Geology of the 

Connors Pass Quadrangle 

Schell Creek Range 

East-Central Nevada 

By HARALD DREWES 

GEOLOGICAL SURVEY PROFESSIONAL PAPER 557 

Stratigraphy and structure of a 

complexly deformed area in the 

Basin and Range province, and an 

evaluation of the tectonic environment 

in which it was developed 

l 

PUBLICAT W~lS :- ,, .. ,, 

'· \ !~· ~ -

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON : 1967 
UNITED STATES DEPARTMENT OF THE INTERIOR 

STEW ART ~. UDALL, Secretary 

GEOLOGICAL SURVEY 

William T. Pecora, Director 

Library of Congress card-catalog No. GS 67-190 

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

Washington, D.C. 20402- Price (paper cover) 
CONTENTS 

Abstract __________________________________________ _ 

Introduction ______________________________________ _ 

Objectives and methods ________________________ _ 

Acknowledgments ______________________________ _ 

Geography ____________________________________ _ 

Geologic setting _______________________________ _ 

Stratigraphy ______________________________________ _ 

Precambrian System ___________________________ _ 

Metasedimentary rocks _____________________ _ 

Cambrian System ______________________________ _ 

Prospect Mountain Quartzite ________________ _ 

Pioche Shale ______________________________ _ 

Pole Canyon Limestone _____________________ _ 

Lincoln Peak Formation ____________________ _ 

Metamorphism of Precambrian and Cambrian rocks_ 

Cambrian and Ordovician Systems _______________ _ 

Limestone ________________________________ _ 

Shale member _________________________ _ 

Fauna, age, and correlation _____________ _ 

Ordovician System _____________________________ _ 

Eureka Quartzite __________________________ _ 

Fish Haven Dolomite ______________________ _ 

Silurian System ________________________________ _ 

Laketown Dolomite ________________________ _ 

Devonian System ______________________________ _ 

Sevy Dolomite ____________________________ _ 

Simonson Dolomite ________________________ _ 

Guilmette Formation _______________________ _ 

Member a ____________________________ _ 

Memberb ____________________________ _ 

Member c ____________________________ _ 

Member d ____________________________ _ 

Fauna, age, and correlation _____________ _ 

Environment ______ ____________________ _ 

Devonian and Mississippian Systems _____________ _ 

Pilot Shale ________________________________ _ 

Mississippian System ___________________________ _ 

Joana Limestone ___________________________ _ 

Chainman Shale ___________________________ _ 

Mississippian, Pennsylvanian, and Permian Systems_ 

Ely Limestone _____________________________ _ 

Permian System _______________________________ _ 

Rib Hill Sandstone ________________________ _ 

Arcturus Formation ________________________ _ 

Lithology _____________________________ _ 

Conglomerate member ___ .:: ______________ _ 

Fauna, age, and correlation _____________ _ 

Page. 

1 

2 

2 

2 

2 

4 

7 

7 

7 

7 

7 

9 

10 

12 

14 

16 

16 

17 

18 

18 

18 

20 

21 

21 

22 

22 

24 

25 

26 

27 

28 

28 

28 

28 

29 

29 

35 

35 

37 

41 

41 

43 

43 

48 

49 

49 

50 

Stratigraphy-Continued 

Jurassic, Cretaceous, and Tertiary(?) Systems _____ _ Porphyritic rhyolite ________________________ _ 

Cretaceous or Tertiary System __________________ _ 

Shale and tuffaceous sandstone ______________ _ 

Tertiary System __________ _____________________ _ 

Basaltic andesite vitrophyre __ ________ _______ _ 

Conglomerate _____________________________ _ 

Quartz latite vitrophyre ____________________ _ 

Latitic rocks ______________________________ _ 

Welded tuff lenses _____________________ _ 

Intrusive bodies of quartz latite vitrophyre_ 

Upper lava flow of quartz latite vitrophyre_ 

Environment, age, and correlation _______ _ 

Dacite vitrophyre __________________________ _ 

Intrusive rocks _______ -~--- ____________ _ 

Tuff lenses ____________________________ _ 

Environment, age, and correlation _______ _ Fanglomerate _____________________________ _ 

Quaternary System ____________________________ _ 

Older alluvial and fan graveL _______________ _ 

Younger alluvial and fan graveL ____________ _ 

Lacustrine deposits ________________________ _ 

Alluvial sand and graveL ___________________ _ 

Structural geology _________________________________ _ 

Structural features of Mesozoic(?) age ____________ _ 

Schell Creek Range thrust fault _____________ _ 

Structure of the lower major thrust plate _____ _ 

Structure of the upper major thrust plate _____ _ 

Structural features of middle or late Tertiary age __ _ 

Structural features of late Tertiary or early Pleisto- cene age ____________________________________ _ 

Structural features of late Pleistocene or Recent age_ 

Origin of structure ______________ ________ --------

Glide faults _______________________________ _ 

Thrust faults ______________________________ _ 

Regional uplift and normal faults ____________ _ 

Economic geology ______ ____________________________ _ 

Taylor mining district _________________ _________ _ 

Cleve Creek district ____________________________ _ 

Mineralization near Majors Place ________________ _ 

Other mineralization ___________________________ _ 

General geochemistry ___________________ --------

Geologic history ___________________________________ _ 

References cited ___________________________________ _ 

Index-----------------~---------------------------

III 

Page 

51 

51 

53 

53 

53 

53 

53 

56 

58 

58 

58 

59 

59 

59 

60 

62 

62 

62 

62 

62 

63 

63 

64 

64 

66 

66 

67 

68 

70 

72 

73 

73 

74 

75 

77 

77 

77 

82 

82 

83 

83 

86 

88 

91 
IV 

PLATE 

FIGURE 

CONTENTS 

ILLUSTRATIONS 

[Plates are in pocketl 

1. Geologic map and structure sections of the 

Connors Pass quadrangle. 

2. Tectonic map showing structures by type and 

age. 

3. Isometric diagram of the Steptoe Creek-Cave 

Creek area. Page 

1. Index map showing location of the Connors 

Pass quadrangle_____________________ 3 

2. Stratigraphic sections of Pioche Shale____ 10 

3. Stratigraphic section of upper part of 

Lincoln Peak Formation______________ 13 

4-10. Photographs: 

4. Typical outcrop of white Eureka 

Quartzite_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 20 

5. Typical bed of Fish Haven Dolomite ________________________ 21 

6. Typical ledge of the lower alternating member of the Simonson 

Dolomite_____ _______________ 24 

FIGURE 

TABLES 

Page 

7. Typical exposure of basal thickbedded limestone of member a 

of the Guilmette Formation __ _ 

8. Ledges of Ely Limestone _______ _ 

9. Massive outcrops of the lower unit 

of the Eocene conglomerate ___ _ 

10. Details of sorting, roundness, and 

size of clasts in Eocene conglomerate __________________ _ 

11. Tectonic map of region surrounding ·the 

Connors Pass quandrangle ___________ _ 

12. Drawings showing comparison between 

idealized and actual patterns of fault 

deformation __________ ____________ · __ _ 

13. Geologic map of Taylor mining district __ _ 

14. Map showing distribution of lead, copper, 

and zinc in alluvium in the Connors 

Pass quandrangle ___________________ _ 

. TABLE 1. Generalized section of rocks exposed in the TABLE 10-12. Chemical and semiquantitative spectroConnors Pass quandrangle ________ __ _ 4 graphic analyses of: 

2-4. Fauna of: 10. Porphyritic rhyolite ___________ _ 

2. Unnamed limestone of Ordovician 11. Rocks from Egan and Schell 

age ________________________ _ 19 Creek Ranges _______________ _ 

3. Guilmette Formation __________ _ 30 !'2. Dacite vitrophyre _____________ _ 

4. Joana Limestone ______________ _ 

5. Semiquantitative spectrographic analyses 

of black shale ______________________ _ 

6-9. Fauna of: 

6. Chainman Shale ______________ _ 

Production record of the Taylor mining 

district ___________ _________________ _ 

Semiquantitative analyses of: 

14. Rocks from the Taylor mining 

36 13. 

38 14-16. 

40 

7. Ely Limestone _______________ _ 

8. Lowermost 100 feet of Rib Hill 

district _______________ _____ _ 

15. Lead, copper, and zinc content of 

45 

Sandstone ___ _______________ _ 48 alluvium ___________________ ~ 

9. Arcturus Formation ___________ _ 50 16. Alluvium _________ --------- --

Page 

26 

42 

54 

54 

65 

75 

80 

85 

Page 

52 

57 

61 

79 

81 

84 

84 
GEOLOGY OF THE CONNORS PASS QUADRANGLE, SCHELL CREEK RANGE, EAST-CENTRAL 

NEVADA 

By HARALD DREWES 

ABSTRACT 

The Connors Pass quadrangle lies southeast of Ely and covers 

a moderately rugged area in the central part of the Schell Creek 

Range, largely north of Connors Pass. 

The stratigraphic column in the area is about 5 miles thick 

and comprises rocks of late Precambrian to Recent age. Only 

a . few hundred feet of upper Precambrian rock consisting of 

slightly metamorphosed quartzite and slate is present. Paleozoic. rocks, about 23,000 feet thick and reflective of three major 

environmental changes, make up most of the section. The 

Paleozoic sequence begins with the clastic rocks of the Prospect 

Mountain Quartzite and Pioche Shale, whose grains are fine to 

moderately coarse and only moderately rounded and clean and 

it continues with the dominantly calcareous rocks of the' Pole 

C~nyon Limestone and the Lincoln Peak Formation. Above 

this sequence is a unit of undifferentiated Cambrian and Ordovician age that is identical to Hague's (1883) Pogonip Limestone. Locally some of these formations are slightly metamorphosed. 

.The overlying middle Paleozoic rocks consist mainly of dolomite, but also include a little quartz sandstone composed of 

well-ro.unded clean grains. They include the Eureka Quartzite 

and Fish Haven Dolomite, of Ordovician age, the Laketown 

Dolomite, of Silurian age, and the Sevy Dolomite Simonson 

D~lomite, a~~ the Guilmette Formation, all of De~onian age. 

Disconformities probably separate the Silurian rocks from 

both older and younger rocks. 

. The upper Paleozoic rocks consist mainly of .limestone but 

mclude much impure siltstone and sandstone containing poorly 

rounded grains. The impure sandstone first appears in the 

upper .part of th~ Guilmette Formation, which is successively 

overlam by ~he Pilot Shale; of Devonian and Mississippian age, 

the Joana ~Imestone and Chainman Shale, of Mississippian age, 

th.e Ely Limestone, of Mississippian, Pennsylvanian, and Permian age, and the Rib Hill Sandstone and Arcturus Formation 

both of Permian age. A little gypsum occurs in the Chainma~ 

Sha~e and ~ossibly also in the upper part of the Arcturus FormatiOn, which contains a thick wedge of chert-pebble conglomerate: . The continuity of sedimentation was broken by discon-

~ormibes probably near the end of the Devonian and certainly 

m ~ate Pennsylvanian time. The upper Paleozoic rocks were 

denved from areas at least partly exposed by orogenic uplift; 

such are~s, probably 100-200 miles distant, lay northeast, west, 

and possibly southeast of the Connors Pass area. 

The Mes?zoic and Tertiary rocks are poorly represented. 

Between Middle Jurassic time and early Tertiary time the area 

was ~trongly u~l~fted, g~eatly faulted, and intruded by granophyric po~phyritlc rhyolite dikes, which are probably related 

~o monzomte stocks in the adjacent ranges. At some time durmg the Cretaceous or Paleocene, black shale, tuffaceous sandstone, and conglomerate were deposited in a terrestrial environment. 

During Eocene and Oligocene(?) time, as much as 6,000 feet 

of volcanic rock and terrestrial red conglomerate, originating 

in the Schell Creek ·Range and in the Snake Range immediately 

to the east, was deposited on a piedmont surface of moderate 

relief. Volcanism began with a relatively small extrusion of 

latite lava and tuff, which was followed by widespread extrusions of dacitic lava and tuff. Conglomerate of very local origin 

was deposited unconformably on the volcanics and the underlying red conglomerate, perhaps during Pliocene time. During 

Quaternary time, pediment and alluvial gravels were spread 

along the flanks of the Schell Creek Range and far into the 

adjacent valleys. During late Pleistocene time a pluvial lake 

occupied Spring Valley, east of the Schell Creek Range, and 

its lacustrine and beach deposits are probably interbedded with 

the youngest part of a gravel formation of Pleistocene age. 

The rocks are much faulted and locally folded. Most of the 

structural features are relatively simple, but the outcrop patterns along the Schell Creek Range thrust fault are moderately 

complex because faults different in age and direction of movement share fault surfaces. The oldest faults, probably of Mesozoic age, are chiefly low-angle faults almost parallel to bedding 

planes. Beds adjacent to these faults dip into the fault planes 

in many places, and along the faults beds are cut out rather 

than repeated. Along the Schell Creek Range thrust fault, rocks 

as young as the Arcturus Formation are thrust onto rocks of 

Late Cambrian and Early Ordovician age, and in some places 

about 2.5 miles of strata is missing; in other places faults do 

not commonly cut out more than a few hundred to a few thousand feet of strata. Some faults seem to die out along their 

courses; some merge into adjacent thrust faults or are truncated by thrust faults higher in the section; and others abut 

against or merge into tear faults. Rocks within the thrust 

plates are broken by normal and reverse faults, many of which 

are restricted to a particular plate or group of plates. Northeastward or southwestward movement of the upper plates relative to the lower plates is indicated by the alinement of axes 

of drag folds, by tear faults, and by other minor structural features, but the direction of absolute movement is less certain ; 

the upper plates may have been displaced northeastward with 

respect to the lower ones. All the thrust faults of this region 

have been dated as Late Jurassic or Early Cretaceous. The 

origin of the low-angle faults is not entirely clear, but regional 

relations indicate that the lower ones are thrust faults and that 

the upper ones may be either thrust faults or glide faults 

(faults directly of gravity origin in which horizontal stresses 

are absent or minor). 

Some normal faults of middle Tertiary age may be as old as, 

or older than, some of the volcanic vents which are alined along 

1 
2 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

these faults. Other faults of this general age cut the Eocene 

conglomerate, and Eocene and Oligocene ( ? ) volcanic rock and 

produced typical Basin and Range topography. One of the 

larger normal faults was locally deflected along a rather steeply 

inclined part of the Schell Creek Range thrust fault. 

During middle or late Tertiary time, two plates of Tertiary 

rocks, the larger several square miles in extent, slid westward 

as much as 3,500 feet from an upfaulted part of the range onto 

the adjacent downdropped block. The plates moved partly 

along a surface close to the Schell Creek Range thrust fault and 

partly on the Chainman Shale of the upper thrust plate. The 

parts of the glide plates nearest their source were tilted with 

a reverse rotation, such as commonly occurs in slump blocks, 

and were warped into open synclines during the process of 

gliding. A few normal faults of late Tertiary and Quaternary 

age cut the glide plates and also the gravel older than the late 

Pleistocene lacustrine deposits. The only range-front fault recognized trends southwest and extends into the northeast corner 

of the area. 

The mines in the quadrangle have yielded $1-$2 million worth 

of silver and a small amount of lead, copper, zinc, gold, antimony, and tungsten. In the principal mining area, the Taylor 

district, silver ore is scattered in silicified bodies that replace 

parts of the Guilmette Formation and the Joana Limestone 

near northeast-trending faults. The mineralization may be 

genetically related to the granophyric porphyritic rhyolite dikes, 

which are concentrated in the district. Some mineralization 

occurs along Cleve Creek, near Majors Place, and in Tamberlaine Canyon. A cursory spectrographic study reveals anomalously high amounts (as much as 0.1 percent) of several metals, 

including silver, copper, and zinc, in some parts of the Chainman Shale, but these anomalies are- so localized that they seem 

to be related to sedimentation or diagenetic processes rather 

than to later mineralization. Reconnaissance geochemical prospecting indicates that average background values for copper, 

lead, and zinc in alluvium are 20 ppm (parts per million), 25 

ppm, and 25 ppm, respectively. Slightly greater amounts of 

zinc are in alluvium derived from Chainman Shale. 

INTRODUCTION 

The Connors Pass quadrangle (fig. 1), an area of 

207 square miles, lies 7-25 miles southeast of Ely, in 

east-central Nevada. It straddles the south-central 

part of the Schell Creek Range. Spurr ( 1903, p. 

38-4 7) briefly described parts of the range. Young 

( 1960a, b) mapped the northern part of the range, 

and Tschanz and Pampeyan (1961) mapped the extreme southern part of the range. Brief descriptions 

of several of the mining districts in the range have 

been published (Hill, 1916; Roberts, 1942; Couch and 

Carpenter, 1943). Slightly more geologic work had 

been done in the Snake Range to the east and considerably more in the Egan Range to the west than 

had been done in the Schell Creek Range, but less 

than a fifth of the total area of the three ranges had 

been mapped when this study began. 

OBJECTIVES AND METHODS 

This area was selected for geologic study chiefly 

because it is representative of a part of the Great 

Basin that contains a variety of complex and unusual 

structural features. Few geologic studies have been 

made in this general region, and these have been 

largely of reconnaissance type. The area was especially attractive because of its location between two other 

areas in which detailed geologic studies are currently 

in progress; one of these is in the southern Snake 

Range, to the southeast, and the other in the Egan 

Range, to the west. The combined knowledge obtained 

by the three studies should lead to a fairly comprehensive understanding of the stratigraphy, structure, 

and mineral deposits of a large part of eastern Nevada. 

This geologic study was designed to obtain a representative stratigraphic section, to determine the relations between numerous low-angle faults, steep normal 

faults, intrusive bodies, and mineral deposits, and 

particularly to gain a better understanding of the 

origin of the low-angle faults. A geochemical reconnaissance was also made for guidance in prospecting. 

The report is based on 190 days of fieldwork from 

the fall of 1958 through the fall of 1961. The geology 

was mapped (pl. 1) on a topographic base at a scale 

of 1 : 48,000. Geologic mapping was facilitated by 

the use of a sketchboard and on open-sight alidade. 

High-altitude aerial photographs were used chiefly in 

mapping valleys, for elsewhere the geologic features 

are too complex to be mapped on the photographs. 

About 750 samples were collected; these consisted of 

three groups roughly equal in number-petrographic, 

geochemical, and paleontologic. 

ACKNOWLEDGMENTS 

I was assisted in the field by J. 0. Gallagher in 

1959, B. M. Irvine in 1960, and E. J. Young in 1961. 

I also benefited from conversations in the field with 

W. H. Easton, Carew McFall, A. R. Palmer, R. K. 

Hose, and H. R. Christner. Mackenzie Gordon, Jr., 

furnished the unpublished results of his studies of a 

suite of fossils collected in · the area by him, Hose, 

and C. A. Repenning. 

.GEOGRAPHY 

Linear mountain ranges, separated by broad, flat 

valleys, -are typical physiographic features of the 

central part of eastern Nevada. The Connors Pass 

quadrangle is in a part of the Schell Creek Range 

that is transitional between a more rugged topography 

to the north and a less rugged topography to the 

south. Spring Valley, which lies east of this quadrangle, forms a closed drainage basin having a floor 

less than 6,000 feet above sea level. Steptoe Valley, 

west of the range, is largely at an altitude of less than 

7,000 feet and drains northward into two closed depressions. 
0 5 10 15 

INTRODUCTION 

20 25MILES 

>-

ILl 

....J 

....J 

<( 

> 

3 

,--------~-----l 

I I ~ L--1 

I Iko I VosALT LAKE 

Reno 8il CITY \ 

~ 0:Jy 0 Delta \ 

', I 

' I I ', I oCedar City J """ ~----- ' 'Las Vegas} I 

~\ ') 

0 50 100 150 MILES 

FIGURE I.-Index map showing location of the Connors Pass quadrangle. 

Many roads and tracks give relatively easy access 

to most of the area, although only one ranch and 

Majors Place, are inhabited. Paved highways cross 

Connors Pass and lie close to most of the east and 

west edges of the quadrangle. Several graded access 

roads and many smaller roads are shown on the 

topographic map. There are also several unmapped 

tracks that are passable to vehicles having four-wheel 

drive: to Summit Spring from the southeast; eastward nearly to E,ast Canyon Spring; to Crethers 

Springs from the north; from the nearest part of the 

Nevada National Forest boundary to a treeless area 
4 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

about 1.75 miles southwest of Bastian Spring; along 

the fence on the western boundary of the ·national 

forest. 

Eastern Nevada has a semiarid temperate climate 

with a strongly seasonal orographic influence. Climatic data have been recorded by the U.S. Weather 

Bureau (1957) at several stations near the quadrangle 

for at least 10 years, and a few years ago a station 

at which only general data are collected was set up 

at Connors Pass. 

There are some streams and springs in the mountains of the northern half of the quadrangle, but 

observations made during years of average to belowaverage rainfall show that water also flows perennially in a half-mile segment of the canyon -northwest of the Kolcheck mine in the Cleve Creek area, 

in a 1-mile segment of the canyon midway between 

Kolcheck Basin and Cottonwood Spring, in all the 

valley extending from Clear Spring to Steptoe Creek, 

and in a half-mile segment below the spring in an 

unnamed valley tributary to Steptoe Creek from the 

west. There are also moderately large unmapped 

springs a quarter of a mile southwest of East Canyon 

Spring, and in the mouth of a cave in the narrow 

canyon midway between the Kolcheck Basin and 

Cottonwood Spring. The spring mapped half a mile 

north of the abandoned Taylor townsite has been dry 

for years. The largest springs in the quadrangle are 

Cave Springs, Clear Spring, and the unnamed $pring 

a third of a mile northwest of Clear Spring; all are 

near the junction of Cave Creek and Steptoe Creek. 

GEOLOGIC SETTING 

Upper Precambrian and Paleozoic sedimentary 

rocks underlie most of the mountainous part of the 

quadrangle, but Tertiary volcanic and sedimentary 

rocks and Quaternary deposits (table 1) underlie small 

TABLE !.-Generalized section of rocks exposed in the Connors Pass quadrangle 

Age Formation Thickness, estimated (feet) 

Recent Alluvial sand and 0--100+ 

gravel. - Unconformity 

Lacustrine silt, sand, 0--100+ and gravel. Quaternary -Unconformity(?) 

Pleistocene Younger alluvial and 

fan gravel. 0--100+ 

- Unconformity(?) - Older alluvial and fan 

gravel. {}-;-200+ 

------- -Unconformity - Pliocene(?) Fanglomerate 0--600+ 

-------- - Unconformity - Oligocene(?) Dacite vitrophyre 0--1, 200+ and Eocene 

Latite tuff 0--2,000 

~----------

Tertiary Eocene 

Quartz latite vitro- 0--300 phyre. 

Conglomerate 

0--100+ 

---------------- ------------Unconformity 

Basaltic andesite ---- vitrophyre. 

-Unconformity(?) - Tertiary or Shale and tuffaceous 

Cretaceous sandstone. 50± 

Tertiary(?), - Unconformity -

Cretaceous, Porphyritic rhyolite ---- and Jurassic 

----------------------------

Lithology 

Unconsolidated sand and gravel in lowest 

stream terraces. 

Unconsolidated silt and sand, and bars of 

rounded gravel. 

Very weakly indurated sand and gravel in low 

stream terraces and fans that have a slightly 

mature morphology. 

Very weakly indurated sand and gravel in high 

stream terraces and fans that have a mature 

morphology. 

Weakly indurated fanglomerate of locally derived coarse subangular fragments. 

Lava flows, tuff, and intrusive bodies. 

Light-gray massive tuff and local lenses of 

welded tuff. 

Lava flow underlying conspicuous brownishgray cliff. 

Reddish-gray to yellowish-gray conglomerate 

of coarse subangular fragments derive d 

a 

d locally and from adjacent ranges; contains 

lens of fresh-water limestone near base an lenses of tuff near top. 

One small dike. 

--

Black shale and mudstone ' and light-gray 

tuffaceous sandstone in one small down 

faulted block. 

Altered granophyric dikes, probably associate d 

with silicification and mineralization an d 

possibly associated with an unexposed plu 

tonic body. 
INTRODUCTION 5 

TABLE I.-Generalized section of rocks exposed in the Connors Pass quadrangle-Continued 

Age Formation Thickness, esti- Lithology 

mated (feet) 

Unconformity 

Pale-yellow-brown siltstone and sandstone and 

interbedded medium-gray shaly limestone; 

possibly contains a little gypsum; 500-1,000 

ft; probably as young as Leonard age. Arcturus Formation 2, 000-3, OOO+ Reddish-brown conglomerate of rounded 

chert and quartzite pebbles derived from a distant source; 0-500 ft. Medium-gray 

shaly limestone, reef limestone, and paleyellow-brown limy siltstone; 1,500-2,000 ft; 

Permian Early Permian of W olfcamp age. 

Rib Hill Sandstone 1, OOO+ Pale-yellow-brown fine-grained sandstone. 

Light-gray limestone and pale-yellow-brown 

siltstone; contains thin local basal con- glomerate; 500-800 ft; of Wolfcamp age. 

2, 500± Light-gray shaly limestone and pale-yellow- Ely Limestone brown siltstone. Chaetetes-bearing beds at 

base; 500-600 ft. 

Pennsyl- Middle and Early -Unconformity- Light-gray to medium-gray medium-to-thickvanian and Pennsylvanian bedded cherty limestone; 1,400 ft; locally Mississip- includes some rocks of Mississippian age rll pian at base. ::l 

e 

(!:) Dark-gray clay-shale containing a little sand- Late ~ Mississippian Chainman Shale 1,100± stone, conglomerate, and limestone, and 0 traces of gypsum. ..0 Mississip-

~ pian 0 Early Medium-gray bioclastic cherty massive to 

Mississippian Joana Limestone 300-500 thick-bedded limestone. 

Mississip- Early Dark-gray shale and siltstone that weather 

-- pian and Mississippian Pilot Shale 320-480 to yellowish-brown and reddish-brown plates; Devonian and contains a little quartzite, argillite, and 

Late Devonian limestone. 

Unconformity (?) 

Sandstone and conglomerate overlain by shaly 

limestone and reef limestone; 600± ft; 

only very locally preserved. 

Bluish-gray cherty limestone and shaly limestone; local lenses of dark-brown coarse- Late and Guilmette Formation 2, 000± grained dolomite; 400-600 ft. 

Middle Devonian Dark-brown coarse-grained dolomite, interbedded shaly limestone, and a sandstone 

unit; 300-700 ft. 

Blue-gray thick-bedded cliff-making limestone 

above a basal silty dolomitic limestone; 

Devonian 

500-600 ft. 

L~ght-brown and dark-brown laminated coarse- grained dolomite; 150 + ft. 

Middle Simonson Dolomite 

Dark-brown coarse-grained cliff-forming doloDevonian 600-700 mite; 100+ ft. 

Light-brown and dark-brown laminated coarse- grained dolomite; 150+ ft. 

"' Pale-brown coarse-grained dolomite; 200+ ft. --------- Middle(?) and Sevy Dolomite 900+ Medium-gray fine-grained dolomite that 

Earlv Devonian weathers light gray. 

Silurian Middle and Unconformity 

Laketown Dolomite 600-700 Light-gray coarse-grained thick-bedded 

Late Silurian dolomite. 

Unconformity(?) 

Late Ordovician Fish Haven Dolomite 400-500 Dark-brown coarse-grained dolomite; contains 

Ordovician 

interbedded gray dolomite near the top. 

Middle Eureka Quartzite 300-400 Very light gray to pinkish-gray thick-bedded 

Ordovician quartzite. 
6 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

TABLE !.-Generalized section of rocks exposed in the Connors Pass quadrangle-Continued 

Age Formation 

Ordovician and 

Cambrian 

Cambrian 

Late Precambrian 

Middle and 

Early Ordovician and 

Late 

Cambrian 

Late and 

Middle 

Cambrian 

Middle 

Cambrian 

Middle and 

Limestone 

Lincoln Peak Formation 

Pole Canyon Limestone 

Early Pioche Shale 

Cambrian 

Early Cambrian Prospect Mountain 

Quartzite 

Metasedimentary 

rocks 

areas. The major valleys are almost entirely underlain by Quaternary deposits. Within the quadrangle 

the Precambrian and Paleozoic rocks form a marine 

sequence almost 5 miles thick that consists dominantly 

of limestone and dolomite but that also contains considerable quartzite and shale. The lithology and 

thickness of the sequence is fairly uniform throughout much of western Utah and eastern Nevada. The 

continuity of sedimentation was broken, however, by 

disconformities in Middle and Late Pennsylvanian 

time, probably by one in the Early Silurian and one 

in the Late Silurian, and possibly by one in the Late 

Devonian. Rocks of Late Permian through early 

Tertiary age are, with few exceptions, absent. Middle 

Thickness, estimated (feet) 

3,000± 

1,60D-1,800 

1,50D-2,000 

25Q-315 

4, 000-5,000 

70D-800 

Lithology 

Medium-gray fine-grained bioclastic, highly 

fossiliferous limestone; 30D-400 ft. 

Dark-olive-gray fissile shale, interbedded fossiliferous limestone, and a little sandstone and 

conglomerate; 400± ft. 

Medium-gray limestone and siltstone, interbedded with shale and a little intraformational conglomerate ; 1, 10D-2,000 ft. 

Light-medium-gray thick-bedded cherty limestone; 1,00D-1,100 ft. 

Light-medi urn-gray thin-bedded limestone, silty 

partings; 20Q-800 ft. This formation is 

equivalent to the Pogonip Limestone of 

Hague (1883) and approximately equivalent 

to the Ordovician Pogonip Group and the 

Cambrian WindfaJI Formation (Nolan and 

others, 1956) . 

Shale and dark-gray thin-bedded highly 

fossiliferous limestone. 

Medium-dark-gray medium-thick-bedded limestone; pinches out to south; Q-250 ft. 

Medium-gray to pale-olive-gray slightly limy 

shale. 

Medium-gray fine- to medium-coarse grained 

limestone; 1 OD-300 ft. 

White to very light gray saccharoidallimestone or low-grade marble; contains thin gray 

limestone and local lenses of dolomite; 

1,200± ft. 

Medium-dark-gray fine- to medium-coarse 

grained limestone; contains a few local 

quartzite beds near base; 10Q-200 ft. 

Olive-black to greenish-gray quartzitic shale 

and siltstone; contains some interbedded 

quartzite and limestone. 

Light-gray to dark-purplish-gray thick-bedded 

crossbedded quartzite and metaquartzite; 

contains some shale near top and conglomeratic quartzite near base; locally contains some bodies of altered metadiabase; as mapped may include some rocks of Precambrian age. 

Phyllitic shale, metaquartzite, and slaty 

argillite. 

Tertiary through Quaternary time is represented by 

a sequence of continental conglomerate, lava flows, intrusive bodies, and tuffs having a combined thickness 

of more than a mile. Angular unconformities are 

numerous in the younger sequence but are poorly 

dated. The surficial deposits in the valleys are 

largely a continuation of Tertiary sedimentation. 

They are poorly consolidated, are derived from nearby 

sources, and are interbedded with fine lacustrine sediments deposited in a pluvial lake. 

The sedimentary rocks are cut by many low-angle 

faults and by many steep faults. The low-angle faults 

are largely thrust faults parallel or almost parallel 

to bedding planes, and they generally reduce the thick-
CAMBRIAN SYSTEM 7 

ness of the sequence of Paleozoic rocks, in some places 

by as much as 2.5 miles; only rarely are beds repeated 

along these faults. Because of this fact, the thicknesses given for the older formations can only be 

estimated and are commonly the minimum amounts. 

Other low-angle faults are glide faults; "glide fault" 

is a term here used to describe rootless faults that 

were formed near the surface under the direct influence of gravity. Many normal faults and some 

glide faults cut the thrust faults or are nearly parallel 

to them. Corr~plex outcrop patterns were formed near 

segments of faults along which movement has been 

recurrent and varied in direction. Movement along 

some normal faults during late Tertiary and Quaternary times caused linear physiographic features, but 

not all such features are related to faults. During the 

Tertiary when normal faulting was frequent, magmas 

ranging in composition from rhyolite to dacite were 

intruded into the older strata and were extruded as 

lava and tuff. Siliceous material that partially replaced limestone and that locally contains ores of base 

metals and silver is closely associated with the oldest 

intrusive rock. 

STRATIGRAPHY 

PRECAMBRIAN SYSTEM 

METASEDIMENTARY ROCKS 

Less than 800 feet of metasedimentary rocks of 

late Precambrian age underlies a few square miles in 

the northeastern corner of the quadrangle, and 15 

miles north of the quadrangle similar rocks form the 

upper part of the Piermont Group of Young (1960b, 

p. 158). Pending a more extensive study of the Precambrian rock in the intervening area, no formal 

names are applied to it in this quadrangle. I have 

probably assigned less rock to the Precambrian and 

more to the Cambrian than Young has done, for his 

uppermost shale unit seems to be lenticular and to 

be absent in this quadrangle, and the quartzite beds 

above and below it are lithologically similar and 

cannot be separated where the shale unit is absent. 

The lowest 500-600 feet of the Precambrian rock 

exposed in the quadrangle consists of impure quartzite, 

conglometratic quartzite, a little conglomeratic shist, 

and argillite, which are grayish brown 1 and underlie 

moderately steep slopes. The pebbles in the congomeratic rocks are moderately well rounded, are 

less than 1 inch in diameter, and consist of white quartz 

and quartzite. They are scattered or poorly sorted and 

lie in a matrix that ranges in composition from relatively pure quartz sand to silt. The quartzitic beds 

1 All colors used in this report are from Rock-Color Chart (Goddard 

and others, 1948). 

are a few inches to a few feet thick, but the schist . and 

argillite beds are thinner. 

The quartzite, schist, and argillite unit is overlain 

by about 200 feet of slaty argillite and quartzitic 

phyllite, which are generally also grayish brown, but 

which form a bench and gentle slopes above the more 

resistant quartzite, schist, and argillite. A few slaty 

beds are more colorful-dusky blue to purplish gray, 

pale bluish green, and pale yellowish orange. 

The Precambrian rock is slightly metamorphosed. 

Phyllitic foliation and slaty cleavage are conspicuous 

in many of the fine-grained rocks. The cleavage 

commonly parallels the bedding, but in some rocks 

diverges as much as 30° from bedding. Chlorite is 

abundant in the groundmass of this rock and also 

forms some larger pods, as seen in thin section. The 

grains of the quartzitic rock inter lock, and in the 

phyllitic rock biotite lies between the quartz grains. 

The metasedimentary rocks begin about 5,000 feet 

below Olenellus-bearing beds and are the youngest 

fairly thick argillaceous rocks beneath the Prospect 

Mountain Quartzite. They are considered late rather 

than early Precambrian because of their apparent conformity to overlying Paleozoic rocks and their contrast to another older sequence of moderately metamorphosed rocks in the southern end of the Deep 

Creek Range (Nelson, 1959; Bick, 1958) about 30 

miles to the northeast. 

Rocks similar to, and possibly correlative with, the 

metasedimentary sequence in the Schell Creek Range 

were named the Goshute Canyon Formation and Horse 

Canyon Formation in the Deep Creek Range (Bick, 

1959), and were the basal quartzite and the overlying 

slate or shale member of the lower part of the Prospect 

Mountain Quartzite in the Gold Hill district (Nolan, 

1935, p. 6). Correlative rocks also appear in the 

southern Snake Range (Drewes, 1954; 1958, p. 224-

225) and in the Egan Range (Fritz, 1960; Woodward, 

1962). Individual units of upper Precambrian rock 

in these four ranges cannot be definitely correlated, 

because the units apparently wedge out or change 

facies within 10-30 miles. 

CAMBRIAN SYSTEM 

PROSPECT MOUNTAIN QUARTZITE 

Quartzite, 4,000-5,000 feet thick, that lies with apparent conformity on the phyllite at the top of the 

metasedimentary Precambrian rocks, constitutes the 

Prospect Mountain Quartzite. The name was firs~ 

applied by Hague (1883, p. 253-254) near Eureka, 

Nev., and has since been widely used in Nevada and 

Utah. Hague, however, was unable to define the base 

of the formation, because only its upper 1,500 feet is 
8 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

exposed in the type locality. The lower contact of 

the Prospect Mountain was selected at six places in 

eastern Nevada and western Utah; though at each 

place the contact is marked by similar lithologic 

changes, each selection actually may represent different horizons. At each of the six places, as well 

as in the Connors Pass quadrangle, the base of the 

Prospect Mountain Quartzite is placed at the top of 

the highest mappable unit of shale, schist, or argillite 

beneath the main body of quartzite. At the base of 

the formation the change from phyllitic rock upward 

to quartzite is· either sharp or transitional over a few 

feet. The thickness assigned to the formation on this 

basis ranges from 2,000 feet in the Sheeprock Range, 

Utah (Cohenour, 1957, 1959), to at least 5,000 feet in 

the Promontory Range, Utah (Olson, 1956). This 

wide variation in thickness suggests that the argillaceous units are lenticular and that a given lens may 

be present and well exposed in one district but not in 

others. 

In the northeast part of the Connors Pass quadrangle and for several miles north of it, much of the 

middle part of the Prospect Mountain Quartzite is 

poorly exposed on a large dip slope. A thin phyllitic 

shale unit 2,000-3,000 feet beneath the top of the 

formation that appears 15 miles to the north (Young, 

1960b) is either covered or absent in this quadrangle. 

The Prospect Mountain Quartzite underlies about 

10 square miles of the quadrangle, mostly along Cleve 

Creek in the northeast corner of the area; it also crops 

out topographically low along the east flank of the 

range between Majors Place and the mouth of Cooper 

Canyon, and in Mosier Canyon in the northwest 

corner of the quadrangle. The quartzite generally 

forms extensive uniform slopes that are interrupted 

by a few castellated cliffs. Many of these slopes are 

covered by rubble fields whose fragments have conspicuous grayish-red centers and light-brownish-gray 

rims. Less typically, as north of Majors Place, the 

Prospect Mountain weathers to very light gray slopes 

that are not covered with rubble and are broken only 

by scattered small ledges. 

The Prospect Mountain consists mainly of fairly 

uniform quartzite or metaquartzite alternating with 

thin beds or partings of shale or argillite. The fresh 

quartzite is mostly very light gray to pinkish gray 

but less commonly greenish gray or dark purplish 

gray, and the interbedded shale is dark brownish 

gray to brownish black. Upon weathering, the very 

light gray to pinkish-gray quartzite does not change 

color, but the shale and argillite become pale red, 

pale yellowish brown, or brownish black. The quartzite beds are commonly 3--4 feet thick but range in 

thickness from 1 to 6 feet, and generally are crossbedded. North of Majors Place most of the foreset 

beds dip westward as they do in the Wheeler Peak 

area, 15 miles to the southeast (Drewes, 1954, p. 17), 

but in the Cleve Creek area no direction appeared to 

be dominant. 

Most grains are subangular to subrounded moderately coarse to very coarse sand -sized quartz, but 

some scattered grains are granule and pebble sized; 

a few thin beds contain abundant pebbles. The shale 

and some beds of quartzite contain biotite, chlorite, 

sericite, iron oxides, sphene, and zircon; apatite crystals are included in some grains of quartz. The quartz 

gains are slightly strained, are interlocking, but rarely are interpenetrating. The larger clastic grains are 

commonly separated by smaller secondary grains. The 

mica is mostly intergranular, but some flakes of 

sericite penetrate the secondary quartz grains. The 

mineralogy and texture of -the quartzite indicate a 

slight metamorphism, and these features will be compared with the characteristics of younger quartzites 

and sandstones. 

Such lithologic variations in the Prospect Mountain 

are both lateral and vertical. In the Cleve Creek 

area, pebbles are most common in the lower half of 

the formation and shaly beds are most common near 

its top, about 20 percent of the uppermost 300 feet 

being quartzitic shale. North of Majors Place, however, all but the uppermost few tens of feet of the 

formation consists of relatively clean very light gray 

quartzite. The degree of cementing or induration also 

is varied, and locally the prevailing rock is not a 

quartzite but a sandstone that weathers to · friable 

slightly rounded fragments. 

Altered greenish-gray diabase is scattered in some 

of the colluvium low on the south wall of Mosier 

Canyon. The local distribution of the blocks indicates 

that they have been weathered from a small body 

within the quartzite. This isolated occurrence is 

noteworthy because none of the Tertiary igneous rock 

in the area is similar to the diabase, and because similar rock was described by Morris ( 1957, p. 4) and by 

Morris and Lovering (1961, p. 15-16) from the Tintic 

Quartzite in the East Tintic Hills in central Utah and 

by Kellogg ( 1960, p. 190) from the Patterson Pass 

area in the. southern Schell Creek Range. The rock 

has a moderately coarse ophitic texture and consists 

dominantly of laths of strongly kaolinized, probably 

albitized, plagioclase and of interstitial clinopyroxene 

that has largely been altered to actinolite. It also contains small amounts of apatite and magnetite, xenocrysts of quartz, and interstitial secondary calcite, 

quartz, chlorite ( ~), and another amphibole ( ~). These 
CAMBRIAN SYSTEM 9 

occurrences of diabasic rock in the Prospect Mountain 

Quartzite suggest that magmatic activity occurred 

at widely scattered places in the region during Early 

Cambrian time, perhaps simultaneously. 

In eastern Nevada the Prospect Mountain Quartzite 

is of Early Cambrian age hut may possibly include 

Precambrian rocks near its base. In my opinion the 

entire formation should be designated Early Cambrian(~). 

The Prospect Mountain Quartzite was recognized in 

the Egan Range by Fritz ( 1960), in the Deep Creek 

Range by Nolan ( 1935) , Bick . ( 19·58) , and Nelson 

(1959), in the southern Snake Range by Drewes and 

Palmer (1957), and elsewhere in the Schell Creek 

Range by Young (1960b) and Kellogg (1960). 

The formation was deposited in a sea which seems, 

because correlative beds of quartzite to the east are 

younger, to have transgressed eastward. The type of 

sedimentation was continuous from late Precambrian 

time to Cambrian time, and vast quantities of quartz 

sand and a few pebbles were deposited under conditions that remained constant for a long time. The 

material in the thicker shaly and schistose beds may 

mark the occasional influx of mud and silt from a 

generally subsiding land during minor regressions of 

the sea, but that in the thinner shaly beds and partings 

was probably winnowed from the sand by generally 

westward flowing currents. The Prospect Mountain 

sediments apparently came from the east. The relative 

purity of the sand indicates that the source was distant, or perhaps that the sand was recycled. Upper 

Precambrian quartzite in the Wasatch Mountains may 

have been the immediate source of the quartz sand 

before it was submerged. 

PIOCHE SHALE 

The Pioche Shale conformably overlies the Prospect 

Mountain Quartzite. It is 250-315 feet thick, and is 

transitional between a thick quartzitic sequence and a 

thick carbonate sequence. It was defined by W alcdtt 

( 1908) and was redefined by Westgate and Knopf 

(1932). 

The Pioche Shale underlies a narrow belt on the 

east side of the Schell Creek Range between the mouth 

of Cooper Canyon and Majors Place, and several 

small areas along Cleve Creek; it commonly forms 

gently sloping benches on which outcrops are scarce. 

The shaly lithology of the Pioche is partly masked by 

quartzite and limestone chips weathered from resistant 

layers within the formation and from the overlying 

Pole Canyon Limestone. North of Majors Place the 

weathered shale is brownish gray and contrasts 

strongly with the almost white quartzite and gray. 

limestone, but in the Cleve Creek area the color of the 

weathered shale blends into that of the weathered 

quartzite. 

The Pioche consists mainly of silty shale but contains quartzite and limestone. Its contact with the 

Prospect Mountain Quartzite is gradational and is 

placed at the top of the uppermost thick bed of 

quartzite. In a transitional zone . extending a few tens 

of feet above this contact, there is a larger proportion 

of quartzite, but shale gradually becomes dominant 

upward. The general lithologies are described in 

order of decreasing abundance. The distribution of 

these rock types in the four stratigraphic sections (fig. 

2) shows that the thinner units are discontinuous. 

More than half the formation consists of olive-gray, 

greenish-gray, or olive-black micaceous shale or siltstone that weathers light brown to pale yellow brown. 

South of Cooper Canyon, and locally to the north, the 

shale is phyllitic and contains small clusters of meta- ' 

morphic minerals. The beds are commonly ¥! 6-¥2 

inch thick. The quartzite interbedded in the lower 

part of the Pioche resembles that of the underlying 

Prospect Mountain except that it is largely thin bedded 

and impure. The quartz grains are seen in thin section to be generally less than 0.1 mm (millimeter) in 

diameter and slightly flattened or elongate parallel to 

the bedding; these grains either interlock or are separated from one another by sericite, chlorite, and iron 

oxide. Schistose texture is common in some areas, and 

some shale also has a cleavage inclined at a moderate 

angle to the schistosity. 

In the upper half of the Pioche there are a few 

layers of yellowish-brown impure limestone 5-15 feet 

thick. Some of these contain small bioclastic lenses 

rich in small fragments of trilobites. Near the top 

of the formation there are also a few thin beds or 

lenses of gray platy limestone similar to that in the 

overlying Pole Canyon. 

Sections B and 0 of figure 2 were measured with a 

Jacob staff and hand level; the thicknesses of units in 

the other sections were estimated in the field and 

scaled from the map. 

Part of the difference in thickness of these sections 

may be due to minor faults (fig. 2) or to minor 

unmapped bedding-plane faults, but some of it may be 

due to variations in original deposition. The consequent difficulty in obtaining a complete and representative stratigraphic column persists in all the 

Paleozoic formations; some units in these formations 

show so much lateral variation that a single section of 

a unit cannot be regarded as representative for the 

whole area. 

Fossils were collected from the Pioche Shale at only 

four places and were all identified by A. R. Palmer 
10 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

A On spur 10,000 ft north 

of Majors Plac.e 

B On east wall of South Fork of Cleve Creek 

above bench mark 7393, 3000 ft north 

of Connors Pass quadrangle 

c 

Along gully joining South Fork of Cleve 

Creek from the southwest at elev 

10,280 ft, 3 miles north of Connors 

Pass quadrangle 

D 

Along north-fork of 

· Mosier Canyon 

t-------14 miles-----+k-------- 2 miles ____ __,++-------7 miles-----~ 

~ ~----',...--:-=------l 

~!--'--'--'--'---___,__, 

(/) 

LLJ 

:r: 

u 

0 

a: 

/ 

/ 

'1/ 

/" 

/ 

/ 

/ 

/ 

Prospect .. --1: ·.: ~- -: 

·.: :: :f'i: ... ·.<=: Mountain 

:L..·. ·. ·. ·.-.· .. z· .... .. '7 . . . .. Quartzite .. ·v . . "'-·· 

1-- .. .e.- ... · ·· -! 

1-J.-· ..... ·"7-1 

EXPLANATION 

Quartzite Sandstone Shale 

*2648·-CO 

Fossil locality and USGS collection number 

Phyllite Limestone 

X 

Unidentifiable fossil fragments 

Covered interval, 

probably shale 

FIGURE 2.-Stratigraphic secLions of Pioche Shale. 

(written commun., 1962). Two collections, 2657 -CO 

and 2662-CO (fig. 2), contain fragments of olenellid 

trilobites that indicate an Early Cambrian age; one 

collection also contains B onnia. Collection 3734-CO 

contains Olenellus sp. and a ptychoparoid trilobite 

referable to Orassifombra, also of Early Cambrian age. 

Collection 2648-CO contains fragments of several 

ptychoparoid trilobites without olenellid material and 

is probably of very early Middle Cambrian age. 

The Pioche Shale has been recognized over a wide 

area around the quadrangle; its lithology is generally 

the same everywhere, but the formation is probably 

slightly younge.r to the east than to the west. 

The silt and clay that formed most of the Pioche 

Shale are presumed to have been reworked from the 

underlying and adjacent quartz sands and to have been 

deposited in a shallow eastward-transgressing sea. 

POLE CANYON LIMESTONE 

The Pole Canyon Limestone, a white-to-gray saccharoidal limestone of Middle Cambrian age as much 

as 2,000 feet thick, conformably overlies the Pioche 

Shale. It was defined by Drewes and Palmer ( 1957) 

in the southern Snake Range. It is the oldest formation of the thick dominantly limestone sequence that 

was deposited in the region almost continuously from 

Middle Cambrian to Middle Ordovician time. 

The limestone underlies about 6 square miles of the 

area ; it crops out chiefly in the lower slopes along the 

east flank of the Schell Creek Range between Majors 
CAMBRIAN SYSTEM 11 

Place and Cleve Creek, but also in smaller areas near 

the Kolcheck mine and high in the wall of Mosier 

Canyon. The formation commonly forms large 

rounded bosses or low gray cliffs and benches, but in 

Mosier Canyon it forms prominent white to . medimngray cliffs. These cliffs are conspicuous more because 

of their white color thari because of their prominence; 

at a distance they can readily be distinguished from 

the higher and more uniformly gray cliffs of the 

Cambrian and Ordovician limestone above the overlying Lincoln Peak Formation. 

Although the Pole Canyon Limestone consists 

mainly of massive limestone, its lower contact is 

gradational; thin beds of limestone are intercalated in 

the uppermost few tens of feet of the underlying 

Pioche Shale, and a small amount of quartzitic shale 

is locally interbedded near the base of the Pole 

Canyon. The base of the Pole Canyon is placed at 

the bottom of the lowest thick unit of limestone, a 

position that is never ambiguous. 

None of the sections of the Pole Canyon Limestone 

is complete; in every section one or both contacts are 

faulted, generally by minor thrust faults that are 

almost parallel to bedding. The lithologic sequence 

within the formation is therefore uncertain, but along 

Cleve Creek, where the formation is thickest, it comprises a basal medium-gray unit 100-200 feet thick, a 

middle white to light-gray massive unit 400-500 feet 

thick that contains a few beds of darker lime,stone, 

and an upper medium-gray unit 100-300 feet thick. 

These three units and some of the subdivisions of the 

middle unit are locally mappable, but none seems to 

extend continuously over large areas. In the Mosier 

Canyon area, about 150 feet of limy shale resembling 

the upper half of the Pioche Shale,, but containing 

younger fossils, lies 300-400 feet above the base of the 

Pole Canyon Limestone. 

The limestone consists almost wholly of calcite, but 

some of it is dolomitic; the darker rocks contain very 

small amounts of black opaque material, which is 

probably organic, and some grains of detrital quartz . 

and secondary . sericite and limonite. The few 

quartzitic shale beds near the base of the Pole Canyon 

resemble the Pioche Shale in that sericite and chlorite 

are abundant, are alined, and penetrate through the 

quartz grains. 

Much of the limestone is massive or thick bedded 

' but the beds in the darker units are commonly only 

2-12 inches thick. Primary sedimentary features are 

scarce; for example, fine siliceous or silty laminae 

appear in some parts of the Pole Canyon but do not 

seem to be of great horizontal extent. In a few places 

there are small dark spheroidal blebs resembling remnants of GirvanelZa. Irregular to lenticular pods of 

limestone varied in color or texture may be relicts of 

sedimentary features, but they are difficult to distinguish from sheared pods of structural origin that occur 

in some places. Intense diagenetic change--or more 

likely very low grade metamorphism-has obliterated 

other sedimentary features. 

The most distinctive fe,ature of the limestone in the 

Pole Canyon is its saccharoidal texture. Much of the 

rock is coarsely crystallip.e, but the darker limestone 

is generally fine to medium grained. The calcite is 

seen in thin section to form interlocking anhedral to 

subhedral grains, some of which are alined, sheared, 

or veined by other calcite crystals that are commonly 

elongated normal to the gel}eral foliation. In the 

exposures south of Cooper Canyon, coarse-grained 

yellowish-brown dolomite makes up 1-15 percent of 

the formation. Dolomite also occurs in smaller 

amounts in some parts of the Cleve Creek area and is 

abundant north of Mosier Canyon. Some of the 

dolomite occurs in small pockets 1-2 inches across, but 

some forms lenses a few tens of feet thick and many 

tens to hundreds of feet long. One lens, which extends 

across the mouth of Cooper Canyon, is more than 100 

feet thick and more than half a mile long. Most contacts between limestone and dolomite parallel bedding 

planes, but some cut across the bedding. Some dolomite lenses enclose small angular blocks of limestone, 

and in places the contacts between limestone and dolomite are intricately embayed. The distribution of the 

dolomite shows no relation to the thrust faults, and in 

several places there are fault breccias containing 

fragments of both limestone and dolomite-these features indicating that the dolomite is older than the 

fault. 

The Pole Canyon Limestone is probably 1,500-2,000 

feet thick, but because it is everywhere faulted, its 

apparent thickness is commonly 800-1,500 feet. A 

rough estimate of thickness in a few sections has been 

made by computing from the map. Between Majors 

Place and the mouth of Cooper Canyon, the. apparent 

thickness is 1,000-1,360 feet; just north of Cooper 

Canyon it is 1,080 feet; north of the Kolcheck mine 

it is 1,200 feet; and just south of Cleve Creek, it is 

about 1,680 feet. Even this last figure, however, is 

probably somewhat less than the actual total thickness. 

Two collections of fossils were obtained from the 

Pole Canyon Limestone. A. R. Palmer (written 

commun., 1962) stated that one contained only a single 

cranidium of Alokistocare? and the other (USGS 

colin. 3404-CO) contained : 

Ptarmiganoides cf. P. poulseni Resser 

K ochaspis dispar Resser 
12 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

Alokistoeare sp. 

Pagetia sp. 

AlberteUa sp. 

Palmer further mentioned that the trilobites in 3404-

CO are all assignable to the Albertella zone. 

Palmer also stated (written commun., 1962) that 

the "presence of an Albertella zone assemblage in the 

assemblage in the Pole Canyon Limestone provides 

the first direct evidence that the lower part of the 

Pole Canyon Limestone is correlative with the upper 

part of the Pioche Shale in its type area, and * * * 

the development of relatively clean carbonate sediments that characterize the lower half of the Middle 

Cambrian series in the eastern Great Basin began 

earlier in this area than it did in areas to the south 

and east. Further north, in the Duck Creek Range, 

rocks equivalent to the Pole Canyon Limestone were 

mapped as Eldorado Limestone by Young (1960b)." 

Fossils of early Middle Cambrian age that were 

collected from near the top of the Pioche Shale help 

to bracket the age of the Pole Canyon Limestone as 

probably early and middle Cambrian ; only the earliest part of early Middle Cambrian and possibly the 

latest part of middle Cambrian time are not represented by Pole Canyon rocks. 

During Pole Canyon time, . the Connors Pass area 

lay so far from the shore of the eastward-transgressing sea that little of the clastic material derived from 

the land was carried into the area. The fairly abrupt 

transition from the underlying quartzite and shale 

to the limestone suggests that the shoreline shifted 

eastward somewhat rapidly in early Middle Cambrian time. Generally stable conditions, resulting in 

only very minor fluctuations of the shoreline, prevailed during most of Middle Cambrian time. 

LINCOLN PEAK FORMATION 

The Lincoln Peak Formation, a sequence of shaly 

rocks commonly 1,600-1,800 feet thick, overlies the 

Pole Canyon Limestone and was defined by Drewes 

and Palmer ( 1957) in the nearby southern Snake 

Range. During the time when shaly rocks were being deposited in the vicinity of Connors Pass, more 

limy rocks were being deposited in other areas, this 

contrast in deposition producing a fairly marked 

facies change through western Utah and eastern N e- · 

vada. In addition, at least the upper part of the 

formation is time transgressive to a s.mall, but measurable, extent; it is younger in the Cleve Creek area 

than in the type locality. 

The formation is exposed over more than 10 square 

miles of the quadrangle, largely along the east flank 

of the Schell Creek Range, but also on the west flank 

of Cave Mountain, and in the northwest corner of the 

quadrangle. The Lincoln Peak commonly forms gentle slopes having few outcrops, though nearly halfway 

up most of these slopes a resistant bed crops out as a 

small cliff or a row of knobs. Along U.S. Highway 

6-50-93 near Majors Place, the slopes underlain by 

the formation are moderately steep and are broken 

by scattered ledges and rocky gullies; but less than a 

mile north of the highway, they have more of their 

usual smoothness. 

In the northern part of the quadrangle, the Lincoln 

Peak Formation is divisible into two shale members 

and a middle limestone member. The limestone member thins abruptly from Grasshopper Canyon eastward to Cleve Creek, .and between Cleve Creek and 

Cooper Canyon it is present only here and there. 

On the geologic map (pl. 1) the thin edge of the 

limestone is shown schematically as a marker bed. 

The upper shale member can generally be distinguished from the lower one by its lithologic character, 

even where it is not underlain by the middle limestone member, but south of Cooper Canyon, where 

the formation is slightly metamorphosed, these lithologic distinctions, as well as diagnostic fossils, are 

obliterated. 

The Lincoln Peak Formation is conformable with 

the Pole Canyon Limestone, and in some places the 

typical rocks of the two formations are separated by 

a transitional zone a few score feet thick. The lowest 

shale beds assigned to the Lincoln Peak contain a few 

beds of limestone closely resembling that of the Pole 

Canyon. However, at most outcrops the basal contact relations are obscured by faulting. At such outcrops the beds on one or both sides of the contact are 

gradually truncated; the shearing, brecciation, minor 

folds, and crinkles commonly increase downward in 

the lowest 50 feet of the Lincoln Peak Formation; 

the contact is probably a minor thrust fault nearly 

parallel to the bedding. A fault is inferred to extend along the contact wherever beds are missing, for, 

although stratigraphy itself could account for their 

absence no evidence of an unconformity has been ' . found in any place where there is not als.o some evidence of faulting. 

The lower shale member of the Lincoln Peak Formation consists of fissile to thin platy shale, and scattered limestone beds 1-2 inches thick which make up 

less than 10 percent of its volume. Much of the 

shale is silty and limy, and some of it is micaceous. 

On fresh fractures it is medium gray to pale olive 

gray, but weathered chips are pale yell?w brown, 

pale purple, grayish orange pink, or grayish orange. 

The upper shale member is rarely as colorfuL Along 
CAMBRIAN SYSTEM 13 

many miles of its base the lowest few tens of feet of 

the lower shale member weathers to a pale-red or 

moderate-red rubble, which is probably a fault breccia inasmuch as it appears only where there are other 

signs of structural disturbance; whatever its origin, 

it is a useful marker for the base of the formation. 

The middle, limestone member of the Lincoln Peak 

Formation consists of medium-dark-gray thin platy 

limestone that contains some silty partings, Girvanella, 

fucoidal markings, and toward the top, agnostid 

tribolites. In upper Cleve Creek the limestone is bioclastic and oolitic. The calcareous beds are commonly 

¥2-4 inches thick, but the shaly interbeds are less than 

one-fourth of an inch thick. Just south of Cleve 

Creek, some of the clastic interbeds are highly siliceous 

and resemble chert. Just north of Cooper Canyon, 

the limestone member is thin, lenticular, and in places 

deformed by minor disharmonic folds and thrust 

faults. It commonly has agnostid tribolites in its 

uppermost part, but along Cooper Canyon and south 

of it, the limestone member contains no fossils. 

The upper shale member of the Lincoln Peak Formation is more fossiliferous and more varied than the 

lower shale member. The proportion of limestone 

beds gradually increases upward from about 30 to 75 

percent; most of the beds are 1-2 inches thick, but 

toward the top some are as much as 9 inches thick. 

Low in the member, most of the limestone is finely 

crystalline but some is bioclastic or even coquinoid. 

Small limy plates having moderate-brown to grayishbrown silty surfaces are common in the lower part 

of this member. The silty shale generally weathers 

to larger less colorful fragments than the lower shale 

member. Nodular beds, crinkly bedding surfaces, 

beds of trilobite hash, and other bioclastic materials 

become common as the amount of limestone increases 

upward in the member. A section of the upper few 

hundred feet of this member was measured between 

altitudes of about 9,000 and 9,940 feet on the ridge 

south of Cave Mountain (fig. 3). 

From Cooper Canyon south to Majors Place, the 

Lincoln Peak Formation is slightly metamorphosed 

to phyllitic or slaty shale. The intensity of the alteration increases gradually southward, and with one 

exception, just south of the mouth of Cooper Canyon, 

it does not change appreciably toward the contacts of 

the formation and the minor thrust faults. The first 

change in the rocks appears east of Bastian Spring, 

where rocks of the lower shale member have a pencil 

fracture and are sufficiently hard to tinkle under foot. 

A little north of Cooper Canyon the increasing hardness affects the entire formation. Just south of the 

canyon some beds about 50 feet above the base of the 

240-303 0 - 67 - 2 

Q) 

bO 

til 

c 

til 

"(j 

·::; 

0 

"C 

0 

"C 

c 

til 

c 

til 

·;::: 

.0 

E 

til 

(.) 

0 

Q) 

c 

.s 

<II 

Q) 

E 

:.::i 

c 

0 

:p 

til 

E 

0 

LL.. 

..ll:: 

til 

Q) 

Cl... 

c 

0 

(.) 

c 

:.::i 

Q) USGS FOSSIL LITHOLOGY t' B COLLECTION 

~ ~ r:-:-.-r-----r-=---..----

(.) E 

Q) 

c 

.s 

<II 

Q) 

E 

"C 

Q) 

"C 

"C 

Q) 

.0 

c 

:c 

3018. 

IQ) 

c 

.s 

<II 

Q) 

E 

"C 

Q) 

"C 

"C 

Q) 

.0 

.X 

~ 

£ 

>. 

til 

f 

.r:. 

bO 

:.::i 

3017. 

Q) 3016. c 3015. .s 

<II 3014. Q) 

E 3013. 

3012. "C 

Rocks much f.ractured, 

thicknesses .probably 

not accurate 

Q) 3011· "C h-:::r-::::I~~;;;r-'7 S ma II "C 

Q) 3010. -9 3009. >. 

.0 3008. .0 

0 3007. c 3006. ~ 

3005. 

3004. 

3003. 

3002. 

3001. 

fault(?) 

FEET 

0 

100 

FIGURE 3.-Stratigraphic section of JPcpJ} p~Pfl o Lincoln Peak 

Formation and lower part of overlying Cambrian and Ordovician limestone, measured by A. R. Palmer and Harald Drewes 

on ridge south of Cave Mountain. 
14 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

formation are phyllitic, have a weak slaty cleavage 

inclined about 30° to the bedding, and have bedding 

planes sprinkled with needles of a secondary mineral, 

probably actinolite. Quartz rubble from veins appears in areas of slightly metamorphosed rocks but is 

almost completely absent elsewhere. Near U.S. Highway 6-50-93, slaty cleavage is widespread and cleavage surfaces are spangled with fine-grained mica. 

The clastic grains range from 0.01 to 0.25 mm in 

diameter. Quartz and calcite make up most of the 

rock, but their proportions are greatly varied. The 

very slightly metamorphosed rock contains considerable sericite and some spindle- or disk-shaped larger 

crystals of calcite among smaller equidimensional 

grains. More distinctly metamorphosed rock contains 

about 5-50 percent of sericite or muscovite and a 

small amount of chlorite among the clastic grains of 

quartz, calcite, black opaque material, and limonite 

pseudomorphs after pyrite. Even in the more distinctly metamorphosed rock, however, the metamorphism dearly was of very low grade. 

Because of inadequate exposures and structural 

complications it is impossible to measure the thickness 

of the formation, and estimates (about 1,600 ft and 

not more than 1,800 ft) obtained from structure sections probably are within 10 percent of the actual 

thickness. 

The Lincoln Peak Formation is the most fossiliferous Cambrian formation in the Connors Pass quadrangle. According to A. R. Palmer (written commun., 1962), it includes beds ranging in age from 

about middle Middle Cambrian to Franconian, in the 

Late Cambrian. The Middle Cambrian part of the 

formation is less fossiliferous than the Upper Cambrian part. The trilobites are predominantly agnostids. Near the top of the Middle Cambrian part of 

the formation in the northern part of the quadrangle, 

the limesto:P.e member yielded agnostids referable to 

Lejopyge. Limestones containing Lejopyge have been 

found at a comparable stratigraphic position at the 

top of the Marjum Limestone in the House Range 60 

miles to the east, in the Lincoln Peak Formation on 

the east side of the Snake Range, and in the middle 

of the Patterson Pass Shale (Kellogg, 1960) near 

Patterson Pass in the southern Schell Creek Range. 

A few small collections from beds below the Lejopygebearing limestone contain species of Ptychagnostus, 

Hypagnostus, Peronopsi.~, and Doryagnostus, indicative of ages within the upper half of the Middle 

Cambrian. 

Palmer (written commun., 1962) commented: 

The Upper Cambrian part of the Lincoln Peak Formation is 

generally fossiliferous, and faunas of at least six different Late 

Cambrian ages have been collected from it. These faunas are 

largely undescribed, although studies of the trilobites are now 

underway. 

Fossils from the upper part of the formation indicate that 

the contact with overlying Upper Cambrian and Lower Ordovician limestone varies in age from perhaps as young as the 

Oonaspis zone, of Franconia age, to as old as the Dunderbergia 

zone, of Dresbach age. In general, the contact becomes younger 

to the north and northwest within the quadrangle. 

In the area south and east of the peak with triangulation 

marker Bastian, the top of the Lincoln Peak Formation is within 

the Dunderbergia zone and is of approximately the same age 

as it is in its type area in the Snake Range. 

In the vicinity of Cleve Creek and in the northwestern corner of the quadrangle, the top of the Lincoln Peak Formation 

is distinctly younger and the upper beds contain trilobites of 

the lower part of the Elvinia zone, of Franconia age. The top 

of the formation here i'S approximately equal to the top of the 

Dunderberg Formation in the vicinity of McGill, about 14 miles 

to the north. Apparently this quadrangle is in an area of 

striking facies changes within the early Late Cambrian. The 

massive nearly lithographic light-gray limestone of the upper 

part of the Raiff Formation of Young (1960b), which underlies 

the Dunderberg Formation at McGill, has changed to thinbedded limestone in the vicinity of Mosier Canyon, and near 

Cleve Creek and in areas south to Bastian Spring its stratigraphic position seems to be completely occupied by thin-bedded 

dark silty limestone. The silty limestones of the upper part of 

the Lincoln Peak Formation in Mosier Canyon and near Cleve 

Creek also change facies southward and are temporally equivalent to the massive limestones of the lower part of the undifferentiated limestones of Cambrian and Ordovician age in the 

vicinity of Cave Mountain. 

In mapping, the lithographic identity of the map units has 

been retained at the expense of some inconsistency in regard 

to age. 

Palmer (written commun., 1962) further said that 

his regional study of these facies changes indicated 

that the local variations "* * * result from a ·complex 

lateral shifting of the contact between a belt of generally silty sediments, represented by the Dunderberg 

Shale and Lincoln Peak Formation, and a belt of 

generally clean carbonate sediments lying to the north 

and east, in response to a significant marine regression during late Dresbach time." 

The change from a shaly facies in eastern Nevada 

to a limestone facies in western Utah, during early 

and middle Late Cambrian time, · indicates a western 

source for the Lincoln Peak Formation. But late in 

this period a tongue of clastic sediments derived from 

a landmass in eastern Utah was spread out to form a 

part of the upper shale member of the Lincoln Peak 

Formation in the Cleve Creek area (Palmer, 1960). 

METAMORPHISM OF PRECAMBRIAN AND 

CAMBRIAN ROCKS 

Rocks as young as the Late Cambrian, or perhaps 

even slightly younger, are sufficiently metamorphosed 

to be either moderately recrystallized or moderately 
METAMORPIDSM OF PREOAMBRIAN AND CAMBRlAN ROCKS 15 

sheared and contorted and to contain a small amount 

of newly constituted minerals. But not all the rocks 

older than the Middle Cambrian are metamorphosed; 

the type and intensity of the changes differ with the 

composition of the rock, as well as with general geographic distribution, and they are affected to some 

extent by the proximity of major low-angle faults. 

In outcrops the metaquartzite does not seem to 

differ significantly from other quartzite, but thin sections reveal some textural differences. In the Precambrian and Cambrian quartzites, the quartz grains 

generally interlock or even interpenetrate; these rocks 

contain comparatively few remnants of rounded quartz 

grains having overgrowths of secondary silica, and 

there are numerous flakes of muscovite or sericite 

within the quartz grains as well as between them. In 

the younger quartzite, however, some of the grains 

interlock but do not interpenetrate; there are also 

many remnants of rounded quartz grains, and the 

grains enclpse little or no sericite. 

Phyllitic or slaty rock occurs in all the Precambrian 

rocks; there is some in all the Cambrian Pioche Shale, 

and it is abundant in some of the Cambrian Lincoln 

Peak Formation. The Precambrian rocks include 

slaty shale, in which the cleavage is inclined as much 

as 30° to the bedding, and phy llitic metaquartzite. 

Although not widely exposed within the quadrangle, 

the Precambrian metamorphic rocks appear outside 

the quadrangle in the northern part of the Schell 

Creek Range (Young, 1960b), where no low-angle 

faults have been recognized. 

The Pioche Shale also contains much metaquartzitic 

shale, a little phyllitic shale, and some highly micaceous shale; these different types of shale are perhaps examples of Dapples' (1962) phyllomorphic 

stage of diagenesis, which overlaps the zeolite and 

chlorite grades of metamorphism. The Lincoln Peak 

Formation consists of shale to the north and west 

of Bastian Creek; to the south it changes gradually 

along the strike but generally does not change across 

the strike. Along Bastian Creek the shale is so indurated as to tinkle underfoot, and it has a wellformed pencil fracture. South of Cleve Creek all 

fossils and many sedimentary features are obliterated; 

here the rock is very hard, has a weak slaty cleavage, 

and contains many small quartz veins. Near Majors 

Place these rocks are plica ted, have a moderately well 

formed slaty cleavage and a dull phyllitic luster, and 

contain some chlorite. 

The distribution of the weakly metamorphosed rocks 

in the Lincoln Peak Formation is largely independent 

of any main low-angle fault. Near Majors Place the 

formation lies close beneath the largest low-angle 

fault in the quadrangle, but along Bastian Creek it 

is several miles from the trace of the fault, and presumably far beneath a projection of the fault. At the 

head of Cave Creek and northwest of ·Grasshopper 

Canyon, however, where the formation is exposed 

close to the fault, it is unmetamorphosed, even though 

the thin sheet of limestone overlying it is sheared and 

slightly recrystallized as it is everywhere along the 

fault. 

The Pole Canyon Limestone consists chiefly of 

saccharoidal limestone or low-grade marble, in which 

the calcite grains are completely and coarsely recrystallized, all sedimentary details are obliterated, and 

muscovite or sericite, where present, is intergrown 

with the calcite grains as well as molded around them. 

Mortar texture or granoblastic texture and shear 

planes are present on a microscopic scale even at some 

distance from the major fault. The wide extent of 

this metamorphism of one formation might suggest 

that the metamorphism was due to stresses along an 

unrecognized fault within that formation, but this 

explanation is not favored, because the Pole Canyon 

Limestone and the adjacent formations are far less 

deformed into tectonic lenses than are the formations 

along the largest recognized thrust fault and because 

the Pole Canyon contains no relict drag features. 

The origin of the metamorphism is difficult to explain, because inferences drawn from field relations 

require a broader regional base than is now available, 

and those drawn from microscopic relations require a 

more systematic study of the physical properties of 

the rocks than it has been possible to make. At present I believe that some of the metamorphic features 

are the result of a mild dynamic deformation, caused 

by movement along the nearby major low-angle faults. 

Similar views have been expressed and more adequately supported by Misch and Hazzard (1962). 

However, the occurrence of metamorphic features far 

from the major low-angle fault and the varia.tions in 

the intensity and the extent of metamorphism along 

that fault probably indicate that much of the metamorphism was due to causes independent of this dynamic deformation. Contact metamorphism above a 

hypothetical buried stock might explain the association 

of quartz veins with the more intensely altered rock, 

but inasmuch as none of the exposed stocks of 

the region has a wide aureole, such a hypothesis fails 

to explain the widespread mild alteration. This wide 

alteration most likely was a static metamorphism 

produced by the tremendous load of overlying sed~­

ments, about 6.5 miles thick during Late J urass1c 

or Early Cretaceous time. This static metamorphism may have been reinforced by some poorly 
16 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

understood mechanism involving diffuse and irregular movements of pore fluids under high hydro- . 

static pressure, a condition possibly critical in the 

structural development of the area. 

The static metamorphism presumably was in progress during middle Mesozoic time, when the rocks 

that were metamorphosed were most deeply buried 

(see p. 77). This process may have begun at an earlier time, when a threshold of depth of burial, of 

unknown amount, was reached, and it is even more 

likely that the process continued until another threshold of depth of burial, of unknown amount, was passed 

as the rocks were exhumed. Throughout the region, 

the time and rate at which the rocks were exhumed is 

poorly known, but very likely exhumation began with 

the Late Jurassic or Cretaceous epeirogenic uplift 

that is indicated by the withdrawal of the sea. The 

rate of exhumation may have been greatest during 

the middle Tertiary time of block faulting; thus it is 

unlikely that metamorphism continued any later. 

Armstrong ( 1963) presented a dozen radiogenic age 

determinations that placed the end of the metamorphism as late as Miocene. 

At least some shearing, a common feature of the 

dynamically metamorphosed rocks close to the Schell 

Creek Range thrust fault, has been superposed on 

some of the static metamorphism. 

CAMBRIAN AND ORDOVICIAN SYSTEMS 

LIMESTONE 

A sequence of limestone, about 3,000 feet thick, 

overlies the Lincoln Peak Formation. Hague ( 1883, 

p. 260) named this sequence the Pogonip Limestone, 

after Pogonip Ridge near Hamilton, Nev., and believed it to be Lower Ordovician and possibly Upper 

Cambrian. Since then these rocks have been extensively studied in Nevada and Utah, and sections have 

been described at Ibex, Utah, by Hintze (1951a, b) 

and near Eureka, Nev., by Nolan, Merriam, and Williams (1956). As a result, the stratigraphy of the 

Cambrian and Ordovician rock has been revised in 

many places. The limestone that is mainly Ordovician 

age has been raised to the rank of a group, and the 

Upper Cambrian limestone has been made a separate 

formation. 

In the Connors Pass quadrangle, about midway 

between the areas studied by Hintze (1951a, b) and 

by Nolan, Merriam, and Williams ( 1956), lithologic 

variations are more subtle than at Eureka, and fossils 

are less numerous than at Ibex. Consequently, the 

Pogonip Limestone of Hague in the Connors Pass 

quadrangle is difficult to divide and to correlate with 

the Eureka and Ibex sections; it is also impractical to 

separate the limestone of Ordovician age from that of 

Cambrian age. As structural complexities add to the 

difficulties, not only in this quadrangle but throughout 

much of e·astern Nevada and perhaps elsewhere, the 

usefulness of the Eureka and Ibex sections may be 

restricted to the vicinity of those sections. These rocks 

are called simply Cambrian and Ordovician limestone 

in this report, although they are equivalent to the 

eminently practical unit, the Pogonip Limestone of 

Hague. The formation is divided informally into a 

lower limestone, a. shale member, and an upper limestone; where the shale member is not mapped, the 

limestone members may not always have been 

differentiated. 

The stratigraphic thickness of the Cambrian and 

Ordovician limestone in this area is estimated to be 

about 3,000 feet; however, in no one place is there 

more than about 2,000 feet of strata between the 

bounding contacts because, although the formation as 

a whole generally is a nearly flat-lying sheet, its beds 

are generally inclined at moderate angles and are 

broken by high-angle faults. Inasmuch as many of 

these faults remain unmapped because of poor stratigraphic control, estimates of the overall thickness from 

structural sections are unreliable, and the thicknesses 

assigned to the constituent units are based on very 

rough estimates. 

The undifferentiated Cambrian and Ordovician limestone underlies a broad area near the center of the 

quadrangle and smaller areas in all parts of the 

quadrangle except the southwest corner. The rocks in , 

the lower few hundred feet . form small ridges and 

spurs. The middle part is exposed in high, steep 

light-gray cliffs. The upper part generally forms low 

cliffs that alternate with discontinuous benches. 

The lower limestone is divisible into thre~ unmapped 

units : a basal ledgy limestone, a cliff-forming limestone, and a silty limestone. The basal contact of the 

Cambrian and Ordovician limestone is vertically 

gradational and js laterally time-transgressive. In 

most places the base is placed at the base of the lowest 

small eliff of moderately thick bedded limestone, containing thin silty partings, that overlies the shalier 

rocks of the Lincoln Peak Formation. In the Cooper 

Canyon area, however, and southward toward Majors 

Place, where most of thjs limestone is cut out by an 

overlying fault that is almost parallel to the bedding 

planes and where the underlying Lincoln Peak ~ormation is slightly metamorphosed, the lowest cliffforming unit is older and seems to be several hundred 

feet lower stratigraphically than it is to the north. 

In some places the lateral changes are entirely stratigraphic and involve minor lithologic differences-in 
CAMBRIAN AND ORDOVICIAN SYSTEMS 17 

the proportions of silt to carbonate for exampleelsewhere they are partly or wholly structural, or are 

metamorphic. Some apparent differences are only differences in weathering habit. Minor bedding-plane 

faults have occurred at or near the basal contact in 

many places, probably because this contact separates 

incompetent rocks above from competent ones below. 

In some places, such as the Kolcheck Basin, where the 

contact is not broadly gradational, the stratigraphic 

section may be slightly telescoped along a minor 

bedding-plane fault. In other places, such as northwest of Bastian Spring, weak thin-bedded rock has 

been brecciated and then thoroughly healed, either 

with or without the addition of calcite cement. The 

cemented breccia, is relatively resistant to erosion, 

owing to its alteration, and forms cliffs. 

Because of these complications in structure, it is well 

to apply other criteria for determination of the contact; one useful criterion is the distribution of chert. 

The Cambrian and Ordovician limestone is generally 

cherty, whereas the Lincoln Peak Formation is not, 

except east of Cottonwood Spring where chertlike pods 

are in the centers of small siliceous siltstone lenses, in 

a group of ledge-forming limestone beds many hundreds of feet below the top of the Lincoln Peak. However, in most places the lowest chert is in the basal 

ledgy unit of the lower limestone, or roughly within 

the lowest 300 feet of the Cambrian and Ordovician 

limestone and is possibly equivalent to the Windfall 

Formation; in a few places the lowest chert does not 

appear below the base of the cliff-forming limestone 

that lies above the basalledgy unit. 

The basal ledgy limestone unit is commonly 200-300 

feet thick, but in some places it is as much as 800 feet 

thick. It is light-gray to medium dark-gray thinbedded shaly limestone to a platy limestone containing 

pale-yellowish-brown, pinkish-gray, and pale-reddishbrown silty partings not constituting more than 15 

percent of the rock. Most of the beds are only a few 

inches thick, but some are as much as 4 feet thick. 

Crinkly and knobby bedding characterize much of the 

unit, and in many places nodular beds appear near the 

top. The texture of the limestone ranges from very 

fine to eoarsely crystalline or bioclastic. Highly fossiliferous beds are common, and some beds contain 

abundant small spherical bodies that resemble Girvanella. Chert forms small dark-gray irregular nodules 

and pods and a few long lenses. A few irregular 

nodules of chert cut across the bedding. Generally 

where the unit is relatively thick a little fissile olivegray shale is interbedded with nodular limestone near 

the top. South of Cave Mountain, where the basal 

ledgy limestone unit (fig. 3) is thickest, it is divisible 

into four parts, in ascending order: a dark-gray 

knobby-bedded limestone, a light-gray thick-bedded 

limestone forming small cliffs, a thin-bedded limestone, 

and a cherty limestone. South of Cooper Canyon 

these rocks are slightly recrystallized, and much sedimentary detail and many fossils are obliterated. Here, 

too, each of the four parts of the sequence becomes 

thinner, perhaps ber..ause it has been partly cut out by 

faults or thinned by pressure. 

The cliff-forming limestone unit is about 1,000-

1,100 feet thick, contains relatively little silt and 

clay, and is thick bedded. It is medium gray and 

fine to medium-coarse grained. The rock does not 

part readily on bedding planes; therefore it breaks 

down into more massive blocks than it would if the 

bedding were more generally marked by silty layers. 

Chert nodules are generally present in small amounts, 

and high in the unit there are several zones, each a 

few tens of feet thick, containing as much as 20 percent thin-bedded lenticular chert. 

The silty limestone unit, roughly estimated to be 

1,100-2,000 feet thick, caps the flat-topped ridges at 

triangulation marker Bastian and between upper Steptoe Creek and Cleve Creek. It consists of thin layers 

of cliff-forming or ledgy limestone that alternate with 

weaker, more largely detrital, rocks. This limestone 

resembles that in the lower units; it is a medium-gray 

fine-grained to coarsely crystalline bioclastic moderately thick bedded rock having silty partings and 

some chert nodules. Intraformational conglomerate, 

which is common, in places contains conspicuously 

flat limestone pebbles several inches in diameter. The 

detrital rock also includes much limy siltstone and 

shale and some coquina. Some of the shale is very 

fissile and weathers olive gray; other shale and siltstone weather reddish gray. The more detrital clastic 

rock beds seem to form lenses a few tens to a few 

hundred feet thick, but inasmuch as bedding-plane 

thrust faults are common here, the lenses may have 

been formed by the shearing out of extensive layers. 

SHALE MEMBER 

The silty limestone is overlain by a shale member 

about 400 feet thick. An accessible and thick section 

of the shale member is exposed on the north slope of 

a large unnamed canyon 2 miles east-northeast of 

Cave Creek Reservior. This member consists chiefly 

of a dark-olive-gray highly fissile clayey shale, but 

it also contains thin beds of siltstone, muddy sandstone, flat-pebble limestone conglomerate, and bioclastic and coquinoid limestone. Small bodies of these 

rocks may be difficult to distinguish from the clastic 

material interbedded with the underlying silty limestone unit, but they generally contain a larger pro-
18 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

portion of fissile shale and a distinctive fauna consisting of ostracodes, gastropods, and sponges. 

A limestone 300-400 feet thick is the highest unit 

of the Cambrian and Ordovician limestone. It is 

moderately well exposed above the shale member in 

the section northeast of the Cave Creek Reservoir, 

but in some places it is not present above the shale, 

probably because it is faulted out. The limestone is 

medium gray on fresh fractures but weathers light 

gray, is finely crystalline to coarsely crystalline and 

in part bioclastic, contains a little intraformational 

conglomerate, and near the top includes some siltstone and sandstone. The limestone beds are 2-10 

inches thick, and their bedding surfaces are slightly 

knobby. Chert occurs in small amounts as nodules 

and rarely as tubular bodies that may have replaced 

fossils. The upper limestone thus resembles much 

of the lower limestone from which it can be distinguished only by its stratigraphic position and by its 

fauna, which includes abundant ostracodes, gastropods, and brachiopods. 

FAUNA, AGE, AND CORRELATION 

Much of the Cambrian and Ordovician limestone 

is moderately fossiliferous, but the basal ledgy limestone unit of the lower limestone and the shale member 

are highly fossiliferous, and the cliff-forming limestone unit of the lower limestone is only sparsely 

fossiliferous. Of the Ordovician fossils in table 2, 

the gastropods were identified by E. L. Y ochelsen 

(written commun., 1960) and all others by R. J. 

Ross, Jr. (written commun., 1959, 1960); Cambrian 

fossils not in the table were identified by A. R. 

Palmer. 

A. R. Palmer (written commun., 1962) had the 

following to say about the Cambrian fossils: 

Locally, in the vicinity of triangulation marker Bastian [Cave 

Mountain], a rubbly zone in the lower part · of this sequence 

[the base of the thin-bedded limestone unit of fig. 3 of present 

paper] yields trilobites of the EZ'Vinia zone and probably corre--

lates with the Corset Spring Shale of the Snake Range. The 

sequence of massive carbonate rocks between this and the Lincoln Peak Formation thus correlates with the Johns Wash 

Limestone of the Snake Range. In the northern part of the 

quadrangle, a cherty unit correlative with the Catlin Member 

of the Windfall Formation characteristically yields trilobites 

probably representing the Ocm.aspis zone, of Franconia age, 

which weather out on the surfaces of thin-bedded dark-gray 

fine--grained limestones. This unit is usually separated from 

the underlying beds of the Lincoln Peak Formation by noncherty 

limestones correlative with the Barton Canyon Limestone Member of Young (1960b), in the Windfall Formation near McGill. 

No fossiliferous younger Cambrian rocks were found within the 

quadrangle, but a collection of Trempealeau-age trilobites about 

4 miles north of the quadrangle indicates their probable presence also within the area described in this report. 

Ross also identified a trilobite from the cliffy limestone unit as Eurekia sp. and regarded it as probably 

correlative with forms found in the basal part of the 

Goodwin Limestone in ·the Eureka district. 

The Ordovician fossils are listed in table 2. 

The fossils thus indicate that the basal ledgy limestone unit and most or all of the cliff-forming limestone unit are of Late Cambrian age. The silty 

limestone unit, however, is mainly Early Ordovician 

but may include a few beds of Middle Ordovician 

near the top; the shale member and the upper limestone are Middle Ordovician. 

The sedimentation pattern for the Cambrian and 

Ordovician limestone in the region resembles the 

pattern of the earlier Cambrian rocks in that fine 

clastics alternated with limestone. During the middle 

Early Ordovician, approximately represented by 

zones D-I of Ross ( 1951) and of Hintze ( 1951a, b, 

1952), a sheet of silt and clay containing much calcite 

was deposited in eastern Nevada. During late Early 

Ordovician time, a similar sheet, the Ninemile Formaton, was· deposited in central Nevada, but this too 

contained considerable calcite as far east as the Egan 

Range, as shown in the sections of Kellogg (1960) and 

Fritz ( 1960). Together these deposits are equivalent 

to the silty limestone unit of the lower limestone of 

the Cambrian and Ordovician limestone in the Connors Pass quadrangle. Inasmuch as clastic material 

was largely absent in western Utah while the Ninemile Formation was being deposited, the clastic material may have been derived from the west. Strong 

currents were moving over the sea floor during late 

Early Ordovician time, for intraformational conglomerate is common throughout the region. During 

part of early Middle Ordovician time, sediment rich 

in silt and clay was deposited to form the shale member, which is correlative with the Kanosh Shale of 

Hintze (1951a) about 25 miles to the east. West of 

the Egan Range this member becomes more limy, and 

at Eureka, about 65 miles to the west, silt and clay 

were not deposited at this horizon. The shale member 

was probably derived from the south or east, as the 

Corset Spring Shale, of Late Cambrian age, is inferred to have been. 

ORDOVICIAN SYSTEM 

EUREKA QUARTZITE 

Eureka Quartzite, a nearly white quartzite 300-400 

feet thick, overlies the Cambrian and Ordovician limestone. It was named by Hague ( 1883, p. 262) for its 

exposures near Eureka, Nev. Since then the form&-

tion has been studied by Kirk (1933), Hintze (1951a, 

b), Webb ( 1956), and Nolan, Merriam, and Williams 
ORDOVJlCIAN SYSTEM 19 

TABLE 2.-0rdovician fauna from unnamed limestone 

[Zones are lettered in ascending order according to the system of Hintze (1\J51a, b; 1952). Identified by R. J. Ross, Jr. (written commun., 1959, 1960), and E. L. Yochelson (written commun., 1960)] 

Unit_ ___________ _________ ____ _____ _________ __ _ Silty limestone unit of the lower limestone Shale member Upper limestone 

Faunal zone__________________________________ A? B-A G2 J J-H M M N-M M Nor N? . N? N 0 or 0 J-H L? M-K M? M 

----------·-- ------------------------ ~ :15 ~ :g ~ ..... ~ 0 ;:'! ;::!: ..... 0> r:- ~ ""' ,., ~ C':) ;:5 ;:!;; C':) 

~ 00 :g ;:5 ..... ;:!;; s ~ C':) ""' i3 C':) i3 C':) Field No. _____________________________________ A A A A A A A A A s A A ""'A i3 A 

:15 :15 0 0> 0 0 0 ~ :15 0 0> 00 :15 00 00 0 0 0 ,., ,., ""' ,., ,., ,., ,., ""' >Q "' "' 00 ,., ,., ----·-----------·------ ------------------------------------------

U.S. Geol. Survey loc. __ ___________ ______ ___ _ 

--·--------------------------------------------------------- Brachiopods: Anomalorthis cf. A. utahensis Ulrich and 

~:~~ti;!;f~s:~-~-========================= Orthambonites michaelis Clark _____________ ====== 

------ ====== ------ ====== ------ ==~=?== ------ ====== ------ ====== ------ ====== ------ -

====== ----- ====== 

------ ====== ------ ~~~~~ X ------

~~~~~ ~~~~~ ------ ------==~== ------~~~~?~~ ------~~~~~ ------====== ------====== ~~~~~ ------ Orthambonites sp ______________ ____________ ------ ------------ ------ ------ ------------ X ------ ------ ------ X X X X ------ X? ------ X Orthoid brachiopod ______________________ ------------------------------------------------------------------------------------------------------ X 

Gastropods: Eotomaria sp ______________ --------------------- ------ ------ ------ ------ ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ X ------ ------ Moderately high spired pleurotomaria- cean ____________ __ ______________________ ------ ------ ------------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ X 

~!~~r;:~~J:dt~~~r~i>-a<i=============== ====== ====== ====== ====== ====== ====== ====== ====== --~-- ====== ====== ====== ====== ====== --~-- --~-- ~ --~-- ------ 1-Iormotoma? SP--------------------------- ------ ------ ------ ------ ------ ------ ------ ------ ------ X ------ ------ ------ ------ ------ ------ ------ ------ ------

Ostracodes: 

t~~i~~~Pe~r:i~~~~~~-~==================== ====== ====== ====== ====== ====== ====== ====== ====== ====== ~~~~~ --~-- ====== ====== ~~~?~~ ====== ~~~~~ ~~~!~~ ====== --~-- ~~~~~~~~:J~!re~_s_t:~_c_~~~~================ ====== ====== ====== === === ====== ====== ====== ====== ====== ====== ====== --X-- --X-- --x.--r- --X-- ====== --~-- --~-? __ ====== 

Trilobites: 

ilf~E~:~lliiifB:Iffirf~:l::j~~jj -_ -:~:j- -j:-~j :~ -_- ~jj:: -~-~:~ -=~--: -::~: -::~: ~j=~:- ::~:: :f,: ~j~:j= =~j~~ ~:_::: :~~ : --~;~ -:~~~ ~~~~- Hystricurus cf. M. millardensis Hintze_____ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Illaenus cf. I. utahensis Hintze ___ ________ _ ------------ ______ ------ ______ ____ ______ __ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ X 

~~~~~~;fcf~~et:%~~~~1Jso(~iii.tze)~===== ====== ====== ====== ====== ====== ==~=== ====== --~-- ====== ====== ====== ---x-- ====== ====== ====== ====== ====== ====== ====== 

~~~~~~:?s~P:-============================= ====== ====== ====== --~-?-- ====== ====== ===== ~ ====== ====== ====== ====== ====== ====== ====== ====== ====== ---x-- ====== ====== Hintzeia cf. H. celsaora (Ross) ____________ ------------ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Paranileus? sp _________ _______ ____ ____ ____ ------------ ------ ------ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Pseudomera cf. P. insolita Poulsen ________ ------------------------------------ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Pseudomera? sp _________________________________ ------ ______ __ ____ X ____________ ------ ------ X ------ ------ ------ ------ ------ ------ X ------ ------ Pseudoolenoides acicaudus Hintze ______ ______ _______________ ________ _____ _____ ________________________ ------------------------------------------------ X 

Pseudoolenoides dilectus Hintze ____________ ------ ------ ------ ------------ ------ ------ ------ ------ ------ X X ------ ------ ------ ------ ------ ------ Simphysurina cleora (Walcott) __________ __ ------ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Simphysurina cf. S. cleora (Walcott)_______ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Trigonocerca sp ___________________________ ------ ------ ------ ------ X -- - ------- ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Huge p!iomcrid trilobite __________________ ------ ------ ------ ------ ------ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------

Others: 

_g~A~~~~~:~p~~~~~~~~------:================ ====== ====== ====== ====== ====== ====== === === ====== ---x-- --~-- ====== ====== --~-- ====== ====== --~-- --~-- ====== ====== Receptaculitea? sp _________________________ __________________ ------ ______ ______ X ------ ------ ------ ------ ------ ------ ------ X ------ ------ ------ ------

( 1956) . It differs from the Prospect Mountain 

Quartzite in being much thinner and of lighter color. 

Its upper contact is easily recognized where exposed, 

because it underlies the darkest dolomite in the section. 

The Eureka Quartzite forms lenses commonly less 

than 1,000 feet long, most of which are high on the 

flanks of the ridge between Cave Creek and Cleve 

Creek. The most accessible exposure of a thick lens 

of the quartzite is about 2 miles east-northeast of Cave 

Creek Reservoir, along the bottom of the large canyon 

that is tributary to Cave Creek from the north. The 

upper contact is well exposed there, but the basal 

contact is covered, as it is elsewhere, with quartzite 

debris. 

The Eureka Quartzite commonly forms small cliffs 

that disintegrate into large rounded boulders (fig. 4). 

At some places on the east flank of the Schell Creek 

Range, the quartzite weathers to small blocky debris 

and forms slopes as gentle as those of adjacent formations. Some of the Eureka in small fault blocks 

resembles the intensely silicified but nonelastic rock 

that is common along some faults. Both types of rock 

are believed to occur along the north slopes of Cooper 

Canyon, where the Eureka Quartzite is white or pinkish gray and the silicified rock, perhaps originally a 
20 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

FIGURE 4.~Typical outcrop of white Eureka Quartzite (Oe), a 

mile east of Cave Creek Reservoir. Note the large subrounded 

weathered blocks in the canyon bottom. The dark slope 

above the quartzite is underlain by Fish Haven Dolomite (Of), 

and the light-gray outcrops farther uphill and above the dark 

slope to the left are Laketown Dolomite (SI). 

limestone, is brownish gray. The light-colored blocks 

of siliceous rock are associated here with other fault 

blocks of formations adjacent to the Eureka Quartzite, 

another indication that the light-colored blocks are the 

Eureka Quartzite. 

The quartzite is a very light gray to pinkish-gray 

rock in which most beds are 1-10 feet thick, though 

some beds are thicker. Some beds are finely laminated and others are crossbedded. Much of the quartzite has been shattered or brecciated and then cemented with quartz, this process making an extremely 

tenacious rock. The quartzite locally contains many 

small (~- to 1%-inch diameter) subspherical pockets 

filled with pale-yellowish-brown sandy or dolomitic 

material, and a very small amount of the rock is 

sandstone rather than quartzite. 

The quartzite consists almost entirely of unstrained 

quartz grains that are mostly 0.05--0.7 mm in diameter 

but rarely are as much as 5 mm. Some of the quartzite contains a very Sl!lall amount of sericite and black 

opaque material between the quartz grains. The 

quartz grains themselves also enclose very small 

amounts of apatite, biotite, zircon, iron oxide, and 

minerals tentatively identified as tourmaline and rutile. 

The grains are subrounded to subangular and are 

alined, probably parallel to the bedding. Some grains 

are only moderately closely packed and are cemented 

by later optically continuous quartz, but the boundaries of more closely packed grains interpenetrate or 

interlock. The sandy and vuggy varieties of the rock 

contain some carbonate cement, probably dolomite. 

The thickness of the Eureka Quartzite cannot be 

measured in the Connors Pass quadrangle, and it is 

difficult to estimate because the formation is persistently faulted. Even where faults are not obvious, the 

range of thickness of the formation is great, this diversity implying either faulting or unconformity or 

both. Faulting would seem to be the main cause of 

the varied thickness, for elsewhere in the region where 

an unconformity does overlie the quartzite, the Eureka 

is not as lenticular as it is in Connors Pass quadrangle; 

nevertheless, several apparently unfaulted quartzite 

lenses within the quadrangle, including the one east 

of Cave Creek Reservoir, are only 100-200 feet thick. 

About llh miles northeast of Aspen Spring, just north 

of the quadrangle, the quartzite is 300--400 feet thick; 

well-exposed sections nearby indicate that this may be 

its complete thickness. 

No fossils have been found in the Eureka Quartzite. 

The formation is underlain, however, by rocks that 

contain a lo·wer Middle Ordovician fauna and is overlain by rocks that contain an Upper Ordovician fauna. 

The quartzite is therefore assumed to be of Middle 

Ordovician age, although it may include some rocks 

of early Late Ordovician age. 

The Eureka Quartzite occurs throughout the Schell 

Creek Range and adjacent ranges and apparently varies little in appearance and only slightly in thickness. 

Ross ( 1964, p. 1551) suggested that the Eureka Quartzite may have been derived from the Uinta Arch to 

the east or, less likely, from the north. 

FI'SH HAVEN DOLOMITE 

The Fish Haven Dolomite, a very dark brown dolomite 400-500 feet thick, overlies the Eureka Quartzite 

with apparent conformity. This rock is the darkest of 

the Paleozoic sequence, and, because it overlies the 

nearly white Eureka Quartzite,, it is easy to identify 

even at a distance. I apply a nomenclature from sections in faraway northeastern Utah, rather than from 

nearby Eureka, Nev., to the rocks of Late Ordovician 

and Silurian age because lithologies and thicknesses 

change more markedly toward Eureka than they do 

to the northeast. The formation was named the Fish 

Haven Dolomite by Richardson (1913) for its exposures near the to~n of Fish Haven in northeasternmost Utah. 

The Fish Haven Dolomite is found only in the 

north-central part of the Connors Pass quadrangle, 

where it is exposed along a discontinuous narrow belt 

high on both flanks of the ridge between Cleve Creek 

and Cave Creek and forms scattered small bodies along 

a fault zone low on the west flank of that ridge from 

near the center of the quadrangle to the north edge 

of the quadrangle. 
• 

SiLURIAN SYSTEM 21 

Few sections of this formation are both well exposed and apparently complete. On much of the east 

flank of the ridge just mentioned the dolomite forms a 

dip slope that, though steep, contains few outcrops. 

Near the Kolcheck mine the dolomite lies successively 

upon the Eureka Quartzite, upon the upper limestone, 

and upon the · shale member of the Cambrian and 

Ordovician limestone. The contacts of the dolomite 

mass are there nearly horizontal, but the bedding 

within it dips steeply. This structural discordance 

indicates that the basal contact of the dolomite is a 

low-angle fault rather than an unconformity, and because this relation prevails over an extensive area, the 

dolomite is probably much broken by unrecognized 

faults. Low on the west flank of the ridge, however, 

and in the canyon that joins Cave Creek from the 

north, a;bout three-quarters of a mile east of Cave 

Creek Reservoir, the Fish Haven Dolomite is moderately well exposed and is not obviously faulted. 

Where the Fish Haven Dolomite overlies the Eureka 

Quartzite, its lower part commonly forms a bench and 

gentle slopes. The upper part of the Fish Haven 

forms steeper slopes that are broken in places by low 

cliffs, and it invariably weathers to small blocky rubble, which thinly covers much of the gentle slopes 

formed by the lower part of the dolomite. 

Most of the Fish Haven Dolomite is very dark 

brownish gray to dark gray, but toward the top the 

dark beds alternate with light-gray dolomite, which 

increases in abundance upward. The thickness of beds 

in the formation averages about 1-2 feet but is as 

much as 5 feet in some places. Some beds contain 

fine laminae that are commonly much fainter than 

those in the younger Simonson Dolomite. The faint 

laminae near the top of the thick dolomite bed and 

left of the tree in figure 5 may be compared with the 

aJbundant conspicuous laminae shown in figure 8. Minute fraotures are abundant ·and are ·at least ·as closely 

spaced as bedding planes. The dolomite is coarsely 

crystalline and has few primary sedimentary features. 

Chert makes up less than 5 percent of the rock; it 

forms scattered light-gray to dark-gray roughly ellipsoidal nodules a few inches long. Quartz grains like 

those in the underlying quartzite occur only near the 

bottom of the formation. The dark dolomite has a 

strong fetid odor when broken. 

The Fish Haven is 300-400 feet thick in the canyon 

east of Cave Creek Reservoir, where it does not seem 

to be faulted. In several other places it seems to be 

500-700 feet thick, but inasmuch as these places are 

near severely faulted rocks little reliance can be placed 

on the larger estimates. 

FIGURE 5.-Typical bed of Fish Haven Dolomite east of upper 

Steptoe Creek, 1.5 miles south of the north border of the 

quadrangle. 

The Fish Haven Dolomite contains a few poorly 

preserved fragments of corals, gastropods, and brachiopods that are replaced by coarsely crystalline lightcolored dolomite or by quartz. The chain coral 

0 atenipora sp. was identified in two collections by 

W. A. Oliver, Jr. (written commun., 1960), who dated 

them as probable Late Ordovician in age although a 

similar coral appears in the Silurian. This chain coral 

is probably the H alysites sp. of many other reports on 

the formation. J. T. Dutro, Jr. (written commun., 

1961), also identified a single brachial valve of a 

Plaesiomys that is probably related to Plaesiom!!JS 

subquadrata (Hall), a widespread species of Late 

Ordovician age. In other areas the formation is more 

adequately dated as Late Ordovician, and specifically 

as Richmond. 

SILURIAN SYSTEM 

LAKETOWN DOLOMITE 

The Laketown Dolomite, a light-gray coarse-grained 

dolomite 600--700 feet thick, conformably overlies the 

Fish Haven Dolomite. It was named by Richardson 

(1913) for exposures near Laketown in northeastern 

Utah. 

The Laketown Dolomite underlies small areas in 

the north half of the quadrangle; some of these areas 

are on or near the crest of the range, others are scattered along the fault zone at the foot of the west 

flank of the range between Cave Creek and the north 

edge of the quadrangle, and several are in Cooper 

Canyon. The formation is relatively accessible and is 

well exposed high above the dry falls on the Eureka 

Quartzite in the large canyon that joins Cave Creek 

from the north, about three-quarters of a mile east of 

Cave Creek Reservoir, and also along a gully on the 
22 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

steep northwest-facing slope just west of the Kolcheck 

mine. 

The formation has few outstanding characteristics 

that are noticeable at a distance. Its base forms the 

upper parts of the small cliffs that begin near the top 

of the Fish Haven Dolomite. On steep slopes, most of 

the formation is exposed in discontinuous cliffs where 

its bedding is only. faintly visible. 

Where the Laketown Dolomite is best exposed, its 

base intergrades with the underlying Fish Haven 

Dolomite, in which the spacing and thickness of the 

beds of dark dolomite gradually diminish upward 

toward the contact. The base of the Laketown Dolomite is arbitrarily placed at the top of a brown bed 

above which dark colors are subordinate to light colors, 

but this horizon does not anywhere form a reliable 

time-stratigraphic boundary. 

The Laketown Dolomite is largely light gray to 

yellowish gray or very pale orange on both fresh and 

weathered surfaces, but beds of light-brownish-gray 

to brownish-gray dolomite, much like those in the 

underlying formation, continue to appear at wide intervals for several hundred feet above the contact. 

Most of the rock is coarsely crystalline, but in the 

upper part of the formation there are a few beds of 

light-gray fine-grained dolomite resembling the overlying Sevy Dolomite and a few beds of medium-gray 

to brownish-gray coarsely laminated fine-grained dolomite. Although most of the dolomite contains only 

small scattered nodules of yellowish-gray chert, chert 

and other siliceous material make up more than half 

of one layer about 30 feet thick. 

The original textures and structures of the Laketown Dolomite have been greatly modified by diagenesis. The few faintly laminated beds contain indications of fine bedding and some crossbedding; elsewhere the bedding is generally indistinct and the beds 

. are at least moderately thick. The competence of the 

rock is therefore mainly controlled by the spacing of 

small fractures. Some laminated beds contain concentrically layered ellipsoidal bodies having cores of 

silica, which may be remnants of algal structure. 

Fragments of corals and brachiopods are scarce and, 

where present, are replaced by coarse-grained dolomite. Vugs commonly less than 2 inches across are 

scattered through much of the moderately coarse 

grained dolomite; many of them are lined with coarse 

crystals of dolomite and a few contain quartz. 

The thickness of the Laketown Dolomite is about 

600-700 feet, as estimated from the section east of the 

Cave Creek Reservoir. Laketown of similar thickness 

underlies about a mile of the crest of the high ridge 

between Cave Creek and Cleve Creek just north of 

the place where the road reaches the crest of the ridge 

north of Cave Mountain. Here., however,. the internal 

structure of the Laketown is probably complex, for the 

beds commonly dip 10-40° more steeply than the basal 

contact. 

Two collections of poorly preserved fossils were 

made. from the upper part of the formation along the 

crest of the ridge north of Cave Mountain. W. A. 

Oliver, Jr., and He.len Duncan (written commun., 

1960) reported that the collections contain F avo sites 

sp., 0 atenipora? sp., horn corals, and phacelloid rugose 

corals, which they regarded as probable Silurian. 

During Silurian time the Connors Pass quadrangle 

presumably was on a moderately stable shelf betwe.en 

an actively subsiding geosynclinal area to the west and 

a more stable belt to the east. Intense diagenetic 

dolomitization has all but obliterated the initial character of the Silurian sediments. The fact that many 

of the fossil remnants in the sediments are coralline 

indicates at least a moderately warm sea; the absence 

of terrigenous detritus suggests that this sea was bordered by lowland areas. 

DEVONIAN SYSTEM 

SEVY DOLOMITE 

The Sevy Dolomite, a fine-grained light-gray dolomite at least 900 feet thick, overlies the Laketown 

Dolomite. Nolan (1935) named it for the excellent 

exposures in Sevy Canyon in the northern Deep Creek 

Range, Utah, and since then the formation has qeen 

most thoroughly studied by Osmond ( 1954). 

The Sevy Dolomite underlies many small areas on 

the crest and the west flank of the Schell Creek Range, 

the steep west flank of the prominent hill 1-3 miles 

south of the mouth of Steptoe Canyon, and the west 

flank of the range just south of the mouth of the 

canyon of Cooper Wash. No complete section of the 

Sevy can be found in this quadrangle, for it appears 

only in much-faulted areas and is not generally well 

exposed. A section can be pieced together, however, 

for the basal beds, at least, are exposed on the north 

wall of the large canyon 2.5 miles east-northeast of 

Cave Creek Reservoir, most of the middle beds are 

exposed on the hill south of Steptoe Creek, and the 

beds near the top are exposed south of Cooper Wash. 

The Sevy Dolomite generally forms gentle to moderately steep slopes broken by many persistent narrow 

ledges and a few less continuous cliffs. The ledges 

and intervening benches are much more regular and 

continuous than those formed by other rocks. Only 

the slopes formed by part of the Guilmette Formation 

of Middle and Late Devonian age, and by part of the 

Ely Limestone, of Mississippian, Pennsylvanian, and 
DEVONIAN SYSTEM 23 

Permian age, remotely resemble those formed by the 

Sevy Dolomite, but the ledgy units in the.se other 

formations are brownish or yellowish gray, whereas 

those in the Sevy are very light gray. 

In most places the base of the Sevy is marked rather 

sharply by the main body of fine-grained dolomite, 

but in a few places similar beds are also present in 

the uppermost part of the dominantly coarse-grained 

underlying Laketown Dolomite, and exposures are too 

scarce for one to follow the contact in detail. 

The Sevy Dolomite is a medium-light-gray to darkgray rock that weathers to a distinctive very light gray 

to light gray. The beds underlying the benches are 

faintly light brownish gray, but this variation in hue 

is apparent only nearby, for at a distance the Sevy is 

masked by the color of the ledges and of the rubble 

derived from them. The rock is very fine grained to 

aphanitic. The beds generally break along small fractures rather than along the distinct bedding planes 

that are spaced 1-5 feet apart. The bench-forming 

beds are faintly laminated. Finely crenulated stylolites in the uppermost. beds are exposed near Cooper 

Wash. Most of the. Sevy contains little detrital material, but the darker laminae appear to be slightly silty. 

Where best exposed on the steep slopes of the hill 

south of the mouth of Steptoe Canyon, the Sevy is 

divisible into two ledge-forming units separated by a 

cliff-forming unit. The lower ledge-forming unit is 

about 340 feet thick. The beds in it are commonly 

about 1-2 feet thick, but some of those near the top 

are as much as 5 feet thick. Some of the ledge-forming beds in this unit contain a sedimentary breccia, 

and some of the intervening bench-forming beds are 

faintly laminated and are separated by minor disconformities. The middle, cliff-forming unit is 170-220 

feet thick. Some of it is very indistinctly bedded, and 

some of it is massive and weathers to slightly rounded 

bosses. Toward the more gently sloping north and 

south spurs of the hill, the cliff is so subdued that 

this unit is no longer mappable; the cliffs are only on 

exceptionally steep slopes. The upper ledge-forming 

unit, which is at least 340 feet thick, resembles the 

lower one except that some of its beds form rounded 

ledges rather than the usual blocky ones. In this section the upper unit is overlain by a low-angle fault 

that cuts out the overlying Simonson Dolomite, part 

of the Guilmette Formation, and possibly also the 

uppermost beds of the Sevy Dolomite itself. A mile 

farther south some intraformational conglomerate and 

minor disconformities appear near the top of the 

Sevy. 

Along Tamberlaine Canyon and on the high ridge 

southwest and south of Kolcheck Basin, there is a 

sandy layer, less than 20 feet thick, near the top of 

the Sevy. Southwest of the basin, quartz sand is very 

abundant in this layer, which there includes a few 

light-gray to very pale brown quartzite beds, but elsewhere makes up no more than 50 percent of this layer. 

Osmond ( 1954, p. 1918-1920, fig. 9) showed only a few 

feet of sandy dolomite near Cooper Wash, but he remarked that a dolomite containing less than 30 percent of quartz sand is hard to recognize in the field 

as a sandy bed. In some places the grains are frosted. 

The quartz grains in this layer range in diameter from 

0.05 to 0.5 mm and are commonly subrounded to well 

rounded. Rocks containing abundant quartz also contain more angular grains that interpenetrate and are 

partly cemented by secondary silica, which may have 

been derived from the outer parts of the angular interpenetrating grains. In other words, angularity of 

these grains is considered a diagene.tic feature. The 

quartz sand is very clean and contains only a few 

grains of iron oxide and leucoxene; the quartz grains 

enclose a very few small crystals of rutile, tourmaline, 

and apatite. 

The thickness of the Sevy Dolomite is estimated to 

be about 900 feet near Steptoe Canyon, but inasmuch 

as the top of the formation is faulted and the position 

of the base is uncertain, this thickness is a minimum. 

If the measured dip of the Sevy near Steptoe Canyon 

is 5° too low, the formation may be as much as 1,050 

feet thick. No more than 500 feet of the Sevy is exposed in any block northeast of Cave Creek. 

The Sevy Dolomite contains few fossils, and only 

three collections were made from it in the Connors 

Pass quadrangle. W. A. Oliver, Jr. (written commun., 1961), identified F erestromatopora sp. and an 

amphiporoid stromatopora in one collection, Clathrodictyon sp. in the second collection (written commun., 

1959), and indeterminate brachiopod fragments in the 

third. J. T. Dutro, Jr. (written commun., 1961), 

identified Cryptonella~ sp. in the third collection. 

These fossils have a long age range, but the ages are all 

compatible with those assigned to the formation in 

other areas. Nolan ( 1935, p. 19) dated the type Sevy 

Dolomite as Devonian, and probably Middle Devonian, because of the unconformity at its base and its 

gradation at the top into well-dated Middle Devonian 

rocks. Osmond (1954, p. 1928-1929) favored a Late 

Silurian and Early Devonian age for the Sevy, placing less emphasis on the nature of the top of the 

formation than Nolan did and more on the occurrence 

of H alysites sp., H rilysites cf. H. catenula:ria Linne, 

which he found low in strata correlated with the Sevy 

Dolomite in the Ninemile Canyon area of the southern part of the Egan Range. He also inferred that 
24 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

the Sevy was transgressive, being older in the west 

than in the east. I regard the Sevy Dolomite in this 

quadrange as mostly Early Devonian and in minor 

part Middle Devonian, but it may contain some rock 

older than Early Devonian. 

Sevy Dolomite occurs throughout most of eastern 

Nevada and western Utah, where it is of uniform 

lithology and is 500-1,500 feet thick, the thinner sections being mostly near the Connors Pass quadrangle. 

It is noteworthy that the fine-gTained Sevy Dolomite 

lies near the middle of the thickest part of the middle 

Paleozoic dolomite sequence and that it overlies the 

only widespread unconformity in these rocks. 

The origin of the Sevy Dolomite seems to be somewhat different from that of the adjacent coarsegrained dolomite. The removal of dolomite during 

the widespread hiatus preceding deposition of the 

Sevy and the resolution of this dolomite by the sea 

perhaps caused especially high concentrations of magnesium in the Sevy sea (Osmond, 1954, p. 1930) and 

the primary deposition of the fine-grained dolomite. 

Such a situation would have been ideal for the deposition of primary dolomite, or perhaps for relatively 

rapid replacement of a calcareous sediment. 

SIMONSON DOLOMITE 

The Simonson Dolomite, a coarse-grained brown 

dolomite 600-700 feet thick that includes some strongly 

laminated beds, conformably overlies the Sevy Dolomite. This formation, which is slightly more extensive than the underlying formation, was named the 

Simonson Dolomite by Nolan (1935, p. 19) for exposur~ in Simonson Canyon in the northwest part of 

the Deep Creek Range. Osmond (1954) divided the 

Simonson into four informal members : a basal buff 

member, a lower alternating member, a brown cliffforming member, and an upper alternating member. 

The Simonson Dolomite is exposed in several small 

areas along the crest and the west flank of the Schell 

Creek Range between Cave and Cleve Creek, along the 

east side of Cooper Wash, and along Tamberlaine Canyon. The best section, and probably the one measured 

by Osmond, lies on the spur south of the mouth of 

the canyon, tributary to Steptoe Creek, that runs 

through the northernmost outcrops of volcanic rocks 

along the west flank of the range (pl. 1) . Slopes on 

the Simonson Dolomite are darker· than those on the 

Sevy Dolomite and are only faintly marked by ledges. 

The base of the formation is marked by the lowest 

appearance of a yellowish-gray to light-brownish-gray 

1 

medium- to coarse-grained thick-bedded to massive 

dolomite. In the lower part of the basal buff member, 

a few fine-grained dolomite beds like those in the Sevy 

\ Dolomite alternate with the coarser grained rock, and 

the upper part of the member is faintly laminated 

and so mew hat thinner bedded than the rocks below it. 

In the lower alternating member, conspicuous laminae of light-gray to light-brownish-gray dolomite alternate. with laminae of dark-brown dolomite (fig. 6). 

FIGURE 6.-Typical ledge in the lower alternating member of 

the Simonson Dolomite on the south wall of the canyon 

tributary to Cooper Wash at its mouth. Laminae are far 

more abundant and conspicuous than in the Fish Haven 

Dolomite. 

Individual laminae are paper thin to almost an inch 

thick. The contacts between the laminae are commonly very regular, but in a few places they are 

highly irregular, having undulations as high as a 

quarter of an inch. Prevailingly dark beds in units 

a few feet to a few tens of feet thick form small 

benches and alternate with equally thick or slightly 

thicker cliffy units of lighter color. Minor unconformities are beneath some of the brown laminae 

within and possibly between the. units. The brown 

laminae are commonly coarser grained than the gray 

laminae, and they contain fossil fragments. Some 

brown laminae also contain biostromal forms or are 

almost coquinas ; others are bioclastic. The darkbrown units thicken upward within the member, and 

the lower alternating member grades into the overlying brown cliff-forming member. 

In the southern part of the Coope.r Wash area, the 

brown cliff-forming member consists of three separate brown cliffy dolomite units that are separated by , 

weaker laminated rocks. Along Tamberlaine Canyon 

and 1.5 miles east of Cave Creek Reservoir, this member is relatively inconspicuous; in other places this 
DEVONIAN SYSTEM 25 

member cannot be recognized. In some. places there 

appears tube a single member ccmposed of laminated 

dolomite that is of more than the normal thickness. 

Either the thicknesses of the three upper members are 

varied, or in places the brown cliff-forming member is 

absent and the alternating members are juxtaposed. 

The brown cliff-forming member contains some biostromal beds and some dark-gray chert lenses 1-2 

inches thick and many feet long. In Tamberlaine 

Canyon the stratum that most resembles the brown 

cliff-forming dolomite member contajns many thin 

beds of dark-gray fine-grained limestone. 

The upper alternating member resembles the ]ower 

one, except that it contains widely scattered chert 

nodules. Near the top it grades upward from brownish-gray laminated dolomite to a medium-gray faintly 

laminated or unlaminated limy dolomite. 

In the Cooper Wash area the Simonson Dolomite 

is estimated from structure sections to be 600-700 feet 

thick. The minimum thicknesses of the individual 

members are: basal buff member, 200 feet; lower alternating member, 150 feet; brown cliff-forming member, 100 feet; and upper alternating me.mber, 150 feet. 

In what is presumably the same section, Osmond 

(1954, fig. 12) measured thicknesses of 207, 108, 87, 

and 131 feet for these respective members. 

No identifiable fossils were collected from the Simonson within the quadrangle, although fragments of 

corals and brachiopods are locally abundant. Elsewhere in this region the formation is sparsely fossiliferous, and as a whole its fauna is unquestionably Mjddle Devonian. The age of the base of the formation 

cannot be accurately determined because of the general absence of fossils at this horizon, but regionally 

the top of the formation is at or just beneath the Martinia kirki zone or the next younger Stringocephalus 

zone, both of Middle Devonian age. In detail the 

upper contact appears to fluctuate slightly with respect to these zones, which apparently range through 

several hundred feet of strata. In the Connors Pass 

area and in the Hamilton area (Humphrey, 1960), 

about 40 miles to the west, fossils probably referable 

to the M artinia kirki zone appear in the lowest limestone that is assigned to the overlying Guilmette Formation or its equivalent. But in several other places 

the Simonson Dolomite contains fossils of the younger 

Stringocephal!us zone. It seems more likely thrut our 

knowledge of the fossils and their range is not yet 

complete than that the four very persistent and distinctive members of the Simonson Dolomite cross time 

horizons so much at random. 

The coarsely crystalline doiomite in the Simonson 

was probably derived from a calcareous mud, some 

remnants of which are still preserved as limestone 

lenses, for the obliteration of most fossils and of much 

sedimentary detail indicates that the dolomite is secondary. The origin of the light-gray beds is more 

problematical, for they are not as coarse grained as 

the dolomite and they do not contain remnants of fossils or limestone. Osmond ( 1965, p. 1952-1953) believed that these differences recorded a periodically 

changing environment, and he described in detail the 

kinds of fluctuation that may have. occurred near sea 

level. He ascribed the gray beds to deposition or reworking at, or even above, sea le.vel and believed that 

the brown beds were deposited at slightly greater 

depths, more favorable. to organic life. One might 

wonder whether the color differences eould be due. to 

sorting of pigmented material during replacement by 

dolomite, as well as, or instead of, due to initial differences in the organic content of the sediments. The 

many minor disconformities in the alternating members of the formation indicate current activity, but 

the thinness of the laminae indicates that the currents 

were very gentle. Osmond explained this apparent 

contradiction as a result of periodic damping of wave 

activity, and offered several intriguing suggestions for 

the cause of this damping. The origin of the laminae 

may be alternatively explained, however, by changes 

in the local physio-chemical environment rather than 

by changes in the regional geographic environment. 

GUILMETTE FORMATION 

The Guilmette Formation, a sequence of limestone, 

dolomite, and a small amount of sandstone, is about 

2,000 feet thick and conformably ove.rlies the Simonson Dolomite. It was named by Nolan (1935, p. 20) 

for exposures in Guilmette Gulch, in the northeast 

part of the Deep Creek Range. In the Connors Pass 

quadrangle the distribution of the dolomite within 

the formation is ·highly irregular, and the informal 

members that have been mapped are therefore of 

merely local value. 

The Guilmette Formation underlies about 9 square 

miles of the quadrangle. It is extensively exposed in 

the topographically high area between Cave and Cleve 

Creeks and between Tamberlaine Canyon and the 

Taylor mining district; small outcrops also occur along 

Steptoe Creek, Cave Creek, and Grasshopper Canyon. 

The formation is so much faulted that no complete 

section has been found, and the rapid and irregular 

1 ateral ehanges in lithology make it difficult to piece 

together a meaningful representative section. A comparatively unbroken section of a large part of the 

formation is fairly well exposed on the upper slopes 

of the east side of Cooper Wash about 1-2 miles north 

of the section in the Simonson Dolomite. A less com-
26 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

plete but more accessible and more fossiliferous section 

extends across the south end of the prominent ridge 

1 mile east of the Taylor mining district; the only 

outcrops of the highest member of the formation are 

near the north end of the ridge. A large part of the 

formation, not cut by any large faults, is fairly well 

exposed on the east slope of a small valley about 2 

miles southeast of the mouth of Steptoe Creek. 

The mixed limestone and dolomite generally form 

narrow benches and gentle slopes that alternate with 

discontinuous cliffs. The limestone in the lower part 

of the formation forms higher cliffs, and areas in 

which dolomite is abundant contain long irregular 

cliffs diversified by knobs, buttresses, and chutes. Most 

of the sandy, silty, and shaly beds form gentle slopes, 

but in many places the sandst~ne marker bed near 

the middle of the formation forms a small cliff. 

Most of. the Guilmette Formation consists of thickbedded fine-grained gray limestone, thin-bedded finegrained silty limestone, dark-brown coarse-grained 

dolomite, light- to medium-gray fine-grained dolomitic limestone, light-brownish-gray coarse-grained 

dolomite, and pale-yellow-brown limy siltstone, in 

various proportions and successions. The base of the 

formation is placed at the bottom of the lowest thick 

limestone bed, or the dolomitic limestone, whichever 

is lower, but this horizon is an irregular surface and 

probably ranges through several score feet of section. 

Silty rocks generally first appear near the middle of 

the formation and become more abundant upward. 

Dolomite is moderately abundant near the base of the 

formation, most abundant near the middle, and scarce 

near the top. A thin, somewhat lenticular sheet of 

quartz sandstone or quartzite slightly above the middle of the formation makes a distinctive marker. The 

bulk of the formation can be divided in most places 

into three informal members, called in ascending order 

a, b, and c, but these members cannot be identified 

where the proportion of coarse-grained dolomite is 

very high or where the local structure is complex. 

These rocks are overlain between Cooper Canyon and 

Cooper Wash by a thick sequence of reef limestone, 

thin-bedded limestone, siltstone, and subordinate sandstone, quartzite, and conglomerate, which I can member d. 

MEMBER A 

The lowest member, a, of the Guilmette Formation 

is about 500-600 feet thick. East and southeast of 

the mouth of the canyon of Cooper Wash and northeast of Cave Creek it consists of a cliff-forming limestone, but between the mouths of the canyons of 

C~oper Wash and of Steptoe Creek it is mainly dolomite and the slope~ are gentler. Part of the transition 

FrGURE 7.-Typical exposure of basal thick-bedded limestone of 

member a of the Guilmette Formation (Dga). The dip slope 

to the right is underlain by the overlying member b (Dgb). 

The gentle slope, broken by small ledges, in the left foreground 

is underlain by the upper part of the Simonson Dolomite ( Ds). 

View is northward across the canyon tributary to Cooper 

Wash at the mouth of the canyon. 

between the two facies of member a is illustrated in 

figure 7, a photograph of an area where the nearer 

cliffs consist mainly of limestone and the distant slopes 

are underlain by beds that are at about the same 

stratigraphic horizon but are more dolomitic. The 

base of the formation lies at the foot of the prominent 

cliff, and much of the rock exposed in the dip slope 

to the right of the cliff belongs to member b. East 

of the mouth of the canyon of Cooper Wash the cliffy 

limestone is underlain by a thin fine-grained thinbedded gray dolomitic limestone, which, however, is 

faintly laminated and so much fractured that its 

structural relations to the cliffy limestone are uncertain. Southeast of the mouth of this canyop., member 

a consists mainly of sparsely fossiliferous and slightly 

bluish gray cherty fine-grained limestone. Here thick 

lenses of cliff-forming thick-bedded to massive limestone are separated by thin-bedded limestone. Inasmuch as faults are along the periphery of at least the 

southernmost lens, it is uncertain whether the lenses 

are primary features or were formed by shearing. 

Northeast of Cave Creek, siltstone partings and silty 

dolomite appear low in member a, which there contains widely scattered chert nodules and sparse remnants of brachiopods, gastropods, and crinoids. 

Between the mouths of Cooper Wash and Steptoe 

Creek, member a is more dolomitic than elsewhere. 
DEVONIAN SYSTEM 27 

East of the wash a few dark-brown coarse-grained 

dolomite beds 3-15 inches thick crop out about a mile 

north of the last cliffy limestone. Just northwest of 

the wash, on the southwest spur of hill 9,085, darkbrown dolomite, gray dolomite, and limestone are 

about equally abundant, and it is therefore hard to 

separate member a from member b. On this hill, 

member b is underlain by about 800 feet of massive 

to very thick bedded coarsely crystalline light-pinkishgray to light-brownish-gray dolomite. Although a 

minor thrust fault, which brought some of the Guilmette Formation over Chainman Shale and some of it 

over other rocks of the Guilmette Formation, complicated the situation, much of the light-brownish-gray 

dolomite is probably in member a. Between the 9,085,. 

foot hill and Steptoe Creek, member a is more than 

300 feet thick and consists mainly of dark-brown 

dolomite. 

At several places in this area of abundant dolomite, 

local sedimentary features show some interesting relations between several varieties of dolomite. East of 

Cooper Wash some of the brown dolomite beds contain algal heads or stromatoporoids that enclose pockets of light-gray dolomite. On the · southwest spur of 

hill 9,085 is a lens of intraformational conglomerate, 

1 foot thick and 5 feet long, that consists of small 

angular pebbles of gray dolomite, dark-brown dolomite, and chert in a gray matrix of calcareous dolomite. Along the front of the range northeast of the 

hill there is more intraformational sedimentary breccia 

and conglomerate, consisting of gray-dolomite fragments in a matrix of dark-brown dolomite. The breccia grades laterally from larger rectangular blocks of 

gray dolomite separated by small septa of brown dolomite to unbroken gray dolomite. The relations between the several kinds of coarse-grained rock suggest 

that such rocks were formed at various times, but all 

of them are younger than the fine-grained dolomite 

and possibly younger than the chert. Furthermore, 

the fine-grained dolomite and chert were sufficiently 

consolidated to break into angular fragments before 

the coarse dolomite was formed. Clearly, however, 

inferences about the origin of dolomite drawn from 

one outcrop in this area cannot be applied too generally. 

MEMBER B 

Member b of the Guilmette Formation is 300-700 

feet thick and consists of alternating layers of darkbrown coarse-grained dolomite and shaly or thinbedded limestone. In some places this member also 

contains a small amount of the light-brownish-gray 

coarse-grained dolomite and a thin marker bed of 

sandstone or quartzite. 

The limestone is commonly a slightly bluish to 

medium-gray rock containing crinkly beds lJ.t,-4 inches 

in thickness, separate~ by yellow-brown silty partings. 

Many of the limestone beds are fossiliferous, and many 

fossils weathe-r out and lie on the surface. Atrypa spp. 

and athyrid and spiriferid brachiopods are very common, and some corals and brachiopods are generally 

present. This fossil assemblage and weathering habit 

occur most commonly in rocks of the lower or middle 

parts of member b, but some speciments of Atrypa 

are found in a slightly younger assemblage, and some 

of the fossils of member c also weather free from the 

enclosing rock. 

Dolomite is most abundant in member b in hill 9,085 

and is least abundant south of Cooper Wash. Most 

of it is dark brown and thin bedded to moderately 

thick bedded, but some of the light-brown massive 

dolomite on hill 9,085 may belong to member b. Small 

dark-brownish-gray chert nodules are widely scattered in dark-brown dolomite. Locally the dark-brown 

dolomite interfingers with the limestone; the contacts 

between these rocks, which are mostly sharp, generally 

extend along the more conspicuous bedding planes, but 

in some places they cut across them. Faint laminae, 

along which the rock does not part, end abruptly 

against the dolomite, but some laminae also continue 

across the contact. Most sedimentary details obviously were obliterated during the replacement of the 

limestone by dolomite. Tongues of dolomite replace 

slightly more shaly limestone rather than thick-bedded 

limestone. 

A quartzitic sandstone bed that has been mapped as 

a marker lies either within member b or in the basal 

part of memb~r c. It is commonly 15-30 feet thick, 

but in some places it is absent and in other places it is 

as much as 60 feet thick. The rock is light gray and 

weathers grayish pink to very pale orange. It is 

faintly laminated, and generally parts along planes 

2 inches to 4 feet a part. 

In thin section it is seen that clastic grains generally make up about 50 percent of the rock, or rarely 

as much as 70 percent. They consist almost entirely 

of quartz which contains a few inclusions of tourma- ' . line, apatite, and zircon, and also very small particles 

of black opaque iron oxide ( ~) , tourmaline, zircon, and 

leucoxene. The quartz grains are 0.1-0.9 mm in diameter and are subangular to well rounded. The grains 

are commonly loosely packed, with point-to-point or 

line-to-line contacts, in a calcite cement. Less commonly the quartz grains interlock or are separated by 

a little quartz or clay cement. . 

The upper part of member b contains less dolomi~ 

and more silty limestone than the lower part, and It 
28 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

includes some yellowish-brown limy siltstone. It is as 

fossiliferous as the lower part, but contains more corals 

and .fewer brachiopods. 

MEMBER C 

Member c of the Guilmette Formation is about 400-

600 feet thick and is more uniform in character than 

the underlying members. Most of it consists of silty 

limestone and limy siltstone, but it also contains some 

thin layers of dolomite. The limestone is generally 

fine grained, slightly bluish gray, and thin bedded 

although a few layers less than 20 feet thick contain 

beds as much as 4 feet thick. Some of these layers 

contain abundant corals and algae or stromatoporoids 

and may be biostromes. Some of the limestone also 

contains a little nodular to slightly lenticular darkgray chert that weathers light brown. 

MEMBER D 

In one small area on the east side of the divide between Cooper Canyon and Cooper Wash, about 600 

feet of limestone, interbedded with small amounts of 

sandstone, quartzite, and conglomerate, overlies member c of the Guilmette Formation with apparent conformity and is unconformably overlain by the Pilot 

Shale. These rocks are member d of the Guilmette 

Formation. 

The basal 50 feet of member d consists of platy 

limestone, shale, sandstone, quartzite, conglomerate, 

and sedimentary breccia. The coarser clastic rocks 

appear to be lenticular, for they are less extensive 

along their strike than the finer grained rocks. The 

quartzite, the most abundant of the clastic rocks, is 

light gray to light olive gray and weathers pale reddish brown. As seen in thin sections, about 90 percent 

of the quartzite consists of angular to subrounded 

quartz grains only 0.02-0.2 mm in diameter. A few 

clastic grains of zircon and tourmaline are also present. 

The grains are cemented by fairly abundant clay, sericite, and traces of iron oxide, calcite, and chalcedony. 

The breccia, forming beds 4-12 inches thick, consist of 

medium-gray to brownish-gray quartzite fragments. 

The small grain size, poor sorting and rounding of 

grains, and large clay content and weathering color of 

the sandy rocks are more characteristic of those of 

Mississippian age than of those of middle Paleozoic 

age; apparently they are harbingers of a changing 

tectonic environment. 

The upper 550 feet of member d has more shaly 

limestone than the lower part and contains a few 

thick biostromal limestone beds resembling the rocks 

in member c. Near the top of member d there are 

conspicuous outcrops of reef limestone containing a 

rich fauna of partly silicified corals. 

FAUNA, AGE, AND CORRELA.TION 

The limestone beds of members b, c, and d of the 

Guilmette Formation are among the most fossiliferous 

rocks in the area. Brachiopods are very abundant 

and well preserved in the shaly limestone of the lower 

part of member b. Many of the shells are phosphatic, 

and the shells weather free with both valves intact. 

Higher in member b corals are more abundant, the 

brachiopods more varied, and the Atrypa perhaps 

somewhat larger. In member c the shaly beds contain 

abundant brachiopods and the limy beds contain corals. Silicified Oladopora? is especially abundant near 

the top of the member. Corals are even more abundant near the top of member d than in member c. All 

fossils identified from the Guilmette are listed in 

table 3. 

J. T. Dutro, Jr., stated: 

The fossils of the Guilmette Formation are predominantly of 

Late Devonian age although the poorly preserved material from 

member a may well be Middle Devonian. Member b contains 

a predominantly brachiopod assemblage that is of early Frasnian age and probably represents the "Spi·rifer" argentarius 

zone of Merriam (1963, p. 53). All the fossils from members 

c and d are also of Frasnian age, and representatives of both 

the Paohyphyllum and "Martinia" nevadensis zones of Merriam 

are present. As Merriam has indicated (1963, p. 54), these two 

are facies assemblages of approximately the same age significance. The brachiopod-rich assemblage in member c can be 

compared favorably with the Sly Gap fauna of New Mexico 

(Stainbrook, 1948) . Common species and genera between the 

two assemblages are: Oalvinaria bransoni Stainbrook, Deoonoproduotus vulgaris Stainbrook, Douvillina, Gypidula munda 

Stainbrook, Nervostrophia, Nudirostra spp., Pugnoides sohuoherti Stainbrook, Spinatrypa, Thomasaria, Warrenella spp., 

Alveolites, Maogeea, Paohyphyllum, Tabuwphyllum, and Phaoellophyllum. No representatives of Merriam's Oyrtospirifer 

zone (post-Frasnian) have been identified from this quadrangle. 

ENVIRONMENT 

During the early part of Guilmette time, the quiet 

deposition that had been going on in much of the 

eastern Great Basin since Middle Ordovician time 

continued. In the Connors Pass area, as elsewhere 

through Guilmette time, progressively less dolomite 

and more limestone were deposited, this change suggesting that concentration of magnesium in the sea 

was significantly reduced. As magnesium content was 

reduced, precipitation of, or replacement by, the available magnesium depended increasingly on local environment, and consequently the dolomite beds are 

less continuous. 

The macroscopic sedimentary features indicate that 

both the light-brownish-gray and the dark-brown 

coarse-grained dolomite types replaced limestone and 

the fine-grained gray dolomite. At least the darkbrown dolomite preferentially replaced shaly dolomite, and perhaps the light-brownish-gray dolomite 
DEVONIAN AND MISSISSIPPIAN SYSTEMS 29 

also preferentially replaced the more massive and coralline limestone. Locally, pebbles and blocks of each 

coarse-grained type. are embedded in the other, so 

there is not a clear-cut age relation between them. 

Both contain sedimentary fragments of the finegrained gray dolomite, in which inclusions of the 

coarse-grained dolomite do not appear. Apparently 

the fine-grained gray dolomite is older than the coarsegrained types, and ~onceivably it is a primary dolomite. If these deductions are valid, deposition of 

primary dolomite, or very early replacement dolomite, 

ceased generally during early Guilmette time and 

ceased entirely in about middle Guilmette time, whereas the replacement by secondary dolomite reached a 

climax during middle Gui1mette time and continued 

into late Guilmette time. 

The sandy rocks of member d are thG oldest deposit-s in the Connors Pass area that reflect orogenic 

movements occurring near the end of Guilmette time 

in northwest Utah and south-central Nevada. The 

reef limestone above these clastic beds indicates that 

the seas were shallow, and thus for a while the clastic 

sediments could not be transported westward beyond 

the downwarping area near the Thomas and Dugway 

Ranges and did not spread more 'viclely until downwarping had ceased and the basin was filled with 

sediments. 

DEVONIAN AND MISSISSIPPIAN SYSTEMS 

PILOT SHALE 

The Pilot Shale, a dark shale and siltstone as much 

as 480 feet thick, overlies the Guilmette Formation 

with apparent disconformity. Spencer (1917) named 

this shale for outcrops at Pilot Knob, west of Ely. 

The Pilot Shale commonly forms the lowest of three 

conspicuous units, two of shale and a middle one of 

limestone, largely of Mississippian age. The Pilot is 

the lower part of Hague's White Pine Shale ( 1892). 

The name White Pine was later abandoned and replaced in the Eureka district by the Pilot, Joana, and 

Chainman Formations (Nolan and others, 1956). The 

Pilot Shale has been widely recognized in eastern 

Nevada and western Utah, but has nowhere been intensive.Iy studied. 

In the Connors Pass quadrangle the Pilot Shale 

occupies about 2 square miles in the northern twothirds of the west side of the Schell Creek Range. It 

generally forms narrow benches, gentle slopes, and 

saddles between outcrops of resistant limestone formations. In many places it forms a veneer on the dipslope side of ridges eroded in the Guilmette Formation (fig. 7). In many other places it forms taluscovered slopes below cliffs of the overlying Joana 

240-303 0 - 67 - 3 

Limestone. Slopes on the Pilot Shale are generally 

treeless. 

Outcrops of Pilot Shale are few and small, and nowhere is as much as 5 percent of the formation exposed. The best exposures in the area are those on 

the south side of Square Top Hill, south of the lower 

part of Steptoe Creek, and those just north of the 

large silicified area in the Taylor mining district. 

Many slopes formed by Pilot Shale are. covered with 

large chips and small plates of siltstone typical of 

many of the exposures, which, though useful in identification of the formation, mask the rarely exposed 

shalier rocks. 

The contact between the Pilot Shale and the Guilmette Formation is commonly smooth and unfaulted. 

The thicknesses of both units are fairly uniform and, 

because the transition from limestone to shale is gradational, the contact easily can be assumed to be conformable. The base of the. Pilot Shale was placed at 

the top of the highest thick limestone of the Guilmette 

Formation, a position probably slightly higher than 

that chosen by Clark and Becker ( 1960, fig. 2). At 

one place, however, in a small valley that drains eastward from the divide between Cooper Wash and 

Cooper Canyon, the Pilot Shale is underlain by member d of the Guilmette Formation. The contact there 

is covered, but a disconformity is inferred because of 

the very small distribution of member d and because 

the contact dips 20-30° more gently than the Pilot 

and Guilmette rocks adjacent to the contacts. The 

relations resemble those on the bedding-plane thrust 

faults common in the older Paleozoic rocks, but there 

is much less evidence of movement along this contact 

than along most of the contacts known to be faulted. 

Presumably, therefore, this contact is a disconformity 

and member d is preserved only very locally as a hill 

beneath the Pilot Shale. 

The Pilot Shale consists mainly of shale and siltstone but includes some quartzite, limestone, and argillite. The proportions of these constituents are unknown because the finer grained rocks are generally 

masked by surface debris from the coarser grained 

ones. Shale and siltstone are probably about equal in 

abundance, and the other kinds of I"ock together probably make up less than 5 percent of the formation. 

Siltstone is more abundant in the lower part of the 

formation than in the upper part. It is dark gray 

and commonly weathers to pale-yellow-brown chips 

and plates, mostly 2-4 inches across but some as m~ch 

as 10 inches across. Some of the plates are reddish 

brown, especially near the base of the formation where 

a few thin beds of limestone are present. 
30 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

TABLE 3.-Fauna o.f the 

[Most brachiopods identified by J. T. Dutro, Jr. (written commun., 1960, 1961), corals by W. A. Oliver, Jr. (written commun., 1959, 1960, 1961), and a few mixed collections by 

argentarius zone; 10, Phillipsastraea o r lfartinia 

Unit (pl 1.) ___________ Member Member b Member c, lower part a 

Age __________________ Middle Middle Devonian Late Devonian 

Devonian or Late Devonian 

Faunal zone _______ --- ? 8? 8? or 9 9 9? 9 9? ? 9 10? 10 

------------ -

Field No.; U.S. s~ s~ s~ SrGeol. Survey lO ~ lO Cl":) 0') ~ 00 Ul~ Cl":) ~ Ul~ O')Ul~ 0 ~ 00 wtO 0') ~ ~ t- ~ 0 ~ 0 0 

colin. number in 00 c Cl":) ~ ~ t- Cl":) M Cl":) t- I~ 0') 0') I~ ~~~ 00 00 0') 

~2 t- 0 00 Cl":) lO 00 0') ~ ~ ~ lO t- ~ ~ Cl":) lO 1.0~ M Cl":)o:> Cl":) Cl":) t-0') ~~0') ~ Cl":) Cl":) lO ~ lO Cl":) Cl":) Cl":) ~ ~ parentheses ______ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~tO ~ ~ ~tO ~OOlO ~ ~ ~ oo:> 

00 00 00 0') 0 0 0 0 ootO ~ ~ ~ ~ ~ ~ ~ ~ ~ 0 0 e 0 0 e O')tQ 0 0 0 e 0 0 0 0 0 0 0 0 0 lO lO lO lO ~ ~ ~ ~ ~ ~ ~ ~ 1.0'-" ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 

-----------1--1-~- -----------------------------------

Brachiopods: 

Atrypa devoniana . Webster ________________________________________________________ -~- __ ---- _______________________ cf. 

Atrypa sp __________ -----X?------ X-- ____ X---- X -----------------------------·-- X X ___ ~-- ________ _ Calvinaria cf. C. 

bransoni Stain- brook _______________________ -~- _______________ ________ _____ ______ __________________ ~-- ___________ _ 

Calvinaria sp ________________ --- _____________ ---- ____________ --------- __ ----------X? X X? X? ___ X? __ _ Crurithyris sp _______ X X? ______________________________________ --- ____ ________ X? _________________ X? 

Cyrtospirifer g~~li~:e;~~~======== == === == = === === == == == == == ==== == === ==== === === === x? == ==== === === === == === === === === === placitus · . · · Stainbrook __________ _______________________ ________ _________ ___ cf. _______________________________ _ 

Devonoproductus cf. 

D. vulgaris Stainbrook _____ ____ _________________________________________ --- ____________ ------ ______________ X 

Devonoproductus sp ______________ .:. _________ ~- ___________ :__ ...:~ ___ -------- _______ X _____ _ _: _ ____ ______ :.__ 

~ze~~!~~ko~;;~~"P~== :: ::: ::: ::: x? :: :: x :: :: :::: :: ::: -x- ::: ::: ::: :::::-x-i::::::::::::::::: x? :::· ~~ Elytha sp ______________________________________________________ --- ---' _________ --- --- _____ X? ______ ---

Gypidula aff. G. 

munda Stainbrook _________________________________________________________________ ____________________ _ 

Hypothyridina sp. a 

(of Merriam, 1940) _____________ - :.. _- _-- __ - _____ - ____________ - _________ - --- --- __ - -- _-"'- _-- --- --- _- __ - _______ -- X 

Hypothyradina sp _______________ ___________________ --- __________ --- ___ - - _______ --- --- ___________ --- --- Nervostrophia sp __________________________________________________________ · _____ --- _____________ -_ --- X 

Nudirostra aff. N. 

carya (Crickmay) __ -- --- --- --- ________________________________ --- ___ -- ______ .:. ------X--- ______ X ---

~~~~~t!zz~ Pugnoides aff. ~~======= P. == === x? === === :: :: == ====-:x-i=========================================-~-======::: · · schucherti 

Stainbrook _______ -----------·----"' ______ --------~-- _______ --------------------------·.,.-----_.:._------

Pugnoides sp ________ -- --- --- --- --- -- -- -- -- -- ---- -- --- ---- --- --- --- --- -- ---- --- --- --- -- -·-- --- --- ------ Schizophoria sp ______ -- --- --- --- --- ________ -- ________________ --- --- ___ -- :_ ___ --- --- ------ --- --- --- --- --- Spinatrype monta- nensis (Kindle) ____ ----------- ___________________ cf. ____________________________________ __ _ aff. _____ _ 

Spinatrypa sp. (large)------:----------------------- __________ X _____________ X ___________________________________ _ 

See footnote at end of table. 
DEVONIAN AND MISSISSIPPIAN SYSTEMS 31 

Guilmette Formation 

c. w. Merriam (written commun., 1959). Zones are numbered in ascending order in the Devonian rocks, as applied in the Eureka, Nev., area; 8, Tylothyris zone; 9, Spirifer 

nevadensis zone (Nolan and others, 1956; Merriam, 1940)] 

Member 

Unit (pl !.)__________ c, 

middle 

part 

Age _________________ 

Faunal zone_~------- 10 

Field No.; U.S. s~ Geol. Survey 00~ eo 

colin. · number in 'A ~ 

~~ ~ 

parentheses ______ OOlO A 

e 0 

eo 

s~ 6ff5 SfA 00~ 00~ 00~ 

~~ t6A cbA ~~ 0~ 0~ 

t--lO ootO OOlO 

e e e 

Member c, upper part 

Late Devonian 

10 10? 10 

0 ,..; 00 0 1:'-- ~ ,..; ~ ~ 

0 0 00 0 ~ 00 00 00 0 ~ ~ ~ ~ ~ ~ C'r.l C'r.l ~ 

~ A A ~ A A A A A 0 0 0 ~ 0 0 0 0 0 eo <:0 <:0 11';) <:0 eo eo eo eo 

? 10 

~ 0 ~ C'l ~ 11';) ~ 

0 ,..; 00 0 ~ ~ eo 11';) lO ~ ~ ~ ~ ~ 

~ A A A A A A 0 0 0 0 0 0 0 eo eo <:0 eo eo eo eo 

10 

11';) 0 11';) eo ~ ~ 

A A 0 ~ 

eo 11';) 

Member d, 

upper part 

10? 10 

6,..; s~ s~ 00~ 00~ 00C'l 

~A ~A ~A 0~ 0~ ,..;~ 

OOlO OOlO OOlO 

e s s 

~ 

eo C'l 

A 

~ 

lO 

1-----------1-----------------· -------------~ ----------

Brachiopods: 

Atrypa devoniana Webster _______________________ ---- ___ cf. _________________ aff. _____________________________________ _ 

Atrypa sp __________ ------ - ----------------------- X X ---------- X ---------X------------ X X?--

Calvinaria cf. C. 

bransoni 

Stainbrook __________ ------------------------------------- X -------------- ------------------ .:. ___ --

Cyrtospirijer 

~ft?.~!~s~f~~~~ placi- ~~~ ~~ =~= =~= ~~~~ ~~~ ~~~ ~~~ =~~ ~~~ ~=~ :~ ~;~ =~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ ~~ =~~ ~~~~ ~~~~ ~~~~ ~~ tus Stainbrook _________________ aff. __________________________________________________ ~--- _________ _ 

Devonoproductus cf. 

D. vulgaris 

Stainbrook ______ ------------------------------------ X-------- X ------ ;.. __ ------------------------ Devonoproductus sp_ ---- -- ---- ---- ---- --- X --- --- --- --- -- --- --- -- --- --- --- --- -- --- -- --- ---- ---- ---- --

if~~~~~~~~~~~~=:::::::::::::::::::::~~::=::::::::::::::::::::::::::::::::::::::::::::::::::::::: Gypidula aff. G. 

munda 

Stainbrook __________ ---------- -------~------------------------------------ X --- -- --- ---- ---- ---- -- Hypothyridina sp. a (of Merriam, 

1940) __ ..: _ _ _ _ _ _ _ _ -- _ - -- - -:..- - --- ---- --- --- --- --- --- --- - - X --- -- - -- --- - - - - -- - - - - - -- --- ---- ---- ---.:. --

IJ~fv~ts~lf~~~~:~~~=== ==== == ==== ==== ==== === === === === ~~ === == === === == === === === === == === == === ==== ==== ==== == Nudirostra aff. N. 

1!:.~!~:[~1~~~;;~: :::: :: :::: :::: :::: ::: ::: :~: ::: ::: ~== := ::: :=: ~ ::: :>!_ ::: ::: :: :=: :: ::: :>!_?: :::: :::: :: 

Pugnoides aff. P. · schucherti 

Stainbrook ______ -- _- -- ---- ---- ---- --- --- --- --- --- --- -- --- X -- -·-- --- --- --- -- X -- --- ---- ---- ---- --

~~~~~a::r:~~P--~~= ==== == ==== ==== ==== === === === === === === == === -x_- == === === === === ~ -x_- == === ==== ==== ==== == Spinatrypa montanensis (Kindle) ___ --------------------------------- ___ -- cf. ___ -- ___ --- ___ --- -- --- -- ___ ---- ---- ---- --

S~J;,.~~iJ~~~~~----- ---- --1---- ---- ---- --- --- --- --- --- --- -- --- --- -- --- --- --- --- -- --- -- --- ---- ---- ---- --
32 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

TABLE 3.-Fauna of the 

Unit (pl 1.) ___________ Member Member b Member c, lower part a 

Age __________________ Middle Middle Devonian Late Devonian 

Devonian or Late Devonian 

Faunal zone __________ ? 8? 8? or 9 9 9? 9 9? ? 9 10? 10 

----------- -

Field No.; U.S. Seo s~ s~ s~ Geol. Survey ~ C'l ~ C'l":l ~ eo 00 Ul~ C'l":l "o::j! UlC"l ~UlC"l 0 ~ 00 ri1C'l ~ c:o ~ ~ eo 0 ~ 0 0 

colin. number in 00 0 C'l":l C'l C'l ~ C'l":l C'l":l C'l":l ~ I~ ~ a;, J.~ "o::!!l~ 00 00 ~ ~~ ~ 0 00 C'l":l ~ 00 ~ C'l eo ~ ~ ~ C'l ~ C'l":l ~ ~ "o::j! C'l":l C'\":)0:. C'l":l C'l:l C'l~~ "o::j! "o::j! C'l":l 0~ C'l":l ~ ~ ~ C'l":l C'l":l C'l":l ~ ~ parentheses ______ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~0) 

~lC ~~ ~00~ ~ ~ ~ 00~ ~ ~ ~ ~ ~ ~ ~ ~ ~ 00 00 00 ~ 0 0 0 0 0 0 e 0 0 e a;,~ 0 0 0~ 0 0 0 0 0 0 0 0 0 ~ ~ ~ ~ eo eo eo eo eo eo c:o eo ~......,... eo eo eo ......,... eo eo eo eo eo eo eo eo eo 

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

Spinatrypa sp_ - - _ - _- _ _ _ _ _ _ _ _ _ _ _ X _ _ X X _ _ X _ _ _ _ _ _ _ _ _ X _ _ _ X - - - X __ -- __ - _ _ X - - - __ - _- - _ _ _ _ _ _ _ - __ _ 

"Spirifer" cf. "S." argentarius Meek__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ X _______________________________________________ _ 

"Spirifer" cf. "S." strigosus Meek _______________________________________________________ -- ___ X ___________________ _ 

Spiriferoid brachio-

~~};~:~t~}i~~~~~~= :: ::: ::: ::: ::: ~ ~ ~= ~ ~ :~:?: :: ::: :::: ::: ::: ::= ~~ :: :=:: ::: ::: ~~ :: ::: ::: ::: ::: ::: 

Tylothyris sp _____________ X? ______ ------------------------------------------------------------------- Thomasaria cf. T. · altumbona Stainbrook _____________________________________________________ --- ____________ --- _____ --- ______ X 

Warrenella cf. W. 

Corals: w~~~~!~zl:~~c~-~~:~= == === === === === == == == == == ==== == === ==== === === === === == ==== === === -~- == === === === === x? Alveolites sp ______________________________________________________________________ --- ______________ ---

Aulopora sp _________________ X? ________________________________ -------- X --- --- --- -- ___ --- ___ --- ---

~r!~!i}:Z1~:::_~~=== :: ::: ::: ::: ::: :: :: :: :: :: =::= :: =:: :::: ::= ::: ~! ::: :: :=:: ::: ~; ::: :: ::= ::: ::: :=: ::: 

Chonophyllum sp. cf. 

C. infundibulum (Meek) ___________________________________________________________________________________________ _ 

Cladopora sp ____ ·_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ X ? _ - _ - - _ _ _ _ _ _ _ - _ _ _ _ _ _- - -- Horn corals indet_ ___________ X ________________________________________ X ______ --- _____ --- ______ --- Macgeea sp __________________________________________________________ X X? X? ___ X 1 ________________ _ 

Pachyphyllum sp ____________________________________ - ____________ - - _- -- ---- --- --- --- -- --- --- --- --- --- Pachypora sp __________________________________________________ X- _______________________ --- ______ --- Phacellophyllum sp ______________________________________________________ ---"'" X ___ X 1 ________________ _ 

Phaceloid coral · 

species indet_ _ _ _ _ _ _ _ _ _ _ _ _ _ X ___ -- -- -- -- -- ---- -- --- ---- --- --- --- --- -- ---- --- --- --- -- --- --- --- --- --- Ramose favositoid coral_____________ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ X ______________ --- _-- --- ---

Rugose corals indet ___________________________________ ---- ______ --- --- -- ---- --- --- --- -- -·-- --- --- --- ---

Striatopora sp _____________________ -- -- -- -- -- ---- -- --- ---- --- --- --- --- -- ---- ,...-- --- --- -- --- --- --- --- ---

fi~~~?~:~~~~~== :: ::: ::: ~; ::: :: :: :: :: :: :::: :: ::: :::: :=: ::: ::: ::: ~ :~: ::: ~? ::: :: ::: :=: :=: ::: ::: 

Thamnoporid coraL ,. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ - --- _ - _ ~ -- --- - - --- --- --- --- - --

Gastropods: 

Murchisonia sp ______ X X? _____________ -- __ -- -- __ -- --- _--- --- --- --- --- -- ---- --- --- --- -- --- --- --- --- --- Bellerophon tid 

gastropod (small) __ X X _________ -- -- -- -- -- ---- -- --- ---- --- --- --- --- -- ---- --- --- --- -- --- --- ---- Platyceratid gastro- pod, indet ______________________________________________________________________________________ X 

See footnote at end of table. 
Guilmette Formation-Continued 

Unit (pl 1.) _________ _ 

Age _________________ 

Faunal zone _________ 

Field No.; U.S. 

Geol. Survey 

colln. number in 

par en theses ______ 

Member 

c, 

middle 

part 

10 

6~ W.co eo IO O'.l 

~O'.l co ool.Q 0 ~ 0 

eo 

-

6~ W.c-:~ 

J,O 

O',)O'.l 

t--lO 

~ 

--

DEVONIAN AND MISSISSIPPIAN SYSTEMS 

Member c, upper part 

Late Devonian 

10 10? 10 ? 

6~ 60',) W.c-:~ w.~ 0 ..-i 00 0 t-- C'l ..-i C'l co O'.l 0 

~~ IO 0 0 00 0 C'l:) 00 00 00 0 0 ..-i 

eoO'.l ~ ~ co co ~ ~ co co ~ l.Q l.Q OO'.l 

ool.Q ~l.Q 0 0 0 0 0 0 0 0 0 0 0 ~ ~ 0 0 0 O'.l 0 0 0 0 0 0 0 

eo <:0 <:0 l.Q eo eo eo eo eo <:0 eo 

----- - - - - --- ----- -

10 10 

co C'l O'.l l.Q C'l l.Q 0 00 0 O'.l O'.l eo l.Q eo ~ ~ co -.:1'1 -.:1'1 co C'l 

0 0 0 0 0 0 0 0 0 0 0 0 0 O'.l eo eo eo eo eo eo l.Q 

- - - - - - -

33 

Member d, 

upper part 

10? 10 

6.-~ 6~ 6~ w.~ W.c-:~ W.c-:~ 

J,o O'.lO'.l 

I~ ~0 OO'.l ~tO ..-iO'.l ool.Q ool.Q 

~ ~ ~ 

------

co 

eo 

C'l 

0 

O'.l 

l.Q 

-

Spinatrypa sp______ ____ __ ____ ____ X _______________________________ --- --- --- - - X -- --- ---- ---- ---- --

"Spirifer" cf. "S." 

argentarius Meek _________ __________________________________________________ -- --- -- ___ ---- ---- ---- --

"Spirifer" cf. "S." 

strigosus Meek ________________________ X ______ ______ X ___________ --- ___ --- -- --- -- --- ---- X ---- --

Spiriferoid brachiopod, indet_ _ _ _ _ _ _ X _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ --- -- - -- - -- - - - - - - -- --- -- - -- --- - ---- ---- --

~ft!S~~!P=== ==== :: :=:= :=:: =~= ~; ::: ::: ::: :=: ::: ~ ::: ::: := ::: ::: :=: ~~ :: ::: :: ::: :::: :::: :::: :: 

Thomasa ria cf. T. · altumbona · Stainbrook _______________________________________________________________ - -- --- -- ___ ---- ---- ---- --

Warrenella cf. W. 

eclectea Crickmay _ _ _ _ _ _ _ _ _ _ _ X _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____________________ - X -- - -- - - __ - ---- --- - ---- --

Warrenella sp __________ -- X? __________________________________ -----X? X?----------------~----------

Corals: · Alveolites sp _______ ----X---- ___________ X _________ X ________ -------------------X------- X ----X 

i~f~~~;~;~~r~~~=== ==== == ==== ==== ==== === === -x_- === === === == === === == === === === === == === == === ==== ==== ==== == 

~~!:r:::z~~u;:: s~--~= ==== == ==== ==== ==== -x.- === === x? === === == === === == === === === === == === == === ==== ==== ==== == Chonophyllum sp. 

cf. C. infundiZ?~~~::rp~~;.~=== Macgeea sp ____________________________________________ ==== == =~= ==== ==== === === === ~~~ ~~~ ~; ~ X === ____________________ === == === === === === == ------- === ~ ~~~ X? X? ==== -~-X X -~- --== 

~~~~t~:;~l~;- Phacellophyllum ~~=== -~- ~ ==== ==== ==== === === === === === === == === === == === === === === == === == === ==== ~ ==== == sp _______________________________ X X ___________________ --- -----X --- ---- --------X 

Phaceloid coral species indet ____________________________________________________________________________ - _--- ---- --

Ramose favositoid coral ___________________________________________________________________________ -- ___ --------------

i~~~f.i:i~~~;;: =::: ~ ::=: :::= :::: ::: ::: ::: ::: :=: :=: :: ::: ==: :: ::: ::: ::: :=: :: ::: ~ ::: :::: :~:?: :::: :: 

Tabulophyllum sp___ ____ __ X X ____ X ___ X? X ___ X __ X ______________ --- -- --- -- X ---- X ---- --

f~::.~:o~~J~~~;,i: ==== ~ ==== ==== ==== === -~- === === === === == === -x_- == === === === === == === ~ === ==== ==== ==== == Gastropods: Murchisonia sp ________________ _________________________________ -- --- --- --- --- -- --- -- --- ---- ---- ---- --

Bellerophontid gas- tropod (small) ___________________________________________________________________ -- ___ --------------

Platyceratid gastro- pod, indet _______________________________________________________________________ - ____ - _- ---- ---- --
34 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

TABLE -3.-Fauna of the 

Unit (pl 1.) _____ . ______ Member Member b Member c, lower part 

a 

Age ____ .:._____________ Middle Middle Devonian 

. - Devonian or Late Devonian 

Late Devonian 

Faunalzone __________ ? 8? 8? or 9 9 9? 9 9? ? 9 10? 10 

---------- -

Field No.; U.S. ;..-.,.tO 

A~ 6'~ 6'~ St; Geol. Survey ~ C'l ~ C'r.l a> tO 00 OOC'I C'r.l "<tt OOC'I o;,OOC'I 0 "<tt 00 rLlC'I a> tO ...-1 t- tO 0 ...-1 0 0 

colln. number in 00 0 C'r.l C'1 C'1 t- C'r.l C'r.l C'r.l t- lA a> a> ~A ~~A 00 00 a> ~A t- 0 00 C'r.l ~ 00 a> C'l tO "<tt ~ t- C'1 "<tt C'r.l ~ ~ "<tt C'r.l C'r.lo;, C'r.l C'r.l "<tt "<tt C'r.l C'r.l lO "<tt ~ C'r.l C'r.l C'r.l "<tt "<tt parentheses ______ A A A A A" A A A A A ~~ A A a;, a> Aoo:> A A A oo:> t-~ 00~ 00~ A q A A A A A A A 00 00 00 a> 0 0 0 0 0 0 e 0 0 e ~~ 0 0 0 e 0 0 0 0 0 0 0 0 0 lO lO ~ ~ tO tO tO tO ~ tO <:.0 tO ~..._, tO tO tO tO tO tO tO tO tO tO tO tO 

---------1---------------------· --· - --·-. --------------·--

Gastropod indet. 

(high and medium . . spired) ____________ . ____ -·-- ____________ ____________________ --.--.-- ____ _ ________ ____ :.. ________________ _ 

Gastropod indet. . (small, high spired) ____________________ X"-- _________ ---~ ___________________________________ --------- Gastropod indet _ _..___ __ ___ ___ ___ ___ __ __ __ __ __ ___ _ __ __ _ ____ ___ ___ ___ ___ __ X _________________________ _ 

Others: 

Pelecypod indet. _ 

Styliolina Te~r:~:t{i;s-;;~~=== ___________= == __ === X ---

=== --=== - === 

--- == ________ == == == == -- ==== ________________ == === ==== === === --- === ___ ---

=== == 

__ ----

==== ---=== ---=== ----~- == 

-- ---

=== -x- --- ---=== ---=== ---==: 

Stictostroma sp ______________________ ____________ :-- _______ X? ___ --..., __________________________________ _ 

Stromotoporoidindet ________ --"- ___ X ______ __ _______________ ________________________________ _______ ---

~~~~~~ . zoans, indet ____ ;., __________________________ ----. __________________________________ · __ _ :.. ___ ---. ______ ---

Echinoderm debris ___ X ____________________ -- ___________________________ ---- --- --- --- -- --- --- --- --- ---: · 

1 Either one or the other coral present. 

Shale is most common in the · upper part of the 

formation. It is generally a dark-gray to olive-gray 

noncalcareous silty clay shale that breaks into very 

thin hard plates or fissile chips and is faintly ·color 

laminated. In one place the soil formed on the shale 

swells when wet. A few beds 1-2.5 inches thick of 

argillite having a dull to semivitreous luster are scattered in the. upper part of the formation. Near the 

top there are also some pale-red to moderate-red siltstone and quartzite beds as much as 3 inches thick, 

and here some of the shale is calcareous. One typical 

siltstone bed high in the Pilot Shale has a grain size 

of 0.02-0.04 mm. Most of the grains are subangular 

to subrounded quartz and calcite but include some 

iron oxide, chlorite, tourmaline, and a hydrocarbon. 

The fairly abundant cement consists of calcite, clay, 

and iron oxide. 

Semiquantitative spectrographic analyses were made 

of five samples of Pilot Shale for comparison of their 

trace-element content (table 5) with that of the Chainman Shale. Sample 23 is a platy, fissile, paper shale 

from near the middle of the formation, sample 24 a 

slightly silty shale from its upper part, and sample 25 

a silty shale about 50 feet above its base. Sample 26 

is a black thin, platy, paper shale having a little 

argillite; it was taken from three outcrops within a 

stratigraphic range of 10 feet near the middle of the 

formation. Sample 27 is from a blocky shale about 

80 feet from its top. . 

The thickness of the formation has been scaled from 

several structure sections, because the ·. exposures al,'e 

too poor to make direct measurements very meaningful. Where not obviously faulted, the formation 

ranges in . thickness from 320 to 480 feet; about half 

of the scaled estimates are at 400 feet, which seems a 

reasonable average for the area. 

No fossils have been found in the Pilot Shale within 

the Connors Pass quadrangle, but there the age of the 
MISSISSIPPIAN SYSTEM 

Guilmette Formation___:_Continued 

Unit (pl 1.) _________ _ 

Member 

c, Member c, upper part Member d, 

mid- upper part 

dle 

part 

Age _________________ Late Devonian 

Faunal zone _________ 10 10 10? 10 ? 10 10 10? 10 

Field No.; U.S. 6~ 6~ 6i2 6~ 6.-1 6~ 6~ Geol. Survey W.r;f'J ~ W.c-:~ W.c-:~ w.~ 0 .-I 00 0 1:'- C'l .-I C'l Cf'J Ol 0 Cf'J C'l ~ l.C C'l l.C 0 w.~ W.c-:~ W.c-:~ Cf'J 

colin. number in IQ Ol J;Q IQ IQ 0 0 00 0 Cf'J 00 00 00 0 0 .-I 00 0 ~ ~ ~ l.C ~ IQ IQ .1Q ~ 

~Ol Cf'J l.C~ 2:€0':> "<t4 "<t4 Cf'J Cf'J "<t4 "<t4 Cf'J Cf'J "<t4 l.C l.C Cf'J "<t4 Cf'J "<t4 "<t4 Cf'J C'l 00~ ~~ C'l 

par en theses ______ Q Ol~ 

~l.C Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q Q ~l.C ~lO .-!Ol Q ool.C t--l.C OOlO ool.C 

e 0 e e e 0 0 0 ~ 0 0 0 0 0 0 0 0 0 0 0 0 0 ~ e e e C) 

~ ~ ~ ~ lO ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ l.C l.C 

1---------1---------· -------------------------------

Gastropod indet. 

(high and 

medium spired) __________________________ X _________________________________ ----------------------

Gastropod indet. 

(s:r;nall, high . spired)__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ____________ _ 

Gastropod indet ________________ ________________________________ --' ______________ --- -- --- ---- ---- X --

Others: 

Pelecypod indet. 

'£~fft~~-~:~~~==== :=:: :: :::: :::: =::: =:: :=: :~: ::: ::: ::: :: ::: :=: :: :=: ::: :=: ::: :: ::: :: ::: :::: :::: :::: :: 

Stictostroma sp ______________________________________________ . ___________________ ----------------------

Stromotoporoid · · indet ______ .,. __________________________________ X _.:. ______________ :_ _______________ --- _· ___ X ------

Fenestrate bryozoans, indet ______________________________________________ X ___________ --- ----- ----- ---- ----------

Echinoderm debris _______________ ~--- ____________ ~-- _____ X _________________ -- --- ~- --- ---- ---- ---- --

formation is bracketed between the early or middle 

Late Devonian age of the underlying Guilmette Formation and the Early Mississippian age of the overlying Joana Limestone. Some fossils of Late Devonian 

and others of Early Mississippian age have been found 

in the Pilot Shale in many nearby stratigraphic sections, and at several outcrops there is an uneonformity 

within the formation or at its base. 

The Pilot Shale is probably a finer grained facies of 

the predominantly argillaceous and quartzitic units in 

the lower part of the Eleana Formation (Poole and 

others, 1961) , which was deposited near ·another high 

area about 150 miles to the southwest. During latest 

Devonian time, currents carried silt over a large area 

and very little calcium carbonate was deposited. 

Slightly finer material, perhaps winnowed out of the 

coarser clastic material deposited near the orogenic 

centers, continued to be. deposited during earliest 

Mississippian time. 

MISSISSIPPIAN SYSTEM 

JOANA LIMESTONE 

The Joana Limestone is a thick-bedded to massive 

crinoidal limestone 300-500 feet thick that conformably overlies the Pilot Shale. This formation was 

named the Joana Limestone by Speneer (1917), for 

the Joana mine a few miles west of Ely. 

The Joana Limestone underlies about 3--4 square 

miles in the Connors Pass quadrangle; it occurs chiefly 

in the western half of the quadrangle but also in a 

small· area at an altitude of -about 7,600-8,000 feet that 

is west of Cleve Creek. It generally forms small 

rugged knobs, ridges, and cliffs that contrast markedly 

with the gentle slopes formed by the aO.jaeent shale 

formations. Where the underlying shale has been 

deeply eroded, as along Cave Creek and Steptoe Creek, 

the cliffy outcrop is emphasized; there many cliffs 

overhang, making caves and natural shelters along 

their bases. Gentle dip slopes on the limestone are 
36 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

largely stripped bare of colluvium and are interrupted 

by large rounded ledges having strongly pitted and 

fluted surfaces. The middle and upper parts of the 

formation contain limestone layers that weather to 

narrow regular ledges and slabby debris. 

Typical outcrops of the formation are most accessible at the junction of Cave Creek and Steptoe Creek. 

A more complete and unfaulted section is moderately 

well exposed 1-2 miles south of Cave Creek, and a 

thick section of the limestone may he seen on the west 

side of the upper part of Cooper Wash. 

Much of the Joana Limestone is medium gray, thick 

bedded, bioclastic, crinoidal, and slightly cherty. The 

base of the formation is well exposed on the south 

side of Square Top Hill along Steptoe Creek and on 

the ridge about 1.5 miles N. 10° W. of the peak containing Taylor bench mark. Despite the slightly limy 

top of the Pilot Shale and the platy bedding at the 

base of the Joana Limestone, the contact is sharp. 

South of Cave Creek, where it is most fully exposed, 

the formation consists of five units, consisting alternately of platy and massive limestone. The lowest 

unit consists of only 15-20 feet of platy limestone. 

The basal beds of this unit are rarely more than 4 

inches thick, and are partly nodular, are generally 

bioclastic, and in places contain brachiopods and horn 

corals. In the Cave Creek area a zone 10 feet thick 

contains rubundant long lenses and beds of chert. 

Above the basal platy unit there is the lower massive 

limestone, about 200 feet thick, which contains scattered pods of dark-gray chert and scraps of fossils; 

this unit varies considerably in thickness, possibly 

because it is indistinguishable from the upper massive 

unit where the middle platy limestone is absent. The 

middle unit, 30-50 feet thick, consists of bioclastic 

silty platy limestone in beds 0.5-4 inches thick. The 

beds become thicker upward, and the middle unit 

grades into the upper massive limestone unit, about 

150 feet thick, but less conspicuous and perhaps less 

extensive than the lower niassive unit. At one outcrop, half a mile northeast of hill 9,085, rocks of the 

upper massive limestone unit contain abundant coral 

fragments and some colonial coral masses that resemble 

biostromal st:r~uctures. The upper platy unit is about 

60 feet thick and resembles the middle one. The beds 

are generally thinner toward the top of the upper 

platy unit, and they locally contain scour channels 

and "IDinor unconformities. The unit contains much 

calcarenite rich in crinoid debris and some calcilutite. 

In some places where the Joana is thin but not obviously faulted, not all of these units can be recognized, 

possibly because obscure bedding-plane faults are more 

widespread in the formation than has been supposed, 

or because the lithology differs laterally, or because the 

upper contact is an unconformity that cuts out some 

of the units. 

Where the Joana Limestone seems to be most complete, it is at least 480 feet thick, as scaled from several 

structure sections. Near Steptoe Creek and Cave 

Creek, however, where neither of the contacts is obviously faulted, there is only rubout 300-400 feet of this 

limestone. On the east . side of the upper part of 

Cooper Wash, there is only 100-200 feet of Joana, 

again without obvious faults along the contacts. A 

similar thinning of Cambrian formations in this area 

was explained structurally, but the structural features 

are locally exposed near the Cambrian formations; 

whereas the Joana Limestone also thins in outcrops 

northwest of the quadrangle that are clearly unfaulted. 

Provisionally, then, most of the contacts of the Joana 

Limestone, even where it is thin, are mapped as normal 

stratigraphic contacts, on the assumption that the 

initial thickness of the formation differed widely. 

Fossil fragments and single fossils· are abundant in 

the formation, but assemblages of unbroken fossils are 

only moderately common in the platy limestone units 

and are scarce in the massive limestone units. All 

fossils identified from the Joana are listed in table 4. 

TABLE 4.-Fauna of Joana Limestone 

[Identified by Helen Duncan and MacKenzie Gordon, Jr. (written commun., 1962, 

1963), and J. T. Dutro, Jr. (written commun., 1961)] 

<0 >0 

~ .... ;1; 0> C'l C'l ~ 0 CQ Field No _____________________________ o C'l CQ CQ 

Q ~ ~ ~ ~ ~ ""' 00 ~ ~ ~ 0> 0 0 >0 >0 <0 <0 

--------T -- 0 0 0 0 0 p.., p.., p.., p.., p.., U.S. Geol. Survey loc ________________ J, cb ~ ~ J, 

>0 

~ ~ ~ C'l 

C'l ~ ~ C'l ~ 

------------

Brachiopods: . X 

ISi~i~~~~I~~~~~i~::::::: Eumetria cf. E. verneuiliana ~~~~== ::~:= ~~~~~~ ~~~~:: --~-~ ::~:: ==~=~~ 

Productoid M~~~~f!If~ff~i~~~i~~~~~======= brachiopod cf. Mar- ====== ==~== ==~== ====== ~~~~~ ====== ====== 

sf~'tz~~~:Jt~i~~~fnd.et:========== ====== ~ ====== ====== ====== ====== ====== Spirifer cf. S. centronatus ______ X ___________ _ 

sprr~~e;~~~-illdet================= Strophomenoid brachiopod ~ --~-- ~ (highly inflated form) __________ ------ ------ X ------ ------ ------ ------ Strophomenoid brachiopod in deL X X ------ ------ ------ ------ ------

Coc~~!i~~:~~~~~~~~::~~=~ ):: :::::: ~=~=:~ ;;~;; --~ ===~~~ :;~;; Others: . X 

~~~~~~~r~.t~:~~ ::~~~: ;;~;; :~~::: :~~~~ ~~~-~ -=_==~ -~=~~~ 
MISSISSIPPIAN SYSTEM 37 

Most of the fossils were collected to aid in solution of 

local structural problems and came from undetermined 

stratigraphic horizons; USGS colln. 21236-PC, however, is from the basal 12 feet of the formation, and 

USGS collns. 21235-PC and 21258-PC, collected a few 

hundred feet -apart, are probably from the middle 

platy limestone unit. Most of the collections are 

assigned an Early Mississippian age, but some are not 

sufficiently diagnostic for so specific an assignment. 

The widespread and relatively uniform bioclastic 

lithology of the Joana Limestone indicates a general 

return of the quiet conditions of deposition that prevailed during much of middle Paleozoic time. Within 

the Connors Pass quadrangle there are abundant signs 

of current activity and some evidence of small reefs. 

Only in the Cherry Creek Range, 60 miles northwest 

of the quadrangle (Langenheim, 1960), where the 

formation is very thin or absent, is there any suggestion of continued crustal instability; however, Langenheim did not mention any bedding-plane faults. In 

the Silver Island Range (Schaeffer and Anderson, 

1960) , 120 miles north of the quadrangle, the Joana 

Limestone rests unconformably on the Guilmette 

Formation. 

CHAINMAN SHALE 

The Chainman Shale, a dark-gray shale about 1,100 

feet thick, conformably overlies the Joana Limestone. 

Spencer (1917) named this formation the Chainman 

Shale for exposures near the Chainman mine, a few 

miles west of Ely. The formation consists of weak 

rocks and therefore generally forms benches and 

valleys. It is widely known for its characteristic 

fauna of pelecypods and cephalopods. Many geologists have described the formation in specific localities, 

but it has not yet been comprehensively studied. 

The Chainman Shale underlies almost 10 square 

miles in the western half of the quadrangle. It occurs 

chiefly in an area lying between Tamberlaine Canyon, 

the head of Cooper Canyon, and the southwestern 

corner of the quadrangle, but also in small areas 

northeast of Cave Creek, east of the crest of the Schell 

Creek Range along the southern edge of the quadrangle, and west of the North Fork of Cleve Creek. 

Particularly noteworthy in the distribution pattern of 

the shale is the fact that the basal contact is more 

irregular than the upper contact. 

The formation underlies most of the broader benches 

and larger basins in the area. Slopes eroded on it are 

usually very gentle, except where they are cut by 

young gullies or· are immediately beneath the Ely 

Limestone. In many places they are veneered with 

Tertiary and Quaternary gravels or conglomerates, 

this cover showing that the formation has underlain 

low areas for a long period of time. Some of these 

gentle slopes are interrupted by one or more small 

ridges or alined small knolls consisting of sandstone 

and quartzite interbedded with the shale, and fragments of these resistant rocks mantle the shale over 

large areas. A characteristically irregular, hummocky, slump topography is formed on the shale and 

is represented on the map (pl. 1) by an overprint 

symbol. 

The Chainman is nowhere sufficiently well exposed 

to provide a basis for anything more than a general 

outline of its stratigraphy. Some exposures of its 

upper part can readily be seen in cuts along U.S. 

Highway 6-50-93 about a mile west of Connors Pass. 

Exposures of rocks low in the formation are most 

accessible at the dam of Cave Creek Reservoir and at 

a place about three-quarters of a mile farther east, 

on the west side of the valley tributary to Cave Creek 

from the south. Rocks in the middle and upper parts 

of the formation are conveniently exposed in Cooper 

Canyon a few hundred yards south of the head of the 

rough narrow road running south from the corral in 

the center of the basin centering in sec. 35, T. 15 N., 

R. 65 W., and also along the northwest side of the 

small volcanic plug near the road on the east side of 

the same basin. 

The Chainman consists chiefly of dark-gray noncalcareous highly carbonaceous clay shale, but contain a small amount of coarser clastic rocks. Its base 

appears to be fairly sharp, but it is everywhere 

slumped or covered. The formation is roughly divisible into a lower shale and siltstone unit probably 200-

400 feet thick, a middle shale unit at least 500 feet 

thick that contains few sandstone beds, and an upper 

shale unit about 300 feet thick that contains numerous small lenses of sandstone and quartzite and a little limestone. These units, however, are so broadly 

gradational and so much disturbed by landslides that 

they are not mappable. 

Siltstone and mudstone are interbedded with the 

shale near the base of the formation, and some layers 

of silty rock are several tens of feet thick. The beds 

in the lower shale and siltstone unit are commonly 

lj2-12 inches thick, have a roughly conchoidal fracture, and weather to irregular blocky slabs. Some of 

the siltstone is slightly micaceous and weathers pale 

yellow brown. The shale interbedded with it c?ntains small carbonaceous nodules, a few of whiCh 

have pyrite cores. Rocks in the upper part of this 

unit or near the base of the overlying middle shale 

unit contain a few cephalopods. 
38 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

In many places near the middle of the Chainman, 

there are a few selenite veins. A lenticular marker 

bed of sandstone and ·quartzite about 50 feet thick 

appears near the middle of the formation in several 

places, such as on the high bench northeast of the 

Taylor mining district. This rock is moderately thick 

bedded and weathers to a pale-yellowish-brown blocky 

rubble. 

Sandstone and quartzit-e in groups of beds a few 

feet to 10 feet thick are most common in the upper 

shale unit of the Chainman Shale, but even there they 

do not exceed 5 percent of the rock. In most places 

there are three to six such groups of beds, and the 

more prominent and extensive groups are locally 

mapped as markers. They are not extensive, probably 

having been deposited as lenses and some of them possibly having been pinched off by faulting and folding. These beds are commonly light gray, greenish 

gray, or pale yellowish gray on fresh fractures, and 

they weather brownish gray or olive gray. The 

sandstone beds are 1-22 inches thick but are most 

commonly about 4 inches thick. Faint laminae within 

them show crossbedding, and many surfaces have ripple marks, chiefly of current ripples. In thin section 

Sample loc. (fig. 14) _ 23 

Field No __ --------- 59D254 

Lab. No____________ 50888 

Formation __ -------

24 

60D357 

5090S 

Analyst_ ___________ E. F. Cooley 1 

Si_ ----------------- 15 10 

·AL ----------------- ------------ Fe __ ---------------

_____ 2 ______ 3 Mg __ --------------- >5 >5 Ca __ --------------- ------------ ------------ Na ----------------- ------------ ------------ TL K_ -----------------

_________________ ------------ ------------ .3 .3 

Mn p- -----------------__ ________ _______ ------------ ------------ • 05 .1 

Ag-- --------------- <. 0001 <· 0001 B-- ---------------- . 005 . 005 Ba __ --------------- . 03 . 05 Be __ --------------- <. 0001 <. 0001 Co_---------------- <.001 . 001 

Cr ------------------ . 005 . 01 Cu __ --------------- . 005 .003 Ga __ --------------- <.002 <.002 La _________________ <.005 <.005 LL _________________ Mo _________________ ----<:ooo5- ----<:ooo5-

Nb _________________ NL ------------ _________________ . 002 ------:000-- Pb __ --------------- .002 .002 Sb __________________ 0 0 Sc __________________ <.001 . 001 Sr __________________ .02 .03 

v------------------ .005 .007 y------------------ .002 . 002 Yb_---------------- ----<:02 ___ ----<:02 ___ Zn __ --------------- Zr ____________ · ______ . 01 .007 

25 

61D647 

61-2972 

Pilot Shale 

26 

61D649 

61-2973 61D650 

61-2974 

J. C. Hamilton 2 

7 >10 >10 3 3 3 . 7 .7 . 7 7 7 1.5 >10 >10 . 7 .3 .15 . 07 3 3 3 . 07 . 07 .15 0 0 0 . 03 . 015 . 015 0 0 0 . 003 . 003 . 007 . 03 • 015 . 03 0 0 . 00015 0 0 . 0007 . 0015 . 003 . 003 :0015 . 003 .007 .0003 .0003 . 0003 0 0 0 0 0 0 0 0 . 003 0 0 0 .0007 . 0015 . 015 0 0 . 0015 0 0 0 .0007 .0007 . 0007 . 015 . 007 .03 .003 .003 . 015 . 0015 0 . 0015 . 00015 . 00015 . 00015 0 0 0 .007 . 003 . 007 

the diameters of the grains are seen to range from 

0.05 to 0.5 mm and average about 0.1 mm. The 

grains are well sorted and alined, and most of them 

are subangular to subrounded, but some well-rounded 

and secondarily enlarged quart-z grains are mmally 

present. 

Quartz grains make up 80-95 percent of the sandstone and quartzite. Other constituents are chert, 

iron oxide, leucoxene, zircon, apatite (as inclusions in 

quartz), tourmaline, muscovite, plagioclase (of intermediate An content), and in a few specimens possibly 

also pyroxene, sphene, and rutile. The quartz grains 

interlock or are closely packed, and the cementing 

material consists of clay and iron oxide, quartz, chalcedony, or calcite. One typical quartzite sample contains 15 percent by weight of soluble and clay -sized 

material and 0.3 percent of heavy minerals, of which 

zircon, leucoxene, and tourmaline of several varieties, 

including schorlite, each make up 25-30 percent; very 

small amounts of muscovite and oligoclase are attached to the tourmaline. These quartzite and sandstone beds are finer grained than those in member b 

of the Guilmette Formation and in older rocks, and 

TABLE 5.-Semiquantitative 

[Italic type indicates anomalously high values; __ ,not looked for; 0, looked for but 

28 

59D165 

50878 

29 

60D353 

5089S 

30 

60D440 

5091S 

31 

61D569 

61-2955 

32 

61D572 

61-2956 

33 

61D577 . 61~2957 

Chainman Shale 

E. F. Cooley 1 J. C. Hamilton 2 

7 20 30 >10 >10 >10 _____ 3 ______ 7 7 7 ------------ _ ____ 3 ______ 7 1. 5 1.5 2 1 >5 1 1.5 7 1.5 

------------ .7 7 .3 ------------ ------------ ------------ .3 .3 .3 ------------ ------------ 1.5 3 1.5 ------------ ------------ .3 . 7 ------:7 ____ .3 .3 .3 

0 0 0 ------:o3 ___ ------:o7 ___ ---J--:oi ___ .15 .03 . 03 

.002 <. 0001 . 0001 0 0 0 

,01 .01 .01 . 003 . 007 . 007 

.01 .03 . 07 . 015 . 07 • 015 

. 0001 .0001 . 0001 . 00015 0 . 00015 

<.001 <.001 . 001 . 0015 .0007 .0015 

.1 .007 . 015 . 015 . 007 .015 

.02 .005 . 015 . 003 .003 .003 

<. 002 <.002 <.002 . 0015 .0007 . 003 

<. 005 <.005 <. 005 0 0 .003 

0 0 .03 ------------ ------------ ------------ .0007 .0007 0 . 005 <. 0005 . 001 0 0 . 0015 ------------ ------------ ------------ . 01 . 005 . 007 .003 .ooa .007 

.003 .002 .002 .0015 0 . 003 

0 0 0 0 0 0 

. 001 .001 .001 .0015 .0007 . 0015 

.05 .01 .005 .03 .03 .03 

.1 .007 . 01 .007 .007 .015 

. 01 .005 .003 .0015 .0015 .003 

----- -- -- .0003 • 00015 .0003 ------------ ------------ .2 <.02 <.02 0 0 0 

. 01 .03 .02 . 015 . 015 .015 

34 

61Y595 

61-2958 

>10 3 

.7 

7 

7 

.15 

3 

. 07 0 

• 03 0 

• 003 

.03 

0 

0 

.003 

.003 

0 

0 

0 

0 

0 

. 0015 0 

0 

. 0007 

.015 

.0015 

0 

. 00015 

0 

.003 

1 Analyses reprted in percent. Elements looked for but not found (in parts per million): As <1000, Bi <10, Cd <50, Ga <20, Ge <20, In <50, Nb <50, Sb <200, Sn <10, Ta <50, Ti <100, and W <50. 2 An!Jolyses reported to nearest numbers in the series 7, 3, 1.5, 0. 7, 0.3, 0.15, and so forth, m percent. These numbers are midpoints of group data on a geometric scale, 

and the groups contain the quantitative value for about 60 percent of the analy~s Elements also looked for but not found: As, Au, Bi, Cd, Ce, Dy, ~~r, ~~ ~d, T~' Hf, Hg, Ho, In, lr, Lu, Nd, Os, Pd, Pr, Pt, Re, Rh, Ru, Sn, Sm, 1a, , . e, 

Tl, Tm, U, and W. 
MISSISSIPPIAN SYSTEM 39 

their grains are more angular and contain more material other than quartz. 

Some of the shale in the upper unit contains limy 

nodules and mudstone beds having an abundant fauna 

of gastropods, pelecypods, and goniatites. This upper shale unit also contains some thin beds of argillite and, in its uppern1ost 50-100 feet, some lenses of 

grit and of conglomerate associated with a small 

amount of greenish-gray quartzite. The conglomerate contains pebbles of limestone and siliceous material. Just above the quartzite there is generally a 

little limestone or coquina containing abundant silicified brachiopods and corals that weather out and 

cover the slope. Near the northwest side of the small 

intrusive body along Cooper Canyon, in sec. 36, limestone containing the silicified fossils is interbedded with 

black shale containing the pelecypod-goniatite fauna; 

rocks of intermediate lithology have a mixed fauna. 

The uppermost 40-60 feet of the upper unit contains beds that grade into the overlying Ely Limestone. Brownish-gray sandy and bioclastic limestone 

beds, making up 25-50 percent of the material, alternate with -beds of dark-gray shale. A few of the 

more limy beds contain chert nodules. The. top of 

spectrographic analyses of black shale 

not found; >,greater than; <,less than; d, detected but concentration uncertain] 

35 36 37 38 39 40 41 

61Y596 61Y597 61Y598 61Y599 61D602 61D605 61D608 61-2959 61-2960 61-2961 61-2962 61-2963 61-2964 61-2965 

the Chainman is most conveniently placed at the base 

of the lowest thick bed of cherty limestone,· a contact that can almost everywhere be located on the 

map within 200 feet, and usually within 50 feet. I 

suspect, however, that the contact would coincide 

more closely with the systemic boundary if it ·were 

placed at the top of the highest black shale bed, a 

less convenient horizon slightly higher in the section. 

The trace-elements contents of 21 samples were 

semiquantitatively analyzed by spectrographic methods (table 5). Sample 28 contained 20 times as much 

zinc, chromium, vanadium, and silver as other samples, and minor anomalies were found in other samples. This cursory study showed no apparent . relation between the distribution of the trace elements and 

the areal or stratigraphic position of the sample or 

the distance of the sample from mineralized areas, 

intrusives, or major structures. 

Much of the Ohainman Shale is unfossiliferous, but 

at a few horizons it is abundantly fossiliferous. In 

some places the dark-gray shale contains a rich and 

well-preserved fauna of pelecypods, gastropods, and 

goniatites, and the limier beds contain some corals 

and brachiopods. Collections from the shale, includ42 43 44 45 46 47 48 

61D609 61D610 61D624 61D626 61D628 61D629 61D703 

61-2966 61-2967 61-2968 61-2969 61-2970 61-2971 61-2975 

Chainman Shale-Continued 

J. C. Hamilton-Continued 2 

>10 7 7 >10 . >10 >10 7 >10 >10 >10 >10 >10 >10 >10 3 1.5 3 3 >10 3 7 >10 7 3 7 7 3 3 

. 7 . 7 . 7 1.5 1.5 1.5 . 7 1.5 3 1.5 3 7 1. 5 1.5 

7 3 7 7 1.5 . 7 1.5 1.5 1.5 3 1.5 1.5 7 .7 

>10 >10 >10 >10 . 7 7 7 . 3 . 7 7 .3 .7 7 1.5 

.15 .15 .3 .15 . 3 . 3 . 3 . 3 .3 . 3 . 3 .3 . 3 .7 

3 1. 5 3 3 3 3 . 7 3 3 3 3 .7 3 1.5 

.3 • 07 .15 . 07 . 7 .15 .15 .3 .3 .15 . 3 .3 .15 .3 

0 0 0 0 0 0 1.5 0 0 0 0 0 0 .7 

• 03 . 015 . 03 . 03 . 007 . 007 . 007 . 015 . 07 . 015 . 07 . 3 .03 . 007 

0 0 0 0 . 00015 0 . 00015 0 0 0 0 0 0 0 . 003 0 . 003 . 003 . 007 . 007 . 007 . 007 . 007 . 007 . 007 • 007 . 003 . 007 

• 015 . 015 . 03 . 007 . 015 . 007 . 007 . 015 . 015 . 015 . 03 .007 • 015 • 03 

0 0 0 0 . 0003 . 00015 0 . 00015 . 0003 0 . 00015 • 00015 0 0 

.0007 0 0 0 . 0007 0 0 . 0015 . 003 0 . 0015 . 0007 • 007 0 

.015 . 015 . 007 . 003 . 015 . 015 .015 .015 . 015 . 015 . 015 . 007 . 003 . 015 

. 0015 . 003 . 0015 . 003 . 0003 . 003 . 003 . 003 . 003 . 003 . 003 . 003 . 003 . 003 

. 0003 0 . 0007 . 0003 . 003 . 0015 . 0007 . 003 . 0015 . 0007 . 0015 . 0015 . 0007 0 

0 0 0 0 . 007 0 0 . 003 . 003 0 . 003 0 0 . 003 

0 0 0 0 . 03 0 0 . 03 . 03 0 0 0 0 0 

0 0 0 0 0 . 0007 . 0007 c . 0007 0 . 0015 . 0007 0 0 

0 0 0 0 . 0015 0 0 c 0 0 0 0 c 0 

. 007 .003 . 0015 . 0015 . 007 . 007 . 007 . 007 . 007 . 003 . 007 . 003 . 003 . 003 

0 0 0 . 0015 0 0 0 .003 . 003 0 . 003 . 003 0 0 

0 0 0 0 0 0 0 0 0 0 0 .07 0 0 . 0007 0 . 0007 . 0007 . 003 . 0015 . 0007 . 0015 . 0015 . 0007 . 0015 . 0015 . 0007 . 0007 

. 03 . 07 . 03 . 07 . 03 . 03 . 07 . 03 . 03 • 03 . 03 . 03 . 007 . 015 

. 007 . 007 . 003 . 003 .015 . 007 . 015 .015 .015 . 007 . 03 . 007 . 007 . 007 

. 0015 . 0015 . 0015 . 0015 . 003 . 003 .003 . 003 . 003 . 0015 . 003 . 003 . 0015 • 003 

. 00015 . 00015 . 00015 . 00015 . 0003 . 0003 . 0003 . 0003 . 0003 . 0003 . 0003 . 0003 . 00015 . 0003 

0 0 0 0 0 d . 03 0 0 0 0 0 0 0 . 015 . 007 . 015 . 007 . 015 .015 . 003 . 007 . 015 .015 .015 . 015 . 007 . 015 
40 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

ing one, field No. 200, made in 1957 by Mackenzie 

Gordon, Jr., R. K. Hose, C. A. Repenning, and H. R. 

Christner, contains about 550 specimens; the fauna 

are listed in table 6. W. L. Youngquist (1949, p. 278-

279) previously reported on another collection from 

the Connors Pass quadrangle. 

The collections are all of Late Mississippian age 

and range from the Goniatites gTanosU8 zone to the 

upper part of the EwmOTphoceT(U; bisuleatwm zone. 

Gordon thought possibly some of the basal beds of 

the formation are missing in this area, inasmuch as 

fossils of an older zone in nearby stratigraphic sections have not been found here, and the Goniatites 

gTanostts zone is here only about 300-500 feet above 

the base of the formation instead of considerably 

higher as it is in other areas. 

The Chainman Shale occurs throughout the Schell 

Creek Range and adjacent ranges, and some of its 

lithologies reflect more distant orogenic events. The 

sandstone, quartzite, and conglomerate lenses of the 

Chainman Shale in the Connors Pass quadrangle are 

inferred to be the thin extremities of tongues of the 

Diamond Peak Formation, which was derived from 

the west (Nolan and others, 1956), or its correlative, 

the Scotty Wash Quartzite; inasmuch as some of the 

conglomerate contains siliceous pebbles, it also was 

probably derived at least in part from the west. 

TABLE 6.-Fauna of the Chainman Shale 

[Identified by Mackenzie Gordon, Jr. (written commnn., 1961, 1963), Gordon and Helen Duncan (written commun., 1962)] 

Faunal wne _________________________________ _ Goniatites 

granosus 

Unit__________________________________________ Lower shale and 

siltstone 

Middle 

shale 

Eumorphoceras bisulcatum 

Upper shale 

---- 1---;-----;-·------;·---,-----,-----.---- ------------------

0 0 0 0 0 0 0 0 ll; ll; ll; ll; ll; ll; ll; ll; I 

@ 

J, .,!. 

0 @ 

J, 

@ 

J, d. C'-1 ~ ~ 

~ Q(l 00 E 00 

~ ~ ~ ~ ~ ~ 

0 0 0 0 0 0 0 0 0 

U.S. Geol. ll; il< il< il< il< il< il< il< il< Survey loc ________________________ J, J, 6 tL ~ d. I I C'-1 .b ~ 00 00 @ 00 00 

~ ~ 0> 0> o:> 0> o:> 

~ ~ ~ ~ ~ ~ ~ 

------------ -- ---- --- --------- - ------ ,.._ 0 ,.._ 0 00 C'-1 ..... "' o:> "' ..... <:0 C'l ,.._ 00 0 ~ ~ C'l C'l 0 ~ <:0 ..... . 0> 0 "' "' "' 00 0 <:0 <:0 <:0 C'l 

"' "' <:0 C'l C'l <:0 <:0 ,.._ "' "' "' <:0 s "' s s C'l Field No ___ --------------------- ______ _______ e ~ ~ "' ~ ~ ~ e e e ~ ~ ~ ~ ~ ~ ~ 0> 0> 0> 0 0> 0> 0> 0> 00 ~ 0> 0> 0> 0> 0> tQ <:0 <:0 tQ <:0 <:0 <:0 tQ tQ tQ tQ tQ tQ tQ tQ tQ tQ tQ 

---------- ------------ ---- --------

Brachiopods: Chonetes sp_______________________________ ______ ______ ______ ______ ______ ______ X ____________ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Cleiothyridina cf. C. suborbicularis (Hall)____________________________________________________________________ X ------ ------ ------ ------ ------ ------ ------

ge::~~ii~i:;.1~d~t_s_~~~~~e!~~~~-~-~l~~=== Composita ====== ====== ====== ====== ====== ====== ====== ====== ====== ~ ====== ====== ====== --~-- ====== --r- ====== ====== ====== subquadrata (Hall) ______________ ________ __ __ ____ _____________________ ____ ____________ ------ ------------------ X ------ ------ ============--X-- Diaphragmus n. sp. A____________________________________________________________________ X X ______ ------ ------ ------ ------ ------ Flexaria aff. F. arkansana (Girty)_________ ______ ______ ______ ______ ______ ____ __ ______ ______ X ------ ------ ------ ------ ------ ------ --------------X--------

Flexaria sp. indet__________________________ ______ ______ ______ ______ ______ ______ ______ X ______ ------ ----... - ------ ------ ------ ------ ------ ------ Hustedia sp ___________________________________________________________________________________________ ------ ------ ------ X ------ ====== ======--------X--

Inflatia inflata (McChesney) ______ _______ ______ _ ______ ------------------------------------------------------------ ---f-- --X-- --X-- X lnflatia n. sp. A__________________________________________________________________ ________ X X X --------X-- --X--

Inflatia sp. indet_ __ ----------------------- ____________________ _________ _____ __ ____________ ------ ------ X ------ ------ ------ ------ ------ X ___________ _ Kozlowzkia? sp _________________________________________________________________________________ ------ ------ ------ ------ ------ ------ ------ X 

Leiorhynchuscarboniferum Oirty__________ ______ ______ ______ X ______ ? X X X ------ ------ ------ ------ ------ ------ ------ ------ ------ X 

Orbiculoidea fl:Jttf:Ff~~~l~:~~;~~;~=~=~~;~~-===== sp____________________________ ______ 

====== _____====== _ ====== ______ ___====== ___====== _______ ______ ====== ====== _____ _ ====== X ====== ______ ------ ~~~~~ ------ ~~~~~ ====== 

------ ------ ------ ------

====== ====== ==~== --====== ---- ====== ------====== --X-- ====== 

Petrocrania g~~~~!e~~- t~~e~~~e-~~i~-~~~-~~~~~~~~~==== chesterensis (Miller and ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== --x--

Faber)_______________________________________________________________________________________________________________ X ------ ------ ------ ------------

~~~~~~=~;~;}:~?t~~~~~d!~~-~~:-~~-e_s~~~~== ====== ====== ====== ====== ====== ====== ====== ====== --X-- ====== ====== ====== ___ ? ___ --~-- ====== == ==== ====== ====== ====== 

c~II!~ijl~~~~~~)~::: ::;:~; ;:~::: ::::;~ ;~l::; ::;~:: :~:::: :;;;:: il;~:; ;:~~: l!!!l; !!~~: !!~!~ ;:~:; ::~:; ::;::: :;:;;: ::~;; i~~;~ ::~:; ~~~~:~~~~ ::~~= ~!~~~= ~ill~~ ;;~;; ~~~~~ ))~)~!!!~~~! :;~;; ~=~;i ~~!!~= ~~~jj~ ljllll ~l~llj l~jl~l ~)jj)) ~~))jj ~~jjlj j)jj)) ::~=: Neoglyphioceras cloudi utaheme (Miller, 

i~~!~~:~~r:=: ~~~~; j~~~~ ~l~~l ::~:: ;;;;l; ;;~;;; l~~ll ::~:: ;;;;;; ~~ljlj ;;;;;; ;~;-;; ;-l-ll ;-;!;; ;l;;;l :~~!~; ;;j;j; ;;!;;_ ;;~;; See footnote at end of table. 
MISSISSIPPIAN, PENNSYLVANIAN, AND PERMIAN SYSTEMS 41 

TABLE 6.-Fauna of the Chainman Shale-Continued 

(Identified by Mackenzie Gordon, Jr. (written commun., 1961, 1963), Gordon and Helen Duncan (written commun., 1962)] 

Faunal zone _______________________ -- __ ------- Goniatites 

granosus 

Unit__________________________________________ Lower shale and Middle 

siltstone shale 

0 

Pot U.S. Geol. Survey loc ____ ------------------- cb 

~ ·--

!::; 

co Field No ________ ----------------------------- e 

co 

--· 

0 

g 

~ 0 

co 

----- -- r:- ~ 00 co 0> c<l co co 

~ 0> e e lQ co co 

--- ------ -- c<l co 

F2 "" "" "" "" "" "" e A ~ "" "" ~ 0> 0> 0> co lQ lQ lQ 

Eumorphoceras bisulcatum 

Upper shale 

----- ----------------- 00 0> "" """ co c<l r:- 00 8 "" 0 co co co c<l c<l c<l co 0 "" 0 0 c<l "" "" "" c<l 

~ ~ ~ ~ ~ ~ ~ ~ 00 0> 0> 0> ~ 0> 0> 0> 0> lQ lQ lQ lQ lQ lQ lQ lQ 

----------------·--------· ---------------------------- Gastropods: 

Bellerophontid __ ------------------------- ______________________________ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ X 

Gastropod indet (high spired) ________________________ ------ X ______ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Glabrocingulum quadrigatum Sadlick and 

Nielsen_________________________________ ______ ______ ______ X ------ ------ ------ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Glabrocingulum binodosum Sadlick and 

Nielsen _______ ________________ _______ __ ___________________ ------ ------ ------ ------ ______ · ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ X 

Pelecypods: ~~~gfJ~a;~~~=========================== ====== ====== ====== ====== ====== ====== ==~== --~-- ==~== ====== ====== ====== ~~~~~ ====== ====== ====== ====== ====== ==~:: 

t~~l~r~·j:::::::=~~l;~;~~=~;;~~ ;;;=;; ~~=~;; ~~~l;; r ~:~~: =:~== ~~~~~ :r ~~~;~ ~;~;:; ;;:;:: :;:~;; ::;:~; :;~:; ;:~~;; ;;:;:; :~;:); ~;;;;; ;;;;; Polidevcia sp______________________________ ______ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ Posidonia cf. P. wapanuckensis (Girty) _________ ------ ______ X X ------ ------ X ------ ------ ------ ------ ------ ------ ------ ------ ------ ------ ------

~~~:'~~~ss~~=========================== ====== ====== ====== --~-- ====== ====== ====== ~ ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== ====== Others: 

15.~I~~;E~:~;~~;;~=::::::::: Trepostomatous bryozoan indet. (laminar ::===~ :::::: =~~~~~ ~~==~~ =~=~~~ =:~::: :=::: =~==~~ ~~==:: ~~~:=: =:~=- ===~=~ :~=~~= ==~;= =~=~~: =t: ~~:~:: ==~== ::~:: forms) ______________________________________________ ------------------------------------------------ X ------ ------ ------ ------ ------ ------ ------ ------ Trepostomatous bryozoan indet. (ramose 

a~~~~~H2~-;:==~=~===~===~::::= ~~~=~= ~~=~~= ===~~~ ~~~~~= :===-= =~=~=~ =~-~~~ ~~~~~= ====== ==~=: ::~:: ;;~;; ~~~~~~ ::~;; =:~:: =~=~== ==~== ~~=~=~ ~=~~~~ ~~~~i~~~~~=:fss~~~===================== ====== ====== ====== ====== ====== ====== --X-- ====== ====== ====== ====== ====== ====== --X-- ====== ====== ====== ====== __ _: __ 

¥~i~~~~!~iii~~~~t;=================== ====== ====== ====== ====== ====== ====== ====== ==~== ====== ====== ~~~~~ ====== ====== ====== ====== ==~== ==~== ==~== ====== 

1 Encrusting and ramose types. 

MISSISSIPPIAN, PENNSYLVANIAN, AND PERMIAN 

SYSTEMS 

ELY LIMESTONE 

The Ely Limestone, a light-gray cherty limestone 

about 2,500 feet thick, overlies the Chainman Shale. 

The contact is apparently conformable in a few places 

and is structurally discordant in many places. The 

name Ely Limestone is used here essentially as 

Pennebaker ( 1932) defined it. It consists mainly of 

Pennsylvanian and Permian rocks that lie between 

the Chainman Shale and a thick sequence of Permian sandstone, but it includes some rocks of Mississippian age. 

The Ely Limestone underlies more than 15 square 

miles in the Connors Pass quadrangle, occurring 

chiefly in the southern and western parts of the quadrangle but also occupying a small area near the mouth 

of the canyon of Cleve Creek. It forms moderately 

prominent ridges that contrast strongly with the 

benches and valleys underlain by Chainman Shale. 

Small, moderately continuous, conspicuously yellowish-gray ledges and benches are typical of the lower 

part of the formation (fig. 8), but they are fewer 

and less continuous on slopes formed on the upper 

part. 

No stratigraphic section of the Ely Limestone was 

measured because~ like the Chainman Shale, it is 

much faulted and inadequately exposed. Moderately 

good exposures of the formation are accessible along 

the highway at Connors Pass; the clastic upper unit 

of the formation lies just east of the pass and the 

limy lower unit half a mile to the west of it. In both 

Places however the beds are much disturbed by ' ' f faults and by numerous unmapped shears. Much 0 
42 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

FIGURE 8.-Ledges of Ely Limestone (PIPMe) in a klippe, 

underlain by almost flat-lying Chainman Shale (M c) on the 

south side of the peak at Taylor bench mark. The peak rises 

about 500 feet above the bench formed by the shale. 

the lower part of the formation is fairly well exposed on the west flank of the peak on which Taylor 

bench mark lies and on the south slope of the ridge a 

mile north of The Narrows on the lower part of Steptoe Creek. Much of the crest of the ridge south of 

Connors Pass is underlain by the upper part of the 

formation, but at that place there are few exposures 

and · there is some evidence of minor structural 

complications. 

The Ely Limestone is divisible into two informal 

units, a limestone unit that makes up the lower twothirds of the Ely, and a clastic unit that consists of 

the upper third. These units are not mapped separately although locally a marker bed, b, shows the base 

of the clastic unit. Much of the limestone is shaly, 

and calcareous shale increases in abundance upward. 

The clastic unit contains some' siltstone, sandstone, dolomite, and a very small amount of conglomerate. 

The base of the Ely is almost everywhere faulted; 

the angular discordance on the faults ranges from 0° 

to almost 90°, and the stratigraphic thickness of rooks 

that are missing along the fault may in some places be 

as much as 2,000 feet. Roadcuts about half a mile 

west of Connors Pass also show several wedges of 

Chainman Shale that have been squeezed up into the 

limestone. Obviously then, there is doubt about the 

completeness of all sections near the base of the formation. In some places, however, at which there is no 

evidence of faulting along the base, clastic limestone 

somewhat similar to the limestone interbedded near 

the top of the underlying shale occurs in the lower 

20-60 feet of the Ely Limestone. This rock consists 

of alternating beds of light-medium-gray bioclastic 

limestone, brownish-gray bioclastic limestone, coquina, 

and limy siltstone. The lowest gray limestone beds, 

4-12 inches thick, generally contain chert. 

In the limestone unit, most of the limestone is relatively pure, crystalline; and fine- to medium-coarsegrained, but some of it is bioclastic or crinoidal. 

Toward the top of this part of the formation, moderately thick-bedded limestone in beds 20-40 feet thick 

alternate with equally thick units of platy limestone 

(fig. 8). Most of the limestone contains a little chert 

either in small nodules and lenses or in subspherical 

bodies 1-2 feet in diameter. The chert is light gray 

to brownish gray and weathers to a pale yellowish 

gray. A few units of rock 10-30 feet thick contain 

as much as 20 percent of lenticular and bedded chert. 

The cherty rocks form many of the yellowish bands 

that are conspicuous on some of the slopes. The subspherical nodules are most common in the ledgy units 

or just above them. Many are made up of concentric 

layers of competent and incompetent material and 

resemble· an onion in structure, and some contain 

vestiges of. Chaetetes or possibly of algae. 

About 1,400 feet above the base of the formation, 

near the top of a layer that contains the onionlike 

nodules, abundant subspherical silicified colonies of 

Chaetetes 6 inches to 2 feet in diameter provide the 

very useful marker bed a (pl. 1). Generally there is 

only a single Chaetetes-bearing limestone bed, but in 

some places there are two beds 20 feet apart, and in 

two places (in one of which no structural complications were apparent) there are two beds at least 100 

feet apart. Where Chaetetes colonies disappear 

abruptly along a bed, chert nodules resembling them 

in size and shape continue. . 

The proportion of clastic rocks increases in the 

upper one-third of the . formation, the clastic unit, in 

some places to such an extent that it is difficult to 

identfy the contact between the Ely Limestone and 

the overlying Arcturus Formation. Limy siltstone 

and sandstone make up about 75 percent of the upper 

500-800 feet of the formation, and thin lenses of limestone only 25 percent. The siltstone and sandstone, 

which are very pale yellowish brown to very pale 

orange, are friable and fractured and are rarely well 

exposed. The ·limestone lenses are moderately thick 

bedded and are coralline; they may possibly represent 

biotstromal features. Large fusulines are abundant in 

some of the shaly limestone, and a few beds of this 

rock actually fusuline coquinas or fusuline-granule 

arenite. The clastic unit of the formation also contains a few beds of fine- to medium-grained lightgray dolomite. In the southern part of the quad-
PERMIAN SYSTEM 43 

rangle, the clastic rocks and fusuline limestone appear 

so abruptly in the stratigraphic section as to provide 

another marker horizon. Along Steptoe Creek north 

of The Narrows, a marker bed of chert-pebble conglomerate and breccia about a foot thick lies close 

beneath the fusuline limestone and 500-600 feet above 

the Ohaetetes marker zone. 

Brachiopods and corals are moderately abundant 

throughout the Ely Limestone, and fusulines are very 

abundant at some horizons in its clastic unit (table 7). 

The fauna of the Ely Limestone in this area ranges 

in age from Late Mississippian to Early Permian but 

does not include any Late Pennsylvanian fossils. . In 

some localities the lowest few tens of feet of limestone 

contain Late Mississippian fossils. Rocks equivalent 

to the Missouri and at least parts of the Des Moines 

and Virgil of the midcontinent· region may be missing. 

The conglomerate marker bed, b, at the base of the 

clastj.c unit appears to be a basal unit above an unconformity at or near the base of the Permian. An unconformity of this age is widely~ but not everywhere, 

recognized in eastern Nevada and western Utah 

(Steele, 1960, pl. 4; Dott, 1955). 

The distribution of clastic rocks and unconformities 

in the Ely rocks of the surrounding region indicates 

that during part of Ely time the Connors Pass quadrangle lay near tectonically active areas, and the rocks 

within the quadrangle record several regional tectonic 

events. The slight increase in shaly and silty limestone in the upper part of the limestone unit-that is, 

in the rocks between the two marker beds-is roughly 

within the rocks equivalent to the Tomera Formation 

of Dott ( 1955), 60-80 miles northeast of the Connors 

Pass quadrangle, and inasmuch as the abundant conglomerate in the Tomera suggests that the Antler 

orogenic belt. of central Nevada was uplifted, the 

detrital material in this part of the Ely Limestone in 

the Connors Pass area presumably was derived from 

the west. During Middle and Late Pennsylvanian 

time eastern Nevada and western Utah, as well as the 

tectonic area to the west, were moderately uplifted, 

and the Oquirrh Basin in north-central Utah subsided 

rapidly. Material removed from or carried across the 

Connors Pass area and the eastern Nevada-western 

Utah uplift may have been deposited in the adjacent 

Oquirrh Basin. The clastic unit of the Ely Limestone 

and probably also the clastics in the overlying Rib 

Hill Sandstone seem to reflect renewed uplift of the 

orogenic belt. 

PERMIAN SYSTEM 

RIB HILL SANDSTONE 

The Rib Hill Sandstone, a pale-yellow-brown sandstone about 1,000 feet thick, conformably overlies the 

Ely Limestone. This sandstone was first named the 

Rib Hill Formation by Pennebaker (1932); Steele 

( 1960, p. 103) recommended renaming the sandstone 

the Riepetown Sandstone (for an abandoned town 

near the present site of Ruth), because the name Rib 

Hill had also been applied to a quartzite of Precambrian age in Wisconsin, but the name Rib Hill 

Sandstone is apparently more widely accepted in 

Nevada and it will be used here. 

The Rib Hill Sandstone underlies about 2 square 

miles of the quadrangle in a zone that extends from 

the Taylor mining district to the valley southeast of 

Connors Pass. In small areas where it was difficult 

to distinguish the Rib Hill Sandstone from silty rocks 

in the overlying Arcturus Formation, the sandstone 

was generally mapped with the Arcturus. 

The Rib Hill Sandstone forms gentle slopes and 

lowlands and is poorly exposed. The slopes are strewn 

with small slightly rounded plates and blocks of friable sandstone which weathers to grayish orange, pale 

yellow brown, or pale reddish brown, all more intense 

than any colors of the siltstone in the upper part of 

the Ely Limestone and also more intense than those 

of most sandstone and siltstone in the Arcturus Formation. Near the Taylor district the lower part of 

the Rib Hill contains more reddish-brown rock than 

the upper part. A part of the Rib Hill is well exposed 

half a mile north of Connors Pass and also in the 

small gullies tributary to the main valley in which 

there is a rough narrow road. 

The base of the Rib Hill Sandstone, which is 

nowhere well exposed, is placed above the highest beds 

containing much limestone and beneath the lowest 

relatively pure and intensely colored sandstone. The 

transition between the Ely and the Rib Hill occurs in 

a zone that is generally less than 100 feet thick and in 

some places less than 10 feet thick. The transitional 

zone contains a little of both the shaly limestone and 

the lenticular bodies of thick-bedded coralline limestone common in both the underlying and overlying 

formations. 

Most of the Rib Hill consists of very fine grained 

to fine-grained pure to moderately impure quartz 

sandstone. Dolomite beds 6-18 inches thick and sandy 

and shaly limestone beds are common throughout the 

formation but make up less than 1 percent of it. The 

dolomite is fine grained and medium gray but weathers 

light gray, much like the dolomite in the adjacent 

formations. Most of the sandstone is thick bedded 

to massive, but some of it is faintly laminated and 

cross bedded. 
44 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

TABLE 7.-Fauna 

[Identified by Helen Duncan and Mackenzie Gordon, Jr. (written commun., 1963), Gordon (written commun., 

Epoch____________________________________________ Late Mississippian 

Age _________________________ --- _____ ------- ___ ---

Position in formation ____________________________ _ 

Chester 

Basal unit (~100ft) 

Early Pennsylvanian Middle Pennsylvanian 

Morrow Atoka Des Moines 

Between basal unit and marker bed a Between marker beds a and b 

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

00 0 0 0 000 0 0 0 0 0 00 0 0 0 0 0 00 0 00 0 0 0 0 00 0 0 0 ~~ P-1 P-1 P-1 P-IP-til< P-1 P-1 P-1 i ~ P-Ill< ~ P-1 ~ P-1 P-1 P-Ill< P-1 P-Ill< P-1 P-1 P-1 ~ P-Ill< P-1 ~ ~ U.S. Geol. Survey loc ___________ _________________ I .b I I I I I I .!. ~:2 I .J, I I I I I I I I I I I I 

~~ "' ;:!: c<:>r-oo CQ 0 0 

~ 0 0 ~"' ~ E~ co C'l 

~ ~ ~E ~ OQ 

~ ~ ;:! fl5~~ Ci!l ~ OQ 

~ ~ ~ Ci!l C'l~ ..,. OQ "' 00 C'l ~~ ;:! C'l "' lQ .... ~ ~ o ........ ~ ~ ~ ~ ~ ~ 0 ~ ........ ~ ~ ~ ~ ~ ~ ~ .... C'I C'l C'IC'IC'I C'l C'l C'l C'l C'l C'IC'I C'IC'I C'l C'IC'I 

----- --- - - - ----- - - - --- - ----- - - --- - - - - -- Brachiopods: 

Ant~ff~A~~~J:;~~e';:;{;(~~fy)~i:::!_-~======= == == === == ::: == == == == === === === == == == == === === ======X==============:::======---~--========== === == 

Avo~tidiil<iiii::======== Beecheria sp. indet_ _______===================== __ ____________ ___ ___ == 

__ --

== __=== _ == 

-- === --- == -- --

== == --X == === 

___ ·

=== --- -~- X --== == -- == 

-- -== - === ___ ---

==~ === 

__ _ === ________ == === --

== == 

_____ === -= - == -- === ______________ === -~ == === --

== == 

______________ === === x === == _ 

g~;;rer::~~.aln~i~===== ===================== == == === == === == x == == === === === == == == == === === === === == === == == === == == === === === == === == == === === == === x Cleiothyridina cf. C. orbicularis (McChesney) ____ -- ___ ----------- X ______ X -- -- -- -- --- --- ___ --- -- --- -- -- --- -- -- --- --- --- -- --- -- -- ______ + X -- cf. C. sublamellosa (Hall) __________ __ _____ X ______ _ ___ -- _______ ________________ _____________________________________ ___ __________________ _ 

sp. indet_ __ ____ ______ _______________ ____ __ -- -- --- -- --- -- -- -- -- ___ --- --- -- -- -- -- --- --- --- X __ -----X------- ______ X -- --- -- ___________ ___ _ Composita cf. C. ozarkana Mather ____________ _ __ -- ___ __ --- -------- ______ X __ -- -- -- _________ ________ -- _______ -- _____________ _ ___________ _ ____ _ 

c.~Y~~~~m-!-mm~~~=-~--~! ~ ~ r~ ~~ ~, == ~~ -~ ~ ~~~ ~~- ~~~ ~~ ~~ ~ ~- m m ~~~ ~; ~ m -~ ~~ ~~ -- ~~ m ~~ =-~ ~~ m ~~ ~= ~ ~l~ ~ =~- ~- Desmoinesia ~~:~:~rt~1~~=~=~=~~~~======~==~~=~== a:ff. D. muricatina (Dunbar and ~~ ~~ ~=~ ~~ ~=~ =~ =~ ~~ =~ ~~~ ~=~ =~= ~~ ~~ ~~ ~~ =~= ~~= ~~~ ~~~ ~= =~~ ~~ ~ ~~~ =~ ~~ ~=~ ~~~ =~~ ~~ ~=~ ~= == =~= ~== =~ ~~ ~~ 

~~~~·tt;~~-j~~~~~~~=mmm- Grandaurispina SP---------------------------- -- --~ ~ --~ -~----:~ ----~ -- --~ ~~ --~ --~. _____m 

_

~X=~ ___ ---_~~~~~~~~-~ -- -- -- ___ ---m 

____

~~~ ___~-__-

__ 

_- --~ ~ __ m 

---

~~ -- --~- ~~~ _________ ~-~ m _=::: 

-- ___ 

__ 

--

-~ -- ___________ ~~ ~ ~~ r~ ~ --

!~~;£0~#~!i=m~~~m!!~=-===~-! ~ == ~ == m _- ~ _- ~= -!! :-: ~~ =~ ~~ !- ~= ==! -~~ m -=- ~~ m !: -_ ~- ~= -= ~~! :-: -~! =- =~ ~- ~~ ~, :~= =; ::: =; Linoproductus prattenianus (Norwood and 

:~~~i~ITi<~rrt~:~::~;:;; ;; ; ;, ~; lx! ;; i! ~; :x: !ii ix! ;; ~ ~ ~~ ~~~ ixi ~' :;: ii ~;~ ii j: ~ ;; ;i ;~ :' ~' ~~ ~~ :: ;i !i; ~~ :: ixi ;i 

Reti~~~l~~~~-c-~~~~~:~i~ ~~~!~~~============== ~ == === ~ -~- __ X == == ~~ == = -~- == == == == === -~- === ~~ ~ === :: == === == :: === === === == =----_ == == === === == === == Rhipidomella nevadensis (Meek) _______________ -- -- X -- --- -- -- -- -- ___ --·- ___ -- -- -- -- ___ --- ________ --- -- -- --- -- -- --- ___ --- ----- -- -- --- ___ -- ___ --

!,fi!IJ~~~~~;.t~:~:~~~~~il ~ i~ :x~ ii :~ :; ~ i! ;~~;ii ~ i~ ~ ~ ;: ~x: x; J, :x; ~iii ;iii ji iii; ii; :~:ill il i!! ;; ;; ;x: ~~; !i ixi li 

Spir;y:~:~~:;~~-;=~~~~~~~~~~~~~~~~~~~~~~~~~~~ == ~ == = ~ ~~ ~~ == == == === === == = ~= ~= == == == = == = ~= = == : ~ === == == === == == === === === == === == == ~~~ =~= == === == Spiriferinid (fragment)_- --------------------- ____ --- ------- -- -- -- --- --- --- -- -- -- -- --- --- -"- --- -- --- -- -- --- -- -- --- --- --- -- --- -- -- --- --- -- --- --

~:~tln~te~:gi1tf3~~~~:======================== == :: :=: :: -~- -- X==~ :: :=:: =: == =: :: ::: ::: === :=: :: ::: :: :: ::: :: :: ::: =:: ::: == ==~ == == === === == === -- See footnotes at end of table. 

I 
PERMIAN SYSTEM 45 

of the Ely Limestone 

1963) Gordon and Duncan (written commun., 1962, 1963), and R. C. Douglass (written commun,. 1959, 1961, 1962)] 

Epoch _____ __________ __ _______ _ ---------

g Early Permian 

Age ________ ----------------------------- ~ Wolfcamp 

§ 

Position in formation __ ____ ____ __ _______ ~ Above marker bed b 

D 

...... C'l "" <:'.) t- al ...... 1X> "" "" C'l "" 00 .... "" "" 0 "" ~ i'! 00 1Q ~ ~ <:'.) .... Field No _______________ ____ _ -- __ ----_------- t- .... ~ ~ 0 <:'.) "" .... 0 .... "" .... "" .... 00 .... R 00 0> a> 0> 

e C'< C'l <:'.) <:'.) "" <:'.) "" t- § t- t- t- § t- "" § "" <::> "" "" "" t-

~ 

~ 

fl5 ~ fl5 ~ fl5 ~ fl5 ~ 

fl5 ~ fl5 ~ ~ ~ e e e e e e e e e e e e e ~ fl5 ~ "" "" "" "" "" "" "" "" "" "" "" 1------------------------------------------------ "" "" "" "" "" 

0 0 0 0 0 0 0 0 0 0 0 p.. p.. p.. p.. p.. p.. p.. p.. p.. p.. p.. 

U.S. Geol. Survey loc _______________________ I <:'.) 

~ I I J, I I I I ...... ...... 00 0> "" 0 1J 0> J, 00 "" ~ fl5 0 ...... I C'l 0> ;;!;: "" C'l 00 i8 § C'l 00 ~ ~ ;;!;: .... ;;!;: ~ <:'.) "" "" "" "" ;;!;: fl5 8 .... C'!l ~ "" ::; "" <! "" ~ 0> ~ 0> ~ <! C'l 0 ~ ~ 0 C'l C'l C'l C'l C'l C'l C'l C'l Ei Ei C'l 

~ ~ ~ ~ C'l c:1 C'l C'l C'l ~ tl tl tl tl tl tl tl tl ~ tl tl tl E.! ~ tl 

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

Brachiopods: 

Ant~~~T"~~ft;j~~::Sfso(G-~~t~~!~~~~==== ==== ==== ==== ==== ==== ==== ==== ==== ==== == == ==== == == ==== ==== ==== === = ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== sp __________________________________ ---- --~ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- -- --- ---- ---- ---- ---- ---- ---- ---- ---- ---- Avoniid indet_ __________________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- --- " ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

g~EJ[}f~~~l~i~~====================== Cleiothyridina cf. C. orbicularis === = ==== ==== ==== ==== =~ = ~~~?~ == == ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== == == ==== === = ==== ==== ==== ==== 

c,JJI;~;:~l~~~~~~=-=~=:~~~ ==:: -=:: ==:: :== =~= ~- :~:: :~- ::=: -::: ==~~ :::: :==~ ::: :-_ =~ = :-: :::: :::: =~ := :=~: =~~= =~=~ :~=: :::: ==~~ ~~=~ subquadrata (Hall) __________________ ---------------- -------------------- ------------ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

~~~tf:::feL~~l~~====================== ==== ==== ==== ==== ==== ==== ==== -x- ==== ==== ==== ==== :::: ==== ==== ==== :::: ==== ==== ==== ==== ==== ==== ==== == == ==== ==== 

~~: ~fra:~~:e:~!fo~m)================ ==== ==== ==== ==== ==== ==== ==== ==== === = ==== ==== ==== ==== == == ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== Compositoid indet _______________________ ---- ---- ---·- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----· ----

g~~[th~~~i~;~i~g~e:=================== ==== ==== -X- ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== === = ==== ==== ==== ==== === = ==== ==== ==== ==== 

Der~~~i~~;J~:~~~~s:~---================= === = -X- ==== ==== ==== ==== ==== ==== == == === = ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== Desmoinesia a:ff. D. muricatina 

(Dunbar and Condra) ________________ ---- ---- - X ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ____ ---- _______ _ 

~~~f:~~f~~~in~~L~-----================ ==== ==== ==== ==== ==== -x- == == ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== 

~f:1:~C:~t~·~ !~,;d~~~~-(aift"Y">"-----===== ==== ==== ==== ==== ==== ==== ==== ==== ==== === = ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== === = ==== ==== ==== ==== 

ara;~iiu~iSpina-si>====================== ==== ==== ==== === = ·x- ·x- ==== ==== ==== ==== ==== === = ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== == == ==== Hustedia sp _____________________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Hystriculina sp. indet_ __________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----- ---- ---- ---- ---- ---- ---- ---- ---- ---- Injlatia n. spA _________________________ -------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- _______ _ sp __________________________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

Koz~~~k!~-~~~-~-(~~~~~================ ==== == == ==== ========-X- ====-X-============ ===== ==== =============== ===== === ====== ==== ===== ========= ======== Linoproductus prattenianus (Norwood 

ans~.~~aJ!~~}---======================== ==== ==== ==== ==== ==== ==== ==== ==== -X- == == ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== == == ==== ==== ==== ==== Lissochonetes sp _________________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Marginiferid indet_ _____________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Mesolobus mesolobus decipiens (Girty) ___ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Neospiri[er sp. indet_ ___________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- cf. N. dunbari King _____ _______ _____ ----- -------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Orbiculoidea SP-------------------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- --~ ---- ---- ---- ---- ---- ---- ---- ---- Ovatia n. spA __________________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Productoid indet_ _______________________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Reticulariina campestris (White) ________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- sp. indet_ __ _______ _____ _____________ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

Rhi~~-o~~l~~-~~~~~~~~~s_:~~~~)_-_-_-_-_-==== ==== ==== ==== ==== ==== ==== ==== -X)- ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== Rhynchonelloid brachiopod indet ___ ___ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Rhynchopora sp_ ----------------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Ruqoclostus sp. indet. __ _____ _____ ______ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Schizophoriacf. S. resupinoides (Cox) ___ _ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- Schizophoria cf. S. texana Girty ______ __ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

Spir~le~ i~g:t.s:increbesciii8-(ifiii5====== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== n. SP------------------------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- occidU1£S Sadlick ____ _______________ ---- ---- ---- ---- ---- ---- ---- ---- X ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- opimus Hall, var.. ____ __ ____ ____ ____ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ----

Spir~feroidirldet_-_-===================== ==== ==== ==== ==== ==== ==== == == -x-==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== 

¥1~&~%~{;g~~Jg~e~t~~~~~================ ==== === = ==== ==== ==== ==== ==== =~= ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ~=== ==== ==== ==== ==== ==== ==== ==== ==== 

240-303 0 - 67 - 4 
46 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

Epoch_ -----------------------____________________ Late Mississippian 

Age ____ ------------------------------------------

Position in formation ____________________________ _ 

Chester 

Basal unit 

(,....,100ft) 

Early Pennsylvanian 

Morrow 

Between basal unit and marker bed a 

TABLE 7.-Fauna of the 

Middle Pennsylvanian 

Atoka Des Moines 

Between marker beds a and b 

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

00 0 00 

U.S. Geol. P-dl-. 11 11 11 Survey loc _____________________________ ch J O> ., -.1< 

§ ~ ~ ~ i ,.-..4 cq C"' C'l -t 

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

Bryoza: ArchimedeSSP-------------------------------- ____ ---X _____ --- __ --------------- -- ---------------- . c.------------ __ ------ _____________________ _ 

Cystodictya SP--------------------------------- __________________ -- --- --- --- -- __ -- -- --- --- --- --- -- --- -- __ X -- --- __ --- --- __ --- ~- __________ ____ _ Fenestella SP---------------------------------- __ -- --- _______ -- -- -- --- --- --- -- -- -- -- --- --- --- --- -- --- .. -- --- -- --- -- --- --- X ______ _____ ___ __ _ Fenestellid bryozoan _____________________________ --- _______ -- -- -- --- --- --- -- -- -- -- --- --- -- - --- .. --- -- -- X -- --- __ --- --- __ --- ________________ _ Fistuliporoid brozoan ___________________________________________ -- --- --- --- -- __ -- -- --- --- --- X -- --- -· -- --- -- --- __ X? ________________________ _ Penniretipora sp _______________________________________ ___ ___ _____ --- --- --- -- -- __ -- --- --- --- --- -- --- -- __ --- -- --- __ X --- X ________________ _ 

~r;g;;s;gps&oidbryozo"i1r1iil<iei~~============= == == === == == ::: :: :: :: ::: ::: ::: :: :: :: :~ ::: ::: Q ::: == ==~ == ~ x == ::: :: ::: ::: Q == ~ ::: ::: :: ::: :: 

~~:~ggg~t~ ~~~g~:~-<ei1cl-ustiiii!orm)=:::::: :: :: ::: == :: ::: :: :: :: -~- ::: ::: :: :: x :: ·-x.- ::: ·-x.- ::: ~ ::: :: :: ::: :: ::: :: ::: ::: -- ·x.· -= :: ::: ::: :: ::: :: 

Stenoporid bryowan (large ramose form) ___ ___ X ____ _ ___ ___ _ . _____ .... --- --- -- ____ -- --- --- --- -- - -- -- _ -- -- --- -- --- __ --- ___________ ___ _ _______ _ Stenoporid bryozoan (smallramoseform) ___________ _ ___ __ __ .. ________ ____ _____ ____ __ _ --- --- --- ___ __ -- __ --- -- --- __ X _________ __ _ ____ ___ _ Trepostomatous bryozoan indet. (ramose ____ X ____ _ __ X __ . ____________ --- ___________ :-- X --- __ -- - -- __ --- -- --- __ X ______________ _ __ _ ___ _ _ 

form). Trepostomatousbryozoanindet_ ___________________ _ ______ _ ,_ 

Corals: Amplexizaphrentis?sp ________________________ ____ X _______ ... ____ --- --- -- -- __ -- -- - --- --- --- -- --- -- -- --- -- --- -- --- --- ___________ __ _______ _ Auloporid coraL ______________________________ ~- __ __ _____ ___ .... -- --- --- -- -- -- -- --- --- --- --- -- ---- -- -- --- -- --- -- --- --- X -- -- -- ~ _______ _ Caninoid coral sp. indet_ _____________________ -- ____ __ _ ___ ____ -- __ X --- --- -- -- -- -- --- --- --- --- -- ---- ---- .c .----- ----- X X -- -- X __ _ ____ _ Caninia trojana Easton? ___________ __ _______ __ --___________ _ ... __ --- -- - --- -- -- -- -- -- - --- --- --- -- --- -- -- --- -- --- -- --- --- __ --- __ X __________ ._ Chaetetes SP----------------------------------- ______ _ _______ .. __ ___ ___ __ ..... ________ --- --- --- --- -- X X- - X X--- __ ------ ___ ____ -- __________ _ Diphyphyllumconnorsensis Easton ________________ _ ____ ________ ___ --- ___________ --- --- --- -- - .. ___ -- -- --- -- --- __ --- --- ___________________ _ Horn coral indet _________________________________________ ___ ... ______ _ __ _ X _. ______ --- --- -- - --- -- ----- X --- -- --- -- X --- _____ -- -- --- .:. ____ _ 

Kleopatrina ftatateeta (McCutcheon and Wilson) ________ ___ _________ __________ __ __ _ ______________________________________________________________ _ ______________________________ _ Lithostrotionella sp ________________________________________________________________________________________ _ __________________________________ _ 

dilitata Easton? ___________________________________________________________________ --- --- --- -- --- -- -- --- -- --- -- --- --- ____ _ -- -- --- _________ _ "Lonsdaleia" cf. L. illipahensis Easton ________________________________________________ --- --- --- -- --- -- -- --- -- --- -- --- --- _____ -- -- --- _________ _ Multithecopora sp. A __________________________________________ X _____ X ___ X __ ---- X?---------------------------------- ____ _ ------------ ____ _ sp. B _____________________________________ -- __ --- -- _____ .• -- __ --- --- --- -- ____ -- --- --- --- --- -- --- -- -- --- -- X? X --- --- X?-- -- X'?--- -- --- --

Orygmophyllum? SP-------------~------------- _______ -- __ --- ______ --- X --- -- -- -- --X? X.----------------------------------------------------- Syringopora sp _____________________________________________________________________ --- --- --- --- -- --- -- -- --- -- --- -- --- --- -- ___ --X--- ___ -- ____ _ 

mccutcheonae Wilson and Langenheim ________________________________________________ --- --- -- ___ -- -- --- -- --- -- --- --- -- ___ -- -- --- --- ______ _ Thysanophyllum princeps Easton __________________________________________________ --- --- --- --- -- --- -- -- --- -- --- -- ---· --- -- .-- -- -- --- --- -- --- __ sp. indet ________________ ______________________________________ --- ___ --- -- -- ____ --- --- --- --- -- --- -- -- --- -- --- -- --- --- -- --- -- -- --- --- -- --- __ 

Foram_inifera: . Clzmacammzna SP----------------------------- __ -- --- -- -- --- -- -- -- --- --- --- -- -- -- -- --- --- --- --- -- --- -- -- --- -- --- -- --- --- -- --- -- -- --- --- -- --- -- Endothyrid ____________________ _________________________________________________ -- --- --- --- --- -- --- -- -- --- -- --- -- --- --- -- --- -- -- --- --- -- --- --

Pse·udofusulina SP----------------------------- .-- -- --- -- -- --- -- -- -- --- --- --- -- -- -- -- --- --- --- --- -- ~-- -- -- --- -- --- -- --- --- -- --- -- -- --- --- -- --- -- Pseudoschwagerina SP------------------------- _______________________ --·- _______ -- -- --- --- --- --- -- --- -- -- --- -- --- -- --- --- -- --- -- -- --- --- -- --- -- Schubertella SP-------------------------------- _________________________________ -- -- --- --- --- --- -- --- --· -- --- -- --- -- --- --- -- --- -- -- --- --- -- --- -- schubertellid ______________ ___________________________________________________________________________________________________ ________________ _ 

:if~~f~~~~fd~-~~-----------------------------------------------------===== == == === == == === == == == === === ::: == == == == === === === === == === == == === == === == === === == === == == === === == === == Triticites SP----------------------------------- -- -- --- -- -- --- -- -- -- --- --- --- -- -- -- -- --- --- --- --- -- --- -- -- --- -- --- -- --- --- -- --- -- -- --- --- -- --- -- Others: 

i~~l~~;;~~~~!:::::~::=~~~:~~:~::=::: :~ ~~ :~: :: ~: ::: :~ :: :: ::: ~-: =~: :: ~: := :: ::= ~i ~;: ::: :: ::: := :: ::: :: ::: :: ::: ::: ~~ :~: ~: ~ ::: =:: :: ~:: ~ 

if~~ffi11f~TErmZ:F~m_::- =: :~ m -- :: ~-: ~ =- -- :x: ~:: :=_ ~~ ~= :~ ~ ::: ::~ =:= ::- ~- ~-= ~: :: ::~ :: =~~ :_ -~= =~: ~: ::: ~: :: ::: ~:= ~ :~~ ~: ~~~~:C~d~s~~-~~~~~~~-~~::::::::::::::::::: ::: :: ~ :: ::: :: :: ::: :: :: :: ::: ::: :::]:: :: :: :: "~- -~- !:_ ::: :: ::: :: :: ::: :: ::: :: ::: ::: :: ::: :: :: ::: ::: Q ::: :: 

1 From same locality as field No. 61D737. 2 Mixed collection, specimens largely from float from rocks in stratigraphic interval 

of about 50 feet near hilltop on inferred fault slice of Ely Limestone. 
Ely Limestone-Continued 

Epoch _______ --------------------------- .C 

Age_____________________________________ "§ .S 

d 

0 

<.l Position in formation_------------------ ;5 

Field N 0------------------------------------

..... 

>Q C'l 

~ ~ e """ C'l 

A A A 

,........'E'---, ~ ~ ~ 

PERMIAN SYSTEM 

<'.) ,_ a'S ..... ~ 0 <'.) 00 

<:0 ~ """ c M <'.) >Q <'.) <:0 e A A A A 0 A ~ ~ ~ 0 

<:0 ~ ~ <:0 

47 

Early Permian 

Wolfcamp 

Above marker bed b 

~ >Q <:0 C'l or) 00 """ >Q I <:0 ,_ 0 <'.) """ 10 >Q ~ """ >Q """ 00 """ 0 00 00 0> 0> 0> 

e ,_ e ,_ ,_ ,_ <:0 e e <:0 <:0 <:0 <:0 <:0 e e e e e e e e e e § <:0 <:0 <:0 <:0 <:0 <:0 <:0 <:0 <:0 <:0 <:0 <:0 <:0 <:0 <:0 

1------------·----!---.---·-----·-------------------

0 0 0 0 0 0 0 0 0 0 0 P-c P-c P-c P-c P-c P-c P-c P-c P-c P-c U.S. Geol. Survey loc _______________________ I C<:J J, I I J, I I ~ 2 I ..... 

~ 00 

~ ~ 0 """ 0> J, 00 >Q 

~ 0> g 0> ..... C'l 

""" <:0 C'l 00 ::g ~ 00 ~ ~ ~ <'.) ;g <:0 >Q <:0 <:0 0> >Q <:0 <:0 ~ ~ ~ ~ ~ ~ ~ ~ ~ 0> ~ 0> """ >Q 

~ 0 0 ~ 0 C'l C'l C'l 

~ C'l 

~ ~ ,_ C'l ~ ~ ~ C'l c:1 C'l C'l c:1 ~ tl tl tl tl tl tl tl ~ ~ tl tl tl ~ tl '------------------------------. ---------------

Bryozoa: Archimedes sp ___________________________ ---- ---- ---- ---- ---- ---- ---- ---·----- ---- ---- ---- ---- ________ ---- ---- ---- ---- ---- ---- ________________ ____ ----

Fenestellid ~~~~~1!zf~~~~~========================== ==== ==== ==== ==== ==== ==== ==== -x- ==== ==== ==== ==== == == ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== bryozoan ____________________ ---- ---- ---- ---- ---- -------- ---- ---- ---- ________ ---- ________ ---- ---- ---- ___________________________________ _ Fistuliporoid brozoan ___________________ ---- ---- ---- ---- ---- ____ ---- ---- ____ ---- ________ ---- ____ ____ ---- ---- ---- ____________ ___ ___________________ _ _ Penniretipora SP--- --------------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- -.--- ---- ---- ---- ---- ----

'~%£.b"g;&o-i(f1iryozoa11incteC======== ==== ==== ==== ==== ==== -x- ==== -x- ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== :::: 

llEE11Hi!fgggEr~~EEl= Trepostomatous bryozoan indet. (ramose ~~=~ ~~~= ~=~: ~~~~ ~~:: ~~~: ~==~ :~: :~: =~=~ :=~~ =~=~ ~~:: =~~~ ~~~~ =~~= =~~= ~~~~ ~~~: ~~~: ~~~= ~~-~ ~=~~ :~~~ ~~~~ =~=~ ~~~~ form) _________________________________ ---- ---- ---- _· _______________________ ______ ________ _________ ________________________________________________ _ Trepostomatous bryozoan indet_ ________ ---- ---- ___ _ ____ ____ ____ ____ X ___________________________________________________________________________ _ Corals: Amplexizaphrentis? sp ___________________ ---- -------- _____ _______ __________ ____ ___________________ _____ ___ _______ ____ ____ , ___________________________ _ Auloporid coraL ___________________ __ ___ ---------------- ____ X ---- ---- ---- ---- ---- ---- ---- ---- ____ ---- ---- ---- ---- ---- ---- ---- ---- ---- ________ ---- Caninoidcoralsp.indet ________________ ------------ ___ _____ _____ __ _______ __ ________ ______ __ __ ___ ________ ___ _______ _____ _________________ ______ ____ _ Caninia trojana Easton?----------------- ____ ---- ___________________________________________________________________________________________________ _ Diphyphyllum Chaetetes SP----------------------------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- connorsensis Easton____ X ---- X? _____________ c __ __________________________________________________________________________ __ ___ _ 

Horn coral indet~- --- --------- --------- ---- ---- ---- ---- ____ ____ ____ X ---- ___ _ ---- ____ ---- ____ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ____ ---- ---- Kleopatrina [tatateet a (McCutcheon and Wilson) __________________________ _ ---------------- ______ __ X ________ cf. ____________________________ ---- ________ ____ __ ______ _______________ _ Lithostrotionella SP---------------------- ---- ---- ---- ---- ________________________________________________ ---- ________________________ ____ ____ X ___ _ 

dilitata Easton?-------~------------- ---- ---- ---- ---- ---- ________ ---- X ________________ ____ c ___ ---- ____ ---- ________________________________ ----

"Lonsdaleia" cf. L. illipahensis Easton __ ---------------- ________ ____________ X ___________________________________________________________________ _ 

MuUithecopora sp. A-------------------- ------------------------ ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- sp. B __ ----------------------------- ___________________________________________________________________________________________________________ _ 

Orygmophyllum? sp _____________________ ---- ---- ---- ---- ---- ____ ---- ---- -------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- -------- ---- ---- ---- ---- ---- Syringopora sp ______________________________ ---- ---- ---- ______ __ ---- -------- ____ ---- ____ ---- ---- ---- ---- ---- ---- ---- -------- ---- ---- ---- ---- ---- ---- mccutcheonae Wilson and Langenhiem __________________________ ---- ---- X ________ X? _______________________________________ _ ____ X ________________________ X ___ _ 

Thy~~~~~~~~l~~~~i~~e~~~~~~~~======== ==== ==== _X_?_ -~- :::: ==== :::: ==== -~- :::: :::: :::: :::: :::: :::: :::: :::: :::: -~- :::: :::: :::: :::: :::: :::: :::: :::: Foraminifera: Climacammina sp ___________________________ ---- ________________ .---- ___ _____________________________________ ----________ X X X ____ X _______ _ 

~};~~!~~~~~::~~~~~~~~:~~~~~~=~~ -=~~ :~ ==~= :~~~ ~: : ~~~: :::- ~~-~ ::_: ::-: :::: ~: :~; ;~; :~: :~: ;~; ~:~: :~: ;~; :~: :~ :~: =~=~ :~,: ::=: :~: Schubertellid ___________________________________ X ______________________ _______ ____ ________ __ ___ __ X X _______________________________________ _ 

¥~~~~f::t:t~-~~==:::::::::::::::::::::::: :::: -x- :::: :::: :::: :::: :::: :::: :::: :::: =::: -x- -x- :::= -~- ~ -x- :::: :::: :::: :::: -~- :::: -~- :::: :::: --x- Triticites sp _____________________________________________________________________ X __ .,_ _____________ ---- ---- ---- ---- ---- )(? ---- ---- ---- X ---- ---- Others: Ameura sp. (pygidium)_________________ ____ ____ _ _ _______ ______ __________________________________ ---- ____ -------- ---- -------- ---- ---- ---- ---- ----

~!~~~~rs~-~-~;;====================== ==== ==== ==== ==== ==== =~= ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== 

~!i¥JRf~1~~y~~=~~~~r=o~~;==i~~~~===== Crinoid plate ___ ____ ==== ==== ==== ==== ==== =·=== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== ==== __ ________________ ______________ .________________________________ _ _____________________ ________ ---- ---- ---- ---- ---- ---- ---- ----

~~i:~~o~~~~mde~;is::::::::::::::::::::: :::: :::: :::: ==== :::: -~- -~- ==== :::: :::: :::: ==== :::: :::: :::: :::: :::: :::: :::: :::: :::: ==== ==== ==== :::: :::: :::: Ostracodes _____________________________ _____________________________________________________________ ---- -------- ---- ---- ---- ---- ---- ---- ---- ---- ----
48 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

The sandstone is 60-95 percent quartz grains and 

1-2 percent heavy minerals; the remainder IS clay 

material, calcite cement, and a little silica cement. The 

heavy minerals include, in order of decreasing abundance, tourmaline, leucoxene, zircon, rutile ( ? ) , and 

Iron oxide, a suite resembling in type and abundance 

those in all sandy rocks above the sandstone marker 

In member b of the Guilmette Formation. Sericite 

and possibly chert are also present In very small 

quantity. The average grain size of much of the rock 

Is 0.06 mm; most of the small grains are angular, but 

the larger grains of quartz and the grains of heavy 

minerals are more or less rounded. The quartz grains 

are mostly well sorted and many are frosted. The 

calcite cement is irregularly distributed; so many of 

the quartz grains interlock. 

Fossils are scarce in the Rib Hill Sandstone, but a 

few were collected from limestone within 100 feet of 

the base (table 8) . Some of the fusulines were identified by R. C. Douglass as Sehwagerina( ?) sp., of 

a type thus far reported only from the basal beds of 

the Riepetown Sandstone (here called the Rib Hill 

Sandstone) of D. R. Shawe's section A (written commun., 1961) in the Egan Range. · Both at that locality 

and In the Connors Pass quadrangle the enclosing 

rocks contain fossils of Early Permian age, or Wolfcamp age as the term is used In west ·Texas; thus, 

the Rib Hill Sandstone is probably of W olfcamp age. 

TABLE 8.-Fauna of lowermost 100 feet of the Rib Hill Sandstone 

[Identified by R. C. Douglass (written commun., 1961, 1962), Mackenzie Gordon, Jr., 

and Helen Duncan (written commun., 1963)) 

Age __________________________ _ 

Field No., abbreviated __________ _ 0 

00 

C'l 

Wolf camp 

~·-------------1----~-------

U.S. Geol. Survey loc ___________ _ 

~---~----------1--- ---------

Crurithyris sp___________________ X ____________ ------

Trepostomatous bryozoan (small ramose form)_________________ X _________________ _ Fusuline in deL_________________ X _________________ _ Monodiexodina sp_______________ ______ X ___________ _ 

Pseudoschwagerina sp____________ X _____ _ >< 

Schubertella sp_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ X ___ __ _ ___ __ _ 

Schwagerina sp _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ X ? __ ---- Climacammina__________________ X 

The area In which the Rib Hill Sandstone has 

been mapped IS limited to part of White Pine 

County, Nev., but Steele (1960, p. 103) recognized the 

lithology farther to the north and west. The Rib 

Hill Sandstone seems to be a local highly clastic 

facies near the base of a group of rocks of a mixed 

lithology similar to that of the Arcturus Formation, 

and as it increases in limestone and dolomite content 

the Rib Hill loses its lithologic identity. To the west 

the correlative of the Rib Hill Sandstone is the lower 

part of the Carbon Ridge Formation of Nolan, Merriam, and Williams (1956), which contains considerable conglomerate as well as more limestone than the 

Rib Hill. To the east the Rib Hill Sandstone loses 

its lithologic identity near the Utah~Nevada border. 

In the Confusion Range it is probably represented by 

part of the Arcturus Formation of Hose and Repenning ( 1959), and at Gold Hill by a small part of the 

Oquirrh Formation of Nolan (1935). 

ARCTURUS FORMATION 

The Arcturus Formation-several thousand feet of 

heterogeneous rock, containing much limestone, dolomite, shale, and sandstone, and locally much conglomerate and a little gypsum-conformably overlies 

the Rib Hill Sandstone. These are the youngest 

Paleozoic rocks in the quadrangle. The name Arcturus Formation was first applied to them in the 

Egan Range by Lawson (1906, p. 293), but the formation was redefined by Spencer (1917, p. 28} and 

given a type locality near the Arcturus claims in the 

Robinson mining district just west of Ely. The name 

is applied here, as it was by Steele (1960, p. 103), to 

the rocks above his Riepetown Sandstone (here called 

the Rib Hill Sandstone)., and below the Kaibab Limestone (of Leonard age). The Arcturus Formation 

in the Connors Pass quadrangle differs from that of 

the type locality, just west of Ely, chiefly in probably 

containing a tongue of conglomerate many hundreds 

of feet thick in its upper part. The top of the formation is not exposed within the quadrangle. 

The Arcturus Formation underlies more than 4 

square miles in the southern part of the quadrangle, 

chiefly in the southern part of the drainage basin of 

Cooper Canyon and in the drainage basin southeast 

of Connors Pass. The formation is in general so 

poorly exposed that its internal structure is obscure 

and its thickness therefore hard to determine. No 

subdivision that is widespread within the Connors 

Pass quadrangle has been made, but locally a conglomerate member has been mapped. A basal limestone unit is also referred to in the following description, but most of the formation is described lithologically rather than stratigraphically. Rocks characteristic of the formation are well exposed along 

both the old and the new alinements of U.S. Highway 6-50-93. Most of these rocks form gentle 

slopes and low hills, but the limestone near 

the base forms low ridges and narrow ledges. 
PERMIAN SYSTEM 

Outcrops of Arcturus rocks other than this limestone unit are scarce and usually consist of limestone, dolomite, or conglomerate. 

LITHOLOGY 

A basal limestone unit of the Arcturus forms lenses 

as much as 400 feet thick. It consists of moderately 

thick-bedded coralline limestone, shaly limestone, and 

interbedded siltstone and sandstone. This unit is 

thickest about a mile southeast of Connors Pass, but 

it is virtually absent half a mile farther south, where 

there is no evidence o:i bedding-plane faults. The 

individual limestone beds or groups of beds are lenticular; many of them are about 50 feet thick and 300 feet 

long and resemble biostromal reefs. The limestone is 

fine grained to moderately coarse grained, and much 

of it is bioclastic or crinoidal. Fossil fragments are 

common, and small silicified spines, possibly of 

echinoids, are conspicuous on many weathered surfaces. Light-gray chert, which weathers white to 

pale yellowish brown or yellowish gray is widespread 

but rarely abundant. It assumes a large variety of 

shapes, such as concentrically layered subspherical 

bodies, amoeboid nodules 6-12 inches in diameter, 

lenses parallel to bedding, and small pelletlike bodies. 

Locally, groups of limestone beds 5-20 feet thick contain as much as 75 percent chert, in cores surrounded 

by siliceous siltstone or limestone, but the interbedded 

siltstone and sandstone resembles that in the main 

body of the formation. In many ways, then, the basal 

part of the Arcturus Formation resembles the upper 

part of the Ely Limestone, but the two can he distinguished by their stratigraphic relation to the Rib 

Hill Sandstone and generally by their fossils. Where 

the basal limestone of the Arcturus is absent or is thin 

bedded, the base of the formation grades into the 

underlying Rib Hill Sandstone. 

The main part of the Arcturus is much more heterogeneous than the basal limestone unit; within the 

quadrangle it is estimated to be at least 1,500 feet thick 

and possibly much thicker. It consists of a mixture 

of sandstone, limestone, dolomite, and shale, which 

are mostly very pale yellowish brown, though some 

are white or pale red. The term "marl" may be appropriate for much of the formation. In the exposures 

along the highway east of Connors Pass the beds of 

the main part of the formation are 2-12 inches thick, 

but elsewhere the beds vary more in thickness. 

Sandstone typical of the formation contains 65-85 

percent of very well sorted quartz grains, appreciable 

amounts of detrital tourmaline, leucoxene, zircon, 

rutile ( ? ) , plagioclase, and some calcite that may be 

detrital. The grains are cemented with calcite, clay 

minerals, iron oxide, and a little silica, distributed 

somewhat irregularly. The grains range from very 

fine sand to fine sand; those surrounded by cementing 

material are subrounded to rounded, whereas the others 

are angular and form a compact polygonal mosaic 

without interpentrating boundaries. Such a packing 

suggests that the close mutual accommodation of 

grains was obtained by the solution of parts of the 

grains, perhaps along the pressure surfaces between 

the grains. Inasmuch as overgrowths are relativeiy 

scarce, silica must have been removed from parts of the 

rock; indeed, the general friability of the rock indicates that silica must have been removed from much 

of the unit. Yet only a moderate amount of silica 

appears to have been removed in this manner, for there 

is no obvious difference in size between the grains 

forming the mosaics and those surrounded by cementing material. In the rocks that have a mosaic texture, 

the shapes of the grains and possibly also their size 

characteristics are diagenetic features, and the diagenetic process may have ceased when the polygonal 

mosaic was completed and the pores were filled. 

The limestone in the main part of the formation 

is similar to that in the basal limestone unit except 

that it occurs in thinner and more scattered lenses. 

Corals and echinoid ( ? ) and crinoid debris are common, and fusulines occur in many of the shaly limestone beds. 

Fine-grained light-gray to pale-yellowish-brown 

dolomite, similar to that in the Rib Hill Sandstone 

and the top of the Ely Limestone, forms a few thin 

widely separated lenses; this rock seems more abundant 

than it really is because, being especially competent, 

it forms ledges. 

Shale is probably also common, but it is very rarely 

exposed. Near the conglomerate lens north of the 

highway, shale makes up about a quarter of a poorly 

exposed section about 400 feet thick. Some of the 

weathered shale beneath the conglomerate is veneered 

by a powdery soil, which is capped by a brown crust 

resembling that formed on gypsiferous ground; presumably this shale is here gypsiferous. There is no 

conspicuous gypsiferous zone in this area, however, ~s 

there is in the Egan Range southwest of Ely. In this 

part of the Schell Creek Range, more gypsum may 

have once been present in the upper parts of the 

Arcturus that presumably were cut out by the lowangle fault above the Arcturus northeast of Connors 

Pass. 

CONGLOMERATE MEMBER 

In the upper part of the Arcturus For~ation al?ng 

the highway east of Connors Pass, there IS a reddish-
50 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

brown conglomerate that is probably more than 500 

feet thick at that place but wedges out rapidly to the 

northwest. The thickness body of conglomerate lies 

almost entirely south of the highway at the big bend 

1-2 miles east of the pass, where it seems to be faulted 

down into other rocks of the Arcturus Formation. A 

thin conglomerate bed is also exposed half a mile 

northwest of the bend. These beds of conglomerate on 

both sides of the highway are here referred to as the 

conglomerate member of the Arcturus Formation. 

Much of the conglomerate underlies gentle terrain and 

weathers to small knobs and large boulders, but the 

thin lenses of this rock are more friable and leave 

only residual pebbles in the soil. 

As a whole, the conglomerate member is interbedded 

with other rocks in· the Arcturus Formation, and in 

some places an unconformity underlies the member. 

Between the old and new alinements of the highway, 

for a distance of about 1,000 feet, the base of the conglomerate cuts gently across an underlying limestone 

bed that dips about 20° more steeply than the conglomerate. The exposures here are inadequate for one 

to determine whether the unconformity represents 

local channeling at the base of the conglomerate or is 

of greater structural significance. 

The conglomerate is a thick-bedded moderate-red to 

light-brown rock consisting of chert and quartzite 

pebbles in a sandy slightly calcareous m~trix. The 

pebbles are subrounded to rounded and have smooth 

to polished surfaces. North of the highway the 

member also contains some grit and granule conglomerate and conglomeratic sandstone. Some fossiliferous Permian limestone and sandstone are 

apparently interbedded in the main body of conglomerate, but the stratigraphic relations lire partly obscured by local faults of unknown throw. 

Very little of the upper contact of the conglomerate 

member is exposed. In a roadcut at the big bend in 

Highway 6-50-93, younger tuffaceous shale is inferred 

to be faulted onto the conglomerate, and some blocks 

" of conglomerate are faulted or slumped onto the shale. 

Northwest of the bid bend in the highway, thin lenses 

of conglomerate are overlain with apparent conformity 

by fossiliferous Permian limestone. 

FAUNA, AGE, AND CORRELATION 

Corals, brachiopods, and fusulines are n1oderately 

abundant in some of the limestone beds of the 

Arcturus, and a few beds contain many gastropods 

and pelecypods. Fossil fragments abound in all the 

carbonate rocks, and echinoid ( ~ ) spines are conspicuous on many weathered surfaces. All the identified fossils are listed in table 9. 

TABLE 9.-Fauna of the Arcturus Formation 

[Foraminifera ident~ed by R. C. Douglass (written c<!mmun., 1959, 1961); corals by . Helen Duncan (written com!fiun., 1963); most brachiOpods by Mackenzie Gordon, 

Jr. (Duncan and Gordon, written commun., 1963), some by J. T .Dutro, Jr. (written commun., 1960); gastropods, pelecypods, and a few brachipods by E. L. Yochelson 

(written commun., 1960)] 

Age ________ _________ _________ ____________ _ 

Type of fauna ______________ ____ ___ ___ c___ as 

Wolfcamp 

I 

Wolfcamp or Lenard 

~ 

;g Arcturus 2 

Approximate position in formation where 0 known (feet above base) __ ______________ g 

----·---------------------- 00 

ff5 Field No __________________ _______________ 8 

<0 

0 0 0 0 0 p., p., p., p.. p.. 

U.S. Geol. Survey loc _______ ____ _____ __ __ ~ ~ g; ~~ t!: ~ 

~ ~ ~ ~~ ~ ~ --- --------- - - ---- .-- ~--- --

Brachiopods: Aulostegid bn.chiopod, n. gen., n. sp __ ---- ---- ---- ____ X _______________ _ Avoniid productoid indet_ ____________ ---- ---- ---- ______________ __ X ___ _ Composita subtilita (Hall) ___ ______________ X ___ _ _______________________ _ 

1-Ieteralosia SP----·-------------------- ---- ---- ---- ___ _ X ________ _______ _ Neophricodothyris? ___________ _________ ---- ---- ---- ____ X _____ __________ _ Spiriferinid indet _____________________ ---- X ---- ________________ _ 

Bryozoans: 

Fistuliporoid bryozoan (lamellar growth form) _____ _____ _____________________ __ ---- X ---- __ __ ---- ____________ ___ _ 

Stenoporoid bryozoan (lamellar growth form) _______ c ______________ ___________ ---- X ---- ____ ---- ---- ___________ _ Tabulipora arcturusensis Gilmore?____ X ---- ---- ____ ---- ________ _____ __ _ 

Corals: 

1-Ieritschioides sp ___ __ _____ ____________ _ ---- ---- X ____ --··- _______________ _ 

Kleopatrina ftatateeta (McCutcheon and Wilson) __ _____ ___ _______________ >~ ---- ---- ____ ---- ---- _______ ____ _ Lithostrotionella dililata Er.ston? ______ _ ---- ---- ---- X ---- ---- ---- _______ _ Lophamplexus? sp. indet_ ___ ___ ____ ___ ---- X ---- ____ ---- ---- ________ ___ _ Roemeripora? sp _______ _______________ ---- ---- ---- X ---- ---- ---- _______ _ 

Foraminifera: 

~!:~~~~~~na-si>========================================~ ~ ===~ ==== ==== Schubertella sp ___________________________ c ---- ---- ---- ---- X ---- ---- ___ _ Millerellids _______ ____________________ ---- ---- ---- X ---- ---- ---- ---- ___ _ 

Schwagerina SP-- ------------- 7 ------- ---- ---- ---- X ---- X ---- ---- ----

Gastropods: Amphiscapha sp. indet_ _______________ ---- ---- ---- ---- ---- ---- ---- X ---- Bellerophon sp. indet ___ ______________ ---- ---- ---- ---- ---- ---- ---- X ---- Euphemites sp. indet_ _________________ ---- ---- ---- ---- ---- ---- ---- X? X 

Gastropod indet. (moderately high 

~~1~~1~fEi~!~1r~~~~~.=~i~~i~~====== Omphalotrochus cf. 0. whitneyi (Meek) _ ==== 

---- ~=== ---- ==== ---- ---- ==== -

==== --- ==== 

---- ==X == B =~; Permophorus? sp. indct__c ____________ ---- ---- ---- ---· ---- ---- ---- X 

Pleurotomaraceansindet. (two genera)_---------------------------- X 

~~~~~~zi'J:oR~~~~~~!~l~_e_t_-_--~~========= ==== ==~= ==== ==== ==== === = ==== ~ Others: 

fii~~~r~~~;mm -~--~~~~-- --~- =~- X: •••~ -•-= ==-= -•= ~ : 1 Kleopatrina supposedly is a late Ely fossil, the Tabulipora is questionably ide!J-tifi~d 

with an Arcturus species. They were collected above rocks mapped as the Rib Hill 

sar~~~~~~oll~ctions either require or permit a correlation with an Arcturus fauna. 

The Arcturus Formation is identified as Permian on 

the basis of fossils. Its fauna in the Connors Pass 

quadrangle is comparable to that of th~ W olfcamp 

Series and perhaps also of a part of the Leonard 

Series in the West Texas region. The oldest rocks lie 

well above the base of the W olfcamp, but, so far as I 
JURASSIC, CRETACEOUS, AND TERTIARY ( '?) SYSTEMS 51 

can judge from the genera identified, the local fauna 

throughout that stage is uniform. 

The age of the conglomerate member here considered to be part of the Arcturus Formation, has 

been the subject for considerable speculation by geologists who have seen the rock along the highway, and, 

indeed, the assigned Permian age is tentative. P. J. 

Barash (oral commun., 1963), for instance, considered 

the conglomerate to be Tertiary because he placed less 

emphasis on the significance of the fault separating 

the conglomerate from the overlying shale in the 

roadcut and more emphasis on the significance of the 

basal unconformity. A Permian age is preferred to a 

younger age, however, because northwest of the big 

bend in the highway some conglomerate lenses seem 

to be interbedded in fossiliferous Permian limestone 

and because south of that bend in the high"·ay some 

fossiliferous Permian limestone appears to be interbedded in the main body of the conglomerate. 

The name Arcturus Formation is used only in eastcentral Nevada and adjacent parts of Utah. The 

Arcturus Formation of the Connors Pass quadrangle 

is represented in the Confusion Range, about 40 miles 

to the east, by the middle and upper part of the 

1 

Arcturus Formation described by Hose and Repenning 

(1959). Steele (1960) advocated the use of the name 

Pequop Formation for correlative rocks at ~Ioorman 

Ranch between Ely and Eureka, Nev., and also north 

of the Connors Pass. The Arcturus is also correlative 

with part of the Oquirrh Formation (Nolan, 1935) at 

Gold Hill, Utah. 

The lithology of the Arcturus Formation in the 

Connors Pass quadrangle suggests deposition in a shelf 

area, and comparison with correlative rocks in nearby 

areas suggests that the shelf lay slightly south of the 

axis of the basin. The Arcturus within the quadrangle 

includes at least a small ~mount of gypsum, which 

occurs in greater abundance in contemporary rocks 

(Hose and Repenning, 1959) in the Confusion Range, 

in part of the Egan Range (A. L. Brokaw, oral commun., 1962), and in the southern part of the Butte 

Mountains (Douglass, 1960). The formation also 

includes some conglomerate, similar to that found by 

Nolan, Merriam, and Williams ( 1956) in the southern 

Sulphur Springs Range, by Dott (1955) in the northern Diamond Range about 75 miles to the northwest, 

by Sharp (1942) and Dott (1955) in the southern 

Ruby Range about 60 miles to the northwest, by 

Snelson (1955) and Harlow (1956) in the Spruce 

Mountain area about 85 miles to the north, and by 

Nolan ( 1935) in the "central facies" of the Oquirrh 

Formation at Gold Hill, Utah. The position of the 

conglomerate member in the southeastern part of the 

quadrangle and its wedging out to the northwest suggest that the pebbles came from the south or southeast; 

however, inasmuch as only a little conglomerate is 

found in the area, there is no assurance that the source 

lay in that direction. The composition and the rounding of the pebbles, considered together, suggest that 

they were transported a long distance. During 

Arcturus time the Connors Pass quadrangle probably 

lay in a shelf area along the southeastern margin of a 

marine basin, a basin that was nearly or entirely landlocked part of the time. 

JURASSIC, CRETACEOUS, AND TERTIARY(?) 

SYSTEMS 

Rocks of Mesozoic and earliest Tertiary age are 

extremely scarce in the quadrangle, as they are in most 

of the region. Triassic and I ... ower Jurassic s~dimentary rocks are absent in the quadrangle, but they 

probably once covered the area and may have affected 

later deformation through their great load. Several 

monzonitic plugs were intruded into rocks of the 

adjacent ranges, 10-20 miles distant, during :Mesozoic 

and early Tertiary time. In the Connors Pass quadrangle tltere are some porphyritic rhyolite dikes that 

are of Mesozoic or Tertiary age, nnd a small fault 

block of shale and tuffaceous sandstone that is probably of Cretaceous or Paleocene age. 

PORPHYRITIC RHYOLITE 

There nre about 30 small rhyolite dikes in the 

Connors Pass quadrangle. Most are clustered within 

a fe'v square miles in the Taylor 'llining district, but 

three are east of Connors Pass and one is in Cooper 

Wash 2.5 miles north of the -Taylor district. An 

unexposed dike may lie half a mile to a mile east of 

the one in Cooper \Vash, for the colluvium there contains scattered fragments of a prophyritic rhyolite 

similar to that of the dikes. 

~1ost of the dikes are only a few feet wide and 

less than 200 feet long. Several are irregular in 

plan but most are tabular bodies. The longest dike 

extends for a mile nurthwestward from M!!jors Place 

and is uniformly 10 feet wide. In the Taylor district 

there are several dikes, one too small to be mapped, 

that paraJlel nearby normnl faults and are less sheared 

than some of the host rocks. 

The rocks of most of the dikes are incompetent and 

are poorly exposed in narrow belts largely covered 

with platy and blocky rubble. Several dikes near the 

south end of the Taylor district are better exposed 

along small ridges, but the northwest end of. the dike 

at Majors Place is marked by a band of white powdery 

material containing only a few fragments of porphyritic rock. 
52 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

Where it is least altered the rhyolite is very light 

gray to very pale orange, but where it is much .altered 

it is either white, pale red, or moderate reddish orange. 

The rhyolite usually has an earthy or chalky appearance, but in a few dikes it is subvitreous and in the 

southeast end of the dike near Majors Place it is 

slightly saccharoidal. Quartz veinlets cut the dike 

and the slaty host rocks near Majors Place. Quartz 

phenocrysts are in the rhyolite, and grains of biotite 

and feldspar can be seen where the rock is not much 

altered. 

Thin sections show that the rhyolite is all porphyritic, having a granular to obscure groundmass 

dominated by secondary minerals. Phenocrysts generally make up only about 5 percent of the rock and 

never more than 20 percent. Quartz phenocrysts constitute 1-6 percent, and plagioclase phenocrysts 1-5 

percent; the phenocrysts also commonly include a 

trace to 8 percent of potassium feldspar and as much 

as 2 percent of biotite. . The anorthite content of the 

plagioclase is Ano-35, but it generally cannot be determined because of the intensive alteration. In some 

specimens the potassium feldspar is sanidine, but in 

about half it consists of an undetermined potassium 

feldspar that is intergrown with quartz. Accessory 

magnetite ( ~), apatite, and zircon were observed in 

some specimens, and secondary quartz, sericite, clay 

minerals, and iron oxide are generally present. In 

some specimens the plagioclase is partially replaced 

by albite and sericite; in others it is alomst entirely 

replaced by sericite, kaolin ( ~ ) , and calcite. Some of 

the silica in the groundmass may be chalcedony. 

The chemical compositions of two samples of porphyritic rhyolite are listed in table 10. 

The porphyritic rhyolite dikes contain no glass and 

probably contained none prior to alteration; many are 

granophyric. These dikes, therefore, probably cooled 

more slowly and at greater depth than those associated with the volcanic rocks. They may be roughly 

contemporaneous with nearby stocks, as is apparently 

true of similar porphyritic rhyolite dikes in the 

southern Snake Range (Drewes, 1958) and in the 

Ward district of the Egan Range (A. L. Brokaw, oral 

commun., 1961). 

No measure of the absolute age of the di~es is 

available, nor is their relative age closely defined. 

The dikes intrude rocks as young as the Arcturus 

Formation, of Permian age, and fragments similar to 

the dike rocks-though probably derived from the 

Snake Range, as indicated by other components associated with these fragments-are included in the Eocene conglomerate west of Majors Place. The dikes 

are probably also older than some of the Tertiary 

TABLE 10.-Chemical and semiquantitative spectro- graphic analyses of porphyritic rhyolite 

[Elements looked for in spectrographic analyses but not found: Ag, As, 

Au, Bi, Cd, Ge, Hf, Hg, In, Ir, Mo, Os, Pd, Pt, Re, Rh, Ru, Sb, Ta, 

Te, Th, Tl, U, W, and Zn] 

Sample loc. (pl. 1) _ _ _ _ _ _ _ _ _ _ _ 1 

Lab. No____________________ H3186 

Chemical analyses 

[By C. L. Parker] 

Si02 _______________________ _ 

AJ203-----------------------

Fe203----------------------- FeO _______________________ _ ~gO ______________________ _ CaO _______________________ _ 

Na20 ______________________ _ ]{20 _______________________ _ 

H20+ ---------------------- H 20-______ ---------------- Ti02 ______________________ _ 

p 

~no 205------------------------ ______________________ _ C02 

_______________________ _ 

Cl ________________________ _ F _________________________ _ 

SubtotaL ____ --- ~ ____ _ Less 0 _______________ _ 

TotaL ______________ _ 

65.54 

11. 73 

. 40 

. 59 

. 45 

6. 83 

2. 47 

4. 19 

. 85 

1. 37 

. 05 

. 01 

. 19 

5. 06 

. 01 

. 12 

99. 86 

. 05 

99.81 

Semiquantitative spectrographic analyses 

[By P. R. Barnett] 

B _________________________ _ Ba ________________________ _ Be ________________________ _ Ce ________________________ _ Co ________________________ _ Cr ________________________ _ Cu ________________________ _ Ga ________________________ _ La ________________________ _ 

Li_~ _______________________ _ Nb ________________________ _ 

Nd Ni ________________________ ______ ~------------------_ 

Pb Sc ________________________ ______ ~------------------_ Sn ________________________ _ Sr _________________________ _ 

v-------------~------------ y _________________________ _ Yb ________________________ _ Zr ________________________ _ 

0 

. 03 

. 0003 

0 

0 

0 

0 

. 0015 

0 

. 015 

. 0015 

0 

. 0003 

. 003 

. 0007 

. 0007 

. 015 

0 

. 007 

. 0007 

. 003 

2 

H3187 

76.26 

12. 61 

. 25 

.44 

. 22 

.71 

3. 03 

4. 79 

. 52 

. 68 

. 05 

. 01 

. 05 

. 04 

. 01 

. 10 

99.77 . 04 

99.73 

0 

. 015 

. 0003 

0 

0 

. 00015 

. 00015 

. 0015 

0 

. 015 

. 003 

0 

0 

. 0015 

. 0007 

. 0007 

. 003 

0 

. 0015 

. 00015 

. 003 

volcanic rocks, because they were intruded at a depth 

greater than that at which the glassy volcanic plugs 

were emplaced, during a period when the region was 

steadily being exhp.med. If the correlation of the 

porphyritic dikes with the stocks in the adjacent 

ranges is accepted, the possible range in age may be 

further narrowed. Radiometric dates of some of the 

stocks described by Griggs, Whitebread, and Roberts 

(in Adair and Stringham, 1960, p. 231) range from 
TERTIARY SYSTEM 53 

Permian to Oligocene, and inasmuch as the dikes cut 

Permian rocks they are probably of Jurassic to Oligocene age. 

CRETACEOUS OR TERTIARY SYSTEM 

SHALE AND TUFFACEOUS SANDSTONE 

A sequence about 50 feet thick, made up of two 

layers of shale separated by a layer of tuffaceous 

sandstone, underlies a very small area along U.S. 

Highway 6-50-93 at the big bend 1.5 miles east of 

Connors Pass. The rocks are exposed in only one 

cut, slightly more than 200 feet long and less than 25 

feet high, on the north side of the road. If that cut 

had not been made, these rocks would not have been 

found, for the surface underlain by them is thickly 

covered with rubble from the adjacent Arcturus Formation. The rocks seem to lie in a thin fault block 

between outcrops of the conglomerate member of the 

Arcturus and outcrops of other Arcturus rocks. 

Dark-greenish-gray to greenish-black clay shale and 

mudstone 10 feet thick are in fault contact with 

underlying sandstone and chert-pebble conglomerate, 

presumably of the Arcturus Formation, and the shale 

encloses small blocks of similar chert-pebble conglomerate, probably faulted into or slumped onto 

parts of it. Faulted onto this shale is a very light 

gray tuffaceous sandstone about 25 feet thick· beds 

in this unit are 3-36 inches thick and are ~ently arched. The upper shale, which is interbedded with 

mudstone, rests conformably on the tuffaceous sand- . 

stone and also contains blocks of conglomerate. 

Plant remains that were collected, probably from 

one of the shale layers in the road cut, by Neal Smith 

and Fred Digert (written commun., 1959), were tentatively identified by D. I. Axelrod as: 

Sequoia fastigata (Sternberg) Heer 

Podozannites sp. cf. P. la!rweolatrus (Lindley and 

Hutton) Braun 

H eliconia sp. 

Oeraidiphyllum ellipticum (Newberry) Brown 

Axelrod dated these forms as Late Cretaceous or 

early Paleocene: The collection was referred to by 

Van Houten ( 1956, p. 2808). Estella Leopold tried 

in vain to find pollen in several samples of the shale 

and sandstone. 

TERTIARY SYSTEM 

BASALTIC ANDESITE VITROPHYRE 

A single dike of basaltic andesite vitrophyre intrudes the Ely Limestone low on the north wall of 

the upper pa,rt of Cave Creek. The dike is not exposed, but its presence is shown by a heavy local concentration of small fragments and blocks of darkgray igneous rock. The distribution of the blocks 

indicates that the dike is only a few feet wide, is less 

than 200 feet long, and trends northwestward along 

the valley wall. 

The rock is very dark gray to grayish black and 

has a very thin yellowish-brown coating on its weathered surface. Rounded inclusions of quartz 5-15 mm 

long are conspicuous but form only a small percentage of the rock. In thin section the rock is seen to 

contain 5 percent of phenocrysts and xenocrysts and 

about 35 percent of small crystals having trachytic 

texture, all in a glassy groundmass. The larger crystals are 2 percent labradorite phenocrysts and 1 percent each augite phenocrysts, magnesian orthopyroxene phenocrysts, and quartz xenocrysts. Of the small 

crystals, labradorite makes up about 15 percent of the 

rock, augite 10 percent, orthopyroxene 9 percent, and 

reddish-brown opaque material that may be iron oxide 

or an alteration product of olivine about 1 percent. 

The quartz is strongly resorbed by the glass, and the 

orthopyroxene has thin reaction rims of augite. The 

glass is very pale brown, is crowded with fine crystallities, and has an index of refraction of 1.533, appropriate for andesitic or basaltic glass. 

The abundance of unaltered glass indicates that the 

dike was emplaced at shallow depth and is comparatively young. In this respect the vitrophyre resembles the abundant volcanic rocks in the quadrangle 

more closely than it does the granophyric porphyritic 

rhyolite dikes. Fragments of similar but thoroughly 

weathered basalt or andesite are included in the basal 

conglomerate underlying the volcanic rocks of Eocene 

and Oligocene ( ~) age in this area. The dike of vitrophyre is probably a feeder of the oldest rock of the 

volcanic sequence but is probably not much older than 

the other rocks of that sequence. Its similarity in 

composition and in stratigraphic position to the basal 

member ( 1 a) of the Kalamazoo Volcanics of Young 

( 1960b), further north in the Schell Creek Range, 

indicates that they are correlative, but none of the 

local volcanics is of basaltic andesite. 

CONGLOMERATE 

Pale-reddish-gray conglomerate containing subordinate limestone and tuff occurs in lenticular bodies as 

much as 1,000 feet thick and rests unconformably on 

upper Paleozoic rocks. The conglomerate underlies 

about 3 square miles within the quadrangle, chiefly in 

six separate bodies alined slightly askew to the crest 

of the Schell Creek Range. A small amount of the 

conglomerate also occurs along the west flank of the 

range at the south end of the Taylor district. Sepa-
54 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

rate bodies of conglomerate lie on separate structural 

blocks, and many underlie a flow of quartz latite 

vitrophyre. . Slopes eroded on the conglomerate are 

gentle to moderately steep and are strewn with residual pebbles and cobbles in a reddish-gray or palereddish-brown to yellowish-gray soil. 

The best readily accessible exposures of this conglomerate are in the gullies tributary to Cave Creek 

from the south, but nowhe:re is a complete section 

well exposed. The thick body of conglomerate south 

of Cave Creek is divisible into two units, the upper 

one gray and only slightly indurated, and the lower 

one reddish gray and more indurated. Their contact 

is shown on the map by marker bed b. Conglomerate also occurs in smaller bodies that cannot be correlated with either unit. A thin limestone lens is 

mapped as marker bed a, and lenses of tuff are mapped 

as part of the conglomerate. 

The base of the conglomerate is poorly exposed 

where it overlies the Chainman Shale, but threequarters of a mile southwest of Cooper Canyon irregularities along its contact with the Arcturus Formation show that it rests on an old erosion surface of 

slight local relief. Here the upper 3 feet of limestone in the Arcturus Formation is broken and stained 

reddish brown, the color of the basal conglomerate. 

The relief on the unconformity beneath the conglomerate is much less than that on the present surface in 

this area, on which there is no reddish-brown soil. 

Beh een Cave Creek and Cooper Canyon the basal 

contact is a strongly angular unconformity, but elsewhere it is only slightly unconformable or merely 

disconformable. 

The conglomerate has indistinct bedding planes 

from several feet to 30 feet apart or it is massive; the 

fragments are poorly sorted except where there are 

small lenses of sandstone or roughly alined boulders 

(figs. 9, 10). Pebbles are generally dominant, cob--

bles are . common and locally dominant, and boulders 

are present here and there. The conglomerate has a 

sandy and silty matrix cont3ining much calcium 

carbonate and finely disseminated brown iron oxide. 

Boulders and cobbles are largely restricted to the 

lower 30 feet of the conglomerate just south of Cooper 

Canyon and to. the basal 200-400 feet of the conglomerate south of Cave Creek. The clasts are 

generally subangular to subrounded, but in places they 

are moderately well rounded. The degree of rounding 

of the clasts thus is intermediate between that in the 

conglomerate member of the Arcturus Formation and _ 

that in the younger clastic rocks except the lacustrine 

gravel. 

FIGURE 9.-Massive outcrops (foreground) of the lower unit of 

the Eocene conglomerate, a half mile southwest of Cooper 

Summit. View is southward toward peak having the Taylor 

bench mark at its summit. .. Ledges of Ely Limestone (PPM e) 

are in a klippe above the Chainman Shale (Me), which underlies the treeless bench around the peak. The crag in the 

middle of the skyline is underlain by the edge of a large plug 

of dacite vitrophyre (Tdi). 

- FIGURE 10.-Details of sorting, roundness, and size of clasts in 

the Eocene conglomerate, half a mile southwest of Cooper 

Summit. 

Most of the clasts consist of cherty fossiliferous 

limestone, derived from· the Ely Limestone and possibly from the Arcturus Formation, or of sandstone 

from the Rib Hill Sandstone and adjacent formations. 

Clasts of greenish-gray . quartzite, probably derived 

from the Chainman· Shale, and· of nearly white finegrained vitreous quartzite probably derived :from the 

Eureka Quartzite, ~re generally present but are 
TERTIARY SYSTEM 55 

nowhere abundant. There are some fragments of 

other kinds of rock : ( 1) on the east flank of the Duck 

Creek Range, Prospect Mountain Quartzite, Pole 

Canyon Limestone, and Upper Cambrian and Lower 

Ordovician limestone; (2) southwest of Majors Place, 

Prospect Mountain Quartzite, Pole Canyon Limestone, 

unmetamorphosed fossiliferous limestone from upper 

part of the Lincoln Peak Formation, unmetamorphosed and unsheared Upper Cambrian and Lower 

Ordovician limestone, granite or quartz monzonite, 

and altered porphyritic rhyolite. The granitic cobbles 

are more deeply weathered than similar rocks on 

alluvial fans at the foot of the southern Snake Range 

-an indication that the environment in which the 

Eocene gravel was deposited was different from the 

Pleistocene environment. The granitic rock consists 

of about 40 percent quartz, 35 percent slightly. granophyric orthoclase, 20 percent albite (An2_ 6 ), and 3 

percent muscovite. The upper unit of the conglomerate on both sides of Cave Creek contains some limestone fragments having nodules of a bluish-opaline 

material. Rare fragments of phyllite and one of 

granite were found on slopes underlain by conglomerate in the basin of Cooper Canyon. The conglomerate 

contains almost no fragments of volcanic rocks except 

in the tuff lenses. The middle part of the conglomerate wh-ere exposed on the south wall of the upper 

part of Cave Creek contains some fragments of 

weathered basaltic andesite, possibly derived from a 

dike similar to the one on the north valley wall. The 

conglomerate lenses south of Clear Spring contain a 

few cobbles and pebbles of a fresh tough dark-gray 

andesite vitrophyre of unknown source. This rock 

contains phenocrysts of hornblende and plagioclase in 

a glass having a refractive index of 1.518. 

Much of the red color of the conglomerate is imparted by the fragments from the Rib Hill Sandstone, 

but some may be derived from the red soil that 

appears to have underlain the conglomerate in places. 

The upper unit of the conglomerate is grayer, perhaps 

because the red soil had been stripped from the source 

area by the time this part was laid down, and also 

because it contains . fewer fragments of the Rib Hill 

Sandstone. 

One lens of limestone is interbedded low in the conglomerate on the east wall of the lower part of the 

South Fork of Cave Creek. It forms a ledge 1,500 

feet long and commonly about 10 feet thick hut as 

much as 30 feet thick in some places. The limestone 

is very finely crystalline, is yellowish gray to very 

pale orange, and has beds commonly 2-6 -inches thick. 

Some bedding planes are nodular and locally the top of 

the limestone contains a breccia of limestone flakes 

resembling fragments of those formed between mud 

cracks. 

Much tuff is interbedded with the conglomerate at 

Clear Spring, and south of Cave Creek more than a 

dozen lenses of tuff appear in the upper unit of the 

conglomerate. The largest lenses of distinctly tuffaceous rock are mapped as tuff lenses within the Eocene 

conglomerate. Tuff may also be mixed with the matrix 

of some of the conglomerate, but is thoroughly masked 

by other fine-grained clastic material. 

The tuff is gritty or sandy, rich in crystal fragments, and white, very light gray, yellowish gray, or 

pinkish gray. It is generally massive, but locally it 

contains some thin beds of well-sorted tuffaceous sandstone. In thin secticn, 20-25 percent of the tuff is 

seen to consist of crystals or crystal fragments; thus 

the rock is 6-10 percent quartz, 8-10 percent andesine 

near An45, 2-3 percent sanidine ( ~), and 2-4 percent 

biotite. Minor accessories are magnetite, zircon, 

sphene, apatite, and allanite. The rest of the tuff ( ~), 

consists of vesicular, partly devitrified glass, clay 

. minerals, cristobalite, and small amounts of lithic 

fragments, iron oxide, and chalcedony. The glass of 

one tuff body has an index of refraction of 1.503. 

The reddish-gray conglomerate is the first postPermian deposit in the area that contains evidence of 

source area, mode of transport, and conditions at the 

site of deposition. Most of the fragments were derived 

from rocks now exposed within the area, but the 

granitic cobbles are foreign to the area, and the lime~ 

stone in the conglomerate southwest of Majors Place 

is unmetamorphosed, whereas the nearest limestone 

in place is distinctly altered. The persistent scattered 

clasts of quartzite believed to be from the Eureka 

Quartzite probably came from outside the area of the 

present Schell Creek Range, for the Eureka has been 

eroded from only a small part of that area. The 

sizes of the -fragments and their degree of roundness 

and sorting also indicate that _ they came from distant 

sources, probably outside the quadrangle. 

Quantitative estimates of the distance of transport 

and the location of the actual source areas remain 

conjectural. Inasmuch as fragments now being deposited at the distal ends of fans 5-10 miles from 

the present range front are more angular than most of 

the clasts in the conglomerate, these subrounded clasts 

must have been carried farther than the fragments on 

the present fan~possibly two to three times as far. 

The combination of rocks represented by the fragments in the conglomerate near Majors Place is not 

now exposed at any place nearer than in the southern 

Snake Rano-e about 20 miles to the east. The northB' • h h 

ern Snake Range is one of the few areas in wh1c -t e 
56 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

Paleozoic rocks have been largely removed; it is also 

the largest of these areas and one of the nearest. The 

red conglomerate therefore presumably was derived 

largely from sources east of the Schell Creek Range, 

possibly in the Snake Range. 

That debris was probably carried by streams to an 

old piedmont area is indicated by the sorting and 

bedding of the deposits. There is no indication that 

the site of deposition had as much local relief as it 

has now, and there is some evidence south of Cooper 

Canyon that the surface beneath the conglomerate was 

deeply weathered and gentle in relief. Some relief is 

indicated by the great variations in the thickness of 

the conglomerate over short distances; not all of this 

variation can be the result of later erosion. The 

formation and preservation of the. weathered rinds 

on the granite or quartz monzonite cobbles indicate 

that deposition was less rapid or the climate was 

wetter than at present, these conditions perhaps affecting the red color in the conglomerate. The limestone 

lens was probably deposited in a lake, the life of 

which may have been terminated by desiccation, as 

indicated by the capping layer of curled limestone 

flakes. 

Inasmuch as the conglomerate is unfossiliferous, it 

cannot be dated exactly. From its general appearance 

and its relation to volcanic rocks of generally similar 

composition, it is tentatively correlated with the I\::insey 

Canyon Formation of Young (1960b, p. 163~164), 15 

miles to the north, and with either the conglomerate 

low in the Sheep Pass Formation of Eocene age or that 

low in the Garrett Ranch Group of Oligocene(~) age 

described by Winfrey (1960, p. 126-133), 30-50 miles 

to the southwest. Similar conglomerate appears in 

the Egan Range, just west of the quadrangle, and low 

in the White Sage Formation of Eocene ( ~) age (Nolan, 

1935, p. 42) , at the north end of the Deep Creek Range. 

If the correlation of the reddish-gray conglomerate in 

the Connors Pass quadrangle with that in the Sheep 

Pass Formation or with that in the Garrett Ranch 

Group or with that in the White Sage Formation proves 

valid, the conglomerate is of Eocene age and it is moro 

likely to be post-Eocene than pre-Eocene. 

QUARTZ LATIT'E VITROPHYRE 

The conglomerate just described is conformably overlain by glassy effusive quartz latite that underlies about 

1 square mile of the high area between Cave Creek and 

Cooper Canyon and also smaller areas north of Cave 

Creek. At each locality there is only one lava flow. 

The lava south of Cave Creek is about 300 feet thick, 

but at the other places it is much thinner. 

Most of this lava is very resistant and underlies sharp 

ridges and a mesa, but some of it underlies low knobs. 

The thick flow south of Cave Creek is polygonally 

jointed and forms a low cliff above an apron of blocky 

talus. On relatively flat areas the rock weathers to a 

grus interspersed with residual blocks. 

The basal15 feet of the flow, best exposed just above 

Summit Spring, is a gray breccia of glassy fragments 

in a grassy matrix. Most of the flow is pale reddish 

gray on fresh factures, but weathers brownish gray, 

pale reddish brown, or dusky reddish gray. It has a 

strong platy structure formed by alined, flattened, and 

stretched vesicles, which are commonly less than 2 inches 

long and make up 10-20 percent of the rock. Many of 

the phenocrysts of feldspar, biotite, and quartz also lie 

parallel to the platy structure. Near the top of the flow 

the rock is more· vesicular; and in places the flow layers 

are mammillary rather than platy. Small angular inclusions of tuff are locally abundant. 

Phenocrysts make up about 40 percent of. the rock 

and the groundmass is an unaltered or little altered 

flow-laminated glass. The proportions of the phenocrysts do not differ widely: 10-20 percent· of the rock 

consists of plagioclase phenocrysts, which have an 

anorthite content of An20-55 but commonly are only 

An35-48, 10-15 percent quartz phenocrysts, and 2-10 percent sanidine( ~) phenocrysts. The rock contains 0.5-1 

percent sphene and a very small amount of magnetite 

( ~), apatite, zircon, and allanite. Few of the phenocrysts are more than 4 mm long, and most are only about 

0.5 mm in diameter. The larger phenocrysts are generally subhedral or fragmental, but the smaller ones 

as well as the grains of accessory minerals are commonly 

euhedral. Quartz and, more rarely, plagioclase have 

the embayed or rounded shapes of partly resorbed 

crystals. 

The glass is very pale brown and contains abundant 

microlites. Its index of refraction has a narrow range, 

1.501-1.505, and is most commonly 1.502-1.504, a range 

that barely overlaps that of the glass of the other volcanic rocks. Most of the glass is replaced in small part 

by a radially fibrous mineral, and in some of the specimens it is almost completely devitrified. A small 

amount of cristobalite fills or lines vesicles in many 

speciments, and opal and chalcedony are also common. 

Throughout the report I present the full range of 

the anorthite content, as measured in all thin sections 

of a given mapped unit, such as the quartz latite vitrophyre flow. This range extends from the most sodic 

zone in one plagioclase crystaL to the most calcic zone 

in any other plagioclase crystal. Where there is abundant data, such as for the quartz latite vitrophyre 
TERTIARY SYSTEM 57 

(measurements were made on about 70 plagioclase 

crystals in 11 thin sections) , a second range of anorthite content is given to show the common composition 

of the plagioclase. 

The anorthite content was determined by measuring 

extinction angles of grains in which the ( 001) and 

(010) crystal faces are oriented normal to the stage, 

and by applying these results to the appropriate hightemperature curve for volcanic rocks or low-temperature curve for plutonic rocks, as given by Trager 

(1956, p. 111). 

Indices of refraction of glass were obtained by use 

of a sodium lamp and immersion oils calibrated to 

about 0.004:. These oils were mixed to about the nearest 0.001, and appropriate temperature corrections 

were applied. 

Chemical and spectrographic analyses of five specimens of quartz latite vitrophyre from the lava flow 

are presented in table 11. The analyses are so similar 

that the specimens could all represent a single flow. 

The quartz latite vitrophyre is probably only a little 

younger than the conglomerate, which is dated as 

Eocene. Zircon from this flow is given an age of 50 

millions years ±10 million years by lead-alpha radiogenic methods (T. W. Stern, written oommun., 1964). 

Most potassium-argon ages given of volca.nic rocks in 

eastern Nevada are slightly younger ( 30-40 my) and 

probably are more reliable. 

TABLE 11.-Chemical and semiquantitative spectrographic analyses of rocks from Egan Range (Shawe, 1961) and from Schell Creek Range 

[Spectrographic analyses of samples from localities 3--8 by P.R. Barnett, who reported to the nearest number in the series 7, 3, 1.5, 0.7, 0.15, and so forth, in percent. These numbers represent midpoints of group data on a geometric scale. Elements looked for but not found : Ag, As, Au, Bi, Cd, Ge, Hf, Hg, In, Ir, Mo, Os, Pd, Pt, Re, Rh, 

Ru, Sb, Ta, Te, Th, Tl, U, W, and Zn. In samples from Egan Range, Li also was looked for but not found] 

LocalitY--------------------------------- Egan Range 

Rock name_ ______ _____ ___ ___________ ____ Rhyolite 

Rock type ____ -------------------------- Welded tuff 

Sample loc. (pl. 1) _____________________ _ -------------- --------------

Lab No_--------------------------- ____ _ 

Si02------------------------------------- AhOa_ ------ __ -------------------------- Fe20a ___ ------------- ________ ___ ________ FeO _________ _____ ______________ __ __ __ __ _ 

MgO ------------------------ ____________ 

CaO __ ---------------------------------- Na20 ___ -------------------------------- K20 ___ _ -------------------------------- H20+ H20-_ ----------------------------------- --------____________________________ 

Ti02------------------------------------ P20 5- _ ----------------------------------

MnO __ __ ------------------------------- 002------------------------------------- CL ___ ---------------------------------- F ---------------------------------------

SubtotaL_--------------------------

Average 

of four samples 

69. 71 14.11 

1.12 

1. 41 

. 81 2. 85 2. 51 3. 84 1. 81 1. 00 

.45 

.10 

.05 

. 02 

.02 

.07 

-------------- Less 0 ---------------------------------- --------------

TotaL __ ---------------------------- --------------

Average 

of five 

samples 

71.44 

13.84 

1. 08 

1. 06 

.69 

2.49 

2.69 

4.29 

. 72 

. 67 

.39 

.10 

. 05 

. 01 

.02 

.08 

-------------- --------------

--------------

Schell Creek Range 

Quartz latite vitrophyre 

Lava flows 

3 4 - 5 

H3179 H3180 H3181 H3182 

Chemical analyses 

72.13 70. 60 71.85 70.64 

13. 36 14.26 13.71 13.99 1. 06 1. 26 1. 22 1.11 1. 06 1. 06 . 99 1.13 

. 66 . 70 . 72 . 70 2.40 2.39 2. 56 2. 59 2. 78 2.33 2. 81 2. 71 4. 01 4. 82 4.05 4.39 

. 79 1. 00 . 61 . 77 . 62 . 70 . 59 .64 .37 . 41 .39 . 41 . 20 . 01 .09 .11 .09 .06 .04 .04 . 01 .01 .00 .01 .02 .02 .02 .02 . 08 . 08 . 07 .08 

99.64 99.71 99.72 99.34 .03 .03 .03 . 04 

99.61 99.68 99.69 99.30 

~miquantitative spcctrograpltic analyses 

B--------------------------------------- 0 0 0 0 0 0 

Ba_ ------------------------------------- .19 .07 .07 .07 .07 . 07 Be __ ----------------------------- _______ . 00015 . 00018 . 00015 . 00015 . 00015 .0003 

Ce __ ----------------------------- ------~ .023 .018 . 015 .015 .015 .03 Co ___________________________________ ___ . 0003 .0003 .0003 .0003 .0003 .0003 

Or __ ------------------------------------ .0003 . 00015 . 00015 . 00015 . 00015 .00015 Cu ______________________ ________________ . 0003 .00027 .0003 ; 0003 .0003 .0003 Ga _________________________________ _____ .0009 .0015 .0015 . 0015 . 0015 .0015 La __________________________ -----------_ . 011 .009 .007 . 007 .007 .015 

Li._------------------------------------- 0 0 0 0 0 0 Nb -------------------------------------- . 0019 .0015 . 0015 . 0015 .0015 .0015 Nd -------------------------------------- . 009 .004 0 0 0 .015 

NL __ ----------------------------------- <.0003 . 00006 0 0 0 0 

Pb-------------------------------------- .0009 .0015 .0015 .0015 .0015 .0015 Sc _______________________________________ .0007 . 0007 . 0007 .0007 .0007 .0007 

Sn ____ --------------------------------- _ 0 0 0 0 0 0 Sr _______________________________________ .06 .07 .07 .07 . 07 .07 

v--------------------------------------- . 004 .003 .003 .003 .003 .003 

y--------------------------------------- . 0023 .0015 .0015 . 0015 .0015 .0015 

Yb-------------------------------------- . 00023 . 00015 . 00015 . 00015 . 00015 . 00015 Zr _______________________________________ .019 . 015 • 015 . 015 .015 . 015 

H3188 

71.97 

13.88 . 77 1. 06 

.66 

2.50 

2. 83 4.17 

. 45 

. 79 

.38 

.09 

. 04 

. 01 

.01 

.07 

99.68 

.03 

99.65 

0 

.07 

.00015 

. 015 

.0003 

. 00015 

.00015 

.0015 

.007 

0 

.0015 

.007 

.0003 

.0015 

.0007 

0 

.07 

.003 

.0015 

. 00015 

. 015 

Egan Range 

Rhyolite 

Intrusive 

8 

H3178 

75. 89 13. 10 

. 30 

.36 

.10 

. 86 3. 51 4. 69 

.32 

.42 

. 05 

. 02 

. 06 

. 01 

.01 

.13 

99.83 .05 

99.78 

0. 0015 

.007 

.0003 

0 

0 

.00015 

. 00015 

.003 

0 

. 015 

.003 

0 

0 

.003 

.0007 

.0007 

.007 

0 

.003 

.0003 

.007 

Average 

of four samples 

73.47 

13.56 

.45 

.32 

.09 

.90 

3. 50 4.89 

2.20 

.21 

.05 

.03 

.08 

.01 

.02 

.12 

-------------- --------------

---·----------

0.0011 

.003 

.0003 

0 

0 

<.0003 

<.0003 

.0023 

0 

0 

.003 

0 

0 

.003 

.0003 

.0007 

.003 

0 

.003 

.0003 

.005 
58 GEOLOGY, . CONNORS PASS QUADRANGLE, NEVADA 

Welded tuffs of somewhat similar chemical and 

mineral composition from the Egan Range were described by Shawe (1961, p. 178-181); analyses of them 

(table 11) show that the quartz latite vitrophyre flows 

of the Schell Creek Range ·resembled the welded tuff 

to the west in the Egan Range more closely than that 

tuff resembles the intrusive rhyolite in the Egan Range, 

also described by Shawe. The chemical similarity 

between the intrusive rhyolite described by Shawe and 

the intrusive quartz latite vitrophyre is even more 

impressive. 

LATITIC ROCKS 

The flows of quartz latite vitrophyre are confonnably overlain by a thick sequence of tuff. Two small 

lenses of welded tuff and two intrusive bodies of vitrophyre and a lava flow compose the formation that 

underlies an area of about 1 square mile near Cooper 

Summit and a small area half a mile northeast of 

Cave Creek Reservoir. The tuff forms gentle to moderately steep slopes between the more competent lava 

flows, these slopes being so thickly strewn with blocks 

of tuff and other volcanic rocks that outcrops are few. 

The tuff is best exposed along the road 1 mile south 

of Cooper Summit. 

The tuff is almost everywhere a massive, blockyweathering, very light gray rock, but locally it forms 

rounded bosses having pitted surfaces. It consists predominantly of fine-grained volcanic ash and 20-35 

percent of crystals and crystal fragments, but near 

the south end of the quadrangle it also contains 20-30 

percent of small lithic fragments, as much as 4 inches 

in diameter, of glass, vitrophyre, and white tuff. The 

vitrophyre fragments Tesemble the quartz latite more 

closely than they do the overlying dacite. 

The tuff contains 8-15 percent plagioclase crystals, 

which have a composition range of An33-48, 2-7 percent sanidine ( ~), 6-20 percent partly resorbed quartz, 

and 2-3 percent biotite. The accessory minerals include sphene, which is abundant, and magnetite( n' 

zircon, apatite, and allanite, which are all scarce. 

Shards of vesicular glass are abundant and some 

pumiceous fragments are also present. The index of 

refraction of. the glass is 1.492-1.501-mostly lower 

than, but slightly overlapping, the range in the quartz 

latite vitrophyre flow. Devitrified glass and clay alteration minerals obscure much of the groundmass. 

WELDED TUFF LENSES 

Two lenses of welded tuff lie at or just above the 

base of the latite tuff. One is well exposed on the 

ridge west of the road about a mile south of Cooper 

Summit, and the other is poorly exposed three-quarters 

of a mile northeast of Cave Creek Reservoir. The lens · 

south of Cooper Summit is scarcely half a mile long 

and 100 feet thick, and it apparently grades· in all 

directions into normal tuff. The rock has a strong 

platy parting and contains flat vitrophyre inclusions, 

both parallel to the bedding. · The lens thins gradually northward and is ~ probably continuous with a 

layered well-indurated tuff unit about 15 feet thick, 

which lies about 50 feet above the base of the latite 

tuff. Although the vitric fragments which make up 

most of the layered tuff are not markedly elongate like 

those in the welded tuff, some are subrounded and have 

concentric flow structures, these features suggesting 

that the fragments are slightly flattened clots or volcanic bombs. The layered tuff also contains devitrified 

glass, opaline vein material, and numerous fragments 

of phenocrysts. The fragments and crystals are 

crushed in some places, especially where they are in 

contact with one another. 

The mineral composition of the welded tuff .is iden-

. tical with that of the surrounding tuff and much like 

that of the quartz latite flow. The refractive index 

of the glass is 1.494-1.500. In thin $ection many of 

the glassy fragments are seen to be spindle shaped, the 

ratio of length to thickness ranging from 5: 1 to 10: 1. 

Some large glass fragments have a faint perlitic fracture that is not common in the other vitrophyres of 

this area. 

INTRUSIVE BODIES OF QUARTZ LATITE VITROPHYRE 

The latite tuff is cut by two small bodies of quartz 

latite vitrophyre. One of these underlies an elliptical 

area at Cooper Summit. Its shape and the absence of 

nearby faults indicate that it· is intruded, rather than 

faulted, into the tuff. The rock is about 50 percent 

phenocrysts in a strongly flow -laminated glassy 

groundmass. Plagioclase phenocrysts ( An45-4s) make 

up 30 percent of the rock, and phenocrysts of quartz, 

biotite, and hornblende, 8, 6, and 4 percent, respectively; the accessories are sphene, magnetite( n' apatite, and . allanite. The · refractive index of the glass 

is 1.501. Mineralogically, then, this intrusive rock 

closely resembles the quartz latite vitrophyre of the 

flows except for the pr~ence of hornblende and the 

absence of potassium feldspar phenocrysts; in these 

respects the rock is transitional with the younger 

dacite flows; 

A small area near the mouth of the canyon of 

Cooper Wash also is underlain by quartz latite vitrophyre that seems to be intrusive. Near the north and 

east edge of this body there are some steeply inclined 

peripherally striking flow laminae and some coarse 

vitrophyre breccia and agglomerate. Most of t~e 

petrographic features . of this body of quartz latite 
TERTIARY SYSTEl.\1: 59 

vitrophyre are like those of the lava flows beneath the 

latite tuff, but the groundmass is partly cryptocrystalline, and the refractive index of the remaining glass 

can only be determined to two significant figures a£ 

1.51. Alteration to clay minerals is moderately intense, but is much less than in the dikes of porphyritic 

rhyolite. 

The intrusive quartz latite vitrophyre rock (table 11) 

differs slightly in chemical composition from the associated extrusive rock. It contains significantly more 

silica, soda, and fluorine, and less lime, total· iron 

oxides, magnesia, and water. The ch3mical and possibly also the petrographic differences may be related 

to the greater alteration of the intrusive rock than of 

the extrusive rock, these relations indicating that posteruption fluids may have issued from the vent. It is 

possible, however, that the composition of the latite 

magma differed from place to place. 

UPPER LAVA FLOW OF QUARTZ LATITE VITROPHYRE 

At the mouth of Cooper Wash a thick body of 

latite tuff is apparently overlain by a lava flow that 

so:rnewhat resembles the quartz latite vitrophyre flow 

beneath the tuff at Cave Creek, but which contains a 

greater abundance and variety of silica minerals, is 

brecciated, and is affected by a pervasive clay-mineral 

&Iteration. There are. several possible correlations between it and the volcanic rocks along Cave Creek. It 

seems most likely that the tuff bodies are contemporaneous and the lava flow slightly younger, for quartz 

latite cuts the tuff in both places, and the spreading 

of tuff is less restricted by topography than is the 

spreading of lava flows. The vitrophyre agglomerate 

between the quartz latite vitrophyre intrusive body 

and the tuff along Cooper Wash indicates that the intrusive body may ·he a plug in the vent from which 

the tuff was ejected, which is perhaps also the vent 

of the younger flow. Regardless of· the details of the 

relations between them, the tuff and the quartz latite 

vitrophyre rocks seem to be genetically associated and 

of nearly the same age. 

ENVIRONMENT, AGE, AND CORRELATION 

The initial period of ma]or volcanism, which began 

in this area with small outbursts of tuff and continu~d 

with the extrusion of ·the quartz latite vitrophyre 

flows, culminated with a large explosive outburst that 

deposited a thick blanket of tuff over a large area. 

Some of the tuff was erupted early and· was welded, 

but, judged from the slight deformation of the glassy 

fragments and the presence of unoxidized biotite, the 

welding. was not intense and the temperature was not 

very high. Some of the glassy bombs that were deposited at the horizon of the welded tuff body and 

just beyond its edge apparently were so soft that they 

flattened slightly under the weight of the rapidly accumulating mantle of tuff; some of the more rigid 

fragments and phenocrysts were crushed under this 

pressure. The welded tuff may have been formed in 

a similar manner from a larger accumulation of hot 

viscous glassy fragments that were under moderately 

high lithostatic pressure. Regardless of origin, the 

welded tuff bodies differ from the extensive sheets of 

welded tuff studied elsewhere in this part of the Great 

Basin by Mackin ( 1960) and Cook ( 1960) in that they 

are extremely local. Near the end of this large explosive outburst, or just after it, a latite magma having 

slight dacite affinities intruded some of the tuff and 

locally poured out over it. 

Biotite from the intrusive body of quartz latite 

vitrophyre near the mouth of the canyon of Cooper 

Wash has been dated by the potassium-argon method 

as 38 million years ( ± 10 percent) ( S. S. Goldich, written commun., 1964) . This determination confirms an 

Eocene age, and probably indicates a late · Eocene age. 

The sample was collected at sample locality 8 (pl. 1). 

The tuff does not seem to have any correlative in 

the Kalamazoo Volcanics of the northern ·schell Creek 

Range, except possibly an unanalyzed tuff. In the 

Egan Range, however, Shawe (1961) described a 

welded tuff that resembles in phenocrysts and chemical 

composition the lava flows believed to be associated 

with the welded tuff in the Cave Creek area. 

DACITE VITROPHYRE 

Some of the youngest volcanic rocks in the area lie 

conformably on the latite tuff or on the conglomerate 

of Eocene age, whereas .some lie unconformably on 

rocks of late Paleozoic age or are intruded into upper 

Paleozoic rocks. These youngest volcanics have the 

chemical and mineral composition of dacite and a 

vi~rophyric texture, but are varied within these limitations; I may therefore have mapped rocks of somewhat different age and origin as dacite vitrophyre. 

East of Cooper Summit the dacite vitrophyre consists 

of three flows, separated by thin layers of tuff, that 

are altogether more than 1,200 feet . thick; elsewhere 

it also includes dikes and volcanic necks. The flows, 

tuff, and intrusive rocks are distinguished on the map, 

however, as separate units of the dacite vitrophyre. 

Dacite vitrophyre underlies many small areas, which 

have a combined extent of about 3 square miles. Most 

of these areas lie between the upper part of ~teptoe 

Creek and Majors Place; others ·lie on the west flank 

of the Schell Creek Range south of the Taylor district, 

and one is Rattlesnake ·Knoll, in Spring Valley .near 

U.S. Highway 6-50. 
60 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

The flows of quartz dacite vitrophyre differ greatly 

in topographic .expression: they form high steep ridge 

crests east of Cooper Summit, gently rounded hills 

south of Cooper Canyon, and gentle piedmont slopes, 

hardly distinguishable from the adjacent gravel-covered slopes, southwest of the Taylor district. The 

steep slopes are covered with colluvium and blocky 

talus, but the gentler ones are mantled with grus and 

scattered residual blocks. 

Fresh surfaces of quartz dacite vitrophyre are medium gray to grayish red, and the weathered surfaces 

are moderate yellowish brown, moderate brown, pale 

reddish brown, to brownish black. The fresh rock is 

generally darker than the quartz latite vitrophyre. 

The dacite is slightly vesicular, and the more competent rock has a platy parting. Roughly polygonal 

joints stand at right angles to the parting and partly 

cause weathering of the dacite into blocks. Where 

blocks are abundant and outcrops are absent, as in 

some places southwest of the Taylor district and just 

south of Cooper Canyon, the source of the blocks may 

be an agglomerate body. Phenocrysts of feldspar, 

biotite, and hornblende are common, and in places 

there are also phenocrysts of quartz. In some places 

the dacite flow includes fragments of sedimentary 

rocks, and of igneous rocks resembling the dacite. 

The only place where inclusions of sedimentary 

rocks are especially common in the dacite vitrophyre 

is at Rattlesnake Knoll. The inclusions are subangular to subrounded and range in size from grit to 

blocks 12 inches across although most are only 1-2 

inches across. They are scattered in an igneous matrix, 

and in places they are roughly sorted into layers 

parallel to the nearly flat lying partings. The fragments consist of quartzite, rhyolite, fine-grained and 

recrystallized massive limestone, shaly limestone, and 

phyllite, all common in the alluvial fans in this area 

as well as in some of the fans on the east side of 

Spring Valley. The nearly horizontal position of the 

partings, the size sorting of some fragments, and the 

great variety of the fragments, seem to indicate that 

this dacite vitrophyre is a lava flow that picked up 

debris from the surface of an underlying fan. 

The abundance of the phenocrysts is widely varied 

-from 15 to 50 percent. The relative abundance of 

different kinds of phenocrysts is also widely varied: 

plagioclase phenocrysts ( An35•50, common range; 

An2s-95, extreme range) make up 8-25 percent of the 

rock, quartz 0-15 percent, biotite 0-8 percent, hornblende 0-5 percent, augite 0-3 percent, and hypersthene 0-5 percent. The groundmass is generally 

glassy, but in some specimens it is cryptocrystalline. 

In a typical specimen, andesine phenocrysts make up 

20 percent of the rock, quartz phenocrysts 10 percent, biotite 5 percent, hornblende 3 percent, and 

augite 1 percent. The accessory minerals include 

sphene, magnetite ( ~), apatite, zircon, and allanite. 

The dacite differs from the latite by its complete lack, 

among the phenocrysts, of potassium · feldspar, its 

occasional lack of quartz and biotite, its greater abundance of hornblende, and its content of augite and 

hypersthene. 

The characteristics of the phenocrysts also vary 

widely. Most of them are less than 2 mm in diameter but some are more than 4 mm. The plagioclase 

crystals are commonly subhedral or fragmental, and 

some are embayed or rounded by resorption. Normal 

zoning, oscillatory zoning, and, in one specimen, reverse zoning occur in the plagioclase. The range of 

composition between zones in most of the plagioclase 

phenocrysts is small, but in several specimens the anorthite content between zones varies more than 15 

percent. The quartz phenocrysts are generally fragmental, and many of them are embayed or rounded 

by resorption. Biotite and hornblende are commonly 

subhedral to euhedral phenocrysts, most of which are 

sheathed with iron oxide particles and thus are 

slightly oxidized, but a few of which are altered to 

oxyhornblende and oxybiotite and thus are intensely 

oxidized. Some of the hornblende is slightly altered 

to actinolite or to chlorite and calcite, and some of the 

biotite is replaced by epidote, sericite, and iron oxide. 

A few grains of biotite have reaction rims of hornblende. Augite and hypersthene are commonly euhedral. 

The groundmass is a banded clear to pale-brown 

glass, which contains a few microlites and some pockets of devitrified glass. The index of refraction of 

the glass is commonly 1.508-1.513, but in one specimen it is 1.501. Some of the groundmass contains a 

little cristobalite and is pervasively altered to clay 

minerals. 

Chemical analyses of eight samples of dacite vitrophyre are shown in table 12, and the places where 

they were collected are shown on the geologic map 

(pl. 1). The resultS of the analyses are very similar, 

and as a group the analyses are distinct from those 

of the quartz latite vitrophyre shown in table 11; 

there is more variation, however, within the dacite 

samples than within the latite samples. 

INTRUSIVE ROCKS 

The intrusive bodies of quartz dacite in the Connors Pass quadrangle range from dikes about 100 

feet long and 30 feet wide to a volcanic neck southeast of Crethers Springs that is about three-quarters 
TERTIARY SYSTEM 61 

TABLE 12.-Chemical and semiquantitative spectrographic analyses of dacite vitrophyre 

[Chemical analyses by C. L. Parker .. Looked for in spectrographic analyses but not found: Ag, As, Au, B, Bi, Cd, Ge, Hf, Hg, In, ~i, Mo, P?, Pt, Re, Sb, Sn, Ta, Te, Th, 

Tl, U, W, and Zn. Spectrographic analyses of samples 9, 10, 11, and 14 by P. R. Barnett, who reported to the nearest number m the senes 7, 3, 1.5, 0.7, 0.3, and 0.5 in percent, and also looked for, but did not find: Ir, Os, Rh,: and Ru. Spectrographic analyses of samples 112, 13, 15, and 16 by J. C. Hamilton, who reported to the nearest number in the series 1, 0.7, 0.5, 0.3, 0.2, 0.15, and 0.1 (which represent approximate midpoints of group data on a geometric scale). About 30 percent of amounts deter- mined present by semiquantitative spectrographic analyses agree with amounts determined by chemical analyses] 

Rock type ____ -------------------------- Intrusive 

Sample loc. (pl. 1) ----------------------- 10 11 12 

Lab. No_ - ------------------------------ H3177 H3185 H3184 H3660 

Lava flows 

13 14 

H3661 H3183 

15 

H3658 

16 

H3659 

Average of 8 sample~ 

Chemical analyses 

SiO _ ----------------------------------- __ 67.83 67.31 66.03 63.01 69.73 65.41 66. 71 67.67 66.71 

AbO a----------------------------------- 14.64 14.81 15. 17 15.17 14. 17 15. 10 14.97 14.53 14.82 

Fe20a _ ---------------------------------- 2. 27 3.11 3.16 3.25 2.69 2.24 2. 41 1. 59 2. 59 FeO _____ ------ _____________________ _____ 1. 72 . 80 1.36 1.62 . 64 2.16 1. 70 1. 80 1. 48 MgO --- _ ------ ______ -------------------- L 19 1.11 1.23 1.85 . 82 1. 37 1.26 1.04 1. 23 

CaO ___ --------------------------------- 3. 75 3. 30 3. 76 4. 97 2. 98 4.14 4.18 3.08 3. 77 

Na20 _ ---------------------------------- 3. 01 2. 91 2. 99 2. 71 2. 94 2. 91 3.06 2. 94 2. 93 

K20------------------------------------ 3.40 3. 84 3. 42 2. 98 3. 98 3. 42 3.45 3. 75 3. 53 H20+- ___ ------------------------------ . 47 . 53 . 53 1. 99 .47 1. 37 .32 2. 06 • 97 

H20------------------------------------ . 51 1.08 1.02 . 64 . 60 .26 . 42 .20 . 59 Ti02- _____ ----- _ --- _____________ --- _---- . 60 . 63 . 70 .77 . 53 .72 . 70 . 56 . 65 

P20s- _ ---------------------------------- .16 .16 . 20 .22 .14 .23 . 21 .14 .18 MnO ___ -------------------------------- . 09 . 05 .12 .09 .03 . 08 . 08 .07 .08 

002------------------------------------- . 05 .00 . 01 . 32 . 01 .17 . 30 . 01 .11 CL _________ ---------- ___ ---- ____________ . 02 . 02 . 01 -------------- -------------- . 03 -------------- -------------- -------------- F--------------------------------------- . 08 .08 .07 -------------- -------------- .06 -------------- -------------- --------------

----- SubtotaL __ ------------------------- 99.79 99.74 99.78 99.59 99.73 99.67 99.77 99.44 99.64 

Less 0---------------------------------- . 03 . 03 . 03 -------------- -------------- . 04 -------------- -------------- --------------

Total_------------------------------ 99.76 99.71 99.75 -------------- -------------- 99.63 -------------- -------------- --------------

Semiquantitative spectrographic analyses 

Ba ____ --------- _________________________ 0.15 0.07 0.07 Be ______________ ___ _____________________ . 00015 . 00015 . 00015 Ce _______________ ___________ __________ __ . 015 . 015 . 015 Co ______________________________________ .0007 . 0007 . 0007 Or ______________________________________ . 0015 . 0015 .0007 Cu ______________________________________ . 0003 . 0003 . 0003 Ga ______________________________________ . 0015 . 0015 . 0015 La __ ----------- _________________________ . 007 .015 . 007 Nb __ ---------- ____________________ ------ . 0015 . 0015 . 0015 N d. _______________ --- _______________ - _-- . 007 . 007 . 007 

NL _ ------------------------------------ . 0007 . 0015 0 Pb ______ --- _______ --- ___________ --- ___ -- . 0015 . 0015 . 0015 Sc ___ -------------- ______________________ . 0015 . 0015 . 0015 Sr ___ ------ ______________________________ . 07 . 07 . 07 

v--------------------------------------- .015 .007 .007 

y--------------------------------------- .003 . 0015 . 003 Yb __ --------------- _______ ---- ____ --- ___ .0003 . 00015 .0003 Zr ___ --------- ___________________________ .015 . 03 .03 

of a mile in diameter. Most of them are clustered 

just south of Cooper Canyon. Intrusive contacts, 

chilled margins, and steeply inclined peripheral flow 

structures oan be seen along the margins of most of 

these bodies. Many of the intrusive bodies are on the 

north-trending faults. The rocks of a few are moderately altered. Similarly altered bodies without 

structural evidence of intrusion occur in this area, 

but these may only have boon volcanic rocks penetrated by gases escaping through vents. 

The physical and chemical properties of the less 

altered intrusive rocks differ little from those of the 

flows. The index of refraction of glass from chilled 

margins is 1.510-1.513. The more altered rocks, however, are very light gray and are thoroughly fractured. Their groundmasses are cryptocrystalline and 

are pervaded with clay minerals. The plagioclase 

crystals are not albitized, as are some of those in the 

older porphyritic rhyolite dikes. 

240-303 0 - 67 - 5 

0. 1 0.1 0. 07 0.15 0.1 0. 95 . 00015 . 0002 . 00015 . 0002 .0002 . 00017 .02 .02 . 015 .02 . 015 . 017 .001 .007 . 0007 . 001 . 001 . 0019 .0007 . 0007 .0007 . 001 .0007 . 0009 . 001 . 001 .0003 . 0005 . 0007 . 0006 .002 . 003 . 0015 . 003 .003 . 0021 . 007 . 015 . 007 . 01 . 007 . 009 .002 . 002 . 0015 .002 . 002 . 0018 < . 01 . 015 .007 . 015 <.01 -------------- 0 0 0 0 0 .0003 .002 .002 . 0007 . 003 .002 . 0018 . 0015 . 001 . 0015 . 0015 . 001 . 0014 .07 . 07 .07 .07 . 05 .07 . 01 .007 . 007 . 01 . 007 .0088 .003 .003 .003 .003 . 003 .0028 .0003 . 0005 . 0003 .0005 .0003 .0003 .02 .02 .03 .05 . 015 .026 

The large intrusive neck southeast of Crethers 

Springs is nearly circular in plan and consists of two 

kinds of rock. Along the west and north sides of 

the neck the rock is unaltered and highly competent, 

and it there underlies a rugged crescentic ridge. 

Along the west side, where the contacts are locally 

very steep, a wide-chilled margin and a peripheral 

breccia zone contain fragments of volcanic rock and 

of upper Paleozoic sedimentary rock. Strong joints 

dipping 35 °-65 ° outward indicate that, aside from the 

local steep exposures, the contact dips inward as in a 

funnel. The core and south and east sides of the 

neck, however, are underlain by moderately altered 

incompetent rock. On these sides the contact is unexposed, but across one steep canyon on the northeast 

side it appears to be stoop or to incline inward. The 

altered rock grades into the unaltered rock, and in 

places it encloses unaltered rock. 
62 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

Half a mile south west of this large neck there is an 

intrusive body less than 300 feet wide and elliptical in 

plan. The rock of this body is pale purple to reddish 

gray, fine grained, and very brittle, being closely fractured in a radial pattern. This rock consists mainly 

of devitrified glas~ containing less than 2 percent 

andesine phenocrysts and accessory minerals. 

TUFF LENSES 

Two thin unexposed tuff lenses that separate flows 

of dacite vitrophyre east of Cooper Summit are 

mapped with the dacite vitrophyre. Poorly exposed 

tuff and tuffaceous sandstone that underlie the dacite 

vitrophyre flow just west of the townsite of Taylor 

are also mapped with it because of their mineralogic 

affinities with the dacite. They contain oxyhornblende 

and augite but no sphene; the refractive index of the 

glass is 1.508. 

ENVIRONMENT, AGE, AND CORRELATION 

The wide distribution of remnants of dacite vitrophyre and the still wider distribution of dacite fragments in the younger gravel units indicate that the 

dacite flows once covered a large area. After the 

more explosive phase of eruption, during which latite 

tuff was ejected, a less silicic magma was brought to 

the surface through vents that were partly in normal 

fault fissures. The largest intrusive body may be 

the root of a large volcano, and the others may be the 

roots of satellite cones. 

Biotite from the upper of the flows east of Cooper 

Summit has been dated by the potassium-argon radiogenic method as 36 million years ( ± 10 percent) 

(S. S. Goldich, written commun., 1964). This age 

would probably indicate that the rocks are late Eocene, hut some may be younger ; they are here assigned an Eocene and Oligocene(?) age. The sample was collected along the jeep trail about 200 feet 

south of the saddle three-quarters of a mile east of 

Cooper Summit. 

Winfrey ( 1960) reported a radiogenic age of 34 

n1illion years from similar volcanics above the Eocene 

Sheep Pass Formation, and Armstrong ( 1963) reported additional ages of 30 million years and 36 

million years from these rocks. The rock is also 

similar to some of the flows in the poorly dated Kalamazoo Volcanics of Young ( 1960b) , in the northern 

part of the Schell Creek Range, and to the dacite flow 

at the south end of the Snake Range (Drewes, 1958). 

FANGLOMERATE 

A gray poorly indurated cobble fanglomerate at 

least 600 feet thick is exposed between Cooper Canyon and U.S. Highway 6-50-93. It lies unconformably upon a dacite vitrophyre flow, the Eocene reddish-gray conglomerate, the Ely Limestone, and the 

Arcturus Formation. The· fanglomerate is inclined 

almost as steeply as the underlying Eocene conglomerate and is faulted against limestone of Late Cambrian or Early Ordovician age. Slopes on the fanglomerate are gentle to moderately steep and are 

mostly covered with residual gravel, but the fanglomerate is exposed along some gullies and in a 

few small ledges on the steeper slopes. 

The fanglomerate consists mainly of angular to 

subangular poorly sorted cobbles and boulders in a 

sandy matrix, but it includes some interbedded tuffaceous sandstone and pebble conglomerate. It is 

thick bedded, and in some exposures it shows no 

bedding. Most of the cobbles in it are derived from 

sheared Upper Cambrian and Lower Ordovician 

cherty limestone and from the Middle Cambrian Pole 

Canyon Limestone, which is slightly metamorphosed 

as it is in the exposures immediately to the east. To 

the north, where the fanglomerate is finer grained 

than it is generally elsewhere, it contains some pebbles of upper Paleozoic limestone. 

The poor sorting and rounding of the fragments 

indicate that they are derived from a nearby source; 

this source must have been to the east, for elsewhere 

the rocks from which the fragments are derived are 

still covered by younger Paleozoic rocks. 

In general character, and in its stratigraphic and 

structural relations to adjacent formations, the fanglomerate is comparable to the North Creek Formation of late Tertiary and Quaternary age of Young 

( 1960b) in the northern Schell Creek Range. A Pliocene ( ? ) age is tentatively assigned to the fanglomerate. 

QUATERNARY SYSTEM 

Quaternary gravel, sand, and silt. underlie extensive areas of Spring Valley and Stept<;>e Valley and 

very restricted areas along the larger valleys within 

the Schell Creek Range. They are divisible into 

lacustrine deposits and alluvial gravels. The gravels 

are further divisible into three units, the youngest of 

which differs only slightly in distribution and character from the most recent deposits along the drainages. 

OLDER ALLUVIAL AND FAN GRAVEL 

In both Spring and Steptoe Valleys, there are d~­

posits of gravel at least 200 feet thick, which underhe 

high relatively smooth slopes, incised by widely spaced 

gullies that have gently sloping sides and narrow bottoms. Most of the larger areas in which this gravel 

occurs lie close to the fronts of the Schell Creek 
QUATERNARY SYSTEM 63 

Range and extend up into its larger valleys. Except 

in one area near Cleve Creek, the erosion surfaces on 

this gravel slope more steeply toward the centers of 

Spring Valley and Steptoe Valley than the surfaces 

of the younger gravel deposits do, and at moderate 

distances from the Schell Creek Range this gravel is 

commonly overlapped by younger deposits. Close to 

the range fronts it is also overlapped by a thin apron 

of gravel that is generally unmapped. 

The deposits beneath the mature high piedmont surfaces consist mainly of angular to subangular poorly 

sorted pebbles and cobbles but contain scattered boulders and bouldery lenses, all in a sandy, silty, and 

limy matrix. Boulders are most common to the northeast, as they also are in the younger deposits, but 

throughout the area the older gravel is coarser than 

the nearest deposits of younger gravel. The difference is most striking at the mouth of Cooper Canyon, where the older gravel contains scattered blocks 

of Eureka Quartzite as much as 10 by 10 by 15 feet 

in size, whereas the younger gravel contains few 

blocks as much as a foot long. The older gravel is 

only slightly indurated, though remnants of caliche 

rest upon it in many places . 

The older gravel was deposited by streams on fans 

and narrow pediments at a time when coarse debris 

was being moved over steep gradients. Either the 

relief of the area was higher than it is now, or the 

climate was slightly different. The older gravel may 

be largely of early or middle Pleistocene age, for it is 

older than the lacustrine deposits, which are probably 

of late Pleistocene age. 

YOUNGER ALLUVIAL AND FAN GRAVEL 

Gravel having moderately mature surface morphology, typified by more closely spaced gullies and 

rougher surfaces along drainage divides than are common on the older gravel, generally underlies fans and 

terraces of intermediate height above the present 

stream courses along the range front in Spring Valley and away from the front in Steptoe Valley. This 

gravel overlaps and partly buries the older gravel and 

is at least 100 feet thick. Gravel of uncertain age 

that appears in isolated bodies within the Schell Creek 

Range is arbitrarily mapped with this gravel. 

The younger gravel is much like the older gravel 

except that it is finer grained. Southwest of the Taylor district it contains much silt, which apparently 

has been washed from the older gravel for the younger 

deposits derived from the mountain slopes above the 

fans are much coarser even though similar in dip of 

bedding. Caliche locally caps the younger gravel, 

especially along and north of Bastian Creek. 

The younger alluvial and fan gravel was also deposited by streams on fans and narrow pediments and 

was deposited at a time when relief or climate conditions were not as different from the present ones a~ 

they seem to have been slightly earlier. Some of the 

youngest part of this gravel overlaps the lacustrine 

deposits, but most of the gravel is probably contemporaneous with, or older than, the lacustrine deposits. 

Most of the gravel is probably of late Pleistocene age, 

but some of it may be slightly older or slightly 

younger. 

LACUSTRINE DEPOSITS 

Silt, sand, and gravel of lacustrine origin underlie 

the lowest parts of Spring Valley, along the east edge 

of the quadrangle. The upper surface of these deposits is nearly horizontal, but it has a relief of 10-15 

feet and is characterized by benches and ridges parallel to the contours and by small hummocks. The most 

conspicuous ridges and benches lie at altitudes of 5,720 

feet, 5,760 feet, and 5,840 feet, but faintly defined ones 

appear still higher, and at Rattlesnake Knoll a narrow irregular terrace is cut on the bedrock at an altitude of 5,880 feet. The area underlain by the lacustrine deposits is densely covered with tall sagebrush 

and other shrubs, this vegetation indicating proximity 

to ground water. 

The low ridges are underlain by moderately well 

sorted and rounded pebble and shingle gravel, which 

is well exposed in a borrow pit just north of Highway 

6-50. Most of the surface material between the ridges 

consists of silt in small dunes or gravel in lag concentrates. A few miles southeast of the quadrangle, similar gravel is underlain by a clayey silt containing 

small unidentified pelecypods and gastropods (Drewes, 

1954, p. 81). 

The geomorphology of these deposits at the edge 

of the quadrangle and the rounding and sorting of 

the pebbles contained in them indicate that they were 

deposited in a lake. This interpretation is strengthened by a comparison with the more extensive deposits 

and geomorphic features in the bottom of Spring 

Valley. Clark and ·Riddell (1920) were the first to 

show that there had formerly been a pluvial lake in 

this valley, and I have discussed the history of the 

southern part of the lake (Drewes, 1954, p. 82-84). 

Spring Valley was first occupied by a large pluvial 

lake that reached an altitude of at least 5,880 feet. 

As the water level dropped, the lake was divided by a 

gravel bar, now followed by the north highline road 

a few miles southeast of the quadrangle, into a restricted Spring Valley Lake to the north and a smaller 

Shoshone Lake to the south. Thereafter, the lakes 

fluctuated in level many times but continued to recede. 
64 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

At present, some of the lowest parts of the northern 

basin contain ponds and both basins contain large 

marshes. 

The higher bars and the wave-cut terrace at Rattlesnake Knoll were thus formed in the earlier, more 

extensive stage of the pluvial Spring Valley Lake, 

and the bars at and below an altitude of 5,780 feet 

are related to the younger, more restricted stage of 

that lake. The lake is assumed to have formed during a regionally cool moist period, and the high lake 

stage was probably contemporaneous with the high 

level of pluvial Lake Bonneville, of late Pleistocene 

age, which extended into Snake Valley to the east. 

If that assumption is correct, the lacustrine <ieposits 

are mainly of late Pleistocene age, though the youngest may have been deposited in early Recent time. 

ALLUVIAL SAND AND GRAVEL 

Unconsolidated gravel and minor amounts of sand 

and silt form low terraces along stream courses and 

are still being deposited. Because the surface gradient on these deposits is gentler than that on the older 

gravel deposits, the youngest gravel commonly lies 

below the upper levels of the older gravel deposits 

near the canyon mouths at the foot of the mountains 

but overlaps them in small alluvial fans away from 

the mountains. The extremely rough surface on the 

grave] is dissected by a drainage network that tends 

to follow the abandoned channels of the streams that 

deposited the gravel. The gravel contains only debris 

of local origin. The largest boulders are washed out 

of nearby terraces, rather than washed down from the 

bedrock exposures. The youngest alluvium is entirely 

of Recent age. 

STRUCTURAL GEOLOGY 

In order to attempt to explain the structural environment, origin, and development of structural features within the Connors Pass quadrangle, I must 

summarize the tectonics of the surrounding region. 

The Connors Pass quadrangle lies in the eastern part 

of the Basin and Range province. This province is 

generally underlain by 20,000-40,000 feet of pre-Tertiary sedimentary rock, which is overlain in many 

places by a great thickness of Tertiary volcanic and 

sedimentary rock. Scattered Mesozoic and Tertiary 

stocks intrude the pre-Tertiary rock. The region contains many high -angle faults trending almost north, 

some bounding the ranges, and low-angle faults. 

There are also noteworthy smaller structural features 

pertinent to the geology of the Connors Pass quadrangle. 

The regional distribution of the major groups of 

sedimentary rocks indicates that a broad dome about 

40 miles wide and 80 miles long lies in eastern White 

Pine County and the adjacent part of Utah (Drewes, 

1960b) ; fig. 11. On the north, west, and south sides of 

this dome there are numerous complex low-angle 

faults, many of them near bedding planes, along which 

the apparent thickness of the strata is commonly reduced rather than increased. The dome and ma~y 

faults near bedding planes are cut by several major 

high-angle faults, such as range front faults, not shown 

on figure 11. The major dome is flanked by six or 

eight minor domes, each 10-30 miles in diameter. 

Some low-angle faults lie on or near each small dome, 

and few such faults have been found away from the 

domes. The larger areas of the most intense lowangle faulting, where upper Paleozoic rocks are commonly brought down onto Lower Cambrian or even 

Precambrian rocks, lie closer to the core of the major dome, and the areas of less intense faulting are 

farther from the core of the major dome. Many of 

the larger intrusive bodies lie near the centers of the 

small domes. 

The Connors Pass quadrangle lies on the southwest 

flank of a small dome extending along the east side 

of the central part of the Schell Creek Range and 

on the south end of another small dome in the Duck 

Creek Range, and it is in a zone of numerous lowangle faults. Most of the rocks here are moderately 

deformed, and in places they are severely deformed, 

chiefly by low-angle faults and steep normal faults 

but partly by tear faults and folds. The low-angle 

faults probably include both thrust faults and glide 

faults. The term "glide fault" is used here to describe faults formed as a direct result of gravity. At 

the time of movement, a glide fault plane reached the 

surface of the earth all around the allochthonous 

plate. In these respects a glide plate is a large variety of slump block. Low-angle normal faults, though 

also formed as a direct result of gravity, die out 

within the crust along their lower edge. Faults beneath slumps and glide plates may begin as low-angle 

normal faults along their upper edge, but become 

glide faults once the fault plane has been extended 

beneath the entire plate. The term "thrust fault" is 

used here to describe faults formed beneath plates 

that have been thrust laterally, either from some 

force within the crust or perhaps indirectly through 

gravity. · 

The structural features are of four general ages : 

Mesozoic ( ~), middle or late Tertiary, late Tertiary or 

early Pleistocene, and late Pleistocene or Recent. The 

scarcity of Mesozoic and early Tertiary rock prevents 

more precise dating of the structural features and 
0 5 10 

STRUCTURAL GEOLOGY 

15 20 

I 

I 

< ~~~ < &ll~ zl 

I 

I 

I 

I 

I 

I 

25 MILES 

EXPLANATION 

VALLEYS 

D 

Underlain largely by 

Cenozoic rocks 

RANGES 

65 

Underlain largely by Paleozoic 

rocks but include some older and 

younger rocks 

Solid field indicates plutonic intrusive body · 

Low-angle faults absent or of 

small size 

Low-angle faults moderately 

abundant 

Low-angle faults of large size 

or abundant 

Dome 

Showing age of rock exposed in core of 

dome; p£, Precambrian; £, Cambrian; 

0, Ordovician 

FwuRE 11.- Generalized tectonic map of the region around the Connors Pass quadrangle, showing the distribution of domes 

and low-angle faults. General stratigraphy adapted from McJannet (1960), Nolan (1935), Bick (1958), and Fritz (1960). 

240-303 0 - 67 - 6 
66 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

even causes considerable uncertainty regarding the 

ages assigned to some of them. 

those of the Schell Creek Range thrust fault and 

which may actually be an extension of it, ap-pears 15 

miles to the north of the quadrangle (Young, 1960a, 

STRUCTURAL FEATURES OF MESOZOIC(?) AGE b). The trace of the Schell Creek Range thrust fault, 

A group of low-angle faults that deformed Per- or a very similar one, recrosses the range 3-8 miles 

mian rocks but not Eocene rocks is tentatively dated south of Majors Place. Spurr (1903, p. 44-47) recogas Mesozoic. Similar faults in· nearby areas were nized a large fault between Carboniferous and Camdated by Misch ( 1960, p. 33) as probably of Late brian rocks east of Connors Pass, and faults in this 

Jurassic or Early Cretaceous age. I include in struc- area were discussed by Misch and Easton (1954), by 

tural features of this age some faults that are geo- Drewes ( 1960a), and by Misch and, Hazzard ( 1962, 

metrically similar to those of Mesozoic(~) age but of 319) p. . even more uncertain age, some broad arches, smaller Within the quadrangle the Schell Creek . Range 

faults, and folds within the low-angie fault plates. thrust fault is crossed by some faults and is confluent 

The porphyritic rhyolite dikes believed to be related with others. Between Majors Place and Cooper 

to the monzonitic plutons of adjacent are.as were Canyon, a block of fanglomerate and volcanic rock 

probably intruded late in this period of deformation. younger than the Schell Creek Range thrust fault 

Among the oldest, and possibly the very oldest, . ·is faulted into its upper plate, and for about 3 miles 

structural features in the area are two broad anti- the normal fault bounding this block is superposed on 

clines, the southern noses of minor domes, st:iking the trace of the thrust fault, and thereby interrupts the 

about north and plunging gently southward, Ill the thrust fault. At Stepto.e Creek, again·, the trace of the 

northern part of the quadrangle (fig. 11). The axis Schell ·Creek Range thrust fault is interrupted for 

of the larger anticline runs through Cave Mountain · more than a mile by a graben, by which that thrust 

and the crest of the Schell Creek Range, and that of fault has been offset for several miles to the north, 

the smaller one passes near Camel Peak between upper . beyond the edge of the quadrangle. 

Steptoe Creek and Mosier Canyon . . The formations as The Schell Creek Range thrust fault is confined to 

a whole, as well as the minor thrust planes, are arched a single well-defined shear surface where the rocks of 

over the axes, but the bedding planes, except perhaps the upper plate are relatively imcompe~ent, but where 

in the oldest rocks, do not closely conform to . the they are competent it is distributed among several 

anticlinal structure. This apparent incongruity will subparallel shear surfaces. Stripped low-angle fault 

be explained in the following sectio~. Howell ( 1875, surfaces are exposed j:ust north .of Cooper Canyon and 

p. 240-247) was the first to recognize a quaquaversal · northwest of Grasshopper Canyon, and the fault is 

structure in the southern Snake Range, and Spurr also w~ll exposed along U.S. Highway 6-50-93. At 

(1903, p. 44-47) mentioned a large north-trending fold the surface' the fault dips about 25° sw.; this dip can 

in the Schell Creek Range. be proj~cood downward for 200-1,000 feet. where there 

The age relations between the minor domes and is ·considerable relief. Northeast of Its trace, a 

other structural features of Mesozoic ( ~ ) age are uncer- restored surface of the main fault would presumably 

tain: It ~eems as likely, at first glance, that the ~ arch ~ver the crest of the ridge, and about 1 mile 

doming warped the low-angle faults as that the faults :southeast of the Kolcheck Basin dip downward befollowed bedding planes· already warped. Inasmuch n~th the small klippe or tectonic outlier of Chainman 

as the age relations between these features seem to be Shale and Joana Limestone. South of· the mouth of 

essential to the interpretation of the structure, the the canyon of Cleve Creek, the fault .. p~obably also 

reasons for this uncertainty will be discussed in the underli~s a small block of El'y Limestone and Chainsection on low-angle faults (p. 74). Suffice it to say man Shale that has been further dropped along rangehere that regional relations preclude my inferring that front normal faults. 

the faulting has been caused by the doming and hence The youngest rock in the lower plate of the Schell 

that these features are contemporaneous. Creek Range thrust fault is generally the lower part 

SCHELL CREEK RANGE THRUST FAULT 

The main low-angle fault in the Connors Pass quadrangle will here be referred to as the Schell Creek 

Range thrust fault. Its trace extends diagonally 

northwestward across the quadrangle from near 

Majors Place to Mosier Canyon (pis. 1, 2). A lowangle fault, whose structural relations are similar to 

of the limestone of Cambrian and Ordovician age. 

Near the fault it is ·slightly sheared, and in places it is 

my lonitized, recrystallized, a;nd warped. The bedding 

of this rock. is nearly parallel to the fault ,surface 

except for a few small folds, whose axial planes strike 

northwest and generally dip southwest. The rock at 

the base of the upper plate is most commonly the 
STRUCTURAL GEOLOGY 67 

Chainman Shale, but in places the Arcturus Formation and Ely Limestone lie directly on the lower plate, 

and locally there are a few slices of Guilmette Formation and even older _rock above the fault. · Farther 

from the trace of the fault, rocks older than the 

Guilmette Formation appear in the upper plate, and 

less rock appears to be missing along the fault. The 

rocks of the upper plate commonly dip into the fault 

plane, and their structural habit differs from that of 

the rocks immediately beneath the fault plane. 

STRUCTURE OF THE LOWER MAJOR THRUST PLATE 

In the lower major plate, low-angle faults of various kinds are more plentiful than steep normal faults, 

and they become less common away from the major 

fault. Northeast of Cave Creek most of,the low-angle 

faults separate formations _ or separate beds of different 

character within formations. In general they are 

almost parallel with bedding, and the rocks in the 

minor fault plates are mostly in their normal stratigraphic order. Locally, however, parts of the formati~ns, or even entire formations, are cut out along 

mmor low-angle faults; in other places, ·beds in adjacent parts of minor plates are parallel to each other 

but dip more steeply than the intervening fault. On 

the 10,300-foot peak 3 miles north of Cave Mountain, 

for example, the fault contacts between formations are 

nearly horizontal, but the beds of each formation dip 

30° or more to the east. The steeper dips occur on 

the east side of the peak, where the section is least 

complete. A stratigraphic section normally about 

5,000 feet thick is here represented by fault slices 

only 1,000 feet in total thickness. 

On plate 2 the larger of the minor low-angle faults 

are lettered consecutively in ascending order from 

A to M. A few faults that bifurcate are designated 

by numerical subscripts. Fault C, for example, splits 

to for:n faults C1 and C2, C1 being the lower. Although 

the minor faults along some horizons are discontinuous, their separate segments are given one letter where 

t~e faults seem to be potentially continuous (had the 

displacement along the fault been greater) or to join 

up or down the dip. For instance fault A which is 

within a thin shaly unit between thick mas~ive units 

cannot be continuously traced, but I suspect that i~ separate segments are joined beneath the surface or 

were ?nee joined in the rocks now eroded away. I also 

de&ribe some of the minor faults as smaller or larger 

than others and thereby loosely compare their promin~ce. ~'Smaller" and "larger" need not be synonymous 

with either amount of displacement or length of the 

fault, bu~ may .be a combination of both parameters. 

The minor low-angle faults-differ greatly in extent 

and so do the thicknesses of the rocks that are cut ou~ 

by them. These variations-can be illustrated by examples arranged in a gradational series. The most extensive minor low-angle fault in the lower major plate, 

fault C, follows the base of the limestone of Cambrian 

and Ordovician age. Generally very little of the 

Lincoln Peak Formation is missing beneath this -fault, 

but near Bastian Spring the entire formation_ is 

faulted out. Along the upper part of Steptoe Creek, 

northwest of Grasshopper Canyon, and south of 

Cooper Canyon, fault C follows the same horizon 

above shaly rocks and beneath relatively massive lims.,. 

stone, but north of Cooper Canyon and in the Cleve 

Creek area it splits into two branches ( C1 and C2 ), 

rarely more _than 200 feet apart. The rocks between 

C1 and C2 are alternating shaly limestone and moderately thick bedded limestone, intermediate - in competence between the shale and the limestone adjacent 

to fault C. Fault C does not split further south, perhaps because rocks of intermediate competence are 

there absent along this horizon, owing to a facies 

change. Faults C1 and C2 can be recognized where 

they are separated by rocks of this transitional character that dip more steeply than either of the faults. 

The bedding in the shaly rocks below C1 and that in 

the relatively massive limestone above C2 also converge with these faults. Fault C, or C2 , is exposed in 

many places; fault c1 is covered by colluvium, but 

there are abrupt changes of attitude and lithologic 

character in the rocks along its course. Faults C1 and 

C2 . appear to be connected at several places by minor 

low-angle faults, and presumably other cross faults 

have been overlooked. 

Faults D and E are as long as fault C, but inasmuch 

as the thicknesses of the rocks missing along them 

are less, they seem to be somewhat smaller. Fault E 

follows the base of the Fish Haven Dolomite where 

the Eureka Quartzite is missing, and in places it splits 

into E1 and E2, which are separated by thin sheared 

lenses of the quartzite. This fault brings rocks that 

are probably low in the Fish Haven Dolomite against 

rock~ as low in the norma~ stratigraphic sequence as 

the limestone beneath the ohve-gray clay-shale member 

of the limestone of Cambrian and Ordovician age. To 

the south, fault D converges gradually with fault E, 

but to the north, near the Kolcheck mine, fault E cuts 

fault D at a fairly large angle, this relation indicating 

that movement on fault -D had ceased before movement 

along fault E began. Other very-local minor beddingplane faults may follow the base of the limestone beds ' 

above the olive-gray clay-shale ·member. 

Faults F and B are much less conspicuous than 

those described above. Fault F extends for alniost 

2 miles between Cave and Cleve Creeks, where it 
68 GE.OLOGY, CONNORS PASS QUADRANGLE, NEVADA 

brings rocks low in the Simonsbn Dolomite against the 

Sevy Dolomite and in places against the Laketown 

Dolomite. Along fault B, which is more extensive 

than fault F, only a thin sequence of rocks is missing. 

Near the mouth of Cooper Canyon, rocks probably low 

in the Lincoln Pea~ Formation are faulted across the 

upp~r several hundred feet of the Pole Canyon Limestone. . The lowest shaly beds a!ong the fault are 

sheared; they weather to a reddish-brown soil. 

Misch and Hazzard (1962) considered fault B a 

decollement fault.-in the vicinity of Majors Place. (See 

also Misch and Easton, 1954; Drewes, 1960a; Misch, 

1960.) Fault B, however, is only one of many minor 

thrust faults almost parallel with bedding planes. It 

is neither the lowest nor the largest, nor does it lie at 

the base of shingled thrust plates. Fault B, therefore, 

seems no different from the many other similar faults 

in the area. Considering our present knowledge of 

the area, I suspect that the application of the term 

"decollement fault" tp any fault exposed in the 

Connors Pass quadrangle would detract from the 

appeal that decollement faulting has as a regional 

hypothesis. · 

The lowest and least extensive mapped minor 

bedding-plane fault, A, cuts out all of the Pioche 

Shale about a mile north of Majors Place, but only a 

part of it 3 miles north of Majors Place and also just 

south of Cleve Creek. On the south wall of Mosier 

Canyon, in the northwest corner of the quadrangle, 

vertical and slightly overturned beds of Prospect 

Mountain Quartzite and Pioche Shale indicate local 

movement on this fault along the shale and perhaps 

also movement along a lower horizon within the 

quartzite. . About 2 miles north of the mouth of 

Cooper Canyon, · structural details along marker bed a 

of the Lincoln Peak Formation show very minor 

bedding-plane faults within the formation in addition 

~o the mapped fau1ts. In this place, shale beds adjacent to the mapped limestone marker beds have been 

d.isharmonically folded along the contacts with the 

limestone beds. · 

The lower major plate is broken by one group of 

high-angle tear faults. about a mile north of Cave 

Mountain an-d also . along the main ridge about a mile 

~uth of the north edge of the -qu~drangle. These 

~aults strike northe~stward, :and ·downdip they join 

minor low-angle faults above the Lincoln Peak Formation (pl. 3). Rocks of Middle Ordovician to Devonian 

age, which ar~ _generally missing along the trace of the 

Schel~ Creek Range thrust fau~t, are p~esent between 

t;he tear f!lults . . Perhaps they were preserved beneath 

the Schell Creek ~ange thrust fault because within 

the lower major plate they occupy a structurally low 

position between the tear faults. 

Most of the high-angle faults that cut the rocks of 

the lower major plate are normal faults that strike 

north to northeast, and many end upward, downward, 

or in both directions against minor low-angle faults. 

The normal faults along the upper part of Cleve 

Creek are truncated upward by the lowest of the minor 

low-angle faults present there, fault C. With the 

possible exception of these, the normal faults appear 

to have relieved stresses between blocks within the 

minor low-angle fault plates. Many other minor 

normal faults probably cut the rocks, but because of 

the present lack of detailed stratigraphic control it 

has been impossible to map them. The difficulty of 

recognizing and mapping subdivisions of the Cambrian and Ordovician limestone is due to the many 

small normal faults within it. The widespread convergence of the strata with the minor low-angle faults 

is probably caused in part by the rotation of segments 

of minor thrust plates between these small normal 

faults. 

The Lincoln Peak Formation and the limestone of 

Cambrian and Ordovician age have been deformed in 

places by folds a mile or more in length that have 

gently dipping limbs and north- to northwest-trending 

horizontal axes. These folds are disharmonic features, 

in that no one of them affects more than one formation. 

Smaller folds, which are asymmetric and rarely more 

than 30 feet in amplitude are common in the Lincoln 

Peak Formation north of U.S. Highway &--50--93. 

Their axes trend northwest and are horizontal or 

plunge gently either way, and their axial planes dip 

10°..:..60° northeast~ard. They are disharmonic with 

respect to the fault contact at the top of the Lincoln 

Peak Formation. Other small folds occur throughout 

the lower major plate. 

•STRUCTURE OF THE UPPER MAJOR THRUS'.l" PLATE 

In the upper major plate, above the Schell Creek 

Range thrust fault, steep normal faults are more 

numerous than ·minor low-angle faults, and 'folds are 

relatively scarce. The normal faults differ more 

widely in strike than those in the lower major plate, 

and only locally do they form regtilar patterns. ·For 

instance, a roughly arcuate pattern is formed by 

widely spaced normai faults high in the upper major 

plate southeast of Connors . Pass. Severa.l small 

northeast-trending faults cut the Joana · Limestone 

near the junction of Cave Creek and Steptoe. Creek 

and die out in the overlying Chainman Shale and the 

underlying Pilot Shale. The Joana is cut by small 

faults in many other places, apparently in reSponse to 
I 

STRUCTURAL GEOLOGj . 69 

stress adjustments between the incompetent shale because ltmestone of various faunal zones lies directly 

formations adjacent to the limestone. on the sh~·le, and because over large areas the limestone 

Most of the minor low-angle faults in the upper dips into the upper part of the shale. In some places 

major plate are near the Schell Creek Range thrust as much as 1,500 feet of the lower part of the limefault. Fault H follows the base of the Guilmette stone is missing along fault K, but elsewhere little or 

Formation on both sides of lower Steptoe Creek. none of ~ is missing. This relation is well shown at 

Rocks in the lower part of the Guilmette Formation the outc op of limestone on a ridge 1 mile north of 

there lie either on the Sevy Dolomite or on the lower The Narfows on the lower Steptoe Creek (pis. 1, 3). 

part of the Simonson Dolomite. On the west side of On the S<jmthwest side of the hill the contact seems to 

Tamberlaine Canyon, the Simonson Dolomite immedi- be norma , for rocks characteristic of the basal part of 

ately beneath fault H dips steeply and is truncated the Ely 1 Limestone lie conformably on rocks preby a thin limestone unit of member a of the Guilmette sumably at the top of the Chainman Shale. The rocks 

Formation. The relations are less obvious, however, dip 30°---45° northeastward, the steeper dips being in I • 

on the large hill a mile and a half south of the mouth the northeast. Ohaetetes-beanng beds of Pennsylof the canyon of Steptoe Creek, where rocks of mem- vanian a~e and the silty limestone containing fusulines 

ber a of the Guilmette Formation lie immediately of Permian age lie in their normal stratigraphic posiabove, and parallel to, beds high in the Sevy Dolomite. tions, abput 1,400 feet and 2,000 feet, respectively, 

This contact has been mapped as a fault rather than above th' base of the Ely. The ridge crest thus conan unconformity, which it also resembles, because no sists of Fermian rocks, but only 200 feet topographiregional unconformity is known at this .horizon and cally beldw and northeast of it, downdip from some of 

because local bedding-plane faults are abundant. the Per4ian rocks, the Chainman Shale reappears. 

The Pilot Shale is also thinned in several places by Around he northwest and southeast ends of the ridge 

minor faults almost parallel to bedding. Just south of the beds ponverge northeastward with the nearly horiTamberlaine Canyon a group of three such faults, the zontal fal.lt contact at the top of the shale. On three 

middle and probably the most extensive being fault I, sides of 1..,he hill the fault movement is concentrated 

brings a thin unit of tilted Joana Limestone close to at the base of the limestone, as shown by fault K. On 

beds in member a of the Guilmette Formation. These the southwest side of the hill, however, most of the 

rocks are similarly faulted together along the lower moveme~ lies at a slightly lower horizon within the 

part of Steptoe Creek, but there t.he low-angle faults shale, falfllt K2, and a little movement may also have 

are displaced by many normal faults. Farther south followed fault K1 without leaving any conspicuous 

the deformation along fault I gradually becomes less trace. 

marked, as Pilot Shale is brought onto different mem- In a ock of Ely Limestone near the Aspen Spring 

hers of the Guilmette Formation. in the celjlter of the quadrangle, the beds dip as steeply 

Along some of the minor low-angle faults in the as 65° NlE. (not shown on map) and over large areas 

upper major plate, beds have been repeated rather the same lbeds dip 40° NE., where the contact with the 

than cut out. In the large hill 3 miles south of lower Chainman Shale dips about 5° SE. A similar strucSteptoe Creek and west of Cooper Wash, dolomite of tural rel tion exists around the flanks of the limestone 

the Guilmette Formation has been moved on fault J forming fhe peak at Taylor bench mark (fig. 8). 

over other apparently younger dolomite in that forma- Other small masses of Ely Limestone lie on or withtion and over the Chainman Shale (pl. 1, section in the ~hainman Shale. Those not associated with 

M-M'). The small plate above this fault is bounded slump topography and not in positions that could 

on the northwest by a northeast-trending tear fault. have bee~ part of a more extensive thrust plate or 

Structural details along the south end of this plate glide plJte are regarded as blocks that moved along 

are obscured by strong local dolomitization and con- unmapp, d faults within the shale. Some of these 

sequent blurring of stratigraphic details within the blocks Jitay even have been engulfed in the highly 

Guilmette Formation. . plastic spale at times during which the rocks were 

Higher in the upper major plate a low-angle fault, under gr~at stress, or they may have been slump blocks 

K, extends along, or just beneath, the contact of the of Tertidry age. In several places the shale has been 

Chainman Shale with the Ely Limestone, which has plastical1~ deformed near its contact with the limebeen so much eroded that only scattered outliers stone. 1 ust south of Cooper Canyon and near the 

remain_: The fault plane is nowhere exposed, for the center of the drainage basin, slightly overturned 

, shale is largely covered by limestone . debris, and the Chainmajll Shale lies on a large body of Ely Limestone. 

shale is commonly slumped. Faulting is inferred Along tble highway a mile southwest of Connors Pass, 

--·-_ _______ ____. 
70 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

Chainman Shale has been squeezed up into the limestone. Such plastic deformation is greatly facilitated 

by the gypsum and high clay content of the shale. 

In the southwestern part of the quadrangle, signs 

of structural deformation along the contact between 

the Chainman Shale· and Ely Limestone are fewer and 

less impressive or are masked by high-angle faults. 

Two ·miles southwest of Connors Pass, however, just 

north of the highway, some beds of limestone and conglomerate in the Chainman Shale are upended beneath the base of the Ely Limestone. 

On the south wall of Cooper Canyon just west of 

the trace of the Schell Creek Range thrust fault, the 

Arcturus Formation seems to be thrust along fault L 

over the Ely Limestone. The Ely Limestone has 

fairly steep to vertical dips, and the Arcturus Formation gentle to moderate dips, whereas the contact between the formations seems to be nearly horizontal. 

East of this locality the Ely Limestone wedges out 

between fault L and the Schell Creek Range thrust 

fault. 

In a downfaulted block high in the upper major 

plate, the Ely Limestone is thrust over the Rib Hill 

Sandstone and the Arcturus Formation on fault M, 

which is gently arched from northeast to northwest, 

just north of Connors Pass. Fault M is not exposed 

because the rocks immediately beneath it are incompetent and the slopes are covered with debris of the 

Ely Limestone. About a mile northeast of the pass, 

Pennsylvanian Chaetetes-bearing rocks in the middle 

of the Ely Limestone lie a short distance above Permian rocks, some of which may be as young as the 

gypsiferous Lower Permian rocks in the Arcturus . 

Formation. 

Fossil determinations made after the completion of 

the fieldwork indicate that some beds low in the 

Permian part of the Ely Formation were mistakenly 

ass~gned to the Arcturus Formation in the Connors 

Pass area but,. regardless of this possible miscorrelation, known Pennsylvanian rocks there have moved 

over Permian rocks. To the west, fault M is cut out 

by a high-angle normal fault that brings rock high in 

the Ely Limestone overlying fault M in contact with 

the middle part of the Ely Limestone overlying fault 

K. Thus, lj2-l .mile west of Connors Pass the Chainman Shale is exp<;>sed in part of a fenster through 

faul~ K, and the Rib Hill Sandstone adjacent to the 

shale is expOsed in part of a fenster through fault M 

(pl. 1, section 0-0'). The Chain Shale and Rib Hill 

Sandstone are here separated by narrow slices of· brecciated Ely Limestone. 

In the southwestern part of the quadrangle, three 

broad gentle folds extend· northeastward and · are 1-2 

miles long. Smaller folds occur at a few places in 'the 

Chainman Shale, their · axes striking north west and 

their axial ·planes vertical or dipping steeply to . the 

southwest. 

In both of the major plates, the small folds are 

probably· drag folds formed during the time or times 

of movement along the lo~-angle faults. The ·axes of 

the drag folds almost all strike north to northwest and 

are horizontal or gently inclined, but the direction of 

dip of the axial planes of the folds is less systematic. 

In the lower major plate, somewhat more than half 

of the axial planes dip southwestward, and the acute 

angle between the fault plane and the axial planes of 

the drag folds points northeastward, this relation indicatiri.g that the upper plate moved relatively northeastward. The axial planes of many other drag folds 

are at right angles to the fault planes, so the direction 

of movement is equivocal, and the axial planes of a 

few drag folds in the lower plate dip northeastward. 

In the upper major plate, however, the axial planes 

all dip southwestward, this dip indicating that the 

upper plate on each of the minor thrusts in that plate 

moved relatively northeastward. Evidence presented 

by these structural features, as well as by the northeast-striking tear faults, shows clearly that the upper 

plate moved relatively northeastward or southwestward on the main fault, but the actual direction of 

movement is somewhat uncertain. Perhaps there were 

even two different directions of movement at different 

times. 

STRUCTURAL FEATUR:&S OF MIDDLE OR LATE 

TERTIARY AGE 

A second group of features comprises normal faults 

and glide faults that cut rocks as young as those of 

Oligocene(~) age and that also cut the Schell Creek 

Range thrust fault. Normal faults of this group trend 

north or alternately north and northwest, and some 

of them are paired to form the sides of · grabens. 

These faults are less numerous, but of larger displacement, in the northern part of the quadrangle than in 

the southern part. Where normal faults of large displacement join subparallel thrust faults without deflecting them, . as they do east of Cooper Summit and 

south of Cooper Canyon, the normal fault surfaces 

are believed to have followed thrust-fault surfaces 

downdip for a moderate distance. 

The largest graben, Duck Creek graben, lies between 

the Grasshopper Canyon fault and ·the Steptoe C~k 

fault (pl. 2) and is at the south end of a topographic 

and structural basin, about 25 miles long and 5 miles 

wide, between the Duck Creek Rari.ge and· the main 

part of the Schell Creek Range. The geology at the 
STRUCTU~AL GEOLOGY 71 

north and south ends of the basin is probably more 

indicative of the rocks and structure beneath the 

alluvium in the basin than is the geology on the slopes 

to the east or west. South of this basin the Grasshopper Canyon fault dips steeply eastward, and toward the south its stratigraphic displacement decreases 

and even reverses. Also south of the basin, the Steptoe Creek fault consists of several closely spaced west-' 

dipping faults,, most of which have only moderately 

steep dips. The .south end of this fault zone turns 

eastward along Cave Creek and follows a segment of 

the . older Schell Creek Range thrust fault. Although 

rocks as young as Permian are dropped in the graben 

between rocks as old as Late Cambrian, the stratigraphic displacement along the faults adjacent to the 

graben is not as large as it might seem, for much of 

the stratigraphic section is cut out by the older lowangle faults. Inasmuch as the Duck Creek graben 

topographically resembles many of the larger valleys 

of the region, the structure of the rocks within it may 

be similar to that of the rocks under Spring Valley 

and Steptoe Valley; therefore, the features at the ends 

of the Duck Creek graben might give us some clues to 

the structure underlying those valleys. 

South of the Duck Creek graben are several smaller 

grabens that contain· sedimentary or volcanic rock of 

Tertiary age. The fault bounding the east side of a 

small graben between Cooper Canyon and U.S. Highway 6-50-93 has been superposed on the trace of the 

Schell Creek Range thrust fault for about 3 miles. It 

probably truncates this fault, as projections of the 

faults downdip indicate (pl. 1, section 0-0'), but a 

part of the normal fault probably coincides with a 

steeply dipping .Part of the thrust fault. Some of the 

faults along Cooper Wash and near the Taylor mining 

district are tentatively grouped with these Tertiary 

norma~ faults because of their association . with .small 

grabens~ 

Between Cooper Canyon and the central part of 

Steptoe Creek, low-angle faults underlie two plates. of 

Tertiary conglomerate and volcanic rock. The remnant of the fault plate south of Cave Creek covers 

about 8 square miles and consists of at least 5,000 feet 

of conglomerate, lava :flows; tuff, and welded tuff~ The 

one north of Cave Creek is much·. smaller, consists of 

a thinner sequence of similar rock, and is largely covered by the older alluvial and fan gravel. Both plates 

rest mainly on the Chainman Shale, but small parts 

of them rest on or. against blocks of Ely. Limestone, 

and part of the east edge of ·the large fault plate rests 

on Cambrian and Ordovician limestone. 

Although the contacts .. between · the Tertiary rock 

and the older rock are covered and the rocks near the 

contact indicate little of the local structure, these contacts are inferred to be fault contacts. · There must be 

a iault contact. between the eastern half of the .larger 

body of Tertiary rock and the Paleozoic rock because 

the overlying Tertiary rock dips eastward toward the 

adjacent exposures of older rock. The trace of the 

contact around the eastern half of this body is deflected 

across spurs and around ridges in. such a manner as to 

require a fault surface that dips gently inward like 

the edges of a saucer. The contrast in style of deformation between the Tertiary and the Paleozoic rocks 

also indicates the . nature of the faulting. The rock 

above the fault is gently warped into a broad syncline, 

which plunges eastward toward the underlying fault 

surface, but the Tertiary rock itself is cut by relatively 

few faults. The Paleozoic rock, however, is intricately 

faulted and is sheared along faults near bedding 

planes. These contrasts indicate that the deformation 

of the Tertiary rock and that of the Paleozoic rock 

reflect wide differences of stress and environment. The 

plates of Tertiary rock resemble those that moved 

along the Turtleback faults in the Death Valley region 

of California (Drewes, 1959}, except, of course, that 

their lower surfaces are concave rather than convex 

upward. The plates of Tertiary rock also resemble 

large slump blocks in that they are rotated about a 

north-trending horizontal axis and dip eastward and 

in that they appear to rest in part on a saucer-shaped 

surface. These comparisons and contrasts suggest that 

the fault beneath the plate of Tertiary rock was 

formed near the surface, as a glide· fault. This interpretation is strengthened by the fact that .the ·Tertiary 

rock most commonly overlies the plastic Chainman 

Shale, which must always have underlain topographically low areas and which would be an ideal lubricant 

for either a large slump block or a glide _plate, two 

structural features differing only in size. 

If this interpretation is accepted, tha low-angle 

fault must be inferred to continue between the Chainman Shale and the main body of. Tertiary rock to the 

west, for the rotation of the eastern part of . the plate 

could only be effected by a shift of the . western part, 

where the Tertiary rock is more nearly conformable 

with the. contact beneath it. 

One minor complication around the larger plate . of 

Tertiary rock must be considered here. Along , the . 

road in the upper part of Cave Creek Canyon,; conglomerate in this larger plate overlies a small . block 

of Ely Limestone without signs of faulting. The 

block of Ely Limestone possibly was d~gged alo!lg 
72 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

the base o:f the plate o:f Tertiary rock on the shale 

immediately beneath the limestone. 

Some of the other Tertiary rock within the Connors 

Pass quadrangle also seems to rest on faulted surfaces, 

but other Tertiary rock merely rests on unconformities. 

The body of Tertiary rock north of Cave Creek resembles the larger one in every respect except size and 

is therefore also inferred to be the remnant of a glide 

plate. Inasmuch as the Tertiary rock south of Cooper 

Canyon is bounded by high-angle :faults and does not 

dip into underlying Paleozoic rock, it is not inferred 

to rest on a low-angle fault, even though the conglomerate there is gently warped like that in the bodies 

regarded as remnants of a glide plate. In the northern part of the Schell Creek Range, Young ( 1960b, 

p. 167-168) reported low-angle faults resembling the 

one here described. 

, STRUCTURAL FEATURES OF LATE TERTIARY OR 

EARLY PLEISTOCENE AGE 

Structural :features of middle or late Tertiary age 

were cut by normal :faults, apparently before the deposition of upper Pleistocene gravel. Several normal 

faults that lie wholly within the Schell Creek Range 

cut the low-angle :fault and the overlying plate of Tertiary rock south of Cave Creek. The upper part of 

the largest of these faults probably was active during 

movement o:f the glide plate of Tertiary rock, :for . it 

offsets the rocks above the glide fault more than it 

does the glide fault itself. Renewed normal faulting 

occurred along the existing fault plane within the 

glide plate and extended below the glide plate, so at 

present the rocks within the glide plate are offset more 

than those beneath the glide plate. Near Cave Creek 

the later movement along this largest normal fault 

probably extended along the Steptoe Creek fault, 

which had already been active during early or middle 

Tertiary time. In other words, there was recurrent 

movement along some, at least, of the segments of the 

normal fault along upper Steptoe Creek, Cave Creek, 

and Cooper Canyon. It is noteworthy that the lowangle glide fault beneath the Tertiary rock occurred 

between times of other large crustal movements. 

The only normal fault along either front of the 

range is in the northeast corner of the quadrangle. 

Near the' mouth o:f the canyon of Cleve Creek this 

:fault splays out toward the south, and branches of it 

extend into Spring Valley as well as into the range. 

North of the mouth o:f the canyon the fault is buried 

but probably lies close to the foot o:f a prominent scarp, 

which continues at least 25 miles northward beyond 

the quadrangle. The latest movement along this :fault 

probably occurred in late Quaternary time, for the 

younger alluvial and fan gravels are crossed by dim 

fault scars. 

A normal fault-the Taylor fault (pl. 2)-.,.-trends 

alternately northward and northwestward close to the 

west front of· the range. Rocks that are mainly o:f 

late Paleozoic age but include the older alluvial and 

fan gravel of Pleistocene age are faulted down to the 

west along the northwest-trending segments of this 

fault, which seems to truncate some of the older 

grabens. The north-trending segments probably followed some of the older normal faults. According to 

A. L. Brokaw (oral commun., 1962), another large 

young normal fault, downthrown to the east, trends 

northwestward along the east flank of the Egan Range 

and cuts obliquely across part o:f it near the copper 

pit at Ruth. The northwestward trend of a part of 

Steptoe Valley-roughly between the latitudes of Connors Pass and Ely-seems to have been controlled or 

influenced by a segment of a major graben lying between the large :fault in the Egan Range and the 

Taylor fault. 

Normal faults probably underlie the low scarp lets 

in the fan gravel several miles west of the Schell Creek 

Range in the southwestern pait of the quadrangle. 

Because these scarp lets follow the contours closely, 

they superficially resemble the little wave-cut cliffs 

in Spring Valley, but the scarp lets in Steptoe Valley 

are not associated with lacustrine gravel. A preliminary gravity survey across Steptoe Valley west of the 

Taylor mining district by D. R. Mabey (written 

commun., 1962) showed a locally steep gravity gradient, suggestive of a fault, alined with the scarplets. 

In Grasshopper Canyon a large body of shattered 

· or brecciated, but not strongly rotated or mixed, Ely 

Limestone and Chainman Shale rests partly on more 

of the Chainman Shale and Ely Limestone and partly 

on Cambrian rocks. Where the bedding is preserved, 

it dips 30°-55° eastward-at least twice as steeply as 

similar rocks in the adjacent ridge. This body of 

shale and limestone is believed to be a large slump 

block or possibly a landslide, and it differs from the 

nume~ous recent slump blocks in its relation to adjacent topography. It deflected the course of the wash 

in Grasshopper Canyon about 500 feet to the west, 

and thereafter a canyon about 100 feet deep was cut 

into the distal end of the body of sha.le and limestone. 

This amount o:f canyon cutting indicates t~at t~e 

body of shale and limestone probably moved .mto Its 

present position at least as long ago as Pleistocene 

time. 
STRUCTURAL GEOLOGY 73 

STRUCTURAL FEATURES OF LATE PLEISTOCENE 

OR RECENT AGE 

Slump blocks are given special attention here as 

structural features resting on low-angle faults, rather 

than as topographic or weathering features characteristic of shaly formation, because the area contains 

many somewhat similar but larger structure features. 

The term "slump block" is used here to describe a 

variety of landslide in which a mass of rock has 

moved relatively slowly as a discrete body over a 

fault surface. Material in a debris slide, another 

variety of landslide, is shattered, generally because it 

has moved more rapidly. Some landslide masses have 

features intermediate between those of slump blocks 

and debris slides. 

Most of the slump blocks are underlain by Chainman Shale, but some are under lain by the Lincoln 

Peak Formation. Areas marked by prominent landslide topography total about 2 square miles; they are 

outlined on plate 1 by a fault contact and are distinguished from other low-angle fault blocks by an overprint pattern. In areas of slight local relief, the slump 

blocks are characterized by an irregular hummocky 

topography, but where the local relief is greater they 

make a rudely terraced topography, in which many 

of the terrace surfaces slope gently in a direction opposite to the general slope. Springs issued from the 

lower edges of several of the areas of slump blocks. 

The slumped material consists mainly of shale similar 

to that over which the slump block has moved, but 

in places it also contains fragments of the more competent rocks overlying the shale. For instance, blocks 

of Ely Limestone as much as several hundred feet in 

length seem to be rafted on internally disturbed and 

weathered Chainman Shale. The slump blocks are 

believed to be of Pleistocene or Recent age, because 

they are closely related to the present topography in 

areas of moderate relief. That some downslope movement is currently in progress is indicated by locally 

steep frontal lobes, by small depressions, and by disrupted vegetation. 

ORIGIN OF STRUCTURE 

The stress pattern responsible for the structural 

features in the Connors Pass quadrangle is not fully 

known, especially for those that extend beyond the 

borders of the quadrangle, for too little is known of the 

surrounding region-particularly of the rocks under the 

floor of the alluviated basins-to form a complete picture of the geometry of these major structural features; very few descriptions of the geology in this 

region recorded the observations on which conclusions 

regarding ·directions of movement on faults were 

based. The available evidence within the quadrangJ.e 

is not sufficiently diagnostic for me to determine the 

origin of some of the low-angle faults, and that evidence is distorted by recurrent and diverse movement 

along some of the faults. 

The main structural problem in the eastern Great 

Basin is the origin of the low-angle faults. Thrust 

faults are reported in most mountain ranges, but glide 

faults also are recognized in some places. Ideally, 

thrust faults are formed as the result of tangential 

compressive stresses relatively deep in the earth, 

whereas glide faults are the product of gravitative 

forces near the surface of the earth. In practice, 

the distinction between glide faults and thrust faults 

has never been a simple one to make, because in many 

places the rocks involved were probably subjected to 

both gravitational and laterally transmitted compressive stresses, which varied widely in relative importance. Where irregular glide surfaces introduce local compressive stresses or where glide faults form 

downslope in front of thrust faults, field evidence may 

be apparently conflicting. Local field evidence may 

not be diagnostic, and even in more thoroughly 

mapped areas than the eastern Great Basin it may be 

largely indicative rather than conclusive. 

Even in areas where field evidence is not ambiguous, 

listing of rigid criteria for distinguishing the various 

kinds of low-angle faults is difficult. General evidence 

more strongly indicative of thrust faulting than of 

glide faulting includes persistent and widely distributed signs of compression well within the fault plates. 

Just how uniform, how strongly developed, and how 

extensive the compressional features must be is not 

clear; it apparently depends on environment-such 

factors as type of sediment, depth of burial, rate of 

deformation, and hydraulic conditions. Recognition 

of a root area is accepted as evidence of thrust faulting, but there is no general agreement about the criteria for recognizing a root area. A fault that plunges 

downward in the direction from which the upper plate 

moved is comnwnly regarded as a thrust fault, but 

because the configuration of many glide surfaces is 

irregular, the downward plunge must persist for a 

long distance (another vague quantity) if it is to be 

regarded as evidence of thrust faulting. 

The presence of a gentle slope down which a plate 

has moved may be regarded as evidence, though perhaps only permissive evidence, of glide faulting. 

Apparently the larger the glide plate is, the gentler 

the slope can be, for the slope under a large plate 

must be extensive, and thus the total drop across the 

slope must be considerable (still another va~e quan-
74 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

tity). Perhaps, also, · great incoherence in the faulted 

rocks· and conflicting evidence of direction of movement indicate glide faulting rather than thrust fault- · 

ing. This brief review of some salient features of 

glide faults and thrust faults shows how difficult it 

oft~n is . to distinguish ,between them. To reconstruct 

the conditions under which the low-angle faults in the 

Great Basin . were formed--:-to identify slopes of regional extent for glide faults or root zones. for thrust 

faults-is exceptionally difficult, because the low-angle 

faults are cut by younger high-angle faults and be-

-cause relatively narrow mountain ranges are separated 

by broad belts of surficial deposits. Parts of all the 

low:-angle faults dip downward in one direction or 

another, but thus far no long low-angle fault in the 

eastern part of the Basin and Range province has 

been so adequately mapped throughout its length as 

to show how extensive a particular dip is or to reveal 

clearly the fault's age relation to the folds associated 

with it. For these reasons and others, correlation of 

faults between ranges has not been conclusive. 

I believe that the Connors Pass area contains some 

thrust faults and some glide faults and that it has 

undergone regional uplift and normal faulting. Some 

of the low-angle faults may have begun as thrust 

faults and later may have become glide faults. 

GLIDE FAULTS 

Some flat-flying faults are clearly glide faults. 

These faults are overlain by rock masses that range 

in size froni small slump blocks to glide plates many 

square miles in extent. The gravity origin of slump 

blocks is widely known from studies elsewhere; many 

are well exposed or have been drilled, and many have 

been studied during movement. In the slumped areas 

mentioned on page 73, the material overlying the 

small glide planes is broken into discrete blocks, which 

are tilted upslope, as indicated by the terraces and 

depressed areas. Such movement requires a concave 

local glide surface. Slump blocks are derived from 

areas a relatively short distance upslope from the 

present site of the blocks, for . many blocks lie downslope from topographic embayments in rocks like 

those in the slump blocks. Some slump blocks are 

moving ·at the present time, others moved in the 

recent past, a:q.d still others, such as the slump or 

debris slide of shattered shale and limestone along 

Grasshopper Canyon and possibly some of the blocks 

of Ely Limestone included in Chainman Shale, moved 

during Pleistocene or. early Recent time. Tectonic 

forces may have set the stage for the movement of the 

slump blocks by increasing the local relief and by 

enabling streams to undercut certain blocks and thus 

leave them·inadequately supported, but the chief moving force has been gravity. 

The plates of Tertiary conglomerate and volcanic 

rock adjacent to Cave Creek have sonie structural 

features in common with the slump blocks, these similarities indicating that their origin was similar to 

that of the slump blocks. Large discrete plates of 

these rocks were · rotated heel down (pl. 1, section 

111-Llf'; pl. 3, fig. 12), and, although of several orders 

of magnitude larger than the slump blocks in the 

area, these plates are of relatively local extent; they 

are not klippen of more extensive thrust or glide 

plates. The lower surface of the larger plate at least 

is probably saucer shaped and concave upward. The 

plates lie at the foot of structurally and topographically high areas, which were uplifted before, as well 

as after, the plates came to their present position. 

They are much less broken than the typical slump 

blocks, ·perhaps because of their greater size and 

strength. The combined evidence then, though only 

permissive, suggests that these large plates were glide 

faulted from a position slightly higher than the summit -of Cave Mountain. The rocks , of the eastern 

part of the large plate were rotated about 40° as they 

moved down ward and westward, thereby pushing the 

rocks of the western part, with little or no rotation, 

over a surface eroded on the . Chainman Shale. If 

one assumes that the axis of rotation of the eastern 

part of the block was not shifted laterally and that 

the small pipe of quartz :latite vitrophyre was intruded at right angles to the bedding of the host 

rocks, the pipe .may be projected beneath the glide 

plate (pl. 3, section E-E'). The projected position 

of the ·-pipe would then coincide with a north-trending 

normal fault, extending from NW~ sec. 25, T. 15-N., 

R. 65 E., to SE;{b sec. 12, T. 14 N., R. 65 E., along 

·which other igneous bodies were intruded. If," as 

seems probable., the axis of rotation was nearly stable, 

the distance of movement along the glide fault was 

about 3,500 feet. _ 

Certain features in the large blocks ·of Ely Limestone widely scattered on the Chainman Shale indicate that they too are glide -plates, though this evidence is not as convincing as is that in ·the plates of 

conglomerate and volcanic rock. The blocks of Ely 

Limestone considered as possible glide plates are those 

1-2 miles north of The Narrows along Steptoe Creek, 

at Taylor triangulation mark, and ·near the Aspen 

Spring in the middle of the quadrangle, b~t not the 

smaller blocks already mentioned as constituent~ o:f 

slump blocks or those that ·extend along small highangle faults. In these large blocks, the bedding makes 
STRUCTURAL. GEOLOGY · '75 

moderately high ae:gles with the low-angle faults beneath the blocks and the blocks are internally broken 

by faults, along which the beds have been tilted. This 

structure is possibly also illustrated at a lower horizon by the much-repeated Joana Limestone along 

Steptoe Creek (fig. 12) ; inasmuch as the Joana in 

these blocks generally dips to the east or northeast 

and the surface beneath the blocks is flat rather than 

saucer shaped, the blocks could be the base of a large 

glide plate derived from a single area to the east or 

northeast. The fact that there was more rotation of 

the beds in the blocks of Ely Limestone north of the 

peak at Taylor triangulation mark (near the glide 

plates of conglomerate and volcanic rock) than in 

those farther south also suggests a source area nearby 

to the northeast. These blocks may be remnants of 

one or several large glide plates that moved southwestward from a structurally high area, underlain 

by Cambrian and Precambrian rocks, about 10 miles 

to the northeast, but there also is some indication that 

they are remnants of the upper plate on a thrust fault. 

THRUST FAULTS 

Evidence bearing on the origin of the low-angle 

faults within the Paleozoic rocks is available within 

the Connors Pass quadrangle, as well as in the surrounding region, but neither approach leads to a 

conclusive interpretation of how they originated. 

Two somewhat related lines of reasoning, based on 

observations within the quadrangle, have a bearing 

on whether the faults are thrust or glide faults, or 

possibly both. First, the distribution of structural 

features resulting from compressive stress and .. the 

uniformity of the_ direction of that stress indicate the 

minimum extent of the stress field associated with the 

faulting. Second, the differences in styles of deformation of the rocks above and ·below the Schell Creek 

Range fault suggest differences in the environment of 

deformation, which could lead to a hypothesis of 

thrusting on some .low -angle faults and gliding on 

others. 

In the Connors Pass quadrangle there is more evidence of compressive deformation in the rocks beneath the Schell Creek Range thrust · than in those 

above it. For instance, between lower Cooper Canyon 

and U.S. Highway 6-50-93, compressive stress of at 

least local extent is indicated by the imbrication- of 

small slices of the Lincoln Peak Formation and of 

the lowest limestone in the overlying Upper Cambrian and Lower Ordovician limestone (pl. 1, fig. 12). 

More extensive compression is indicated by widespread 

gentle folding throughout the Lincoln Peak Formation, and the consistent northward strike of these 

fold . axes suggests that the compressive stress was 

fairly uniform. The tighter smaller folds close beneath the thrust fault were formed independently of 

the larger open folds; they are ·drag folds formed in 

response to very local and relatively intense shearing 

stresses. Only one suggestion of compressive deformation can be cited in rocks above the thrust fault. On 

the south side · of the klippe at Taylor triangulation 

mark, part of the Ely Limestone (pl. 1, section N-N') 

has been repeated along two subsidiary low-angle 

faults. On the basis of compressive deformation 

within thequadrangle, then, the small low-angle faults 

Load small Load large Load small Load large 

~~~~~ Glide faults Thrust faults ~ 

Volcanic rocks (black) and 

conglomerate at Cooper 

Summit 

IDEALIZED STRUCTURES 

Joana Li mestone(black) 

along lower Steptoe 

Creek 

Sevy Dolomite (black) 

northeast of Cave Creek 

SIMILAR STRUCTURES IN THE CONNORS PASS QUADRANGLE 

Lincoln Peek Formation 

(Stippled) south of ~ower 

Cooper Canyon 

FIGURE 12.-Drawings showing comparison between idealized and actual patterns of fault deformation in rocks subjected to 

stress, by overriding glide or thrust plate. Horizontal scale almost equal to map scale. 
76 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

above the Schell Creek Range fault may be glide 

faults but the ones beneath it could be thrust faults. 

The contrast in local styles of deformation between 

the Tocks above and below the Schell Creek Range 

thrust may be due to differences of environment. The 

rock above the fault is not very strongly deformed . 

and is broken chiefly by normal faults, many of which 

are younger than the thrust. Local evidence permits 

some of the low-angle faults that occur within the 

upper plate to be interpreted as glide faults, though 

some small plates may first have moved on thrust 

faults. The rock beneath the Schell Creek Range 

thrust fault is more strongly sheared and is locally 

drag folded and recrystallized. This difference in 

style of deformation cannot be explained by differences 

in lithology alone, for in some places the fault brings 

rocks of similar lithology but different degree of 

deformation in contact, and there are several bodies of 

incompetent rock in the upper plate as well as in the 

lower. However, the difference in style of deformation can be explained if the rocks beneath the Schell 

Creek Range thrust, and perhaps that fault itself, 

were deformed at much greater depth than that at 

which the rocks above the fault were deformed. These 

two environments of deformation may, but need not, 

indicate that the low-~ngle faults include both thrust 

and glide faults. When combined with the line of 

reasoning based on the extent of compressive stresses 

in the older rocks, the idea that there are both thrust 

and glide faults in the quadrangle has considerable 

merit, but convincing evidence is unavailable. Therefore, on the basis of local evidence alone I am sympathetic with DeSitter's (1956, p. 291) point of view 

that "* * * it is very much a question of taste how 

much one believes should be accounted for by thrusting and how much by gliding." 

Regional evidence indicates even more clearly that 

stresses were uniform and widespread. The deformation. is all of the same general style, and the direction 

of movement seems to have been east-northeastward 

in practically all areas. The uncertainty about the 

direction of movement implied by the words "seems to 

have been" is admittedly deliberate, for neither the 

abundance, the persistence, nor the location of the evidence with respect to particular low~angle faults is 

usually reported in the literature. In many nearby 

ranges in which there are abundant low-angle faults, 

the largest fault is not structurally the lowest fault, 

imbricated fault slices are usually absent or small, and 

younger rocks have typically been faulted over older 

ones. Although low-angle faults in adjacent ranges 

follow approximately the same stratigraphic horizons 

along incompetent rocks, correlation of specific faults 

from range to range has still to be demonstrated. The 

relation between the low-angle faults and the domes 

gives a further indication of the widespread distribution of the stress field associated with the faults. 

The coincidence of much of the low-angle faulting 

with the top and flanks of the major dome in the 

northern Snake Range and the minor domes like those 

just north of the Connors Pass quadrangle (fig. 11) 

suggests a close genetic relation between domes and 

faults. The faults are not glide faults formed separately about the domes, for there is no radial direction 

of transport of the fault plates, and the most intense 

faulting seems to lie on the tops of the domes rather 

than on their flanks. Alternately, then, the genetic 

relation between the low-angle faults and the domes 

must involve a plate or plates of regional extent. It 

is unlikely that the domes formed after the low-angle 

faults, for the coincidence in their distribution can not 

be explained then. However, it does seem likely that 

the domes were formed before or during the time in 

which the regional fault plate moved, the domes being 

an obstacle beneath the plate above which the deformation was severest. Although it is interesting to point 

out here why the domes are among the oldest structured features of the region, the essential point is that 

the low-angle faults are regional and were propelled 

by sufficient energy to move over a number of fairly 

large obstacles. 

A conventional approach to explaining the origin of 

low-angle faults of regional extent involves the identification of either a root area from which lateral 

stresses were transmitted, or a slope down which a 

glide plate could move, but both are conspicuously 

missing. In central Nevada there is no large upthrust 

or intrusive mass that might pass for a root area; 

likewise, there is no record of a structurally high area 

of sufficient magnitude, even accepting the gentlest 

of slopes, and of appropriate age to have been the 

source of a glide plate of regional extent. These unresolved difficulties indicate that perhaps some less conventional approach must be explored. 

The difficulty in resolving the question of where the 

root area of the thrust faults is located may indicate 

a weakness in our concept of what a root area is like. 

The root of a thrust plate is commonly pictured as a 

simple piston of rock, as m:ty be exemplified by an 

expanding magma chamber that pushes out against its 

host rock. Perhaps a root may also consist of a body 

of rock in which the pore pressure is equal to the 

lithostatic pressure, in the general sense used by 

Hubbert and Rubey (1959), and in which local lateral 

and vertical variations in pressure help to produce 

lateral movement of the rock as an indirect result of 
ECONOMIC GEOLOGY 77 

the. load itself. Local variations in the pressure 

balance arise from variations in the porosity and other 

properties of the rock and in the amount of pore 

fluid present. This balance would a!so b~ affected by 

the rates of deposition or :.·os~on of overlying sediments, as well as by g~mtle regional tilting c:r a 1_~ush 

from a root area. !fost of these following factors 

have varied throughout the region: lateral fac:es 

changes and metamorphic changes that would change 

the porosity of the rocks, rates of deposition during 

the late Paleozoic, and the rate of unload:ng of 

sediments. 

In accordance with Misch's ( 1960: p. 33) view that 

the low-angle faults are Late Jurassic or Early 

Cretaceous, they must have formed under extremely 

high lithostatic pressure; for at the end of Early 

Jurassic time, the thickness of rock above the Precambrian was about 6.5 miles and that above the 

Cambrian about 5 miles. At such depths . the lithostatic pressure and pore fluid pressure may well have 

been equal. Perhaps, then, some of the low-angle 

faults in the Schell Creek Range, which generally cut 

out beds and rarely repea~ed them, were formed in a 

root area. Conceivably, too, the zone in which pore 

fluid pressure balanced lithostatic pl'essure may have 

shifted upward as sedimentation continued. The rocks 

may thus have been squeezed out laterally at successively higher horizons, and the time during which 

they were being Equeezed out could have been much 

longer than the time that would have been available if 

the faults were formed during a single orogenic 

period. If this hypothesis is correct for the rocks in 

the Schell Creek Range, or at least for the rocks of the 

lower plate of the Schell Creek Range thrust, the 

lithostatic pressure would never have been as great as 

the weight of the entire sedimentary column. Where 

relative ages are known in the Schell Creek and Snake 

Ranges, the low-angle faults at the higher stratigraphic levels are consistently younger than those at 

the lower stratigraphic levels. They cannot all be 

assigned a Late Jurassic or Early Cretaceous age 

unless they are assumed to have been formed during 

one orogenic period, but in accordance with the 

hypothesis of lateral squeezing only the youngest fault 

need be of that age. Although these unconventional 

ideas do not fully explain the origin of the low-angle 

faults, they do point to some approaches that may 

have fewer shortcomings than the. usual hypotheses 

regarding thrusts and glide f~ults of this region; thus 

far our facts are few and our assumptions many. 

REGIONAL UPLIFT AND NORM'AL FAULTS 

The regional uplift or uplifts recorded, in the Schell 

Creek Range and in most other parts of the eastern 

Great Basin, by the major angular unconformity 

between Paleozoic marine rocks and Cretaceous or 

Tertiary continental reeks caused an enormous change 

in the regional structural environment, from the great 

depths at which the thrust faults app:-ar to have 

formed to near the surface. The cumubtive uplift 

amounted to many thousands of feet-in places to 

tens of thousands of feet-the thickness of the Paleozoic and Mesozoic rocks that have been removed by 

erosion. No evidence of the cause. of this major uplift 

has been found in this quadrangle, but a relaxation 

or cessation of the forces involved may have produced 

the normal faults of Tertiary and Quaternary age and 

permitted the intrusion and · extrusion of magma. 

Inasmuch as the normal faulting and volcanic activity 

were recurrent, the forces producing tension in the 

crust must have been discontinuous or most have 

varied in intensity. Some of the low-angle faults, at 

least those beneath the Tertiary rocks, are believed to 

have been caused by gravity in areas of high relief 

adjacent to Tertiary normal faults. 

ECONOMIC GEOLOGY 

Scattered mining districts in the region around the 

Connors Pass quadrangle have produced chiefly silver, 

tungsten, gold, lead, zinc, manganese, and beryllium, 

but few mines are now being operated in the region 

other than the one in the large porphyry copper body 

at Ruth, in the Egan Range (fig. 1) . Much of the 

mineralization lies in or near granodiorite or quartz 

monzonite stocks and related dikes, though not all of 

these intrusive bodies are associated with mineralization. 

Several small areas within the quadrangle are mineralized, but aside from the Taylor mining district the 

duration of mining activity in them was brief. Silver 

was the chief metal produced, but small quantities of 

gold, copper, lead, zinc, antimony, and tungsten were 

also extracted, and barite and fluorite were locally 

prospected. At the time of the. field mapping, attempts 

were being made to recover antimony, and several 

areas '\Vere being explored for other metals by drilling 

and by sinking a shaft. Currently some silver ores 

are being shipped from the Taylor district, and further exploration activity is concentrated along the 

eastern edge of the district. 

TAYLOR MINING DISTRICT 

The Taylor mining district occupies several square 

miles low on the west flank of the Schell Creek Range 

and 3 miles northwest of Connors Pass. Silver was 

discovered in the district in July 1872 (Whitehill, 

1873, p. 77), and according to Hill (1916, p. 200-202), 

who briefly described the geology and ore deposits of 
78 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

the area at a time when a little high-grade ore was 

still available, the mines in the area were most active 

from 1872 to 1878. Available production data are 

summarized in table 13. 

Although Lower Devonian to Recent rocks are 

exposed in the district, only some of the Middle 

Devonian to Lower Mississippian rocks are mineralized. · These rocks include much limestone and shale 

and some dolomite that are capped by a small ·amount 

of dacite lava and tuff and cut by numerous dikes of 

porphyritic rhyolite (fig. 13). Most of the mineralized rocks dip gently to moderately steeply eastward, 

except along the west side of the district, where both 

the direction of dip and the inclination are more 

varied. These rocks are cut by many normal faults, 

most of which trend north to northeast and dip 65°-

700 SE. The Taylor fault, however, which · is the 

largest, trends northwestward and dips steeply westward. One fault in the district is probably . a lowangle fault. The stratigraphic displacement on the 

Taylor fault exceeds 1,000 feet where it brings unmineralized rocks against the mineralized rocks, but 

on the ot;her faults it is in the order of hundreds of 

feet and diminishes northward. 

The limestone of the Guilmette Formation and the 

Joana Limestone contains stringers, sheets, pods, and 

larger irregular bodies of siliceous rock, which form 

dark-brown to dark-gray ledges and ribs that project 

above the level of the adjacent limestone. Tabular 

bodies of siliceou~ rocks are a]ined along some of the 

north- to northeast-trending faults and along some 

north-striking stratigraphic units. Many of the 

larger silicified bodies grade into the limestone host 

rocks through zones of weakly silicified rock, in which 

quartz stringers are common ; the separation of limestone f~agments . by a siliceous matrix indicates a replacement of limestone by silica. The silica has preferentially .repl1aced thin-bedded shaly Umestone of 

member .. c . of the Guilmette Formation, especially its 

lower part, · and it has also replaced, to a lesser extent, 

the thin '-bedded limestone at the top of the Joana 

Limestone~ Some · of the· contacts, however, along the 

smaller tabular bodies are strongly sheared and relatively abrupt; and . some of the silicified bodies are 

sheared and brecciated. Near the largest open pit 

north of Taylor townsite; the shear planes commonly 

strik~ N. 25° W.-N .. 40° E. and dip vertically to 

5Q0 'f. Near.the large fault .-that runs northeastward 

through the district, the attitudes of the shear planes 

;tpproach that of the , fault, this· relation indicating 

that the_ shears feather out. a way from the f.ault. 

Carbona~ . and quartz . veinlets cut the silicified rock 

and commonly fill the interstices in the brecciated 

rock. 

The district contains many small strongly altered 

but · unmineralized porphyritic rhyolite dikes. Where 

they cut slicified rock the dikes are subparallel to the 

nearby shear · planes. 

Most of the ore has been mined from opencuts and 

from a maze of shallow drifts extending along the 

main silicified horizons in the central part of the 

district. About 20 shafts and inclines are more than 

50 feet. deep, and some may be more than 200 :feet 

deep. None of the deeper workings were entered 

and, although the pits and shallow passages are accessible, their floors are commonly covered with waste 

material. During part of the time in which the area 

was being mapped, a small stibnite prospect was being 

mined east of the townsite. 

Ore minerals are scarce and inconspicuous in ·most 

of the workings. Some bluish-green mineral, possibly 

chrysocolla, occurs in small veinlets and fracture coatings in the central and northern part of the district. 

Azurite and malachite are less common, and some 

rock fragrnents are coated with a dark-gray sooty 

material, probably either a copper or a manganese 

mineral. Limonite and other secondary iron minerals, 

some having conspicuous boxwork structures, are common in the prospects in the southern part of the 

district. A barite vein roughly follows a locally 

faulted contact between the Guilmette Formation and 

Pilot Shale about 1,000 feet northwest of the unnamed 

9,200-foot peak in the northeast corner of the district. 

Stibnite is abundant in pods of silicified Joana Limestone east and northeast of the central part of the 

district and is most abundant at the prospect in an 

area of much faulted Chainman Shale and silicified 

and mineralized Joana Limestone. The silicified limestone is f11actured and brecciated, and the :fragments 

are cemented with stibnite, calcite, silica, and a bluishgreen copper(?) mineral. Nearby are some porphyritic rhyolite dikes which appear· to be younger than 

the faults that cut the silicified limestone. 

Spectrographic analyses of 40 samples from six of 

the larger workings were made tO supplement the 

scanty mineralogical data and to show the distribution of silver in the silicified ~ock (table 14).- Three 

of the workings extend almig the east side of the 

central part of the district, and the others, which lie 

west of the central part of the district, . are separated 

from these by a normal fault~ The workings from 

which collections 17-22 were made are identified on 

figure 13. The samples were obtained either from 

rock in place or from waste ·in ·the bottom of the pit 

and contain fragments typical of' the rocks exposed 
ECONOMIC GEOLOGY 

TABLE 13.-Production record of the Taylor mining district 

[Only those years listed for which production was recorded. Ore production: includes ore from -reworked tailings] 

Number 

Year of mines 

producing 

1883_------ ---------- 1884_- - - - - - - - - - - - - - - - 1885_------ ---------- 1886_- - - - - - - - - - - - - - - - 1887------- ------- ---

1888_------ ---------- 1889 _______ ----------

1890_------ ---------- 189 L _____ - ----------

1892_------ ---------- 1936 _______ ----------

1940 ___ ___ _ ----------

Ore produced (short 

tons) 

1, 875 

5, 545 

8, 935 

6, 746 

6, 644 

4,428 

999 

907 

1, 277 

463 

3, 127 

Metals recovered 

Mines or mining 

companies known 

Compiled by Couch and Carpenter (1913) 

Combined Ag, Au, Cu, and Pb __________ __ ________ -------------------- - ____ do__ ______________ ______ _________ ___ __ __ ____ Monitor, Sunrise ___ _ _____ do __ _______________ ____ __ ____________________ ___ do ____________ _ _____ do __ ____ ________________________________________ do ____________ _ 

_____ do__ ___ ______ __________________ ____ ________ Monitor, Sunrise, 

Argus. _____ do ______________________________ _______ ___ ______ do __ ___ __ _____ _ _____ do ____ ______ ___ ___________ __ _____ ___ ____________ do ____________ _ _____ do __ _________ ___________________________________ do ____ ______ __ _ _____ do ______________________________________________ do ____ ________ _ 

_____ do ________________________ ___________ --- _____ do _____ -------

___ __ do __________ ___ ___ _______________ __ ________ Oxborrow and 

Mckerrzie. 

18, 865 ___ __ do __________ ._________ ____________________ __ Ox borrow and 

Compiled by U.S. Bur;mu of Mines (1937-61) 

Mckenzie, and 

Ely Gold Mining 

Co. 

-----------------------------.-----.-----

I Zn I Sb 

1935 _______ 2 15, 442 

1936 _______ 3 29, 265 

1937 _______ 3 1, 271 

1938 _______ 1 243 

1939 _______ 2 1, 320 

1940 _______ 9 12, 932 

1941_ _____ _ 6 14, 244 

1942 _______ 5 9, 084 

1946 ___ __ __ 3 3, 284 

1947 _______ 3 2, 957 

Au Ag 

Fine ounces 

288 104, 656 

887 176,938 

18 8, 002 

4 1,433 

28 8, 365 

385 107, 029 

418 199, 900 

208 90, ,1)44 

37 12,892 

74 15, 532 

Cu Pb 

Pounds 

_ ___ __________________________ Ely Mining Co _____ _ 

_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Gore Mineral Farm, 

Monitor, Sunrise. ___ ___________________________ Mineral Farm ______ _ 

500 10, 600 -------- ------ --------- ----------- _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Goodman mine 

(Nevada Sunshine Mining Co.). 

1948_______ 3 102 897 1, 300 17, 100 7, 200 --- --- -------------------- 1949______ _ 1 13 2 1, 134 -- - ----- -------- -------- ------ --------------------

1950_------ 2 411 6 6, 046 -------- -- ------ -------- ------ -------------------- 1951______ _ 1 190 4 1, 411 -------- ------ -- -------- ------ -------------------- 1952 ____________________________________________ :._ _______ _ - ________ -------~ _____ _ Mineral Farm, 

Garder Mining 

Co. 

1953-54 ____________________________________________________________ _:_ ___________ Taylor mine, Imperial Nevada Co. 

Estimated by Drewes 

79 

Total value 

' $66, 187 

150, 617 

258,914 

193, 020 

161,975 

111, 181 

43, 641 

21, 414 

25, 596 

7, 994 

22, 121 

118, 965 

$1, 181, 625 

$85,285 

168, 093 

6, 820 

1, 066 

6, 658 

89, 585 

156, 781 

71,667 

12, 948 

16, 646 

5, 113 

1, 096 

5,682 

1, 417 

$628,857 

1959_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ Merrimac claims ____ I Several 

thousand 

dollars 

(for Sb). 
80 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

R. 65 E. 

EXPLANATION 

Gravel 

Latite and dacite flows 

and tuffs 

[2] 

Granophyric rhyolite dikes 

Ely Limestone 

Chainman Shale 

Joana 

~ 

~ 

Limestone 

Pilot 

-

Shale 

Guilmette Formation 

Dgc, member c 

Dgb, member b 

Dga, member a 

Sevy Dolomite 

GO 

Silicified rock 

----- Contact 

-------%-· 

Fault 

Dotted where concealed. U, upthrown 

side; 

~ 

D, downthrown side 

Thrust fault 

Teeth on overriding block 

":7" 

Strike and dip of beds 

70 

-dStrike and dip of overturned beds 

II 

Shaft 

~ 

Large pit 

X 

Prospect and small pit 

y 

Adit 

>-

}~ 0 

z 

<( 

z 

~ 

FIGURE 13.-Geologic map of the Taylor mining district, in the western part of the Connors Pass quadrangle, modified from 

Drewes (1962). Silver ore occurs in some silicified bodies. Numbers 17-22 at workings indicate sample localities. 
... "' 0 

"' 0 

"' 0 

"' ... 

s ample 

loc. 

:fig. 

13) 

--

17a 

b 

c 

d 

e 

f 

g 

18a 

b 

c 

d 

e 

19a 

b 

c 

d 

e 

f 

20a 

b 

c 

d 

e 

f 

~ i 

21a 

b 

c 

d 

e 

f 

22a 

b 

c 

d 

e 

f 

g 

Lab. 

No. 

61-

242S 

243S 

244S 

245S 

246S 

247S 

248S 

249S 

250S 

251S 

252S 

253S 

254S 

255S 

256S 

257S 

258S 

259S 

273S 

274S 

275S 

276S 

277S 

278S 

279S 

280S 

281S 

260S 

261S 

262S 

263S 

264S 

265S 

266S 

267S 

268S 

269S 

270S 

271S 

272S 

TABLE 14.-Semiquantitative spectrographic analyses of rocks from the Taylor mining district 

[Analyses, in parts per million, by E. F. Cooley. Be <1, Ge <20, Ga <20, Sn <10, Sc <10, Bi <10, In <50, Ti <100, W <50, Nd <50, Ta <50] 

Visible 

miner- Rock type aliza- Fe Mg Si Cu Pb Zn Sb Ag Mn As Ti Cd La B Or Ba Sr 

tion 

------------------------------------------

Silica breccia _________ 

·au==== 

15,000 5, 000 500,000 500 1, 500 700 5, 000 1, 000 300 <1, 000 1, 500 <50 <50 50 50 150 70 Silica ______ ---------- 7, 000 1, 500 300,000 5, 000 >10,000 10,000 7, 000 150 500 1,000 1, 500 200 <50 20 30 100 200 

Calcite vein in silica_ 1, 500 2,000 70,000 200 300 <200 200 200 >10,000 <1, 000 200 <50 <50 <10 10 20 1, 000 Silicified limestone ___ 1, 500 30,000 200,000 500 1, 000 1, 000 200 200 5,000 <1, 000 200 <50 <50 10 10 50 200 Silica breccia _________ 5, 000 2, 000 500,000 500 700 1, 000 1,000 2,000 200 <1, 000 700 <50 <50 50 20 200 50 Vuggy silica __________ 5, 000 1, 500 500,000 500 1, 000 500 3, 000 3, 000 100 <1, 000 700 100 <50 50 20 100 50 Silica breccia and 5, 000 1, 500 500,000 200 700 -500 5, 000 700 150 <1, 000 500 <50 <50 30 15 100 10 

quartz vein. 

Altered limestone ____ 

·au==== 

5, 000 2, 000 300,000 1, 500 3, 000 5, 000 5,000 1, 000 200 1, 000 700 100 <50 20 20 100 500 Silica ________________ 2, 000 5, 000 100,000 10,000 >10, 000 >10, 000 10,000 1, 000 700 1, 500 500 1, 500 <50 20 15 100 <10 Vuggy silica __________ 3, 000 1, 000 500,000 1, 000 2, 000 10,000 3, 000 150 50 <1, 000 500 150 <50 20 15 150 20 

Calcite vein and 5, 000 3, 000 100,000 700 1, 500 5, 000 2, 000 150 1, 500 <1, 000 1, 000 150 <50 15 20 50 700 

silica. Silica. _________ ____ -- Cu ____ 20,000 1, 500 300,000 >10, 000 >10, 000 >10, 000 >10, 000 5, 000 1, 500 5, 000 2, 000 5, 000 <50 50 30 300 70 

Dolomite breccia ____ _ Cu ____ 10,000 1, 500 300,000 5, 000 >10, 000 >10, 000 7, 000 2, 000 500 <1, 000 1, 500 300 <50 30 20 1, 500 200 Silicified limestone ___ Cu ____ 10,000 1, 500 500,000 3, 000 >10, 000 2,000 7, 000 2,000 200 <1, 000 1, 500 100 <50 50 30 200 100 Silica breccia _______ __ 

·au==== 

5, 000 1, 500 500,000 2, 000 10,000 >10, 000 3, 000 1, 500 700 <1, 000 1, 000 200 <50 30 30 1, 500 200 Silica. _______ -------- 10,000 500 300,000 >10,000 >10, 000 >10, 000 >10, 000 5, 000 150 7, 000 500 3, 000 <50 30 20 150 20 

Limestone replaced 1, 000 5, 000 15,000 1, 500 3, 000 2, 000 500 150 500 <1, 000 300 50 <50 <10 <10 1, 000 300 

by quartz and calcite. 

Silicified limestone ... -------- 5, 000 1, 500 500,000 1, 000 3, 000 2,000 1, 000 1, 000 50 <1, 000 1, ooc 50 <50 50 20 200 50 

Silica breccia _________ Sb ____ 1, 000 500 500,000 200 20 500 >10, 000 150 50 1, 000 200 <50 <50 20 20 500 50 

Calcite vein and cu __ __ 5, 000 1, 500 100,000 10,000 3,000 10,000 5, 000 :!., 500 2, 000 1, 000 100 150 <50 <10 10 50 200 

silicia. Silica breccia _________ Cu ____ 1, 500 500 300,000 >10, 000 1, 000 10,000 500 150 500 <1, 000 200 <50 <50 20 10 150 50 

Silicified limestone Sb ____ 1, 500 1, 000 300,000 1, 000 2, 000 500 7, 000 150 10 <1, 000 1, 500 50 <50 20 15 700 150 

Silica __ -------------- Sb ____ 1, 500 500 500,000 700 200 500 >10, 000 700 10 1, 000 150 <50 <50 10 20 1, 500 100 

Silicified limestone cu ____ 20,000 1, 000 200,000 >10, 000 >10, 000 >10, 000 >10, 000 1, 500 3,000 1, 000 200 200 50 20 10 700 500 

Silica and stibnite Sb ____ 1, 000 500 150,000 1, 000 150 1, 000 >10, 000 3,000 50 2,000 70 <50 <50 <10 10 >10, 000 100 

Silica ____ ------------ cu ____ 5,000 500 300,000 >10, 000 >10, 000 >10, 000 >10, 000 150 3, 000 <1, 000 200 <50 100 50 10 700 20 Vein calcite __________ 300 1, 500 5,000 500 200 1, 000 5,000 15 700 <1, 000 <10 <50 <50 <10 10 200 500 

Silica breccia _______ __ -------- 2, 000 1, 500 500,000 500 500 2,000 200 150 200 <1, 000 1, 000 <50 <50 50 10 150 500 Vuggy silica __________ 1, 500 1, 000 500,000 700 1, 000 2, 000 1, 000 1, 500 20 <1, 000 700 50 <50 30 10 100 10 Silicified limestone ___ -------- 1, 000 1, 000 500,000 300 300 3, 000 300 1, 000 700 <1, 000 150 50 <50 20 15 150 100 Silica ________ -------- 1, 500 700 500,000 300 300 3, 000 200 150 100 <1, 000 300 <50 <50 20 10 100 20 Vuggy silica __________ 500 500 500,000 150 70 <200 <200 70 100 <1, 000 100 <50 <50 20 10 70 50 

Silcified limestone -------- 1, 500 1, 000 500,000 150 200 300 <200 150 300 <1, 000 200 <50 <50 30 10 100 100 

breccia. 

Silica and calcite -------- 700 1, 000 200,000 150 100 200 200 200 2, 000 <1, 000 150 <50 <50 20 10 50 200 

veins. __ ___ do ________ ______ - -------- 2,000 1, 000 500,000 500 1, 000 10,000 3, 000 500 300 <1, 000 700 100 <50 30 10 70 150 __ ___ do _______ ___ ___ -- 1, 000 2, 000 200,000 200 2,000 1, 000 2, 000 2, 000 2,000 <1, 000 150 100 <50 10 10 20 700 Vuggy silica __________ 2, 000 700 500,000 300 700 1, 000 1, 000 2, 000 150 <1, 000 300 <50 <50 30 10 100 50 ____ .do. ____________ -- 1, 500 1, 000 300,000 150 500 1, 500 500 700 700 <1, 000 200 50 <50 20 10 50 100 

Dolomitic lime- 500 2,000 20,000 70 70 500 <200 70 300 <1, 000 50 <50 <50 <10 < 10 -30 1, 000 

stone. 

Silica._-------------- -------- 1, 000 1, 000 300,000 70 100 1, 500 200 100 200 <1, 000 200 <50 <50 20 10 50 100 

-- ---

Zr Ni Co 

------

200 7 <10 500 10 <10 10 5 <10 150 10 <10 300 10 <10 200 7 <10 150 5 <10 

200 5 <10 100 50 <10 200 5 <10 200 5 <10 

200 20 <10 

300 10 <10 200 10 <10 100 20 <10 150 10 <10 10 <5 <10 

500 5 <10 

30 20 <10 30 <5 <10 

200 10 <10 500 <5 <10 10 50 <10 20 10 <10 <10 20 <10 150 10 10 

<10 <10 <10 

300 5 <10 300 <5 <10 70 <5 <10 200 5 <10 100 <5 <10 200 5 <10 

50 <5 <10 

300 10 <10 20 <5 <10 100 7 <10 70 5 <10 10 <5 <10 

30 7 <10 

v 

--

70 

30 

30 

100 

50 

20 

20 

50 

15 

30 

50 

50 

30 

30 

30 

20 

30 

20 

15 

10 

10 

20 

10 

15 

10 

15 

10 

20 

10 

20 

10 

<10 

20 

10 

15 

20 

10 

10 

20 

15 

Mo y 

---

20 10 

<5 15 

<5 15 

<5 10 

<5 10 

<5 10 

<5 10 

<5 10 

<5 15 

<5 10 

<5 20 

20 20 

500 10 

10 20 

1, 500 20 

20 20 

20 20 

<5 20 

<5 <10 7 10 

<5 10 

100 10 

5 <10 10 20 

<5 10 

10 15 

<5 15 

7 10 

<5 10 

<5 <10 

<5 10 

<5 10 

<5 10 

<5 10 

<5 10 

5 10 

<5 10 

<5 10 

<5 10 

<5 <10 

t:_:rj 

c 

0 

z 

0 

~ ~ 

c 

0 

t:_:rj 

0 

t'1 

0 

~ 

00 

1--l 
82 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

in the walls nearby. Both field observations and 

analytical results showed that the mineralization is 

strongest in a zone extending from the large pit, 

locality 20, on the northwest side of the central part 

of the district to locality 19, slightly southeast of the 

center of the district. 

Bluish-green copper(~) minerals can be recognized 

in any sample that contains as much as 300ppm of 

copper. Stibnite or a secondary antimony mineral 

is recognizable in any sample containing as much as 

10,000 ppm of antimony, unless the sample also contains large quantities of secondary minerals of other 

base metals, which mask secondary minerals derived 

from antimony. No lead, zinc, or silver minerals 

could be identified, even with the aid of the analyses. 

Rocks having a large content of silver or base metals 

most commonly consist of brecciated silica, less commonly of nonbrecciated silica, and least commonly 

of silicified limestone; much of the silicified rock, however, contains only small amounts of silver or base 

metals. 

Lead and zinc minerals are most closely' associated, 

copper is somewhat more widely distributed than 

lead and zinc, and antimony is not always associated 

with the other base metals. Silver tends slightly to be 

associated with antimony rather than with other base 

metals. 

The rocks were probably mineralized in late Mesozoic or early Tertiary time, apparently in the early 

part of the period during which the region was being 

subjected to tensional stresses. Siliceous solutions 

probably followed the main faults· and selectively replaced the impure limestones beneath ·the more refractory shales. The silicified rock was fractured by 

further adjustments along faults, and ore-bearing 

solutions also apparently followed the main faults and 

deposited base metals and silver in· the zones of 

severest brecciation . near the center of the district. 

Solutions of antimony and perhaps of silver retained 

mobility longer than those of other metals and thus 

ascended a little higher. Shortly after the mineralization, porphyritic rhyolite was intruded · along or 

near the main fractures. The siliceous solutions and the 

1nagma may both have been derived from a single stock 

that lies not far beneath the surface. Further movement 

along the faults trending north and northeast was 

succeeded by movement along those trending northwest and also, presumably, by the extrusion of the 

Tertiary latite and dacite. Still later the mineral 

deposits were altered and . secondary ·minerals were 

concentrated . near the surface. 

Guides to prospecting in the Taylor district 

(Drewes, 1962) place the chief emphasis on downdip 

exploration of the two mineralized horizons along 

which additional silica pods enriched in silver may be 

anticipated. Extensions of these horizons across some 

of the faults along the eastern edge of the district 

may also be . found by deep drilling. · 

CLEVE CREEK DISTRICT 

There are two groups of prospects and mines on 

quartz veins in the Cleve Creek district, but they were 

developed only a short time. One group of shafts and 

adits is scattered along the lower part of Cleve Creek 

ll/2 miles west of the Cleve Creek campground and 

extends to the crest of the hill south of the creek. 

These prospects are all in the Pioche Shale or the 

upper part of the Prospect Mountain Quartzite. Vein 

quartz and dolomite are abundant in the rubble 

around the shafts near the creek ; they contain traces 

of a black mineral, perhaps hematite or hiibnerite, and 

of a bluish-green copper( n mineral. South of Cleve 

Creek a shallow incline follows a quartz vein containing pyrite, bornite, and malachite in a limy bed in the 

Pioche Shale. In this area the alluvium and colluvium 

have a slightly anomalous base-metal content that extends east of the area of prospects (fig. 14). 

The Kolcheck mine and surrounding prospects lie 

high above the west side of the Kolcheck Basin, along 

the upper part of Cleve Creek. The workings are in 

the middle of the complexly faulted Pole Canyon 

Limestone. According to the U.S. Bureau of Mines 

(1953, v. 3, p. 672), 32 tons of ore, containing 3.15 

percent W03 , was shipped from the mine in 1953. 

Scheelite is probably the chief or only tungsten 

mineral. 

The prospects containing quartz, pyrite, malachite, 

&nd possibly hiibnerite' in quartzite and shale are similar to the deposits at and north of the Hub Mine 

Basin in the southern Snake Range (Drewes, 1954, 

p. 114), and the setting of the Kolcheck mine resembles that of the Minerva district, 10 miles south of the 

Hub Mine Basin. In the Hub Mine Basin and the 

Minerva district the mineralization is closely associated with a granodiorite stock or with porphyritic 

rhyolite dikes, this relation indicating that hydrothermal solutions may have emanated from a magma 

chamber to form a manganese tungstate in the quartzite and a calcium tungstate in the limestone. The 

mineralization in the Cleve Creek area may have 

originated in a similar manner to that in the southern 

. Snake Range but was less intensive. 

MINERALIZATION NEAR MAJORS PLACE 

Several shafts, adits~ and smaller prospects lie high 

on the east flank of the ridge about 11j2 miles north-
ECONOMIC GEOLOGY · 83 

west of Majors Place, and a few prospects l~e farther 

north on the ridge, about a mile south of Cooper 

Canyon. Some development work was done near 

Majors Place a few years before the area was mapped, 

but no production was recorded. Most of these prospects were dug in sheared shale of the lower part of 

the Lincoln Peak Formation, but several were extended a short distance into the top of the Pole Canyon Limestone, and those to the north were dug in the 

middle of the Pole Canyon. Rubble of vein quartz is 

widely scattered throughout this area, and the quartz 

veins at the prospects contain traces of a bluish-green 

copper ( ? ) mineral. 

Fluorite appears in two small prospects in Rattlesnake Knoll, just south of U.S. Highway 6-50 and 

about 4 miles east-northeast of Majors Place. Here 

the host rock is fragmental dacite vitrophyre, perhaps 

a flow agglomerate; fluorite fills some of the voids 

between the angular fragments, and some of the fragments are cut by fluorite veins. Most of the fluorite 

is light gray, but some of it is greenish or pinkish 

gray. This mineralization is the youngest in the area 

for it affects the dacite volcanics of Eocene and 

Oligocene ( ? ) age, and it may be related to that volcanism. 

OTHER MINERALIZATION 

Several adits and small prospects lie in Tamber lainc 

Canyon, about 3 miles south of the northwest corner 

of the quadrangle. A small amormt of silver ( ? ) ore 

was probably shipped from the largest adits, but production records are not available. The workings are 

in pods of silicified limestone in members b and c of 

the Guilmette Formation, along a zone that extends 

westward from the major normal fault trending northwestward across the canyon and continues beyond the 

. west boundary of the quadrangle. Quartz replaces 

limestone along northeast-trending fractures within 

the main east-trending zone. Some of the quartz is 

brecciated and sheared and contains later silica and 

coatings of brownish- and yellowish-gray material, 

and the mineralization is associated with the brecciated 

silicified limestone. No ore minerals were recognized, 

but silver was probably mined here as well as in the 

Taylor district. 

Other small silicified bodies are scattered thro~gho~t the quadrangle. Although I donot know wheth~r 

they are similarly mineralized or not, they closely 

resemble the larger silicified and mineralized bodies 

and . are probably of the same age. One group of 

silicified bodies is _ along a gently inclined fault in the 

Ely Limestone at the southeast end of the klippe west 

of Grasshopper Canyon. Another silicified body, o:f 

pipelike form, is at the' junction of several normal 

faults along Cooper Wash, SW%, sec. 33, T. 15 N., 

R. 65 E., and still another silica pod appears on the 

north wall of Cooper Canyon three-quarters of a mile 

east of the center of the basin, SW%, sec. 36, T. 15 N., 

R. 65 E. Several other silicified pods extend along 

the fault between the Arcturus Formation and the 

dacite vitrophyre volcanic rocks south of Cooper Canyon, in the projected position of SW%, sec. 8, T. 14 N., 

R. 66 E. The bodies along this fault are mapped as 

silicified Arcturus Formation, but they could be altered 

Ely Limestone or Guilmette Formation that has been 

faulted, for a small block of Chainman Shale also 

extends along the fault. Silicified rock along a fault 

in Chainman Shale at the head of Steptoe Creek, 

NW%, sec. 20, T. 16 N., R. 65 E., may likewise be 

infaulted silicified Ely Limestone, Joana Limestone, 

or limestone of the Guilmette Formation, all of which 

are exposed nearby. 

A small exploratory shaft was sunk in the Joana 

Limestone on a bench west of Steptoe Creek slightly 

more than a mile south of the north edge of the quadrangle. No mineralization was seen in the debris on 

the dump, but slightly . anomalous lead contents were 

found in some samples of alluvium collected a short 

distance downstream. Inasmuch as the shaft is less 

than 3 miles south of the Success mine, from which 

small amounts of lead, silver, and ·gold were reported 

to have been produced between 1907 and 1910 (Hill, 

1916, p. 198), it was perhaps sunk in search of a similar deposit. 

GENERAL GEOCHEMISTRY 

A general survey was made of trace-element content 

in alluvium and black shale (tables 15 and 16). Alluvium was sampled close to the range fronts and near 

the mouths of the large tributaries of the major watercourses. Samples of silt and sand were collected from 

at least 2 inches below the surface of the youngest 

deposits in the bottoms of dry washes or in sand bars 

next to running water. Most of the samples represent 

material derived from · drainage areas no more than a 

few square miles in extent, and all but a few drainage 

areas of any considerable size were sampled. Alluvium 

in unmineralized areas contained, on the average, 

about 2o ppm copper, 25 ppm lead, and 25 ppm zinc, 

which may be. considered background values of .those 

metals, but the tungsten content is below the thn~shold 

value of detection. Zinc background values increased 

somewhat erratically in areas underlain by rocks of 

late Paleozoic age, particularly in areas underlain by 

black shale. 
84 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

TABLE 15.-Semiquantitative analyses of lead, copper, and zinc content of alluvium 

[Analyses, in parts per million, from field-method wet tests in the laboratory by H. H. Mehnert, W. W. Janes, and K. W. Leong. Tungsten content <20 parts per million except for sample 69, which contains 20 ppm] 

Element Element Element Sampleloc. Lab. No. Sampleloc. Lab. No. Sampleloc. Lab. No. (fig. 14) (fig. H) (fig. 14) Pb Cn Zn Pb Cu Zn Pb Cn Zn 

-- --- 49 _____________ 59-16458 50 50 50 81_ ____________ 29388 25 20 50 113 ____________ 29198 25 30 50 50 _____________ 16468 <25 40 50 82 _____________ 29358 25 10 50 114 _______ _____ 29188 25 10 25 51 ___ ---------- 16478 <25 40 50 83 _____________ 29348 25 30 50 115 ____________ 29178 25 10 50 52 ___ ---------- 16488 25 40 50 84 _____________ 29338 25 10 25 116 ____________ 29168 25 10 50 53 _____________ 16528 <25 40 50 85 _____________ 29328 25 10 25 117 -----------~ 29158 25 20 50 54 _____________ 16578 <25 20 25 86 _____________ 29318 25 20 50 us__ __________ 29028 25 20 25 55 _____________ 16588 <25 20 25 87------------- 29408 25 10 25 119 ______ ______ 29438 25 10 25 56 _____________ 16728 <25 20 25 88 _____________ 29398 25 10 25 120 ____________ 59-16778 <25 20 25 57------------- 16738 25 40 25 89 ___ __________ 29448 25 20 25 121_ ___________ 16718 <25 20 25 58 _____________ 16748 <25 30 50 90 __ ----------- 29428 25 10 25 122 ____________ 16708 <25 20 50 59 _____________ 16758 <25 20 25 91 _____________ 29308 25 10 50 123 ____ ________ 16798 <25 10 25 60 _____________ 16768 <25 20 25 92 ______ ------- 29298 25 10 25 124 ____________ 16788 <25 20 50 til _____________ 16808 <25 20 25 93 ______ ------- 29288 25 10 25 125 ____________ 62 _____________ 61-29118 25 10 50 16818 <25 20 25 94 _____________ 29418 25 10 50 126 ____________ 63 _____________ 29128 25 10 75 60-29068 25 10 25 95 _____________ 64 _____________ 61-29168 25 40 75 127------------ 29148 25 30 100 29078 25 20 25 96 _____________ 60-29468 25 20 50 128-----~------ 29138 25 10 75 65 __ ----------- 29058 25 20 25 97------------- 29458 25 20 50 129 ____________ 66 _____________ 59-16698 <25 20 <25 59-16448 75 75 75 98 _____________ 29478 25 20 50 130 ____________ 16688 <25 20 25 67------------- 60-29138 25 20 50 99 _____________ 29148 25 10 25 131_ ___________ 16668 <25 30 68 _____________ 25 29128 25 30 25 100 ____________ 29268 25 10 25 132 ____________ 16678 <25 20 69 _____________ 25 29118 25 30 75 lOL __________ 29278 25 10 50 133 ____________ 16658 <25 30 70 _____________ 25 29108 25 20 25 102 ____________ 29258 25 10 25 134 ____ ________ 16648 <25 20 71 _____________ 25 29098 25 20 <25 103 _________ ___ 29248 25 10 50 135 ____________ 16638 <25 20 72 ___ __________ 25 29088 50 20 50 104__ __________ 61-29078 50 40 75 136 ____________ 16628 <25 20 73 _____________ 25 59-16498 25 75 50 105 ____________ 60-29238 25 10 25 137------------ 16618 <25 20 7 4 _____________ 25 16518 <25 40 50 106 ____________ 61-29088 50 40 75 138 __ ---------- 16568 <25 20 75 _____________ 25 16508 <25 40 25 107------------ 29098 50 30 75 139 ____________ 16608 <25 20 76 _____________ 16558 <25 30 50 108 ____________ 60-29228 25 10 50 140 I_--------- 16598 <25 20 25 

77------------- 16538 <25 40 25 109 ____________ 61-29108 50 30 75 14L ___________ 60-29038 25 10 <25 78 _____________ 16548 25 40 25 110 ____________ 29158 25 20 75 142 __ ---------- 29048 25 10 <25 79 _____________ 60-29378 50 10 50 11L __________ 60-29218 25 30 50 25 so _____________ 29368 25 20 50 112 ____________ 29208 25 20 50 

t Sample from terrace 18 inches above stream and sample from locality 61. 

TABLE 16.-Semiquantitative spectrographic analyses of alluvium 

Analyses, in percent, by E. F. Cooley. Elements looked for, but not found, in ppm: Ag <1,As <1000, Bi <10, Cd <50, Ga. <20, Ge <20, In <50, La <50, Nb <50, Sb <200 Sc <10, Zn <2001 

Sample loc. (fig. 14) ____ 49 50 51 52 53 54 Lab. No _______________ 59-1645 59-1646 59-1647 59-1648 59-1652 59-1657 

------------

SL_ -------------------- 20 10 20 30 15 30 Fe_-------------------- Mg _____________________ 2 2 3 2 2 1.5 2 2 2 1.5 2 .3 

Ti __ ------------------- .3 .15 .3 .3 .1 .15 

Mn ___ ----------------- .07 .1 .07 .07 .15 .02 

B ---------------------- .005 .005 .01 .01 .003 .002 Ba ____ ----------------- .05 .03 .07 .05 .05 .05 Be_-------------------- Co <.0001 .0001 .0001 <.0001 <.0001 <.0001 _____________________ <.001 <.001 .001 .001 .001 .001 

Cr --------------------- Cu .005 .003 .007 .005 .005 .005 _____________________ .003 .003 .003 .003 .002 .0007 

NL-------------------- Pb .0015 .0015 .002 .0015 .001 .0015 _____________________ .002 • 003 .002 .002 .0015 <.001 Sr _____ ---------------- .03 .05 .02 .01 .03 .005 

v ---------------------- • 005 .005 .01 .01 .005 .005 

y ---------------------- .003 .003 .005 • 002 . 002 .003 Zr ___ ------------------ .03 .007 .02 .02 .007 .015 

The areas that show minor anomalies in the content 

of copper, lead, and zinc correspond closely with 

known mineralized areas, as illustrated on figure 14. 

Very weak anomalies, having roughly two to three 

times the background value of a single metal, are near 

small mineralized areas, and somewhat more pronounced anomalies, involving several metals or greater 

values for one metal, are near two of the larger mineralized areas. Lead seems to be a more sensitive 

indicator of moderately intense mineralization than 

either copper or zinc. The extent and intensity of the 

anomalies in mineralized areas is not proportional to 

55 56 57 58 59-1658 59-1672 59-1673 59-1674 

---

20 20 10 10 1.5 1.5 3 2 1 1.5 2 2 .15 .1 .15 .15 .05 .07 .07 .07 .005 .002 . 003 .003 .05 .03 .03 .03 <.0001 <.0001 .0001 .0001 

<.001 <.001 .0015 .001 .003 .007 .007 • 002 .002 .0015 .005 • 005 .001 .0015 .003 .002 .002 .001 .005 .005 .02 .03 .07 .02 .005 .005 .01 .003 .003 .003 . 002 .002 .01 ,015 .005 .01 

59 60 59-1675 59-1676 

7 30 1 3 

2 1. 5 .1 • 3 .05 • 07 .001 • 007 .03 .05 <.0001 • 0001 <.001 • 001 .003 • 005 .002 .005 .001 .002 .002 • 003 .03 .02 • 003 .01 .002 .005 .005 .02 

61 59-1680 

10 

2 

1.5 

.2 

.07 

• 003 

.05 

.0001 

.001 

.007 

.003 

.002 

.002 

.05 

.007 

.002 

.01 

62 59-1681 

20 

3 

1 

,15 

.07 

:07 

<· 

003 

0001 1 

7 

2 

2 

<.00 

.oo 

.oo 

.00 

.o 02 • 05 

.o 

:o1 

05 

003 

the exrent and intensity of the known mineralization 

in those areas. The anomaly along lower Cleve Creek, 

for instance, is of the same order of magnitude as that 

near the Taylor district, . although there appears " to 

have been much less mineralization along Cleve Creek 

than in the Taylor district. Perhaps there are minalized rocks along Cleve Creek that have not yet been 

discovered, or possibly the quartzite terrane along 

Cleve Creek facilitates the retention of the· ~etals in 

forms readily found by the tests employed, whereas 

in the limestone-rich terrane of the Taylor district 

the metals are washed out or are not found by those 
ECONOMIC GEOLOGY 85 

114°~4~5~'---------~------------------------.-------.---------------------------1_1,4°30' 

.. /·· 1 

.·-·1 ....£-. . . . .!2§;:.. <..____ 31 • ·-.~

lOS. ·· 

-

SUCCESS MIN£ 

~ v 

/ 

\ / 

I? / : /; ,__. / I/ 

/ ... ~. 

/ 

·. 48 

. \ '\.~16 

) 

( 

-------·. 

\ 

/ 

---··. · .. 

/.·· 

3-.!E. 

--···> ... - ··effi --- .• 

J 

\ 133 .. . 

~-··-\ .. ~~ 

39° ........._ 00'~----------------~~----~----------L---·----------------~~----------~ 

0 3 MILES 

EXPLANATION 

D 

10-20 ppm Cu 

<25- 25 ppm Ph 

25 ppmZn 

30-40 ppm Cu 

and (or) 

50-100 ppm Zn 

50-75 ppm Cu 

and (or) 

50-75 ppm Ph 

.74 

Locality of chemically analyzed 

sample (field method, wet 

test) 

+29 

Locality of spectrographically 

analyzed sample 

_.f'0 

Locality of chemically and spectrographically analyzed sample 

Mine or prospect 

_FIGURE 14.-Distribution of lead, copper, and zinc in alluvium in the Connors Pass quadrangle. 
86 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

tests. This idea seems to be supported by the abrupt 

decrease of metal content in the washes that drain the 

western edge of the Taylor district, as opposed to 

gradual decrease of metal content in the washes to the 

east and south. When the same analytic methods are 

used and the same type of mineralization is being 

checked, the sampling interval in a limestone terrane 

ought not to be more than 1 mile, but in a. quartzite 

terrane may be slightly larger. 

Although strong prevailing winds frequently carry 

fumes from the copper smelter at McGill southward 

along the west front of the range for about 30 miles, 

the samples taken in the Taylor district do not record 

any base-metal anomalies attributable to contamination by these fumes. Within the Connors Pass quadrangle, a minimum of 15 miles from the smelter, the 

depth at which samples were collected apparently was 

adequate to safeguard against contamination by airborne particles. 

Semiquantitative spectrographic analyses were made 

of many alluvium samples taken in areas underlain by 

Pioche Shale to check specifically for beryllium, which 

occurs in the Pioche southeast across Spring Valley 

(Stager, 1960; Whitebread and Lee, 1961) . The contents of copper and lead measured by these analyses 

generally agreed with those measured by the wet tests 

(table 15). 

Semiquantitative spectrographic analyses of samples 

from the Pilot Shale and the Chainman Shale showed 

anomalously high contents of several elements ( numbers in italic type on table 5). One sample contained 

0.2 percent zinc, 0.1 percent each of chromium and 

vanadium, and smaller but significant amounts of copper, silver, and other elements. The high values of 

copper, silver, and zinc are of special interest because 

these metals have been economically important in the 

region. However, a further cursory study showed no 

obvious relations of high v&.lues of some metals in 

these shales to either areal or stratigraphic variations 

to distance from the large thrust fault or from a~ intrusive body, or to the mineralization in the Taylor 

district. No explanation has yet been found for the 

local concentration of some metals, but it may be revealed by more detailed study of the sedimentation 

a?-~ environment during, and shortly after, the deposition of the black shales. · 

GEOLOGIC HISTORY 

The following section gives the best interpretation . 

I am now able to make of the geologic history. The 

interpretation is necessarily incomplete, because a 

great part of what happened in the area since the 

end of Precambrian time has left no geologic record. 

Near the end of late Precambrian time, the sea 

covered the region and currents brought much sand 

and some mud into the area. Marine deposition continued into Cambrian time without interruption and 

without change in the type of sediments. 

During Paleozoic time, the sea floor seems never to 

have been deeply submerged, but it subsided almost 

continuously, though not at a uniform rate, to receive 

sediments aggregating about 5 miles in thickness. 

The tectonic conditions during this era changed markedly twice, these changes causing both local and regional changes in the character of the sediments and 

in the rate of sedimentation. On the basis of these 

changes, the Paleozoic Era can be divided into three 

parts, each of which lasted about 120 million years. 

During early Paleozoic time, about 12,000 feet of 

sediment was deposited at a fairly uniform rate of 

about 100 feet per million years. In Early Cambrian 

and part of Middle Cambrian time, sand and mud 

similar to those deposited in late Precambrian time 

continued to be brought into the area from the east, 

but later in the Cambrian Period the shoreline moved 

progressively eastward and carbonate sediments were 

deposited. Early in the Late Cambrian, during Lincoln Peak time, deposition of carbonates alternated 

with deposition of mud that came from the west; thmt 

the sea regressed ·and the source of the clastics shifted 

back to the east. Toward the end of Cambri'an time 

and in much of Early Ordovician time, less clastic 

material was brought into the area; thereafter it increased sporadically and carbonate sand, flakes and 

chips of limy mudstone, and bioclastic material were 

reworked. The sea was evidently shallow at this time, 

and it seems to have become increasingly shallow in 

the interval preceding the major change in the seaway 

system that followed. 

The sea floor subsided much more slowly in middle 

Paleozoic time, and less than 4,000 feet of sediments 

accumulated at an average rate of 40-60 feet per million years. This phase began during Middle Ordovician time with the deposition of the well-sorted and 

well-rounded clean quartz sand that formed the Eureka Quartzite. The sand was deposited from a 

magnesium-charged sea. During much of middle 

Paleozoic time, the calcium carbonate that was precipitated was diagenetically altered to dolomite. In Late 

Ordovician time, much organic material was included 

with the sediments that formed the Fish Haven Dolomite. Perhaps in Early Silurian time, and certainly in Late Silurian, the area was nearly at sea 

level. Some of it may occasionally have risen briefly 

above sea level, but probably did not undergo much 
GEOLOGIC EITSTORY 87 

erosion. In Early Devonian time, immediately after 

the second emergence, the sea appears to have contained so much magnesium that primary dolomite 

was deposited to form the Sevy Dolomite. Late in 

Sevy tim_e more clean quartz sand came into the. area. 

Throughout Simonson time and the early part of 

Guilmette time, magnesium carbonate from sea water 

may have diagenetically changed the limy deposits to 

dolomite; however the supply of magnesium diminished gradually toward the end of Middle Devonian 

time, so the sediments of the Guilmette Formation 

are not completely dolomitized and show many replacement textures. Clean quartz sand was deposited 

in the area during middle Guilmette time, perhaps 

from a relatively distant source, for the last time; 

subsequently the clastic material was derived more 

locally as a result of the changing tectonic conditions 

that distingiushed late from middle Paleozoic time. 

The sea floor again subsided more rapidly in late 

Paleozoic time and the area received abundant sediments at about half the regional average rate ·of 

about 200 feet per million years, this ·rate indicating 

that the Connors Pass area lay in a. relatively stable 

part of a sea that was at least partly surrounded by 

tectonically active areas. In early Late Devonian 

time and only shortly after the deposition of the lad 

clean sand, .dirty poorly sorted and poorly rounded 

sand was intercalated with the calcareous deposits to 

record the earliest movements of the tectonically active areas (an area 100-150 miles to the northeast). 

Quieter conditions returned briefly and, at the end of 

Guilmette time, reef structures formed. Near the 

~nd of Devonian time the area seems to have been 

briefly uplifted, and the upper few hundred feet of 

the Guilmette Formation was largely removed by 

erosion before the Pilot Shaie was deposited. The 

sea returned at the end of Devonian time and remained 

into Early Mississippian time, when the area was 

covered with the dirty silt and mud of the Pilot Shale, 

these deposits reflecting further tectonic activity 

nearby (to the north west) . During Joana time, calcium carbonate was again deposite~ and minor reef 

structures were formed in a shallow sea. During Late 

Mississippian time, however, clastics that formed the 

Chainman Shale were deposited in the area. Son1e 

patches of the black mud accumulated anomalously 

large amounts of chromium, vanadium, copper, silver, 

and zinc. Toward the end of Chainman time some 

sand and conglomerate were deposited in channels on 

mud that formed the Chainman; the area may have 

been a .tidal flat or the floor of a lagoon. During 

Early Pennsylvanian time, a deeper sea returned to 

the area, and limy mud and small -reefs of the Ely 

Limestone were deposited. Late in Pennsylvanian 

time, however, the area was once more uplifted, sufficiently at least for sediments from other areas to 

bypass it, and possibly sufficiently for sediments to 

be removed from it, and all were deposited in the 

rapidly subsiding Oquirrh Basin 60 miles to the 

northeast. Shortly after the beginning of the Permian, abundant dirty sand and silt were again 

brought in from the northwest to form the Rib Hill 

Sandstone; the influx of these sediments diminished 

somewhat in Arcturus time, when small reef structures formed. Late in this period, probably in Leonard time, some gypsum . was deposited here. 

Mesozoic sedimentary rocks are largely absent in 

the Connors Pass area because of orogeny that probably began in Late Jurassic time. In nearby areas 

about 5,000 feeet of sediments we deposited during 

Triassic and Early Jurassic time, largely in a marin.e 

environment. Near the end of the Triassic Period, 

the sea left the region for the last time, and at least 

the youngest of the deposits, correlative with the 

Navajo Sandstone of the Colorado Plateau region to 

the east, was deposited in a terrestrial environment .. 

During Late Jurassic time, the base of the Cambrian rock lay at depths as great as 7 miles, and because of the great weight of the overlying column, 

the Precambrian rock and some of the Cambrian rock 

were mildly metamorphosed to very low grade argillite, phyllite, slate, and marble. During Late Jurassic 

or Early Cretaceous time, the rock in the area was 

warped into widely scattered broad domes, and the 

Paleozoic rock was thrust northeastward for an unknown distance along multiple fault planes that lay 

subparallel to bedding. Subsidiary tear faults and 

normal faults were formed within the plates, and 

rock is generally missing rather than repeated along 

the faults that are almost parallel to the bedding. In 

some places the rocks along the thrust faults were 

dynamically metamorphosed. . The greatest movem~nt 

was concentrated along the Schell Creek Range thrust 

fault lying near the middle of the group of multiple 

low-angle faults. Some of the faults above the Schell 

Creek Range thrust fault may be glide faults, and 

they may even be glide faults along older thrust fault 

surfaces. By Late Cretaceous 'or early Paleocene time, 

the area had already been strongly unlifted: and deeply 

eroded and at least one basin had been formed in ' . which clastic rocks accumulated. Some volcanism is 

also recorded by the volcanic ash inte;rcalated with the 

sediments, 
88 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

Epeirogenic and possibly also orogenic movements 

continued during Tertiary time, when the rocks were 

broken by normal faults and were again deeply eroded. 

It was probably during the Tertiary that the granophyric dikes were intruded and that siliceous fluids 

rose along the existing faults. In the Taylor district 

these solutions selectively replaced parts of the Guilmette Formation and the Joana Limestone with silica 

and ores of silver, antimony, and other base metals. 

During Eocene time, the area lay along the western 

flank of a mountainous region and became partly covered with piedmont gravel. Volcanism became widespread during the Eocene and Oligocene ( ~) Epochs 

and was closely associated with later normal faulting. 

Basaltic andesite was the first intrusion, followed 

successively by the extrusion of a latite lava, eruption of abundant latite tuft' (partly welded) and several extrusions of dacite lava interlayered with some 

dacite tuft'. 

Further movement along normal faults during middle or late Tertiary time caused north-trending grabens and block-faulted ranges that resemble the present ones in the region but that do not coincide with 

the present Schell Creek Range. Two large glide 

plates of Tertiary rock moved westward from a raised 

block into a valley cut in the Chainman Shale; the 

larger moved about 3,500 feet. While they were gliding, the plates were gently warped into open eastwardplunging synclines. 

During late Tertiary and Quaternary time, volcanism ceased, but normal faulting and accumulation of 

piedmont gravel and basin deposits continued. Several faults cut the glide plates of middle or late Tertiary age and locally lie along older normal-fault 

surfaces. Probably in Pliocene time, gravel was deposited at the foot of some of the larger fault-block 

mountains and was itself faulted. The Schell Creek 

Range was probably formed in about its present position early in Quaternary time, and pediment and 

fan gravels were deposited along both of its flanks. 

Owing to the climatic changes during Pleistocene 

time and to renewed movement along normal faults 

extending along some of the mountain fronts, the 

older of these gravels was incised and then the 

younger and successively finer grained gravel was deposited. During late Pleistocene time, at least, pluvial Spring Valley Lake overlapped the eastern edge 

of the area. During the desiccation of the lake, bars 

were formed at progressively lower elevations, small 

dunes accumulated behind them, and they became 

I>artly covered by younger gravel. 

REFERENCES CITED 

Adair, D. H., and Stringham, B. F., 1960, Intrusive igneous 

rocks of east central Nevada, in Geology of east central 

Nevada : Intermountain Assoc. Petroleum Geologists, 11th 

Ann. Field Conf., 1960 Guidebook, p. 229-231. 

Armstrong, R. L., 1963, Geochronology and geology of the eastern Great Basin in Nevada and Utah: Yale Univ. Ph. D. 

thesis. 

Bick, K. F., 1958, Geology of the Deep Creek quadrangle, western 

Utah: Yale Univ. Ph. D. thesis. 

-- 1959, Stratigraphy of Deep Creek Mountains, Utah : 

Am. Assoc. Petroleum Geologists Bull., v. 43, no. 5, p. 1064-

1009. 

Clark, D. L., and Becker, J. H ., 1960, Upper Devonian correlations in western Utah and eastern Nevada: Geol. Soc. 

America Bull., v. 71, no. 11, p. 1661-1674._ 

Clark, W. 0., and Riddell, C. W., 1920, Exploratory drilling for 

water and use of ground water for irrigation in Steptoe 

Valley, Nevada: U.S. Geol. Survey Water-Supply Paper 

467,70 p. 

Cohenour, R. E., 1957, Geology of the Sheeprock Mountains, 

Tooele and Juab Counties, Utah: Utah Univ. Ph. D. thesis. 

-- 1959, Sheeprock Mountains, Tooele and Juab Counties: 

Utah Geol. and Mineralog. Survey Bull. 63, 201 p. 

Cook, E. F., 1960, Great Basin ignimbrites, in Geology of east 

central Nevada: Intermountain Assoc. Petroleum Geologists, 11th Ann. Field Conf., 1960 Guidebook, p. 134-141. 

Couch, B. F., and Carpenter, J. A., 1943, Nevada's metal and 

mineral production (1859-1940 inclusive) : Nevada Univ. 

Bull. 37, no. 4, Geol. and Mining Ser. 38, 159 p. 

Dapples, E. C., 1962, Stages of diagenesis in the development of 

sandstones: Geol. Soc. America Bull., v. 73, no. 8, p. 913-933. 

DeSitter, L. U., 1956, Structural geology, 1st ed.: New York, 

McGraw-Hill Book Co., Inc., 552 p. 

Dott, R. H., Jr., 1955, Pennsylvanian stratigraphy of Elko and 

northern Diamond Ranges, northeastern Nevada : Am. 

Assoc. Petroleum Geologists Bull., v. 39, no. 11, p. 2211-2305. 

Douglass, W. B., Jr., 1960, Geology of the southern Butte Mountains, White Pine County, Nevada, in Geology of east central Nevada: Intermountain Assoc. Petroleum Geologists, 

11th Ann. Field Conf., 1960 Guidebook, p. 181-185. 

Drewes, Harald, 1954, Structural geology of the southern Snake 

Range, Nevada: Yale Univ. Ph. D. thesis. 

-- 1958, Structural geology of the southern Snake Range, 

Nevada: Geol. Soc. America Bull., v. 69, no. 2, p. 221-239. 

-- 1959, Turtleback faults of Death Valley, California.....--a 

reinterpretation : Geol. Soc. America Bull., v. 70, no. 12, 

pt. 1, p. 1497-1508. 

-- 1960a, Bedding~plane thrust faults east of Oonnors Pass, 

Schell Creek Range, eastern Nevada, in Short papers in th~ 

geological sciences: U.S. Geol. Survey Prof. Paper 400-B, 

p. B27Q-B272. 

-- 1960b, Major structural features of the central parts of 

western Utah and eastern Nevada [abs.]: Geol. Soc. America Bull., v. 71, no. 12, pt. 2, p. 1853-1854. 

-- 1962, Stratigraphic and structural controls of mineralization in the Taylor mining district near Ely, Nevada, in 

Short papers in geology, hydrology, and topography: U.S. 

Geol. Survey Prof. Paper 450-B, p. B1-B3. 

Drewes, Harald, and Palmer, A. R., 1957, Cambrian rocks of 

southern Snake Range, Nevada: Am. Assoc. Petroleum 

Geologists Bull., v. 41, no. 1, p. 104-120. 
REFERENCES CITED 89 

Fritz, W. H., 1960, Strueture and stratigraphy of the northern 

Egan Range, White Pine County, Nevada: Seattle, Washington Univ. Ph. D. thesis. 

Goddard, E. N., chm., and others, 1948, Rock-Color Chart : 

Washington, D.C., Natl. Research Council (repub. by Geol. 

Soc. America, 1951), 6 p. 

Hague, Arnold, 1883, Abstract of report on the geology of the 

Eureka district, Nevada: U.S. Geol. Survey 3d Ann. Rept., 

p. 237-290. 

--- 1892, Geology of the Eureka district, Nevada: U.S. Geol. 

Survey Mon. 20, 419 p. 

Harlow, G. R., 1956, Stratigraphy and structure of the Spruce 

Mountain area, Elko County, Nevada: Seattle, Washington 

Univ. M.S. thesis. 

Hill, J. M., 1916, Notes on some mining districts in eastern 

Nevada: U.S. Geol. Survey Bull. 648, 214 p. 

Hintze, L. F., 1951a, Lower Ordovician detailed stratigraphic 

sections for western Utah: Utah Geol. and Mineralog. Survey Bull. 39, 100 p. 

--- 195lb, Ordovician stratigraphy of central Utah, in Utah 

Geol. Soc. Guidebook 6 : p. 38--43. 

--- 1952, Lower Ordovician trilobites from western Utah 

and eastern Nevada: Utah Geol. and Mineralog. Survey 

Bull. 48, 249 p. 

Hose, R. K., and Repenning, C. A., 1959, Stratigraphy of Pennsylvanian, Permian, and Lower Triassic rocks of Confusion 

Range, west-central Utah : Am. Assoc. Petroleum Geologists 

Bull., v. 43, no. 9, p. 2167-2196. 

Howell, E. E., 1875, The geology of portions of Utah, Nevada, 

Arizona, and New Mexico, in U.S. Geog. and Geol. explorations and surveys west of the lOOth meridian, v. 3, pt. 3 : 

p. 227-301. 

Hubbert, M. K., and Rubey, W. W., 1959, Mechanics of fluid-filled 

porous solids and its application to overthrust faulting, 

pt. 1 ot Role of fluid pressure in mechanics of overthrust 

faulting: Geol. Soc. America Bull., v. 70, no. 2, p. 115-166. 

Humphrey, F. L., 1960, Geology of the White Pine mining district, White Pine County, Nevada: Nevada Bur. Mines 

Bull. 57, 119 p. 

Kellogg, H. E., 1960, Geology of the southern Egan Range, 

Nevada, in Geology of east central Nevada: Intermountain 

Assoc. Petroleum Geologists, 11th Ann. Field Conf., 1960 

Guidebook, p. 189-197. 

Kirk, Edwin, 1933, The Eureka quartzite of the Great Basin 

region: Am. Jour. Sci., 5th ser., v. 26, no. 151, p. 27-44. 

Langenheim, R. L., Jr., 1960, Early and Middle Mississippian 

stratigraphy of the Ely area, in Geology of east central 

Nevada: Intermountain Assoc. Petroleum Geologists, 11th 

Ann. Field Conf., 1960 Guidebook, p. 72-80. 

Lawson, A. C., 1906, The copper deposits of the Robinson mining 

district, Nevada: California Univ. Dept. Geol. Bull. 4, 

p. 287-357. 

Mackin, J. H., 1960, Structural significance of Tertiary volcanic 

rocks in southwestern Utah: Am. Jour. Sci., v. 258, no. 2, 

p. 81-131. 

McJannet, George, 1960, Geologic map, east central Nevada, in 

Geology of east central Nevada: Intermountain Assoc. 

Petroleum Geologists, 11th Ann. Field Conf., 1960 Guidebook. 

Merriam, C. W., 1940, Devonian stratigraphy and paleontology 

of the Roberts Mountain region, Nevada: Geol. Soc. America Spec. Paper 25, 114 p. 

Misch, Peter, 1960, Regional structural reconnaissance in centralnortheast Nevada and some adjacent areas: observations 

and interpretations, in Geology of east central Nevada: 

Intermountain Assoc. Petroleum Geologists, 11th Ann. Field 

Conf., 1960 Guidebook, p. 17-42. 

Misch, Peter, and Easton, W. H., 1954, Large overthrusts near 

Connors Pass in the southern Schell Creek Range, White 

Pine County, eastern Nevada [abs.]: Geol. Soc. America 

Bull., v. 65, no. 12, pt. 2, p. 1347. 

Misch, Peter, and Hazzard, J. C., 1962, Stratigraphy .and metamorphism of Late Precambrian rocks in central northeastern Nevada and adjacent Utah: Am. Assoc. Petroleum 

Geologists Bull., v. 46, no. 3, pt. 1, p. 289-343. 

Morris, H. T., 1957, General geology of the East Tintic Mountains, Utah, in Utah Geol. Soc. Guidebook 12: p. 1-56. 

Morris, H. T., and Lovering, T. S., 1961, Stratigraphy of the 

East Tintic Mountains, Utah: U.S. Geol. Survey Prof. Paper 

361,145 p. 

Nelson, R. B., 1959, The stratigraphy and structure of the 

northernmost part of the northern Snake Range and the 

Kern Mountains in eastern Nevada and the southern Deep 

Creek Range in western Utah: Seattle, Washington Univ. 

Ph. D. thesis. 

Nolan, T. B., 1935, The Gold Hill mining district, Utah: U.S. 

Geol. Survey Prof. Paper 177,172 p. 

Nolan, T. B., Merriam, C. W., and Williams, J. S., 1956, The 

stratigraphic section in the vicinity of Eureka, Nevada: 

U.S. Geol. Survey Prof. Paper 276, 77 p. 

Olson, R. H., 1956, Geology of Promontory Range, in Utah Geol. 

Soc. Guidebook 11: p. 41-75. 

Osmond, J. C., Jr., 1954, Dolomites in Silurian and Devonian of 

east-central Nevada: Am. Assoc. Petroleum Geologists Bull., 

v.38,no.9,p.1911-1956. 

Palmer, A. R., 1960, Some aspects of the early Upper Cambrian 

stratigraphy of White Pine County, Nevada and vicinity, 

in Geology of east central Nevada: Intermountain A<Ssoc. 

Petroleum Geologists, 11th Ann. Field Conf., 1960 Guidebook, p. 53-58. 

--- 1965, T1·ilobites of the Late Cambrian Pterocephaliid 

biomere in the Great Basin, United States: U.S. Geol. Survey Prof. Paper 493, 105 p. 

Pennebaker, El N., 1932, Geology of the Robinson (Ely) mining 

district in Nevada; a preliminary report on the primary 

monzonite porphyry intrusive ore bodies and how they are 

formed: Mining and Metallurgy, v. 13, no. 304, p. 163-168. 

Poole, F. G., Houser, F. N., and Orkild, P. P., 1961, Eleana formation of Nevada Test Site and vicinity, Nye County, 

Nevada, in Short papers in the geologic and hydrologic 

sciences: U.S. Geol. Survey Prof. Paper 424-D, p. D104-

Dlll. 

Reso, Anthony, 1962, Paleozoic stratigraphy in the Pahranagat 

Range, Lincoln County, Nevada [abs.]: Geol. Soc. America 

Spec. Paper 68, p. 251-252. 

Richardson, G. B., 1913, The Paleozoic section in northern Utah: 

Am. Jour. Sci., 4th ser., v. 36, p. 406--416. 

Roberts, R. J., 1942, Manganese deposits in the Nevada district, 

White Pine County, Nevada: U.S. Geol. Survey Bull. 931-M, 

p. 295-318. 

Ross, R. J., Jr., 1951, Stratigraphy of the Garden City formati?n 

in northeastern Utah, and its trilobite faunas: Yale Umv. 

Peabody Mus. Nat. History Bull. 6, 161 p. . 

--- 1964, Relations of Middle Ordovician time and rock umts 

in Basin ranges, western United States: Am. Assoc. Petroleum Geologists Bull, v. 48, no. 9, p. 1526-1554. 
90 GEOLOGY, CONNORS PASS QUADRANGLE, NEVADA 

Schaeffer, F .. E., Jr., and Anderson, W. L., 1959,. Geologic ·history 

of the Silv~r Island Range, Utah and Nevada [abs.]: Geol. 

Soc. America Bull., v. 70, no. 12, pt . 2, p. 17.86--1787. 

- . -- 1960, GeQlogy of the Silver Island Mountains, Box Elder 

· and Tooele Counties, Utah, and Elko County, Nevada, in 

Utah Geol. Soc~ Guidebook 15: 185 p. 

Sharp, R. P., 1942, Stratigraphy and structure of the southern 

_ Ruby Mountains, Nevada: Geol. Soc. America Bull., v. 53, 

no. 5, p. 647-690. 

Shawe, D. R., 1961, Rhyolites in the Egan Range south of Ely, 

Nevada, in Short papers in the geologic and hydrologic 

sciences: U.S. Geol. Survey Prof. Paper 424-B, p. B178-

B181. 

Snelson, Sigmund, 1955, Geology of the southern Pequop Mountains in Elko County, northeastern Nevada: Seattle, Washington Univ. M.S. thesis. 

Spencer, A. C., 1917, The geology and ore deposits of Ely, Nevada: 

U.S. Geol. Survey Prof. Paper 96, 189 p. 

Spurr, J. E., 1903, Descriptive geology of Nevada south of the 

40th parallel and adjacent portions of California: U.S. 

Geol. Survey Bull. 208, 229 p. 

Stager, H. K., 1960, A new beryllium deposit at the Mount 

Wheeler mine, White Pine County, Nevada, in Short papers 

in the geological sciences: U.S. Geol. Survey Prof. Paper 

400-:-B, p. B70-B71. , 

Steele, Grant, 1960, Pennsylvanian-Permian stratigraphy of eastcentral Nevad.a and adjacent Utah, in Geology of east central Nevada: Intermountain Assoc. Petroleum Geologists, 

11th Ann. Field Conf., 1960 Guidebook, p. 91-113.' 

Stokes, W. L., and · Arnold, D. E., 1958, Northern Stansbury 

Range and the Stan-sbury formation, in Utah Geol. Soc. 

Guidebook 13; p. 135-149. 

Troger, W. E., 1956, Optische Bestimmung der gesteinsbildenden 

Minerale ; pt. 1, Bestimmungstabellen : Stuttgart, E. 

Schweitzerbart'sche, 147 p. 

Tschanz, C. M., and Pampeyan, E. H., 1961, Preliminary geologic 

map of Lincoln County, Nevada: U.S. Geol. Survey Mineral 

Inv. Field Studies Map MF-206. 

U.S. Bureau of Mines, 1937-61, Minerals yearbooks, 1937-60. 

u.s. Weather: Bureau, 1957, Climatography of the United States, 

Nos . .11-:-22, in Climatic summary of the United Statessupplement for 1931-52. 

Van Bouten, F. B., 1956, Reconnaissance of Cenozoic sedimen~ 

tary rocks· of Nevada: Am. Assoc; Petrol~um Geologists 

Bull., v. 40, no.12, p. 2801-2825. 

Walcott, C. D.; 1008, Cambrian sections of the Cordilleran area: 

Smithsonian Misc. Colin. 53, Pub. 1812, p. 166--230. 

Webb, G. W., 1956, Middle Ordovician detailed stratigraphic 

sections for western Utah and eastern Nevada: Utah Geol. 

and Mineralog. Survey Bull. 57, 77 p. 

Westgate, L. G., and Knopf, Adolph, 1932, Geology and .ore deposits of the Pioche district, Nevada, with contributions by 

J. L. Gillson : U.S. Geol. Survey Prof. Paper 171, 79 p. 

Whitebread, D.- H., and Lee, D. E., 1961, Geology of the Mount 

Wheeler mine area, White Pine County, Nevada,. in Short 

papers in the geologic and hydrologic sciences: U.S. Geol. 

Survey Prof. Paper 424-C, p. C120-C122. 

Whitehill, H. R., 1873, Biennial report of the State mineralogist 

of the State of Nevada for the years 1871 and 1872: 191 p. 

[Carson City]. 

Winfrey, W. M., Jr., 1960, Stratigraphy, correlation, and oil 

potential of the Sheep Pass Formation, east-central Nevada, 

in Geology of east central Nevada: Intermountain Assoc. 

Petroleum Geologists, 11th Ann. Field Conf., 1960 Guidebook; 

p.126-133. 

Woodward, L. A., 1962, Structure and · stratigraphy of .the central Egan Range, White Pine County, Nevada: Seattle, 

Washington Univ. Ph. D. thesis. 

Young, J. C., 1960a, Structure and stratigraphy in the northcentral Schell Creek Range, eastern Nevada: Princeton 

Univ. Ph. D. thesis. 

--- 1960b, Structure and stratigraphy in north central Schell 

Creek Range, in Geology of east central Nevada : Intermountain Assoc. Petroleum Geologists, 11th Ann. Field 

Conf., 1960 Guidebook, p. 158-172. 

Youngquist, W. L., 1949, The cephalopod fauna of the White 

Pine shale of Nevada: Jour. Paleontology, v. 23, no. 3, 

p. 276--305. 
A 

Page 

acicaadus, J>seudoolenoides ___ -.---------------- 19 

Acinophyllum SP------------------------------ 32,33 

Acknowledgments____________________________ 2 

Albertella sp__________________________________ 12 

Allorisma sp__________________________________ 41 

Alluvial sand_________________________________ 64 

Alokistocare ___ _______ ------------- _ ·---·------- 11 sp_ _ __ __ _ _ __ _ _ _ _ _ ___ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 12 

altumbona, Thomasaria________________________ 32 

Alveolites sp ____ --------------------- _________ 32, 33 

Ameura SP------------------------------------ 46,47 

Amphiscapha sp______________________________ 50 

Amplexizaphrentis sp ______________ ·- ______ 41, 46,47 

Amplexoid____________________ ____ __ __ ________ 41 

Analyses, alluvium___________________________ 84 

dacite vitrophyre _________________________ 60, 61 

Pilot Shale___ ____________________________ 34 

porphyritic rhyolite ___ ------------------- 52 

rocks from Egan Range________ ___________ 57 

rocks from Schell Creek Range___________ 57 

rocks from Taylor mining district________ 78 

Anomalorthis utahensis________________________ 19 

sp_ _ _ _ _ _ _ _ _ ___ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ 19 

Antimony-------------------------- __________ 77, 82 

Antiquatonia coloradoensis _____________________ 44,45 

hermosana _________ ----------------------- 44, 45 

sp_ --------------------------------------- 44,45 

Archimedes SP------------------------------ 41, 46,47 

Arcturus Formation ________ 48, 53, 54, 62, 67, 70, 83,87 

arcturusensis, Tabulipora __ ------------------- 50 

argentarius, Spirifer --------------------------- 32,33 

arkansana, Flexaria ________________________ 40, 44,45 

Astartella sp_ ------------------------------ 41, 46, 47 Atrypa __________________ _____________________ 27, 28 

sp- ----------------------- ________________ 30, 31 

Atrype devoniana ______________________________ 30,31 

Aulopora sp_ --------------------------------- 32, 33 Auloporid coraL ________________ c _____________ 32,33 

Aviculopecten SPP----------------------------- 41 

Axelrod, D. I., fossil identification____________ 53 

Azurite______________________________________ 78 

B Barite ________________________________________ 77, 78 

BasaUic andesite vitrophyre_______________ _____ 59 

Basin and Range province__________ __________ 64 

Bathyurus sp_ -------------------------------- 19 

Beecheria sp _ --------------------------------- 44, 45 

BeUerophon sp ____________ --------------- _ ____ 50 

Benches______________________________________ 63 

Beryllium ____________________________________ 77,86 

binodosum, Glabrocingulum____________________ 41 

bisculcatum, Eumorphoceras___________________ 40 

bivia, Leperditia_____________________________ __ 19 

Bonnia_ -------------------------------------- 10 Bornite____________________________________ 82 

brachiopod, Orthoid ____________ ----------- _ ____ 19 

Bradyina sp _ ----------------- ____________ ____ 50 

bransoni, Calvinaria ___________________________ 30,31 

Breviphyllum sp __ ---------------------------- 32,33 

c 

Calliprotonia SP------------------------------- 44, 4fi 

Calvinaria brqnsonL -------------------------- 30,31 

sp_ --------------------------------------- 30,31 

INDEX 

[Italic page numbers indicate major references] 

Camarotoechia sp __ ---------------------------

Cambrian and Ordovician Systems __________ _ 

Cambrian rocks, metamorphism __ ----------- Cambrian System ___________________________ _ 

Page 

36 

16 

14 

7 

campestris, Reticulariina ___________________ 40, 44,45 

Caninia trojana _______________________________ 46,47 

carboniferum, Kozlowskia Leiorhynchus________ 40 

carboniferum polypleurum, Kozlowskia________ 40 

Carbon Ridge Formation____________________ 48 

carya, Nudirostra_____________________________ 30 

Catenipora sp _________________________________ 21,22 

catenularia, Halysites __ ----------------------- 23 

celsaora, HintzeL _ ---------------------------- 19 

centronatus, Spirifer ___ ----------------------- 36 

Cercidiphyllum ellipticum_____________________ 53 

Chaetetes ___ ---------------------------- 42, 43, 69, 70 

sp_ -----------------------~--------------- 46,47 

Chainman Shale______________________________ 27, 

97, 54, 67, 68, 69, 70, 71, 72, 73, 74, 78, 83, 87 

chesterensis, Petrocrania_______________________ 40 

Chonetes______________________________________ 36 

SP------------------------------------- 40, 44,45 Chonophyllum sp. infundibulum _______________ 32,33 

Chromium ___ -------------------------------- 86 

Chrysocolla __ -------------------------------- 78 

Cladopora __ ---------------------------------- 28 sp ________________________________________ 32, 33 

Clathrodictyon sp ___ -------------------------- 23 

Cleiothyridina orbicularis_--------------------- 44,45 

fUblamellosa __ ------------------------- 40, 44,45 suborbicularis_ ___ _ __ _ ___ ____ __ _ _____ __ _ __ _ 40 

sp_ --------------------------------------- 44,45 cleora, Simphysurina__________________________ 19 

Cleve Creek district__________________________ 82 

Climacammina sp _______________________ 46, 47, 48,50 

Climate __ ------------------------------______ 4 

cloudi utahense, Neoglyphioceras_______________ 40 

Coleolus sp __ ------------------------------- __ 41 

coloradoensis, Antiquatonia ____________________ 44,45 

Composita ozarkana ___________________________ 44,45 

subquadrata __________________ ____ ______ 40, 44,45 

subtilita ______________________ __ -------- 44, 45, 50 

sp_ --------------------------------- 36, 40, 44,45 

Condrathyris SP------------------------------- 44,45 

Conglomerate, Tertiary ___ ------------------- 59 

Conglomerate member, Arcturus Formation__ 49 

Cooley, E. F., analyst________________________ 81 

Copper------------------------------ 77, 82, 83, 84,86 

coral, Auloporid _____ -------------------------- 32 

Crassiftmbra ______ ____ ------- ____ _ ___ __ _ __ ___ _ 10 

Cravenoceras hesperium __ --------------------- 40 

merriamL ___ --------------------------- __ 40 

crebriliratum, Mitorthoceras ____ --------------- 40 

Cretaceous System ___________________________ 51,53 

croneisi, Reticycloceras_________________________ 40 

Crurithyris SP-----------"------------ 30, 31, 44, 45,48 

Cryptonella sp _________ -------------------- 23, 30,31 

Cybelopsis sp __ ------------------------------- 19 

Cypricardella SPP--------------"--------------- 41 Cyrtina sp ____________________________________ 30,31 

Cyrtospirifer placitus __________________________ 30,31 

Cystodictya sp _________________________________ 46,47 

D 

Dacite vitorphyre, description________________ 59 

environment, age, and correlation_________ 62 

Page 

decipiens, Mesolobus mesolobus _________________ 44,45 

Decollement fault ___ -----------"------------- 68 

Derbyia robusta ___ ---------------------------- 44, 45 

SP---------------------------------------- 44,45 

DeSitter, L. U., quoted_______________________ 76 

Desmoinesia muricatina ________________________ 44,45 

Devonian System ____________________________ 22,29 

devoniana, Atrype _____________________________ 30,31 

Devonoproductus vulgaris_. _____________________ 30,31 

sp_ --------------------------------------- 30,31 

Diabase, Prospect Mountain Quartzite________ 8 

Diaphragm us sp. A ___ ------------------------ 40 

sp. B--------------------------~---------- 44,45 

dilectus, Pseudoolenoides_______________________ 19 

dilitata, Lithostrotionella ____________________ 46, 47,50 

Dimegelasma SP------------------------------- 36 Dinoproductid _____ ________________________ ---- 40 

Diparelasma sp_ - ----------------------------- 19 

Dolorthoceras SP------------------------------- 40 

Domes, generaL______________________________ 64 

genetic relation to faults_----------------- 76 

Doryagnostus ___ ------------------------------ 14 

Douglass, R. C., fossil identification __________ 48,50 

Douvillina sp ___ ------------------------------ 30,31 

Duck Creek graben_____________________ ______ 70 

dunbari, Neospirifer --------------------------- 44,45 

Duncan, Helen, fossil identification_ 36, 40, 41, 44, 50 

Dutro, J. T., Jr., fossil identification _______ 30, 36,50 

quoted _________ -------------------------- 28 

E 

Echinoconchus sp __ --------------------------- 44,45 

eclectea, Warrenella____________________________ 32 

Economic geology __ -------------------------- 77 

Eleutherocentrus petersoni___________________ __ 19 

Eleutherokomma sp __ ---------------------~--- 30,31 

ellipticum, Cercidiphyllum_____________________ 53 

Ely Limestone_ 22, 41, 53, 62, 67, 69, 70, 71, 72, 74, 75, 83 

Elytha sp_c ___________________________ . ________ 30,31 

Eojletcheris sp_ ------------------------------- 19 

Eotomaria sp __ ------------------------------- 19 

Euloxoceras sp________________________________ 40 

Eumetria verneuiliana_________________________ 36 

sp ______________________________________ -_ 36 

Eumorphoceras bisulcatum. _ ------------------ 40 

(Euomphalus) sp. Straparollus________________ 36 

Euphemites SP-------------------------------- 50 Eureka Quartzite ____________________ 18, 54, 63, 67,86 

Eurekta SP------------------------------------ 18 

F 

Fanglomerate_------------------------------- 62 

fastfgata, Sequoia ____ ~------------------------- 53 

Faults _________________ --_--- ___ ------ ____ - _-- 6 

Favosites SP----------------------------------- 22 

Fenestella SP---------------------------------- 46, 47 

Ferestromatopora SP--------------------------- ·· 23 

Fish Haven Dolomite.-------------------- 20, 22,67 

Flexaria arkansana _________________________ 40, 44,45 

sp _____________________________________ 40, 44,45 

Fluorite __ ------------------------------------ 77, 83 Fossils, Arcturus Formation __________________ 48,49 

Cambrian and Ordovician limestone_____ 18 

Chainman Shale __ ----------------------- 39 

Ely Limestone_-------------------------- 42 

Fish Haven Dolomite____________________ 21 

91 
92 

Page 

Fossils, Arcturus Formation-Continued 

Guilmette Formation ____________________ n, 28 

Joana Limestone_________________________ 36 

Laketown Dolomite______________________ 22 

Lincoln Peak Formation_________________ 13 

Pioche Shale __ --------------------------- 9 

Pole Canyon Limestone__________________ 11 

Rib Hill Sandstone_--------------------- 48 

Sevy Dolomite __ ------------------------- 23 

Simonson Dolomite______________________ 25 

ftatateeta, Kleopatrina ______________________ 46, 47,50 

G 

Garrett Ranch Group________________________ 56 

Geochemistry_------------------------------- 83 

Geography_---------------------------------- l 

Geologic history------------------------------ 86 

Geologic setting __ ---------------------------- 4 

Girvanella __ -~-------------------------------- 11, 17 

Glabrocingulum binodosum____________________ 41 

quadrigatum_ ----------------------------- 41 Glide faults, defined__________________________ 7, 64 

origin ___ --------------------------------- 74 

Glyptospira sp __ ------------------------------ 50 

Gold __ --------------------------------------- 77, 83 

Goniatites granosm __ ------------------------- 40 

Gordon, MacKenzie, Jr., fossil identification _____ __ ___________ 36, 40, 41, 44, 48,50 

Goshute Canyon Formation__________________ 7 

Grandauarispina sp _____ ______________________ 44, 45 

granosus, Gonia.tites_ _ _ _ _ _____ ______ _ _ __ __ _ _ ___ 40 

Grasshopper Canyon fault____________________ 70 

gratiasus, Tylonautilus__ __ _ __ __ _ _ _ _ _ _ _ _ __ __ __ _ 40 

GraveL _________ _____________________ ______ __ 63,64 

Guilmette Formation ______ 22, !5, 29, 67, 69, 78, 83, 87 

Gypidula munda ______________________________ 30,31 

H 

Halysites catenularia_ _ ___ __ _ _ __ _ _ __ __ _ _ __ __ ___ 23 

sp _____ ---- __ ---- ___ __ ____________________ 21,23 

Hamilton, J. C., analyst___________________ ___ 61 

Heliconia sp_ _ _ __ _ _ __ _ __ _ _ _ _ _ __ __ __ __ ______ ___ 53 

Hematite_________ ____ ___________ __ __________ _ 82 

Heritschioides sp_ _ _ ___ _ __ _ _ ______ ____ __ _ _ __ __ _ 50 

hermosana, Antiquatonia ______________________ 44,45 

hesperium, Cravenoceras___ _ _ _ __ _ _ _ _ __ __ __ _ _ _ _ _ 40 

Heteralosia sp____ __ _ _ __ _ ___ _ _ __ _ _ _ _ __ __ _ __ _ __ _ 50 

Hintzeia celsaora_ __ _ _ __ _ _ __ _ _ _ _ __ __ __ __ _ _ _ _ __ _ 19 

HomalophyUites sp__ _ __ _ _ __ _ _ _ _ __ __ __ __ _ _ _ _ __ _ 36 

Hormotoma sp____________________________ ___ _ 19 

Horse Canyon Formation________________ ____ 7 

Hiibnerite___ __ __ ____ ___ _ __ _ _ _ _ __ _ _ ____ _ _ __ __ _ 82 

Hustedia sp ________________________ ________ 40, 44,45 

Hypagnostus______________________________ ___ _ 14 

Hypothyradina sp _________________________ ____ 30,31 

Hypothyridina sp _____ ______________ ______ ____ 30,31 

Hystriculina sp _______________________________ 44,45 

Hystricurus millardensis_____ _ _ _ __ __ __ __ ___ ___ _ 19 

lllaenus utahensis__ _ _ __ __ __ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ 19 

iUipahensis, Lonsdizleia ____ ____________________ 46,47 

increbescens, Spirifer ___ ____ ___________________ 44,45 

Indices of refraction, glass _________ __ ___ ___ 57, 61, 62 

inflata, lnflatia_____ __ __ __ __ __ __ __ ____ __ __ ___ _ _ 40 

lnflatia inflata_ _ __ _ _ _ __ __ __ __ _ _ __ __ __ __ __ __ _ __ 40 

sp. A __________ ____ __________________ __ 40, 44,45 

sp ___________________________ __________ 40, 44,45 

infundibulum, Chonophyllumsp __________ ____ _ 32,33 

insolita, Pseudomera_ _ _ _ _ __ __ _ _ __ __ _ _ __ _ _ _ _ _ _ _ 19 

Introduction_________________ ________________ 2 

Intrusive bodies, quartz dacite___________ ___ _ 60 

quartz-latite vitrophyre_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 58 

J 

Joana Limestooe ____________________ 35, 68, 69, 78,87 

Joints________________ ________________________ 61 

Jurassic System____ ____________ __________ ____ 51 

K 

Kaibab Limestone____________________________ 48 

Kalamazoo Volcanics _________________________ 53,59 

INDEX 

kanoshensis, Kanoshia ___ _____________________ _ 

Kanoshia kanoshensis ___ _____________________ _ Kanosh Shale __________ _______________ ______ _ 

kaskaskiensis, Ortholetes ____ __________ ______ __ _ 

Page 

19 

19 

18 

40 

Werriea___ _________ ______ ___ ___ __ _________ 40 

Kawina selapugia_____________________ _______ 19 

Kinsey Canyon Formation_ _____ _____________ 56 

KirkeUa sp__________________ __ _______________ 19 

kirki, Martinia____ ________ __ _______ _______ ____ 25 

Kirkina sp_____________ __________ _____________ 19 

Kleopatrinaftatateeta _____ __________________ 46, 47,50 

Knightites (Retispira) sp___ ________ ___________ 50 

Kochaspis dispar __ _ __ ____ _ _ _ _ __ _ _ _ __ __ _____ _ __ 11 

Kolcheck mine ________________ ___ _______ 4, 11,21,82 

Kozlowskia carboniferum polypleurum_ _ _ _ _ _ _ _ _ 40 

Leiorhynchus carboniferum________________ 40 

nuda _______ _______ _______________________ 44,45 

sp __________ ________ __ ____ ___________ _____ 40,45 

L 

Lacustrine deposits__ ______ ___________________ 63 

Lake Bonneville_------- --------------------- 64 

Laketown Dolomite __________________________ tl, 68 

lanceolatus, Podozamites _ _ ___ __ _ _ __ _ _______ _ _ _ 53 

Late Pleistocene or Recent structural features_ 73 

Lake Tertiary or early Pleistocene, structural 

features___________________________ 72 

Latitic rocks__ ___________ ______ _______________ 58 

Lead ____ __________________ ______ ___ _ 77, 82, 83, 84,86 

Leioclema______ __ ___ _ __ __ _____ ____ _ ____ __ __ __ _ 41 

Leiorhynchus carboniferum, Kozlowskia_ _ _ _ _ _ _ _ 40 

Leperditia bivia_ _ _ _ _ _ __ __ _ _ __ ________ __ __ _ _ _ _ _ 19 

Lepojopyge___ _ _ ___ __ _ _ __ _ _ __ __ _ ____ _ __ __ _ ___ _ 14 

Limestone, Cambrian and Ordovician________ 16 

Limipecten sp __ --------------------------- ___ 46,47 

Limonite____ _______ ____ ______ ______________ __ 78 

Lincoln Peak Formation, description_________ 1$, 

17, 55, 67, 68, 73, 75.83 

Linoproductid sp_ ____ __ _ _ __ __ _ _ ____ __ __ _ _ __ _ __ 36 

Linoproductus prattenianus ___________ ________ 44, 45 sp __________ ___________ ___________ _______ 44,45 

Lissochonetes sp ______________________________ 44,45 

Lithostrotionella dilitata _______ ______ __ ____ _ 46, 47, 50 

sp. A____________ ___________ __________ ____ 36 

sp ______________ _________ _____________ ____ 46,47 

Lonsdaleia illipahensis _____ _______________ __ __ 46, 47 

Lophamplexus sp_ __ _ __ __ ___ ___ __ ____ __ _ _ __ _ _ _ 50 

Loxonema sp__________________________________ 36 

Lower major thrust plate, structure__________ 67 

M 

Macgeea sp ______________________________ ______ 32,33 

Macronotella sp_ ___ __ ____ __ __ _ ___ ____ _ __ __ _ __ _ 19 

Majors Place, description_ ----- ----------_____ 3 

mineralization_____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 82 

Malachite ______ ___ ____ _____ ______________ ____ 78, 82 

Manganese_____ _____ __ ____ ______ ______ ____ ___ 77 

Marginatia sp ________________________ ------ __ _ 36 

Martinia kirkL ___ __ _________ ____ ___ ~-- __ _ _ __ _ 25 

sp_ ___________ ____ _____ _______ ____________ 40 

mccutcheonae, Syringopora_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 46, 47 

Members, Guilmette Formation ___________ t6,t1,t8 

Merriam, C. W., fossil identification__________ 31 

merriami, Cravenoceras _______________________ - 40 

mesolobus decipiens, Muolobus ________________ .. 44,45 

Mesolobus mesolobus decipiens ____ _______ _____ _ 44, 45 

Mesozoic structural featurP.S_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 66 

Metamorphism, Lincoln Peak Formation _____ 13, 15 

Precambrian and Cambrian rocks_ _____ _ 14 

Metasedimentary rocks ____________________ __ - 7 

Methods of investigation ___ ______ ____ __ ____ --- 2 

michaelis, Orthambonites ____ __________________ - 19 

Middle or late Tertiary structural features____ 70 

millardensis, Hystricurus___ _ _ __ __ _ _ _ _______ _ _ _ 19 

Millerellids _________________________ ------ _ __ _ 50 

Mineralization________________________________ 82 

Mississippian System ______________________ 29, 35,41 

Mitorthoceras crebriliratum ____ ---------------- 40 

perfilosum__ _ _ _ __ _ ___ __ _ _ __ ___ ___ ______ ___ 40 

Monodierodina SP----------------------------- 48 

Page 

montanensis, Spinatrypa __ -------------------- 30,31 

Mourlonia sp __ ------------------------------- 41 

Multithecopora sp. A_------------------------- 46, 47 

sp. B-'------------------------------------ 46,47 

munda, Gypidula_ ---------------------------- 30,31 

Murchisonia SP-------------------------------- 32,33 

muricatina, Desmoinesia __ -------------------- 44, 45 

N 

Naticopsis sp ___ ------------------------------ 41 Navajo Sandstone____________________________ 87 

Neoglyphioceras cloudi utahense _ -------------- 40 

subcirculare __ ______________ ------- __ ------ 40 

Neophricodothyris _______________ -------------- 50 

Neospirifer dunbari_ _ ------------------------- 44,45 

sp_ --------------------------------------- 44,45 

Nervostrophia sp_ ----------------------------- 30,31 

nevadensis, RhipidomeUa __ ----------------- 40, 44, 45 

Ninemile Formation__________________________ 18 

Normal faults_------------------------------- 77 North Creek Formation______________________ 62 

Nuculoidea sp __ ------------------------------ 41 nuda, Kozlowskia _____________________________ 44,45 

Nudirostra carya ______________________________ 30,31 

sp_ --------------------------------------- 30,31 

0 

occidum, Spirifer ----------------------------- 44,45 

Older alluvial fan graveL____________________ 6! 

Olenellus _ ------------------------------------ 7 sp ________ --- ___ ------ __ ____ _______ _ __ __ __ 10 

Oliver, W. A., Jr., fossil identification___ _____ 30 

Omphalotrochus whitneyi_ --------------------- 50 

opimus, Spirifer ___ --------------------------- 44, 45 

Oquirrh Formation __ ------------------------ 48,51 

orbicularis, Cleiothyridina __ ------------------- 44,45 

Orbiculoidea sp ___ ------------------------- 40, 44,45 

Ordovician System___________________________ 18 

Ore minerals __ ------------------------------- 78 

Origin, structural features __ ------------------ 73 

Orthambonites michaelis _ ---------------------- 19 

sp_ --------------------------------------- 19 

Orthoid brachiopod-- ----~-------------------- 19 

Ortholetes kaskaskiensis __ --------------------- 40 

Orygmophyllum SP---------------------------- 46,47 

Ovatia sp. A_--------------------------------- 44,45 

sp_ --------------------------------------- 40 

ozarkana, Composita __ ___ --------------------- 44,45 

p 

PachyphyUum SP----------------------------,- 32,33 

Pachypora sp_ -------------------------------- 32,33 

Pagetia sp __ ---------------------------------- 12 

Paleoneilo sp __ ------------------------------- 41 

Paleonusula sp _ ------------------------------ 50 Palmer, A. R., quoted ____________________ 12, 14,18 

Paranileus SP--------------------------------- 19 

Parker, C. L., analyst------------------------ 61 

Pelecypod __ ---------------------------------- 41 

Penniretipora SP------------------------------ 46,47 

Pennsylvanian System_______________________ 41 

Pequop Formation___________________________ 51 

perjilosum, Mitorthoceras __ -------------------- .40 

Permian System ___ -------------------------- 41,43 

Permophorus sp ___ --------------------------- 50 

Peronopsis ____________ -----------------_______ 14 

Peruvispira sp_ ------------------------------- 46,47 

petersoni, Eleutherocentrus _ ------------------- 19 

Petrocrania chesterensis------------------------ 40 

Phacellophyllum sp_ -- ---~------------ -------- 32,33 

Phestia sp_ ----------------------------------- 41 

Piermont Group __ --------------------------- 7 Pilot Shale __________________________ 29, 68, 69, 78,87 

Pioche Shale_------------------------------ 9, 68,82 

placitus, Cyrtospirijer __ ----------------------- 30,31 

Plaesiomys subquadrata _ ---------------------- 21 

Plagioglypta SP------------------------------- 50 

Pleurotomariacens____________________________ 50 

Podozamites lanceolatus ----------------------- 53 

Pogonip Limestone___________________________ 16 
Page 

pogonipensis, Uromystrum____________________ 19 

Pole Canyon Limestone ________________ 10, 55, 62,68 

Polidevcia SP---------------------------------- 41 

polypleurum, Kozlowskia carboniferum_________ 40 

Polypora SP----------------------------------- 46,47 

Porphyritic rhyolite dikes_------------------- 51 

Posidonia wapanuckensis______________________ 41 

prattenianus, Linoproductus ___________________ 44,45 

Precambrian and Cambrian rocks, Metamorphism_--------------------------- 14 

Precambrian System __ ----------------------- 7 

princeps, ThysanophyUum_ ------------------- 46,47 

ProducteUa sp_ ------------------------------- 30,31 

Production, Taylor mining district_---------- 78 

Productoid _____ ---- ___ ---- ___ ----------------- 44 

Promontory Range___________________________ 8 

Promytilus sp_________________________________ 41 

Prospect Mountain Quartzite _________ 7, 19, 55, 68,82 

Pseudofusulina sp_ --------------------------- 46,47 

Pseudomera imolita _________________ --------- 19 

sp ___ ----------- ____ ___ ___ _____ ___ ___ ___ __ 19 

Pseudoolenoides acicaadus_____________________ 19 

dilectus __ --------------------------------- 19 

Pseudoschwagerina SP---~------------------ 46, 47,48 

Pseudozygopleurid ___ ------------------------- 50 

Ptarmiganoides poulsenL_____________________ 11 

Ptychagnostus __________________________ ------- 14 

Pugnoides schuchertL ------------------------- 30,31 

sp_ --------------------------------------- 30, 31 

Punctospirifer tramverBUB_____________________ 40 

sp ______________________________ ----- ___ __ 40 

Pyrite __________________________________ ------ 82 

Q 

quadrigatum, Glabrocingulum_ ---------------- 41 

Quartz latite vitrophyre______________________ 56 

Quaternary System___________________________ 6B 

R 

Rayonnoceras sp_ ----------------------------- 40 

Receptaculites SP------------------------------ 19 

resupinoides, Schizophoria __________________ 40, 44,45 

Reticulariina campestris ____________________ 40, 44,45 

sp_ ------------------------------------ 40, 44, 45 

Reticycloceras croneisL _ ----------------------- 40 

(Retispira) sp. Knightites______________________ 50 

Rhipidomella nevadensis ____________________ 40, 44,45 

sp_ --------------------------------------- 44,45 

Rhynchopora SP------------------------------- 44,45 

Rhyolite dikes ____ --------------------------- 51, 78 

Rib Hill Sandstone __________________ 49, 54, 55, 70,87 

Ridges __ ------------------------------------- 63 

Riepetown Sandstone_----------------------- 43,48 

Roads ____________________ -------_____________ 3 

robufta, Derbyia _______________________________ 44,45 

Roemeripora sp __ ----------------------------- 50 

Rugoclostus SP-------------------------------- 44,45 

s 

Scheelite______ ___ ___ ___ _ ___ ____ ___ _ _ ___ ___ _ ___ 82 

Schell Creek Range thrust fault_------------- 68 

Schizophoria resupinoides ___________________ 40, 44,45 

texana _________________________________ 40, 44,45 

sp_ --------------------------- 30, 31, 36, 40, 44, 45 

INDEX 

Page 

SchuberteUa sp __________________________ 46, 47, 48,50 

schucherti, Pugnoides __________________________ 30,31 

Schwagerina sp __ ----------------------- 46, 47, 48,50 

Sequoia fastigata_______________________________ 53 

Sevy Dolomite _________________________ tt, 68, 69,87 

sexapugia, Kawina____________________________ 19 

Shale and tuffaceous sandstone, Cretaceous 

or Tertiary_______________________ 59 

Shale member, Cambrian and Ordovician 

limestone ____________ ------------- 17 

Sheep Pass Formation________________________ 56 

Sheeprock Range_____________________________ 8 

Schell Creek Range thrust fault_ _____________ 66,75 

Shoshone Lake_______________________________ 63 

Silurian System______________________________ S1 

Silver----------------------------------- 77, 82, 83,86 

Simonson Dolomite _____________________ 21, !4, 68,69 

Simphysurina cleora __________________________ '" 19 

Slump block, defined_________________________ 73 

Sphenotus SP---------------------------------- 41 Spinatrypamontanensis _______________________ 30,31 

sp_ --------------------------------- 30, 31, 32,33 

Spirifer argentarius ____ ----------------------- 32, 33 

centronatus _ ------------------------------ 36 

increbescens ___ ---------------------------- 44, 45 

occiduus_ --------------------------------- 44,45 

opimus _ ---------------------------------- 44, 45 

strigosus_ --------------------------------- 32,33 

sp_ --------------------------------- 36, 40, 44, 45 

Spring Valley, description____________________ 2 

Spring Valley Lake___________________________ 63 

Springs _____ --------------------------________ 4 Steptoe Creek fault ___________________________ 70,72 

Steptoe Valley, description_------------------ 2 

Stibnite_ ------------------------------------- 78,82 

Stictostroma sp_ ----------------------------- 34,35 

Straparollus (Euomphalus) sp_ --------------- 36 

sp _____ ---------- ___ ___ ____ __ _ ______ ___ _ _ _ 36 

Stratigraphy ___ ------------------------------ 7 

Streams __ ------------------------------------ 4 

Striatopora sp __ ------------------------------ 32,33 

strigosus, Spirifer _ ---------------------------- 32,33 

Stroboceras SP--------------------------------- 40 Strongocephalus___ ___ ___ __ __ ____ ___ _______ __ __ 25 

Stropheodonta SP------------------------------ 32,33 

Structural geology____________________________ 64 

Styliolina ___ __________ ------- _________________ 34, 35 

subcirculare, Neoglyphioceras__________________ 40 

sublamellosa, Cleiothyridina ____ ------------ 40, 44,45 

suborbicularis, Cleiothyridina __ ---------------- 40 

subquadrata, Composita_ . ------------------ 40, 44,45 

Plaesiomys ___ ---------------------------- 21 

subtilita, Composita ___ --------------------- 44, 45,50 

Success mine_________________________________ 83 

Syringopora mccutcheonae_ -------------------- 46,47 

sp_ --------------------------------- 32, 33, 46,47 

T 

Tabulipora arcturusensis_ --------------------- 50 

Tabulophyllum sp ___ ------------------------- 32,33 

Tamberlaine Canyon, adits and prospects____ 83 

Taosia SP------------------------------------- 50 

Taylor fault __________________________________ 72,78 

Page 

Taylor mining district________________________ 77 

Tentaculites sp __ ----------------------------- 34,35 

Tenticospirifer: sp_ ---------------------------- 32,33 

Terraces __________ -------------- ___ ---------__ 63 

Tertiary System_---------------------------- 51,59 

texana, Schizophoria __ --------------------- 40, 44,45 

Thamnopora SP------------------------------- 32,33 

Thomasaria altumbona_ ----------------------- 32,33 

Thrust fault, defined __ ----------------------- 64 

origin ___ --------------------------------- 75 

Thysanophyllum princeps _____________________ 46,47 

sp_ --------------------------------------- 46,47 

Tomera Formation___________________________ 43 

Torynifer sp __ -------------------------------- 44, 45 

Trace elements_______________________________ 83 

Chainman Shale __ ----------------------- 39 

transversus, Punctospirifer _ ------------------- 40 

Trepospirea SP-------------------------------- 41 Trigonocerca sp_______________________________ 19 

Triticites SP----------------------------------- 46,47 

trojana, Caninia ______________________________ 46,47 

Tuff lenses_---------------------------------- 62 

Tungsten-_------------------------------- 77, 82, 83 

Tylonautilus gratiasus_________________________ 40 

Tylothyris SP---------------------------------- 32,33 

u Uplift, regional_______________________________ 77 

Upper lava flow, quartz latite vitrophyre_____ 59 

Upper major thrust plate, structure__________ 68 

Uromystrum pogonipensis_____________________ 19 

utahense, Neoglyphioceras cloudi_______________ 40 

utahensis, Anomalorthis_______________________ 19 

IUaenus_ --------------------------------- 19 

v 

Vanadium____________________________________ 86 

verneuiliana, Eumetria________________________ 36 

VesiculophyUum sp __ ------------------------- 36 

Volcanics of Young___________________________ 62 

Volcanism____________________________________ 88 

vulgaris, Devonoproductus __ ------------------- 30,31 

w 

wapanuckensis, Posidonia_____________________ 41 

WarreneUa eclectea _____________ : ___________ :,. __ 32,33 

sp_ --------------------------------------- 32,33 

Welded tuff lenses_--------------------------- 58 

Werriea kaskaskiensis __ ----------------------- 40 

White Pine Shale_____________________________ 29 

White Sage Formation________________________ 56 

whitneyi, Omphalotrochus __ ------------------- 50 

Windfall Formation __ ------------------------ 17 

y 

Yochelson, E. L., fossil identification_________ 50 

Younger alluvial fan graveL_________________ 63 

z 

Zaphrentites SP------------------------------- 36 

Zinc _________________________________ 77, 82, 83, 84,86 

U.S. GOVERNMENT PRINTING OFFICE : 1967 0 - 240-303