LIBRARY COPY 

Bedrock Geology of 

the Kassler Quadrangle 

Colorado 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 421-B 
Bedrock Geology of 

the Kassler Quadrangle 

Colorado 

By GLENN R. SCOTT 

GEOLOGY OF THE KASSLER QUA.DRANGLE, JEFFERSON 

AND DOUGLAS COUNTIES, COLORADO 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 421-B 

A survey of the east flank of the Colorado Front 

Range with emphasis on Cretaceous rocks and 

on structural geology 

0 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1963 , 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEWART L. UDALL, Secretary 

GEOLOGICAL SURVEY 

Thomas B. Nolan, Director 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington 25, D.C. 
CONTENTS 

Page 

Abstract------------------------------------------- 71 

Introduction_______________________________________ 71 

Acknowledgments_______________________________ 73 

Geographic setting______________________________ 73 

General geology_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 73 

Precambrian metamorphic and igneous rocks_______ 7 4 

Metasedimentary rocks______________________ 74 

Quartzite ______________________________ · 7 4 

Sillimanitic biotite-quartz gneiss__________ 7 4 

Biotite-quartz gneiss_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 7 5 

Amphibolite _________________________ .___ 75 

Lime silicate gneiss_____________________ 77 

Granitized metasedimentary rocks_____________ 78 

Granite gneiss and migmatite_ _ _ _ _ _ _ _ _ _ _ _ 78 

Sillimanite granite gneiss_________________ 80 

Hornblende granite gneiss _______________ -. 80 

Intrusive rocks------------------------------ 81 

Gneissic granite________________________ 81 

Quartz diorite and hornblendite _ _ _ _ _ _ _ _ _ _ 81 

Biotite-muscovite granite________________ 82 

Pikes Peak granite______________________ 83 

Granite pegmatite in Pikes Peak granite_ 84 

Granite pegmatite_______________________ 84 

Paleozoic sedimentary rocks______________________ 85 

Sandstone dikes_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 85 

Source of the sand_______________________ 86 

Process of emplacement__________________ 87 

Fountain formation__________________________ 88 

Lyons sandstone ________ : ______ -·-___________ 89 

Lykins formation____________________________ 90 

Mesozoic and Cenozoic sedimentary rocks__________ 91 Rals~on Creek formation_____________________ 91 

Morrison formation__________________________ 92 

Lytle and South Platte formations____________ 94 

Graneros shale, Greenhorn limestone, and Carlile shale __________________________ .:. _ _ _ _ _ _ 94 

Graneros shale__________________________ 94 

Greenhorn limestone_____________________ 95 

Carlile shale____________________________ 95 

General geology-Continued 

Mesozoic and Cenozoic sedimentary rocks-Con. 

Niobrara formation _________________________ _ 

Fort Hays limestone ~ember ____________ _ 

Smoky Hill shale member _______________ _ Pierre shale _____________________ :... __________ _ 

Fox Hills sandstone ________________________ _ 

Laramie formation _________________________ _ ])awson arkose ____________________________ _ 

Intrusive dike rocks ____________________________ _ 

Andesite ________________________ - - - - - - - - - - -

Rhyolite_--·----- __________________ --- _____ _ Structure _________________ :_ _______________________ _ 

Precambrian structure __________________________ _ 

Faults ______________ . ___________ ------- ____ _ 

Folds ___ -·- ______________________ ----·------_ Pennsylvanian structure ________________________ _ 

Laramide structure ____________________________ _ 

Faults------------------------------------- Folds_. ___________________________________ _ 

History of Laramide structure _______________ _ 

Post-Laramide structure ________________________ _ 

Geologic history ___________________________________ _ 

Economic geology __________________________________ _ 

Nonmetallic deposits _________________ --- _______ _ 

Mica--------------------------------------

Feldspar----------------------------------- Clay _____ .;, _______________________________ _ 

. Coal.:. ____________________________________ _ 

Limestone ______ - _____ ..; ____ - - - - - - - - - - - - -·~ - -

Structural stone-------------------------~--

Sand-------------------------------------- Road metal _______________________________ _ 

Metallic deposits _______________________________ _ Iron ______________________________________ _ 

Copper ___________________________________ _ 

Uranium __________________________________ _ 

Engineering problems _______________________________ _ 

Fossil localities _______________________ -- __ - ___ - ____ _ 

References cited ____________________ ----------------

lndex----------------------------------------------

m 

Page 

97 

97 

98 

99 

104 

104 

106 

106 

106 

107 

107 

107 

108 

108 

108 

109 

109 

110 

111 

112 

113 

114 

114. 

114 

114 

114 

114 

115 

115 

115 

115 

115 

116 

116 

116 

117 

118 

120 

123 
IV CONTENTS 

ILLUSTRATIONS 

J:>age 

PLATE 2. Bedrock geologic map of the Kassler quadrangle_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ In pocket 

3. Correlation of rocks in the Kassler quadrangle with a reference sequence for the western interior of conterminous 

1Jnited States--------------------------------------------------------------------------------- In pocket 

FIGURE 28. IndexmaP----------------------------------------------------------------------------------------- 72 

29. Granite gneiss and migmatite _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 79 

30. Pikes Peak granite in nearly fresh outc~OP-------·------------------------------------------------------ 83 

31. Distribution of sandstone. dikes ______ ---______________________________________________________________ 85 

32. Thinning of the Fountain formation to the south by faulting_______________________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 89 

33. Contour diagram of ·lineations___________________________________________________________ _ _ _ _ _ _ _ _ _ _ _ _ _ 1 08 

34. Jarre Creek fault an~ general view of south end of quadrangle____________________________________________ 110 

35. Cross section of Front Range showing tilting of mountain front___________________________________________ 111 

TABLES 

Page 

TABLE 1. Spectrographic analyses of sandstone dikes and Sawatch quartzite________________________________________ 87 

2. Stratigraphic distribution by ammonite zones of fossils of the Pierre shale__________________________________ 100 

3. Lithology and faunal zones of the Pierre shale------------------------------.---~------------------------ 103 
GEOLOGY OF THE KASSLER QUADRANGLE, JEFFERSON AND DOUGLAS COUNTIES, COLORADO 

BEDROCK GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

By GLENN R. ScOTr 

ABSTRACT 

The Kassler quadrangle lies along the South Platte River 

on the east flnnk of the Colorado Front Range a few miles 

south of Denver. 

Precambrian metamorphic and igneous rocks constitute the· 

bedrock of the mountains. The oldest rocks are metasedimentnry quartzite, amphibolite, lime silicnte gneiss, biotite-quartz 

gneiss, nnd sillimnnitic biotite-quartz gneiss. These older rocks 

were invaded by granitic solutions that generally produced 

large bodies of grnnite gneiss, but that locally were so intimately interbedded with the metasedimentary rocks that migmntite wns formed. Gneissic granite (probably equivalent 

to the Boulder Creek granite) and quartz diorite and associnted hornblemHte also inyaded the older rocks and were given 

n metnmorphic structure by the last stage of regional metamorphism to affect the crystalline rocl\:S of the Front Range. 

The biotite-muscovite granite, the Pikes Peak granite, and 

grnnite pegmatite were intruded into all earlier rocks in later 

Precambrian time. 

In Inte Precambrian time a r:mg-e of low mountains apparently wns uplifted in the present position of the Colorado 

Front Runge, nnd fnults, such as the Jarre Creek fault and 

other northwest- and northeast-trending faults that cross the 

l1'rout Rnnge, were formed. These faults are the framework 

of the ll'ront Rnnge fault system, and major movements have 

tnken plnce nlong them periodically since Precambrian time. 

After erosion in late Precambria~ and E'arly and Middle Cambrian time, the sea encroached on the area in Late Cambrian 

time and started to deposit the Sawatch quartzite over the young 

fnults. After only a few feet of sand was deposited on the sea 

fioor, the Precambrian fnults were opened, possibly by earthqunlces; sand wns sucked or injected into the fault system, and 

a widesprend networl\: of sandstone dikes was created. 

About 11,500 feet of sedimentary rocks unconformably overlie the crystalline rocl\:S. The unconformity is ·the result of 

erosion of all pre-Pennsylvanian sedimentary rocks as the 

Peunsylvnnian Ancestral Rockies were uplifted. The Fountain 

nrkose contnins detrital material eroded from these mountnins. Transgression of the Permian sea and reworking of 

continentnl fnn deposits eroded from the mountains resulted 

in deposition of dune sand of the Lyons sandstone. The sea 

remained in the area only long enough to deposit maroon siltstone and limestone in the lower part of the Lykins formation. 

~'he upper pnrt, which is of Permian ( ? ) and Triassic ( ? ) age, 

contains . maroon siltstone and sandstone deposited by wind 

nnd streams. The Ralston Creek formation of Jurassic (Kimmeridgiun'l) age contains fresh-water limestone, siltstone, 

jasper, and locally gypsum. At the base of the Morrison formation is a lenticular sandstone unit. The upper part of the 

Morrison formation is also of continental origin and consists 

of fresh-water limestone, variegated siltstone, and thin sandstone beds. 

Most of the Cretaceous beds in the urea are of marine origin. 

The Lytle and South Platte formations are predominantly beach 

sand, but contain a thin bed of marine shale near the middle. 

The Graneros shale, Greenhorn limestone, and Carlile shale consist of black marine shale including (a) a thin siliceous siltstone (Mowry equivalent) in the lower part; (b) calcareous 

shale, brown calcarenite and gray dense limestone in the middle, 

and (c) chalky shale, silty and sandy shale, and calcarenite in. 

the upper part. The Niobrara formation consists of the Fort 

Hays limestone member at the base and the Smoky Hill shale 

member. The Pierre shale is predominantly dark marine shale, 

but contains the friable marine Hygiene sandstone member 

near the middle and another soft sandstone near the top. Faunal 

zones were defined in the Pierre shale on the basis of n remarkable fauna of ammonites. The Fox Hills sandstone, a brackishwater marine sandstone, overlies the Pierre shale. The sea 

withdrew from the area for the last time after the Fox Hills 

sandstone was deposited. The Laramie formation, which overlies the Fox Hills, was deposited in the streams and swamps ; it 

contains the only minable deposits of coal in the area. The 

Dawson arkose contains the coarse detritus that was eroded as 

the Front Range was uplifted during Laramide time. 

Precambrian faults were reactivated during the Laramide 

orogeny and possibly some new faults were formed. Late Cretaceous ( ?) and Tertiary ( 'l) dike rocks were intruded into the 

faults and later both the dike rocks and the sandstone dikes 

were brecciated. 

INTRODUCTION 

The Kassler quadrangle, an area of about 57 square 

miles in central Colorado, is about 18 miles south of 

Denver (fig. 28). The quadrangle is in Douglas County 

except for a small area northwest of the South Platte 

River that is in Jefferson County. 

The quadrangle is accessible by U.S. Highway 87 

from the east and by Colorado Routes 67 from the south 

and 75 and 221 from the north. County and U.S. 

Forest Service roads, logging roads, and trails traverse 

the western third of the area. The Atchison, ·Topeka 

and Santa Fe Railway and the Denver and Rio Grande 

Western Railroad cross the northeast corner of the area. 

71 
72 

40" 

39" 

GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

105" 

LARIMER j 

I 

' 0 ~-~ \ 2 . I 

~r---7-------1 

( I O (_ BOULDER 

Z ). I 

~ ) 

\ 

,-1 

/ Flatirons X 

'r-----:J=-

1 L GILPIN 

,., \ 

......., 

'"\__").. Idaho Springs0 ---.... 

~lver Plume 

CLEAR CREEK I 

I 

ADAMS 

I Po,.k I 

ARAPAHOE 

'---+--+--¥-....::S:!:p.:..:.ri:.:!ng~s:...._j Strontia I South Platte R II R"d ELBERT 

PARK 

1

pegmatite distric~sse 1 ge 1 

I I ~ Perry Park I 

I / X I 

~I 2 ;; I I 

~ I (;) I 

I TELLER {1'\ I 

I I 

I I 

1 rj 

I I I L __ l 

EL PASO 

iGarden of the Gods 

~olorado Springs 

N 

1 

OCalhan 

FIGURE 28.-Index map showing Kassler quadrangle and other places mentioned in text. 
BEDROCK GEOLOGiY" 73 

Commercial activities include farming,' manufacturing, mining, and supplying of water to cities. Dry 

farming and beef-cattle raising are the two main agricultural activities. A large explosives manufacturing 

plant is at Louviers in the northeast part of the area, 

and a guided missile plant is north of l{assler. One of 

the Denver water-supply filtration plants is at Kassler, 

where the South Platte River emerges from the mountains, and a pumping plant to supply water for the city 

of Aurora lies east of Willow Creek. 

The study of the l(assler quadrangle was undertaken 

in 1950 primarily to provide geologic information required for engineering projects planned by the Denver 

City Water Board and the U.S. Bureau of Reclamation 

along the South Platte Riv~r. 

The geology was mapped in 1950, 1955, and 1956 on 

aerial photographs and then transferred to the topographic map of the quadrangle at the sca~e 1 : 20,000. 

The distribution and attitude of .the rocks in the quadrangle are shown on the geologic rna p (pl. 2) . Color 

names and designations in. the text refer to the RockColor Chart of the ·National Research Council (Goddard and others, 1948) and to the Munsell soil-color 

chart (Munsell Color Co., 1954) which were used 

throughout the fieldwork. The fossil localities are 

listed on pages 118-120; the localities are also shown 

on plate 2. 

ACKNOWLEDGMENTS 

Owners of the Willow Creek, Slocum, Nelson, Penley, 

Lambert, Feeley, N ockols, and Helmer ranches made 

their lands accessible for this survey. Ray E. Johnson, 

forest ranger at the Indian Creek ranger station, gave 

helpful information on roads and trails in the Pike 

N atJional Forest. 

Several specialists gave advice on fossils. William A. 

Cobban of the U.S. Geological Survey visited the area 

several times and made fossil collections and identifications that are the 'basis for most of the stratigraph~c 

zoning of the Cretaceous formations. R. E. Peck of the 

University of Missouri identified charophytes from the 

Jurassic formations. 

GEOGRAPHIC SETTING 

The quadrangle is partly in the Colorado Piedmont 

section of the Great Plains physiographic province and. 

partly in the Colorado Front.Range (Fenneman, 1931). 

The surface of the plains rises gradually toward the 

southwest and passes from gently rolling hills and 

gullies to dissected pediments at the foot of the mountains. The pediments are largely destroyed nearer the 

mountains, and in their place rise steep northwesttrending hogback ridges that dip sharply away from the 

higher mountains of the Front Range (pl. 2). The 

High Plains in the area range in altitude from 5,500 to 

6,500 feet; the mountains, from 5,600 to 8,050 feet. The 

total relief is 2,550 feet. · 

Many of the streams in the area are consequent upon 

faults, upon a northwest-trending foliation of the metamorphic rocks in the mountains, and upon the hogbacks 

of sedimentary rocks that flank the mountains on .the 

northeast. Most of the streams on the pla:ins are undergoing rejuvenation; both perennial and intermittent 

streams have cut deep arroyos. The whole area is 

drained by the South Platte River and its tributaries, 

Plum, Indian, Willow, Jarre, and Rainbow Creeks. 

(pl. 2). 

GENERAL GEOLOGY 

Rocks ranging in age· from Precambrian to Recent 

crop out in the Kassler quadrangle. 

Rocks of Precambrian age crop out in the western 

part of the area and form the mountainous region of. 

the quadrangle. Sedimentary rocks crop out east of 

the mountain front; the more resistant units form 

ridges parallel to the mountains. The formations of 

Paleozoic age include the Fountain formation of Pennsylvanian and Permian age; the Lyons sandstone of 

Permian age; and the Lykins formation, which includes 

the Harriman shale, Falcon limestone, Bergen shale, 

Glennon limestone, and Strain shale members of LeRoy 

(1946, p. 31), of Permian(~) and Triassic(~) age. The 

Mesozoic formations are the Ralston Creek formation, 

which includes the Entrada ( ~) sandstone, and the Morrison formation of Late Jurassic age; the Lytle and 

South Platte formations of Early Cretaceous age; the 

Graneros shale of Early and Late Cretaceous age; and 

the Greenhorn. limestone, Carlile shale, and Niobrara 

formation, which includes the Fort Hays limestone and 

Smoky Hill shale members, the Pierre shale, which includes the Hygiene sandstone member, the Fox Hills 

sandstone, the Laramie formation, and the lower part 

of the Dawson arkose, all of Late Cretaceous age. Intruded into the Precambrian rocks are dikes of andesite 

that may ·be of Late Cretaceous age. 

Rocks of Cenozoic age include the upper part of the 

Dawson arkose of Paleocene age, rhyolite of possible 

Paleocene age, and a series of Quaternary surficial deposits that are described in chapter A of this report 

(Scott, 1963). Pre-Wisconsin surficial deposits include 

three alluviums and an older loess that are of Nebraskan 

or Aftonian, Kansas or Yarmouth, and Illinoian or 

Sangamon age. Wisconsin surficial deposits include 

the Louviers alluvium, a younger loess, and the Broadway alluvium. The Recent deposits include three 

alluvial deposits, two eolian deposits, deposits of bog 

clay, and landslides. 

The bedrock was tilted and faulted by uplift of the 
74 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

mountains. The oldest sedimentary rock, the Fountain 

formation, dips northeast away from the mountain 

front and unconformably overlies the Precambrian 

rocks. The sedimentary and Precambrian rocks are cut 

by a series of northwest-trending faults, most of which 

are believed to have formed during Precambrian time 

and which were reactivated during the formation of the 

ancestral Rockies in Pennsylvanian time and again during the Laramide revolution in Late Cretaceous and 

early Tertiary time. 

PRECAMBRIAN METAMORPffiC AND 

IGNEOUS ROCKS 

The Precambrian rocks consist of a complex series of 

metamorphosed sedimentary and igneous rocks. For 

description they are divided into three categories: (a) 

metasedimentary rocks, (b) granitized metasedimentary rocks, and (c) intrusive rocks. The metasedimentary rocks are the oldest of the Precambrian 

formations. Mappable units are quartzite, sillimanitic 

biotite-quartz gneiss, biotite-quartz gneiss, amphibolite, 

and lime silicate gneiss. Some of these rocks were 

changed to granite gneiss ahd migmatite, then were intruded by a series of igneous rocks, from oldest to 

youngest, gneissic granite, quartz diorite and hornblendite, biotite-muscovite granite, Pikes Peak granite, 

and granite pegmatite. 

METASEDIMENTARY ROCKS 

Metasedimentary rocks are the oldest rocks in the 

quadrangle and have been described previously in other 

areas of the Front Range. · Ball (1906, p. 374; Spurr 

and others, 1908, p. 37) applied the name Idaho Springs 

formation to a similar series of metamorphic rocks, believed to be of sedimentary origin, in the vicinity of 

Idaho Springs, Colo. The terms used hy Ball (Spurr 

and others, 1908, p. 37) and ·the terms for equivalent 

rocks in the Kassler quadrangle are given below: 

Ball (Spurr and others, 1908, p. 87) This report 

Lime. silicate member______ Lime silicate gneiss 

Hornblende-diopside gneiss 

unit ------------------- Amphibolite 

Biotite schist_____________ Biotite-quartz gneiss 

Biotite sillimanite schist_ __ Sillimanitic biotite-quartz 

gneiss 

Quartz-magnetite gneiss ___ Quartzite 

The lithologic names of the metasedimentary rock units 

of the Kassler quadrangle are the same as many of those 

used by Harrison and Wells ( 1956, p. 37; 1959, p. 5). 

QUARTZITE 

Quartzite crops out a8 irregularly shaped bodies east 

and northeast of Thomas Hill, in the south-central part 

of the quadrangle, and as persistent layers in an area 

a;bout 1f2 to 1 mile north of the Indian Creek ranger station, in the southwest quarter of the quadrangle. Most 

of the quartzite bodies lie in conformable contact with or 

near lime silicate gneiss or amphibolite. 

The quartzite is a medium-grained medium-gray rock 

that weathers olive gray. It consists mostly of quartz 

with some biotite, plagioclase, and magnetite and, 

locally, of minor amounts of hematite, apatite, epidote, 

diopside, and sericite. Epidote and diopside are common in the quartzite bodies near lime silicate gneiss, 

such as the outcrop in the NW%,NEY.t, sec. 3, T. 8 S., R. 

69 W. Magnetite is abundant in the quartzite in and 

just north of the NW%NE% sec. 6, T. 8 S., R. 68 W., 

where two prospect pits were dug. Apatite is included 

in the quartz grains. The following table gives the 

modes (volume percent) of two samples of the quartzite: 

SC-2 

Quartz_____________________________ 75 

Biotite_____________________________ 5 

Plagioclase _______________ ·___________ 20 

Muscovite__________________________ Tr. 

Sericite_____________________________ Tr. 

SC-43 

93 

7 

Tr. 

Magnetite__________________________ Tr. _________ _ Apatite ___________________________ ..: __________ _ Hematite ___________________________________ --

SC-2: NW~NE~4 sec. 3, T. 8 8., R. 69.W. 

SC-43: NW~NE~ sec. 3, T. 8 8., R. 69·W. 

Tr. 

Tr. 

The quartzite is even grained; most grains are 0.2 

mm in diameter although a few are as much as 0.33 mm. 

Most grain bounda.ries are straight or slightly curved. 

The magnetite-bearing facies is slightly coarser and 

contains megascopic magnetite grains. Bedding resulting from the alinement of concentrations of hematite, 

magnetite, and biotite can b~ seen in the quartzite. 

BILLIMANITIC BIOTITE-QUARTZ GNEISS 

. The sillimanitic biotite-quartz. gneiss is confined to 

the southern part of the quadrangle and is particularly 

abundant-where the foliation turns from N. 75° W. to 

N. 20° W. in sees. 34 and 35, T. 7 S., R. 69 W., and in 

sec. 3, T. 8 S., R. 69 W. (pl. 2). Contacts between the 

sillima.nitic biotite-quartz gneiss and other metasedimentary rocks are conformable. 

Sillimanite cannot easily be detected in the field in 

amounts less than 5 percent; therefore, only those rocks 

with more than 5 percent sillimanite and with abundant biotite and quartz but little feldspar are jncluded 

in sillimanitic biotite-quartz gneiss. 

The sillimanitic biotite-quartz gneiss is a yellowishgray well-foliated rock in which plates of biotite and 

needles of sillimanite are set in a platy matrix of quartz 

and feldspar. A freshly broken fragment is dark gray 
BEDROCK GEOLOGY 75 

and vitreous and appears quartzitic. On weathered 

surfaces the sillimanite gives a yellowish-gray or lightgray felted appearance like asbestos, or a silken sheen 

may be reflected from the needlelik_e cryst~ls. The 

gneiss is fine crrained except where It contan1s large 

masses of ma;1etite~ Porphyroblasts of microcline 

and quartz as large as one-half inch in diameter are 

common. One-fourth-inch biotite porphyroblasts also 

occur in the o-neiss near the Pikes Peak granite. Biotite flakes a:d matted layers of sillimanite generally 

produce the foliation and the lineation. Locally ':foliation is due to magnetite. In one specimen compo~ed 

of magnetite and sillimanite, one-fourth mm-tluck 

layers of magnetite are wrapped around the_ crests ~nd 

troughs of isoclinal folds only one-half Inch lngh. 

Macrnetite stands out fron1 the weathered surface of the b • 

rock n,nd stains it light brown owing to the alteratiOn 

of the magnetite to limonite. 

The sillimanitic biotite-quartz gneiss is composed of 

quartz, biotite, feldspar, muscovite, magnetite, and sillimanite. The plagioclase content probably averages 

about 20 percent, but may be as high as 50 percent. As 

a corollary, the quartz content, which is commo~1ly n~ar 

45 percent, may be as low as 30 percent. MICrochne 

rancres from 2 to 12 percent. The following table gives 

the ~nodes (volume percent) of three samples of sillimanitic biotite-quartz gneiss: 

SC-9 

Microcline ______ ---------- Quartz __________ ---_-----

Plagioclase _____ - - - - - - - - - - -

Biotite __ ---_------------- Muscovite _______ - ___ ----- Sillimanite _______ -_-_-----

Magnetite _______ ---------

SC-9: NW~NE~ sec. 3, T. 8 S., R. 69 W. 

SC-12: NW~~NE~ sec. 3, T. 8 S., R. 69 W. 

SC-45: SE~Nl<~H sec. 34, T. 7 8., R. 69 W. 

SC-12 I SC-45 

!; 4~ --------50 

3 40 30 

8 2 15 

.2 1 Tr. 

25 10 5 

5 5 Tr. 

The sillimanitic biotite-quar•tz gneiss in thin sections 

has a texture dominated by prismatic sillimanite crystals whose greatest dimensions are subparallel to the 

plane of schistosity. The biotite grains also have a 

preferred orientation and lie along grain boundaries of 

the feldspar and quartz. Some of the biotite grains 

have sutured boundaries embayed with elongate grains 

of feldspar and quartz. Feathery sheaves of needlelike crystals of sillimanite lie along fractured zones 

that contain ground-up fragments of feldspar and 

quartz. Most of the feldspar along the fraCtured zones 

is altered to sericite. Muscovite lies parallel and intergrown with biotite in the biotite-rich layers. The magnetite grains in the fractured zones are elongate; those 

654901 Q-63~-2 

in the unfractured part of the rock are rounded, oval, 

or irregular shaped. Hematite a.nd limonite halos surround' some of the magnetite grains. 

BIOTITE-QUARTZ GNEISS 

Biotite-quartz gneiss underlies a very small part of 

the map area (pl~ 2). Most of the mappable bodies of 

biotite-quartz gneiss are along the west margin ~nd in 

the southeast corner of the quadrangle, but thin· unma.ppa'ble bodies are conformably interlensed with 

granite gneiss throughout the quadrangle. The contacts between the biotite-quartz gneiss and other metasedimentary rock units are conformable. The contacts 

are marked by slight changes in the amounts of silli-. 

manite, quartz, and microcline. Rocks that are mapped 

as biotite-quartz gneiss contain abundant biotite and 

quartz, but sparse feldspar. · 

The biotite-quartz gneiss is very light gray mottled 

with black and commonly has a salt-and-pepper appearance· it is medium grained, though some outcrops con-

' B. tain crrains of biotite one-fourth inch in diameter. lO- b • • 

tite layers produce the foliation. The gneiss contains 

about 70 percent quartz, 20 percent biotite, and 10 percent feldspar although composition varies considerably 

between outcrops. Microcline and oligoclase are the 

most common feldspars. Muscovite, ma,gnetite, sillimanite, apatite, hornblende, titanite, an~ g~r~et are 

accessory minerals. Some of the muscovite IS Ill parallel growth with biotite. Sericite (mostly altered 

plagioclase) makes up as much as 10 percent of soi?e 

weathered rocks. Most of the biotite lies along grain 

boundaries of quartz and plagioclase. Euhedral apatite is included in larger anhedral grains of quartz. 

Grain boundaries are straight or slightly wavy; sutured boundaries are uncommon. Most of the magnetite is between other grains; however it is also included 

in plagioclase and is intergrown with sillimanite. . 

A garnetiferous variety of the biotite-quartz gneiss 

crops out in the SE14NElt4 sec. 34, in the adjacent part 

of sec. 35, T. 7 S., R. 69 W., and in the NEJ4NWJ4 sec. 

28, T. 7 S., R. 69 "V. The garnetiferous variety is 

medium crray to o-rayish red, depending on the amount b b . 

of garnet. Many of the biotite flakes exceed 4 mm In 

diameter. Garnet makes up as much as 20 percent of 

the crneiss and is in well-formed crystals as large as b • l 3 mm in diameter. The garnet apparently IS a mandine, the same variety found in the Freeland-Lamartine 

district by Harrison and Wells (1956, p. 40). 

AMPHIBOLITE 

The amphibolite, which Balf (Spurr and ot~ers, 

1908, p. 37) included in the Precambrian Idaho Spnngs 

formation, crops out throughout the western part of 
76 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

the quadrangle. In the southwestern part of the quadrangle the amphibolite is interlayered and grada.tional 

with the granite gniess and migmatite, quartzite, and 

lime silicate gneiss, and may constitute as much as 10 

percent of the rock. Few of the layers can be followed 

for more than 100 feet and their contacts are usually 

covered. The float indicates that most of the small 

ridges in the southwest corner of the area are underlain 

by layers of amphibolite. In the rest of the western 

part of the quadrangle the amphibolite occurs in pods 

from a few inches to ten's of feet in length associated 

with smaller pods of lime silicate gneiss, .both enclosed 

in the granite gneiss and migmatite. Typically, several pods of amphibolite are alined parallel to the foliation of the granite gneiss and the foliation of the pods 

is parallel to that of the granite gneiss. A few bodies 

of amphibolite crosscut the foliation of the enclosing 

rock, but their foliation is parallel to that of the enclosing rock. 

The amphibolite is typically a dark-gray or dark 

greenish-gray fine- to medium-grained, even-grained 

gneiss consisting of hornblende, plagioclase, quartz, and 

locally, biotite. The common accessory minerals are 

apatite, magnetite, hematite, titanite, and pyrite. The 

following table gives the modes (volume percent) of 

13 samples of the even-grained typical amphibolite: 

SC-6 SC-14 SC-15 SC-16 SC-17 SC-18 SC-21 SC-22 SC-25 SC-32 SC-33 SC-40 S-4 

Hornblende_________ 70 60 40 60 50 50 50 45 20 30 35 50 45 

Plagioclase_ _ _ _ _ _ _ _ _ 11 40- 60 30 30 40 40 50 40 35 20 30 20 

Quartz_____________ 15 Tr. ------- 10 20 10 10 5 8 5 20 15 35 

Biotite------------- 2 _______ ------- ------- ------- ------- ------- Tr. 20 30 25 40 

5 Tr. 

Tr. 

Apatite ____________ ------- Tr. ------- Tr. · ------- Tr. Tr. Tr. 1 Tr. Tr. 

Magnetite__________ 2 ------- ------- ------- Tr. Tr. ------- ------- ------- ------- ------- Hematite ___________ ----------------------------_______ Tr. ------- Tr. ------- Tr. ------- Tr. 

Titanite----------------------------------------_______ Tr. -------------- 1 Tr. ------- Tr. Tr. Pyrite_____________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Tr. _________ - _____ ---- __ -- ______ -- ___ - Tr. 

Epidote------------------------------------------------------------------------.----------------- Tr. 

SC-6: Along South Platte River near Strontia Springs one-half mile west of Kassler 

quadrangle. · SC-14: SEU sec. 34, T. 7 S., R. 69 W. 

SC-15: SEU sec. 34, T. 7 S., R. 69 W. 

SC-16: SEU sec. ~4_, T. 7 S., R. 69 W. 

SC-17: NWUSWn sec. 3, T. 8 S., R. 69 W. 

SC-18: SE~ sec. 34, T. 7 S., R. 69 W. 

In the amphibolite, a rock that has less than the 

average amount of hornblende has more than the average amount of biotite and a rock that is below average 

in plagioclase is rich in quartz. Alternating layers of 

plagioclase and hornblende, not always visible in hand 

specimen, give a rock its foliation, except for rocks 

having a high percentage of biotite; in these rocks the 

orientation of the biotite gives the rock its foliation. 

Hornblen''de in the amphibolite is generally in simple 

prisms but may have sutured borders embayed with 

plagioclase and quartz. Inclusions in the hornblende 

are quartz and opaque iron minerals. Euhedral grains 

of plagioclase are not common in the typical amphibolite, the form of the plagioclase being dependent upon 

that of the surrounding grains of hornblende and 

quartz. An average of 17 percent of the plagioclase 

has been altered to sericite. . The plagioclase and quartz 

have been strained. Titanite was probably altered 

from titaniferous magnetite; two thin sections showed 

grains of titanite grouped around hematite and limonite. Vugs lined with crystals of hornblende, epidote, 

and quartz are common in the amphibolite, especially 

near beds of lime silicate gneiss. One vug in an 

SC-21: SE~ sec. 34, T. 7 8., R. 69 W. 

SC-22: SE~ sec. ~4_, T. 7 S., R. 69 W. 

SC-25: SWUNWn sec. 5, T. 8 S., R. 68 W. 

SC-32: SWUSEU sec. 3, T. 7 S., R. 69 V.'. 

SC-33: SWUSEU sec. 3, T. 7 S., R. 69 W. . SC-40: Russell Ridge west of Bennett Mountain, Platte Canyon quadrangle. 

S-4: NWUSW~ sec. 5, T. 8 S., R. 68 W. 

amphibolite bed in sec. 16, T. 7 8., R. 69 W., along the 

South Platte River contains poorly formed crystals of 

hornblende, magnetite, titanite, scapolite, and albite. 

Varieties of the amphibolite include a strongly foliated type that contains more than 70 percent hornblende in tabular crystals, a porphyroblastic type in 

which amphibolite porphyroblasts constitute about 15 

to 20 percent of the rock, and an augen type in which 

segregations of hornblende crystals amount to about 

50 percent of the rock. 

The strongly foliated variety occurs in small outcrops throughout the area and is gradational with the 

typical amphibolite; it differs principally from the 

typical amphibolite in having, on the average, a higher 

percentage of hornblende, which may in part explain 

its being more strongly foliated. A typical sample of 

this variety (sample S-39 from the NE:l4NW¥.t, sec. 4, 

T. 8 8., R. 69 W.) contained (volume percent) 70 percent hornblende, 11 percent plagioclase, 11 percent 

quartz, 3 percent magnetite, and a trace of apatite. As 

much as 20 percent of the plagioclase is altered to sericite. The hornblende and feldspar crystals are 

oriented subparallel to the plane of schistosity and give 
BEDROCK GEOLOGY 77 

the rock a nematoblastic texture. The foliation is 

the result of alinement of the hornblende crystals and, 

in some specimens, of the biotite crystal&. 

The porphyroblastic variety of amphibolite crops 

out in sec. 3, T. 8 S., R. 69 W., and sec. 34, T. 7 S., R. 

69 ,;v,; it differs from the typical amphibolite principally in containing on the average less hornblende, 10 

to 20 percent, and in having the hornblende concentrated in the porphyroblasts. This concentration gives 

the rock a gray color with black spots. Field data 

were insufficient to determine whether the porphyroblastic variety is a facies of the typical amphibolite or 

a distinct variety. The following table gives the modes 

(volume percent) of two samples of the porphyroblastic amphibolite: 

SC-4 

Hornblende_________________________ 15 

Plagioclase__________________________ 35 

~r~~~~============================= ~g 

S-26 

20 

80 

Tr. 

Tr. A pa ti te _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Tr. 

Magnetite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Tr. _________ _ 

Tr. 

Tr. 

Pyrite _____________________________ - ---------- Diopside or hedenbergite _______________________ _ 

SC-4: NEUNWU soc. 3, T. 8 S., R. 69 W. 

8-20: NEUSWU soc. 3, 'r. 8 S., R. 69 W. 

The texture is porphyroblastic; the crystals of hornblende in the porphyroblasts have a preferred orientation and the crystals of the groundmass are oriented at 

random. The hornblende crystals are as much as 3 

mm long and have a sieve structure and inclusions of 

quartz. As much as 10 percent of the plagioclase is 

altered to sericite. A granulated zone 1 mm wide, which 

contained quartz and sericite as the predominant minerals, was noted in one slide. 

The augen variety of amphibolite occurs where the 

typical amphibolite is adjacent to lime silicate gneiss, 

and probably represents a transitional facies between 

the typical amphibolite and the lime silicate gn·eiss. 

The augen variety differs from the typical amphibolite 

principally because the hornblende is concentrated in 

knots. A typical sample (sample S-35 from the NWlM 

sec. 3, T. 8 S., R. 69 vV.) of the augen variety had a 

mineral composition (volume percent) of 50 percent 

hornblende, 25 percent plagioclase, 25 percent quartz, 

and a trace of titanite. The texture is porphyroblastic; 

hornblende in the porphyroblasts and the groundmass 

shows a preferred alinement. Each porphyroblast, or 

au.gen, is about % inch long, 1M inch wide, ~ to !YJ. 6 inch 

thick. 

LliME SILICATE·GNEISS 

Lime silicate gneiss in this report includes only two 

of the rocks that Ball (Spurr and others, 1908, p. 41) 

included in his lime silicate rocks. These are the 

quartz-epidote-garnet rock and the calcite-lime silicate 

rock. Lime silicate gneiss crops out mostly in the southern part of the quadrangle where beds as Inuch as 8 

feet thick and several hundred feet long were mapped. 

Such large beds are uncommon, but beds that cover only 

a few square yards are common. Most of these smaller 

beds are discontinuous unmappable irregular-shaped 

pods that are abundant in the granite gneiss and migmatite in the southwest corner of the quadrangle. 

The lime silicate gneiss contains many minerals, commonly as well-formed crystals in vugs. The mineralogy 

varies from locality to locality. Fifteen slightly different suites of minerals were found. The more simple 

suites such as garnet-epidote-quartz are common, but 

the complex suites are generally found at only single 

outcrops. These suites (most of which were in beds too 

small to map on plate 2) and the sample locations are 

as follows: 

1. Garnet skarn with limonite. SW:JA,SW:JA, sec. 4, T. 8 S., R. 

69W. 

2. Andradite (determined by X-ray) -epidote-quartz. Many 

localities along road north of Indian Creek ranger station. 

3. Garnet-epidote-hornblende-biotite. SE:JA,NW% sec. 23, T. 

7 S., R. 69W. 

4. Meionite (determined by X-ray) -andradite-epidote-allanitetitanite-apatite-calcite, with later azurite, malachite, 

chrysocolla, chalcopyrite, pyrite, limonite after pyrite. 

NW:JA,NE% sec. 16, T. 7 S., R. 69 W. 

5. Meionite (determined by X-ray) -garnet-epidote-allanitetitanate-apatite-calcite-diopside-hornblende-gahnite. NW 

%NW% sec. 35, T. 7 S., R. 69 W. 

6. Scapolite-garnet-diopside-quartz and scapolite altered to 

blue talc. South Platte Canyon near Strontia Springs 

west of Kassler quadrangle. 

7. Epidote-actinolite-hornblende-serpentine-quartz. SW:JA,NW% 

sec. 3, T. 8 S., R. 69 W. 

8. Diopside-tremolite-quartz-limonite. NW:JA,SW:JA, sec. 15, T. 

7 S., R. 69W. 

9. Vesuvianite\ hornblende-serpentine- orthoclase- quartz. In 

prospect pit in NW:JA,SW% sec. 3, T. 8 S., R. 69 W. 

10. Epidote-scapolite-garnet-magnetite-quartz-calcite and scapolite altered to serpentine. SE:JA,SW% sec. 21, T. 7 S., R. 

69W. 

11. Epidote-diopside-garnet-scapolite-quartz. South Platte Canyon near · Strontia Springs west of Kassler quadrangle. 

12. Tremoli te-muscovite-serpentine-talc-red mineral (kaolinite?) 

with later malachite. NW1MNE1M sec. 21, T. 7· S., R. 69W. 

13. Quartz-pyrite-tremolite, and limonite pseudomorphous after 

pyrite crystals. South Platte Canyon near Strontia 

Springs west of Kassler quadrangle. 

14. Hornblende-orthoclase-qt~artz-chlorite and hornblende altered to diopside, with later chrysocolla, turquoise, smithsonite (botryoidal light green encrustation), malachite, 

azurite, tenorite (black pitchy), conichalcite (radiating 

~lusters of bright green crystals), and limonite. SW% 

NElA,NE:JA, sec. 16, T. 7 S., R. 69 W. 

15. Hornblende-scapolite-titanite-albi.te-magnetite-pyrite. South 

Platte Canyon near Strontia Springs west of Kassler 

quadrangle. 
78 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

Some of the minerals of the lime silicate gneiss are 

the same as the minerals of the surrounding rocks, and 

the rocks that cut the gneiss commonly contain minerals 

derived from it. Lime silicate gneiss interbedded with 

amphibolite contains abundant hornblende; lime silicate gneiss cut by granite gneiss contains abundant potassium feldspar. In pegmatite dikes that cut lime sili- . 

cate gneiss, hornblende commonly takes the place of 

biotite, and hornblende crystals locally line vugs in the 

pegmatites. 

Most of the minerals are in well-formed crystals or 

in large crystalline masses. A description of them 

follows: 

Pyrite : as well-formed crystals one-fourth inch in diameter; 

now partly altered to limonite. 

Quartz: as small crystals in vugs and intcrgrown with feldspar. 

Gahnite (zinc spinel) : rare, as well-formed octahedrons 1 mm. 

in diameter; dark bluish-green, translucent: vitreous faces. 

Calclte : as groundmass around crystals of garnet, diopsidc, 

scapolite and epidote. Where the calcite is dissolved, it leaves 

vugs lined wit!! partly dissolved crystals of the other minerals. 

Diopside: in two forms, as crystals or partly dissolved blebs 

one-fourth inch in length, light green to dark dusky green. 

Occurs as grayish-green to dusky-green crystalline masses, 

except ln. the NWlA,SW% sec. 15, T. 7 S., R. 69 W., where 

diopside .is intergrown with tremolite as large pale-olive 

cleavable masses. 

Tremolite: as grayish-green bladed aggregates partly altered to 

red serpentine, and as granular masses of small pale-green 

crystals. 

Actinolite: as dark greenish-gray bladed aggregates. 

Hornblende: as greenish-black segregations· at many localities; 

locally in sheaflike black crystals 2 inohes in length. 

Garnet: as moderate-brown to grayish-brown well-formed dodecahedral crystals of andradite intergrown w.ith scapolite and 

diopside; slightly dissolved. Also as small masses of black 

schorlomite (determined by X-ray) with crystal faces; schorlomite shows peculiar reticulated etch figures. Probably all 

gradations between nontitan'iferous andradite and titaniferous 

schorlomite are :Present. 

Scapolite: as large columnar masses with prism faces and as 

well-formed prismatic crystals, white or yellowish-gray with 

pearly luster; intergrown with garnet and diopside crystals; 

scapolite commonly coated by epidote, and locally altered to 

serpentine and talc. Determined by X-ray diffraction to be 

the meionite end member. (R. S. Jones, U.S. Geological 

Survey, analyst.) 

Vesuvianite: definitely identified only at one prospect pit in the 

NWlA,SW% sec. 3, T. 8 S., R. 69 W., although not uncommon 

in lime silicate rocks outside the area; occurs as one-fourth 

inch olive-gray prismatic crystals with inner zones consisting 

of yellowish-gray layers alternating with olive-gray layers 

that parallel the crystal faces. 

Epidote: as coating on scapolite and garnet, or as large crystalline masses associated with garnet and surrounded by quartz; 

found rarely a,s small perfectly formed transparent grayish 

olive-green to greenish-black crystals with as many as 10 

forms developed on one crystal. 

Allanite: as thin flat plates· one-half inch long, partly altered to 

a dark reddish-brown metamict mineral; associated wlth 

titanite. 

Titanite : as wedge-shaped dusky-brown crystals ; some crystals 

surrounded by hornblende and epidote ; some partly altered to 

leucoxene. 

Apatite: as perfectly fo·rmed microscopic light-blue prismatic 

crystals surrounded by scapolite, calcite, and quartz. 

Biotite : as yellowish-brown plates with hornblende. 

Muscovite: as clear plates associated with tremolite. 

The order of crystallization of these minerals, as determined from suite 5, on the basis that the early crystals 

are more nearly euhedral than later crystals, apparently 

was: 

1. Allanite 

2. Titanite 

3. Diopside (as crystals) 

4. Garnet (andraditeschorlomite) 

5. Gahnite 

6. Apatite 

7. Scapolite (meionite) 

8. Epidote 

9. Hornblende-tremoliteactinolite 

10. Diopside (massive 

crystalline) 

11. Calcite 

12. Quartz, feldspar 

This sequence is al~ost identical with the crystalloblastic series of Becke (Turner and Verhoogen, 1951, 

p. 510), which in effect implies that allanite has the 

greatest force of crystallization of any of the above 

minerals and develops euhedral crystals regardless of 

its time of crystallization. Similarly, any other mineral in the sequence could have formed before quartz 

and feldspar. 

GRANITIZED METASEDIMENTARY ROCKS 

Granitized metasedimentary rocks include the granite 

gneiss and migmatite, the sillimanite granite gneiss, and 

the hornblende granite gneiss. 

GRANITE GNEISS AND MIGMATITE 

Granite gneiss and migmatite, the most common rock 

unit in the quadrangle, is composed of two rock types 

that are interlayered and gradational into each other. 

One type is migmatite composed of metasedimentary 

rocks, commonly biotite-quartz-plagioclase gneiss in 

layers a few inches to several feet thick with conformable Y2 - to 12-inch-thick layers of leucocratic granite 

(fig. 29). The other type is biotite granite gneiss that 

is strongly foliated but indistinctly layered and does 

not have layers of recognizable metasedimentary rocks. 

Biotite granite gneiss predominates in the l{assler 

quadrangle. 

The granite gneiss and migmatite unit apparently 

is equivalent to the pegmatite, the granite-pegmatite 

and associated granites, and possibly the gneissoid 

granite of Ball (Spurr, and other, 1908, p. 49-51, 60-

67), and to the migmatite and the granite gneiss and 

pegmatite of Harrison and Wells ( 1956, p. 49-53). ·In 

this report the term "granite gneiss" is used in a lithologic sense and is not intended to mean that the rock is 

of igneous origin. 
r 

BEDROCK GEOLOGY 79 

FIGUREJ 29.-Granite gneiss and migmatite along the South Platte River. 

The granite gneiss and migmatite is the most abundant unit of the crystalline rocks; its relation to other 

rocks is well shown throughout the mountainous part 

of the quadrangle. It is well exposed in sees. 16, 21, 

and 28, T. 7 S., R. 69 W. The contacts of the granite 

gneiss and migmatite with the hornblende granite 

gneiss, sillimanite granite gneiss, quartz diorite and 

hornblendite, and the biotite-quartz gneiss are gradational. Contacts with the amphibolite, quartzite, and 

lime silicate gneiss, are sharp. 

Composition of the granite gneiss and migmatite is 

variable. It contains rocks that can be classified as 

alaskite, granodiorite, monzonite, quartz diorite, and 

quartz monzonite. Most of the rock is granitic in 

composition. 

The granite gneiss and migmatite is a pale-red, very 

pale orange, or grayish-orange medium-grained wellfoliated rock composed of quartz, microcline, plagioclase, and biotite; part of the biotite is altered to 

chlorite. The accessory minerals are magnetite, titanite, apatite, limonite, muscovite, and the chlorite 

altered from biotite. 

The following table gives the modes (volume percent) of four samples of the granite gneiss and 

migmatite: 

SC-8 SC-30 S-51 S-59 

Quartz_________________ 55 32 41 40 

Microcline______________ 33 32 17 ___ ___ _ _ Biotite___________ ______ 5 3 9 20 

Plagioclase __ _ _ _ _ _ _ _ _ _ _ _ 7 31 31 40 

Magnetite______ _____ __ _ _ _ _ _ _ _ _ _ Tr. 1 Tr. 

Titanite ___________ __ __ --------· Tr. 1 _______ _ Apatite_ ____ ___________ Tr. Tr. ________ Tr. 

Chlorite __ _____________ Tr. 2 _______ ________ _ Muscovite_______ ______ _______ ________________ _ Tr. 

SC-8: Granite gnei::;s from sec. 28, T. 7 S., R. 69 W . SC-30: Thinly banded quartz monzonite facies from SE}iN W}i sec. 5, T. 8 S., R. 68W. 

S-51: Quartz monzonite facies from SW}iSW}i sec. 4, T. 8 S. , R. 69 W. S-59: Quartz diorite facies from SE}iSW}i sec. 33, T. 7 S., R. 69 W. 
80 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

The texture is shown by tahular crystals of quartz, 

feldspar, and mica oriented subparallel to the schistosity. Most grains are anhedral; feldspar crystals grew 

against biotite crystals; quartz and muscovite are intergrown with both feldspar and biotite; vermicular 

quartz is embayed in microcline. About one-third of 

the biotite is altered to chlorite. Most of the plagioclase 

is oligoclase and is twinned according to the albite law; 

it and part of the microcline are altered to sericite. The 

quartz is strained and fractured. 

Structure of the gneiss is the result of (a) foliation, 

(b) dark beds that are folded in, or (c) intruded granite 

pegmatite. The foliation is the result of biotite alinement. Where stringers and pods of biotite are abundant, the foliation is conspicuous (fig. 29). The biotite 

layers are crenulated, and the biotite flakes are 

stretched along the foliation plane and perpendicular to 

the axes of the crenulations; they produce two lineations, one parallel to the folds and the other perpendicular to the folds. Minor folds can be seen and measured best where dark beds are folded into the gneiss. 

Ptygmatic folds of granite pegmatite that cross the 

foliation are not as common as elsewhere in the Front 

Range, and generally occur only in the more thickly 

foliated gneiss. 

The granite gneiss and miginatite unit contains microfractures that have been healed with later minerals. 

Fractures are filled by epidote, titanite altered to leucoxene, magnetite, and clay minerals. The fractures are 

less than 1 mm thick. and the offset is visible only in thin 

section. As many as five parallel fractures per inch 

may be observed either parallel or perpendicular to the 

foliation. 

A more thinly banded granite gneiss crops out in the 

southeast corner of the quadrangle along J arre and 

Indian Creeks and extends a:bout as far west as the 

Pike National Forest boundary (pl. 2). The biotite 

in this granite gneiss is streaked out in separate layers 

to form the foliation. The gneiss is pale red, medium 

grained, and evenly handed. In a road cut in the 

NW1;4SW1;4 sec. 5, T. 8 S., R. 68 W. (pl. 2), it is isoclinally folded. A mode of this rock (sample SC-30) 

shows it to be quartz monzonite in composition. 

SILLIMANITE GRANITE GNEISS 

Sillimanite granite gneiss, a well-foliated fine:-grained 

grayish-brown rock, crops out principally at the crests 

of folds in the south end of the area (pl. 2). It generally is surrounded by and gradational with sillimanitic biotite-quartz gneiss and granite gneiss and migmatite. The sillimanite granite gneiss is very resistant 

to weathering and forms high ridges above the surrounding rocks. · 

Sillimanite can be easily detected in granite gneiss 

if it makes up 5 percent of the total composition; therefore, those rocks that are of granitic composition and 

contain at least 5 percent sillimanite are mapped· as 

sillimanite granite gneiss. 

The gneiss is a dark-gray well-layered fine-grained 

rock composed of interlocking tabular and acicular 

crystals. Only the sillimanite crystals are euhedral. 

The following table gives the modes (volume percent) 

of two samples of the sillimanite granite gneiss: 

SC-11 

Quartz_____________________________ 10 

Micro cline_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 66 

Biotite ________________ -' _ _ _ _ _ _ _ _ _ _ _ _ 2 

Sillimanite__________________________ 10 

Muscovite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 2 

Magnetite__________________________ 10 

Apatite ______________________ ------- ----------

SC-11 and SC-41: NW~NE~ sec. 3, T. 8 S .• R. 69 W. 

SC-41 

53 

38 

2 

5 

2 

Tr. 

Tr. 

The major minerals are microcline, quartz, sillimanite, and magnetite; the minor minerals . are biotite, 

apatite, and muscovite. The sillimanite, magnetite, 

and mica are restricted to thin, less granitic layers that 

parallel the foliation. · At axes of folds, sillimanite 

crystals are small and densely packed; on the limbs of 

·folds the crystals are larger and more loosely packed. 

Muscovite generally is the matrix for the sillimanite 

crystals. 

The gneiss has a simple planar structure. Sillimanite segregated into layers produces both the foliation 

and lineation. Locally the gneiss is intricately folded 

and the folds are broken by fracture cleavages. 

HORNBLENDE GRANITE GNEISS 

The hornblende granite gneiss crops out in the southern part of the quadrangle in a belt that parallels the 

border of the Pikes Peak granite (pl. 2). The contact 

of the hornblende granite gneiss is sharp with the sillimanite granit~ gneiss, but gradational. with the granite 

gneiss and migroatite and the amphibolite. Quartzite 

bodies with epidote and hornblende are common along 

the borders of the hornblende granite gneiss and the 

gneiss can be traced into beds of amphibolite. 

The hornblende granite gneiss is a grayish orangepink and dark greenish-gray equigranular fine-grained 

well-foliated gneiss that contains quartz, microcline, 
BEDROCK GEOLOGY 81 

biotite, and hornblende. Epidote and hornblende 

masses elongated parallel to the foliation are abundant. 

Some of the hornblende has partly replaced diopside. 

On weathering, the diopside dissolves readily and leaves 

vugs as large as 2 inches long and 1 inch wi.de. 

· In t~in section the rock is xenomorphic granular in 

texture. The major constituents are quartz and microcline; the minor constituents are hornblende, biotite, 

magnetite, muscovite, apatite, epidote, and hematite~ 

Most of the grains are rounded and anhedral; hornblende is in part lathlike and produces a lineation. The 

following table gives the modes (volume percent) of 

three samples of the hornblende granite gneiss: 

SC-1 SC-28 S-2 

60 50 

35 40 

Quartz__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 50 . Microcline ____ .____________ 35 

Biotite___________________ 10 Tr. 5 

Hornblende________________ 5 5 5 

Mu.gnetite________________ Tr. Tr. Tr. 

Muscovite________________ Tr. ---------- ---------- Apatite ___________________________ _ 

Epidote__________________ Tr. 

Hematite _________________ ----------

SC-1: SB~NW~ sec. 3 ..._T. 8 S., R. 69 W. 

S0-28: SE~ sec. 34, T. 7 1::1., R. 69 W. 

S-2: NE~ sec. 1, 'r. 8 S., R. 69 w. 

INTRUSIVE ROCKS 

Tr. _________ _ Tr. _________ _ 

Tr. ~---------

The intrusive rocks include gneissic granite·, qu.artz 

diorite and hornblendite, biotite-muscovite granite, 

Pikes Peak granite, and granite pegmatite. 

GNEISSIC GRANITE 

A few tabular bodies of a rock that is predominantly 

gneissic granite crop out in the west-central part of the 

quadrangle (pl. 2). The granite is similar to the quartz 

monzonite of Ball (Spurr and others, 1908, p. 51), the 

Boulder Creek granite of Lovering and Goddard ( 1950, 

p. 25), and the granodiorite of Harrison and Wells 

(1956, p. 53-54). 

The rock is generally a gray, pink or grayish-brown 

medium-grained gneiss that contains quartz, plagioclase, microcline, and 'biotite. The foliation is· well 

formed except in the center of large bodies where it is 

indistinct. In thin section the rock is xenomorphic 

granular in texture. Porphyroblastic bodies near the 

border of the g11eissic granite are cut by a plitic dikes of 

the biotite-muscovite granite. The porphyroblasts are 

microcline; many of them show carlsbad twinning. 

The following table gives the modes (volume percent) 

of two samples of gneissic granite: 

S-121 

Quartz_____________________________ 35 

Plagioclase__________________________ 5 

Microcline_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 55 

Biotite ____ ... ________________________ 5 

Titanite ____________________________ ----- ____ - Mus co vi te ______ "" _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ________ _ 

S-138 

31 

18 

45 

6 

Tr. 

Tr. 

S-121: SW~SE~ sec. 33, T. 6 S., R. 69 W. 

S-138: Western border of the biotite-muscovite granite in the SW~ sec. 23, T. 7 S., 

R.69W. 

QUARTZ DIORITE AND HORNBLENDITE 

The quartz diorite and hornblendite unit crops out in 

several small areas in the west-central part of the quadrangle and along the South Platte River in the northwest pa_rt of the quadrangle (pl. 2). The unit is much 

like the quartz-bearing diorite and associated hornblendite described by Ball (Spurr, and others, 1908, 

p. 54-57). 

The quartz diorite is locally concordantly interlayered 

with the granite gneiss and migmatite and the metasedimentary rocks and is cut by hornblendite and granite 

pegmatite. Hornblendite dikes as much as 2 feet thick 

cut the quartz diorite at all angles. Ptygmatic veins of 

granite pegmatite cut the quartz diorite and hornblendite. The pegmatite is very coarse grained and 

contains l-inch-long biotite crystals, 2-inch-long feldspar crystals, and bulbous quartz masses as large as 1~ 

feet in diameter. 

The quartz diorite and hornbleridite weathers to more 

rom1ded outcrops than the granite gneiss and migmatite, and on weathered surfaces forms pits about onehalf inch in diameter. 

The quartz diorite occurs in two facies, a massive 

facies and a well-foliated facies. The massive quartz 

diorite is a medium-gray fine-grained xenomorphic 

granular rock consisting principally of complexly 

twinned andesine, hornblende, orthoclase, quartz, and 

biotite. The accessory minerals are apatite, titanite, 

magnetite, and limonite. 

The well-foliated quartz diorite is gneissic, owing to 

segregation of the minerals into mafic-rich and quartzfeldspar-rich layers. It is a black and white coarsegrained rock consisting of andesine, orthoclase, biotite, 

hornblende, and quartz and traces of apatite, titanite, 

and muscovite. 

Hornblendite also has a massive and a well-foliated 

facies. The massive hornblendite is a greenish-black 

medium-grained hypidiomorphic granular rock composed of hornblende, andesine, and quartz with minor 

amounts of biotite, apatite, magnetite, and hematite. 
82 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

The well-foliated hornblendite is gneissic, owing to 

discontinuous layers of plagioclase. It is a black finegrained rock composed of hornblende and andesine with 

traces of biotite, quartz, magnetite, apatite, and hematite. The following table shows the modes (volume 

percent) of seven samples of the quartz diorite and 

hornblendite : 

S-60 S-71 S-40 S-122 S-7 S-52 S-32 

--------1------------------

Quartz___________ 5 12 3 25 10 30 1 

Plagioclase____ _ _ _ _ 50 4 7 11 45 25 30 22 

Orthoclase________ 13 9 16 ____________________ _ 

Biotite___________ 7 16 40 15 Tr. Tr. 2 

Hornblende_______ 25 11 30 15 65 40 · 72 

Titanite __________ Tr. Tr. ____________________ _ 

Apatite___________ Tr. Tr. Tr. Tr. Tr. Tr. 

Muscovite _______________________ Tr. ______________ _ 

Magnetite_____________ 5 ________________ Tr. 3 

Hematite ___________________________________ Tr. Tr. 

Limonite ______________ Tr. ___________ ~---- _________ _ 

S-60: Hornblende-quartz diorite from SE~SE~ sec. 33, T. 7 S., R. 69 W. 

S-71: Fine-grained quartz diorite with microg-(aphic texture from SWXSW~ 

sec. 26, T. 7 S., R. 69 W. 

S-40: Well-foliated biotite-quartz monzonite from SE~SW~ sec. 26, T. 7 S., 

R.69W. 

S-122: Well-foliated hornblende-biotite-quartz diorite from SW~SW~ sec. 16, 

T. 7 S., R. 69 W. 

S-7: Hornblendite from SE~NW~ sec. 5, T. 8 S., R. 68 W. (not mapped). S-52: Hornblendite(?) from NW~SW~SE~ sec. 4, T. 8 S., R. 69 W. 

S-32: Well-foliated hornblendite from NE~SE~ sec. 4, T. 8 S., R. 69 W. 

BIOTITE-MUSCOVITE GRANITE 

The biotite-muscovite granite occurs in a few large 

bodies and many small bodies throughout the quadrangle. Most of the bodies are concordant. The biotite-muscovite granite is nearly undeformed and is 

similar in fabric and mineralogy to the Silver Plume 

granite (Ball, 1906) from the type area at Silver Plume, 

Colo.· 

The granite is well exposed in large bodies on and 

around Carpenter Peak (pl. 2) and in small bodies 

scattered through the area. It crops out as rounded 

knobs as large as 12 feet in diameter that rise above the 

surrounding terrain and project from a mantle of loose 

weathered granite. Crystals of feldspar project from 

the surface of the rugged knobs. 

The contacts with the ·country rock are generally 

sharp, but locally they are transitional zones several 

tens of feet wide .. In the NEljtSW~ sec. 23, T. 7 S., 

R. 69 W. (pl. 2), the biotite-muscovite granite is massive but grades outward toward the border through 

two gneissic zones. The inner zone contains blebs of 

typical granite; the outer zone is cut by pegmatites and 

contains randomly oriented xenoliths of granite gneiss 

from the walls. 

The flow lines in the biotite-muscovite granite are 

generally concordant with the foliation of the country 

rock, but around the border the flow lines in small 

granite apophyses are locally discordant. The relation 

of these small discordant granite apophyses to the 

gneissic granite country rock is well shown in the sw~ 

sec. 23, T. 7 S., R. 69 W. where the granite has a thin 

reaction rim of aplite and it tails out in small pegmatite 

dikes that cut the gneissic granite. 

The granite is pale red and moderate orange pink, and 

weat11ers pale reddish brown, moderate orange pink, 

and pale yellowish brown. It consists principally of 

porphyritic fine-grained granite. The composition 

varies from granite to quartz monzonite to granodiorite 

to quartz diorite. 

The granite contains alined large tabular euhedral 

crystals of microcline that form a flow structure. Most 

of the tabular crystals are one-half ·inch or less in length 

but are as much as 3 inches at an outcrop in the w.y2 

sec. 34, T. 7 S., R. 69 W. (sampleS-54). 

The granite in thin section is seriate porphyritic. 

Needlelike crystals of rutile or some other opaque mineral penetrate the microcline, quartz, and plagioclase. 

Muscovtite and epidote fill cataclastically fractured 

areas in the rock. The following table gives the modes 

(volume percent) of 10 samples of the biotite-muscovite 

granite: 

SC-27 SC-35 SC-36 SC-38 S-1 8-3 S-43 S-47 S-54 S-76 

------1--------------------

Quartz___________ ·24 18 35 22 40 45 30 28 30 40 

Microcline_______ 60 48 45 46 60 45 30 ______ 21 4 

Orthoclase_______ 15 ------ ------ ------ ------ ------ ------ 6 6 9 Plagioclase_______ ______ 23 16 20 10 30 46 31 45 

Biotite___________ 1 6 Tr. 6 Tr. Tr. 4 13 12 Tr. 

Magnetite_____________ 1 Tr. 2 ------ Tr. Tr. 5 Tr. 2 

Apatite ... .,_------ Tr. 1 Tr. Tr. ------ ------ Tr. ------ Tr. ------ Muscovite_______ Tr. 3 3 4 ______ ------ 5 2 ------ ------

¥R~~i~~-~~~==~=== --ri'i-~- ====== Tr~ --Tt-~- ====== --Tt-~- ====== ====== ====== :::::: Chlorite _________ ------------ Tr. ------ ______ Tr. ------ ------ Tr. ------

Limonite ________ ------ ------ ------ ------ ------ ------ ------ Tr. ------ ------ Hornblende ______ ------ ------ ------ ------ ______ ------ 1 ------ ------ ------

SC-27: Granite from SW~ sec. 14 T. 7 S., R. 69 W. 

SC-35: Granite from NW~NW~ sec. 23, T. 7 S., R. 69 W. 

SC-36: Cataclastically deformed granite from NW~NW7;l' sec. 23, T. 7 S., R. 69 W. 

SC-38: Granite from NW7;l'NW~ sec. 23, T. 7 S., R. 69 W. 

S-1: Granite from SW~NW~ sec. 1, T. 8 S., R. 69 W. 

S-3: Granite from SE~ sec. 6, T. 8 S., R. 68 W. 

S-43: Quartz monzonite from NW~NE~ sec. 34, T. 7 S., R. 69 W. 

S-47: Quartz diorite from NEUNE~ sec. 34, T. 7 S., R. 69 W. 

S-54: Quartz monzonite from W7\! sec. 34, T. 7 S., R. 69 W. 

S-76: Granodiorite from NWUNWU sec. 22, T. 7 S., R. 69 W. 

Some outcrops of the granite 'are alaskitic, as shown 

by the modes. Alaskitic granite is more abundant in 

the adjoining Platte Canyon quadrangle where it was 

called gneissic fine-grained granite (Peterson and 

Scott, 1960). The foliation in the granite is caused by 

the orientation of biotite plates. 

Pegmatites and epidote veins are comn1on in the 

alaskitic granite. Small pegmatite clots that are lacking in mica and apparently not connected with discrete 

pegmatite dikes are scattered through the granite. 
~ 

BEDROCK GEOLOGY 83 

Epidote veins and masses 6 inches across are abundant 

in the granite, especially in sees. 14 and 15, T. 7 S., R. 

69 w. (pl. 2). 

Origin.- Harrison and Wells (1956, p. 56) considered 

the biotite-muscovite granite to be of magmatic origin 

because the internal strlJ_cture, which they interpreted 

as flow structure, is parallel to the walls of crosscutting 

bodies and because of the small amount of deformation. The border relation, as noted in the Kassler 

quadrangle, also seems characteristic of magmatic 

rocks. · The granite may have crystallized from intrusive magma, and the transition zone around it probably 

formed by reactions between the magma and its walls. 

The biotite-muscovite granite and the Pikes Peak 

granite are not in contact in the Kassler quadrangle. 

Hutchinson (1959, p. 1622) determined by the argonpotassium method that the ages of the Pikes Peak 

granite and the Doublehead pluton (a correlative of the 

biotite-muscovite granite) are 1,050 and 1,240 million 

years respectively. 

PIKES PEAK GRANITE 

The northeastern border of the Pikes Peak granite 

batholith curves across the southern part of the quadrangle. The granite, which was named by Cross 

(1894a, p. 1), is massive and coarse grained and consists principally of microperthite, quartz, and biotite. 

Figure 30 shows the typical appearance of the granite 

in nearly fresh outcrop. The rounded cubical shape of 

the outcrops is the result of weathering along joints. 

Segregations of biotite and hornblende weather out as 

knobs on the surfaces of the outcrops. 

The granite, at its contact with the metamorphic 

rocks, may be divided into five zones. Where the foliation of the country rock is parallel to the border of the · 

granite, the individual zones are thin, but where the 

foliation is normal to the border of the granite, the 

metamorphic layers apparently provided easier access 

and the zones are wide. The five zones are, from the 

typical granite outward, ( 1) a miarolitic pegmatite 

zone in the typical granite, (2) a metamorphic gneiss 

zone, (3) a porphyritic granite and xenolith zone, ( 4) a 

miarolitic pegmatite zone in the metamorphic rocks, 

and ( 5) typical metamorphic rocks. 

In zone 1, small pegmatite lenses with miarolitic 

cavities are abundant only a few feet inside the border 

of the Pikes Peak granite. In zone 2 a 100-foot wide 

belt of foliated metamorphic rock, generally sillimanitic biotite-quartz gneiss or locally lime silicate gneiss or 

quartzite, concordantly follows the border of the 

granite. The granite between the pegmatites of zone 

1 and the metamorphic rock of zone 2 is highly radio654901 0--63----3 

active because of a greater concentration of allanite and 

cyrtolite; it also contains some xenoliths of metamorphic rocks. Zone 3 contains porphyritic Pikes Peak 

granite of monzonitic or dioritic composition. Xenoliths, which make up about one-third of this zone, are 

extrem;ely migmatized and disoriented. 

FIGURE 30.--Pikes Peak g,ran.ite in nearly fresh o.utcrop at the Noddle 

Heads 3 miles southwest of the Kassler quadrangle. 

Zone 4 contains pegmatites with miarolitic cavities. 

Pegmatites with cavities are typical of the Pikes Peak 

granite, but are unknown in the metamorphic rocks. 

The cavities contain pale-brown microcline crystals as 

large as 6 inches in diameter, clear quartz crystals 6 

inches in length, and, locally, muscovite crystals as 

large as 2 inches in diameter that are perched on the 

microcline and quartz. Muscovite is unknown from 

typical pegmatites of the Pikes Peak granite; therefore 

I think that these pegmatites owe their composition 

partly to contamination from the metamorphic rocks. 

Xenoliths in zone 4 are less migmatized and locally are 

oriented parallel to the regional foliation trend rather 

than parallel to the border of the granite. Some layers 

of metamorphic rock extend into the pegmatite zone. 
84 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

The granite is a homogeneous coarse-grained grayishorange pink rock composed chiefly of microperthite, 

quartz, and biotite. The microperthite is in moderate 

reddish-orange or yellowish-gray grains as large as 1 

inch in diameter, the quartz grains are as large as three 

eighths inch in diameter, and the biotite plates are as 

large as 1 inch in diameter. 

The granite in thin section is hypautomorphic granular to xenomorphic granular in texture, and consists of 

microperthite, quartz, plagiocl~se, and biotite and traces 

of apatite, titanite, magnetite, hematite, chlorite, and 

zircon. Microperthite, much of which is twinned according to the ca.rlsbad <law, and plagioclase (oligoclase) are idiomorphic against quartz. Biotite and 

magnetite are surrounded by microperthite, and 

euhedral biotite lies between the microperthite and 

quartz. The plagioclase appears to have oscillatory 

zoning (alternating calcic and sodic zones) ; the inner 

parts of the plagioclase crystals are vermicular. Part 

of the plagioclase is altered to sericite. Red hematite 

is included in the plagioclase and in f1·actures through 

the granite. Opaque hairlike inclusions (rutile?) 

pierce the quartz and plagioclase. A sheaf of sillimanite crystals was seen in one slide. Zircon is associated with the biotite and may be the variety 

cyrtolite. 

The following table gives the modes (volume percent) of three samples of the Pikes Peak granite: 

SC-47 SC-50 S-49 

Quartz___________________ 24 37 22 

Plagioclase_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 27 9 45 

Microperthite__ _ _ _ _ _ _ _ _ _ _ _ 24 50 _________ _ 

Hornblende_______________ 10 __________ 5' 

Biotite___________________ 12 4 24 

Magnetite________________ 1 Tr. 3 

Muscovite ___________________________________ _ 

Apatite__________________ 1 Tr. 

Titanite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 11 Tr. 

Zircon_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Tr. 

Hematite ___________________________ Tr. 

Chlorite__________________ _ _ _ _ _ _ _ _ _ _ Tr. 

Tr. 

Tr. · 

1 

SC-47: Biotite segregation from Pikes Peak granite along Pine Creek south of the 

quadrangle. SC-50: Typical granite from NWHNE~ sec. 8, T. 8 S., R. 68 W. 

S-49: Quartz diorite from contact zone with metamorphic rocks from the SE~SE~4 

sec. 4, T. 8 S., R. 69 W. 

A deep weathered zone has formed on the Pikes Peak 

granite. At Pine Nook (pl. 2), where several holes were 

angered, the granite is weathered to a depth of more 

than 15 feet. Weathering has affected the biotite grains 

most by loosening them from the quartz and feldspar 

grains. Downward movement of ground water has 

transported the biotite from its disaggregated matrix 

and redeposited it at the water table in a laminated 

band, where it is partly altered to chlorite. Removal 

of the biotite leaves a friable aggregate of quartz and 

feldspar grains. Isolated. boulders of nearly fresh 

granite are distributed at random and protrude fron1 

the surface of the weathered material. 

Origin.-The Pikes Peak granite is of magmatic origin. Several lines of evidence ('Villiams and others, 

1954, p.143-144) lead to this conclusion: (a) microperthite exceeds other feldspars in quantity, (b) only a 

single alkali feldspar is present, (c) plagioclase is complexly twinned in combinations of albite and carlsbad 

twins and, (d) plagioclase shows oscillatory zoning. In 

addition to the above criteria, the characteristics of the 

border of the Pikes Peak granite are more like those 

of a granite of magmatic origin. 

GRANITE PEGMATITE IN PIKES PEAK GRANITE 

Many small pegn1atites that are related to the Pikes 

Peak granite crop out in a narrow zone about 100 feet 

inside the border of the batholith. l\1ost have lenselike 

miarolitic cavities that contain large well-formed crystals of microcline and smoky quartz. Other pegmatites 

contain no cavities but do contain subhedral crystals of 

quartz and feldspar that are tightly bound together. 

The miarolitic pegmatites generally are thin, but long 

and wide, and lie flat. An average-sized pegmatite is 

1 foot wide, 1 foot long, and 2 inches thick. During 

Laramide deformation the cavities were crushed, crystals were broken from the walls, and the cavities were 

filled with limonitic micaceous clay. Smok:y quartz and 

pink microcline are the most common minerals, but 

topaz was found at Pine Nook associated with smoky 

quartz and amazonstone, the green variety of microcline. Octahedral crystals of fluorite were found in 

the SW14 sec. 3, T. 8 S., R. 69 W. 

The pegmatites without cavities are thin and many 

grade into quartz veins. Quartz i.n both the veinlike 

pegmatites and in the quartz veins is milky. These 

pegmatites and quartz veins were emplaced along preexisting fractures and were later fractured and recemented by iron oxide. One of the larger pegmatites, 

about 10 by 20 feet in cross section, in sec. 5, T. 8 S., 

R. 68 ,V., has been prospected by two opencuts. The 

pegmatite contains a discontinuous quartz core, exposed as three quartz pods in the open cuts; the quartz 

is surrounded by moderate reddish-orange potassic 

feldspar. The feldspar and quartz are somewhat iron 

stained and several quartz crystals contain inclusions of 

hematite crystals. 

GRANITE PEGMATITE 

The bodies of granite pegmatite shown on the geologic map (pl. 2) are probably not all of the same age. 

They are tentatively believed to be in part related to 

biotite-muscovite granite, in part to the granite gneiss 

and migmatite, and in part to an unidentified source. 

Quartz-microcline-muscovite pegmatites are the n1ost 
BEDROCK GEOLOGY 85 

abundant; few are more than 3 feet. wide or 10 feet 

long. They contain pink microcline crystals several 

inches in diameter, rnuscovite books locally 8 inches in 

diameter, quartz, and magnetite. Anthophyllite, with 

index of refraction of 1.66, was found in one pegmatite. 

Tourmaline-bearing pegmatites are less common. 

They lie in the southern part of the quadrangle, generally near sillimanite-bearing rocks or biotite-muscovite granite, to which they are related. The tourmaline-bearing pegmatites are 2 to 3 feet wide; they are 

shown on the geologic map (pl. 2). The tourmaline 

crystals are black, 3 to 4 inches long, and a maximum of 

1 inch in diameter. Radiating clusters of tourmaline 

crystals and graphic tourmaline were seen in a pegmatite in the SE% sec. 34, T. 7 S., R. 69 W. Grayish bluegreen apatite was seen in about five of the tourmaline 

pegmatites. The apatite is either in crystals or in crystalline masses as large as 2 inches in diameter. Dark 

reddish-brown garnet, which crystallized earlier than 

both tourmaline and apatite, was seen in one pegmatite. 

In another pegmatite sillimanite surrounds and cuts 

across both toul'lnaline and apatite; hence, it was the 

last mineral to form. 

Beryl was found in a pegmatite that intrudes a lime 

silicate gneiss bed in the NW~4NE% sec. 16, T. 7 S., 

R. 69 ,iV. (shown at a prospect pit on pl. 2). Both the 

lime silicate gneiss and the pegmatite were later invaded by copper-bearing solutions. Microcline crystals 

6 inches in diameter are common in the pegmatite: A 

light bluish-green beryl crystal one-fourth inch in di- . 

ameter and 1 inch in length was found at the contact 

of microcline and quartz. This occurrence of beryl is 

the first known in this area south of the Bigger mine, 

where beryl is abundant in a pegmatite in the metamorphic rocks, or east of the South Platte pegmatite 

district, where beryl has been found in pegmatites in 

the Pikes Peak granite. 

Chrysoberyl was found in the l{assler quadrangle by 

~1aynard Bixby. The locality is listed (Schrader and 

others, 1917, p. 84) as "six miles west of Sedalia; at old · 

mica prospect, with black tourmaline and muscovite, 

and near large garnets." The locality was not found 

but probably is somewhere in sees. 25, 26, 35, or 36 of 

· T. 7 S., R. 69 ,V. Tourmalii1e-bearing pegmatite with 

garnet was found only in the S"T% of sec. 25. 

Where quartz-microcline-muscovite pegmatites cross· 

beds of hornblende granite gneiss, lime silicate gneiss, 

or amphibolit~, they pick up hornblende. Pegmatites 

with hornblende as the ferromagnesian mineral were 

seen in the SE1,4SE% sec. 34, T. 7 S., R. 69 ,V., and 

in the NE%S'V%NE1,4 sec. 4, T. 7 S., R. 69 ,V. (pl. 2). 

Epidote and titanite are locally associated with the 

hornblende. 

PALEOZOIC SEDIMENTARY ROCKS 

Paleozoic sedimentary rocks crop out in a narrow 

belt along the mountain front. In ascending order 

they are the Fountain formation of Pennsylvanian and 

Permian age, the Lyons sandstone of Permian age, and 

the lower part of the Lykins formation of Permian ( ~) 

age. Sandstone dikes crop out along faults in the · 

southern part of the quadrangle; they probably correlate with the Sawatch quartzite and a.re of Late Cambrian age. 

SANDSTONE DIKES 

Northwest-trending dikes of sandstone of Late Cambrian age crop out a.long faults in Stevens and Mill 

Gulches in the west-centraJ part of the area and along 

the valley sides adjoining them (pl. 2, fig. 31). The 

40° 

39° 

EXPLANATION 

Fault, containing sandstone 

dike 

Fault, may contain sandstone 

dikes in places 

0 

105° 

I .._ __ __._ 10 __ _. 20 MILES 

FIGUREJ 31.-Distribution of sandstone dikes in faults. 

N 
86 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

largest and most persistent dike trends northward 

along Bear Creek and Stevens Gulch, then northeastward between Stevens Gulch and Mill Gulch. The 

sandstone forms a small ridge where it is bordered on 

both sides by fault gouge. Elsewhere it forms small 

spurs along the sides of the valleys. The J arre Creek 

fault also contains a sandstone dike in the NvVJ4NE1,4 

sec. 8 and in the SW1,4SE1,4 sec. 5, T. 8 S., R. 68 W. 

Outside the Kassler quadrangle in the Front Range 

the sandstone dikes are known to occur in an area that 

extends from west of Colorado Springs northward to 

Boulder Creek and as far west as Shawnee (fig. 31). 

The northernmost sandstone dike in the Front Range 

is on the west branch of the Rogers dike in the 

W1;2SE14 sec. 3, T. 1 S., R. 72 W., north of Colorado 

Highway 119 and 2.6 miles west of Boulder Falls. The 

westernmost sandstone dikes in the Front Range crop 

out as far west as the intersection of the West Chicago 

Creek road and the road toward Griffith Mountain in 

the SE11.tNE11.t sec. 23, T. 4 S., R. 74 ,V., Georgetown 

quadrangle. 

Sandstone dikes lie in great fault valleys, where the 

thickness of the shattered rock may exceed 300 feet, 

and along small faults where the sandstone occupies the 

full width of the faults. The Bear Creek fault, for 

instance, contains recemented fault gouge on both sides 

of a sandstone dike that in contrast is only slightly 

fractured. On the east side the fault gouge looks like 

vuggy granite pegmatite. Most of the quartz is milky 

and amorphous although occ~sional vugs contain small 

clear quartz crystals. Hematite is abundant in the 

vugs, and the fault gouge is slightly more radioactive 

than background. On the west side, the fault gouge is 

pulverized quartz cemented :by hematite; it contains 

chlorite, serpentine(?), and a purple amorphous mineral (fluorite?). 

The sandstone in the small faults is either extremely 

shattered or not shattered at all, as though some faults 

moved after the emplacement of the sandstone and 

others did not. 

The sandstone dikes are composed of red or green 

fine-grained quartzitic sandstone. The sandstone is 

greenish gray to pale olive to light olive gray, yellowish brown to grayish orange or· pale brown or grayish 

req to pale red. Many outcrops of the sandstone are 

mottled with several colors, sucli as grayish red, moderate yellowish brown, and pale red. 

The sandstone is fine grained, mostly 0.2 to 0.33 mm 

in diameter, with some silt and a few grains larger 

than 5 mm. Most of the grains are rounded to subrounded, but a few are subangular. The borders of 

the grains are ragged, as though they were etched. 

· The following table gives typical modes (volume percent) of total number of grains of the sandstone dikes 

and Sa watch quartzite: 

S-64 S-91 S-101 S-77 

-------------1-----------

Grains: 

Quartz____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 98 99 99 98 

Microcline____________________ 2 Tr. . ______ 2 

Muscovite ______________________________________ Tr. 

Apatite ____________________________ Tr. Tr. 

Rutile(?) ___________________________ Tr. ______ Tr. 

Plagioclase___________________ _ _ _ _ _ _ _ _ _ _ _ _ Tr. _____ _ Magnetite____________________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Tr. 

Biotite ___________________________________ Tr. 

Cementing material: 

Limonite_____________________ xi x Hematite___________________________ x x x Dolomite_______________________________________ x Pore space_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 15 _ _ _ _ _ _ _ _ _ _ _ _ 44 

1 Mineral present. 

S-64: Red sandstone from dike in SWUNEU sec. 4, T. 8 S., R. 69 W. 

S-91: Red sandstone from dike in NEUNEU sec. 16, T. 7 S., R. 69 W. 

S-101: Green sand~tone from dike in NEUNEU sec. 21, T. 7 S., R. 69 W. 

S-77: Sawatch quartzite from Williams Canyon, Manitou Springs, Colo. 

Quartz constitutes 98 to 99 percent of the sandstone; 

microcline, plagioclase, and other minerals constitute as 

much as 2 percent. Needlelike inclusions of apatite 

and rutile are common in the quartz grains. Biotite 

piates are bent between the grains. 

Limonite cements the sandstone so firmly that it has 

the consistence of quartzite and fractures through the 

grains rather than around them. The limonite cement 

has been leached out of spherical spots in the sandstone. 

These spots are 1Js to lj2 inch in diameter and about 1 

inch apart. Loose sa.nd falls out of the centers of some 

spots when the rock is broken. 

The only bedding or alinement in the dikes is parallel 

to the confining walls; no layering was observed that 

would indicate that the sand settled slowly to the bottom of a water-filled crevice. In some dikes the coarse 

grains are alined para.llel to the walls of the fractures. 

Colored bands, produced by ground water, and minor 

fractures also are parallel to the walls of the dikes. Angular fragments of granite and other wall rocks are 

alined along the walls of the sandstone in almost every 

dike. Many of these fragments are as large as 2 to 3 

inches in diameter and all are angular; the angularity 

indicates that the fragments did not move far. 

The dikes are either tabular or lenticular and commonly are less than 1 incli thick, but are quite persistent 

except where faulted. vVhere faulted, the sandstone is 

brecciated, intermixed with the wallrocks, mineralized, 

and lenticular. Thin sections show fractures that extend through the quartz grains and leave finely ground 

quartz in the fractures. Both the microscopic and 

megascopic fractures are healed by silica and hematite. 

SOURCE OF THE SAND 

This discussion of the origin of the sandstone dikes 

deals mainly with two points: (a) the source of the sand 
BE·DROCK GEOLOGY 87 

'l~ABLE 1.-Spect1·ographio analyses of sandstone dikes and Sawatch quartzite 

[Analysts: Paul R. Barnett and Nancy M. Conklin, U.S. Gcol. Survey, Denver, Colo. In this table the following figures only were used: 1, 1.1, 1.2, 1.4, 1.6, 1.8, 2, 2.3, 2.6, 3, 

3.5, 4, 4.5, 5, 6, 7, 8, and 9, with tho necessary decimal point shifts; thus, the reported values should not be considered as being accurate to two significant figures but as bolng grouped into approximately equal geometric subdivisions. Looked for but not detected: Ag, As, Au, Be, Cd, Ge, In, Pt., Sb, Sn, Ta, Th, Tl, U, W, and Zn] 

Sa watch quartzite 

D1324 ••• ·-·····1······10.04610.00301 0.0004210.001910.004410.3810.000110 D 1331. ••••••••• o. 0052 . 062 0 . 0001 . 00063 . 0014 . 34 . 00032 0 1

0. 28 10 1 o 1 o. 000471 o. 00211 o . 0092 . 00090 . 0007 0 . 0029 0 

1

0.008410.0661 0. 001410.002410.000171 0. 018 . 018 . 096 . 0016 . 0019 . 0002 . 046 

Sandstone dikes 

Dl323 •••••••••• .............. 0.098 0 0. 00061 0. 0003 0. 0014 0. 55 0 0 0.084 0. 0028 0 0. 00074 0 0 0 0.042 0. 0004 0 0 0.012 

Dl:l25 •••••••••• ------ . 0088 0 0 . 00038 . 00092 .84 . 0001 0 

)1326 •••••••••• ............. . 0034 0 0 . 00070 . 00032 . 51 . 0002 0 

)1327 •••••••••• ------ .016 0 . 00060 . 0010 . 00041 1.4 . 00034 0 

)1328 •••••••••• ............ .07 0 .0005 . 001 .0008 2 .0004 0 

Dl332 .••••.•••• ------ . 0043 0 0 . 00034 . 00064 . 78 .0002 0 

1333 •••••••••• ------ . 018 0 .0002 . 00057 . 00058 1. 7 . 00063 . 014 

D1324: (S-77, p. 86 In modes). From about 2 feet above base in W11liams Canyon, 

Manitou Springs. Dl331: From 21n. above base In Ute Pass woRt of Manitou Springs. 

Dl323: SE~4SE~4 soc. 33, '1'. 7 S . ..t R. 69 W., KasRler quadrangle. 

Dl325: NE~~NE~4 sec. 16, '1'. 7 b., R. 69 W., Kassler quadrangle. 

DI320: NW~4NE~ ~cc. 21, '1'. 7 S., R. 69 W. Kassler quadrangle. 

Dl327: Groen sandstone from dike 1n NE~fNE~ sec. 21, T. 7 S., R. 69 W., Kassler 

quadrangle. 

and (b) the process by which the sand was emplaced. 

In the past, the sand generally 'vas considered to have 

been derived frmn the Sawatch quartzite. The Sawatch quartzite was favored as the source of the sand 

by Crosby (1895, p. 113-147), Finlay (1916, p. 10), 

ttnd Vitanage ( 1954, p. 500). 

Specirnens of sandstone from the dik~s were compared with the Sa watch quartzite both petrographically 

and chemically. The sandstone from the dikes is texturally and lithologicnJly indistinguishable from the 

Sawatch qua.rtzite. Beds 15 feet above the base of the 

Sawatch most closely resemble the dikes. The cement 

:in the sandstone dikes generally is iron oxide and in 

the Sn,watch quartzite generally is calcite or dolomite. 

The difrerence in cement is not, however, considered to 

be significant because the cement is not an original constituent of the sand. The great difference in pore SP.ace 

between the Sawatch and the sandstone dikes may be 

the result of the different types of emplacement. 

Quantitative spectrographic analyses of two samples 

of Sawatch quartzite and seven sa.mples of sandstone 

dikes, as shown on table 1, show no greater variation 

of minor elements within each rock than between the 

two rocks. Although correlation between the dikes 

ttnd the Sawatch quartzite cannot unequivocally be 

pro~ed, the similarity of the two rocks is remarkable 

and suggests that further analyses or examination for 

microfossils· may eventually confirm the Sawatch 

quartzite to be the source of the sandstone dikes. 

PROCESS OF EMPLACEMENT 

Four hypotheses have been proposed to explain the 

emplacement of the sandstone: (a) injection of w1con-

. 0093 0 0 .0002 0 0 0 .080 . 0004 . 0008 . 00009 . 012 . 0086 0 0 . 00030 0 0 0 .11 . 00064 . 0008 . 00005 . 014 

.046 0 0 . 0015 0 . 00060 .0003 .11 .0022 .0008 . 00006 . 018 

.09 0 .0007 . 001 0 .0007 . 001 .11 . 0012 .0029 . 00035 . 022 . 0083 0 0 0 0 0 0 . 081 . 00078 .0014 .0001 . 014 

.072 0 . 001 . 00050 0 0 .0004 .11 . 00058 .0027 .0002 .022 

Dl328: Green sandstone from dike In SE~SE~ Rec. 21, T. 7 S., R. 71 W., Plne quad- rangle. 

D1332: From Ute Pass fault, North Cheyenne Canyon, Colorado Springs. 

D1333: Green sandstone from dike 1n Ute Pass fault, North Cheyenne Canyon, Colorado Springs. 

soli dated sand into open fissures (Cross, 1894a, p. 3; 

1894b, p. 228; Crosby, 1895, p. 113-147; Vitanage, 1954, 

p. 499) ; (b) dragging of the Sa watch sandstone into the 

fault zones during Laramide faulting (Finlay, 1916, p. 

10); (c) injection of quicksandlike material from the 

sedimentary rocks of the downthrown block of the Ute 

Pass fault into fractures in the upthrown block during 

faulting (Roy, 1946, p. 1226); and 1(d) the possibility 

that the dikes represent unassimilated sandstone beds 

of the Precambrian Idaho Springs formation (D. B. 

Osterwald, in Vitanage, 1954, p. 493). 

The first hypothesis, that is, injection of Wlconsolidated sand into open fissures, is the only one that fits 

the facts already presented. Disagreement on the 

origin has always centered around whether tmconsolidated sand ~vas injected into preexisting fractures or 

whether previously consolidated sandstone was introduced by faulting. The evidence seems conflicting because at one place the sandstone is fractured, at another 

it is unfractured. 

If only one episode of faulting were assumed, the 

presence of both fractured and unfractured sandstone 

would be difficult to explain. Ilow·ever, in Laramide 

time alone, the faults were intruded by igneous dikes, 

faulted once, _and mineralized. They probably were 

disturbed as much or more in Precmnbrian time and 

possibly again in Pennsylvanian time. The presence of 

tmfractured or only slightly fractured sandstone between two thick laye·rs of fault gouge in the Bear Creek 

fault and in the Ute Pass fault at Colorado Springs indicates that the fault gouge was formed before the sandstone was emplaced. 

North west-trending breccia reefs are well known in 
88 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

the northern part of the Front Range, and northwesttrending faults containing sandstone dikes are well 

known in the southern part of the Front Range between 

the South Platte River and Colorado Springs, but their 

relation to each other has not been discussed. Similarities between them are apparent: The trend and the kind 

of movement along them is the same, they both contain 

much limonite and hematite, both are strongly silicified, 

both have chloritized shear zones, both are notahly poor 

in ore minerals, and both cut the sedimentary rocks 

locally. Because of these similarities, I consider the 

breccia reefs of the Front Range mineral belt and the 

northwest-trending faults containing the sandstone 

dikes to be part of the same fault system. 

FOUNTAIN FORMATION 

The Fountain formation (Cross, 1894a) of Pennsylvanian and Permian age crops out in an eastward-dipping belt 1,500 to 3,000 feet wide that extends southeastward from near the northwest corner of the area to sec. 

5, T. 8 S., R. 68 W., in the southeast quarter of the quadrangle, where it is cut off by the J arre Creek fault (pl. 

2) . In general the formation is not well exposed ; the 

sandstone· of which it is composed is poorly cemented 

and forms a valley between the Precambrian rocks on 

the west, which the Fountain formation unconformably 

overlies, and the Lyons sandstone hogback on the east, 

with which it is gradational. Within the valley, however, hogbacks, ridges, and spires composed of more 

resistant sandstone stand conspicuously above the general rolling topography of the valley. The best examples of such features are in the area of Roxborough 

Park in the central part of the belt (fig. 32). Hayden 

(1873, p. 31) considered outcrops of the Fountain formation in this area to he the most picturesque of those 

along the Front Range. 

The contact between the crystalline rocks and the 

Fountain formation is an erosional unconformity. At 

most exposures of the contact, the crystalline rocks show 

no pre-Fountain weathering; in sees. 28, 33, and 34, T. 

6 S., R. 69 W., and sec. 3, T. 7 S., R. 69 ,V., (pl. 2) however, the granite gnei~ is weathered to a depth of about 

30 feet. The weathering consists of the alteration of 

feldspar to kaolin and biotite to chlorite. The minor 

folds in the weathered granite gneiss stand out in sharp 

relief in contrast to the unaltered adjacent granite 

gneiss in which the folds are not nearly so apparent. 

The absence of a relic soil at the base of the Fountain 

and the thinness or absence of a weathered la.yer in most 

of the area indicate considerable pre-Fountain erosion. 

The sediments that resulted from the erosion are deposited in the lower 25 feet of the Fountain formation. 

The Fountain consists of moderate reddish-brown 

arkosic conglomeratic sandstone and minor amounts of 

arkosic conglomerate, siltstone, and dark reddish-brown 

shale. The grains range from pebbles, as much as 6 

inches in diameter, to silt. Most of the sandstone is 

coarse grained. The gravel in the· lower half of the unit 

is coarser than that in the upper half, and conglomerate 

and conglomeratic sandstone are more a.bundant in the 

lower half. Orthoclase feldspar and quartz are the 

predominant minerals. The feldspar grains are fresh 

and only slightly rounded, a.nd the quartz grains are 

angular to subangular. Muscovite, in places as much 

as 1 inch in diameter, is com:rnon throughout the formation. Zircon is the most · abundant heavy mineral; 

there are minor amounts of rutile, tourmaline, epidote, 

sphene, hornblende, ga.rnet, staurolite, and loca.lly 

apatite and clinozoisite. Pebbles in the conglomerate 

and conglomeratic sandstone consist of quartz, quartzite, feldspa-r, granite, gneiss, and schist; the pebbles of 

igneous and metamorphic rocks are restricted principally to the lower half of the formation. 

The sediments of the formation are cemented with 

iron oxide, silica, and carbona.te. Iron oxide is the most 

aJbundant cement; hematite films on the sand grains, 

pink feldspar, and red interstitial argillaceous materia-l 

give the formation its red color. The occurrence of 

resistant beds of the Fountain in the Roxborough Park 

area, as well as in the Garden of the Gods in ·colorado 

Springs, at Perry Park, in Red Rocks near Morrison, 

and in the Flatirons at Boulder, is probably the result 

of a higher content of silica cement; such occurrence apparently is also related to nearby faults or fault zones. 

Carbonate cement occurs only locally. 

The stratification of the Fountain is typical of a formation consisting of stream-channel and minor floodplain deposits. The sandstone beds are very thin to 

thick horizontal or crossbedded units. Channel cut and 

fill structures are common. The lithology of individual 

units changes vertically and horizontally, and there are 

abrupt changes in lithology between units. Discontinuous siltstone and shaly siltstone units, commonly 

green rather than red, occur locally between the sandstone or conglomerate beds or crossbeds. Locally the 

siltstone and shale units reach thicknesses of 50 feet. 

The Fountain formation ranges in thickness from 

about 2,250 feet at the north edge of the quadrangle 

to about 1,150 feet at the south. The change in thickness is gradual throughout the entire distance and is 

probably the result of a strike fault which cuts out some 

of the beds (fig. 32), The relief of the Preca.mbrian surface on which this formation was deposited, at least in 

this small area, is not. the cause of the wide range in 

thickness. The contact of the Fountain formation with 

the Precambrian is not well exposed, but where ex-
BEDROCK GEOLOGY 89 

FIGURE 32.-Thinning of the Fountain formation to the south by faulting. Note how individual beds ap·proach the mountain front as they 

are traced to the south. Thinning is caused by strike fault. 

posed, and where inferred for mapping, the contact indicates a Precambrian relief of only 1 to 2 feet. PostFountain erosion does not explain the range in thickness. At the top of the Fountain formation an interval 

of about 45 feet of interfingering beds of Fountain- and 

Lyons-type sandstone indicates a gradual change from 

conditions of sedimentation of the Fountain formation 

to those of the Lyons sandstone. 

I found no fossils, nor have any been previously reported from the Fountain formation in the Kassler 

quadrangle. The Pennsylvanian and Permian age of 

the Fountain formation is based on Permian fossils 

(Maughan and Wilson, 1960) in the Ingleside formation, with which the Fountain intertongues in northern 

Colorado, and on the Pennsylvanian fossils in the Glen 

Eyrie shale member of the Fountain formation in the 

Colorado Springs area (pl. 3). 

LYONS SANDSTONE 

The Lyons sandstone (Fenneman, 1905) of Permian 

age overlies the Fountain formation and east of the 

mountains forms a continuous hogback that dips about 

60° NE. The formation is well exposed throughout 

the quadrangle. It consists of yellowish-gray to palered massive fine-grained crossbedded quartzose friable 
. , 

90 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

sandstone about 235 feet thick that contains some lenticular layers of channel conglomerate near the base. A 

bed of conglomerate and coarse-grained sandstone that 

contains large flakes of muscovite marks the top of the 

formation. The sandstone is composed almost exclusively of clean well-sorted well-rounded quartz 

grains. Stratigraphic section 1 is typical of the 

formation. 

The cementing material is predominantly limonite 

and calcium carbonate. Limonite also fills fractures 

and forms concretions. Some of these concretions are 

large and hollow, others are small accretions one-eighth 

inch in diameter that resemble fish eggs. 

Crossbedding in the Lyons suggests an eolian origin. 

The Permian age is based on its correlation with the 

Satanka shale of Permian age in Wyoming (Mat~ghan 

and Wilson, 1960) and its correlation with the Cedar 

Hills sandstone of l(ansas (Maher, 1953). 

1. Lyons sandstone in the NE34NWJ4SEJ4 sec. ~7, T. 6 S., R. 

69 W. 

Lyons sandstone : Feet 

4. Sandstone, yellowish-gray, with pink stains ; thinbedded, crossbedded, medium-grained; pebbles 

as much as 1 inch in diameter; some arkose 

·beds----------------------------------------- 81.4 

3. Sandstone, white, massive, friable, fine-grained__ 18. 5 

2. Sandstone, reddish-brown, pink and yellowishgray, massive, crossbedded, fine-grained, medium 

hard to soft; conglomerate lenses_____________ 90. 9 

1. Sandstone and conglomerate, arkosic, coarsegrained. (Lower transitional part of Lyons 

sandstone)---------------------------------- 44.5 

Thickness of Lyons sandstone ______________ 235. 3 

LYKINS FORMATION 

The Lykins formation (Fenneman, 1905) of Permian ( ~ ) and Triassic ( ~) age lies in a valley between 

the Lyons sandstone hogback on the west and the hogback on the east composed of the Lytle and South Platte 

formations (pl. 2, fig. 32). The formation conformably 

overlies the Lyons sandstone. It has a northeast dip of 

about 60° except in the southern part of the quadrangle, 

where it is overturned to the east by a thrust fault. It 

contains in ascending order the following- members as 

described by LeRoy (1946, p. 31): the Harriman shale, 

the Falcon limestone, the Bergen shale, the Glennon 

limestone, and the Strain shale. Stratigraphic sections 

2, 3, and 4 illustrate the lithology of the members. 

The Harriman shale member of LeRoy is a moderate reddish-brown thin-bedded silty shale about 70 feet 

thick. Locally a moderate reddish-brown sandy limestone crops out a few feet above the Lyons sandstone. 

The Falcon limestone member of LeRoy is a yellowish-gray massive or thinly laminated, porous limestone 

2 feet thick. 

The Bergen shale member of LeRoy is a moderate 

reddish-brown thin-bedded silty shale about 40 feet 

thick. The Bergen shale and the Harriman shale are 

mapped as Harriman and Bergen shale members. 

2. Lykins formation in NE%NE114, sec. 31, T. 7 S., R. 68 W. 

Lykins formation (part) : 

Strain shale member of LeRoy : Red shale, mostly 

covered. 

Glennon limestone member of LeRoy : 

4. Limestone, grayish orange-pink, finely lamiFeet 

nated, fine-grained; wavy bedding, shaly to 

platy; upper par.t porous__________________ 12. 0 

3. Limestone, pinkish-gray, massive, laminated__ 2. 8 

Thickness of Glennon limestone member_____ 14. 8 

Harriman and Bergen shale members of LeRoy 

(part) : 

2. Shale, modera•te reddis.h-brown, blocky, silty__ 33. 0 

1. Limestone, yellowish-gray, massive, laminated ; (Falcon limestone member of 

LeRoy)--------------------------------- 2.5 

Measured thickness of Harriman and Bergen 

shale members-------------------------- 35.5 

Covered; moderate reddish-brown shale, down to Lyons 

sandstone. 

3. Lykins formation in SE%SE% sec. 11, T. 7 S., R. 69 W. 

Lykins formation (part) : 

Covered, red shale. 

Glennon limestone member of LeRoy: Feet 

4. Limestone, pale-red, thinly laminated; appears 

to be one-half sand, shaly, wavy bedded____ 12. 0 

3. Limestone, white, wavy-bedded; contains 

chert nodules as much as 1 in. in diameter------------------------------------- 3.3 

Thickness of Glennon limestone member---- 15. 3 

Harriman and Bergen shale members of LeRoy 

(part) : 

2. Shale, red, silty, thin-bedded______________ 40. 0 

1. Limestone, white; contains black manganese 

dendrites ; friable to floury, thin-bedded~ 

(Falcon limestone member of LeRoy)------ 2. 0 

Measured thickness of Harriman and 

Bergen shale members--------------- 42. 0 

Covered down to Lyons sandstone. 

4. Lykins formation in the NE%NW%SEJ4 sec. ~7, T. 6 S., 

R. 69 W. 

Lykins formation : 

Strain shale member of LeRoy : Feet 

7. Covered -------.---------------------------- 165. 0 

6. Sandstone, gray, crossbedded, limy ; weathers 

orangegraY------------------------------- 1.5 

5. Shale, orange-red, clayey------------------- 86. 0 

Thickness of Strain shale member _______ 252. 5 

Glennon limestone member of LeRoy : 

4. Limestone,· grayish-orange to pink; wavy 

bedding surfaces; sandy__________________ 17. 0 
BEDROCK GEOLOGY 91 

4. Lyk,ins tornwtion in the NElA,NWlA,SElA, seo. 2?', T. 6 S., 

R. 69 W.-Oontinued 

Lyldns formation-Continued 

Harriman and Bergen shale members of LeRoy : Feet 

3. Covered; probably reddish-brown shale______ 43. 0 

2. Limestone, gray, massive, thinly stratified; 

(]l'nlcon limestone member of LeRoy)----- 2. 4 

1. Covered; probably reddish-brown shale.______ 71. 8 

~rhiclmess of Harriman and Bergen shale 

members ------------------------------ 117. 2 

~rhiclmess of Lykins formation---------- 386. 7 

The Glennon limestone member of LeRoy is an excellent marker; it is exposed in a small hogback almost 

continuously along the Front Range. The limestone 

consists of 15 to 17 feet of grayish orange-pi~1k, moderate yellowish-brown, and yellowish-gray thin-bedded 

sandy layers that are finely laminated, wavy, intricately 

folded, a.nd faulted or slightly brecciated. Pale-red 

chert nodules and granular quartzose layers with small 

vugs of qu~trtz crystnJs were found in the middle of the 

limestone. Some of the quartz grains show crystal faces 

and indicate that part of the quartz was formed in place 

and was not transported from older sedimentary rocks. 

The chert nodules are rimmed by crystalline calcite. 

The lamination of some of the limestone consists of 

htyers of calcite crystals. 

The Strain shale member of LeRoy is moderate reddish-brown silty shale about 250 feet thick interbedded 

with some thin ]ayers of light-green shale and some 

layers of grayish-orange massive, loosely cemented, 

cross bedded sandstone. 

The age of the Lykins formation is based on its correlation "·.it:h the Satanka, Forelle, and Chugwater formations of "'yoming C~1aughan and 'Vilson, 1960) (see 

also pl. 3). 

At the top of the Lykins there is a soft earthy sandstone about 5 feet thick. The sandstone is reddish 

brown and contains sand grains of two sizes; the larger 

grains range from 0.33 to 1.5 mm in diameter and the 

smaller grains average less than 0.1 mm in diameter. 

The grains are mostly quartz; the larger ones are frosted 

and well rounded and the smaller ones are angular. 

Silt is a minor constituent. The grains are loosely held 

together by calcium carbonate. The frosted grains indicate that the sandstone probably is of eolian origin. 

T'his sandstone strongly resembles and may be correlative with the Entrada sandstone of Gilluly a.nd Reeside 

(1D28, p. 76-78). 

MESOZOIC AND CENOZOIC SEDIMENTARY ROCKS 

l\1esozoic rocks include, in addition to the upper 

Triassic ( ~) part of the Lykins formation, the Ralston 

654901 0--63----4 

Creek, Morrison, and Lytle and South Platte formations, the Graneros shale, Greenhorn limestone, Carlile 

shale, Niobrara formation, Pierre shale, Fox Hills sandstone, Laramie formation, and the lower part of the 

Dawson arkose. The upper part of the Dawson arkose 

is of Cenozoic age. 

RALSTON CREEK FORMATION 

The name Ralston Creek formation of Late Jurassic 

age was adapted from LeRoy (1946, p. 46-55) by Van 

Horn (1957, p. 755-756) and is used for the series of 

limestones and shales between the Lykins formation and 

the :Morrison formation (see stratigraphic sees. 5, 6, and 

7). Despite the probable IGmmeridginn (Morrison) 

age of these beds, their thinness ( 45 feet or less locally) , 

and their lithologic similarity to parts of the Morrison 

formation, differentiation from the Morrison formation 

is justified because these rocks are n1ore easily recognized and are more persistent than adjacent rocks in 

the Lykins or Mo.rrison formation. A jasper horizon 

is a particularly persistent surface and subsurface 

marker bed in Colorado, New Mexico, Utah, and Arizona. 

The lower boundary of the formation is at the top 

of the earthy light-brown Entrnda( ~) sandstone equivalent, or where the Entrada ( ~) is absent, at the top of 

the moderate-brown siltstone or grayish yellowish-green 

shale of the Lykins formation. The upper boundary is 

at the base of the lowest, most persistent sandstone of 

the l\1orrison formation or at the top of the uppermost 

algae and jasper-bearing limestone of the Ralston Creek. 

The Ralston Creek formation contains either a freshwater limestone facies or a gypsum facies along the 

Front Range. Limestone beds crop out between Ralston and Bear Creeks (fig. 28) and between Deer Creek 

and J arre Creek. Gypsum beds crop out between Bear 

Creek and Deer Creek and at Perry Park. Limestone 

beds have been seen in the gypsmn facies but gypsum 

was not observed in the limestone facies. 

5. Ralston 01·eelc to1·mation in gully no1·th ot Kassler schoolhouse, SWIA,SE% sec. 2"1, T. 6 S., R. 69 W. 

Ralston Creek formation (part) : Feet 

28. Shale, olive-gray, silty; weathers to pinkish-gray 

flakes and pinkish-gray limy nodules________ 0. 4 

27. Shale, pale-brown, silty; weathers to pink flakes_ . 1 

26. Shale, light olive-gray, silty, calcareous; weathers to pinkish-gray flakes------------------- 1. 6 

25. Limestone, yellowish-gray, nodular, silty; finely 

crystalline; contains charophytes____________ . 7 

24. Shale, light olive-gray, silty, calcareous; weathers 

to pinkish-gray fla]{eS------------------------ 4. 0 

23. Limestone, light olive-gray, massive, finely crystalline; contains charophytes_______________ . 4 

22. Shale, light olive-gray; silty, calcareous; 

\Veathers pinkish gray _______________________ 1.1? 
92 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO. 

5. Ralston Creek formation in gully north of Kassler schoolhouse, SW~SE~ sec. 2"1, T; 6 S., R. 69 W.-C'ontinued 

Ralston Creek formation (part)-Continued Feet 

21. Limestone, olive-gray, massive; contains lenticular nodules of grayish-brown jasper as 

much as 6 in. in length and 2 in. in thickness. 

Contains algae (Echinochara spinosa) and 

gastropods ( Gyraulus veternus a;nd Lymnaea 

morrisonensis) . Gastropods replaced by quartz 

and jasper__________________________________ .9 

20. Shale, light olive-gray; weathers to light-gray 

flakes; silty, calcareous--------------------- 2. 0 

19. Limestone, yellowish-gray ; weathers nodular ; 

contains charophytes------------------------ .2 

18. Shale, yellowish-gray, chalky ; weathers nodular________________________________________ 1.1 

17. Shale, light olive-gray, silty------------------- . 5 

16. Limestone, yellowish-gray, nodular, chalky; contains charophytes___________________________ .6 

15. Limestone, yellowish-gray, massive, finely crystalline; weathers nodular ; shows calcite 

cleavages; contains charophytes_____________ 1.6 

14. Shale, pale-olive; silty, calcareous, weathers pale 

greenish yellow ; partly covered ; lower part 

~as thin sandstone layers and grayish-brQwn 

shale_______________________________________ 8.0 

13. Sandstone, yellowish-gray; massive, slightly calcareous, platy; weathers pale yellowish 

brO\Vn------------------------------------- .4 

12. Shale, pale-olive and grayish-brown variegated; 

platy to fissile, silty; has 0.5 to 1-in. layers of 

pale-olive sandstone_________________________ 1. 8 

11. Limestone, very light gray, blocky, silty; weathers platy; contains charophytes_____________ .4 

10. Shale, pale-olive, silty, calcareous; thin limonitestained beds-------------------------------- 4.1 

9. Sandstone, yellowish-gray, laminated, finegrained; weathers platy____________________ .4 

8. Shale, pale-olive, silty, calcareous______________ 1. 4 

7. Shale, grayish-brown, silty, calcareous_________ . 8 

6. Shale, pale-olive, silty, calcareous______________ 2. 0 

5. Shale, grayish-bro,vn to pale-olive mottled; 

sandy------------------------------------- 1.9 

4. Sandstone, pale-olive, loose, fine-grained; grades 

downward into silty shale__________________ 1. 6 

3. Shale, grayish-brown to pale-olive mottled, silty 

at top; pale-olive to grayish-brown mottled, 

sandy at bottoJn___________________________ 6.0 

2. Sandstone, grayish-orange, friable to loose, finegrained------------------------------------ 1.3 

1. Shale, grayish orange-pink mottled with pinkish 

gray; silty, calcareous_____________________ 2. 0 

Measured thickness of Ralston Creek formation__ 47. 3 

Qovered. Lykins formation only a few feet below bottom of 

section. 

6. Ralston C'reek formation in the NE~NWJ4SE~ sec. 2"1, T. 

6 S., R. 69 W. 

Ralston Creek formation (part) : Feet 

18. Covered; probably shale______________________ 7. 8 

17. Limestone, gray ; contains algae and some red 

jasper-------------------------------------- .7 

16. Covered; probably shale______________________ 3. 4 

6. Ralston Creek formation 'in the NE~NW~SE~ sec. 2"1, '1'. 

6 S., R. 69 W.-Continued 

Ralston Creek formation (part)-Oontinued Feet 

15. Limestone, gray, fine-grained; contains clots of 

red jasper__________________________________ 1.7 

14. Shale, gray-brown, silty------------------'----- 30. 8 

13. Shale, olive-gray, blocky, clayey------~-------- 12. 0 

12. Limestone, gray, dense; contains jasper nodules; 

almost solid jasper in places________________ . 6 

Measured thiclmess of Ralston Creek formation__ 57. 0 

7. Ralston Creek fo?·nwtion in the SW~NW~ .<tee. 30, T. 7 

S., R. 68 W. 

Morrison formation : Covered. 

Ralston Creek formation (part) : Feet 

3. Limestone, light-gray, massive, sandy---------- 1. 0 

2. Shale, light-gray, blocky, limy----------------- 12. 0 

1. Limestone, light-gray, dense, hard ; contains algae 1. 0 

Measured thickness of Ralston Creek formation__ 14. 0 

Covered. 

The formation is about 48 feet thick and consists of 

a series of yellowish-gray dense ridge-forming limestone beds separated by silty calcareous shale in the 

upper part, and thin, fine-grained sandstone beds separated by silty or sandy shale in the lower part. The 

limestone contains nodules of black to red jasper as 

much as 4 inches in diameter. In the northern part 

of the quadrangle some beds are composed almost entirely of small pellets and streaks of jasper. Sections 

5-7 illustrate the typical lithology. 

Limestone beds,in the SW1,4SE1,4 sec. 27, T. 6 S., R. 

69 W., contain fresh-water gastropods identified by J. 

B. Reeside as Gyraulus veternu,s Meek and Hayden and 

Lymnaea morri.rwnensis Yen, and algae identified by 

R. E. Peck as Echinochara spinosa Peck of IGmmeridgian age (plate 3). These fossils are clustered around 

the outside of jasper nodules in the limestone along 

with silicified internal fillings of ostracodes. Although 

calcite also has replaced the fossils, calcite casts are 

seldom seen and are almost impossible to extract from 

the matrix, whereas jasper casts can be leached out in 

excellent condition. 

Gypsum in the formation indicates that it was deposited in a lagoon near the sea. 

The Ralston Creek formation is equivalent to the 

Summerville formation of the San Rafael group 

(Mcl(ee, and others, 1956, p. 5). Its stratigraphic position is the same; it lies above the Entrada ( ? ) sandstone and below the Morrison formation. Both the 

Ralston Creek and the Summerville contain gypsum 

and chalcedony ( Gilluly and Reeside, 1928, p. 80). 

MORRISON FORMATION 

The Morrison formation (Emmons and others, 1896) 

of Late Jurassic age crops out on the west slope of the 
BEDROCK GEOLOGY 93 

ridge formed by the Lytle a.nd South Pla.tte formations. 

The formation is about 320 to 380 feet thick and consists of n. lower thin sandstone unit and an upper thick 

claystone and siltstone unit (see stratigraphic sections 

8-10). 

The lower 45-foot sandstone unit of the formation 

mn.y be equivnJent to the Sn.lt 'Vash member of Lupton 

(1914, p. 127). It conta.ins as many as four lenticular 

ridge-forming sandstone beds that are massive to thick 

bedded, crossbedded, and .fine to medium grained, and 

are cemented by calcium c~wbonate. They are yellowish gray except for the basal, most persistent sandstone 

which is gray, medium grained, cnJcareous, and crossbedded, and locally conta..ins grains of jasper from the 

underlying. Ra.lston Creek formation. The sandstone 

beds weather light brown, orange pink, or olive gray, 

and are pitted; the crossbedding stands out in relief. 

At the base of most of the sandstone beds is a basal conglomerate made up of chips of limestone, shale, and 

grains of jasper from the underlying Ralston Creek 

formation. The sa.ndstone beds are separated by 

grn.yish-red, reddish-brown, or greenish yellmvish-gray 

blocky calcareous siltstone. Section 8 is typical of the 

sandstone unit. 

The basal contact of the ~1on·ison formation is at the 

base of the lowest persistent sandstone, generally 8 to 

11 feet above the top limestone in the Ralston Creek 

:formation. The upper contact of the lower sandstone 

unit is at the top of the uppermost yellowish-gray 

crossbedded calcareous sandstone that has a. basal conglomerate of shale chips-generally about 45 feet above 

the base of the l\1orrison formation. 

8. Jllon·ison to·rmation ·in the Nl.!J%NW%SW% see. 27, T. 6 S., 

)l. 69 w. 

Morrison formation (part) :Lower sandstone unit: Feet 

22. Shale, olive-grny nnd grny-bro\vn variegated, 

siltY---------------------------------------- 8.0 

21. Sandstone, grhy, massive, fine-grained, soft, limy; 

weathers platy______________________________ 1. 0 

20. Shale, gray and pin]{, also olive-green and graybrown; silty, partly coveretL_~--------------- 11. 3 

19. Sandstone, gray, massive, medium-grained, limy·; 

hns salt-nnd-pepper appenrnnce and contains 

gt·nins of red jasper_________________________ 1. 0 

'J.'hiclmess of lower sandstone uniL----~---------- 21. 3 

Above the lower lenticular sandstone unit is n .. unit of 

variegated siltstone and cla.ystone with thin limestone 

and sandstone beds that may be equivalent to the 

Brushy Basin member of Gregory ( 1938, p. 59). Sections 9 n.nd 10 nre typical of this upper unit. It is div.ided into three parts: a. lower red n.nd gray siltstone, 

a middle yellow.ish-gra.y claystone, and an upper red 

claystone. The lower rart consists of gray and reddishbrown sjJtstone beds that locally contain thin crystalline limestone layers and yellowish-gray quartzitic lenticular sandstone beds. This lower unit of red and gray 

siltstone is generally about 45 :feet thick. 

The middle, or most characteristic, part of the Morrison is light- to yellowish-gray siltstone and claystone 

about 165 :feet thick that contains light-gray or gray 

massive hard crystalline limestone and algae and freshwater mollusks, and yellowish-g"ray medium-grained 

sandstone with limy cement. Dinosaur bone fragments 

were found in a, dusky yellowish-green shale or claystone 125 to 150 feet below the base of the Lytle 

formation. 

The upper part is dominantly red variegated silty 

claystone, but loca.lly contains many beds of reddishbrown or yellowish-gray fine- or 1nedium-grained sandstone. At severaJ places a conglomerate bed containing 

quartzite and chert pebbles was seen at the base of this 

unit. The conglomerate beds grade laterally into sand-. 

stone and then into shale. The thickness of the dominantly red claystone unit is about 60 feet. 

9. lllon··ison to1·mat-ion on slope ot hogback in NE%NE% see. 31, 

T. 7 S., R. 68 W. 

Morrison formation: 

Red claystone unit: Feet 

12. Covered--------------------------------- 70.0:t 

Yellowish-gray claystone unit:· 

11. Shale, light olive-gray, blocky, clayey, 

slig.htly leached------------------------ 27. 0 

10. Limestone, yellowish-gray, fine-grained; no 

fossils--------------------------------- 0.8 

9. Shale, dusky yellowish-green; blocky, 

clayey, calcareous; weathers light greenish graY------------------------------- 27.0 

8. Siltstone, dusky-yellow, sandy_____________ . 3 

7. Shale, dusky yellowish-green, blocky, silty; 

dinosaur bone fragment in float_ ________ 27. 0 

6. Sandstone, yellowish-gray, massive, stratified, medium-grained, friable; upper 1 ft 

:and lower 1ft. more resistant than middle 4. 0 

5. Shale, gray'ish yellow-green; clayey; 

weathers yellowish gray; breaks out in 

small chiPS---------------------------- 36.0 

4. Shale, grayish-red ; blocky, clayey ; weathers. 

pale red _______________________________ 42.0 

Red and gray siltstone unit: 

3. Shale, grayish-red; weathers pale red; 

blocky, silty---------------------------- 51. 0 

2. Shale, dusky yellowish-green, blocky, silty __ 57. 0 

1. Covered down to limestone in Ralston Creek 

formation. Appears to be alternation of 

colored shale of beds 2 and 3 for rema'inder 

of covered intervaL ____________________ 40. 0 

Thickness of Morrison formation (rounded) ____ 382. 0 
94 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

10. Morrison formation in quarry in NW:l4SW:J4 sec. 35, T. 6 S., 

R. 69 W. 

Lytle formation. 

Morrison formation (upper part) : 

·· Red claystone un:it : Feet 

18. Covered--------------------------------- 40.0:t 

17. Shale, reddish-brown; sandy______________ 7. 0 

16. Sandstone, rusty brown ; medium grained ; 

weathers brown_______________________ 6. 0 

15. Shale, reddish-brown; sandy __ :______ _____ 2. 0 

14. Sandstone, reddish-brown, medium-grained_ 3. 0 

13. Shale, reddish-brown; a sandy silL________ 3. 0 

Yellowish-gray claystone unit (part) : 

Covered. 

12. Shale, gray ; stained reddish . brown from 

overlying shale; nodular, calcareous_____ 3. 1 

11. Sandstone, tan and gray ; fine grained ; 

weathers pink__________________________ 2. 0 

10. Shale, reddish-brown, silty---------------- 6. 0 

9. Shale, olive-drab and green, silty--------- . 8 

8. Sandstone, tan-gray; fine grained; weathers 

tan gray-tan mottled___________________ 2. 1 

7. Shale, reddish-brown and pink, silty------- 1. 0 

6. Sandstone, lightl-gray; weathers maroon; 

medium grained------------------------ 5.5 

5. Shale, olive-drab, silty-------------------- . 6 

4. Shale, reddish-brown, silty---------------- 3. 1 

3. Shale, green; weathers light green_________ 1. 2 

2. Sandstone, tan-gray mottled______________ . 4 

1. Shale, light-olive, blocky, limonite-stained__ 8. 0 

Measured thickness of Morrison formation_.,_ _____ 94. 8 

LYTLE AND SOUTH PLATTE FORMATIONS 

The Lytle and South Platte formations form the most 

prominent hogback in the quadrangle (fig. 32) . They 

are about 320 feet thick in the northern part of the-quadrangle but are faulted out in the southern part (pl. 2) . 

Waage ( 1955, p. 46) subdivided the Dakota group, in 

ascending order, into the Lytle formation and the South 

Platte formation and described ( 1955, p. 34-35) an 

excellent section of the two formations. The type 

locality of the South Platte formation is at the north 

boundary of the quadrangle. 

The Lytle formation (Finlay, 1916) of Early Cretaceous age consists of aibout 40 feet of yellowish -gray 

conglomeratic sandstone that contains pebbles of quartz, 

chert, and quartzite and logs of agatized wood; locally 

it consists of medium-grained sandstone with lenses of 

variegated claystone. A widespread disconformity 

separates the. Lytle formation from the South Platte 

formation. 

The South Platte formation (Waage, 1955) of Early 

Cretaceous age is subdivided into the Plainview sandstone member (56 feet), an unnamed shaly unit ( 64 

feet), the l(assler sandstone member ( 72 feet), the 

Van Bibber shale member (20 feet), and an unnamed 

sanqstone unit at the top (85 feet) (vVaage, 1955, p. 

46). The Plainview sandstone member contains thick 

beds of light-gray and yellowish-gray fine-grained 

crossbedded sandstone with gray clayey siltstone beds 

and partings. The unnamed middle shaly member is 

primarily gray and brown siltstone and fine-grained 

sandstone. Near the top it contains dark-gray silty 

shale with som.e marine fossils. Waage ( 1955, p. 41) 

identified I noceran1/U8 bellvuensis Reeside, I nocerawus 

comancheanus Cragin, and Pteria salinensis White from 

this shale. In addition, a mold of an echinoid was 

found in float from the shale in the SW%NW1;{a, sec. 35, 

T. 6 S., R. 69 W. (pl. 2, loc. 2). The Kassler sandstone 

member, whose type locality is at the north end of the 

·quadrangle, consists of thick beds of yellowish-gray 

fine- to coarse-grained cross-laminated friable sandstone 

that contains clay pellets and has a chert and quartzite 

pebble conglomerate at the base. The Van Bibber shale 

member contains ~s many as five minahle refractory 

clay beds interspersed with thin yellowish-gray sandstone beds. The clay is finely laminated and, where 

fresh, is medium gray to medium dark gray; where 

weathered, it is white. The unnamed sandstone unit at 

the top of the South Platte formation contains at its 

base a 45-foot thick light-gray, tabular to massive, fineto medium-grained, crossbedded sandstone that contains 

scattered clay pellets. This sandstone is quarried for 

silica sand. Crossbedded sandstone from the same 

horizon in the southern part of the area was used for 

dimension stone, a purpose for which it is especially 

adapted because of its hardness and well-formed system. 

of joints. Above this unit are thin gray soft finegrained sandstone beds interlayered with thin beds of 

clayey siltstone and porcellanite. 

GRANEROS SHALE, GREENHORN LIMESTONE, AND 

CARLILE SHALE 

The Graneros shale, Greenhorn limestone, and Carlile 

shale are about 550 feet thick and are equivalent to the 

Benton shale. They were not mapped separately beca.use of poor outcrops. The best exposures in the quadrangle are in the SW!4 sec. 19, T. 7 S., R. 68 W., and 

in sec. 35, T. 6 S., R. 69 W. These formations are 

described in stratigraphic sections 11, 12, and 13. 

GRANEROS SHALE 

The Graneros shale (Gilbert, 1896, p. 564) lies conformably on the South Platte formation. The lower 

15 feet is dark-gray fissile noncalcareous siliceous silty 

shale that contains light yellowish-orange bentonite 

layers near the top. .Thin nodular sandstone beds lie 

in the lower part and platy sandstone beds in the upper 

part. This lower 15-foot-thick unit contains diagnostic 

fish scales that indicate that it is equivalent to the 

~1owry shale of Early Cretaceous (Albian) age (Dane 

and others, 1937, p. 210) (pl. 3). 
BEDROCK GEOLOGY 95 

The upper 210 feet of the Graneros shale is of Late 

Cretaceous (Cenomanian) age (Cobban and Reeside, 

1952, chart lOb) and is composed of dark-gray soft 

clayey noncalcareous shale that contains several layers 

of black noncalcareous hard siltstone. Cone-in -cone 

concretions that weather dark yellowish-brown are 105 

feet above the base. Thin beds of light-gray or yellowish-orange bentonite are abundant in the upper part. 

The formation is stained by rusty beds and veins. 

GREENHORN LIMESTONE 

The Greenhorn limestone ( GilLert, 1896, p. 564) contains, in ascending order, the Lincoln limestone member, 

the.Hartland shale member, and the Bridge Creek limestone member. 

The Lincoln limestone member (Logan, 1897, p. 216; 

Rubey and Bass, 1925, p. 47) of Cenomanian age is 

about 125 feet thick and contains many thin layers of 

pale yellowish-brown and dark-gray platy calcarenite 

that is composed mostly of shell fragments. 

At the base of the forniation is an extensive !-footthick dark yellowish-orange flaky soft bentonite that is 

called the marker bentonite in the Denver Basin (Sternberg and Crowley, 1954, p. 38). Overlying the marker 

bentonite is a pale yellowish-brown oyster-shell-bearing 

calcarenite bed about 2 inches thick composed of broken 

shells of Ostrea beloiti Logan and local impressions of 

a large ammonite with large horns, Acanthoceras ~ sp. 

(USGS Mesozoic loc. Dl). The calcarenite has a 

petroliferous smell when broken. Locally, thin lenses 

of the calcarenite bed also underlie the marker bentonite 

and are included in the Lincoln. 

The main part of the Lincoln is made up of olivegray platy calcareous shale that weathers yellowish 

orange and clayey, and thin beds of very light gray and 

yellowish-orange bentonite. At the top is a persistent 

thin platy petroliferous calcarenite bed composed of 

calcite prisms of Inoceramus shells, bones and tee.th of 

shell-crushing sharks, and foraminifera. Inoceramus 

pictus Sowerby, a small clam with evenly spaced fine 

growth lines, Ostrea elegantula Ne,vberry, a smoothshelled small oyster, and Oalycoceras cwnitaurinwm 

( I-Iaas) ~, a coarsely ribbed large ammonite, were collected at USGS Mesozoic loc. D2. 

The I-Iartland shale member (Bass, 1926, p. 33) of 

Cenomanian age is composed of about 60 feet of gray 

fissile calcareous fossiliferous shale that contains abundant paper-thin calcarenite layers, some thin yellowishgray crystalline platy limestone beds, and some thin 

yellowish-orange bentonite beds. Inoceramus pictus 

was identified. Ruth Todd of the U.S. Geological Survey also identified Thalmaninella greenhornensis (Morrow) of Cenomanian to early Turonian age. 

The Bridge Creek limestone member (Bass, 1926, 

p. 67) of Turonian age is about 130 feet thick and contains 7 or 8 beds of gray massive hackly or nodular, 

finely crystalline limestone about 6 inches to 2 feet 

thick, separated by bluish-gray nodular or thin-bedded 

calcareous· shale. The upper beds in the Bridge Creek 

contain Inoceramus labiatus ( Schlotheim) , a slender 

clam, and Ostrea sp., an oyster (USGS Mesozoic loc. 

D1088); the lower beds contain Sciponoceras gracile 

Shumard a.t other nearby localities. 

CARLILE SHALE 

The Carlile shale (Gilbert, 1896, p. 565) of Turonian 

age contains, in ascending order, the Fairport chalky 

shale member, the Blue Hill shale member, and the 

Codell sandstone member. 

The Fairport chalky shale member (Rubey and Bass, 

1925, p. 16, 40) contains about 45 feet of grayish-yellow 

thick-bedded nodular chalky marl that weathers pale 

yellowish orange and clayey; Inoceramus labiatus, 

Ostrea sp., and Oollignoniceras ~ sp. were found near 

the base of this member at USGS Mesozoic loc. D1089. 

The Blue Hill(~) shale member (Logan, 1897, p. 218) · 

includes about 8 feet of dark-gray blocky noncalcareous 

silty shale with a thin olive-gray fine-grained sandstone at the base. The shale contains rusty brown ironstained beds and streaks. 

The Codell sandstone member (Bass, 1926, p. 28, 64; 

Dane and Pierce, 1933) is a gray, finely crystalline, irregularly bedded to massive hard calcarenite that is only 

2 feet thick in this area. It weathers pale yellowish 

brown and is very resistant to erosion. Sand grains and 

small quartz and phosphatic pebbles were observed in it. 

Shark teeth, fish sca1es, and shell fragments are abundant; the rock generally breaks around the shell fragments. Prionocyclus wyomingensis Meek, Ostrea 

(Alectryonia) lugubris Conrad, and Scaphites whitfieldi Cobban were collected at· USGS Mesozoic locs. 

D1086 and D1087. 

According to Johnson ( 1930), the Carlile shale is 

overlain disconformably by the Fort Hays limestone 

member of the Niobrara formation. Apparently two 

scaphite zones, Scaphites nigricollenBis Cobban and 

Scaphites corvensis Cobban, are missing from the Front 

Range section as a result of this disconformity (pl. 3 ; 

Cobban and R·eeside, 1952, chart lOb). 

11. Gramwos shale, Greenhorn, limestone, an(l OarWe shale in 

the SW%SW14 sec. 19, T. "' S., R. 68 W. 

Carlile shale : 

Codell sandstone member : Feet 

11. Calcarenite, gray; weathers brown; massive; 

contains worm 1tubes, pieces of mollusks; 

made up primarily of calcite prisms from 

Inoceramus shells_______________________ 1.0 
96 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

11. Granf;rOS shale, Greenhorn limestone, and Oalile shale in 

the SW%SW14 sec. 19, T, 7 S., R 68 W.-Continued 

Carlile shale--Continued 

Blue Hill(?) shale and Fair.pol'lt chalky shale 

members of the Oar1ile shale, and the Bridge 

Creek limestone member of the Greenhorn 

limestone: 

10. Shale, gray, most covered. This interval is 

slightly thicker than normal because of 

duplication by faulting _________________ _ 

9. Limestone, light-gray, hard, finely crystalline ; 

breaks into angular pieces; ·base of Bridge 

Qreek limestone member--------"""'--------

Thickness of Blue Hill ( ? ) shale and Fairport 

chalky shale members of the Carlile shale and 

the Bridge Creek limestone member of the GreenFeet 

194.0 

2.0 

horn limestone _______________________________ 196.0 

Hartland shale member: 

8. Shale; weathers yellowish gray; calcareous, 

poorly exposed___________________________ 37. 0 

7. Limestone, gray, thin-bedded; weathers yellowish gray______________________________ .2 

6. Shale; weathers yellowish gray; calcareous; mostly covered ___________________________ · 24.6 

Thickness of Hartland shale member------------ 61. 8 

Lincoln limestone member : 

5. Limestone, gray, platy, finely crystalline; 

weathers grayish orange; contains ammonites, Inoceramus pictus (USGS Mesozoic 

·loc. D2) ___________________ .:,. ________ .:.____ . 4 

4. Shale ; weathers yellowish gray ; calcareous ; 

mostly covered--------------------------- 125. 0 

3. Limestone, gray, medium-:-crystalline; weathers 

dark yellowish orange ; composed almost entirely of oyster shells, Ostrea beloiti, Acanthoceras sp (USGS Mesozoic loc. D1) _____ _ .1 

Thickness of Lincoln limestone member---------- 125. 5 

Graneros shale: 

2. Shale; weathers yellowish gray; calcareous_____ 17. 0 

1. Shale, black, fissile, clayey; weathers olive gray; 

lower part is equivalent to the Mowry shale; 

mostly covered _____________________________ .,. 211. 0 

Thickness of Graneros shale _____________________ 228. 0 

12. Graneros shale at Helmer Bt·os. clay mine, NE%SW1A, sec. 

13, T. 7 S., R. 69 W. 

Graneros shale (Mowry shale equivalent) (part) : Feet 

5. Shale, medium-gray, silty ; limonitic streaks ; 

\veathers to small chips _____________________ 10.0 

4. Sandstone, grayish-yellow, blocky, laminated, 

fine-grained -------------------------------- 1.4 

3. Shale, medium-gray, blocky; weathers to chips__ 2. 9 

2. Sandstone, yellowish-gray, laminated, finegrained, hard--------~---------------------- 1.1 

1. Sandstone, moderate reddish-brown, ocherous___ 1. 3 

Measured thickness of Graneros shale ___ _:________ 16. 7 

13. Granero8 shale, Greenhorn limestone, and Carlile shale, in 

limestone quarry in the SW:J4NW% sec. 3{j, T. 6 S., R. 69 W. 

Carlile shale : 

Coden sandstone member : 

38. Limestone, yellowish-gray, nodular ; worm tubes, 

limonite nodules, oyster shells, and shark teeth_ 

37. Shale, yellowish-gray, fissile _________________ _ 

36. Limestone, yellowish-gray, sandy, nodular; worm 

tubes, oyster shells, and shark teeth fragments_ 

35. Calcarenite, yellowish-brown, sandy, lumpy, nodular, hard; limonite balls; moderate yellowish 

brown, crystalline in lower part ; fossiliferous ; 

contains Ostrea lngub'l"is, Prionocycltu; wyomingenis (USGS Mesozoic loc. D1098) _____ _ 

Feet 

1.00 

.10 

. 75 

1.7 

Thickness of Codell sandstone member___________ S. 55 

Blue Hill(?) shale member: 

34. Shale, dark-gray, blocky, silty, noncalcareous; 

rusty brown streaks ; weathers gray and 

muddy------------------------------------- 8.00 

33. Sandstone, olive-gray, fine-grained; weathers 

gray--------------------------------------- .10 

Thickness of Blue Hill ( ? ) shale member--------- 8. 10 

Fairport chalky shale member : 

~2. Shale, olive, blocky, thin-bedded, chalky, 

clayey; weathers tan gray; contains 0.1 ft 

calca:r,-enite near base. Oollignoniceras? sp. 

8.0 feet above base; Inoceramus sp. (USGS 

Mesozoic loc. D1089) -------------------- 47. 00 

Thickness of Carlile shale ______ _; _____ 58. 65 

Greenhorn limestone (part) : 

Bridge Creek limestone member : (part) 

31. Shale, gray; blocky, calcareous; weathers 

light gray; contains Inoceramus labiattts 

(USGS Mesozoic loc. D1088) ------------ 10. 0 

Rest of Greenhorn limestone and upper part of Graneros 

shale covered. 

Graneros shale (part) : 

Covered. 

30. Shale, gray and yellowish-orange, clayey, blocky; 

weathers fissile ______________________________ 27. 0 

29. Ironstone concretions, dark yellowish-orange, 

clayey, pisolitic; cone-in-cone around outside; 

these concretions probably are the same as similar concretions at Pueblo and other places in 

southern Colorado that contain Oalycoceras___ 1. 2 

28. Shale, gray, clayey, blocky; weathers to thin 

chips ; contains many 2- to 4-in. thick soft 

bentonite beds that weather fissile ____________ 36. 0 

27. Bentonite, dark yellowish-orange_______________ . 9 

26. Shale, gray, clayey, blocky; weathers fissile ____ 15. 0 

25. Ironstone nodules, 0.4-ft-thick, clayey, in darkgray shale-------~-------------------------- 1.8 

24. Shale, dark-gray, clayey, soft; yellowish-orange 

streaks------------------------------------ 5.0 

23. Ironstone concretions, dark-gray to yellowishorange, silty; weather blocky---------------- .7 
BEDROCK GEOLOGY 97 

13. Graneros shale, G1·emthorn limestone, and Carlile shale in 

l·imestone q1ta1-ry in the SWJ4NW:l4 sec. 35, T. 6 S., R. 69 W.-

Continued 

Graneros shale (part)-Oontinued Feet 

22. Shale, dark-gray, clayey, soft__________________ 2. 0 

21. Ironstone nodules, moderate yellowish-brown, 

clayey, soft centers__________________________ 1. 2 

20. Shale, dark-gray, clayey, soft; weathers fissile ___ 11. 0 

19. Sandstone, grayish-orange, nodular------------- . 1 

18. Shale, darl{-gruy, clayey, platy, soft____________ 1. 0 

17. Sandstone, grayish-orange, platy, fine-grained___ .1 

16. Shale, dark-gray, bentonitiC-------------------- 12. 5 

15. Shale, pule yellowish-brown, nodular, and gray 

siltstone mottled witb brown_________________ 1. 5 

14. Siltstone, very dusky red, platy________________ .1 

13. Sbale, pale yellowish-brown, platy------------- 2. 0? 

(Mowry shale equivalent:) 

12. Bentoni·te, yellowish-orange ____________________ . . 2 

11. Snndstone, yellowish-orange; weathers olive 

gray, nodular ______________________________ 1.0 

10. Shale, black, platy, bard; weathers fissile, medium gray ; noncalcareous; contains fish scales__ 4. 0 

9. Shale, light olive-gray, fissile, soft_____________ . 7 

8. Siltstone, yellowish-gray, platy; dark yellowishorange streaks------------------------------ 2.25 

7. Sandstone, yellowish-gray and dark yellowishorange, platy, unevenly bedded; top surface uneven ; contains clay balls-------------------- . 8 

6. Shale, medium light-gray, fissile, and thin sandstone layers_________________________________ .9 

5. Sandstone, nodular, fine-grained, and interlayered 

medium light-gray to dark yellowish-orange 

und white shale_____________________________ 1. 0 

4. Sandstone, dark yellowish-orange to white, mas- sive, fine-grained____________________________ .7 

3. Shale, light olive-gray and yellowish-brown; 

snndy near top; carbonaceous________________ .5 

2. Sandstone, light olive-gray, nodular, fine-grained, 

carbonaceous------------------------------- .3 

1. Siltstone, brownish-gray, carbonaceous_________ 1. 6 

Measured thickness of Graneros shale ___________ 133. 05 

NIOBRARA. FORMA. TION 

The Niobrara formation (Meek and I-Iayden, 1862, 

p. 419, 422) of Late Cretaceous age is predominantly 

marine limestone, chalk, and chalky shale. The lower 

part is w~ll exposed at many places, but the upper part 

is poorly exposed. liard beds at the base, in the middle, 

and at the top form small hogbacks. The Fort Hays 

limestone member (Williston 1893, p. 108-109) at the 

base n.nd the Smoky Hill shale member (Cragin, 189'6, 

p. 51) ma.ke up the formation. 

FORT HAYS LIMESTONE MEMBER 

The Fort IIays limestone member of Coniacian age 

averages 35 feet in thickness and contains yellowishgray, dense hard thick massive limestone beds at the 

base ~tnd softer, thin tabular limestone beds at the top. 

Thin calcareous silty shale beds and bentonite beds separate the limestone beds. The lowest bentonite lies 11 

feet above the base. Sandy limestone beds at the base 

contain clusters of altered pyrite crystals. · The lithology of the member is shown in stratigra,phic soction 14. 

Two zones of fossils were found in the member. The 

lower 15 feet (USGS Mesozoic loc. D1090) contains 

Inoceramus sp. (not deformis) and Ostrea congesta; 

the upper 20 feet (USGS Mesozoic locs. D4 and D1091) 

contains Inoceramus dejormis Meek and Ostrea congesta. Mrs. Cecelia Head, who formerly owned the 

quarry in the NE*NW*SE* sec. 2, T. 7 S., R. 69 W. 

(USGS Mesozoic loc. D1085), loaned to the author an 

impression of an ammonite said to be found in the 

middle of the member. W. A. Cobban identified it as 

Peroniceras sp., which is most common in rocks of 

Coniacian age but i~ rare in the western interior of the 

United States. 

14. Niob1·ara formation in limestone quar·ry in the SWJ4NW:l4 

sec. 35, T. 6 S., R. 69 W. 

Niobrara formation (part) : Feet 

Smoky Hill shale member (part) : 

38. Shale, yellowish-gray; clayey, calcareous, 

blocky; weathers to smallligbt-gray chips_ 8. 00 

Fort Hays limestone member : 

37. Limestone, yellowish-gray, massive; upper 

part weathers sbaly. Inoceram1t.S deformis 

(USGS Mesozoic loc. D1091) ------------ 1. 40 

36. Shale, yellowish-gray, calcareous:----------- 1. 25 

35. Limestone, yellowish-gray, nodular; weathers shaly; Inocerarmts deformis__________ . 60 

34. Shale, yellowish-gray ; weathers to irregular 

flakes---------------------------------- 1.25 

33. Limestone, yellowish-gray, massive; Inoceramus deformis------------------------ 1. 80 

32. Shale, yellowish-gray, platy, hard, calcareous-------------------------------- .40 

31. Limestone, yellowish-gray, massive; l-in. 

thick shaly parting 5 in. from top ; lower 

3 in. platy limestone; weathers sbaly ---- 1. 90 

30. Shale, yellowish-gray,· hard, calcareous______ . 20 

29. Limestone, yellowish-gray, massive, Inoceram1ts detormis________________________ 2. 10 

28. Shale, yellowish-gray, calcareous; bentonite 

in"lower 2 in___________________________ . 60 

27. Limestone, yellowish-gray, massive, nodular; 

Jnoceram1ts £lefonnis____________________ . 80 

26. Shale, yellowish-gray, platy; bentonite at 

base; Inoceram1ts defot·mis_______________ . 90 

25. Limestone, yellowish-gray, massive________ 2. 70 

24. Shale,- yellowish-gray; bentonite in lower 

1 in---------------------------------------·25 

23. Limestone, yello~vish-gray, massive _________ . 2.10 

. 22. Shale, yellowish-gray; bentonitic in middle__ . 20 

21. Limestone, yellowish-gray, massive; Inoc-

"eramus deformis, Ostrea congesta________ . 60 

20. Shale, yellowish-gray, platy; bentonite at 

base----------------------------------- .50 
98 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

14. Niobrara formation in limestone quarry in the SWlA,NWlA, 

sec. 35, T. 6 S., R. 69 W.-Continued 

Niobrara formation (pa.rt)-Oontinued 

Fort Hays l.i.mestone member-Continued Feet 

19. Limestone, yellowish-gray, massive; weathers hackly; Inoceramus deformis, Ostrea 

congesta ------------------------------- 2.00 

18. Shale, yellowish-gray, granular, bentonitic__ . 20 

17. Limestone, yellowish-gray, massive; weathers hackly ; Inoceramus sp. (not d.etormis) 

(USGS Mesozoic loc. D1090) ------------- 1. 10 

16. Bentonite, grayish yellowish-green, blocky__ . 75 

15. Limestone, yellowish-gray, massive_________ . 40 

14. Shale, yellowish-gray, fissile_______________ . 20 

13. Limestone, yellowish-gray, massive_________ . 30 

12. Shale, dusky yellow; bentonite at base_____ . 50 

11. Limestone, yellowish-gray, massive; weathers blockY--~--------------------------- .75 

10. Shale, dusky yellow--------.--------------- .10 

9. Limestone, yellowish-gray, massive; platy at 

base; Inoceramus sp. (not deformi.s)----- 1. 50 

8. Shale, dusky-yellow, platy to blocky________ 1. 60 

7. Limestone, yellowish-gray, massive_________ 5. 20 

6. Shale, yellowish-gray, fissile_______________ . 20 

5. Limestone, yellowish-gray, massive_________ . 70 

4. Limestone, yellowish-gray, nodular ; worm 

tubes---------------------------------- .50 

3. Shale, yellowish-gray, silty, fissile, calcareous_ .20 

2. Limestone, yellowish-gray, nodular; worm 

tubes ---------------------------------- .40 

1. Shale, yellowish-gray, fissile_______________ . 20 

Thickness of Fort Hays limestone member------- 34. 35 

The Fort Hays limestone generally dips 60° NE.; in 

the southern part of the area, however, it is overturned 

to the east and cut out by a thrust fault. In a quarry 

in the NEtt4NEI4 sec. 24, T. 7 S., R. 69 W., the limestone is folded strongly by a bedding-plane fault. In 

the SEI4 sec 30, T. 7 S., R. 68 W., the limestone is brecciated by the Jarre Creek fault and recemented with 

calcite. 

SMOKY HILL SHALE .MEMBER 

The Smoky Hill shale of Coniacian and Santonian 

age conformably overlies the Fort Hays limestone and 

is 535 feet thick in this area (pl. 2) . The member is 

best exposed in the NEI4 sec. 27, T. 6 S., R. 69 W., and 

in the SWI4 sec. 19, T. 7 ·s., R. 68 W., along a branch 

of the Jarre Creek fault. The lithology of the member 

is shown in stratigraphic section 14. 

The member consists of chalky shale with several 

thick beds of chalky limestone. A yellowish-gray soft 

calcareous shale in the lower 22 feet contains thin beds 

of limestone similar to those of the Fort Hays that 

weather hackly and contain Inoceramus deformis and 

Ostrea congesta. Next is yellowish-gray chalky fissile 

shale that contains thin bentonite beds and a yellowishgray chalky platy speck1ed limestone about 70 feet above 

the base. About 135 feet above the base is a very pale 

orange thin-bedded speckled chalky ridge-forming 

limestone 17 feet thick that weathers to a sticky calcareous clay. The limestone contains Olioscaphites 

choteauensis Cobban and large shells of Inoceramus 

platinus Logan that are covered with shells of 0 strea 

congesta. 

Olioscaphites choteauensis is shown by Cobban and 

Reeside ( 1952, chart lOb) as being expected near the 

top of the Smoky Hill. Inasmuch as it was found in the 

middle instead of near the top, in the Kassler quadrangle the characteristic faunas of the Telegraph Creek 

formation and Eagle sandstone (pl. 3) may lie in the 

upper part of the Smoky Hill rather than in the lower 

part of the Pierre shale. The upper half of the Smoky 

Hill member contains grayish-orange fissile to thickbedded chalky shale. At the top is yellowish-orange 

thick-bedded speckled chalky ridge-forming limestone 

that weathers to large irregular flakes and slabs and 

then to calcareous clay; Unweathered limestone is dark 

gray. The upper limestone contains smooth baculites, 

Ostrea congesta, Inoceramus sp., and fish scales and 

bones. 

Chalk beds in the Smoky Hill are contorted and fractured. In the SWI4SWtt4 sec. 19, T. 7 S., R. 68 W., 

the dip varies 36° in 12 feet of section-from a normal dip of 60° NE., to an overturn of 84° SW. In the 

SWtt4 ·sec. 30, T. 7 S., R. 68 W., the member is drastically brecciated by the J arre Creek fault and the fragments are recemented by calcite. Small fractures in the 

chalk at other places are also recemented by ·calcite. 

Analyses of the chalk that were considered typical 

by Elias (1931, p. 38-39) show an average of 85 percent 

calcium carbonate, most of the other 15 percent being 

insoluble in acids. No quarries were opened in this 

clayey chalk in the ·Kassler quadrangle. . 

The names Fort Hays limestone and Timpas liinestone have been considered to be synonymous ·and are 

used interchangeably by many geologists, but the upper 

boundary of the type Tim pas limestone is not c'Oincident 

with the upper boundary of the type Fort Hays limestone. Gilbert (1896, p. 566-567) defined the Timpas 

limestone as the lower 175 feet of the Niobrara group. 

He recognized 50 feet of limestone beds at the base that 

are now called Fort Hays, but he also included in his 

Timpas a hogback-forming white limestone and underlying shale of the Smoky Hill; he stated that the upper 

limit of the Timpas was indefinite even at the type locality. Away from the type locality I found that the 

white limestone in the Smoky Hill becomes softer and 

even more indefinite. Along the mountain front near 

Kassler, it forms only .a local low ridge between the 

Fort Hays and the middle chalky limestone rather than 

the prominent bench that is common south of the 
BEDROCK GEOLOGY 99 

A:t;kansas River. Over the years this erroneous interpretation of Gilbert's nomenclature has been used in 

many articles on Front Range geology. The proper 

relationship of these beds is shown in Cobban and Reeside ( 1952, chart lOb). 

The conformable contact of the Smoky Hill shale and 

the Pierre shale is marked by a change from yellowish 

orange to olive gray and from chalk to calcareous shale. 

The change can be seen in a cut at the north edge of 

the quadrangle. 

PIERRE SHALE 

The Pierre shale (Meek and Hayden, 1862, p. 419, 

424), of Late Cretaceous Campanian to Maestrichtian 

age, is predominantly olive-gray clayey shale and sandstone of marine origin. Limestone and ironstone concretions are abundant and characteristic of the Pierre. 

Fossils are abundant and were collected inten·sively. 

Faunal zonation of the Pierre for this quadrangle 

was based partly on earlier work by Cobban in other 

areas and partly on the local fossils. Most of the faunal 

zones are based on Bamdites, but some are based on 

other ammonites (table 2) that have equal value as zone 

fossils. Thirteen zone lines, including one of phosphatic nodules, are shown on the geologic map (pl. 2). 

One extra fossil zone, Baculites obtusus, is shown on 

plate 3 but not on the geologic map. The character of 

the structural disturbance in the Pierre shale caused by 

the J arre Creek fault (pl. 2) became known only after 

the faunal zones were traced in the field. Until that 

time a questionable single fault had been drawn through 

the PietTe. 

The Pierre shale is well exposed only in the southern 

part of the quadrangle where, unfortunately, the rocks 

are :faulted and a complete stratigraphic section cannot 

be measured. No beds are resistant enough to :form 

ridges, but the formation is well exposed on the flanks 

of eroded pediments and in the banks of streams. The 

best outcrops are in sec. 19, T. 7 S., R. 68 W., and serve 

as the basis for the description below. 

The Pierre shale consists o:f about 5,200 feet o:f marine 

sediments which contain five major groups o:f strata. 

Table 3 shows the main subdivisions of these five units. 

The basal part of the Pierre shale consists o:f 1,200 

:feet o:f olive-gray clayey fissile, chiefly noncalcare.ous 

shale (table 3). The lower 80 :feet is calcareous clayey 

shale and thin bentonite interbeds ; from 80 to 500 feet 

above the base the shale is iron -stained, noncalcareous, 

and silty and has beds o:f bentonite that contain selenite 

crystals. Peculiar crystals :from the SE'%,SW%, sec. 19, 

T. 7 S., R. 68 W., are flattened so that the c axis is 

shortened and the forms (110) and (010) nearly eliminated. The resultant crystals are dominantly a combination of the forms (111) and (103). The lower 500 

feet of shale is generally unfossiliferous. A horizon 

between 500 and 600 feet is distinguished by B aculites 

asperiformis Meek, and is characterized lithologically 

by large brown septarian limestone concretions, small 

gray limestone concretions, and hard fissile lenticular 

siltstone ·beds. At 600 feet above the base large rough 

hard gray petroliferous crystalline masses of limestone 

were found. The term "tepee butte limestone" is used 

for this type of limestone because near Pueblo the large 

masses weather to cone-shaped hills that were called 

tepee buttes by Gilbert ( 1896, p. 569). These tepee 

butte limestones weather to dark yellowish -orange 

cavernous fragments :from which project casts o:f gastropods, pelecypods, and cephalopods, including 

B aculites asperiformis Meek. 

Between 600 and 1,200 feet above the base is slightly 

calcareous, blocky shale that contains abundant clayey 

ironstone concretions. The smooth ovate B aculites n. 

sp.lies between 800 and 1,100 feet above the base within 

this horizon. 

The medium-grained olive-brown Hygiene sandstone 

member (Fenneman, 1905, p. 31-33) is exposed from 

1,200 to 1,775 feet above the base. Its outcrop belt is 

covered by a profuse growth of yuccas. It consists o:f 

thin-bedded friable micaceous sha:Iy sandstone with a 

few thick-bedded hard limonite- or calcite-cemented 

sandstone beds. Small crystals of ~arcasite are 

abundant in the unweathered greenish-gray sandstone. 

Where weathered, the sandstone is dusky yellow and 

limonitic. Fossils apparently were the centers for 

calcite concentration in the sandstone, for nearly all 

fossils are found in the centers o:f dark greenish-gray 

hard sandy limestone concretions. Weathered concretions are light greenish gray and split around the fossils. Interconnected crevices in the concretions contain 

marcasite crystals and encrustations of clear barite. 

· From 1,200 to 1,400 feet the Hygiene is a sparsely 

fossiliferous, :friable olive-brown shaly sandstone that 

has some platy calcareous hard sandstone beds in its 

lower part, but in the upper part small limestone concretions and thinly la.minated beds are abundant. They 

commonly contain well-preserved Inoceram!U8 sublaevis 

Hall and Meek. The. thin limestone beds locally thicken 

abruptly to form large masses of rough gray crystalline 

tepee butte limes.tone. B aculites gregoryensis Cobban 

is found in beds from 1,200 to 1,400 :feet in the Hygiene 

sandstone member. At 1,400 feet Baculites scotti Cobban is first found in limestone beds at the base of a thick 

section that is characterized by hard thin sandy ironstone beds and ironstone concretions. This ironstone 

unit lies from 1,400 to 1,775 feet above the base of the 

Pierre and also contains B. scotti. The ammonites 
100 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

TABLE 2.-Strat.igraphic distribution by ammonite zones of tossiZs ot the Pierre shale 

[Numbers refer to fossil localities shown on pl. 2; see alsop. 118-120. aff., most closely resembles the species listed; cf., not certainly identified but resembles the species listed· 

? , may be the species listed] . ' 

~ Q) 

Q) 

~ 

~ Baculites ;s asperiformis 

~ Meek 

Species ~ ~ 

e 

~ 

17 15 16 18 19 

~ 

d 

.. 

:tl "' ] 

~ 

20 21 

Baculites gregoryensis Cobban Baculites scotti Cobban 

22 22a 23 24 25 26 27 30 32 28 29 31 33 34 35 il6 37 3R 39 40 41 42 43 44 45 46 47 48 

---------------·l--1----------------------------------

Coelenterata: 

Corals ___________________________________ ---- --- --- ______ --- --- --- --- --- --- --- --- --- --- --- --- --- --- ___ --- --- --- --- --- ___ ___ ___ X _________________ _ 

Molluscoidea: 

Bryozoa: Membranipora SP---------------------- ---- _____________________________________________________________________________________________________ _ 

BT~~~fa ~~t:ida Meek and Hayden ______ -------------------------------------------------------------------------------·-----·-------------------- Terebratula helena Whitfield ____________ ---------- ______ ------------------------------ ___ --------- ___ --------------- _____________________ --· _____ _ Mollusca: 

Pelecypods: 

Nucula planimarginata Meek and 

Hayden ______________________________ ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ___ --- --- --- --- --- _____________________________ _ 

SP--------------------------------- ---- --- --- ___ --- --- --- --- --- --- --- --- --- --- --- ___ --- --- --- ___ --- --- --- --- --- --- ___ X ___ --- ___ --- ___ --- __ _ Nuculana evansi (Meek and Hayden) .. ---- --- --- ______ --- --- --- --- --- --- --- --- ___ --- ___ --- --- --- ____________ --- --- _________ cf _________________ _ n. SP------------------------------- ---- ____________ --- ___ --- --- --- --- --- --- --- ______ --- ___ --- ______ --- ··-- --- --- _____________________________ _ Nemodon sulcatinus (Evans and 

Shumard) ___________________________ ---------------------------------------------------------------------------------- --- --- --- --- --- --- --- --- Inoceramus sublaevis Meek and Hay- den __________________________________ ---- --- --- --- --- --- --- --- --- X --- --- --- --- --- --- --- --- --- ___ X --- --- ---· -·~- ______ cf ___ ___ ___ X ________ _ tenumneatus Hall and Meek _______ ------- _________ ------ X X X------ X--- X ___ X X--- ______ ------------ _________ X _________________ _ 

aff. convexus Hall and Meek ________ ---- --- --- --- --- --- --- X --- X --- X X X X ___ --- X --- ___ --- --- --- --- --- ______ --- _________ --- ______ --- cf. cycloides Wegner ________________ ------- _________ ------ X--------------------- X--------- ___ --------- --- --- ______ --- ___ --- ___ --- ___ --- --- typicus (Whitfield) _________________ ---------------------------------------------------------------------------------------------------------- saskatchewanensis Warren __________ ---- --- --- ______ --- --- --- --- --- --- --- --- --- --- --- X --- --- ___ X --- --- X --- ___ X ______ --- X X ___ --- ---

sagensis Owen _____________________ ---------------------------------------------------------------------------------------------------------- ? jibrosus (Meek and Hayden) _____ ------- ___ --------------------------------------------------------------------------- ___ ------------------

C~~!b~~~8M~~~:n~~-~~~~-~~======= :::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: -X ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: 

balchii Boehm ______________________ ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ··-- --- --- --·· --- --- sp _________________________________ ---- X------------------------------------------------ X X--- X --- --- --- --- ~-- --- --- --- --- --- --· --- X Pteria linguaeformis (Evans and 

Shumard) ___________________________ ------------------------------------------------------- X ___ X--------- X ____________ --- ___ --- ___ ------

SP--------------------------------- ---- --- --- --- --- --- --- --- --- --- --- --- X--- X------------------------ --- --- --- --- --- X------------------

Ostrea inornata Meek and Hayden _____ ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --·- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- SP--------------------------------- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --· Pecten nebrascensis Meek and Hayden. ---- --- --- --- ___ --- --- --- --- --- --- --- --- ··-- --~ --- --- --- --- ·-- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

~~~~{£~~~!~J~v~~~:?ii~:~~~ :::: === === === === === === === === === === === === === === === === === === === === ==~ ~== === === === === === === === === === === === ::: 1~ci~~ ~~~yd;~~aW:~~r~~-~~=~~~~=== ==== ::: ::: ::: ::: ::: ::: === === === === === ::: ::: ·x ::: ::: ::: ::: ::: ·x ::: ::: ·x ::: ::: ::: ·x ::: ·x ::: ::: ::: ::: ·x 

subundata Hall and Meek __________ ---- --- --- ______ --- --- --- --- --- --- --- --- --- --- --- --- --- --- ___ X --- X --- --- --- --- X ___ X ___ --- --- --- ---

SP--------------------------------- ---- --- --- --- ··-- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ·-- --- --- --- --- --- --- --- X --- --- --- --- --- ---

~~i~:~~ !:~~l~~~~e~~;-~~~~~~~~~:= ==== === === ==~ ::: === === === === =~ === :~ =~ === === === ~~ === === === ~~ ~~ =~ ~~ ~~ === ::: ~~ === =~ === === === ::: === Pelecypod, genus undetermined _______ ------------- X-----------· --· ··-- --- --- --- --- --- --- --- --- ___ X------------ --- --- X ___ X--··--------- ·-- Scaphopoda: 

Dentalium gracile Hall and Meek. _____ ---- --- _________ --- --- --- --- --- --- --- --- --- --- --- --- --- --~ ___ --- --- --- --- --- --- --- --- ___ ___ X --- -"'- --- --- Scaphopod, undetermined _____________ ---------------------------------------------------------------------------------------------------------- Gastropoda: 

Margaritella n. sp ______________________ ·--- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- •-- --- Polinices? SP--------------------------- ---- --- _________ --- --- --- --- --- --- --- --- --- --- --- --- --- --- ___ --- --- --- X --- --- --- --- ___ ___ X --- --- --- --- Amauropsis paludinaeformis (Hall and 

Meek>------------------------------- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- Anchura? SP--------------------------- __________ . ______ --- --- --- --- --- --- ___ --- ______ --- --- --- --- ___ --- --- --- --- --- ___ --- --- X ______ --- --- --- --- Drepanochilus nebrascensis (Evans and . Shumard>---------------------------------- _________ --------------------------- --- --- --- --- --- ___ X------ .X------------ ___ X---------------

sp_ -------------------------------- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

~fe~~~~gfz~~:~i- ~~-i:~~ ~-~:::::::::::: :::: ::: ::: ::: -~ ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: -~ ::: ::: ::: ::: ::: ::: ::: ::: ::: ·x ::: ::: ::: ::: 

Gastropod, undetermined ______________ ---- --- --- ___ --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- "-- --- --- --- --- --- --- --- --- --- --- Cephalopoda: 

Baculites obtusus Meek_________________ ? --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --.- __ ! --- --- --- ---

~~~~-if(~:!~l~~r:bed-veiiter):::::: ==== === === === -~ -~ -ci === ::: === ::: ::: ::: === === ::: === === ::: ::: === === === === === === === ::: === === === === ::: === === 

rugosus mrr:~~~;i:~:~=============== Cobban ____________________ ==== ---- === --- --- === --- === === --- --- --- --- --- --- --- === === =~ === === =~ === --- --- --- =~ === --- =~ === --- --- --- --- --- ~~ === === === --- ~~ ~~ --- ~~ -~- --- --- --- --- --- ~~ === === ~~ ~~ --- === --- ~~ ~~ --- --- ~~ --- --- ~~ ~~ --- ~~ eliasi Cobban ______________________ ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- grandis Hall and Meek _____________ ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- clinolobatus Elias ___________________ ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- SP--------------------------------- ---- X X X--------------- X--------- X--------- X------------------------------ X------------------

~:l:~gg:::: ~:,.~~~~ fii:~~~~>iiay"deii) :::: ::: ::: ::: ::: ::: ::: === ::: ::: ::: ::: ::: ::: :;: === === ::: ::: === ::: === ::: === === ::: ::: === ::: ::: === === ::: === === SP--------------------------------- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- Oxybeloceras crassum (Whitfield) ___________ --- _________ --- ___ --- --- --- --- --- --- ___ --- --- --- --- --- --- --- --- --- --- --- --- --- X --- X X --- --- --- ---

SP--------------------------------- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X------------------------ Didymoceras nebrascense (Meek and 

Hayden>----------------------------- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ·--

~~~~:-~~~~~~~-~~~~~~}_=-~============ ==== === === === === === === === === === === === :~ === === === ::: === === === === ::: === === === === === -~ =~ -~ =~ === ::: ::: === 
BEDROCK GEOLOGY 101 

TABLJ~ 2.-Stmtig·mphic dist·ribution by ammonite zones of fossils of the Pierre shale-Continued 

Species-Continued 

Baculites 

asperijormis Meek 

Baculites gregorgensis Cobban 

Baculites scotti Cobban 

---l-~-~~~--1--l--~~---~~-.-~~--'l--~~~-------~--~~~.-~~~.-.--.-:--.-~--~ 

17 15 16 18 19 20 21 22 22a 23 24 25 26 27 30 32 28 29 31 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 

---------------·1------------------------------------

Mollusca-Continued 

Co;}~~~~gfc~~~~Ue~~~~~l~ ~~~---············· ••••••• --- X X .•. --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --· -·- --- --- --- --- --- --- --- X X --- --- DiscoscaJ>hitcs n. SP-------·---------··· ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- SP-------·-·-·--------------------- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- A?laJJaChylilsctts? complexus (Hall and 

Meek) •••• -----·-·------------------- -·-· --- --- --- --- --- --- --- --- --- --- ~-- --- --- --- --- --- --- --- --- X --- --- X --- -•- --- --- --- --- --· --- --- --- --- llfennites? n. SP-----··········-···-···· •....•. --- ... --· --- --- --- --- --- --- --- ---· --- --- --· --- --- --· --· X --· --- X --- --- --- --- --· --- --- ••• --- ••• --- Pochydiseid ommonlte _________________ ---- --- --.- ••• --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X X --- X X --- --- X --- --- --- --- ___ --- Placenticeras meeki Boehm _____________ -----··------------------ ••. --·--------------------------------------------------------------------- ••• --- intercalare (Meek ond .Hoyden) •••••••• --------------------------------------·-----------------------------·-----------------·--------------- sp. -------------------------------- ____ : •. --- --- --- --- --- --- --- X --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- SJ>henoliiscus sp ••••••••••••••••••••.••• ---- --- --- --- --- --- --- --- ···- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- Crustocea: 

Arthropodo: J)ukoticancer SP------------------------ -·-· ___ ··- ___ --- ___ ... ______ ... ______ --- ___________________________ ... ___________________________________ _ Fish: 

Ichthyodectes sp. (scales) ____________________ --- X --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

Bones •••••.•••••••• -----------······------------------------------.'!..-------------------------------------~-------------------·----------------- Vortobrt\ •••••••••••••••• _______________ ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X --- --- --- --- --- 'l'eeth __________________________________ ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --~ --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

Petrified wood •• --------------------------- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- -- 7 --- --- --- --- --- --- --- --- --- ---

Spocles 

~= ·~ ~ 

= ~~ .. .c oo-e .. ~ .c ~ 

::~ ~ 0 '0 

ool» Baculites scotti ~~ ~ ~ 0 ;:!<5 

Cobban- Eriteloceras jenneyi ·;; ~~ Baculites grandis Baculites clinolobatus .. -e ........ f: ,g Continued 00'0 · (Whitfield) o::~'O Hall and Meek Elias o::~d o::~- 8 ~ t;o5 o.Q) -;;~ ~'S ~~ .. <>,lod 

~~ <>·~ ~.c .'l::l "' ~~ -~» 

~ ij~ 

~e ~::: i;lc:e .,......, o:;~tll 

~ ~ Q:l ~ ~~ 

---~~---~-~-------------·1-~~~~-~--------l--~----~--·~---~---------~--

----------·------------------------------------------------------ Coolonteroto: 

Corols ••••••••••••••••••••••••••••••••••• ___ •••••. ___ ••• ···- •.• --- --- X •••••• ------- .•• ____ ------ ••• ------ ••• --------- •.•••• ------ ••••••••••••••• Mollu~coldeo: 

Bryozoa: 

111embraniJ>Ora SP----------------- •.. ___ ... ______________________ --- ___ --- --- ____ --- --- ____ --- --- --- --- --- --- --- X --- --- --- --- ... --- --- --- --- ---

132!~~~~l~0~~Widtt Meek ond Hayden .••• ___ •••.••••. ________________ --- ___ --- _______ --- --- ____ --- ___ --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X 

'l'erebrahtla helena \Vhltfleld ..•••• __________________ •.. ____ --- ___ ..• --- ___ --~ ----· --- --- ____ --- --- --- --- --- --- --- --- --- --- --- --- --- --- X X------

Mollusco: 

Pelecypodo: 

Nucula J>lanimaroinata Meek and 

Hayden •.••••••••••••••••••••..••• _________ ••. ________________ --- ___ --- --- ---- --- --- ____ --- --- --- --- --- ___ --- --- --- --- --- •••••• --- X --- --- ---

SP---------------------------- --- --- --- --- ••. --- ••. -~-- --- --- --- --- --- --- ---- --- --- ---- --- --- --- --- --- ..• --- --- --- --- --- •.. X --- --- --- --- --- Nttrulana evansi (Meek and l:IoydenL.--------------------- •••••• ___ ••• __________________________________________________________________________________________________ _ 

n. SP------------------------- --- --- --- --- --- --- --- ---- --- --- X X --- --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ••• --- Nemolion S1tlcatinus (Evans and 

Shunwrd) .•••••••••••••••••••••••. ___ ••• --- ______ ··- ··-- --- --- --- X-------------------------·-----·--------------------------- --- --- --- --- --- Inoceram1ts s1tblaevis :Meek and 

l:loyden •••••••••••••••••••••••••••••• _____________ . ______ --- ___ --- --- --- --- ---- --- --- ____ --- --- --- --- --- --- --- ••. --- --- --- --- --- --- --- --- --- --- temtilineattts Holland .Meek •. _________ --- _____________ --- --- --- --- --- --- ---- --- --- ---- --- --- --- --- --- --· --- --· --- --- -·· --- --- --- --- --- --- --- afT. convexus 1-Iall ond l\1eek ..••••••••• ··- _____________ --- --- --- -·· --- --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

~:p~g~~~o~~~~h1i8~j~l<r:::::::::: ::: ::: ::: ::: ~== ~== ~:: ~=== ::: ::: ::: ::: ::: ::: :::: ::: ::: ··x ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: 

sasl:atchewanensis Worren. ••• X X ___ --- X ___ ....••. --- --- --- --- --- --- ---- --· --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- saoensia Owen .••••••••••.•••• --- ••• --- --- --- •.. ___ ---- --- --- --- --- --- --- X --- --- ---- --- -·- -·- --- --- -·- --- --- -·· --- --- --- --- --- --- ••• --- --- ? jibrosus (Meek ond Hoy- . den) .••.••••••••••••••••••.••• ___ --- ••• _________ --------------··--------------·-------·----------------·- X--- X X--- X------ X X---

~~~~b::::sl\~~~;~1~~~~-~1-~:~:~~= ::: ::: ::: ::: ::: ::: ::: --~ ::: ::: ::: ::: ::: ::: :::: ::: ::: :::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: 

balchii Boehm .•••••••..•.•.•. _________________________ --- X-------------------· ___ -----------··---·--- --- --- --· --- --- --- --- --- --- --- --- --- ---

SP---------------------····--- --- ..•.•• --- --· -·- X ---- X --- X X --- X ---- --- X .•.. --- --- --· --- --- --- --- --- --- --- --- --· --- --- --- X --- --- Pteria linouaejormis (Evans and 

ShUillOI'd) ______________________ --- --- --- --- --- --- --- ---- --- --- --- --- --- --- ---- --- --- ---- --- --- --- --- --- --- --- ••• --- --- --- --- --- --- --- --- --- ---

o~~;t!~~~~~~!~~~~~~~~~~l~~~~-~~~:~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ -~ ~~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~~ ~~~ ~~~ ~~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~-~ ~~~ ~~~ ~~~ sp •.•••••••••••••••••••••••••• --- ••• --- --- --- --- --- X-·---- X X-·- X-------------------------·-----~--·------------ .X--·----··-·-------

Pecten nebrascensis Meek and 

1-Joydcn .••.••••••••• _______________________________________ --- --- --- --- --- ---- --- --- --·- --- -·- --- --- --- --- --- --- --- --- --- •.• --- --- X---------

M~l~~~:.::;~~!~~~:-~~-~~~~~~~~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~~ ~~~ ~~-~ ~~~ -~ ~~~ ~~~ ~~~~ ~~~ ~~~ ~~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ ~~~ -~ ~~~ ~~~ ~~~ Orenella elegantula Meek and , Hayden •••• ----------·····----- •••••..••• ____________ •••. ___ ••• --- --- .•• --· ---- --- --- ---- --- --- --- --- --- -·- --- --- --- --- --- ••• --- --- X --- --- ---
102 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

TABLE 2.-Stratigraphic distribution by ammonite zones of fossils of the P·lerre shale-Continued 

~'"' 'i ;; ~~ .. .0 = j ;S .0 ~ 

~I» ~ 0 '0 

BaculUes scotti J5oS 0 ~~ Cobban- ~~ ""'"' Exitelocera& jenneyi ~ :~ ~~ Baculite& grandis Baculites clinolobatus 

Species-Continued Continued oo'O ~~ (Whitfield) ~ ""'0 Hall and Meek Elias "'~ .. ~ 8 ~ _g~ 

~~ ~~ :g-; ~ ~~ :ti"' :ti ~~ ~~ ~~ ~~ ~ ~--- ~--- ~ ~fl.) ~ ~~ 

49 50 51 52 53 54 56 55 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 

---------------1------------------------------------

Mollusca-Continued 

Pelecypoda-Continued A&tarte gregaria (Meek and Hay- den) _________________________________________ ,_-··-------- ______ --- ______ -------------------------------------------- _________ ------ X ________ _ 

llltcina occidenta.li& Morton _______ --- X --- --- --- --- --- ---- --- ---. --- --- --- --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- __ _ subundata Hall and Meek ___________________ X--- ___________________ --- _______ ------- _____________________________________________________ _ 

SP-------------------------~-- --- --- --- --- --- --- --- ---- --- --- X X X --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- X --- --- --- Tellina.,citula Meek and Hayden. _______________ ------ _____________________________ --- ______________________________________________ cf ••• ___ ••• 

Geltena gracili& (Meek and Hay- . · 

den)------------------------------ X----------------------------------------------- X X X X------ X------ X X cf X X---------------

SP---------------------------- --- --- --- ---- --- --- --- ---- --- X --- --- --- --- ---- --- X ---- --- --- --- --- --- --- ? --- --- --- --- --- --- --- --- X --- ? Pelecypod, genus undetermined •• _______________ --- --- ---- ~-- _______________ ---- ___ --- ---- _____________________________________________________ _ 

Scaphopoda: Dentalium gracile Hall and Meek. _______________ --- --- ---- ___ ___ ___ X _____________ --- ---- _____________________________________________________ _ Scaphopod, undertermined ______________________ --- --- ____ ___ ___ ___ X _____________ --- ---- ______________________________ --· ____________________ _ 

Gastropoda: 

~ir:r::!; ;~~:~~--~~============= === ::: ::: ::: ::: ::: ::: :::: ::: ::: -~ ::: === ::: :::: ::: ::: :::: ::: ::: ::: === ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ·x ::: ::: ::: 

A mauropsis palu.dinaejormis (Hall o 

and Meek)--------------------- --- _________ --- --- --- ---- ___ ___ X X ___ --- ---- ___ --- ---- ___ --- ______ --- ______________________________________ _ 

Anchura? SP----~----------------- --- --- --- --- --- --- --- ---- --- --- --- --- --- --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- Drepanochilus nebrascensis (Evans 

ans~~~~-~~_r~)-~=::::::::::::::: ::: ::: ::: ::: ::: ::: ::: :::: ::: ::: ::: ::: ::: ::: :::: ::: ::: :::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: T ::: ::: ::: Aporrhais meeld Whitfield _______________________ --- --- ---- _______________ --- ____ --- --- ---- _____________________________________________________ _ 

Piestochilus Gastropod, SP-------------------- --- --- --- --- --- --- --- ---- --- --- --- --- --- --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- ·-- --- --- --- --- --- --- --- undetermined _______________________ --- --- ---- ___ ___ ___ X _____________ --- ---- ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ ___ X _____ _ 

Cephalopoda: Baculites obtusus Meek __________________________ --- --- ---- _________________________ --· ---- _______________________________________ ••• ___ ••• ___ ••• 

~~~-i{~~~~l~;itkb.e(i"~eiitei-5: ::: ::: ::: ::: ::: ::: ::: :::= ::: ::: ::: ::: ::: ::: :::: ::: ::: :::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: gregorvensis Cobban __________ --- ____________ --- --- ---- ______ --- ______ --- ---- ___ --- ---- _____________________________________________________ _ scotti Cobban_________________ X X X ___ X --- --- ---- ______ --- --- ___ --- ---- --- --- ---- _____________________________________________________ _ crickmayi Williams ___________ --- ___ ___ ___ ___ X --- ---- ______ --- ______ --- ---- ___ --- ---- _____________________________________________________ _ 

~~~~f~o~~~~~~:::::::::::::: ::: ::: ::: ::: ::: ::: ::: :::: ::: ::: ::: ::: -~ -~ :::: -cr" -ci :::: ::: ::: ::: ~== ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: 

~ff:o1~b;~:i\~li~~~~~~======= ::: ::: ::: ::: ::: ::: ::: :::: ::: ::: ::: ::: ::: ::: :::: ::: ::: :::: -~ ::: -~ _: _:_ -~ _: ::: ·x ·x ::: ::: ·x ·x ·x ·x ::: ::: Exit~Pocera~-iennevi-(wiiiitieici)::: ::: ::: ::: ::: === ::: -~ --~ -~ ::: ~ ~ ·x ::: :::: ::: ::: --~ ::: ::: ::: ::: ::: ::: ::: -~ === ::: ::: ::: ::: ::: ::: ::: ::: _: Solenoceras mortoni (Meek and . 

Hayden) ••. ~------------------- --- --- --- --- --- --- X ---- --- --- X X --- --- ---- --- --- ---- --- --- --- --- --- ______ --- ______ --- --- --- --- --- --- --- ---

Oxybeloceras SP---------------------------- --- --- --- --- --- X---------- X-------------------------------------------------------------------------------- crassum (Whitfield) ________________ ---------- ______ --- _________ ---- ___ --- _________________________________________________________ _ 

SP---------------------------- --- --- --- --- --- --- --- X X --- --- --- --- X ---- --- • .:.. ---- --- --- --- --- --- --- --- --- --- ___ --- --- --- --- --- --- --· --- Didymoceras nebrascense (Meek and Hayden) __________________________________ X X---- ______ --- _________ ---- ___ --- _________________________________________________________ _ 

n. sp. (tightly coiled) _________ --- ___ --- ___ --- --- --- ---- --- --- --- --- ___ --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- ---

1!f~~;.~~~~~1~W~~~=~~~ Anapachydiscus? complexus (Hall ~~~ ~~ ~~~ ~~ =~ ~~~ ~~~ ;;~ ~~~ ~~~ ~~= ~~ ~~ ~~ ~~~~ m ~~~ ~:~ ~~~ ~=~ ~~~ m ~~= ~~ =~~ =~ ~~~ =~~ ~~~ ~~ ~~~ ~~~ :~ ~~ ~~~ i~~ Menuites, and Meek) _____________________ --- --- --- --- --- --- --- ---- --- --- --- --- --- --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- n. sp _________________________________ --- ___ ---- ______________________________________________________________________________________ _ 

Pachydisdd ammonite ___________ --- --- --- ___ --- --- --- ---- --- --- --- --- --- --- ---- --- --- ---- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- --- Placenticeras meeki Boehm _______ --- ____________ --- ___ ---- ______ --- ______ X ________________________________ ·-- ________________________________ _ 

intercalare Hayden) (Meek and ___________________ . _______________ --- ___ ---- _________ cf _________________________________________________________________________ _ 

sph:Eadiicua--si;_-:::::::::::::~: ::: ::: ::: ::= ::: ::: ::: :::: === ::: ::: ::: -~ ::: :::: ::: ::: :::: ::: ::: ::: ::: :::· ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ·x ::: ::: 

Crustacea: 

Arthropoda: Dalcoticancersp ___________________ --- --- --- ___ --- --- --- ---- --- --- --- --- --- --- ---- --- --- ---- --- --- --- --- --- --- ___ --- ______ --- ______ --- X------ __ _ Fish: 

~~~~~~~~t_e~-~~:-~~~~~~~:::::::::: ::: ::: ::: ::: ::: ::: ::: :::: ::: ::: -~ ~== =:: ::: :::: ~== ::: :::: ::: ::: ::: ·x ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ::: ·x Vertebra ________________________________________ --- --- ---- --- --- --- --- --- --- ---- ___ --- __________ --- ___ --- ______ --- ______ --- ______ --- ___ --- --- __ _ Teeth ___________________________________________ --- --- ---- --- ______ --- ___ --- ---- ______ ---- ______ --- ______ --- .. _ --- _______________ --- --- ___ --- X 

~etrified wood _______________________ ------------------------------------------------------------------------------------ ___ --------------------- X 
BEDROCK GEOLOGY 103 

~PABLE 3.-LithoZogy and faunal zones of the Pierre shale 

Height 

of top of 

unit 

Unit above 

base of Lithology Fossils 

section 

(foot) 

Shnlo, gray, clnyoy 5, 200 Contains phosphatic nodnnd silty ules and ironstone beds. 

Snndstono, shnly, olive-brown 

4, 700 Contains large calcareous Baculites clinolobatus, 

sandstone concretions. Inoceramus? fibrosus. 

Contains layers of cone- Baculites grandis from 

4,050 in-cone and aragonite, 4,050 to 3,900 ft. 

and ironstone concre- tions. 

3, 740 Contains brown limestone Inoceramus typicus at concretions. 3, 740ft. 

3,450 Blocky. Baculitea eliasi at 3,450 ft. 

3,115 Silty. 

2,800 Chalky; contains limeShnlo, olivo-gmy, stone concretions. 

clayey 2, 700 Contains gray limestone Placenticeras meeki at concretions. 2,530 ft. Exiteloceras 

jenneyi at 2,430 ft. 

2,200 Contains ironstone con- Didymoceras cretions. nebrascense 

Contains ironstone con- 2,150 cretions and has sandy shnle at top. 

1,825 Contains tepee buttes Baculites acotti. 

Shaly; contains thin, hard Anapachydiacus? com- ironstone layers and plexus, Menuites? n. 1, 775 concretions. sp. from 1, 775 to 

Hygiene sandstone 

1,575 ft.; Baculites 

acotti 1,575 to 1,400 

member, olive- ft. 

brown 

1,400 Shnly, platy, calcareous; contains tepee buttes 

and limestone beds in 

Baculites gregoryensis1 , 

Inoceramus aublaevas. 

upper part. 

1, 200 

Cnlcareous, blocky; con- tains clayey ironstone Baculites n. sp. from 

1,100 to 800 ft. 

concretions. 

Shale, ollvo-gmy, clayey Septarian limestone con- Baculites asperiformis. 000 crctions and siltstone 

beds. 

600 Silty, noncnlcareous. 

80 Calcareous, bentonitic. 

Anapaohydisous? o01hplewus (Hall and Meek) and 

M ewwites? n. sp. are 100 to 200 feet below the top of 

the sandstone. ' 

About 700 feet of olive-gray clayey shale overlies the 

I-Iygiene sandstone mem.ber. From 1,775 to 1,825 feet 

the shale contains tepee butte limestone masses more 

than 15 feet in diameter, and small oval gray dense limestone concretions. B aoulites scotti Cobban occurs 

abundantly in the small concretions and in the tepee 

butte limestone. The clayey shale above the tepee 

buttes frmn about 1,825 to 2,150 feet includes a thin belt 

of sandy shale covered by yuccas. From 2,150 to 2,200 

feet, Didyrnooe'l·as neb?·asoense (:~1eek and I-Iayden) is 

common in yellowjsh-orange ironstone concretions in the 

lower part and in gray limestone concretions in the 

upper part. From 2,200 to 2,700 feet above the base, 

gray limestone concretions are abundant in olive-gray 

clayey shale. Moderate yellowish-brown clayey ironstone nodules and thin layers of brown fibrous aragonite 

and cone-in-cone are scattered on the slopes overlying 

this part of the section. Large gray tepee butte limestone masses are found in this part of the 'section in the 

southern part of the area. Phosphatic nodules shaped 

like tear drops and dumbbells were noted about 2, 700 

feet above the base. Ewitelooeras jenneyi (Whitfield) 

and Baoulites n. sp. were found in limestone concretions 

at 2,430 feet above the base; at 2,530 feet the large ammonite Plaoentioeras meeki Boehm is abundant. 

Clayey shale constitutes the next 415 feet of strata 

from 2,700 to 3,115 feet above the base. From 2,700 

feet to 2,800 feet, gray hard dense limestone concretions 

occur in three or four layers in light olive-gray sandy 

chalky shale. They contain B aoulites oorrugatus Elias 

in the Littleton quadrangle but are too poorly exposed 

to yield fossils in the l(assler quadrangle. 

The overlying 315 feet of Pierre shale is poorly exposed in the northern part of the area and probably 

faulted out in the southern part of the area. An outcrop in the SW%,NWlt4 sec. 36, T. 6 S., R. 69 W., shows 

light olive-gray silty shale that contains moderate 

yellowish-brown concretionary ironstone layers and 

layers of pale yellowish-brown aragonite and yellowishgray cone-in-cone. 

Above 3,115 feet, the strata again become olive-gray 

clayey shale, and this lithology extends to 4,200 feet 

above the base. Ironstone concretions and small gray 

limestone concretions lie in a gray blocky clayey shale 

from 3,115 to 3,450 feet; at about 3,450 feet they contain 

Baoulites eliasi Cobban. Yellowish:brown limestone 

concretions in olive-gray clayey shale lie between 3,450 

and 3,740 feet. At about 3,740 feet in the zqne of Baoulites baoulus Meek and Hayden (tables 2 and 3), the 

concretions contain many small, sharply ribbed I noceramus typious (Whitfield). The shale is olive gray 

and clayey, and contains cone-in-cone layers, aragonite 

layers, and reddish-brown and black ironstone concretions from 3,740 to 4,050 feet. At 3,900 to 4,050 feet 

the ironstone concretions contain B aoulites grand is Hall 

and Meek. 

The upper part of the formation is dusky yellow or 

olive-brown shaly sandstone from 4,050 to 4,700 feet, 

and olive-gray clayey or silty shale from ·:1:,700 to 5,200 

feet-the contact of the Fox Hills sandstone. B aoulites 

olinolobatu8 Elias, the highest baculite, and Inooeran1u,s? fibrosrus (:Meek and I-Iayden), which are characteristic of the Mobridge member of the Pierre shale 

in South Dakota, lie in large gray calcareous sandstone 

concretions between 4,050 and 4,700 feet. Above the 

sandy beds, about 500 feet of blocky light olive-gray 

clayey shale contains ironstone nodules and layers (see 
104 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

stratigraphic sections 15 and 18). One of these layers, 

which, crops out in the NE1!.t,SE1,4 sec. 19, T. 7 S., R. 

68 W., and in the NE114,SW1!.t, sec. 29, T. 7 S., R. 68 W., 

is 27 feet thick and is composed of innumerable moderate yellowish-brown pea-sized limonite nodules and 

phosphatic pebbles. This layer lies about 290 feet below the top of the Pierre shale and is an excellent 

marker bed. Above the limonite layer is light olivegray silty shale and thin limestone interbeds, one of 

which contained. Yoldia evansi (Meek and Hayden) 

and comminuted plant fragments. 

15 .. Pierre sha.le on slope of pediment in the NEI4SWI4 sec. 

29, T. "'/ S., R. 68 W. 

Fox Hills sandstone. 

Pierre shale (part) : Feet 

4. Covered; partly sandstone and shale____________ 61. 0 

3. Limestone, yellowish-gray, blocky, dense, hard; 

contains plant fragments, Yoldia evansi·________ .- 5 

2. Covered; presumed to b(} olive-drab limonitic 

sandy shale __________________________________ 157.0 

1. Shale, moderate yellowish-brown, limonitic; limonite layers ; made of one-fourth in. limonite 

nodules and phosphatic pebbles as much as 2 

in. in maximum dimension, some of which 

are casts of mollusks, Baculites clinolobatu.s, 

GeUena SP----------------------------------- 27.0 

Measured thickness of Pierre shale ______________ 245. u 

The contact of the Pierre shale with the Fox Hills 

sandstone is so poorly exposed that its position could 

only be inferred from the texture of the overlying soil. 

The lithology in the contact zone is gradational ; therefore, the Pierre contact was placed at the top of the 

highest marine clay shale and the base of the lowest 

massive sandstone that contains large hard brown sandstone concretions. 

Phosphatic nodules are particularly abundant in the 

upper part of the Pierre. Beds of nodules lie in both 

of the upper two faunal zones. Good outcrops of the 

phosphatic nodule beds are in the NE1,4SW1!.t, sec. 18, 

T. 7 S., R. 68 W., in the SE1,4SE1,4 sec. 19, T. 7 S., R .. 

68 W., and. along the Jarre Creek fault in a slice of 

Pierre that is only 30 feet thick in the SWl!.t,SEl!.t, sec. 

32, T. 7 S., R. 68 W. The pebbles are rounded and 

abraded and include phosphatic casts of Geltena sp. 

and B aculites clinolobatus and teeth and bones of fish. 

Some pebbles ·have holes that were bored by worms on 

the floor of the ocean. 

The pebbles were analyzed chemically and by X-ray 

diffraction. J. P. Schuch of the U.S. Geological Survey found that the dull granular pebbles contain 12.4 

percent P 205 and the vitreous pebbles as 1nuch as 25 

percent P205. A. J. Gude 3d of the U.S. Geological 

Survey found by X-ray that th~ pebbles contain very 

abundant apatite and minor amounts of calcite and 

quartz. 

FOX HILLS SANDSTONE 

The Fox Hills sandstone (Meek and Hayden, 1862, 

p. 419, 427) of Late Cretaceous age is predominantly 

brackish-water marine sandstone. It is best exposed 

in the NE1!.t,S"T14 and the SE-%,N'Vl(t sec. 29, T. 7 S., 

R. 68 W., and in a gully in the SE%,SW1!.t, sec. -7, T. 

7 S., R. 68 W. (pl. 1). The exposed thickness of the 

formation is only 30 feet, but 155 feet of covered beds 

were included, and make a possible thickness of 185 

feet. Neither the lower nor the upper contacts were 

exposed. Stratigraphic sections 16 and 18 illustrate 

the lithology of the formation. 

The formation is divided into a lower sandy shale, a 

middle ridge-forming sandstone, and an upper soft 

sandstone. The lower part is mostly soft, olive-brown 

sandy shale that contains thin limy sandstone layers 

and carbonaceous plant fragments. The middle part is 

29 feet of olive-gray to yellowish-gray fine-grained 

massive to slabby sandstone. It is friable to hard and 

is thin bedded; in some places it is crossbedded in thin 

laminae. The sandstone is composed of subrounded 

quartz grains that are firmly cemented with calcium 

carbonate. Cone-in-cone layers lie between some of the 

sandstone layers. This middle part also contains darkbrown hard calcareous sandstone concretions as large 

as 4 feet in diameter. The upper part is almost completely covered, but probably is olive-brown or olivegray soft sandstone. A fe\v poorly preserved brackishwater pelecypods were found in the middle sandstone. 

The Fox Hills sandstone is a transitional deposit between the marine Pierre shale and the continental 

Laramie formation. The upper contact lies under a 

covered interval, below which is marine sandstone and 

above which is nonmarine sandstone and coal. 

16. Fox Hills sandstone on slope of pediment in the NEI4SW% 

sec. 29, T. "'/ S., R. 68 W. 

Fox Hills sandstone (part) : Feet 

5. Sandstone, olive-gray, nodular, limonitic; contains 

laminated clay balls; fine-grained; 1 ft. slabby 

sandstone at tOP----------------------------- 8.0 

4. Covered ; probably shale with cone-in-cone layers_ 5. 0 

3. Sandstone, yellowish-gray, massive, fine-grained_ 1. 0 

2. Covered; may be soft sandstone_________________ 12. 0 

1. Sandstone, yellowish-gray, slightly crossbedded, 

friable, fine-grained__________________________ 3.0 

Measured thickness of Fox Hills sandstone______ 29. 0 

LARAMIE FORMATION 

The Laramie formation (King, 1876) of ·Late Cretaceous age is predominantly fresh-wate.r siltstone, 

claystone, sandstone, and coal. The best outcrops are in 
BEDROCK GEOLOGY 105 

the center of sec. 29, T. 7 S., R. 68 W., and at the Lehigh 

Mine along the west border of see. 20, T. 7 S., R. 68 ,V., 

and in sec. 7, T. 7 S., R. 68 W., but the formation is 

generally covered. The basal contact is not exposed; 

the upper contact is well exposed at the localities listed 

above. 

The formation is about 660 feet thick and consists of 

light olive-gray and pale yellowish-brown clayey shale, 

yellowish-gray friable well-graded sandstone, moderate-brown hard limonitic sandstone, moderate-brown 

hard limonitic conglomerate, white clean friable 

conglomern,te; and brownish-black lignitic coal beds 

ranging in thickness from 0 to 6 feet (see stratigraphic 

sections 17 and 18) . The sandstone and fine-grained 

conglomerate beds consist of medium-grained clean 

angular to subrounded .quartz sand that is loosely compacted and cemented by calcium carbonate or silica. 

The mnny concretions and concretionary layers are 

concentrically banded and range from % inch to 4 

feet across. 

17. La:ra:mie fo?·mat-ion on slope of pediment in the NEJ4SWJ4 

sec. 29, T. 7 S., R. 68 W. 

Laramie formation (part) : Feet 

Upper part covered. 

10. Sandstone, moderate-brown, shaly, hard, limonitic; leaf impressions------------------------- 1. 5 

9. Covered; limonitic friable sandstone; concretions 

on surface---------------------------------- 75.0 

8. Sandstone, yellowish-gray, massive, soft, friable; 

contains nodules and layers of dark yellowishornnge sandstone____________________________ 1. 7 

7. Coal, grnyish-blacl.:, soft, lignitic_______________ . 2 

6. Sandstone, pinkish-gray, soft, friable, finegrained------------------------------------ 2.8 

5. Coal, brownish-black, sofL-------'------------- . 6 

4. Shale, pale yellowish-brown, silty-------------- 7. 6 

3. Coal, brownish-black, peaty, soft, impure_______ 1. 6 

2. Sandstone, yellowish-gray, soft, friable, mediumgrained------------------------------------ 25.0 

1. Covered ; may be shale ; may be partly Fox Hills 

sandstone---------------------------------- 155.0 

~lensul'ed thickness of Lnramie formation _______ 271. 0 

lK /Jaw::WI/. urkOi:iC. Larau1ic formation, Po.r Hills ~Sandstone,. 

li'IHI Pi('rrc ::rhale in. a·rroyo ·i·n tlw NW1J~ SWJ4 sec. 20, T. "1 S., 

R. G81V. , 

[l\lcnsliJ'Cd by G. R. Scott and Richard Vnn Horn. Clay mineral ldent:iflcntlon br A . .T. Gude ;jd, USGS lahoratorr serial number llsted after 

cltt~· mineral. Samples collected· by Hichard Vnn Horn] 

Dnwson arkose (part) : Feet· 

33. Conglomerate, arkosic; has dark yellowish-orange 

ana black clay at base; base covered; montmorillonite (204714) ------------------------ 100. 0 

32. Covered-------------------------------------- 28.0 

Measured thickness of the Dawson arkose ________ 128. 0 

18. Dawson arkose, Lara·mie formation, Fox Hills sandstone, 

and Pierre shale in arroyo in the NW%SWJ4 sec. 20, T. "1 S., 

R. 68 W.-Continued 

Laramie formation : 

31. Conglomerate; very light-gray; predominantly 

dark-gray and red chert_ ___________________ _ 

30. Clay, medium-gray; montmorillonite (204715) __ _ 

29. Conglomerate; predominantly dark-gray and red 

chert; upper half very light gray, lower half 

yellowish brown; montmorillonite (204716) __ _ 

28. Shale, medium-gi.·ay ; becomes very sandy and 

light gray in upper 4 ft.; montmorillonite 

(204717) ----------------------------------- 27. Conglomerate, yellowish-brown; predominantly 

dark-gray chert; some red chert_ ____________ _ 

26. Shale, medium-gray; montmorillonite (204718) __ 

25. Sandstone, light-gray, friable, medium-grained; 

some iron stains; kaolinite (204719) --------- 24. Shale, medium-gray; base covered _____________ _ 

23. Sandstone and shale, gray to buff _____________ _ 

22. Sandstone, light-gray, medium-grained, ironstained; few pea-sized iron concretions; few 

lea.f prints; kaolinite (204720) ---------------

21. Sandstone and shale, gray and buff ____________ _ 

20. Shale, medium- to dark-grny, kaolinite (204721) _ 

19. Sandstone, light-gray, iron-stained, crossbedded, 

medium-grained ---------------------------- 18. Shale, medium-gray; upper part dark-brown and 

carbonaceous; montmorillonite (204722) ------

17. Sandstone, light-gray, fine-~rained ________ ._ ___ _ 

16. Shale, dark-gray, carbonaceous _______________ _ 

15. Sandstone, light-gray, iron-stained, mediumgrained; kaolinite (204723) -----------------

14. Sandstone and shale, gray and buff ___________ _ 

13. Sandstone, light-gray, medium-grained; kaolinite 

(204724) -----------------------------------

12. Coal ----------------------------------------

11. Covered ------------------------------------- 10. Snndstone, light-gray, medium-grained; kaolinite 

(204725) ----------------------------------

lOa. Covered ---------------------------·---------

Feet 

1.0 

.2 

.9 

18.0 

3.0 

7.3 

3.0 

2.0 

273.0 

6.0 

32.2 

4.0 

1.0 

10.5 

1.6 

1.0 

3.3 

52.0 

2.0 

6.0 

42.0 

4 .. 0 

64.0 

Thickness of Laramie formation _________________ 538. 0 

Fox Hills sandstone : 

9. Covered ------------------------------------- 80. 0 

8. Shale, medium-gray, clayey, montmorillonite 

(204726) ---------------------------------- . 6.0 

7. Covered -------------------------------------- 98. 0 

Thickness of Fo~ Hills sandstone----------------. 184. 0 

Pierre shale (part) : 

6. Shale, light olive-gray, very silty; contains DisoosoazJhites sp. Contains sandstone layers, 

fine-grained, loose, as much as 1.5 ft. thick, 

montmorillonite (204727-8) ------------------ 163. 0 

5. Limestone, brown; plant-fossil layer____________ . 1 

4. Covered ------------------------------------- 72.0 

3. Shale, light olive-gray silty; thin limestone layers, limonite nodules, and limestone nodules; 

montmorillonite (204729) -------------------- 54. 0 

2. Limonite nodules, phosphatic nodules, and shale; 

brown; montmorillonite (204730) ------------ 27. 0 

1. Shale, light olive-gray, silty, partly covered; 

montmorillonite (204731) -------------------- 100. 0 

:\leasured thickness of Pierre shale ________________ 416. 1 
106 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

The thin sandstone and conglomerate beds are lenticular; the thick shale beds are persistent and regular 

in thickness. Bedding planes are fairly even in the 

thick sandstone beds, which commonly part along layers of heavy minerals. Bedding planes are undulatory 

in the shale, and occur along layers of carbonaceous 

material. 

Abundant leaf prints lie along the bedding planes of 

sandstone and ironstone beds near the top of the formation. R. W. Brown identified several Upper Cretaceous leaves frmn an ironstone bed at loc. 85 about 

125 feet below the top of the Laramie formation, in the 

SE1(NvV~ sec. 29, T. 7 S., R. 68 W. They are: Ficu8. 

ctre[~-acea Lesquereux, F. planicostata Lesquereux, F. 

trinervis l{nowlton, Anona robu.rsta Lesquereux, and 

Dombeyopsi.(] sinuata Knowlton. 

DAWSON ARKOSE 

The Dawson arkose (Richardson, 1912, p. 267-276) 

of Late Cretaceous and Paleocene age, which consists of 

conglomerate, sandstone, siltstone, and claystone, underlies almost 18 square miles of the east part of the 

quadrangle (pl. 2) . The conglomeratic lower part of 

the Dawson forms local ridges (fig. 32); the upper part 

forms brl,lsh-covered badlands. The thickness of the 

Dawson is about 1,450 feet; of this, approximately the 

lower 500 feet has been assigned on the basis of fossils 

to the Cretaceous by Brown ( 1943). The Cretaceous 

part of the formation dips northeast ·at 50° or more. 

The dip decreases upward in the section, but 400 feet 

above the base of the Tertiary or 900 feet above the base 

of the Dawson it is still at least 12°. 

Eldridge ( 1888, p. 97) proposed the name Willow 

Creek beds and, later, Arapahoe formation for the 600 

to 1,200 feet of beds cropping out "from 1 to 3 miles 

southeast of the mouth of Platte Canon, where it has 

its greatest and most typical development." This includes almost the entire section between the Laramie 

formation and the Castle Rock conglomerate, but these 

beds are here called Dawson arkpse because by previous 

usage the name Ara'pahoe has been restricted to beds 

that underlie the Denver formation in the Denver area. 

The Dawson arkose in the Kassler quadrangle consists of light-gray, yellowish-gray, moderate-brown, or 

pale reddish-brown conglomerate (see section 18), 

sandstone, and clayey shale; the clayey shale contains 

some green beds and lenses of brownish-black lignitic 

coal. The lower part of the Dawson is characterized 

by conglomerate, the upper part by shale. Bedding is 

irregular, most beds being curved and lenticular. Individual beds range in thickness from 0 to 200 feet; 

conglomerate beds are the thickest. Shale beds have 

been thinned and highly contorted by compression during lithification. Channel-and-fill crossbedding is 

pronounced. 

Granitic fragments are abundant in the conglomerate, 

quartz is common, and chert, rhyolite, quartzite, sandstone, petrified wood, chalcedony, and scoria occur in 

minor amounts. The greater part of the material consists of pebbles 14 to 1 inch in diameter. Lesser 

amounts of sand and cobbles, as much· as 6 inches in 

maximum dimension are present. Biotitic olive-gray 

clayey shale is common. Because of the fluvial origin 

of the formation, vertical variations in grain size are 

extreme. Most of the grains are subrounded, unpolished, alid are loosely compacted with much pore space. 

The grains are cemented with calcium carbonate, silica, 

opal, or iron oxide. Local increases in silica cement 

result in quartzite beds, as at Wildcat Mountain, the 

highest point east of the mountains in this quadrangle. 

Alteration of feldspar to kaolinite has caused the basal 

conglomerate to become nearly white. 

Leaf prints are the only fossils found in the Dawson 

arkose of this area. Platy sandstone beds that are cemented· by iron oxide are the best source of fossil-leaf 

prints in the Dawson arkose. The iron oxide may have 

been altered from iron sulfide that was deposited under 

swampy conditions. R. W. Brown (written communication, 1950) identified two species of Upper Cretaceous 

leaves, Ficus planicostata Lesquereux and F. trinervis 

Knowlton, from the lower part of the Dawson arkose at 

loc. 86 in the NW14SE%, sec. 29, T. 7 S., R. 68 W. 

Paleocene leaves were collected by Arthur Lakes of the 

Colorado School of Mines and later by Brown ( 1943, 

p. 73) from a gully in the SE14NW14 sec. 20, T. 7 S., 

R. 68 W. The Paleocene leaf Rhamnus goldianus Lesquereux was found in ironstone in the SE14SW14SE1)a, 

sec. 30, T. 6 S., R. 68 W. 

INTRUSIVE DIKE ROCKS 

Two intrusive dike rocks were mapped. One is andesite, which crops out in small bodies throughout the 

mountains. The other is rhyolite, which crops out at 

only one place west of Roxborough Park. 

ANDESITE 

Andesite of Late Cretaceous ( ~) age crops out as dikes 

in the western one-fourth of the quadrangle (pl. 2). 

The dikes are poorly exposed because of a cover of 

surficial material and. vegetation and most of them were 

mapped on the basis of float. They are discontinuous 

lens- to tabular-shaped bodies that range in length 

fron1 25 feet to 1 mile and in width from 1 to 10 feet. 

They range in thickness from 1 inch to 10 feet. The 

wallrocks are metasedimentary and granitic rocks. The 

dikes that intrude northwest-trending faults are nearly 
BEDROCK GEOLOGY 107 

vertical; the dikes that intrude northeast-trending 

faults are nearly horizontal. 

The andesite is pale brown, olive gray, or black. It 

weathers to dark gray or brownish gray. The texture 

is generally microporphyritic, but a few megaporphyritic dikes were see.n. ~fost of the feldspar phenocrysts 

n,re smal1er than 2 mm in length and are alined in a 

flow structure that is parn,llel to the walls of the dike. 

Average composition of the andesite is 50 percent pyroxene, 40 percent andesine, and 10 percent magnetite. 

The magnetite alters to limonite. 

In thin section the andesite is composed of a groundmass of andesine crystals set in a cryptocrystalline mass 

that appears to be altered basaltic glass (petrography 

based mostly on an examination of thin sections by R. 

E. "\Vilcox, of the U.S. Geological Survey). The 

groundmass texture is felted. The felted andesine 

crystals have a composition of An 33-36 in the centers 

and An :.! 7-ao in the rims. Andesine phenocrysts as large 

as 2 mm in lengtll" are set in the groundmass and have a 

composition of An 45_48 • The phenocrysts are twinned 

according to both the albite·and the carlsbad laws and 

some of them. are curved. The rock is crowded with 

opaque skeletal growths of magnetite. l{nots of cordier.ite were seen scattered through the andesite. The 

cordierite has inclusions of magnetite; and it may have 

for1ned from clayey inclusions of fault gouge picked up 

by the andesite during intrusion. Most of the andesite 

is lacking in ferromagnesian minerals, but one specimen 

contained !50 percent pyroxene as groundmass and another about 10 percent hornblende as phenocrysts. Pyrite was seen in one dike that cuts amphibolite. 

The andesite in the northwest-trending faults was 

intruded into fault gouge and was brecciated by later 

faulting. The dikes are lenticular and continuous. 

The andesite in the northeast-trending faults was intruded into almost horizontal fractures that contain 

little if any fault gouge. They are tabular and discontinuous, n.re jointed perpendicular to the walls, and 

occur in very small lenses. 

The andesite probably correlates with group 1 of the 

intrusive rocks of the Front Ra.nge mineral belt described by Lovering ( 1935, p. 30). · Lovering stated 

that group 1 is later in age than the Late Cretaceous 

Lara.mie formation and older than the Laramide revolution. These dikes may be part of the body of andesite 

that was eroded and deposited in the Denver forma.tion 

and in the Drt wson arkose; therefore the dikes could be 

as old as Late Cretaceous. 

RHYOLITE 

A small weathered body of rhyolite of Paleocene(?) 

age crops out in the NEl)J,SE%, sec. 15, T. 7 S., R. 69 W. 

(pl. 2). The rock probably was intruded into the 

granite gneiss along a fault or fracture, which now is 

covered by the deeply weathered rock in the area of its 

outcrop. The rock is micro porphyritic; the groundmass, which constitutes 91 percent of the rock, is a 

crystalline aggregate of potassic feldspar and quartz; 

the phenocrysts which constitute 7 percent of the rock 

are anorthoclase. Traces of plagioclase., biotite, magnetite, and microcline are present. Flow lines of feldspar crystals are weakly formed in the rock. 

STRUCTURE 

The rocks of the Kassler quadrangle have been affected by diastrophism at least six times. The earliest 

and most severe was the Precambrian metamorphism 

of a series of limestone, shale, and sandstone deposits 

that now constitute the metasedimentary rocks. The 

second was later in Precambrian time when the biotitemuscovite granite and all earlier rocks were subjected 

to cataclastic deformation. The third was in latest 

Precambrian time when mountains were slightly raised 

and a system of northwest and northeast-trending 

faults was formed. The fourth time was in the Early 

Pennsylvanian when the ancestral Rockies were uplifted and the Precambrian faults were locally ·reac-

.tivated. The fifth time was in the Laramide Revolution when the Rocky Mountains were formed; the Precambrian faults were again reactivated and some new 

faults were formed in both the crystalline rocks and in 

the sedimentary rocks. The sixth and last time was in 

late Pliocene time when the Rocky Mountains were uplifted slightly. 

PRECAMBRIAN STRUCTURE 

Precambrian diastrophism can be divided into seven 

episodes that eventually resulted in the formation of a 

thick mass of banded metasedimentary rocks and three 

intrusive bodies. Recrystallization and deformation 

was the first episode of a long cycle of metamorphism 

that fonned .. rocks of varying composition. A second 

episode of metamorphism was the metasom~tism of the 

recrystallized sedimentary rocks to produce the granite 

gneiss and migmatite; the third episode was further 

metasomatism and plastic flow of the foliated rocks 

caused by intrusion of the gneissic granite. The fourth 

episode was intrusion of the biotite-muscovite granite 

which may be a late phase of intrusion of the gneissic 

granite. The fifth episode was the cataclastic deformation of all rocks of the age of the biotite-muscovite 

granite and earlier. The sixth episode was the intrusion of the Pikes Peak granite, which, although it is the 

largest batholith in the Front Range, has produced only 

slight metan1orphic effects in the foliated rocks. The 
108 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

seventh episode was slight uplift and faulting of the 

. Precambrian rocks. 

FAULTS 

Faults that are inferred, from the presence of dikes 

of sandstone, to be of Precambrian age, lie along major 

fault zones in the southwest pttrt of the quadrangle. 

These faults trend north or northwest and contain 

cemented breccia. Most of them were truncated or abut 

against later sedimentary rocks. The attitude of the 

faults is nearly vertical and some cross each other or 

branch. Thick layers of gouge can be seen along the 

larger faults, but the smaller ones contain only sandstone dikes. The larger faults also have been intruded 

by andesite dikes and, as indicated by brecciation of the 

dikes and sandstone, have been active several times since 

Precambrian time. 

FOLDS 

Most of the Precambrian folds in the area are either 

tight and asymmetrical or isoclinal and overturned. In 

an area about a mile southwest of Kassler a group of 

smaller folds can be studied in excellent outcrops. The 

folds are tight and the distance between the crest of 

an anticline and the trough of a syncline does not 

exceed 75 feet. Drag folds of many sizes can be me.asured on the flanks of the larger folds and all the drag 

folds are similar to the large folds in bearing and 

plunge. Broad arcuate patterns of some of the rock 

units in the southern part of the area outline some 

larger open folds. 

The lineations that were measured on folds and minerals in the area were plotted on the lower hemisphere 

of a Schmidt equal-area net. Concentrations of poles 

on the net were then contoured to show the average 

bearings and plunges of the folds. The resulting diagram (fig. 33) shows concentrations of poles at 38° N. 

80° W., 65° N. 20° E., 35° N: 25° W., and 45° N. 85° E. 

The 38° N. 80° W. fold is considered to be the ma.jor 

fold axis b1 and the 65 ° N. 20° E. fold is considered to 

represent the crinkles, ~, on the flanks of the major 

fold. The major fold is an isoclinal fold overturned 

toward the southwest. As shown on figure 33, no lineations ha.ve a southwest bearing, but many have a northeast bearing which indicates that the fold limbs generally dip to the northeast. 

Minor folds were observed in the NWlit, sec. 3, T. 7 

S., R. 69 W., that are imposed on the flanks of the major 

folds. The be.aring of these minor folds is about 30° to 

40° more northerly than the major folds. One of the 

concentrations of poles on figure 33 is at 35° N. 25° W. 

and may indicate a minor fold system. 

The bends in the ridges that trend northwest in the 

center of sec. 33, Nlh sec. 34, and NW cor. sec. 35, T. 

7 S., R. 69 W. (pl. 2), probably resulted from broad 

N 

0 

FIGURE 33.-Contour d.iagra·m of lineations, lower hemisphere plot of 52 

poles. b11 major fold axis ; a1 , axis of crinkles on major fold. Contoured on number of! poles. 

northeast-plunging folds of the rocks formed before 

the intrusion of the biotite-muscovite granite, inasmuch 

as some small bodies of the granite are intruded along 

the fold axes. 

PENNSYLVANIAN STRUCTURE 

· Mountains of Pennsylvanian age rose in about the 

·same position as the north end of the modern Front 

Range. Along the east margin of the Front Range 

north of Perry ·Park, which lies 4 miles south of the 

quadrangle, pre-Pennsylvanian sedimentary rocks are 

absent and Pennsylvanian arkose rests on Precambrian 

rocks that locally are deeply weathered. Pebbles of 

cherty Mississippian rocks in the basal layers of the 

arkose indicate that a once continuous layer of Mississippian limestone was stripped off in Pennsylvanian 

or pre-Pennsylvanian time. The lack of pre-Pennsylvanian rocks in the quadrangle indicates that the front 

of the ancestral Rockies was slightly east of the present 

east edge of the Front Range. 

The history of Pennsylvanian diastrophism in the 

Kassler quadrangle, which began with uplift, is as follows. The p"re-Pennsylvanian rocks were stripped from 

the Precambrian rocks as the ancestral Rockies rose, 

and the mountains were reduced to a gently sloping 

surface. A minimum of 140 feet of uplift (the thickness of marine pre-Pennsylvanian rocks at Perry Park) 

was required to expose the Precambrian rocks at sea. 
BEDROCK GEOLOGY 109 

level in Pennsylvanian time. The Pi·ecambrian .rocks 

were ";eathered and eroded, and the Fountain formation then was deposited on the gently sloping Precambrin.n rocks in the Pennsylvanian period. The ancestral 

R.ockies must have been lowered, not simply eroded off, 

to explain the encroachment of the Permian sea, for 

the Fountain arkose has not been eroded, though it was 

originally deposited above sea level. 

LARAMIDE STRUCTURE 

The R.ocky Mounta.ins are the result of the La,ramide 

period of mount.a in building in Late Cretaceous rtnd 

early Tertiary time. The magnitude of the Laramide 

force is shown by the present height of the mountains--

more than 25,000 feet of arching at the center of the 

Front H.n.nge and about 17,000 feet on the flanks at the 

contact of the sedimentary rocks and the crystalline 

rocks. 

FAULTS 

Faults of four types are recognized that are related 

to faulting, intrusion, or mineralization during the 

Laramide Revolution: 

1. Reactivated northwest-trending Precambrian faults 

that contain cemented breccia, sandstone dikes, and 

andesite dikes. A thrust fault along the mountain 

front is included in this type. 

2. Northwest-trending Laramide faults with uncemented iron-stained fault breccia. 

3. Almost flat, west-trending north-dipping Precambrian faults with thin layers of fault gouge, mineralized probably in Laramide time. 

4. Almost flat, west-trending north-dipping faults with 

andesite dikes. 

Laramide movement along the Precambrian faults is 

indicated by the brecciation of both the sandstone and 

the andesite. The amount of movement and brecciation 

was slight compared to the brecciation along the faults 

prior to the injection of the sandstone and andesite. 

The Jarre Creek fault is a high-angle branching reverse fault that cuts the sedimentary rocks in the south 

end of the quadrangle (pl. 2). It dips steeply to the 

west and throws flat-lying Dawson -arkose against the 

crystalline rpcks near the 'mouth of J arre Creek (fig. 

34). Just south of Jarre Creek, the fault twisted a 

large mass of Dawson arkose upward in a hingelike 

movement. The arkose crops out with vertical dips as 

a high ridge called Bee Rock. Outcrops of Dawson 

north and south of Bee Rock are nearly horizontal, as 

though they are separated by tear faults from the high 

ridge. Just northwest of Bee Rock, the rocks apparently were intensely brecciated, for no rocks crop out 

ttnd that area is now occupied by landslides. Toward 

the north, the fault cuts across the older sedimentary 

rocks and branches into several faults (pl. 2), one in the 

Fountain formation and the others in the Pierre shale, 

which is thinned and its bedding twisted by the fault. 

Slices of more resistant beds lie along the eastern 

branches of the fault. Far~ther north, the fault gradually cuts across younger rocks and cannot be recognized beyond sec. 18, T. 7 S., R. 68 W., where it 

apparently cuts the Fox Hills and La.ram ie forma,tions. 

The fault trends south ·to Perry Park where it is dissipated in bedding faults. Farther south the trend is 

taken up by another reverse fault that continues south 

to Colorado Springs. The J arre Creek fault probably 

formed during Precambrian time, inasmuch as between 

Bee Rock and Perry Park sandstone dikes can be seen 

at many places in the J arre Creek fault and in smaller, 

probably related fractures in the Pikes Peak granite. 

A branch of the Jarre Creek fault follows the Fountain formation north from J arre Creek. The thinness 

of the formation between J arre Creek and Roxborough 

Park is due to deletion of beds along the J arre Creek 

fault. The eastward bulging of Precambrian rocks at 

Jarre Creek was the result of great compressive stress 

and apparently localized the fault. Beds in the Fountain formation slid along each other in bedding faults, 

and a 3-mile-long outcrop was faulted to about twothirds its original thickness. Apparently the lower part 

of the Fountain formation was removed by the bedding 

faults. As beds in the upper middle part of the Fountain are traced south from l(assler to the south end 

of Roxhorough Park (fig. 32) they gradually swing 

west toward the Precambrian rocks and then disappear 

in a belt that apparently contains the crushed fragments 

of the lower part of the Fountain formation. Several 

small areas of the Fountain formation one-half mile 

north of Jarre Creek have been stripped bare of the 

overlying pediment gravel in a search for minable deposits of uranium. The Fountain formation there is 

not only severely crushed but contains many faults with 

reddish-gray slickensided clayey fault gouge. The 

fault continues north through RoX!borough Park where 

it gradually slices higher into the middle part of the 

Fountain formation and leaves the lower part unfaulted 

1 mile south of the South Platte River. It crosses the 

river west of. Kassler and apparently joins a northwesttrending fault in the Precambrian rocks that offsets 

the mountain front one-half mile north of the quadrangle boundary. 

A few northwest-trending near-vertical faults were 

seen that contain shattered rock, stained deep maroon 

by hematite. The shattered rock is not recemented and 

does not contain milky quartz like the Precambrian 

faults. These iron-stained faults are interpreted as 

Laramide in age. A good example is the fault in the 

center of sec. 5, T. 8 S., R. 68 W. 
110 GEOLOGY OF THE KASSLE R QUADRANGLE, COLORADO 

FIGURE 34.-Jarre Creek fauU. Daw.son arkose is faulted against cry.stalline rocks. The low tree-covered mountains on left are composed of 

Pikes Peak granite ; the higher, almost bare mourutalns on rigM are composed of foliated crystalline Docks. ..,.:

Mineralized west-trending Precambrian faults that 

dip 27° N.W. were seen along the South Platte River 

(pl. 2) and in a few other places where the rocks are 

well exposed. The fault gouge in them is, generally 

less than 3 feet thick, is lenticular, and is locally 

mineralized. Another flat-lying set, into which andesite of Cretaceous ( ~) age was intruded, apparently 

was formed in early Laramide time, for the andesite 

in these faults is not brecciated. 

A few north-trending near-vertical fau,lts with displacements of less than 1 foot were seen in the Lytle, 

South Platte, and Lyons formations. One of these in 

the Lyons sandstone is in the NW1;4SW1;4 sec. 30, T. 

7S.,R.68W. 

FOLDS 

The Front Range anticline is the largest and most 

spectacular fold in the area. The truncated hogbacks 

are remnants of a blanket of sedimentary rocks that 

originally lay over all the crystalline rocks in the quad-
BEDROCK GEOLOGY 111 

rangle. The sedimentary rocks now dip northeast in 

a monocline off the Front Range. In general, the 

steepest dips are related to the ,J arre Creek fault in 

the southern part of the area. One mile northeast. of 

.Tarre Creek at "'ildcat ~fountain the Dawson arkose is 

almost vertical. South of 'Vildcat ~fountain the upper 

part of the Dawson arkose gradually flattens to 6°. 

Most of the older strata along the fault zone also dip 

vet:y steeply northeast or are overturned to the southwest. In the northern pa.rt of the area the rocks dip 

60°-70° NE. D.ips in the Pierre shale are variable,· 

partly because of the influence of the Jarre Creek fault 

and partly because of slippage over each other of the 

soft shale layers at the time of uplift. 

Uplift of mountains in Pennsylvanian and Laramide 

time tilted the overlying blanket of sedimentary rocks 

t,,rice. The amount of tilting in Pennsylvanian time 

can only be guessed, but tilth1g in Laramide time is 

known to be more than 50° (fig. 35). The tilting certainly was not confined to the sedimentary rocks but 

involved also the uppermost of the underlying PreC!l.mbrinn rocks. All planar and linear elements that 

were part of the internal structure of the Precambrian 

Pre-Pennsylvanian rocks 

1. Pre·Laramide time showing uplift of Pennsylva·nian age 

2. Post-Laramide time 

Not to scale 

FIOUHE 35.-Simplltle<l hypothetical cross section of Front Range showing tiltlng of pr('·Lnrnmi<le structural features and formation of border 

tuults. 

rocks were· reoriented. How far this reorientation extends into the center of the mountains was not deiermined, but rocks throughout the Front Range may be 

affected to some extent. Interpretation of the original attitudes and significance of Precambrian internal 

structures is made complicated, if not impossible, by 

the tilting. 

In order to determine the effect of tilting, the attitudes of pre-Laramide rocks were reconstructed by 

rotating out the 60° to 70° of dip now shown by the 

sedimentary rocks. Sedimentary structures indicate 

that the Fountain formation was originally deposited 

on a surface that sloped about the same as the Pleistocene pediments (about 2° E.) and that this surface was 

tilted to about 60° or 70° during the Larall)ide uplift. 

The internal structures of pre-Laramide rocks near the 

~nountain front also were rotated 60° to 70°. Structures in the crystalline rocks that were parallel to the 

mountain front had a change of dip only; structures 

that were not parallel had a change of both trend and 

dip. The amount of tilting was determined on several 

Precambrian structures where both trend and dip were 

changed. A Precambrian fault that now is a reverse 

fault was originally formed as a normal fault. A 

Precambrian fold that now has a gentle plunge to the 

west originally plunged nea.rly vertically. 

Presumably the amount of rotation would be greatest 

at the east and west fronts of the range, and, unless the 

whole range was tilted as a block, would decrease to 

zero somewhere near the center. The outcropping preLaramide rocks on the west flank of the Front Range 

dip about the same as the rocks on the east flank; therefore I infer that the range rose nearly v~rtically and 

that the tilting on the two sides is nearly symmetrical. 

The rotation may have been evenly spread between the 

center and the front of the range, but it seems more 

likely that the rotation was concentrated in a narrow 

strip near the front. Small faults and shear zones may 

have absorbed most of the tilting within only a few miles 

of the mountain front. 

Figure 35 shows my the.ory of the effect of tilting on 

the faults along the east and_ west flanks of the Front 

Range. Most of the fracturing and reorientation caused 

by uplift of preexisting structures I believe was concentrated along the edges of the crystalline mass. 

Tension fractures probably opened between the large 

shear faults in the center of the range. 

HISTORY OF LARAMIDE STRUCTURE 

The uplift of the Rocky Mountains started far to the 

west near the end of Pierre shale (early Maestrichtian) 

time, but the sea covered the l{assler quadrangle until 

the end of Fox Hills (late Maestrichtian) time, when it 

withdrew from the area. The uplift of the mountains 
112 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO . 

apparently progressed slowly eastward. Active uplift 

of the present Front Rar1ge began in early Dawson 

(Danian~) time. The Precambrian rocks were arched 

as they were pushed up, and the sedimentary rocks on 

the flanks slid over the Precambrian rocks or over each 

other along preexisting faults. The eastern flank of the 

Front Range probably remained stationary because of 

deeply buried northwest-trending faults of Precambrian 

age that were .reactivated in Laramide time. Steeply 

dipping Precambrian faults that now lie along the eastern flank of the Front Range apparently were gently 

dipping normal faults (fig. 35) prior to the Laramide 

uplift. 

The complex history of faults in the quadrangle is 

well exemplified by that of the northwest-trending 

fau~ts, whose history started in Precambrian time. 

Their history is believed to be: 

1. The northwest-trending faults were formed and 

mountains uplifted in late Precambrian time after 

the intrusion of the Pikes Peak granite. 

2. The land that .rose in the la;te Precambrian diastrophism was eroded during Early and Middle 

Cambrian. 

3. The sea encroached in Late Cambrian time and deposited part of the sand of the Sawatch quartzite. 

4. Fractures were reopened along the northwest-trending faults during a minor Late Cambrian 

diastrophism or earthquake, and the unconsolidated sand about 15 feet above the bottom of the 

sediments on the floor of the Sa watch sea was 

injected into the fractures or was sucked in by 

vacuum, and apparently filled even the smallest 

of voids. 

5. The sand was indurated. 

6. The faults may have been reactivated in the Pennsylvanian orogeny. 

7. Andesite was intruded into the faults in Late Cretaceous ( ? ) time. 

8. The mountains were uplifted, the sedimentary .rocks 

were tilted, and the faults were reactivated in the 

major movement of the Laramide orogeny in 

Paleocene time. The Front Range high-angle reverse faults cut the sedime1ytary i·ocks at this time 

as a result of the reactivation of preexisting faults 

that were buried under the sedimentary rocks. 

The sandstone and andesite in the northwesttrending faults were brecciated and locally intermixed with the brecciated wallrocks. 

9. The wallrocks and fault gouge along the faults were 

weakly mineralized with pyritic ore in a calcite or 

quartz gangue. 

POST-LARAMIDE STRUCTURE 

Disastrophism in the central Rocky Mountains during the late Tertiary and Quaternary periods is postulated by many authors. Lovering and Goddard ( 1950, 

p. 63) described Mioeene deposits eut by faults. Lovering and Tweto ( 1953, p. 33) describe small postmineral 

(post-l\1ioeene n faults. Stark and others (1949, p. 

147-148) described tilted Plioeene beds in the Arkansas 

Valley near Salida. 

The last sentence on structural geology in reports on 

the geology of the Front Range repeatedly states that 

the mountains were raised intermittently by epeirogenic 

uplift to produce the late Te1tiary ~wd Quaternary 

pediments and stream terraces. To resort to uplift to 

explain Quaternary erosion and alluviation seems quite 

unnecessary. Quaternary geomorphic processes were 

not primarily the result of uplift but of climatic 

change. Mountain glaciation also must be considered 

the result of climatic change, and the cycles of mountain 

glaciation probably correspond exactly with the cycles 

of continental glaciation; furthermore the cycles of erosion and alluvia'tion on the unglaciated plains around 

the mountains also correspond with these glacial stages 

and are the result of cyclical fluctuations in climate. 

Evidence of Quaternary faulting in the Front Range 

is meager, and the Front Range is not now an active 

earthquake area. The lack of evidence for post-Pliocene faulting or uplift lends support to the belief that 

the Front Range has been stable for ·a long time, possibly since the ep.d of Pliocene time. The gentle slope 

of the sediments in the Ogallala formation in eastern I 

Colorado (about 35 feet per mile near Calhan to 20 

feet per mile near Kansas) indicates that the mountains 

could have been at almost their present altitude since 

Pliocene time. 

Quaternary fresh-water mollusks in the l(assler quadrangle (Scott, 1960) give another line of evidence in 

opposition to great uplift in the Pleistocene. If uplift 

had been progressive, then the environment would have 

become progressively colder, but the mollusk assemblage from a middle Pleistocene alluvium is like that 

found today in the arid to semiarid foothills m'ld lower 

mountains of New Mexico and Arizona; the 1nollusks 

from a late Pleistocene alluvium now live near timberline in the modern Rocky Mountains, but the mollusks 

in an early Recent alluvium were again warmth-loving 

and apparently needed a climate almost as warm as was 

.required by the middle Pleistocene mollusks. The climates, therefore, were not progressively warmer or 

colder but fluctuated because of climatic changes that 

were not related to progressive uplift. 
BEDROCK GE.OLOGY 113 

GEOLOGIC HISTORY 

The geologic history of the l(assler quadrangle, as 

interpreted not only from the geology of the quadrangle 

but also from that of surrounding areas, is complex. 

The major events were: the emplacement and metamorphism of the Precambrian rocks, the formation of 

late Precambrian faults which set the framework that. 

controlled the later structural history of the Front 

Range, the uplift of the ancestral Rockies, the deposition of the Pennsylvanian to Cretaceous rocks in .the 

Denver basin, the uplift <?f the Rocky Mountains, the 

deposition of the Tertiary rocks, and the deposition of 

the Quaternary deposits and formation of the modern 

topography. Most of these events have long been 

known, but to them can be added some details that have 

become known as a result of this investigation. 

The oldest rocks in the area were derived from sediments deposited in a basin in Precambrian time and 

were lithified by their own weight to shale, sandstone, 

n.nd limestone. The sediments were uplifted and 

crurhpled; heat and pressure in the zone of tJ.owage 

chn.nged the sedimentary rocks to more compact crystalline metamorphic rocks. These metamorphic rocks 

were then invaded by granitic fluids that converted 

son1e of the rocks to granite gneiss and migmatized 

others. Granite pegmatites invaded most of the metamorphic rocks in the last stage of this episode of granitization. The gneissic granite was intruded into the 

foliated rocks at th~ same time as the quartz monzonite 

(Boulder Creek granite) of the Georgetown area. The 

quartz diorite and hornblendite was intruded later. 

Later the biotite-muscovite granite was intruded into 

the n1etasedimentary rocks as widespread small bodies 

of granite with many associated pegmatites. 

The granite of the Pikes Peak batholith was intruded 

into , the o] der metamorphic and igneous rocks. 

Around the border of the batholith the country rock 

was slightly granitized. Pegmatitic fluids were intruded into fractures which opened in the granite and 

in the metamorphic rocks as the granite cooled. The 

pegmatites cooled slowly enough to form large crystals 

of quartz, feldspar, and other minerals. 

During the Ion()' period of erosion that separated the 

Precambrian frm~ the Paleozoic, a great thickness of 

rocks was removed and the land reduced nearly to a 

plain. 

In this area, erosion apparently coritinued for ~ome 

time from the Precambrian into the Paleozoic era. 

In Late Cambrian time the sea spread into the area and 

the Sawatch quartzite was deposited. The area apparently was structurally unstable, and earthquakes 

may have reopened large tension cracks along the Precambrian faults on the sea floor. Into these cracks the 

sand of the Sawatch quartzite may have poured and 

formed thick clastic dikes. 

The sea was spread over the area throughout most 

of Ordovician time, but apparently withdrew in Silurian, Devonian, and Early Mississippian time.1 In 

middle Mississippian time the sea again encroached on 

the area and deposited limestone. Uplift of the ancestral Rockies in Early Pennsylvanian time and subsequent erosion stripped off most of the earlier Paleozoic 

rocks. Coarse detritus that constitutes the Fountain 

formation was stripped from the mountains by streams 

and deposited on a slightly uneven but gently sloping 

floor as broad coalescing fans. After the land was 

lowered sufficiently, the sea again spread over the 

area and the Permian Lyons sandstone was deposited ' . as nearshore dunes, and the lower part of the Lyk1ns 

formation was deposited as marine shale and limestone. 

The sea again withdrew, and in later Permian and Triassic( n time the area apparently was a dry land on 

which silt and sand were deposited by wind and intermittent streams. 

The Early Jurassic sea may have covered the area, 

but no de.posits are preserved. Upper Jurassic limestone sandstone and siltstone of the Ralston Creek 

' ' . d fonnation and the Morrison formation were depos1te 

in fresh-water lakes and swamps or by streams that cut 

channels across marshy lagoonal flats and deposited 

sand in the channels. In Early Cretaceous time the 

sediments of the Lytle formation were deposited on a 

flood plain; then the sea spread over the area and ~eposited the sediments of the South Platte formatiOn 

along a beach and in the shallow water offshore. The 

Graneros, Greenhorn, a.nd Carlile formations were 

deposited in a deeper sea except for the Codell sandstone member which is calcarenite and may have been 

deposited on a beach. The sea deepened slightly, the 

water became. warmer, and the Fort Hays limestone 

and the Smoky Hill shale members of the Niobrara formation were deposited. The sea in which the lower 

part of the Pierre shale was deposited was a cooler sea 

and bituminous black shale was deposited. The sea 

then warmed and circulation improved, but, because the 

sea was withdrawing, only a little shale was deposited 

before the start of deposition of the Hygiene sandstone 

member. The sea again deepened and shale was deposited. Toward the end of ·the Cretaceous period, the 

sea began to withdraw for the last time as the Rocky 

Mountains started to rise, and sandy shale was deposited in the upper part of the Pierre. Sandstone 

with broken plant fragments and a predominance of · 

brackish-water fossils was deposited in the Fox Hills 

1 Murine rocks of Silurian age were 1iound in Albany County. Wyo., in 

1960 and described by Chronic and Ferri1:1 (19611) in n. symposium on 

lower and middle Paleozoic rocks of CoLorado. 
114 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

sandstone. The sea then withdrew completely from 

this area and the continued rise of the Rocky Mountains, slow at first and probably far to the west, caused 

the deposition of the fresh-water sandstone, coal, and 

claystone of the Laramie formation; the mountain 

rise then became more rapid along the axis of the 

Front Range and caused the deposition of the coarse 

conglomerate in the lower or Cretaceous part of the 

Dawson arkose; then the rise slowed again, and the 

siltstone of the Paleocene part of the Dawson arkose 

was deposited. The conformity of deposition of beds 

in the lowe.r two-thirds of the Dawson arkose indicates 

that uplift and tilting of the east flank of the Front 

Range did not happen until late Dawson time. 

In Cenozoic . time, at the climax of the Laramide 

structural disturbance, the Precambrian faults were reactivated, the Cambrian sandstone dikes were faulted, 

and andesite dikes were intruded into the Precambrian 

northwest- and northeast-trending faults, and possibiy 

into ne.wly created, flat-lying Laramide faults. In the 

latter part of the structural di~turbance, faults were 

again reactivated, the andesite dikes were faulted and 

brecciated, rhyolite was intruded into the Precambrian 

rocks, and welded tuff was interlayered with the upper 

part of the Dawson arkose. Probably the last event 

was the hydrothermal alteration of the faults and the 

postbrecciation emplacement of copper and uranium 

minerals along the northeast-trending flat-lying faults 

and fractures. 

ECONOMIC GEOLOGY 

Rocks in the quadrangle contain both nonmetallic 

and metallic deposits. The nonmetallic deposits include mica, feldspar, clay, coal, limestone, road metal, 

structural stone, and sand. Metallic deposits include 

iron, copper, and uranium. 

NONMETALLIC DEPOSITS 

Clay, limestone, road metal, and sand are now being 

mined ; coal and structural stone were forme.rly mined ; 

mica and feldspar were never mined in the quadrangle. 

MICA 

Muscovite was seen in sufficient quantity to warrant 

prospecting at five places in the quadrangle (pl. 2). 

1. Pegmatite on the ridge top in the SW%NE%SW% 

sec. 28, T. 7 S., R. 69 W., exposed in a 3-by-3-foot 

pegmatite. Mica in 4-inch books, warped, fractured, and stained by iron. 

2. Pegmatite on north side. of road in pit dug for quartz 

crystals in pegmatitic border zone of Pikes Peak 

granite in the NW1,4SE"% sec. 3, T. 8 S., R. 69 W. 

Mica in 4-inch weathered books lying on dump. 

3. Pegmatite 30 feet S. 40° W. from· General Land 

Office marker (half section corner~) on section line 

between sec. 33, T. 7 S., R. 69 W., and sec. 4, T. 

8 S., R. 69 W. Mica in 6-inch books, llard, flat 

and free-splitting, but slightly ruled, warped, and 

stained by iron. 

4. Pegmatite on logging road in SE1,4SW% sec. 22, 

' T. 7 S., R. 69 W. Mica in 4-inch books warped 

and slightly stained by iron. 

5. Pegmatite east of prospect pits in the SW1,4NE1,4 

sec. 25, T. 7 S., R. 69 W. Mica in 3-inch books. 

The mica described above may be suitable for scrap 

mica if the deposits are large enough to be mined. 

FELDSPAR 

Feldspar crystals of large size and possibly in minable 

quantity were found a;t three places in the quadrangle: 

1. Pegmatite in N'V%SW1,4 sec. 3, T. 8 S., R. 69 W., 

opened by prospect pit. Twelve-inch pieces of · 

microcline feldspar. 

2. Pegmatite in SW1,4SE1,4 sec. 10, T. 7 S., R. 69 W. 

Large pieces of potash feldspar, but deposits in 

this are~ probably are too small to mine. 

3. Pegmatite east of prospect pits in the SW1,4NE1,4 

sec. 25, T. 7 S., R. 69 W. Although the rock in 

this area seems to be about one-half pegmatite, the 

feldspar pods may be too small to mine. 

CLAY 

Brick clay and refractory clay are available in the 

Kassler quadrangle. Four mines were being worked 

in 1958 in the South Pl~tte form~tion for refractory 

clay and at least five other mines or prospects were 

formerly worked. The clay beds in the South Platte 

are lenticular and rarely exceed 9 feet in thickness. 

The four working mines are the Hogback, Hillside, 

Helmer Bros. underground, and Helmer Bros. open-pit. 

All four mines and other prospects in the South Platte 

formation were described by Van Sant ( 1959, p. 53.-61). 

Thin clay beds lie under and over the coal in the 

Laramie formation but they are said, by the former 

coal miners, to be too thin to be mined. Brick clay is 

available in the Graneros and the Pierre shales, the Fox 

Hills sandstone, and the lower part of the Laramie 

formation, but has not been used. 

COAL 

Several lenticular subbituminous coal beds lie near 

the· base of the Laramie formation. Five mines were 

operated in this area. G. C. Martin ( 1908) described 

two of these mines as follows: "Platte Canyon Fuel and 

Power Co. [probaoly mine No. 1], sec. 36, T. 6 S., R. 

69 W. Shaft 210 feet deep-then 20 feet horizontal west 

to coal, 6-foot bed, dips 20° * * * Old Lehigh mine 

(NWllt,SWV.t, sec. 20, T. 7 S., R. 68 W.) south of Platte 

Canyon mine, 8- to 12-foot bed [upper easternn1ost coal 
BHDROCK GEOLOGY 115 

bed]; 12-foot bed (sandstone); 4-foot bed [l~wer coal 

bed]." Platte Canyon Fuel and Power Co. mine No.2 

lies one-fourth mile south of mine No. 1. The shafts 

of both of the Platte Canyon mines are closed. Fragments of weathered coal and carbonized tree stumps lie 

on the dumps. A railroad was built to these two mines 

about 1900, but the mines and the railroad were abandoned before any coal was hauled. The entrance to the 

Lehigh mine is also caved and the access road is washed 

out. 

The inclined shaft of the Willow Creek mine in the 

NW%,NWI,4 sec. 1, T. 1 S., R. 68 W., is still open; 

however, the mine was shut down after a cave-in farther down in the mine. ·Two beds were worked in the 

Willow Creek mine, a 6-foot upper bed and a 4-foot 

lower bed. 

The shaft of Morgan's mine in the SW%SW% sec. 

6, T. 7 S., R. 68 W., is also open and some coal is still 

1nined for local consumption. Mr. Morgan did most of 

the exploration for coal in the quadrangle; three of his 

prospect pits lie along the strike of the bed on the Willow Creek Ranch in sec. 1, T. 1 S., R. 68 W. 

Other outcrops of the coal were observed, but none 

was as thick as the be.ds that were mined. The beds 

appear to be too thin and the coal of too low grade to 

permit mining under present ·economic conditions. 

LIMESTONE 

The Glennon limestone member of LeRoy of the 

Lykins formation and the Fort Hays limestone member of the Niobrara formation are the only limestones 

thick enough to be quarried. The Glennon limestone 

1nember was probably quarried for agricultural lime, 

for several kilns were observed along the outcrop. This 

limestone is not only thinner but less pure than the Fort 

I-Iays limestone. The thickness of the bed usually 

quarried ranges from 14 to 17 feet. No quarries were 

opern.ting in 1960 in the Glennon member. 

The Fort IIays limestone is quite pure and is used 

for foundry limestone. The thickness ranges between 

30 and 40 feet; however, the quarried thickness averages 

]ess than 30 feet in most places. The Helmer Bros. 

quarry ~n the SEl,.i sec. 2, T.7 S., R. 69 W., is operating 

part time. At least five abandoned quarries are located 

along the outcrop of the Fort Hays member. 

Other limestone beds lie below the Glennon limestone member of the Lykins formation, in the Ralston 

Creek formation, and near the middle and at the top 

of the Smoky Hill shale member of Niobrara formation. They have not been used because of their thinness 

or impurity. 

STRUCTURAL STONE 

One quarry in the NWl,.i sec. 30, T. 7 S., R. 68 W., 

was observed in the upper part of the South Platte 

formation where the degree of jointing made the rock 

favorable for dimension stone. About 1,000 cubic yards 

of sandstone have been removed for use as structural 

stone in the abandoned coal-mining town of Lehigh. 

The Pikes Peak granite has been quarried along the 

North Fork of the South Platte River west of the quadrangle and probably would be suitable elsewhere at one 

of the rare unweathered exposures. ' 

SAND 

Sand is quarried from the South Platte formation 

and Lyons sandstone for three purposes: as silica sand, 

molding sand, and core sand. The sandstone is suitable 

ior silica sand and has been used for glass-bottle manufacture, but the quantity available is too small to support a large glass factory (Vanderwilt, 1947, p. 262-

264). Six quarries (pl. 2) are operated in the South 

Platte formation; all the product is used for molding 

and core sand. The sand bed that is quarried from the 

South Platte lies near the top of the formation in the unnamed sandstone unit (Waage, 1955, p. 46). The mined 

bed is a 28-foot-thick massive soft friable white sandstone; thin iron-stained interlayers are removed before 

crushing. 

The bed in the Lyons sandstone which has been 

quarried at the localities shown on plate 2, is an 18.5-

foot-thick massive fine-grained soft friable white sandstone that lies about 80 feet below the top of the 

formation. Three small quarries were opened, but no 

sandstone was being taken from th~ Lyons sandstone in 

1950. 

ROAD METAL 

Road metal is defined as material that may be applied 

to a road to improve the performance characteristics 

of that road. 

Weathered Pikes Peak granite is used extensively for 

road metal on the mountainous part of State Route 67. 

No crushing or other treatment is necessary to prepare 

it for this use. A 15-foot blanket of suitable weathered 

granite overlies the unweathered granite in most of its 

outcrop area. A quarry is operated in the NE%,SWlf.1 ~ 

sec. 6, T. 8 S., R. 68 W. 

The Dawson arkose is used for road metal on several 

s1nall county roads. No quarries are open for this purpose, but where the road traverses the arkose, graders 

have spread it for road metal. 

METALLIC DEPOSITS 

Metallic ore minerals have not as yet been found in 

minable quantities in the quadrangle, but deposits of 

iron, copper, and uranium may well be present there 

in minable quantities-a waiting discovery. 
116 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

IRON 

Hematite occurs in small pods along the west side of 

the Bear Creek fault in sec. 33, T. 7 S., R. 69 1V., and in 

sec. 4, T. 8 S., R. 69 W. (pl. 2). The pods are northwest-trending bodies interlayered with the foliated 

rocks and apparently are related to mineralization along 

the Bear Creek fault. Lovering and Tweto (1953, p. 

31) described' a similar small body of high-grade hema-

. tite mined from the Hurricane Hill reef in the Clark 

tunnel in the Boulder tungsten district. Other small 

deposits of hematite were observed in the quartzite. in 

the southeast corner of the area, for instance, in the 

NE14 sec. 6, T. 8 S., R. 68 W. Pyrite is a common mineral in lime silicate gneiss, amphibolite, and in veins, 

but is too disseminated to be of economic interest. Magnetite is abundant in the granite gneiss and migmatite 

and in the granite pegmatite. It has been concentrated 

in sluices as a byproduct of gravel pits along the South 

Platte River. 

COPPER 

Copper minerals were seen in many prospects in the 

quadrangle, both in veins and disseminated near faults 

in the lime silicate gneiss and amphibolite. The most 

common minerals in these deposits are malachite and 

azurite. Other copper minerals seen at a few prospects 

are chalcopyrite, tenorite, chrysocolla, turquoise, and 

conichalcite. Smithsonite, a zinc mineral, was seen at 

one copper prospect. Three samples (see table below) 

from a copper prospect opened-by a 10-foot shaft along 

a northwest-trendi~g fault in the SW14SW14 sec. 22, 

T. 7 S., R. 69 W. (pl. 2), were tested for uranium, 

·nickel, cobalt, and copper by the U.S. Geological 

Survey. 

[Values for eU are for radioactivity, expressed in terms of equivalent uranium; 

analyst S. P. Furman. Values for Ni and Co were obtained by rapid methods 

used for geochemical prospecting, analyst H. E. Crowe. Values for Cu were obtained by the more precise electrolytic method, analyst D. L. Skinner] 

Laboratory 

analysis Rock eU 

---

D81776 Limonite gossan _______ 0. 001 

D81777 Biotite-quartz gneiss ___ . 002 

D81778 Lime silicate gneiss ____ . 001 

Ni Co 

----

0. 002 0. 017 . 01 . 09 . 004 . 03 

Cu 

2. 3 

5. 0 

2. 5 

6 

3 

4 

Although uranium, nickel, and cobalt are present only 

in traces, the copper content approaches that necessary 

for an ore deposit. In a copper mine in the NE14 

sec. 16, T. 7 S., R. 69 W., copper is slightly more abundant, and may constitute a minable deposit under more 

favorable economic conditions than at present. 

URANIUM 

The J(assler qua~rangle had been prospected for 

uranium and more than 100 claims had been located. 

Three claims had been explored by power equipment 

but uranium minerals were discovered in only one. On 

the Bonzo No. 1, in the South Platte canyon in the 

SE14SW14SW% sec. 33, T. 6 S., R. 69 W. (pl. 2), a 

pod of uraninite with secondary minerals gummite and 

autunite and with other unidentified minerals was exposed in the e~rly exploration. Further exploration in 

an incline and raise yielded more pocketlike deposits of 

uranium minerals . 

A fractured zone in the NW1Jt,NE14 sec. 21, T. 7 S., 

R. 69 W. (pl. 2) has been explored by a bulldozer opencut. Mr. Vance Haynes, a geologist and prospector, 

reported uraninite on this dump; oxidized uranium minerals were found later, but the radiation count in the 

pit was only slightly above background. 

Test trenches and shafts have been dug in the Fountain formation nor.th of J arre Creek in search of uranium deposits. The pits were said to contain oxidized 

uranium mineral~ and to be quite radioactive, but they 

have been abandoned. 

Radioactivity above background was measured along 

the Bear Creek fault in sec. 33, T. 7 S., R. 69 W., and 

in the saddle on the section line between sees. 26 and 

35, T. 7 S., R. 69 W. (pl. 2). 

Springs flow from one of the radioactive faults that 

contains a sandstone dike 1n Stevens Gulch 1n the 

middle of the Nlh sec. 21, T. 7 S., R. 69 W. The water 

from two of these springs was analyzed by chemists. of 

the U.S. Geological Survey. Sample 245703 is from a 

spring that flows directly from fractures in the sandstone dike. Sample 245704 is from a larger spring that 

flows up through valley alluvium after flowing from the 

fault. 

Analysis, in parts per million, of water from springs in Stevens 

Gulch, NH sec. 21, T. 7 S., R. 69 W. 

[Total solids analyzed by gravimetric method. Specific conductance and pH ana- lyzed electrically. Ca and Mg analyzed by versenate volumetric method. Li, 

Sr, Na, and K analyzed by flame photometer. U analyzed by fluorimetric method, 

Analyses by Wayne Mountjoy, except analyses of pH and uranium by H. H. Lipp.] 

Uranium-----------~-------------------- Lithium _______________________________ _ Strontium ______________________________ _ Calcium _______________________________ _ Sodium ________________________________ _ 

Potassium _____________________________ _ 

~agnesium~----------------------------

Total solids ____________________________ -

·Specific conductance __________ micromhos __ pli ____________________________________ _ 

245703 245704 

0. 001 

3 

17 

724 

488 

9 

2 

3, 980 

5, 370 

7. 0 

0. 001 

4 

12 

708 

500 

\) 

2 

4,_130 

5, 500 

7. 4 

The residues of the two samples were analyzed spectrographically for 64 elements. The results of this 

semiquantitative analysis are shown below: 
BE:DROCK GE:OLOGY 117 

Spectrogtaphic analysis of residues jrO'In spring water in Stevens 

Gulch, NH sec. 21, T. 7 S., R. 69 T'V. 

[Figures oro porcont of roslduo; M, mnjor constituent (>10 percent). Sl, Al, Cs, F, 

and H.b wero not looked for. rsual sensitivities do not apply owing to use of 

dilution 'teclmlque. Analyst, J. C. Hamilton, U.S. Geol. Survey) 

Sodiutn ~~~I~~~~·~~-_~:==========:=============== ________________________________ _ 

Titanium _______________ --- __ -_--------- 13oron _________________________________ _ 

l3arium __________________ - ___ - _---------

Strontiutn Copper--------------------------------- ______________________________ _ 

Vanadium _____________________________ _ 

245703 245704 

0. 07 

M 

M 

Tr. 

Tr. . 0007 

. 0007 

.7 

. 0015 

0. 07 

M 

M 

0 

Tr. . 0007 

. 0007 

.7 

. 0015 

R. D. George (George and others, 1920, p. 394) gave 

an analysis of water from Strontia. Springs, which flows 

from a fault about 1 mile southwest of and parallel with 

the fault along Stevens Gulch. Although the total 

solids make up a greater proportion of that water, t.he 

chemical composition of the spring water from the two 

locaJities is similar. 

Wa.ter and gas from the springs in Stevens Gulch 

were analyzed for radium and radon. The results are 

shown below : 

Radium and radon in spring water from Stevens Gulch, NH sec. 21, T. 7 S., R. 69 W. 

[Analyst, A. B. Tanner, U.S. Gcol. Survey] 

Spring in Sll.lldstonc Spring in valley dike alluvium 

Water Gas Water Gas 

phase phase phase phase 

H.a226 (micromicrocuries per liter± 20 percent) ________ 40 -------- 40 ------- Rn222 (tnicromicrocuries per liter± 10 percent) ________ 7,500 29,000 3,600 17,000 

Partition ratio: Rn in water+ Rn in gas _______________ 0. 26 0. 21 

Equilibrium partition· ratio __ . 32 . 29 

In explanation of these results Tanner stated (written 

communication, 1956) : 

The concentration of radium in the water samples was anomalous by ubout an order of magnitude and that of radon by 

about hnlf an order of magnitude. Natural waters containing 

more than 3 micromicrocuries per liter of radium or more than 

2,000 micromicrocuries per liter of radon are unusual. The 

nnomalies in radium and radon concentration suggest the 

presence of slight anomalies (0.005 to 0.010 percent eU) in 

uranium concentration in the vicinity of the sampling points. 

Along faults, the lime silicate gneiss and the amphibolite were the rocks most receptive to mineralizing solutions, probably because they contain vugs and because 

many of their constituents are ea,sily dissolved by acidcharged water. The a.mount of acid that acted on these 

rocks is demonstrated by etched figures on schorlomite 

and by crystals of diopside, apatite, garnet, scapolite, 

epidote, and quartz that have been pitted and rounded 

and given a waxy appearance by solution. 

Uranium and other ore minera1s in the amphibolite 

and lime silicate gneiss apparently were not entirely 

dependent on fractures for their localization. The minerals are disseminated through the rock as though some 

were original constituents. Some of the rocks are fractured, others are not. Many of the fractures are healed 

by hornblende . 

ENGINEERING PROBLEMS 

The engineering problems in the Kassler quadrangle 

are varied because there are so many geologic units. 

The problems involving the crystalline rocks are caused 

principally by fractures and faults and the freedom of 

water circulation in them. These fractures must be 

grouted beneath large concrete dams, both to provide a 

solid foundation and to prevent seepage. In building 

highways, drains should be installed to carry away the 

water seeping from the fractures and to prevent frost 

heaving and pumping under the pavement. The 

weathered mantle is sufficiently deep over most of the 

crystalline rocks that small one-way logging roads can 

be built without blasting, but larger roads would require considerable blasting, except in the Pikes Peak 

granite where the weathered rock is thicker. 

Clay is the principal cause of trouble in road construction in the Graneros shale, Greenhorn limestone, 

Carlile shale, Niobrara formation, Pierre shale, Fox 

Hills sandstone, Laramie formation, and the Dawson 

arkose. Some of the clay expm1ds when wet, and 

should either be removed and backfilled with permeable 

material or should be kept dry. Cuts in these shales 

should not exceed a slope of 45 °, arid in the Pierre shale 

cuts should be less than 20°. On the flanks of the pediments, landslides can be observed on 25 ° slopes several 

places in the Pierre shale. 

Most of the a.Iluvium in the area is well drained, but 

the soils in the older alluvium and the Piney Creek and 

post-Piney Creek alluvium are clayey, waterlogged, full 

of organic n1atter, and not suitable for fill; they should 

be stripped. and backfilled with free-draining granular 

1naterial. Both the clayey and organic-rich materials 

expand when wet and shrink when dry and thus 

make w1stable foundations. The loess also may cause 

similar problems because it contains much clay from 

the Pierre shale and the Dawson arkose. The bog clay, 

which is crossed by a north-trending road south of Roxborough Park school, sags and allows the road to become 

rutted and difficult to traverse after rains. The subbase of the road was built of bog clay, whereas the bog 

clay should have been stripped and backfilled with per-

·meable material. Because water is the primary cause 
118 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

of trouble in the clayey sediments, drains should be 

established wherever water can stand or where it seeps 

out at the contact of a permeable bed overlying the 

clayey shales-such as where alluvium overlies the 

Pierre shale. 

The geologic materials are listed below by excavation 

characteristics : 

Rock excavation (requires blasting) : 

All crystalline rocks. 

Sandstone dikes. 

Fountain formation. 

Lyons sandstone. 

Lykins formation; the limestone layers and possibly all 

shale below a depth of 25 feet. 

Morrison formation ; the thick limestone and sandstone 

layers and possibly all shale below a depth of 25 feet. 

Lytle and South Platte formations. 

Graneros shale, Greenhorn limestone, and Carlile shale; 

possibly all beds below a depth of 15 to 25 feet. 

Codell sandstone member of the Carlile shale and Fort Hays 

limestone member of Niobrara formation. 

Smoky Hill shale member of the Niobrara formation below 

a depth of 10 to 25 feet. 

Pierre shale ; possibly all shale below a depth of 50 to 100 

feet. 

Fox Hills sandstone ; the massive sandstone and possibly 

all shale below a depth of 50 feet. 

Laramie formation; the massive sandstone and possibly all 

shale below a depth of 25 feet. 

Dawson arkose; the conglomerate and sandstone and possibly all siltstone and claystone below a depth of 10 to 

25 feet. 

Common excavation (requires power equipment such as bulldozer with hooks, earth mover, and power shovel) : 

All surficial deposits. 

Parts of the bedrock units above the depths mentioned 

under "Rock excavation" above. 

FOSSIL LOCALITIES 

Localities of fossils in the bedrock formations in the Kassler quadrangle are listed below in stratigraphic order. Fossils were collected 

by the field workers in the years indicated. 

USGS 

Locality Mesozoic 

(pl. B) locality 

1 

2 

3 D1 

4 D2 

RALSTON CREEK FORMATION 

SE~SW~SE~ sec. 27, T. 6 S., R. 69 W. 

Scott, 1954. 

SOUTH PLATTE FORMATION 

SW~SW~NW~ sec. 35, T. 6 S., R. 69 W. 

E. B. Eckel, 1954. 

GREENHORN LIMESTONE 

Lincoln limestone member 

SW~SW~ sec. 19, T. 7 S., R. 68 W., from 

oyster limestone at base. Scott, W. A. 

Cobban, and Richard Van Horn, 1954. 

SW~SW~ sec. 19, T. 7 S., R. 68 W., from 

brown platy calcarenite at top. Scott, 

Cobban, and Van Horn, 1954. 

USGS 

Locality Mesozoic 

(pl. 2) locality 

GREENHORN LIMESTONE-Continued 

Bridge Creek limestone member 

5 D3 SE~NW~ sec. 30, T. 7 S., R. 68 W., from 

thin light-gray limestone bed. Scott, 1953. 

6 D1088 SE~SW~NW~ sec. 35, T. 6 S., R. 69 W., 

light-gray limestone at top. Scott, 1956. 

CARLILE SHALE 

Fairport chalky shale member 

7 D1089 SE~SW~NW~ sec. 35, T. 6 S., R. 69 W., 

from tan chalky platy shale at base. Scott, 

1956. 

Codell sandstone member 

8 D1086 NE~NW~SE~ sec. 2, T. 7 S., R. 69 W., 

from brown calcarenite. Scott, 1956. 

9 D1087 SW~SW~ sec. 12, T. 7 S., R. 69 W., from 

brown calcarenite. Scott, 1956. 

10 D1097 SE~SW~NW~ sec. 35, T. 6 S., R. 69 W., 

from brown calcarenite. Cobban, 1956. 

NIOBRARA FORMATION 

Fort Bays limestone member 

11 D1090 SE.USW.UNW~ sec. 35, T. 6 S., R. 69 W., 

from lower 15 ft. Scott, 1956. 

12 D1091 SE.USWUNWU sec. 35, T. 6 S., R. 69 W., 

from upper 15 ft. Scott, 1956. 

13 D1085 NEUNWUSEU sec. 2, T. 7 S., R. 69 W., from 

middle of limestone. Loaned to Scott by 

Mrs. Cecelia Head, 1956. 

14 D4 NEUNWU sec. 30, T. 7 S., R. 68 W., from 

15 D260 

16 D261 

17 D802 

18 D262 

19 D5 

20 D264 

21 D394 

22 D798 

near top of limestone. Scott, 1954. 

PIERRE SHALE 

SW.UNW~SW.USE~ sec. 19, T. 7 S., R. 68 

W., about 600 ft above base. Scott, 1954. 

SWUNWUSW.USE~ sec. 19, T. 7 S., R. 68 

W., about 630ft above base. Scott, 1954. 

NEUSWUSEUNEU sec. 30, T. 7 S., R. 68 

W., from limestone concretions. Scott, 1956. 

SWUNWUSW.USE~ sec. 19, T. 7 S., R. 68, 

W., from light-brown limonitic limestone 

layer. about 640ft above base. Scott, 1954. 

SWUSEU sec. 19, T. 7 S., R. 68 W., from 

tepee limestone. Scott, Cobban, and Van 

Horn, 1954. 

NW~NE~ sec. 30, T. 7 S., R. 68 W., about 

600ft above base. Cobban and Scott, 1954. 

NWUNW~ sec. 12, T. 7 S., R. 69 W., from 

.ironstone concretions in gray clayey shale. 

Scott and R. D. Miller, 1955. 

SE.USE.USWUSEU sec. 19, T. 7 S., R. 68 

W., from shale just below Hygiene sandstone 

member. J. H. Smith, 1956. 

22a Dl105 SEUSW.USEU sec. 19, T. 7 S., R. 68 W., 

from tan-gray limestone concretion in tan 

sandy shale, 26 feet above D798. Scott, 

1956. 

Hygiene sandstone member 

23 D791 NWUNWUSW~SEU sec. 19, T. 7 S., R. 68 

W., from small gray calcareous concretions. 

Scott, Cobban, and Van Horn, 1956. 

24 D1099 SWUSE.U sec. 19, T. 7 S., R. 68 W., from 

tan-gray sandy shale 15.5 feet above D791. 

Scott, 1956. 
BE·DROCK GEOLOGY 119 

USGS 

Localit11 Mesozoic 

(pl. t) locality 

PIERRE SHALE-Continued 

Hygiene sandstone member-Continued 

25 DllOO SW~SE~ sec. 19, T. 7 S., R. 68W., from sandy 

limestone conc.retions 18 feet above D1099. 

Scott, 1956. 

26 D9 SE~SE~ sec. 19, T. 7 S., R. 68 W., from shaly 

sandstone. Scott, Cobban, M. E. Cooley, 

and Van Horn, 1954. 

27 D790 NW~SE~N:W~NW~NW~ sec. 19, T. 7 

S., R. 68 W., from phosphatic nodule zone. 

Scott, Van Horn, and Cobban, 1956. 

28 D809 NW~NE~N·W~NW~ sec. 32, T. 7 S., R. 

68 W., from sandy calcareous concretions. 

Scott and Cobban, 1956. · 

29 D828 NW~SW~ sec. 1, T. 7 S., R. 69 W., from gray 

limestone nodules. Same level as D391 and 

D6. Scott, 1956. 

30 D391 SE~NW~NW~NW~ sec. 19, T. 7 S., R. , 

68 W., from gray limestone concretions in 

sandy shale. Scott, Van Horn, Miller, and 

Cobban, 1955. 

31 DllOl SW~SE~ sec. 19, T. 7 S., R. 68 W., fr()m gray 

earthy limestone concretions 28.5 feet above 

DllOO. Scott, 1956. 

32 D779 Near center N~N~ sec. 35, T. 6 S., R. 69 W., 

from iron-stained limestone bed in Highline 

canal 190 ft below D6. Scott and W. L. 

Peterson, 1956. 

33 D1102 SW~SE~ sec. 19, T. 7 S., R. 68 W., 21 ft 

above DllOl. Scott, 1956. 

34 22840 NE~NW~SW~SE~ sec. 19, T. 7 S., R. 68 

W., from limy nodules 86 ft above loc. 33 

Scott, Cobban, Cooley, and Van Horn, 1950. 

35 D799 NE~SE~SW~SE~ sec. 19, T. 7 S., R. 68 W., 

from sandstone ledge near middle of Hygiene 

sandstone member. Scott and Cobban, 1956. 

. 36 D810 NW~NE~NW,UNW,U sec. 32, T. 7 S., R. 

68 W., from sandy calcareous concretions. 

Scott and Cobban, 1956. 

37 D392 SW,UNE,UNW,UNW~ .sec. 19, T. 7 S., R. 

68 W., from small gray and brown limestone 

concretions. Scott, Miller, Cobban, and 

Van Horn, 1955. 

38 D826 NE,USW~SW,U sec. 1, T. 7 S., R. 69 W., 

from gray sandy calcareous nodules. Scott, 

1956. 

39 '? SW,UNE~SE,U sec. 35, T. 6 S., R. 69 W., 

from gray sandy calcareous nodules 25 ft. 

below D1012. Scott, 1956. 

40 D393 SE,UNE,UNW~NW~ sec. 19, T. 7 S., R. 

68 W., from sandy limestone concretions. 

Scott and Miller, 1955. · 

41 22838 NW~NW,U sec. 32, T. 7 S., R. 68 W., from 

limy sandy nodules in sandy shale. Scott 

and Cobban, 1950. 

42 D6 SW~NE~ sec. 35, T. 6 S., R. 69 W., from 

gray limy concretions. Scott, 1954. 

43 D1012 SW~NE~SE~ sec. 35, T. 6 S., R. 69 W., 

from gray sandy tepee limestone and limy 

nodul.es. Scott, 1956. 

USGS 

Locality Mesozoic 

(pl. e) localitll 

PIERRE SHALE-Continued 

Hygiene sandstone member-Continued 

44 D792 SE,USW~NW,USE,U sec. 19, T. 7 S., R. 68 

W., from hard sandy bed 44ft. above 22840 

and 25. ft below top of Hygiene sandstone 

member. Scott, Cobban, .and Van Horn, 

1956. 

45 Dll03 NW~SE~ sec. 19, T. 7 S., R. 68 W., from ironstone concretions in gray sandy shale 47ft. 

above D792. Scott, 1956. 

46 D800 SW~NW,USE,USE,U sec. 19, T. 7 S., R. 68 

W., from brown ironstone concretions. Scott, 

1956. 

47 D793 SW,USW,USE,UNWUSEU sec. 19, T. 7 S., 

R. 68 W., from top of Hygiene sandstone 

member a little higher than D792. Scott 

and Van Horn, 1956. 

Shale above Hygiene sandstone member 

48 D824 SW~NEUSW,U sec. 1, T. 7 S., R. 69 W., 

from tepee butte limestone in sandy shale. 

Scott, 1956. 

49 D827 NEUNE,U sec. 2, T. 7 S., R. 69 W., from 

brown silty calcareous nodules in sandy shale. 

Scott, 1956. 

50 D285 SW,UNW,UNW~ sec. 1, T. 7 S., R. 69 W., 

from gray tepee limestone and brown limestone concretions. Scott, 1955. 

51 Dll04 NWUSEU sec. 19,- T. 7 S., R. 68 W., from tangray chalky shale 31 ft above Dll03 and 

about 10 ft. above D793. Scott, 1956. 

52 D263 NW,USE,U sec. 19, T. 7 S., R .. 68 W., from concretion 33ft above Dll04. Scott, 1954. 

53 D794 NW,USE,UNW,USEU sec. 19, T. 7 S., R. 68 

W., from sandy shale above D263. Cobban 

and Scott, 1956. 

54 D795 NE,USE,UNW,USE,U sec. 19, T. 7 S., R. 68 

W., from gray tepee limestone and rusty 

ironstone concretions. Scott and Cobban, 

1956. 

55 DB NE,UNW,U sec. 19, T. 7 S., R . .68 W., from 

olive-gray limestone concretion in clayey 

shale. Scott and Miller, 1954. 

56 D7. NE,USW,UNW,U sec. 1, T. 7 S., R. 69 W., 

from olive-gray limestone concretions in 

clayey shale. Scott, 1954. 

57 D808 SW~SWUSE,USW,U sec. 29, T. 7 S., R. 68 W., 

from iron-stained concretions. Scott and 

Cobban, 1956. 

58 D811 NEUSE,USW,USW~ sec. 29, T. 7 S., R. 68 

W., from brown-weathering dark-gray limestone concretions in gray clayey shale. 

Scott, 1956. 

59 D807 NW~NW,UNEUNW,U sec. 32, T. 7 S., R. 68 

W., from brownish-gray tepee butte limestone. Cobban and Scott, 1956. 

60 D803 SWUNE,USE,UNE,U sec. 30, T. 7 S., R. 68 

W., from brownish-gray tepee butte limestone. Scott, Cobban, and Smith, 1956. 

61 D825 Center NW~ sec. 1, T. 7 S., R. 69 W., from 

gray limestone concretions in clayey shale. 

Scott, 1956. 
120 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

USGS 

Locality Mesozoic 

(pl. f) locality 

PIERRE SHALE-Continued 

Shale above Hygiene sandstone member-Continued 

62 D804 SW~NE~SE~NE~ sec. 30, T. 7 S., R. 68 

W., from brown and gray. limestone nodules 

15 to 30 ft above D803. Scott, Cobban, and 

Smith, 1956. 

63 D801 SE~NW~SE~SE~ sec. 19, T. 7 S., R. 68 W., 

from iron-stained limestone concretions in 

clayey shale. Cobban, 1956. 

64 D796 SW~NW~NE~SE~ sec. 19, T. 7 S., R. 68 

W., from gray calcareous concretions above 

D795. Cobban, 1956. 

65 D789 NE~SW~SW~ sec. 18, T. 7 S., R. 68 W., 

from gray calcareous concretions and ironstones. Scott, 1956. 

66 D788 NW~SE~SW~ sec. 18, T. 7 S., R. 68 W., 

from brown- and gray-weathering limestone 

concretions. Scott, Cobban, and Van Horn, 

1956. 

67 D806 SW~NE~NE~NW~ sec. 32, T. 7 S., R. 68 

W., from brown- and gray-weathering limestone concretions. Scott and Cobban, 1956. 

68 D805 NW~SW~SW~NE~ sec. 32, T. 7 S., R. 68 

W., from sandy concretions in sandy shale. 

Scott and Cobban, 1956. 

69 D812 SE~NW~SE~SW~ sec. 29, T. 7 S., R. 68 

W., from brown ironstone concretions in 

clayey shale. Cobban, 1956. 

70 D813 NE~NW%SE~SW~ sec. 29, T. 7 S., R. 68 

W., from ironstone concretions in clayey 

shale. Scott, 1956. 

71 D834 NE~NE~ sec. 30, T. 7 S., R. 68 W., from 

gray clayey shale. Scott, 1956 (collection 

missing). 

72 D786 NW~SE~NW~ sec. 18, T. 7 S., R. 68 W., 

from ironstone concretions and cone-in-cone 

layers in dark clayey shale. Scott, Van 

Horn, and Cobban, 1956. 

73 D787 SW~NE~NW~ sec. 18, T. S., R. 68 W., 

from dark clayey shale a little above D786, 

Van Horn, 1956. 

74 22837 SE~SE~ sec. 19, T. 7 S., R. 68 W. from sandy 

shale. Scott, 1950. 

75 D585 NW~SW~NW~ sec. 7, T. 7 S., R. 68 W., 

from gray limestone concretions in gray 

sandy shale. Scott, 1955. 

76 DlO NE~SW~ sec. 18, T. 7 S., R. 68 W., from 

hard 8-inch sandstone layer in sandy shale. 

Scott, Cobban, Cooley, Van Horn, 1954. 

77 22839 SE~NE~SE~ sec. 19, T. 7 S., R. 68 W., 

from sandy shale. Scott, 1950. 

78 Dll NE~SW~ sec. 18, T. 7 S., R. 68 W., from 

hard calcareous concretion about 50 ft 

above D10. Scott, Cobban, Cooley, and 

Van Horn, 1954. 

79 D12 NE~SW~ sec. 18, T. 7 S., R. 68 W., from hard 

sandstone layer about 55 ft above D11. 

Scott, Cobban, Cooley, and Van Horn, 1954. 

80 22836 SE~NE~SE~ sec. 19, T. 7 S., R. 68 W., 

from sandy shale. Scott, 1950. 

. USGS 

Locality Mesozoic 

(pl. t) locality 

PIERRE SHALE-Continued 

Shale above Hygiene sandstone member-Continued 

81 22841 

82 D814 

83 D13 

84 D815 

85 

86 

87 

NW~SE~ sec. 32, T; ·7 S., R. 68 W;-, from 

friable sandstone· in cut. Scott, Cobban, 

and Van Horn, 1950. 

SE~SW~NE~SW~ sec. 29, T. 7 S., R. 68 

W., from sandy limestone concretions in 

shaly sandstone. Cobban and Scott, 1956. 

NE~SW~ sec. 18, T. 7 S., R. 68 W., from top 

of exposures or' upper sandy shale about 100 

ft above D12. Scott, Cobban, Cooley, and 

Van Horn, 1954. 

NW~SE~NE~SW~ sec. 29, T. 7 S., R. 68 

W.; fossils replaced by olive-green sandy 

phosphatic nodules. Cobban and Scott, 

1956. 

LARAMIE FORMATION 

SE~NW~ sec. 29, T. 7 S., R. 68 W., from 

sandy ironstone bed about 125 ft below top of 

Laramie formation. Scott, 1950. 

DAWSON ARKOSE 

NW~SE~ sec. 29, T. 7 S., R. 68 W., from 

sandy ironstone bed in lower part of Dawson 

arkose. Scott, ·1950. 

SW~NE~ SW% sec. 8, T. 7 S., R. 68 W.; fossil 

leaves from clayey ironstone beds in upper 

part of Dawl:!on arkose. Scott, 1950. Ficus 

sp.; age not determinable. 

REFERENCES CITED 

Ball, S. H., 1906, Precambrian rocks of the Georgetown quadrangle, Colorado: Am. Jour. Sci., 4th ser., v. 21, p. 371-389. 

Bass, N. W., 1926, Geology of Hamilton County, pt. 2 of Geologic 

investigations in western Kansas: Kansas State Geol. Survey Bull. 11, 95 p. 

Brown, R. W., 1943, Cretaceous-Tertiary boundary in the Denver 

Basin, Colorado :. Geol. Soc. America Bull., v. 54, no. 1, 

p. 65-86. 

Chronic, John, and Ferris, C. S., Jr., 1961, Early Paleozoic outlier in southeastern Wyoming, in Lower and middle Paleozoic rocks of Colorado: Rocky Mtn . .&ssoc. Geologists 12th 

Field Conf., South central Colorado, 1960, p. 143-146. 

Cobban, W. A., and Reeside, J. B., Jr., 1952, Correlation of the 

Cretaceous formations of the western interior of the United 

States: Geol. Soc. America Bull., v. 63, no. 10, p. 1011-1043. 

Cragin, F. W., 1896, On the stratigraphy of the Platte series, or 

Upper Cretaceous of the Plains: Colorado Coll. Studies, v. 

6, p. 49-52. 

Crosby, W. 0., 1895, Sandstone dikes accompanying the great 

fault of Ute Pass, Colorado: Essex lnst. Bull., v. 27, p. 118-

147. 

Cross, 0. W., 1894a, Description of the Pikes Peak sheet [Colorado] :U.S. -Geol. Survey Atlas, Folio 7, 5 p. 

---1894b, Intrusive sandstone dikes in granite: Geol. Soc. 

America Bull., v. 5, p. 225-230. 
BEDROCK GEOLOGY 121 

Dnne, C. H., nnd Pierce, W. G., 1933, Geology and oil and gas 

prospects iu pnrt of enstern Colorado: U.S. Dept. Interior 

Memo. 72215, June 8, 1933, 8 p. 

Dane, C. H., Pierce, 'V. G., and Reeside, J. B., Jr., 1937, The 

strntigrnphy of the Upper Cretnceous rocks north of the 

Arlmnsas River in eastern Colorado: U.S. Geol. Survey 

Prof. Pnper 186-K, p. 207-232. 

Eldridge, G. H., 1889, On some stratigrnphical and structural 

features of the country about Denver, Colorado: Colorado 

Sci. Soc. Proc., v. 3, pt. 1, p. 86-118. 

Elias, M. K., 1931, The geology of Wallace County, Kansas: 

Kansas State Geol. Survey Bull, 18, 254 p. 

l~mmons, S. l!"'., Cross, C. ,V., and Eldridge, G. H., 1896, Geology 

of the Denver Bnsin in Colorado: U.S. Geol. Survey Mon. 

27, 556 p. 

l!"'enneman, N. M., 1905, Geology of the Boulder district, Colorado: U.S. Geol. Survey Bull. 265, 101 p. 

---1931, Physiography of western United States: New 

Yorli:, McGraw-Hill, 534 p. 

Fiulny, G. I., 1916, Description of the Colorado Springs quadrangle [Colorado] : U.S. Geol. Survey Atlas, Folio 203, 15 p. 

George, R. D., Curtis, H. A., Lester, 0. C., Crook, J. K., Yeo, 

J. B., and others, 1920, Mineral waters of Colorado: Colorado Geol. Survey Bull. 11, 474 p. 

Gilbert, G. K., 1896, The underground water of the Arkansas 

Valley in eastern Colorado: U.S. Geol. Survey Ann. Rept. 

17, pt. 2, p. 551-601. 

Gilluly, Jnmes, and Reeside, J. B., Jr., 1928, Sedimentary rocks 

of the San Rafael Swell and some adjacent areas in eastern 

Utah: U.S. Geol. Sun-ey Prof. Pap~r 150, p. 61-110. 

Goddard, ID. N., and others, 1948, Rock-color chart: Natl. Research Council, 6 p. 

Gregory, H. E., 1938, The San Juan Country: U.S. Geol. Survey 

Prof. Paper 188, 123 p. 

Hat'l'ison, J. E., and 'Yells, J. D., 1956, Geology and ore deposits 

of the l!"'reeland-I.amnrtine district, Clear Creel{ County, 

Colorado: U.S. Geol. Survey Bull. 1032-B, p. 33-127. 

--- 19G!), Geology and ore deposits of the Chicago Creek area, 

Clear Creek County, Colorado: U.S. Geol. Survey Prof. 

Paper 319, 92 p. 

Hayden, F. V., 1873, The geological features of the east slope 

of the Colorado Range of the Rocky Mountains from Cache 

la Poudre River southward to Pikes Peak: U.S. Geol. and 

Geog. Survey Terr., embracing Colorado, 7th Ann. Rept., · 

chap. 1, p. 31 [1874]. 

Hutchinson, R. M., 1959, A40/K40 age determinations of rocks associated with north end of Pil<es :Peak batholith, Jefferson, 

Douglas, and Park Counties, Colorado [nbs.] : Geol. Soc. 

America Bull., v. 70, no. 12, pt. 2, p. 1622. 

.Johnson, .J. H., 1930, Unconformity in the Colorado group in 

enst:ern Colorado: Am. Assoc. Petroleum Geologists Bull., 

v. 14, p, 789-794. 

King, Clnrence, 1876, Annual revort upon the geological exploration of the fortieth parallel from the Sierra Nevada to the 

eastern slope of the Hocky l\Iountains: U.S. Geol. Explor. 

40th Pnrnllel.Atlas, mnps 1 nnd2. 

LeRoy, IJ. " 7., 1946, Stratigraphy of the Golden-Morrison area, 

Jefferson County, Colorado: Colorado School Mines Quart., 

v. 41, no. 2, i15 p. 

Lognu, "r· N., 1897, The upper Cretnceous of Kansas: Kansas 

Univ. Geol. Survey, v. 2, p. 195-234. 

Lovering, T. S., 1935, Geology and ore deposits of the Montezuma quadrangle, Colorado: U.S. Geol. Survey Prof. Paper 

178,119 p. 

Lovering, '1'. S., and Goddard, E. N., 1950, Geology and ore deposits of the Front Range, Colorado: U.S. Geol. Survey 

Prof. Paper 223, 319 p. 

Lovering, T. S., and Tweto, 0. L., 1953, Geology and ore deposits 

of the Boulder County tungsten district, Colorado: U.S. 

Geol. Survey Prof. Paper 245, 199 p. 

Lupton, C. T., 1914, Oil and gas near Green River, Grand County, 

Utah: U.S. Geol. Survey Bull. 541, p. 115-133. 

McKee, E. D., Oriel, 1S. S., Swanson, V. E., MacLachlan, M. E., 

MacLachlan, J. C., Ketner, K. B., Goldsmith, J. W., Bell, 

R. Y., and Jameson, D. J., 1956, Paleotectonic maps of the 

Jurassic system: U.S. Geol. Survey Misc. Geol. Inv. Map 

I-175, 6 p. 

Maher, J. C., 1953, Permian and Pennsylvanian rocks of southeastern Colorado: Am. Assoc. Petroleum Geologists Bull., v. 

37, p. 913-939. 

Martin, G. C., 1908, U.S. Geol. Survey Mine Notes 9-911, notebook 1: U.S. Geol. Survey Archives No. 2541. 

Maughan, E. K., and ·wnson, R. F., 1960, Pennsylvanian and 

Permian strata in southern 'Vyoming and northern Colorado, in Guide to the geology of Colorado : Geol. Soc. 

America, p. 34-42. 

Meek, F. B., and Hayden, F. V., 1862, Descriptions of new Lower 

'Silurian (Primordial), Jurassic, Cretaceous, and Tertiary 

fossils, collected in Nebraska Territory, with some remarks 

on the rocks from which they were obtained: Acad. Nat. 

Sci. Philadelphia Proc., v. 13, p. 415-447 [1861]. 

Munsell Color Co., Inc., 1954, Soil color charts. 

Peterson, ,V. L., and Scott, G. R., 1960, Precambrian rocks and 

structure of the Platte Canyon and Kassler quadrangles, 

Colorado, in Guide to the geology of Colorado : Geol. Soc. 

America, p. 181-183. 

Richardson, G. B., 1912, The Monument Creek group: Geol. 

Soc. America Bull., v. 23, p. 267-276. 

Roy, C. J., 1946, Clastic dikes of the Pikes Peak region [Colorado] [abs.] : Geol. Soc. America Bull., v. 57, no. 12, p. 1226. 

Rubey, ,V, ,V., and Bass, N. ,V., 1925, The geology of Russell 

County, Kansas, with special reference to oil and gas resources: Kansas State Geol. Survey Bull. 10, p. 1-86. 

Schrader, F. C., Stone, R. ,V,, and Sanford, Samuel, 1917, Useful 

minerals of the United States: U.S. Geol. Survey Bull. 624, 

412p. 

Scott, G. R., 1960, Quaternary sequence east of the Front Range 

near Denver, Colorado, in Guide to the geology of Colorado: 

Geol. Soc. America, p. 206-211. 

---1963, Quaternary geology and geomorphic history of the 

Kassler quadrangle, Colorado: U.S. Geol. Survey Prof. 

Paper 421-.A, 70 p. 

Spurr, J. E., Garrey, G. H., and Ball, S. H., 1908, Economic 

geology of the Georgetown quadrangle, Colorado: U.S. 

Geol. Survey Prof. Paper 63, 422 p. 

Stark, J. T., and others, 1949, Geology and origin of South 

Park, Colorado : Geol. Soc. America Mem. 33, 188 p. 

Sternberg, C. ,V., and Crowley, A. J., 1954, Cretaceous sands of 

the· Denver basin, in Jensen, F. S., Sharl{ey, H. H. R., and 

Turner, D. S., eds, The oil and gas fields of Colorado-a 

symposium : Rocky Mountain Assoc. Geologists, 302 p. 
122 GEOLOGY OF THE KASSLER QUADRANGLE, COLORADO 

Turner, F. J., and Verhoogen, Jean, 1951, Igneous and metamorphic petrology: New York, McGraw-Hill Book Co., 602 

p. 

Vanderwilt, J. W., 1947, Mineral resources of Colorado: Colorado Mineral Resources Board, 54 7 p. 

Van Horn, Richard, 1957, Ralston Creek formation, a new name 

for the Ralston formation of LeRoy (1946) [Colorado] : 

Am. Assoc. Petroleum Geologists Bull., v. 41, no. 4, p. 755-

756. 

VanSant, J. N., 1959, Refractory-clay deposits of. Colorado: U.S. 

Bur. Mines Inv. Rept. 5553, 156 p. 

Vitanage, P. W., 1954, Sandstone dikes in the South Platte area, 

Colorado: Jour. Geology, v. 62, no. 5, p. 493-500. 

Waage, K. M., 1955, Dakota group in northern Front Range foothills, Colorado: U.S. Geol. Survey Prof. Paper 274-B, 51 p. 

Williams, Bowel, Turner, F. J., and Gilbert, C. M., 1954, Petrography-an introduction to the study of rocks in thin sections: San Francisco, W. H. Freeman & Co., 406 p. 

Williston, S. W., 1893, The Niobrara Cretaceous of western Kansas: Kansas Acad. Sci. Trans., v. 13, p. 107-111. 
A 

Page 

Abstract •••••••••• -------.----------- ___ -----. 71 

Acanthoceraa SP------------------------------- 95,96 

Access •••••••••••••••• ----.------------------- 71 

Acknowledgments ___ ------------------------- 73 

Actinolite, in lime sllicate gneiss______________ 78 

Algae, 1n Morrison formation_________________ 93 

in Ralston Crook formation_______________ 92 

Allanite, 1n limo sUlcate gneiss________________ 78 

Amattropaia paludinaeformia. --------------- 100,102 

Ammonite zones, Pierre shale _______________ 99-103 

Amphibolite, Precambrian ___________________ 7&-77 

Analyses, sandstone dikes and Sawatch 

quartzite._------------------- ___ • 87 

springs, Stevens Gulch _________________ 116,117 

uranium in copper prospect_______________ 116 

Anapachgdiacua complezua •••••••••••••• 101,102,103 

Anchura SP--------------------------------- 100,102 

Andesite dikes •••••••••••••••••••••••••••••• 106-107 

Anona robuata. ------------------------------- 106 

Apatite, in lime slUcate gneiss._-------------- 78 

Aporrhaia meekL •••• ----------------------- 100,102 Aatarte gregaria •••• __________________________ 100,102 

Autunite •• ----------------------- __ -------___ 116 Azurite .• ________________ • __ •••• __ ._ •• ________ 116 

B 

Baculitea aaperiformi&.--------------- 99,100,102, 103 

baculua. __ -------------------------------- 103 clinolobatua •• ___________________ ·100, 102,103, 104 

corru,gattta _.-----------------·--------- ___ 103 

crickmayi. -------------· ---------------- 100, 102 

eliaaL.----------------------------- 100,102,103 grandia _____________________________ 100,102,103 

oreoorvenaiB---------------------- 99, 100,102, 103 

obtnBttB----------------------·------- 99,100,102 

TUOOBU8 •••••• --------·-•••• --------••••• 100, 102 

8COtti_. ••••••••••••••••••••••••••• 99, 100,102,103 

n. sp. (weakly ribbed venter). ___ 99,100,102, 103 

sp. -------•••• ---------- ___ • _____ ------ _ 100, 102 

Barnett, Paul R., analyst.___________________ 87 

Borgen shale member, Lykins formation ______ 90,91 

Beryl, In pegmatltos.------------------------- 8.5 

Biotite, In limo slllcate gneiss_________________ 78 

Biotite-muscovite granite, Precambrian ______ 82-83 

Blot.ltc-quartz gneiss, Precambrian___________ 75 

Dluo Hill shale member, Carlile shale _________ 95,96 

Bonzo No. 1 claim____________________________ 116 

Bridge Creek limestone member, Greenhorn 

formation _________________________ 95,96 

Brown, R. W., fossllldontification............ 106 

c 

Calcite, ln limo silicate gneiss_________________ 78 

Calgcocera8. __________ ---- _ ------ _____ -------- 96 

canitaurinum. _____ ------ ___ _ __ _ _ _ __ ____ __ 95 

Carillo shale _______________________________ 95, 96,97 

Cenozoic sedimentary rocks. See Mesozoic 

and Cenozoic sedimentary rocks. 

Chalcopyrite. ___ --------------------------___ 116 

Charophytos, in Ralston formation___________ 91 

Chrysoboryl, in pogmatitos.-------------~---- 85 

Chrysocolla. ___ ------------------------------ 116 

INDEX 

Page 

Clay, refractory, South Platte formation______ 94 

Clay deposits ________ ------------------------- 114 

Clio8caphites choteauemia______________________ 98 

Coal deposits •• ----------------------------- 114-115 

Codell sandstone member, Carllle"shale _______ 95,96 

Collignoniceras SP----------------------------- 95,96 

Commercial activities .• _--------------------- 73 

Conlchalclte ________________ -------------- ____ 116 

Conklin, Nancy M., analyst__________________ 87 

Copper deposits______________________________ 116 

Corals, 1n Pierre shale ______________________ 100,101 

Crenella elegantula __________________________ 100,101 

Crowe, H. E., analyst. ____________________ _.__ 116 

Crystallization, biotite-muscovite granite_____ 83 

order, minerals of lime silicate gneiss •• ____ 78 

D 

Dakoticancer SP----------------------------- 101,102 Dawson arkose, description _________________ 105, 106 

folds ________ • ________________________ .____ 111 

Jarre Creek fault.------------------------ 109 Dentalium gracile ___________________________ 100,102 

Didymoceraa nebrascense •• -------------- 100, 102, 103 n. sp. (loosely coiled) ___________________ 100,102 

n. sp. (tightly coiled).----------------- 100,102 

sp ___________________ ------------------- 100, 102 

Dike rocks, Intrusive _______________________ 106-107 

Dikes. See Andesite dikes and sandstone 

dikes. 

Dinosaur bones, Morrison formation__________ 93 

Dlopslde, In lime sUlcate gneiss_______________ 78 

Discoscaphite8 n. SP------------------------- 101,102 

SP---------------------------------- 101,102,105 

DombevopBiB ainuata.------------------------- 106 

Doublehead pluton___________________________ 83 

Drainage. ____________ -- ____ -- __ ._____________ 73 

. Drepanochilu8 nebra8cenai8------------------ 100,102 

sp ____ ------- _ ------ ---~----- __ ------- __ 100, 102 

E 

Echinochara 8pino&a •.. ------------------------ 92 

Echinoid, mold, South Platte formation______ 94 

Engineering problems---------------------- 117-118 

Epidote, In lime slllcate gneiss________________ 78 

Excavation characteristics of bedrock_________ 118 Exitelocera~jenneyi. ____________________ 100,102,103 

F 

Fairport chalky shale member, Carlile shale .• 95,96 

Falcon limestone member, Lykins formation. 90 

Faults, history __ --------------------------·--- 112 

Laramide _______ • __ ---- _____ .-------- ___ 109-110 

Precambrian._--------------------------- 108 

Quaternary-------------------------______ 112 

role in emplacement of sandstone dikes •.• 87-88 

thinning of Fountain formation___________ 89 

Faunal zonation, Pierre shale ____________ 99, 10o-103 

Feldspar deposits----------------------------- 114 

Ficus arenacea .• ----------------·------------- 106 

planico8tata _____ __ -------------- _________ • 106 

. trinervis ••••••• ------------------- __ ------- 106 

Page 

Fish, bones, Niobrara formation.----------_. 98 

bones, Pierre shale. ______________ -. 101, 102, 104 

scales, Carlile shale.-------------------__ 95 

Graneros shale·---------------------- 94 

Niobrara formation ________________ ._ 98 

teeth, Pierre shale. ________________ 101,102,104 

vertebra, Pierre shale __________________ 101,102 

Flow structure, biotite-muscovite granite..... 82 

Folds, Laramide ____________________________ UG-111 

Precambrian._------------------ ____ ----- 108 

ptygmatic, granite gneiss and migmatlte. 80 

Foliation, amphibolite._______________________ 76 

biotite-muscovite granite_________________ 82 

granite gneiss and migmatlte. _ ----------- 78,80 

homblendite •• ------------------- __ ------ 81-82 

Pikes Peak granite, border zones_________ 83 

quartz diorite ••••• ------------------------ 81 

sllllmanitic biotite-quartz gneiss •••••••••• 74,75 

Fort Hays limestone member, Niobrara formation._------------------------- 97-98 

Fossils, 1n Carlile shale_______________________ 95 

In Dawson arkose------------------------ 106 

Fountain formation ____________________ -. 89 

Greenhorn limestone ••• ------------~----- 95 Laramie formation _____________________ -. 106 

locallties ____________ ~------------- ll8-120, pl. 2 

Morrison formation ____________________ -. 93 

Niobrara formation·------·-----------.--- 97,98 

Pierre shale-----------------------.- 99, 100-104 

Ralston Creek formation_________________ 92 

stratigraphic distribution by ammonite zones in Pierre shale ____________ 100-103 

Fountain formation, description ______________ 88-89 

folds ••••• __________________________ •• __ ._. 111 

Jarre Creek fault. ••..•. ------------------ 109 

Fox Hills sandstone------------------------ 104,105 

Fractures, healed, granite gneiss and migmatite ______ . ____________ ---------- 80 

Front Range, cross section showing structure. 111 

Furman, S. P., analyst_______________________ 116 

G 

Gahnlte, in lime silicate gneiss________________ 78 

Garnet, in lime silicate gneiss_________________ 78 

Gastropod, undetermined------------------ 100, 102 

Gastropods, in Ralston Creek formation______ 92 

Geltena gracilis.---------------------------- 100,102 

SP--------------------------------- 100, 102, 104 

Geographic setting •• _------------------:.----- .73 

Geology, economic ••• ----------------------- 114-117 

generaL.-------------------------------- 73-107 

historic •. ------------------------------- 113-114 

Glennon limestone member, Lykins formation.----------------------------- 90, 91 

Gneissic granite, Precambrian---------------- 81 

Graneros shale •••• ------------------------ 94-95,96 

Granite, gneissic, Precambrian_______________ 80 

Granite gneiss and migmatite _________________ 78-80 

Granitized metasedimentary rocks, Precambrian._---------- ___ -----_---_---_ 78-81 

Greenhorn limestone.------------------------ 95, 96 

Gudo, A. J. 3d, analyst.---------------------- 104 

Gummite _____ -------------------------------- 116 

GyraulU8 vetern'U8----------------------------- 92 

123 
124 

H 

Page 

Hamilton, J. C., analyst______________________ 117 

Harriman shale member, Lykins formation ___ 00,91 

Hartland shale member, Greenhorn limestone. 95, 96 

Helmer Bros. mines__________________________ 114 

Hlllside mine·-------------------------------- 114 

Hogback mine________________________________ 114 

Hoploacaphitea n. SP------------------------ 101,102 

Hornblende granite gneiss, Precambrian ______ 8o--81 

Hornblende, in lime silicate gneiss.___________ 78 

Hornblendite, Precambrian_----------------- 81-82 

Hurricane Hill reeL __ ------------------------ 116 

Hygiene sandstone member, Pierre shale _____ 99,103 

IchthuodecteB sp. (scales)._------------------ 101,102 

Inoceramus balchiL ------------------------ 100,102 

barabinL ------------------------------- 100,101 

bellvuenaia. _ ------------------------------ 94 

comancheanus ____ ___ ---- _______ --- _ ----- _ _ 94 

convexus •• ------------------------------ 100, 101 cucloidea ________________________________ 100,101 

deform is._----------------------------- ___ 97,98 fibroaus _____________________________ 100,101,103 

labiatus •••• ------------------------------- 95,96 

pertenuia_ ------------------------------ 100,101 

pictus. _ ---------------------------------- 95,96 

platinm _ --------------------------------- 98 

aagenBiB--------------------------------- 100,101 

BaBkatchewanenaiB----------------------- 100,101 

aublaeviB.------------------------ 99,100,101,103 

tenuilineatuB---------------------------- 100, 101 tvpicua ______________________________ 100, 101,103 

SP-------------------------------- 96, 97,100,101 

sp. (not deformiB)_________________________ 98 

Intrusive rocks, Precambrian _________________ 81-85 

Iron deposits.-------------------------------- 116 

J 

Jarre Creek fault, description _______________ 109,110 

in Fort Hays limestone___________________ 98 

in Fountain formation____________________ 88 

in Pierre shale ___________________________ 99,104 

sandstone dikes _____________________ ------ 86 

K 

Kassler sandstone member, South Platte formation._------------------------- 94 

L 

Laramie formation.------------------~----- 104-106 

Leaf prints._--------------------------------- 106 

Lehigh mine·------------------------------- 114, 115 

Lime silicate gneiss, Precambrian·---------/-- 77-78 

Limestone deposits ______________________ "____ 115 

Lincoln limestone member, Greenhorn 'limestone.--------------------: _______ 95, 96 

Lineation, contour diagram___________________ 108 

Lingula nitida. _ ---------------------------- 100,101 

Lytle and South Platte formations_______ 94 

Morrison formation _______________________ 93-94 

Niobrara formation _______________________ 97-98 

Pierre shale ______________________ 99, 103-104, 105 

Pikes Peak granite._--------------------- 83-84 

quartz diorite. ___ ------------------------ 81 

quartzite, Precambrian___________________ 74 

Ralston Creek formation._--------------- 91-92 

rhyolite._-------------------------------- 107 

sandstone dikes. ___ ---------------------- 86-87 

sillimanite granite gneiss_________________ 80 

sillimanitic biotite-quartz gneiss __________ 74-75 

Lipp, H. H., analyst------------------------- 116 

INDEX 

Page Lithology, amphibolite _______________________ 76-77 

andesite dikes____________________________ 107 

biotite-muscovite granite·---~----------- 82-83 

biotite-quartz gneiss______________________ 75 

Carlile shale ___________________________ 95, 96,97 

Dawson arkose _________________________ 105,106 

Fountain formation______________________ 88 

Fox Hills sandstone._------------------ 104,105 

gneissic granite___________________________ 81 

Graneros shale _________________________ 94-95.96 

grai:rlte gneiss and migmatite _____________ 79,80 

Greenhorn limestone._------------------- 95,96 

hornblende granite gneiss.---------------~ SQ--81 

hornblendite. __ -------------------------- 81-82 

Laramie formation._--------------------- 105 Lykins formation _________________________ 90-91 

Lyons sandstone _______________ : _________ 89-00 

Location, mineral suites, lime silicate gneiss.. 77 

quadrangle·------------------------------ 71,72 Lucina occidentalia __________________________ 100,102 

aubundata_ ----------------------------- 100,102 

SP-------------------------------~------ 100,102 Lykins formation _____________________________ 90-91 

Lumnaea morriaonenaia. __ -------------------- 92 

Lyons sandstone, description _________________ 89-00 

faults _________________________ ------______ 110 

Lytle and South Platte formations, description._---------------------------- 94 faults ________________ ----_________________ 110 

M 

Malachite.----------------------------------- 116 

Margaritella n. SP--------------------------- 100,102 

Meionite. See Scapolite. 

Membranipora SP--------------------------- 100,101 

Menuitea n. SP-------------------------- 101,102,103 

Mesozoic and Cenozoic sedimentary rocks ___ 91-106 

Metasedimentary rocks, Precambrian ________ 74-78 

Modes, amphibolite, even-grained____________ 76 

amphibolite, porphyroblastic_____________ 77 

biotite-muscovite granite_________________ 82 

gneissic granite___________________________ 81 

granite gneiss and migmatite_____________ 79 

hornblende granite gneiss________________ 81 

hornblendite______ _ __ _ __ _ _ _ _ _ _ _ _ _ __ __ _ _ _ __ 82 

Pikes Peak granite._--------------------- 84 

quartz diorite·-----------------------~---- 82 

quartzite, Precambrian___________________ 74 

sandstone dikes___________________________ 86 

sa watch quartzite. __ --------------------- 86 

slllimanite granite gneiss__________________ 80 

slllimanitic biotite-quartz gneiss__________ 75 

Miarolitic cavities, Pikes Peak granite________ 83 

Mica deposits._------------------------------ 114 

Migmatite. See Granite gneiss and migmatite. 

Mineral deposits, metallic __________________ 115-117 

nonmetallic_____________________________ 114-115 

Mineralogy, granite pegmatites _______________ 84-85 

Minerals, in lime silicate gneiss_______________ 78 

Modiolm meekL---------------------------- 100, 101 

Mollusks, Morrison formation________________ 93 

Morgan's mine_______________________________ 115 

Morrison formation ___________________________ 92-94 

Mountjoy, Wayne, analyst___________________ 116 

Muscovite, in lime silicate gneiss._----------- 78 

N 

Nemodon sulcatinus _________________________ 100, 101 

Niobrara formation ___________________________ 97-99 

Noddle Heads, Pikes Peak granite outcrop___ 83 

Nucula planimarginata _____________________ 100,101 

sp_ -------- _ ---------------------------- 100, 101 

Nuculana evansi._; ___ ~--------------------- 100,101 

n. sp ____ ------------------------------- 100, 101 

0 

Page 

Origin, biotite-muscovite granite_____________ 83 

Fountain formation______________________ 109 

Lykins formation .... ---------.------------ 91 

Lyons formation__________________________ 90 

Pikes Peak granite_______________________ 84 

Ralston Creek formation_________________ 92 

Ostrea (Alectrvonia) lugubris__________________ 95 

beloitL.----------------------------------- 95,96 conge8ta ___________________________________ 97,98 

elegantula ____ ___________ . _____ . _ _ _ _ _ _ _ _ _ _ _ 95 

inornata .. ------------------------------ 100, 101 lugubriB _______________________________ ---- 96 

SP----------------------------------- 95,100,101 Oxvbeloceras crauum ________________________ 100,102 

SP-------------------------------------- 100, 102 

p 

Pachydiscid ammonite _____________________ 101,102 

Paleozoic sedimentary rocks __________________ 85-91 

Peck, R. E., fossil identification______________ 92 

Pecten nebraBcemiB __________________________ 100,101 

(Svncvclonema) halliL __________________ 100, 101 

Pegmatites, granite, Precambrian ____________ 84-85 

in biotite-muscovite granite .. _----------- 82-83 

in Pikes Peak granite _____________________ 83,84 

Pelecypod, genus undetermined ____________ 100,102 

Petrified wood·----------------------------- 101,102 

PeroniceraB sp __ ------------------------------ 97 

Phosphatic nodules, Pierre shale ____________ 103-104 

Pierre shale, description _____________________ 99-104 

folds ____ ------ __________________________ ._ 111 

Jarre Creek fault_________________________ 109 

Piestochilus SP------------------------------ 100,102 

Pikes Peak granite, Precambrian _____________ 83-84 

Placenticeras intercalare _____________________ 101,102 

meekL.----------------------------- 101,102,103 

sp. ______ -~ _________________________ . __ _ 101, 102 

Plainview sandstone member, South Platte 

formation _______ ---- __ --- ______ --- 94 

Platte Canyon Fuel and Power Co., (prob- able) mine No. L_________________ 114 

mine No.2_------------------------------ 115 

Polinices SP--------------------------------- 100, 102 

Precambrian, metamorphic and igneous rocks. 74-85 

Prionocuclus wuomingenaiB.------------------- 95,96 Pteria linguaeformia _________________________ 100, 101 

aalinenaia .. ______ --------- _--------------- 94 

SP-------------------------------------- 100, 101 

Ptygmatic folds, granite gneiss and migma- tite .• __ _ ___ __ __ _ __ ___ __ _ _ _ __ _ _ _ _ _ _ 80 

Pyrite, in lime silicate rock___________________ 78 

Q 

Quartz diorite, Precambrian__________________ 81 

Quartz, in lime silicate ~meiss.________________ 78 

Quartzite, Precambrian. __ ------------------- 74 

R 

Radium and radon, analysis in spring water 

from Stevens Gulch______________ 117 

Ralston Creek formation.-------------------- 91-92 

Reeside, J. B., fossil identification____________ 92 

Rhamnus goldianus.-------------------------- 106 

Rhyolite. ____ -------------------------------- 107 

Road metaL •... ----------------------------- 115 

Rogers dike. __ ------------------------------- 86 

s 

Sand deposits .. _----------------------------- 115 

Sandstone dikes, description __________________ 85-86 

process of emplacement ___________________ 87-88 

source of sand.--------------------------- 86-87 
Page. 

Sawatch quartzite, compared to sandstone 

dikes.--- ____________ ----_________ 87 

Scaphites corvensis •• -------------------------- 95 nigricoUensia •• _ •• ________ •• ______________ .. 95 

whitfieldL ••••••• ____________ ----. __ _ __ __ _ 95 

Scaphopod, undetcrmtned __________________ 100, 102 

Scapoltte, in lim~ stllcate gneiss.-------------- 78 

Schuch, J.P., analyst------------------------ 104 

Sdponoceras gracile.-------------------------- 95 

Sedimentary rocks, Mesozoic and Cenozoic •• 91-106 

Paleozoic.------------- ____ ------------ ___ 85-91 

Selenite crystals.----------------------------- 99 

Shark teeth, Carllle shale--------------------- 95 

S111ca sand, quarry, South Platte formation___ 94 

SUllmantte granite gneiss, Precambrian_______ 80 

Stlltmnnttie biotite-quartz gneiss, Precambrian ••••••• ---------------------- 74-75 

Skinner, D. L., analyst----------------------- 116 

Smitbsonlte. __ ---------------------- _ __ __ __ 116 

Smoky Hm shale member, Niobrara formation •• ------------------------- 97, 98-99 Solenoceras mortonf. ________________________ 100,102 

SP-------------------------------------- 100, 102 South Platte formation .. See Lytle and South 

Platte formations. 

Sphenodiscus SP----------------------------- 101. 102 

Stone, structural.---------------------------- 115 

Strain shale member, Lykins formation _______ 90,91 

Strottgraphlc section, Carllle shale ____________ 95-96 

Dawson arkose--------------------------- 105 

Fox Hills sandstone._------------------ 104, 105 

Graneros shale-------------------~-------- 96-97 

Greenhorn limestone.-------------------- 96 Laramie formation________________________ 105 

Lykins formation _________________________ ~1 

INDEX 

Page 

Lyons sandstone. __ ---------------------- 90 

Morrison formation----------------------- 93-94 

Mowry shale equivalent __________________ 96,97 

Niobrara formation _______________________ 97-98 

Pierre shale ... ---------------------------- 105 

Ralston Creek formation __ --------------- 91-92 

Strotlflcatlon, Fountain formation____________ 88 

Structure, granite gneiss and mlgmatite______ 80 Lnromide _______________________________ 109-112 

Niobrara formation_______________________ 98 

Pennsylvantan_ ------------------------ 108-109 

Pierre shale·------------------------------ 99 

post-Laramide •••• _----------------------- 112 

Precambrlnn ••• --------·---- __ --------- 107-108 

sUllmanite granite gneiss------------------ 80 

T 

Tanner, A. B., analyst----------------------- 117 

TeUina scitula. _ ---------------------------- 100, 102 

Tenorite ••••• ------- ____ ----------- ___ ------ _ _ 116 

Terebratula helena.-------------------------- 100, 101 

ThalmanineUa greenhornemia__________________ 95 

Thin sections, amphiboltte. _ ----------------- 76 

andesite dikes.---------------------------- 107 

biotite-muscovite granite_________________ 82 

gneissic granite·-------------------------- 81 

hornblende granite gneiss_________________ 81 

Pikes Peak granite._--------------------- 84 

sillimanitic biotite-quartz gneiss__________ 75 

Titanite, ln lime sUlcate gneiss________________ 78 

Todd, Ruth, fossflidentlflcation______________ 95 

Tourmallne, ln pegmatites____________________ 85 

Tremollte, ln lime silicate gneiss______________ 78 

Turquoise _______ --------------- __ ------------ 116 

125 

u 

Page 

Unnamed sandstone unit, South Platte 

formation ________ • _______ .________ 94 

Unnamed shaly unit, Soutb ·Platte formation. 94 

Uranlnite _______ ------- ________________ • _. _ _ __ 116 

Uranium deposits __ ------------------------ 116-117 

Ute P8SS fault-------------------------------- 87 

v 

Van Bibber shale member, South Platte 

formation ____________________ .____ 94 

Vesuvlanite, ln lime silicate gneiss____________ 78 

w 

Weathering effectsbiotite-muscovite granite_________________ 82 

Carllle shale______________________________ 95 

Fountain formation______________________ 88 

Graneros shale~-------------------------- 95 

Morrison formation.. _____ ----------------- 93 

Niobrnro formation_______________________ 98 

Pierre shale. ____ ------------------------- 99 Pikes-Peak granite _______________________ 83,84 

quartz diorite and hornblendite__________ 81' 

slliimanite granite gneiss_________________ 80 

sllllmanitic biotite-quartz gneiss _____ ----- 74-75 

Wilcox, R. E., tbln section examlnatlon______ 107 

Wlliow Creek mine.-------------------------- 115 

y 

Yoldia eoanai. _. _ ----------------------------- 104