1.7*

The Bates Mountain Tuff *' 

in Northern Nye County, 

Nevada

By K. A. SARGENT and E. H. McKEE

CONTRIBUTIONS TO STRATIGRAPHY 

GEOLOGICAL SURVEY BULLETIN 1294-E
UNITED STATES DEPARTMENT OF THE INTERIOR 

WALTER J. HICKEL, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

U.S. GOVERNMENT PRINTING OFFICE, WASHINGTON : 1969

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

Washington, D.C. 20402 - Price 10 cents
CONTENTS

Abstract_______________

Introduction___________

Lithology and petrography_ 

Distribution and thickness. 

Remanent magnetism___.

References cited.

Page

El

1

3

4

5

5

12

ILLUSTRATIONS

FIGURE 1. Generalized map showing known distribution, areas of outcrop, 

and lines of sections of the Bates Mountain Tuff________

2. Columnar sections from Clipper Canyon section in northern 

Toquima Range to Crested Wheat section hi Hot Creek 

Range_ _____________________________ ____

3. Columnar sections from Butler Creek in central Monitor Range 

to Antelope Spring in southern Monitor Range_______ -

. 4. Approximate distribution of units 1-5 of the Bates Mountain 

Tuff in northern Nye County, Nev_________--___ _____

TABLES

Page

E2

10

TABLE 1. Analysis of black vitrophyre at base of densely welded part of 

unit 2, Bates Mountain Tuff, Clipper Canyon, Lander County, 

Nev______________________________________________

2. Average phenocryst values of five cooling units of the Bates 

Mountain Tuff at Clipper Canyon, northern Toquima Range.

3. Phenocryst mineralogy of Bates Mountain Tuff and older 

tuffs at section localities shown in figure 2_________________

4. Phenocryst mineralogy of Bates Mountain Tuff, younger tuffs, 

and certain older tuffs at section localities shown in figure 3__

5. Remanent-magnetism directions in samples collected from unit 

5 of the Bates Mountain Tuff-.----------.-.______ 

6. K-Ar age data on Bates Mountain Tuff and three underlying 

welded tuffs from Clipper Canyon section, Toquima Range, 

and from the Crested Wheat section, northern Hot Creek 

Range _____________________________________________

m

Page

E3

11

11

CONTRIBUTIONS TO STRATIGRAPHY

THE BATES MOUNTAIN TUFF IN NORTHERN 

NYE COUNTY, NEVADA

By K. A. SARGENT and E. H. McKEE

ABSTRACT

The Bates Mountain Tuff, a widespread Miocene (K-Ar age about 22-24 

million years) formation in central Nevada, crops out across a region of more 

than 1,900 square miles in northern Nye County, Nev. In the northwestern part 

of this region the formation comprises five cooling units, but only the upper 

two units can be traced eastward into east-central Nye County and only the 

upper unit can be found to the south in north-central Nye County.

INTRODUCTION

The Bates Mountain Tuff was named by Stewart and McKee (1968) 

for a lithologically distinctive sequence of Tertiary rhyolitic ash-flow 

tuffs that is well exposed in the vicinity of Bates Mountain in the 

Simpson Park Mountains, southern Lander County, Nev. To the south 

in the Spencer Hot Springs quadrangle, the formation, as mapped by 

McKee (1968), contains all the ash-flow units recognized at Bates 

Mountain as well as additional upper and lower units. This usage is 

retained in this paper.

The general distribution of the Bates Mountain Tuff in central 

Nevada and its stratigraphic relationship to other Tertiary units was 

outlined by McKee (1969). The Bates Mountain Tuff in northern 

Nye County and in the southernmost parts of Lander and Eureka 

Counties (fig. 1) is described in the present paper. The Bates Mountain Tuff is commonly the youngest ash-flow sequence in the northern 

part of the region, but to the south and east, in Nye County, it is 

locally overlain and underlain by tuffs and lavas from other volcanic 

centers. It is in this south and east area that the tuff is most useful 

as a unit for correlation. Like most widespread ash-flow tuffs, the 

Bates Mountain unconformably overlies various older tuffs, lavas, 

and sedimentary rocks.

El
E2 CONTRIBUTIONS TO STRATIGRAPHY

117°00'

39 00'

38° 

30'

Clipper CanydVi 

 _ section

Potts 

Butler Creek: 

sections.

Crested Wheat 

^section

Diamond

King

Hill

Southern 5 

' /Little Fish Lake 

7 section -

Limit of distribution of 

Bates Mountain Tuff

Antelope Spring 

ection '-

Fourmile Spring | 

section §

10 15 20 MILES

FIGURE 1. Generalized map showing known distribution, areas of outcrop 

(stippled), and lines of sections of the Bates Mountain Tuff. Named sections 

are referred to in figures 2 and 3 and in the text
BATES MOUNTAIN TUFF, NYE COUNTY, NEVADA 

LITHOLOGY AND PETROGRAPHY

In general, the Bates Mountain Tuff is characterized by phenocrystpoor ash flows that are grayish pink to buff where partly welded to 

nonwelded and pink to dark reddish brown where densely welded. 

Most flows contain less than 10 percent phenocrysts that consist dominantly of alkali feldspar (sanidine) but include less abundant plagioclase, quartz, accessory biotite, hornblende, clinopyroxene, orthopyroxene, and opaque oxides, and trace amounts of zircon, allanite, and 

apatite. All the phenocrysts are less than 3 mm in diameter, and commonly quartz is deeply embayed. The groundmass is shard rich, and 

most of it contains only sparse foreign lithic fragments of densely 

welded rhyolitic to quartz latitic tuff and (or) lava of intermediate 

composition.

The upper two cooling units of the Bates Mountain Tuff (Nos. 4 

and 5) are especially distinctive. Both are characterized by dominant 

phenocrysts of sanidine, less common quartz, and sparse plagioclase 

relative to units 1, 2, and 3. In Nye County they appear to be more 

widespread than the lower three cooling units (1, 2, and 3), and 

the lower of the two (unit 4) is distinctive because of its ubiquitous 

gas cavities; this unit is informally called the "swiss cheese." Where 

the flows become punky owing to vapor-phase crystallization, prominent very light gray pumice, 0.5-2 inches long, is common in a brickred groundmass.

Phenocryst mineralogy in cooling units 1, 2, and 3 indicates that 

units 1, and 2 are rhyolitic and that the overlying unit (unit 3) may 

be quartz latitic. The exact contact between cooling units 2 and 

3 is difficult to find.

The vitrophyre from unit 2, as suggested by a whole-rock analysis 

(table 1), is a typical rhyolite.

TABLE 1. Analysis of black vitrophyre at base of densely welded part of unit %>

Bates Mountain Tuff, Clipper Canyon, Lander County, Nev. 

[Whole-rock analysis by U.S. Geol. Survey Lab., Leonard Shapiro, project leader]

Oxide

Si02 - ______ - - __

A12 03 ___ - ________

FeaOs

FeO.__. _____________

MgO.__. _____________

CaO________________.

Na2 0 _ _____________

K2 0._ __ ____________

Percent

____ 73.6

_.__ 12.9

.___ .85

-.__ .32

____ . 16

____ .50

q f|

____ 4.8

Oxide

H.O- _--_- 

H.O+. _____________

Ti02 _____ __-___- 

P.O. _ 

MnO _----_--_----

C02 ______________

Percent

_____ .29

_____ 2.8

___ . 11

___ .00

_____ .06

_____ <. 05

___ 99.44
E4 CONTRIBUTIONS TO STRATIGRAPHY

TABLE 2. Average phenocryst values, in volume percent, of five cooling units of the 

Bates Mountain Tuff at Clipper Canyon, northern Toquima Range

[Tr., trace]

Cooling unit

Total phenocrysts_ ___________

Quartz___- ______ ________

Alkali feldspar (sanidine) _ _ _ _ .

Plagioclase. _ __ _ __________

Biotite. ______ ____ ___ ____

Hornblende.- __ _ __ ___

Pyroxene--.. _________ ____ _ Opaque oxides ______ _______

Altered mafic minerals. ____ _.

Total__ ______ __

i

____ 10

._ <1

55

35

.___ <1

Tr

Tr.

3

._._ 6

99 +

2

5

30 

44 

20 

0 

Tr. 

2 

3 

1

100

3

7.5

24 

17 

50 

1 

Tr. 

Tr. 

6 

2

100

4

2.7

<1

88 

1

<1

0 

Tr.

4 

6

99 +

5

5

23 

60 

11 

4 

0 

Tr. 

1 

1

100

Table 2 summarizes the petrography of the five cooling units of the 

Bates Mountain Tuff. The phenocryst values given are averages fro'm 

modal analyses of specimens taken at Clipper Canyon in the northern 

Toquima Range in the northwestern part of the region. The values are 

distinctive for the cooling units throughout their extent.

DISTRIBUTION AND THICKNESS

The Bates Mountain Tuff is known (fig. 1) in northern Nye County 

only north of U.S. Highway 6 and east of Nevada Highway 8A, 

which runs along the west side of the Toquima Eange. The tuff is 

generally found in the stratigraphically high part of Tertiary fault 

blocks, although in many places it may have been eroded away. In 

the southern part of northern Nye County the Bates Mountain Tuff is 

seen only where erosion of paleotopographic lows has exposed the tuff 

under younger volcanic flows. The five cooling units of the Bates 

Mountain Tuff are 725 feet thick at Clipper Canyon, in Lander County 

about 1 mile north of Nye County. At Butler Creek, in the Monitor 

Range, where only the upper two cooling units were deposited, the 

formation is about 300 feet thick; south of Butler Creek, where only 

the upper unit was deposited, it is generally 50-100 feet thick (figs. 

2, 3). Together the five cooling units cover about 1,900 square miles 

in northern Nye County alone and constitute a volume of about 30 

cubic miles (average thickness about 80 ft). In the study region the 

tipper cooling unit accounts for most of the distribution of the Bates 

Mountain Tuff (outlined in fig. 1); the fourth unit ("swiss cheese" 

unit) crops out across the northern part of the region, and the lower 

three units (units 1, 2, and 3) are found only in the northwestern part 

of the region (fig. 4).
BATES MOUNTAIN TUFF, NYE COUNTY, NEVADA E5

Lines of sections showing thicknesses and general lithologies of the 

Bates Mountain and certain other Tertiary tuffs are presented in figures 2 and 3. Phenocryst mineralogy of most of the units is presented 

in tables 3 and 4. Figure 2 is a line of sections from Clipper Canyon 

on the northwest to the Hot Creek Range (Crested Wheat section) 

on the southeast. In the vicinity of the Crested Wheat section (Hot 

Creek Range), only the fourth ("swiss cheese") units is tentatively 

recognized.

Figure 3 is a line of sections from Butler Creek section on the north 

to the Antelope Spring section in the southern Monitor Range on the 

southwest. It shows the upper cooling unit (No. 5) of the Bates Mountain to be persistent southward and to be overridden by younger 

unrelated ash-flow tuffs.

RBMANENT MAGNETISM

Data obtained by G. D. Bath, by J. D. Kibler, and independently 

by Sherman Gromme (written commun., 1969), all with the U.S. 

Geological Survey, on samples of Bates Mountain Tuff indicate that 

each cooling unit has a distinctive direction or remanent magnetism. 

In cooling unit 1 it is normal; in cooling units 2 and 3, reversed; in 

cooling unit 4, normal; and in cooling unit 5, nearly horizontal (table 

5; figs. 2, 3). Table 5 shows the available data on cooling unit 5. 

Determinations of polarity as reported here are based on the methods 

used by G. D. Bath and J. D. Kibler. Polarity measurements were 

made on IX 1-inch vertically drilled cores which were demagnetized 

in alternating fields to remove the effects of lightning. Their attitudes 

have been corrected for dip of the flow.

AGE

The Bates Mountain Tuff is Miocene. As originally described, the 

formation was Oligocene or Miocene (Stewart and McKee, 1968), but 

redefinition of the Oligocene-Miocene boundary at 26 m.y. (million 

years) by the Geological Society of London (1964) suggests that the 

formation should be considered Miocene. Potassium-argon determinations made on sanidine mineral separates from seven localities in 

central Nevada (all north of the region described here) before those 

of this report indicate that an average age for the formation is about 

24 m.y., which suggests early Miocene age. Of these analyses, that for 

the upper unit, dated at one locality near Eureka, Nev., gives an age 

which suggests that the unit is younger than the other cooling unit 

of the Bates Mountain; but overlap in age due to the plus-or-minus 

factor of analytical precision invalidates separation of cooling units

359-633 69 2
Clipper Canyon

Butler Creek

(composite) 

- -19 miles 

FIGURE 2. Columnar sections from Clipper Canyon section in north

Wheat section in Hot Creek Range. Numbers to right of columns 

of samples given in table 3. Line of section is shown in figure 

correlation.
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E8 CONTRIBUTIONS TO STRATIGRAPHY
BATES MOUNTAIN TUFF, NYE COUNTY, NEVADA. E9

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E10

116"

38'30' -/

Unit5 Unit 4

117° 30' 116°

39°

38°30'

Units 1, 2, and 3

FIGTJBE 4. Approximate distribution of units 1-5 of the Bates Mountain Tuff in 

northern Nye County, Nev. Small circles indicate section localities shown in 

figures 1, 2, and 3.
BATES MOUNTAIN TUFF, NTE COUNTY, NEVADA Ell

TABLE 5. Remanent-magnetism directions in samples collected from unit 5 of the

Bates Mountain Tuff

[Localities are at sections shown In figs. 1, 2, and 3. Monitor Range samples collected by J. D. 

Klbler; Toquima Range, by F. N. Houserj

Sample locality

Butler Creek, Monitor Range. _ __ _ ____ _ 

Four-mile Spring, southern Monitor Range- _ _ _

Clipper Canyon, Toquima Range __ __ _____

Azimuth

124

159 

159 

135

143 

143 

157

166 

144

Inclination

-2

+2 

+ 3 

+6

+ 11 

+ 8 -2

+22 

+ 18

by age. The determinations of this report agree with the earlier ones. 

Cooling unit 2 at Clipper Canyon in the northern Toquima Range has 

a K-Ar age of 23.7 ±1.0 m.y. (table 6, No. 3) ; the highest cooling unit 

(unit 5) from the same section has a K-Ar age of 22.2±0.9 m.y. 

(table 6, No. 1). At the Crested Wheat section in the Hot Creek Eange 

the Bates Mountain Tuff, considered here to be unit 4, has a K-Ar age 

of 22.8 ± 0.9 m.y. (table 6, No. 2).

TABLE 6. K-Ar age data on Bates Mountain Tuff and three underlying welded 

tuffs from Clipper Canyon section, Toquima Range, and from the Crested Wheat 

section, northern Hot Creek Range

Sample 

No.

1 

2 

3 

4

5 

6

Mineral KaO AH0 Radio- Apparent 

Unit and locality analyzed (weight (moles per genie argon age (m.y.) 

percent) 1 g X 1<H°) (percent)

Unit 5, Clipper Canyon section...- Sanidine..

Shingle Pass Tuff, unit 2, Crested ...do ___ 

Wheat section. 

Shingle Pass Tuff, unit 1, Crested .-.do __ .. 

Wheat section. 

Biotite-bearing tuff, Clipper Can- Biotite .... 

yon section.

8.17 

7.77 

10.47 

11.70

11.36

7.68

2.69 

2.63 

3.69 

4.25

4.24 

3.50

67.0 

54.0 

84.0 

86.5

81.1 

70.8

22.2±0.9 

22.8±0.9 

23.7±1.0 

24.6±1.0

25.1±1.0 

30.6±1.2

1 Average of duplicates.

Decay constants used for K« are: X£ = 0.585 X MH0 yr-', X/3 = 4.72 X MH0 yr-1 . 

Atomic abundance of K40 is 1.19 X 10~4 moles per mole.

The Bates Mountain Tuff rests unconf ormably on rocks of Paleozoic, 

Mesozoic, and Cenozoic age. Some of the Tertiary units that lie directly 

beneath it at certain localities have been dated. At the Clipper Canyon 

section the Bates Mountain Tuff lies on a biotite-bearing tuff which 

yielded a K-Ar age on biotite of 30.6 ±1.2 m.y. (table 6, No. 6). This 

age suggests that the welded tuff is Oligocene (Geological Society of 

London, 1964). In the northern Hot Creek Eange (Crested Wheat 

section), two units of Shingle Pass Tuff underlie the Bates Mountain 

(fig. 2). This is the only locality known to the authors where the
E12 CONTRIBUTIONS TO STRATIGRAPHY

stratigraphic relationships between the Bates Mountain and Shingle 

Pass Tuffs can be observed. Units 2 and 1 of the Shingle Pass Tuff 

are 24.5 ± 1.0 and 25.1 ±1.0 m.y. old, respectively (table 6, Nos. 4 and 5), 

and cannot be distinguished in age from the Bates Mountain Tuff 

within the precision of the K-Ar technique.

Analytical technique. Argon analyses were made, by E. H. McKee, 

by standard isotope-dilution techniques on a Nier-type 6-inch-radius 

60°-sector mass spectrometer. Potassium was analyzed by Lois B. 

Schlocker by flame photometer using a lithium internal standard. 

The errors shown as plus-or-minus values, which range from 3 to 4 

percent of the calculated ages, represent the additive effects of uncertainties in the argon and potassium analyses, in the isotopic composition and concentration of the Ar88 tracer, and in the flame photometer 

standards.

REFERENCES CITED

Cook, E. F., 1965, Stratigraphy of Tertiary volcanic rocks in eastern Nevada:

Nevada Bur. Mines Kept 11, 61 p. 

Geological Society of London, 1964, Summary of the Phanerozoic time-scale 

Geological Society Phanerozoic time-scale 1964: Geol. Soc. London Quart.

Jour., v. 120-S, p. 260-262. 

McKee, E. H., 1968, Geologic map of the Spencer Hot Springs quadrangle, Lander

County, Nevada: U.S. Geol. Survey Geol. Quad. Map GQ-770. 

 1969, The Bates Mountain Tuff of central Nevada, in Abstracts for 1968:

Geol. Soc. America Spec. Paper 121, p. 530. 

Stewart, J. H., and McKee, E. H., 1968, Geologic map of the Mount Callaghan

quadrangle, Lander County, Nevada: U.S. Geol. Survey Geol. Quad. Map

GQ-730.

O