. 66 W. 

30. 15969, SEIA, sec. 3, T. 1 N., R. 43 W., 3 miles east ·of Wray. 

31. 15971, NWIA, sec. 6, T. 2 S., R. 42 W. 

32. 16307, SE:!4 sec. 5, T. 3 S., R. 57 W. 

33. 15955, SWIA, sec. 21, T. 14 S., R. 66 W., 2 miles southeast of 

Colorado Spr!ngs. 

34. 15957, NW% sec. 31, T. 13 S., R. 66 W., Monument Creek, 

north of C<?lorado Springs. 

35. 15958, :NW14 sec. 31, T. 13 S., R. 66 W. 

36. 15960, NW1,4 sec. 31, T. 13 S., R, 66 W. 

37. 15970, near center sec. 21, T. 2. S., R. 43 W. 

38. 15805, NW14 sec. 2, T. 14 S., R. 58 W., bank of Horse Creek 

250 feet east of bridge. 

39. 15R36, NE% sec. 13, T. 9 S., R. 56 W. 

40. 15803, line betw.een sees. 3 and 10, T. 14 S., R. 58 W. 

41. 15807, E% sec. ~3, T. 13 S., R. 58 W. 

FOX HILLS SANDSTONE 

The Fox Hills sandsto:ne, which overlies the Pierre 

shale, outcrops north and northwest of the area shown 

on plate 64. Its geographic distribution and some featur.es of its stratigr~phic relations with the Pierre shale 

are briefly discussed in another paper 88 dealing with the 

later Cretaceous formations of the Denver Basin. Be~ 

cause of the faunal relationships between the transition 

zone of the Pierre shale and the Fox Hills sandstone it 

is desirable to include in this paper a summary of 

identifications of fossils collected from the Fox Hills. · 

As used by the writers the name "Fox Hills sandstone" is applied to a unft ranging from 200 to a )ittle 

more than 300 feet in thi~kness, consisting in the lower 

part of buff or brown sandstone and sandy shale 'that 

contains large gray to brown hard sandy concretions 

and in the upper part chiefly of soft sand or poorly -consolidated white sandstone. ·. In general this is also the 

way the Fox Hills of eastern Colorado was restrict~d by 

the Rocky Mountain Association of Petroleum Geologists in 1932·. 

89 

Because the contact of the Fox Hills sandstone and 

the Pierre shale is transitional in many places and because the zones of ·large concretions at the base of the 

Fox Hills were not traced in qetaiLover tP,e complete 

area from which collections were made, the fossils colr 

lected from the Fox Hills sandstone are shown in two 

lists. The first shows species in lots whose positi~n is 

somewhat doubtful; that. is, they may possibly belong 

to . the transition zone of the Pierre shale~ though th~ 

writers believe them more likely to represent Fox Hills 

horizons; the second shows the species in lots assig:ri~d 

with confidence. 

The fauna contains many species that appear firf;t in 

sandy rocks at various h9rizons in the,Montana g!'oup 

of other areas, though such species as Baculites griindis 

Hall and Meek, Discoscdphites conradi (Morton), and . 

Sphenodis()W8 lenti(!Ulari{J (Owen) always indiclite a --

very late Cretaceous horizon wherever found. Some 

of the lots-for example, collection 15865.,.-show a defi- . 

nite admixture of nonlr\ari:p.e elmnents, a not unusual 

occurrence in the Fox H,ills . . 

Fossils probably from the lower part of the Fox Hiils 

sandstone 

Locality 

Solemya bilix White__________________________________ 3 

SolefnyafsP------------------------------------------- 8 

Pteria nebrascana Evans and Shumard________________ 5, 6 

Volsella cf. V. 1neeki (Evans and Sh~mard) ------------ ' 4 

Crenella elegantula Meek and Hayden __________________ .. 5 

Pholadomya n. SP------------------------------------- 3 

88 Dane, C. H., and Pierce, W. G., Dawson and Laramie formations in 

southeastern part of Denver· Basin, Colo. : Am. Assoc. Petroleum· Geologists Bull., vol. 20, no. 10, pp. 1308-1328, 1936. 89 Lovering, T. S., Aurand, H. A., Lavington, C. S., and Wilson, 

J. H., Fox Hills formation, northeastern Colorado: Am. Assoc. Petroleum Geologists Bull., vol. 16, no. 7, pp. 702-703, 1932.