Cambrian and Precambrian 

Rocks of the Groom District 

Nevada, Southern Great Basin

GEOLOGICAL SURVEY BULLETIN 1244-G

Prepared on behalf of the

U. S. Atomic Energy Commission

Cambrian and Precambrian 

Rocks of the Groom District 

Nevada, Southern Great Basin

By HARLEY BARNES and ROBERT L. CHRISTIANSEN

CONTRIBUTIONS TO STRATIGRAPHY

GEOLOGICAL SURVEY BULLETIN 1244-G

Prepared on behalf of the

U. S. Atomic Energy Commission

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

STEWART L. UDALL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

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

Washington, D.C. 20402 - Price 20 cents (paper cover)
CONTENTS

	Page 

Abstract_______________________________________________ G 1

Introduction. _____________________________________________________ 1

Stratigraphy. _____________________________________________________ 4

Johnnie Formation____________________________________________ 4

Stirling Quartzite._____________________________________________ 4

Wood Canyon Formation_____________________________________ 5

Zabriskie Quartzite-___________________________________________ 10

Carrara Formation____________________________________________ 10

Bonanza King Formation_____________________________________ 12

Nopah Formation.____________________________________________ 13

Correlation.______________________________________________________ 20

References cited.__________________________________________________ 32

ILLUSTRATIONS

Page 

FIGURE 1. Index map of part of southern Great Basin_________________ G 2

2. Reconnaissance geologic map of Groom district, south end of

Groom Range.______________________________________ 3

3-6. Columnar sections of:

3. Incomplete Johnnie Formation and Stirling Quartzite-_ 6

4. Wood Canyon Formation, Zabriskie Quartzite, and

Carrara Formation.___________________________ 8

5. Bonanza King Formation._________________________ 14

6. Nopah Formation________________________________ 20

7. Correlation of Cambrian and some Precambrian formations in

southern Great Basin.._______________-_________-__---- 22

TABLES

Page 

TABLE 1. Comparison of stratigraphic units used by various authors in

Groom district and at Nevada Test Site________________ G16

2. Comparison of stratigraphic units of Groom and Pioche districts. _________________________________-------_---- 26

m

CONTRIBUTIONS TO STRATIGRAPHY

CAMBRIAN AND PRECAMBRIAN ROCKS OF THE GROOM 

DISTRICT, NEVADA, SOUTHERN GREAT BASIN

By HARLEY BARNES and ROBERT L. CHRISTIANSEN

ABSTRACT

More than 14,000 feet of conformable Cambrian and Precambrian rocks is 

exposed in the Groom district in southwestern Lincoln County, Nev. The lower 

half of this stratigraphic section is chiefly quartzite and siltstone, the upper half 

chiefly limestone and dolomite. Included are part of the Johnnie Formation 

(>300 ft) and the Stirling Quartzite (>2,930 ft) of Precambrian age; the 

Wood Canyon Formation (2,285 ft) of Cambrian and Precambrian age; and 

the Zabriskie Quartzite (220 ft), Carrara Formation (1,879 ft), Bonanza King 

Formation (4,355 ft), and Nopah Formation (2,035 ft) of Cambrian age.

The stratigraphic units exposed in the Groom Range can be recognized for 

more than 100 miles to the west and south, and the same formational names 

can be used throughout that region. The units can also be correlated with the 

Cambrian and Precambrian rocks of the Pioche district, but different stratigraphic nomenclature is preferred for the Pioche area.

INTRODUCTION

A nearly complete conformable section of Cambrian and upper 

Precambrian rocks is exposed in the Groom mining district, at the 

south end of the Groom Range in southwestern Lincoln County, Nev. 

(fig. 1). Although the section was described by Humphrey in 1945, 

redescription and reinterpretation seem worthwhile because considerably more is now known of regional stratigraphic relations in the 

southern Great Basin and because the revised interpretation of the 

Groom section affects the regional picture significantly. Also1 , on the 

basis of more complete data, this report revises an earlier outline of 

stratigraphic nomenclature for Cambrian rocks in the Nevada Test 

Site area (Barnes and Palmer, 1961).

Because it is on the Nellis Air Force Range, the Groom district is 

not readily accessible at present. Measurement of the stratigraphic 

section and preparation of the reconnaissance geologic map (fig. 2) 

were done with permission of the Air Force as part of geologic mapping at the Nevada Test Site of the U.S. Atomic Energy Commission.

Gl
G2 CONTRIBUTIONS TO STRATIGRAPHY

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FIGUEE 1. Map of part of southern Great Basin.
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G3

115°45'

EXPLANATION

[ Qal | 

Quaternary alluvium

Tertiary volcanic 

and sedimentary 

rocks

Eureka Quartzite I 

Pogonip Group 

Nopah Formation

Bonanza King 

Formation

Carrara Formation

3 MILES

CONTOUR INTERVAL 200 FEET 

DATUM IS MEAN SEA LEVEL

Zabriskie Quartzite

Wood Canyon 

Formation

pp-Cs-j 

Stirling Quartzite

BBI

Johnnie Formation.

Line of measured 

section

FIGUBB 2. Reconnaissance geologic map of Groom district, south end of Groom 

Range (in part after Tschanz and Pampeyan, 1961). Lines of measured sections are discussed in text.

Of the more than 14,000 feet of Cambrian and Precambrian rocks 

exposed at Groom, the lower half is chiefly quartzite and siltstone with 

minor limestone and dolomite and the upper half is chiefly limestone 

and dolomite with minor siltstone and shale. The dominantly clastic 

part of the section exposed at Groom includes the upper part of the 

Johnnie Formation, most of the Stirling Quartzite, and all the Wood 

Canyon Formation and Zabriskie Quartzite (figs. 3, 4). The 

dominantly carbonate part of the section consists of the Carrara, 

Bonanza King, and Nopah Formations (figs. 4,5,6).

Because the Groom section contains more than 5,200 feet of strata 

conformably below the lowest fossils of Early Cambrian age, the 

problem of defining the base of the Cambrian System is pertinent to
G4 CONTRIBUTIONS TO STRATIGRAPHY

this discussion. The definition used here is one presently accepted 

by the U.S. Geological Survey and follows generally the proposal of 

Wheeler (194T) in placing the base of the Cambrian at the base of 

the strata containing the oldest Early Cambrian fossils and at the base 

of equivalent unfossiliferous strata. This usage has been found to be 

practical in the region considered here because the lowest Early Cambrian fossils known throughout a large region occur in the same 

stratigraphic unit, the upper part of the Wood Canyon Formation.

STRATIGRAPHY

JOHNNIE FOBMATION

Only 300-400 feet of the upper part of the Johnnie Formation is 

exposed locally at the western base of the Groom Range (fig. 2). This 

part of the Johnnie is composed of brownish, greenish, and reddish 

thin-bedded to laminated siltstones and calcareous siltstones (fig. 3). 

Humphrey (1945, p. 15) mentioned "a very flat-dipping, thinbedded, red and white banded sandstone * * * exposed in 

gulches * * *" on the west flank of the Groom Range. In his reconnaissance, he considered these rocks as probably an erosional product 

of the Prospect Mountain Quartzite (this report, table 1) and, therefore, as much younger than the quartzite. Mapping has shown that 

these rocks are at the base of the stratigraphic section. Similarity to 

sections in the Halfpint and Papoose Ranges to the southwest and 

south (fig. 1) indicates that the strata are siltstones and calcareous siltstones of the Rainstorm Member of the Johnnie Formation.

Nolan (1929, p. 461-463) named the Johnnie Formation for Johnnie 

Wash in the northwest part of the Spring Mountains, about 60 miles 

south of the Groom district (fig. 1). The Rainstorm Member, named 

by Barnes, Christiansen, and Byers (1965), is the top 1,025 feet of 

the Johnnie in the Halfpint Range about 15 miles southwest of Groom. 

In the Groom Range and locally in the Halfpint Range, the uppermost 

part of the Rainstorm Member has been cut out by bedding-plane 

faults.

On the basis of its stratigraphic position, the Johnnie Formation is 

regarded as Precambrian in age.

STIRLING QUARTZITE

The Stirling Quartzite was named by Nolan (1929, p. 463) for exposures near Mount Stirling in the Spring Mountains. In the Groom 

district the Stirling is chiefly nonmicaceous quartzite with less 

abundant siltstone and micaceous quartzite, as well as a few thin beds 

of limestone. The formation is dominantly reddish in the lower part
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G5

and grayish pink in the upper part; it is more than 2,930 feet thick. 

On the basis of comparison with nearby areas, we estimate that before 

faulting the Stirling in the Groom district was 3,400-3,500 feet thick.

We have divided the Stirling at Groom into four members, the 

upper one comprising three lithologic units (fig. 3). The terminology 

of these members follows that of Stewart (1966). Member A, at the 

base, is composed of cliff-forming reddish to purplish medium-grained 

to pebbly-conglomeratic quartzite. Member B is a micaceous generally 

fine-grained quartzite with conspicuous planar lamellae. The total 

thickness of A and B could not be measured because of faults, but 

member A is more than 555 feet thick and member B is more than 

755 feet. Mapping in nearby ranges convinces us that most of member B is present in the measured section but that about half of member 

A is missing. No other map units are present between members A 

and B in this region. Member C is 555 feet thick in the Groom Kange 

and is composed of interbedded grayish-red very micaceous siltstone 

and nonmicaceous fine-grained thin-bedded quartzite. Micaceous siltstone is the dominant lithology at the slope-forming base of member 

C but becomes less abundant upward. The top 165 feet of the member 

forms a dark-colored ledgy cliff with conspicuous planar bedding. 

There is no member D in the Groom section. Member E consists of 

three units. The lowest, unit 1, is 235 feet of pinkish-gray crosslaminated quartzite that forms a light-colored cliff. The slope-forming unit 2, 440 feet thick, is yellowish-brown micaceous quartzite with 

interbedded light-gray nonmicaceous quartzite and a basal siltstone 

with a few thin beds of limestone. Unit 3 of member E is 390 feet of 

cliff-forming grayish-pink quartzite.

Wherever exposed in the Groom Kange and in most places in the 

Papoose and Half pint Kanges, the basal contact of the Stirling Quartzite is a bedding-plane fault. Comparison of lithologies at this contact in the three ranges, however, indicates that none of the basal 

Stirling Quartzite has been cut out by the faults and only locally is 

much of the Rainstorm Member of the Johnnie Formation missing. 

Sections are exposed at several places in the Papoose Range where the 

contact is apparently conformable.

No fossils have been found in the Stirling Quartzite, whose stratigraphic position indicates that it is of Precambrian age.

WOOD CANYON FORMATION

The Wood Canyon Formation was named by Nolan (1929, p. 463- 

464) for exposures in the northwestern part of the Spring Mountains. 

In the Groom district the Wood Canyon is 2,285 feet of siltstone and 

quartzite with minor sandy limestone; quartzite predominates in the

249-926 O 67 2
G6 CONTRIBUTIONS TO STRATIGRAPHY

SYSTEM

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MEMBER

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UNIT

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COLUMN

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REF. 

NO.

12

10

9

8

7

6

5

4

3

2

1

FIGTJBE 3. Columnar section of incomplete Johnnie 

Formation and Stirling Quartzite in Groom district.

reddish ridge-forming middle part of the formation and siltstone in 

the lower and upper parts. The resulting threefold character of the 

Wood Canyon is similar to that in the type locality.

The Wood Canyon in the Groom Kange is divided into three members (fig. 4). The lower member, 535 feet thick, is a slope-forming 

yellowish-gray micaceous siltstone and grayish-orange micaceous shale 

with interbeds of fine-grained quartzite and a few beds of sandy limestone. The middle member, 1,005 feet thick, is dominantly quartzite 

and can be divided into two units. The lower 785 feet is chiefly 

grayish-red medium- to coarse-grained quartzite that forms a ridge 

or rounded cliff. The upper 220 feet is light-gray fine-grained quartzite and interbedded dusky-yellow micaceous siltstone and fine-grained
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G7

RNEQF- LITHOLOGY

12 Quartzite, grayish-pink to pale-red, medium-grained, well-sorted to moderately sorted; 

1- to 5-ft beds with partings between, laminated and cross-laminated; forms cliff; 

basal 200 ft less well cemented than above; center part has a few pebbly beds; top 

bed is pebbly calcareous sandstone.

11 Quartzite, yellowish-brown, micaceous, fine-grained; thin beds 1-10 ft; thick interbedsof 

white medium-grained well-sorted laminated quartzite; sparse in basal part, more 

abundant upward and dominant at top. Unit forms steep slopes broken by a few 

ledges.

10 Siltstone, light-brown; little mica; %- to Vi-in. partings; forms slope. Basal 25 ft has 

\ few thin beds of silty limestone that weathers moderate yellowish brown.

Quartzite, pinkish-gray, medium- to fine-grained, well-sorted; 3- to 5-ft beds, cross laminated, rare micaceous partings. Forms cliff.

Quartzite and siltstone; pale-red to grayish red cross-laminated quartzite, l-to3-ft beds; 

siltstone 1- to 2-in. beds; unit forms ledgy cliff.

7 Quartzjte and siltstone; quartzite grayish red, fine to very fine grained, moderately 

sorted; 6- to 12-in. beds, discontinuous laminae. Siltstone micaceous, poorly 

sorted, 1- to 10-in. beds, shaly weathering; weathers yellowish gray; unit forms ledgy 

slope. Basal 40 ft. siltstone micaceous, grayish red, 'A-in. partings; unit forms slope.

Quartzite, grayish-red (dominant) to grayish-pink, fine- to medium-grained, well-sorted; 

2- to 6-ft beds, conspicuously laminated, sporadically cross laminated; partings of 

very fine grained micaceous quartzite between beds; color bands 2-20 ft thick; forms 

ledgy slope.

Quartzite. grayish-red to grayish-red-purple, fine- to medium-grained, well-sorted (minor 

mica), well-laminated; partings Vz- to 6-in.; forms slope.

Fault

.4 Quartzite (like unit 2 below).

)uartzite, red-purple to grayish-red-purple, medium-grained to pebbly conglomeratic, 

moderately sorted; 3- to 5-ft beds; no partings; cross-laminated but poorly stratified on larger scale; forms cliff.

Quartzite, pale red, medium- to coarse-grained, well-sorted; 2- to 3-ft beds, cross-laminated; forms cliff.

1 Siltstone, light-brown to yellowish-green in upper part, pale-red to orange-pink below, 

weakly to moderately calcareous, laminated; forms slope.

FIGUBE 3. Continued

quartzite that form a ledgy slope. The upper member of the Wood 

Canyon, 745 feet thick, forms a ledgy slope of dusky-yellow micaceous 

siltstone, shale, and fine-grained quartzite with interbeds of light-gray 

medium-grained quartzite. In the upper part are beds of calcareous 

sandstone and sandy limestone.

The basal contact of the Wood Canyon is a sharp but conformable 

contact between quartzite and siltstone.

The lowest stratigraphic position at which fossil organisms have 

been found in the Groom Range is about 325 feet below the top of the 

Wood Canyon Formation. Fragments of olenellid trilobites are 

preserved on the bedding surfaces of laminated quartzite. Trilobites, 

pelmatozoan debris, and Scolithus occur between this lowest fossil 

horizon and the top of the formation. The lowest stratigraphic posi-
G8 CONTRIBUTIONS TO STRATIGRAPHY

SYSTEM

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THICKNESS 

(FEET)

190

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220

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300

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785

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195

REF. 

NO.

25

23

22

21

20

19

18

17

16

15

14

13

FIGUBE 4. Columnar section of Wood Canyon Formation, Zabriskie Quartzite, and Carrara Formation 

in Groom district.
CAMBRIAN, PRECAMBBIAN BOCKS, GROOM DISTRICT, NEVADA G9

RNE0F' LITHOLOGY

25 Limestone, in part light-gray, massively outcropping, and in part medium-gray, thin-bedded, with discontinuous cuspate silty limestone laminae; forms benches. Silty 

\ limestone predominant in basal 70 ft.

24 Limestone, medium gray, thin-bedded, with irregular and discontinuous wavy to cuspate 

silty limestone interbeds that weather dark yellowish orange; scarce Girvanella near 

\ top; calcareous siltstone in basal 30 ft; forms cliff.

23 Siltstone, moderate-yellowish-brown, micaceous, generally calcareous; beds mostly %-% 

in. thick, but 1-2 ft in upper 50 ft of unit; forms slope, but upper 50 ft forms bluff.

22 Limestone and siltstone: limestone medium dark gray, oolitic; abundant Girvanella; 4-

to 24-in. beds, silty limestone partings; siltstone as dusky-yellow thin interbeds in

_____limestone, especially in lower and upper parts; forms bluffs. __ ___

Shale, siltstone, and limestone; shale and siltstone greatly predominant, olive gray to 

yellowish brown; siltstone occurring as l-to2-in. interbeds in shale; limestone only 

in a 5-ft zone starting 120 ft above base and a 15-ft zone starting 260 ft above 

base, dark gray, 1- to 12-in. beds with silty limestone partings; unit forms slope.

/ 20 Limestone, shale, and siltstone; limestone medium dark gray; 1- to 6-in. wavy beds in 5- 

to 25-ft zones with calcareous siltstone or shale partings; abundant trilobite fragments. Shale and siltstone dusky yellow to medium brown; siltstone calcareous; 

unit forms ledges.

/19 Shale, siltstone. sandstone, and quartzite. brown-duskv-vellow. olive, dusky-red; sandstone fine grained; quartzite micaceous, poorly to moderately sorted, only in basal 

____30 ft; unit forms slope.__________________________________

18 Quartzite, pale-red to pinkish-gray, medium- to fine-grained, well-sorted; l/2- to 2-ft beds 

cross laminated, laminae more conspicuous in upper than lower part; abundant 

Scolithus in upper part; basal 45 ft has interbeds of calcareous sandstone and mi- 

\ caceous siltstone; sparse pebble lenses; unit forms cliff.

17 Siltstone. shale, quartzite. sandstone, and limestone: siltstone and shale dusky yellow to 

light brown, generally micaceous, 1- to 6-in. beds; quartzite and calcareous sandstone in part olive gray to yellowish gray, medium to coarse grained, moderately 

sorted, limonitic and glauconitic; quartzite in part light gray, fine to medium grained, 

well sorted; predominantly olive-gray limonitic-glauconitic quartzite in lower part; 

predominantly light gray well-sorted quartzite in upper part; 6-25 ft of siltstone and 

shale generally separated by 1-5 ft of quartzite or calcareous sandstone beds; 

______sparse limestone moderate brown, laminated; unit forms ledgy slope._______

16 Quartzite and siltstone; quartzite light gray, fine grained, moderately sorted;!- to l'/2-ft 

cross-laminated beds; siltstone dusky yellow, light olive, and grayish red, poorly 

. sorted, micaceous, locally fissile; unit forms steep slope.

juartzite. grayish-red, medium- to coarse-grained; locally pebbly in basal 25 ft; moderately sorted; Vfe- to 2-ft beds, micaceous quartzite partings, sweeping cross-lamination; finer grained toward top; upper 50 It has sporadic micaceous siltstone beds 

as thick as 6 in.; unit forms ledgy cliff.

14 Siltstone,quartzite, and limestone; siltstone and quartzite as below, no fissile shale; 

siltstone predominant generally but zones as much as 75 ft thick have quartzite 

predominant. Two beds of light-olive-gray limestone weather moderate brown; 1-ft 

___ beds inconspicuously laminated, 65 and 190 ft above base. Unit forms slope.

13 Siltstone, shale, and quartzite; siltstone and shale yellowish gray to grayish orange, micaceous, 4- to 12-in. beds; quartzite pale brown, fine to medium grained, poorly 

sorted, micaceous; unit forms slope.

FIGURE 4. Continued
G10 CONTRIBUTIONS TO STRATIGRAPHY

tion at which fossils have been found in the surrounding region is also 

in the upper member of the Wood Canyon (Stewart, 1966, fig. 2). 

Somewhat older forms occur farther west in the Andrews Mountain 

Member of the Campito Formation, which Stewart (1966) has demonstrated to be approximately equivalent to the middle member of the 

Wood Canyon. As defined, therefore, the base of the Cambrian is near 

the middle of the Wood Canyon Formation.

ZABRISKIE QUARTZITE

The Zabriskie Quartzite was originally defined by Hazzard (1937, 

p. 309) in the Nopah-Resting Springs area as a member of his expanded Wood Canyon Formation. Wheeler (1948, p. 26) changed 

the rank of the Zabriskie to formation and reinstated Nolan's original 

definition (1929, p. 464) of the Wood Canyon. In the Groom district 

(fig. 4) the Zabriskie is 220 feet of ridge-forming well-sorted crosslaminated quartzite that weathers grayish orange pink. It is 

dominantly nonmicaceous.

The contacts of the formation are gradational. The basal 45 feet 

of the formation is slightly micaceous calcareous sandstone, which 

weathers pale yellowish orange, and grayish-red cross-laminated 

quartzite with a few interbeds of grayish-red micaceous siltstone. 

The upper contact is so drawn as to place 30 feet of poorly sorted 

micaceous quartzite, siltstone, and shale in the overlying Carrara 

Formation rather than in the Zabriskie.

No organic remains have been found in the Zabriskie Quartzite, but 

sand-filled burrows called Scolitkus are abundant in the upper part. 

The Zabriskie is Early Cambrian in age because it is conformably 

underlain and overlain by rocks of known Early Cambrian age.

CARRARA FORMATION

The Carrara Formation is the name given by Cornwall and Kleinhampl (1961) to beds at Bare Mountain (fig. 1) that are transitional 

from the dominantly clastic rocks at the base of the Cambrian and 

Precambrian section into the overlying dominantly carbonate rocks. 

In the Groom Range the Carrara contains 1,870 feet of interbedded 

limestone, siltstone, shale, and quartzite. The formation is here divided into one formal and six informal members (fig. 4) which correspond to the seven members described in the Halfpint Range by 

Barnes, Christiansen, and Byers (1962).

The lower half of the formation is chiefly siltstone and shale with 

subordinate limestone and quartzite. This part of the formation 

forms ledgy slopes. The basal contact of the Carrara separates the 

well-sorted nonmicaceous Zabriskie Quartzite from the micaceous
CAMBRIAN, PRECAMBBIAN ROCKS, GROOM DISTRICT, NEVADA Gil

elastics of the 130-foot member A of the Carrara Formation. The 

member is mainly shale and siltstone, but about 25 feet below the top 

is a 6-inch bed of medium-dark-gray limestone with abundant trilobite debris. Member B of the Carrara is 300 feet of thin-bedded medium-dark-gray limestone with abundant thin interbeds of duskyyellow shale and silty shale. Member C is 505 feet of olive-gray to 

brown shale with interbedded siltstone and sparse limestone.

The upper half of the Carrara is composed of limestone with subordinate siltstone, weathering into a series of low bluffs and ridges. 

Member D, 220 feet thick, is chiefly medium-dark-gray limestone with 

abundant Girvcmella and conspicuous thin oolitic beds. Member E, 

275 feet thick, is mostly yellowish-brown micaceous calcareous siltstone. The next higher unit is the Jangle Limestone Member. The 

Jangle was originally defined as a formation by Johnson and Hibbard 

(1957, p. 339), who named it for Jangle Ridge in the Half pint Range 

about 15 miles southwest of Groom, but later the Jangle was included 

as a member of the Carrara Formation by Barnes, Christiansen, and 

Byers (1962, p. D28). The Jangle Limestone Member, 250 feet thick 

in the Groom Range, consists of medium-gray limestone that has a 

characteristic mottling formed by discontinuous irregular wavy to 

cuspate laminae of dark-yellowish-orange silty limestone. Member 

G, the uppermost unit of the Carrara Formation, is about 190 feet 

thick and is composed of rocks transitional between the interbedded 

siltstone and limestone of the upper part of the Carrara and the 

relatively pure limestone and dolomite of the basal part of the Bonanza King Formation. In the Groom district member G consists of 

thick beds of light-gray limestone of a type common in the Bonanza 

King Formation interbedded with very thin bedded to laminated limestone, mottled silty limestone, and siltstone of types common in the 

Carrara Formation. The basal 70 feet of member G is especially 

silty.

The age of the Carrara Formation is Early and Middle Cambrian. 

The fauna is largely undescribed, but A. R. Palmer (written common., 

1964) is studying the trilobites collected from both the Groom district 

and the Jangle Ridge area of the nearby Halfpint Range. Palmer 

has identified Early Cambrian olenellids from members A, B, and C. 

Trilobites from the middle of member C and from the base of member 

D represent a pr&-Albertella fauna of early Middle Cambrian age. 

Trilobites of the Middle Cambrian ATbertella zone occur in the top of 

member D, in member E, and in the basal part of the Jangle Limestone 

Member. Glossopleura-zone trilobites, also Middle Cambrian, have 

been found near the base of member G.
G12 CONTRIBUTIONS TO STRATIGRAPHY 

BONANZA KING FORMATION

The Bonanza King Formation was named by Hazzard and Mason 

(1936, p. 234) for a mine in the Providence Mountains in southeastern California, a)bout 155 miles south of the Groom Range. Hazzard's (1937, p. 316-318) original correlation of the Bonanza King 

in the Nbpah Range was based on an incorrect age determination. A 

corrected correlation by Palmer and Hazzard (1956) has since been 

used extensively throughout the southern Great Basin. In the Groom 

district the Bonanza King is 4,355 feet of limestone and dolomite (fig. 

5) with only minor siltstone and silty limestone; it forms ledgy cliffs 

and ridges. In the nearby Half pint Range (fig. 1), Barnes and 

Palmer (1961, p. C102) divided the formation into the Papoose Lake 

Member and the overlying Banded Mountain Member, a division that 

is also recognized in the Groom district.

The Papoose Lake Member, about 2,075 feet thick at Groom, was 

divided informally into three units in the Halfpint Range (Barnes and 

others, 1962, p. 1)30). These same units can be recognized in the 

Groom district. Unit A of the Papoose Lake is 410 feet of massiveweathering dark-gray mottled limestone. The basal 170 feet is 

bleached to light gray and has indistinct bedding. Unit B of the member is 115 feet of distinctly laminated to thin-bedded light- to mediumgray limestone marked by laminae of pale-yellowish-orange calcareous 

siltstone and silty limestone. Unit C of the Papoose Lake Member 

is 1,550 feet of light- to dark-gray dolomite and limestone. The lower 

third of the unit is mostly limestone; the upper two-thirds is mostly 

dolomite, much of it laminated. Much of the upper two-thirds is 

bleached and recrystallized.

The Banded Mountain Member, about 2,280 feet thick at Groom, is 

here divided into four informal units. Unit A is 180 feet thick at 

Groom and is relatively silty like the middle unit of the Papoose Lake 

Member. Unit B of the Banded Mountain Member is a 1,600-foot 

section of interbedded limestone and dolomite characterized in outcrop 

by many light and dark color bands. Unit C is 310 feet of light-gray 

to yellowish-gray limestone that is conspicuous from a distance as a 

broad buff-colored band above the thin light and dark stripes of unit 

B. Unit D at the top of the Bonanza King is 190 feet of medium- to 

light-gray limestone and dolomite with moderately abundant brownweathering silty limestone that increases in abundance upward. 

From a distance unit D appears as a gray band above the buff band 

formed by unit C.

The basal contact of the Bonanza King Formation is gradational 

but is arbitrarily placed to exclude silty limestone. All contacts between the units within the formation are also gradational, and some
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G13

of the units may vary considerably in thickness, even within the Groom 

Range.

The age of the Bonanza King Formation is Middle and Late Cambrian. In the Groom district A. R. Palmer (written commun., 1964) 

found Middle Cambrian fossils of the Glossopleura zone near the top 

of the underlying Carrara Formation and Late Cambrian fossils of 

the Dunderbergia zone in the overlying Dunderberg Shale Member. 

Humphrey (1945, p. 21) and Wheeler (1948, p. 38,50) reported a Middle Cambrian trilobite, Coelaspis ( ?), from beds here assigned to unit 

B of the Papoose Lake Member of the Bonanza King. In the Bonanza King of the Half pint Range, about 15 miles southwest of the 

Groom district, Palmer (written commun., 1960) found Late Cambrian fossils of the Crepicephalus zone 300 feet below the top of the 

formation in the base of the unit equivalent to unit D of the Banded 

Mountain Member at Groom. Another Crepicephalus zone fauna was 

collected 40 feet below the top of the formation in the Halfpint Range, 

3 feet below a fossil collection representing the Aphelaspis zone (Palmer, 1965). Trilobites of the Late Cambrian Dicanthopyge zone were 

identified by Palmer (1965) from the top 10 feet of the Banded Mountain Member in the Halfpint Range.

NOFAH FORMATION

The nomenclature of rocks between the Bonanza King Formation 

and the Lower Ordovician Pogonip Group has not been entirely satisfactory in the southern Great Basin. To point out lithostratigraphic 

relations that had become apparent in regional studies since the earlier 

work at the Test Site and to correct misconceptions that might have 

arisen from the previous stratigraphic names, we have revised the 

nomenclature for this part of the section in the Nevada Test Site area 

(Christiansen and Barnes, 1966). This revised terminology is being 

used in the Groom district (table 1).

At the Nevada Test Site the rocks between the Bonanza King and 

the Pogonip can be readily divided into three lithologic units: at 

the base, 225 feet of shale with minor very thin bedded limestone; in 

the middle, 715 feet of flaggy-splitting very thin bedded limestone 

with silty laminae and common chert; and in the upper part, 1,070 

feet of blocky- to massive-splitting dolomite and limestone with only 

sparse chert. The same three units are present in the Groom Range. 

Johnson and Hibbard (1957, p. 342-345), in preparing the first 

geologic map of the Test Site, recognized the basal shale as the 

Dunderberg Shale of the Eureka district but did not name the overlying limestone and dolomite. Barnes and Palmer (1961, p. C103) 

correlated the overlying rocks at the Test Site with the Windfall

249-926 O 67 3
G14 CONTRIBUTIONS TO STRATIGRAPHY

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FIGURE 5. Columnar section of Bonanza King Formation in 

Groom district.
CAMBRIAN, PRE AMBRIAN ROCKS, GROOM DISTRICT, NEVADA G15

REF

NO.' LITHOLOGY

37 Limestone and dolomite, light- to medium-gray thin bedded to laminated; silty limestone 

occurs as laminae and pockets and weathers medium to light brown, limestone 

"\ more abundant upward; forms steep slope.

36 Limestone, light-yellowish-gray to light-gray; beds average about 5 ft thick; very rare silty 

limestone; forms bluff.

imite and minor limestone: marked in outcrop by conspicuous light- to dark-gray 

stripes 2-10 ft wide; thin bedded to laminated, several zones of thin-bedded to 

lenticular black chert, scarce laminated silty dolomite; forms cliffs.

'34 Dolomite, siltv dolomite, silty limestone, and calcareous siltstone; silty rocks with minor 

chert predominant in top 55 ft and basal 35 ft; massive-weathering dark- to medium-gray mottled dolomite with some discontinuous cuspate silty laminae in central 

90ft.

33 Dolomite and limestone: dolomite light gray, laminated; limestone dark gray, laminated;

fnrrvic c^HHIa forms saddle.

32 Dolomite, dominantly very pale orange to light-gray, thin- to thick-bedded; contains discontinuous beds and lenses of dark-gray dolomite.

31 Dolomite, light- to dark-gray, laminated to thin-bedded; forms ledgy slope.

30 Dolomite, dark-gray; discontinuous laminae and mottling; weathered surface deeply 

\ pitted; forms saddle.

29 Limestone and dolomite: (limestone predominant) light-gray with discontinuous 1- to 5-ft 

dark- to medium-gray beds; dominantly thick bedded; forms cliff.

/28 Calcareous siltstone and siltv limestone, pale-yellowish-orange, thin-bedded; forms slope.

27 Limestone, dark-gray; irregular discontinuous Va-in. beds give mottled appearance; small 

Girvanella in a few beds; forms cliff.

/26 Limestone, medium-light gray; contains V*- to Va-in. vermicular dolomite blebs parallel to 

bedding; bedding indistinct except for faint medium-gray discontinuous 1- to 5-ft 

bands.

FIGTJBE 5. Continued
G16 CONTRIBUTIONS TO STRATIGRAPHY

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G18 CONTRIBUTIONS TO STRATIGRAPHY

Formation of the Eureka district (ISTolan and others, 1956, p. 19-22). 

Although not stated in the paper, their correlation was based on 

comparison of the Test Site rocks with those of the Nopah Range 

as well as the Eureka district. A marked similarity had been noted 

between the Dunderberg Shale and overlying flaggy-splitting silty 

and cherty limestone of the Test Site and similar strata at Eureka. 

These lower two lithologic types of the Test Site section are much less 

conspicuous in the Nopah Range, where they compose only 100 feet 

out of a total of 1,740 feet at the type locality of the Nopah Formation according to Hazzard (1937, fig. 3b). The upper lithology of 

the Test Site section was not found at Eureka but is conspicuous in 

the Nopah Range. Barnes and Palmer, in correlating the limestone 

and dolomite overlying the Dunderberg with the Windfall Formation, 

assigned the flaggy-splitting silty and cherty limestone to the Catlin 

Member of the Windfall as defined in the Eureka district; they 

designated the overlying blocky- to massive-splitting noncherty dolomite and limestone, a unit not present at Eureka, as the Smoky 

Member of the Windfall (Barnes and Palmer, 1961, p. C103; Barnes 

and Byers, 1961, p. C105).

Stratigraphic studies made during the past several years have done 

much to show where the three lithologic units of the Test Site area 

fit in the regional stratigraphy. The Dunderberg Shale is present 

in the area from the Eureka district to the southern Great Basin. 

The overlying flaggy-splitting silty and cherty limestone unit can be 

traced from the Groom district and the Test Site to the Nopah Range, 

although this unit and the Dunderberg thin notably southward. The 

Stratigraphic continuity of the silty and cherty very thin bedded 

limestone between the Test Site and Eureka has not yet been demonstrated, but the unit resembles the lithology of the Windfall Formation at Eureka. The upper unit, the massively outcropping carbonate 

unit, thickens southward from the Test Site area to comprise most 

of the section in the Nopah Range but is not present at Eureka. 

Thus all three lithologic units are common to the Groom-Test Site 

region and the Nopah Range but not to the Eureka district.

We, therefore, assign the post-Bonanza King pre-Pogonip rocks in 

the Groom district to the Nopah Formation and divide the Nopah 

of this area into the Dunderberg Shale, Halfpint, and Smoky Members, as we have done at the Nevada Test Site (Christiansen and 

Barnes, 1966). The Halfpint Member of the Nopah Formation, as 

defined by Christiansen and Barnes (1966), is the equivalent of the 

Catlin Member of the Windfall Formation described at the Test Site 

by Barnes and Byers (1961, p. C104). The Smoky Member of the 

Nopah was a reassignment by Christiansen and Barnes (1966) from
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G19

the Smoky Member of the Windfall Formation (Barnes and Byers, 

1961, p. 0105).

Total thickness of the JSTopah Formation in the Groom district 

(fig. 6) is about 2,035 feet. The Dunderberg Shale Member is about 

310 feet thick, the Half pint Member is 1,055 feet thick, and the Smoky 

Member is 670 feet thick.

The Dunderberg was named by Walcott (1908b, p. 184) as a 

replacement for Hamburg Shale because Hamburg was preempted. 

The Dunderberg Shale Member is composed of shale with very 

thin interbeds and concretions of limestone that are more abundant 

upward. The member is poorly exposed and forms a deep topographic saddle. Trilobite fragments are characteristically abundant 

in many of the limestones. The basal contact of the Dunderberg is 

sharp; the upper contact is gradational.

The Half pint Member in the Groom Range is composed of 1,055 feet 

of cliff-forming very thin bedded flaggy-splitting medium-gray limestone with intercalated laminae of clayey and silty limestone and 

very thin beds of chert. Argillaceous and silty partings are especially 

conspicuous in the lower part, and bedded chert, in the upper part. 

The clayey and silty material weathers to pale red or reddish brown. 

Beds in the lower 60 feet of the member are wavy to nodular. The 

base of the Half pint Member is gradational with the underlying Dunderberg Shale Member and is placed at the horizon where limestone 

becomes dominant over shale.

The Smoky Member at Groom is 670 feet thick and is composed 

chiefly of folocky- to massive-splitting medium- and light-gray limestone with, little to no chert and silty limestone. It forms rounded 

dark cliffs or bluffs with light-colored bands. Stromatolites 1-2 feet 

wide and 2-4 feet high are common in the Smoky. One 50-foot unit 

of pale-red-weathering very thin bedded limestone and silty limestone is present about 200 feet above the base of the member in the 

Groom district. The Halfpint-Smoky contact is fairly sharp. It is 

marked by the change from abundant thin discontinuous beds and 

lenses of dusky-brown-weathering chert in the Halfpint to relatively 

few scattered nodules of chert in the Smoky. The contact of the 

Smoky with the overlying Goodwin Limestone of the Pogonip Group 

is gradational through about 50 feet. In general the base of the 

Goodwin is marked by abundant nodules and thin lenses of duskybrown-weathering chert in yellowish-brown-weathering very thin 

bedded to thin-bedded limestone and silty limestone.

The JSTopah is considered to be of Late Cambrian age. 

Dunderbergia-zone fossils of early Late Cambrian Dresbach age are 

found at several levels in the Dunderberg Shale Member at Groom
G20 CONTRIBUTIONS TO STRATIGRAPHY

SYSTEM

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REF. 

NO.

43

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39

38

FIGURE 6. Columnar section of Nopah Formation in 

Groom district.

and in the Half pint Eange (Palmer, 1965). Palmer (1965) also 

has identified trilobites from the basal part of the Halfpint Member 

as being from the Elvinia zone of Franconia age. Other trilobites 

from 150 to 350 feet above the base of the Halfpint are from the late 

Franconian PtycJiaspis-Prosaukia zone (A. E. Palmer, written 

commun., 1960). Yet others from about 250 feet below the top of 

the Smoky Member in the Striped Hills (fig. 1) were identified by 

Palmer (written commun., 1964) as a typical Late Cambrian assemblage of Trempealeau age. E. J. Eoss (Byers and others, 1961, 

p. C109) has identified Early Ordovician fossils from the Good win 

Limestone about 200 feet above the Nopah in the Halfpint Eange.

CORRELATION

This section of the report compares the stratigraphic assignments, 

lithologies, thicknesses, and ages of Cambrian and Precambrian formations in the Groom district with those of units in the surrounding 

region and reviews associated problems of nomenclature. Figure 7 

shows variations in thickness of major stratigraphic units in the region 

around the Nevada Test Site and the Groom Eange. As an aid in
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G21

REF. 

NO. LITHOLOGY

44 Limestone and silty limestone, pale-yellowish-gray to medium-light-gray; very thin bedded 

to thin-bedded chert nodules weathering dusky brown; basal beds form bench.

43 Limestone, dominantly medium- to dark-gray, thick-bedded, blocky- to massive-splitting; 

20- to 50-ft light-gray bands; abundant stromatolites in upper 50 ft; some nodular 

chert in upper 25 ft; forms cliffs or steep slopes.

42 Limestone, silty, very thin bedded; weathers pale red; forms bench or saddle.

41 Limestone, dominantly medium-gray, thick-bedded, blocky- to massive-splitting; a few 20- 

ft light-gray bands; forms cliff.

40 Limestone, medium-gray; very thin bedded to thin-bedded with partings of pinkish-gray 

argillaceous limestone; thin-bedded irregular and discontinuous dark-gray chert 

abundant; unit forms cliff.

(39 Limestone and siltstone; limestone medium gray; abundant trilobite debris; wavy 1- to 

3-in. beds. Siltstone calcareous; weathers brown; irregular discontinuous very thin 

beds and partings between limestone beds. Unit forms bluff.

38 Shale and limestone: shale light olive gray to reddish brown, notably fissile; weathers to 

tiny flakes. Limestone medium gray; abundant trilobite fragments; in 1- to 3-in. 

nodular beds to flat lenticular concretions, increasing in abundance upward. Unit 

forms deep saddle.

FIGUBE 6. Continued

comparison of thickness changes, the measured sections are projected 

to two planes, whose traces trend east-southeast, approximately normal 

to regional thickness trends (fig. 1). The datum for figure 7 is the 

top of the Carrara Formation. This lithologic contact was selected 

as approximating a f aunal horizon; the Glossopl&wra zone, wherever 

recognized in this region, includes the uppermost part of the Carrara 

Formation.

The four formations, Johnnie through Zabriskie, in the lower part 

of the Precambrian and Cambrian section are recognizable throughout a region that extends at least 100 miles south and west of the 

Groom district (fig. 1). Stewart (1966) correlated these formations 

and their distinctive members through the Spring Mountains-Death 

Valley region (including the Nopah Range, the Spring Mountains, 

and the Last Chance Range); he demonstrated that the units thicken, 

become progressively finer grained, and include higher proportions of 

carbonate strata northwestward across the region. They merge 

northwestward in the Inyo and White Mountains and surrounding 

parts of California and Nevada with formations that represent a 

northwestern facies characterized by siltstones, carbonates, and rela-
G22 CONTRIBUTIONS TO STRATIGRAPHY
Bare Mountain

(Daylight through Nopah modified from 

Cornwall and Klemhampl, 1961, 19G4; 

Stirling measured by Stewart, 1966)

Striped Hills

(Measured by M W. Reynolds and Narley Barnes)

Northwest

Spring Mountains

(Stewart, 1966; modified from Nolan, 1929)

Northern 

Resting Spring Range

<Ste"art ' 1966) Nopah Range

(Noonday through Zabriskie, Stewart, 1966; Carrara through Nopah modified from Hazzard, 1937)

 8 miles-

,

Specter Range

(Modified after eurchfiel, 1964)

Stifling Quartzite .Location of sections shown in figure 1. Sections projected to east-southeast-trending line that is approximately normal to re- gional thickness trend. Datum is f ps, rr,, rn TTiftrmsitirm Rp- Ot ^arfara * OrmaUOn. lie- *The Corkscrew Quartzite and Daylight Formation are names used by Cornwall and KleinhampI, (1964) for strata mapped by other -.- . . . . M««H 

authors in adjacent quadrangles as Zabriskie Quartzite and Wood gional Subdivision of Stirling

canyon Formation Quartzite and Wood Canyon Formation taken, from Stewart (19r86).

FIGURE 7. Correlation of Cambrian and some Precambrlan formations in southern Great Basin.

o

»

O
G24 CONTRIBUTIONS TO STRATIGRAPHY

tively little quartzite and sandstone. Stewart and Barnes (1966) correlated units in the lower part of the Desert Range section with the 

units recognized by Stewart in the Spring Mountains-Death Valley 

region. The Groom district, in turn, can be correlated through the 

Desert Range section with the units to the southwest (fig. 7).

The Rainstorm Member at the top of the Johnnie Formation is present through much of the region (Barnes and others, 1965; Stewart, 

1966). The fine-grained sandstones, siltstones, silty limestones, and 

thin oolitic dolomite beds of the Rainstorm contrast with the quartzite, 

phyllitic siltstone, and cherty dolomite of the main part of the formation below.

Members A, B, C, and E of the Stirling Quartzite in the Groom 

district are also recognizable for 100 miles to the south and west. They 

correlate with members A, B, C, and E of the Stirling in the Desert 

Range (Stewart and Barnes, 1966) and in the Spring MountainsDeath Valley region (Stewart, 1966). Stewart's member D of the 

Spring Mountains-Death Valley region is predominantly dolomite 

that tongues out southeastward into the overlying quartzite of member E. Stewart and Barnes indicate that member D does not extend 

as far eastward as the Desert Range, and there is no lithologic equivalent of this dolomite in the Groom District. Member E is virtually 

pure light-colored quartzite in the Nopah Range and Spring Mountains, but northward at Bare Mountain (Stewart, 1966, fig. 2) its lower 

part includes interbedded siltstone and minor limestone. The three 

lithologic subdivisions of member E at Groom correspond to three 

very similar subdivisions in the Desert Range: unit 1 of member E 

at Groom is equivalent to units 30 and 31 in the Desert Range (Stewart 

and Barnes, 1966), and units 2 and 3 of member E at Groom, are 

equivalent, respectively, to units 32 and 33 in the Desert Range. The 

total thickness of the Stirling Quartzite in the Groom district is uncertain, but regionally the formation thickens toward the northwest

(% 7).

Stewart (1966) divided the Wood Canyon in the Spring MountainsDeath Valley region into lower, middle, and upper members that correspond to the three parts of the formation noted in the description 

at the type locality (Nolan, 1929, p. 464). The same three members 

are present in the Desert Range, and in the Groom district. Figure 

7 shows that the Wood Canyon thickens northwestward. As previously noted, the oldest trilobites found throughout the region occur 

in the upper half of the Wood Canyon Formation and equivalent units.

The Zabriskie Quartzite has been recognized in recent years to be 

a widespread unit in the region west and south of the Groom Range. 

Stewart correlates it throughout the Spring Mountains-Death Valley
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G25

region and shows that it thins southeastward. The corresponding 

strata are more than 1,000 feet thick at Bare Mountain and only about 

20 feet thick in the Spring Mountains. Similarly, the formation thins 

from 220 feet in the Groom Eange to only 6 feet in the Desert Kange.

East of the Groom district, at Pioche, for example (Westgate and 

Knopf, 1932, p. 6-8; Wheeler and Lemmon, 1939, p. 33-34; Merriam, 

1964, p. 9-13), the basal clastic part of the section is generally referred 

to the Cambrian Prospect Mountain Quartzite. Tschanz and Pampeyan (1961) mapped the Prospect Mountain Quartzite throughout 

Lincoln County, including the Groom Kange, the Papoose Eange, and 

the Desert Range, although they separated the Johnnie Formation 

from the Prospect Mountain at the base of the section in the Desert 

Range. The Prospect Mountain commonly has been regarded as 

equivalent to the Stirling Quartzite of the Spring Mountains-Death 

Valey region (Wheeler, 1948, p. 19; Longwell, 1952, p. 212); but the 

present study in the Groom district, mapping in the Halfpint and 

Papoose Ranges, and Stewart and Barnes' work in the Desert Range 

show that the Prospect Mountain as previously used in this area included at least parts of the Zabriskie, Wood Canyon, Stirling, and 

Johnnie as known in the region to the southwest. These four formations probably bear a corresponding relation to the Prospect Mountain Quartzite of the Pioche district (table 2). Upper beds of the 

Prospect Mountain at Pioche contain abundant Scolithus (Merriam, 

1964, p. 11) and are probably correlative with the Zabriskie Quartzite. Lower Cambrian shale beds immediately above the Zabriskie 

Quartzite at Groom, characterized by the trilobite genus Bristolia, 

are definitely correlative with the basal part of the Pioche Shale in 

the Pioche district (A. R. Palmer, written commun., 1961).

In the Groom district Humphrey (1945, p. 15-16) placed virtually 

all the basal clastic rocks in the Prospect Mountain Quartzite (table 1), 

and measured a thickness of 7,855 feet for the formation. It is apparent, however, that the rocks can be correlated with well-established 

formations and their members throughout most of the southwestern 

Great Basin. Total thickness of this part of the section is greater 

than 5,735 feet, but almost certainly not much more than 6,300 feet.

In the Halfpint Range, Barnes, Christiansen, and Byers (1962, p. 

D27-D30) used the name Carrara Formation for the entire sequence 

of shale, siltstone, and limestone between the dominantly quartzitesiltstone sequence below and the dominantly limestone-dolomite sequence above in preference to the usage of the nomenclature of either 

Humphrey or Johnson and Hibbard. Humphrey (1945, p. 16-18) 

attempted to correlate the Groom Range strata with the classic section 

at Pioche, Nev., about 75 miles northeast of Groom; and Johnson and
G26 CONTRIBUTIONS TO STRATIGRAPHY

TABLE 2. Comparison of stratigra/phic units of Groom and Pioche districts

Groom district (this report)

Pogonip Group, Goodwin Limestone

Nopah Formation

Bonanza Kig Formation

Carrara Formation

Banded Mountain 

Member

Papoose Lake Member

i

Unit D

Units B and C

Unit A

UnitC

Unit B

Unit A

Member G

Jangle Limestone Member

Members A through E

Zabriskie Quartzite 

and older clastic formations

Pioche district (Merriam, 1964)

Mendha Formation

Units 7 through 13

Meadow Valley Member

Condor Member

Step Ridge Member

Burnt Canyon Member

Burrows Member 

and 

Peasley Member

£t

£S

r

ro 

Q.

s_0

1

Highland Peak Formtion

Chisholm Shale

Lyndon Limestone

Pioche Shale

Prospect Mountain Quartzite

Hibbard (1957, p. 337-339) applied Humphrey's correlations to the 

rocks of the Half pint Kange in the Nevada Test Site (table 1). In the 

Pioche area the section equivalent to the Carrara Formation is divided 

into three formations: in ascending order, the Pioche Shale (Walcott, 

1908a, p. 11-12), the Lyndon Limestone (Westgate and Knopf, 1927, 

p. 820; 1932, p. 10), and the Chisholm Shale (Walcott, 1916, p. 409- 

410). Fossil evidence from the Groom district shows that the Lyndon 

Limestone of Humphrey, member D of the Carrara in this report, is 

older than the Lyndon in the Pioche district and correlates with beds 

in the upper part of the Pioche Shale (A. K. Palmer, written commun., 

1961). Barnes and Palmer (1961) showed that the Lyndon Limestone 

of Johnson and Hibbard in the Halfpint Kange also is correlative with 

the upper part of the Pioche Shale. Barnes and Palmer, in turn,
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G27

regarded the basal part of the Lyndon Limestone of Johnson and 

Hibbard as correlative with the Chambless Limestone, a Lower Cambrian formation recognized in the Providence Mountains of southeastern California. They accordingly divided the section in the Halfpint Eange into the Providence Mountains units of Hazzard (1954, 

p. 30-32) : in ascending order, the Latham Shale, the Chambless Limestone, and the Cadiz Formation. After field examination of many 

sections in the southern Great Basin, Palmer (written commun., 1961) 

found that these correlations were also wrong. Until more data make 

certain the regional correlation of members within the Carrara, we 

prefer to limit our regional correlation to the more inclusive unit, the 

Carrara Formation.

The Jangle Limestone Member of the Carrara in the Groom-Half - 

pint area is correlative with the Lyndon Limestone in the Pioche district (table 2). The Jangle is lithologically much like the Lyndon 

.and probably is the same unit. Humphrey (1945, p. 19) incorrectly 

correlated the Jangle in the Groom district with the Peasley Limestone 

of Wheeler (1940, p. 17-27) at Pioche, but the Peasley is younger and 

generally does not have the characteristic silty pink to brown mottling 

and discontinuous lamination of the Jangle and the Lyndon.

In the Belted Kange, 25 miles northwest of Groom (fig. 1), a significant change of f acies is apparent in strata equivalent to the upper part 

of the Carrara. J. H. Stewart and C. L. Rogers (written commun., 

1964) measured 1,577 feet of siltstone and subordinate limestone there 

roughly comparable to members A through D of the Carrara in the 

Groom-Halfpint area, but above that they found very thin bedded 

limestone and siltstone in a faulted and partly covered section estimated to be at least 1,300 feet thick. The lithology of this upper 

1,300 feet is unlike the upper part of the Carrara or basal part of the 

Bonanza King but is very similar to the limestone sequence in the 

upper part of the Emigrant Formation of Esmeralda County, Nev., 

and the surrounding region (Albers and Stewart, 1962, p. D27).

Division of the Bonanza King Formation into two members in the 

Groom and Halfpint Ranges follows the practice of other workers in 

the southern Great Basin. Palmer and Hazzard (1956) clarified the 

relations between these members in the Providence Mountains of 

southeastern California, in the Nopah Range, and in the Goodsprings 

district; they showed that the Bonanza King can be divided in all 

three areas into upper and lower parts separated by a sandy or argillaceous unit. This sandy-argillaceous zone at the base of the upper member was shown by Palmer (1956, p. 672-674), to have a 

widespread distribution in the southern Great Basin. Little detailed 

stratigraphic work beyond recognition of lower and upper members
G28 CONTRIBUTIONS TO STRATIGRAPHY

has been published for the Bonanza King Formation in the region 

southwest of the Groom and Halfpint Ranges. Our own regional 

studies now in progress suggest that several units within the Bonanza 

King are wide ranging across the region.

Strata largely equivalent to the Bonanza King Formation in areas 

east of the Groom district are placed in the Highland Peak Formation as defined and mapped in the Bristol and Highland Eanges and 

the Pioche district (Westgate and Knopf, 1927, 1932). The Highland Peak Formation has been divided into members and described 

in several papers on the stratigraphy of the region around Pioche 

(Wheeler and Lemmon, 1939, p. 37-42; Wheeler, 1940, p. 17-33; 1948, 

p. 33-43; Merriam, 1964, p. 33-50). Humphrey (1945, p. 19-22) correlated rocks in the Groom district above the shaly part of the Carrara 

Formation with the Highland Peak and related units (table 1).

As the name Highland Peak has priority over the name Bonanza 

King, the question of which name is preferable for the strata in the 

Groom area should be answered. We have used the name Bonanza 

King because the Bonanza King Formation as used widely in the 

southern Great Basin is correlative with all the strata at Groom between the top of the Carrara Formation and the base of the Dunderberg Shale Member, but the Highland Peak Formation in the Pioche 

district is not. Palmer (1956, p. 673) indicated that the fossiliferous 

basal part of the Mendha Formation, which overlies the Highland 

Peak in its type locality, is not correlative with the Dunderberg, 

which overlies the Bonanza King at Groom. Instead, the basal beds 

of the Mendha form an older stratigraphic unit not conspicuously represented farther southwest. A shaly zone faunally and lithologically 

equivalent to the Dunderberg occurs in the Pioche area some distance 

above the base of the Mendha (Merriam, 1964, p. 52). Thus the 

Bonanza King Formation includes strata correlative with the entire 

Highland Peak plus the lower part of the Mendha. It seems preferable to use the Highland Peak terminology only in the region where 

the formational contacts generally accepted for the unit are clearly 

recognizable, and to regard the equivalent rocks in the Groom district 

as belonging to the Bonanza King.

The basal parts of the Bonanza King and Highland Peak Formations, corresponding to unit A of the Papoose Lake Member in the 

Groom section, are notably similar throughout the region (for example, see Hazzard and Mason, 1936, p. 235; Hazzard, 1937, p. 277; 

Burchfiel, 1964, p. 48; Merriam, 1964, p. 35-36). These parts are 

generally composed of dark- to medium-gray limestone or dolomite 

that forms massive cliffs but has a somewhat inconspicuous thin bedding of discontinuous laminae or alined nodes that give a mottled
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G29

appearance to the rock. The mottling is generally somewhat lighter 

gray and more coarse grained than the bulk of the rock. This lithologic type makes up most of unit A of the Papoose Lake Member of 

the Bonanza King in the Groom and Half pint Ranges and most of 

Hazzard's (1937, p. 277) unit 6A of the Bonanza King in the Nopah 

Range; it is characteristic of the Peasley Member of the Highland 

Peak Formation in the Pioche district (Merriam, 1964, p. 35-36).

In the Half pint and Groom Ranges, in the Nopah Range (Hazzard, 

1937, p. 316), and elsewhere in the region one or more conspicuous 

light-colored zones occur within unit A and equivalent rocks, commonly near the top. Thickness, continuity, and detailed features of 

these light-colored zones vary, but faint to conspicuous remnants of 

darker and finer grained strata within them indicate that the zones 

were formed by alteration of the darker material. This light-colored 

rock type is similar in some respects to the Burrows Member, which 

occupies a similar stratigraphic position in the Highland Peak Formation of the Pioche district (Merriam, 1964, p. 36-41). Merriam 

notes that the thickness of the Burrows and the character of its boundaries are highly variable in the Pioche region; this variability is also 

displayed by the light-colored zones in unit A of the Papoose Lake 

Member of the Bonanza Kng Formation. The total thickness of 

unit A is comparable over a large region, but the individual thicknesses of the Peasley and Burrows type lithologies are not. Unit A, 

therefore, is probably the stratigraphic equivalent of both the Peasley 

and Burrows at Pioche (table 2).

Siliceous clastic material like that characteristic of unit B of the 

Papoose Lake Member at Groom appears to be somewhat more common regionally in the lower than in the upper part of the Bonanza 

King. Hazzard's Nopah Range section (following Palmer and Hazzard, 1956) has several siliceous detrital zones in the lower part of 

the Bonanza King, as do many other sections in the region southwest 

of the Nevada Test Site. In the Half pint and Groom Range sections, 

however, unit B is the only zone of comparable type in the lower part 

of the Bonanza King. Stratigraphic relations indicate (table 2) that 

unit B is approximately equivalent to the Burnt Canyon Member of 

the Highland Peak Formation in the Pioche district (Merriam, 1964, 

p. 41-43). In both areas this part of the section is characteristically 

thin-bedded to laminated limestone with nodes and partings of red-, 

yellow-, or brown-weathering argillaceous and silty limestone, occurring generally 400-600 feet above the base of the formation. In the 

Pioche district the Burnt Canyon Member is fossiliferous, containing 

several undescribed trilobite species of Middle Cambrian age (Merriam, 1964, p. 43). The only fossil reported from unit B in the Groom
G30 CONTRIBUTIONS TO STRATIGRAPHY

or Halfpint Ranges is the "CoelaspisCl}" reported by Humphrey 

(1945, p. 21) and by Wheeler (1948, p. 38, 50). Wheeler (1948, p. 38, 

51) also reported "Coelaspis sp." from the Burnt Canyon Member in 

the Pioche district.

Unit C of the Papoose Lake Member, bracketed by the only significant silty or argillaceous units in the Bonanza King of the Groom 

Range, is correlative (table 2) with the Step Ridge Member of the 

Highland Peak Formation near Pioche (Merriam, 1964, p. 43-45), 

and the lithologies of the corresponding intervals in the two areas are 

similar. Because a single siliceous detrital unit is not distinguishable 

in the lower part of the Bonanza King farther southwest, similarly 

direct correspondence to sections in the southwest is less obvious.

The silty or sandy zone at the base of the Banded Mountain Member of the Bonanza King Formation is present regionally (Palmer, 

1956, p. 672-674). Palmer showed that unit F of the Highland Peak 

Formation as described in the Pioche region by Wheeler and Lemmon 

(1939, p. 47), the Condor Member of Merriam (1964, p. 45-46), is 

equivalent to the regional clastic zone at the base of the Banded Mountain Member of the Bonanza King (table 2). In the Groom section 

this clastic zone is represented by unit A of the Banded Mountain 

Member although the upper contacts of our unit A and Merriam's 

Condor Member differ slightly.

Not enough detail is known about units B, C, and D of the Banded 

Mountain Member in the Groom district to correlate them with the 

equivalent rocks in the Pioche region. Unit B at Groom has not been 

subdivided on a scale comparable to the remainder of the formation. 

This entire unit, 1,600 feet thick, is characterized by its conspicuously 

striped appearance when viewed from a distance. This striped 

appearance has also been described in equivalent strata of the Nopah 

Range (Hazzard, 1937, p. 319) and at Bare Mountain (Cornwall and 

Kleinhampl, 1961). In contrast, units C and D of the Banded Mountain Member form wider color bands at the top of the Bonanza King. 

Similar bands were noted by Hazzard and by Cornwall and Kleinhampl in other parts of the region. In the region southwest of the 

Test Site, a dark-gray unit generally lies between units similar to the 

striped unit B and the buff unit C of the Groom and Halfpint Ranges. 

At Pioche the Highland Peak Formation above the Condor Member 

is divided into 8 (Merriam, 1964, p. 46-50) or 11 (Wheeler and Lemmon, 1939, p. 45-47) units. We do not yet know enough about the 

equivalent rocks in the Groom Range to correlate them individually 

with the divisions in the Pioche district (table 2). Units B and C 

of the Banded Mountain Member at Groom appear to correlate with 

the Highland Peak Formation of Reso (1963, p. 904, pi. 2) in the 

Pahranagat Range (fig. 1). Unit D appears to be the lithologic
CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G31

equivalent of the lower member of the Dunderberg Formation of Reso 

(1963, p. 904, pi. 2).

The Racetrack Dolomite (McAllister, 1952, p. 8-9) of the northern 

Panamint Range is probably correlative with the uppermost part of 

the Papoose Lake Member and the entire Banded Mountain Member 

of the Bonanza King Formation.

Reasons for changing previous nomenclature for the Upper Cambrian rocks above the Bonanza King Formation in the Nevada Test 

Site region (Christiansen and Barnes, 1966) have already been given. 

The Nopah Formation, as used in this paper for the Groom district 

and Nevada Test Site, is directly correlative with the Nopah as generally mapped in areas southwest of Groom (McAllister, 1952; Cornwall and Kleinhampl, 1961; Yochelson and others, 1965, p. B75). 

Christiansen and Barnes (1966) have noted, however, that the top of 

the Nopah Formation as generally mapped in the region varies slightly 

from the description of the Nopah at the type section. Hazzard 

(1937, p. 276) tentatively placed the top of the Nopah at the base of a 

"sandy and clayey, locally cross-bedded dolomite" (unit 9A) that he 

referred to as the basal "Pogonip( ?) dolomite." Subsequent detailed 

mapping and regional work by McAllister (1952, p. 10-11), by R. J. 

Ross (written commun., 1965), and by us has shown that this sandy 

and clayey dolomite is correlative with a widespread silty unit in the 

Goodwin Limestone some distance above the base of the Pogonip 

Group. Regionally the base of the Pogonip corresponds to an upward 

change from massive-splitting relatively chert-free beds in the Smoky 

Member of the Nopah Formation to thin-bedded partly silty beds 

with abundant chert in the basal Goodwin Limestone. There is generally also a change in weathered color from medium gray below to 

lighter, more yellowish gray above this contact. Rocks above and 

below the contact may be either limestone or dolomite. One of us 

(Barnes) remeasured the type section of the Nopah and found that the 

base of the Pogonip, as recognized regionally, is about 500 feet lower 

than the tentative boundary proposed by Hazzard; the Nopah Formation in the Nopah Range is, therefore, about 1,270 feet thick rather 

than 1,740 feet.

The Nopah Formation of the Groom Range is correlative with only 

the middle part of the Mendha Formation of the Pioche region. The 

Mendha is not yet well known stratigraphically, but its base is correlative with rocks in unit D of the Bonanza King Formation and its top 

is correlative with part of the Lower Ordovician Goodwin Limestone 

(Merriam, 1964, p. 52). In the Pahranagat Range, 20 miles east of 

Groom, the upper member of the Dunderberg Formation and members 

A, B, and C of the Desert Valley Formation (Reso, 1963, p. 904-905, 

pi. 2) are probably correlative with the Nopah of the Groom Range.
G32 CONTRIBUTIONS TO STRATIGRAPHY

The most striking changes in the Nopah Formation in the region 

shown on figure 7 are the simultaneous northward thickening of the 

Dunderberg Shale and Halfpint Members and the northward thinning of the Smoky Member. The Smoky Member, which composes the 

bulk of the Nopah at its type section, thins from about 1,135 feet in 

the Nopah Kange to 670 feet at Groom. The Dunderberg Shale 

Member thickens from 40 feet in the Nopah Kange to 310 feet in the 

Groom Kange. The Halfpint Member thickens from 95 feet in the 

northern Nopah Range to 1,055 feet at Groom. Both the Dunderberg 

and Halfpint Members of the Nopah are represented in Hazzard's 

(1937, p. 276) unit 8A of the type locality but are more fully exposed 

on the next ridge to the north, where their total thickness is 135 feet 

instead of 100 feet (Christiansen and Barnes, 1966). Burchfiel (1964, 

p. 45) included both members in the 200 feet of his Dunderberg Shale 

in the Specter Range. The Lead Gulch Formation of the Inyo Mountains likewise is equivalent to the combined Dunderberg and Halfpint 

(Ross, 1963, p. B74-B77). The overlying Tamarack Canyon Dolomite 

is at least largely correlative with the Smoky Member of the Nopah 

Formation (Ross, 1963, p. B77-B78).

Although rocks now assigned to the Halfpint and Smoky Members 

of the Nopah were formerly included in the Windfall Formation at 

the Nevada Test Site (Barnes and Byers, 1961), only the Halfpint is 

lithologically similar to the Windfall of the Eureka district and surrounding areas. Until more is known about the Nopah and Windfall 

Formations between the Groom and Eureka districts, the following is 

presented only as a hypothesis for consideration in future work: It 

seems likely that the Halfpint Member of the Nopah Formation thickens northward to become the Windfall Formation of central Nevada. 

This lithology may, therefore, be a facies of the Nopah Formation; the 

principal facies in the southern Great Basin is the Smoky Member.

In summary, the stratigraphic nomenclature of the Spring 

Mountains and Nopah Range fits the Precambrian and Cambrian rocks 

of the Groom Range, but the nomenclature of the Pioche district is 

less applicable. Among the reasons for this better fit are a greater 

number of well-studied sections, and less marked facies changes between Groom and the Nopah Range than between Groom and the 

Pioche district.

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CAMBRIAN, PRECAMBRIAN ROCKS, GROOM DISTRICT, NEVADA G33

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G34 CONTRIBUTIONS TO STRATIGRAPHY

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o