Strontium Isotopic Composition of Paleozoic 

Carbonate Rocks in the Nevada Test Site Vicinity, 

Clark, Lincoln, and Nye Counties, Nevada, and 

Inyo County, California

Data Series 280

Prepared in cooperation with the U.S. Department of Energy, 

National Nuclear Security Administration Nevada Site Office,

Office of Environmental Management under 

Interagency Agreement DE-A152-07NA28100

U.S. Department of the Interior

U.S. Geological Survey

Strontium Isotopic Composition of 

Paleozoic Carbonate Rocks in the Nevada 

Test Site Vicinity, Clark, Lincoln, and 

Nye Counties, Nevada, and Inyo County, 

California

By James B. Paces, Zell E. Peterman, Kiyoto Futa, Thomas A. Oliver, and 

Brian D. Marshall

Prepared in cooperation with the U.S. Department of Energy 

National Nuclear Security Administration Nevada Site Office

Office of Environmental Management under 

Interagency Agreement, DE-A152-07NA28100 

Data Series 280

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2007

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Suggested citation:

Paces, J.B., Peterman, Z.E., Futo, Kiyoto, Oliver, T.A., and Marshall, B.D., 2007, Strontium isotopic composition of 

paleozoic carbonate rocks in the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, 

California: U.S. Geological Survey Data Series 280, 42 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction ....................................................................................................................................................1

Use of Strontium Isotopic Composition as a Ground-Water Tracer.............................................5

Need for Strontium Isotopic Compositions of Paleozoic Carbonate Rock Data ........................5

Description of Study Area ...................................................................................................................6

Pre-Tertiary Stratigraphy............................................................................................................6

Evolution of Pre-Tertiary Seawater Strontium Isotopes........................................................9

Purpose and Scope ............................................................................................................................10

Analytical Methods......................................................................................................................................11

Major and Trace Element Chemistry ........................................................................................................22

Strontium Isotopic Compositions ..............................................................................................................31

Summary and Conclusions.........................................................................................................................39

Acknowledgments.......................................................................................................................................39

References Cited..........................................................................................................................................39

Figures

Figure 1. Maps showing location of borehole and outcrop samples from the Nevada

Test Site region; in and adjacent to the Nevada Test Site; and Bare Mountain

and the Funeral Mountains, Clark, Lincoln, and Nye Counties, Nevada, and

Inyo County, California ..................................................................... 2

Figure 2. Chart showing principal pre-Tertiary stratigraphic units and associated

hydrogeologic units sampled in Nevada Test Site boreholes, Nye County,

Nevada ....................................................................................... 7

Figure 3. Graph showing variation in strontium isotopic composition (87Sr/86Sr) of

seawater during part of the Phanerozoic and Neoproterozoic based on

analyses of unaltered brachiopods, belemnites, and conodonts from various

locations worldwide ........................................................................ 10

Figure 4. Graph showing relation between magnesium oxide (MgO) and calcium oxide

(CaO) concentrations in acid leachates of borehole samples, Nevada Test

Site, Nye County, Nevada .................................................................. 22

Figure 5. Graphs showing relation between silicon dioxide (SiO2) and aluminum oxide

(Al2O3) concentrations and between silicon dioxide and mole percent calcite

(CaCO3) in acid leachates of borehole samples, Nevada Test Site, Nye County,

Nevada ....................................................................................... 25

Figure 6. Graph and box-and-whisper plot showing relation between strontium (Sr)

concentration and mole percent calcite (CaCO3) in acid leachates of borehole

samples, and distribution of strontium concentrations for acid leachates,

Nevada Test Site, Nye County, Nevada ................................................... 26

Figure 7. Graphs showing relation between rubidium (Rb) and silicon dioxide (SiO2)

concentrations in acid leachates of borehole samples and between

rubidium/strontium (Rb/Sr) concentration ratios and mole percent calcite

(CaCO3) in acid leachates of borehole samples, Nevada Test Site, Nye County,

Nevada ....................................................................................... 27
iv

Figures—Continued

Figure 8. Graphs showing relation between strontium (Sr) and zirconium (Zr)

concentrations, strontium and rubidium (Rb) concentrations, zirconium and

rubidium concentrations for bulk-rock outcrop samples, and the frequency

distribution of strontium concentrations for bulk-rock outcrop samples with

zirconium concentrations less than or equal to 20 micrograms per gram, Nevada

Test Site and adjacent areas, Clark, Lincoln, and Nye Counties, Nevada, and Inyo

County, California ........................................................................... 31

Figure 9. Frequency distribution plots for strontium isotopic compositions (87Sr/86Sr)

measured in borehole and outcrop samples, Nevada Test Site and adjacent

areas, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California ...... 33

Figure 10. Graphs showing relation between strontium isotopic compositions (87Sr/86Sr) and

reciprocal strontium concentrations for acid leachates of borehole samples and

87Sr/86Sr and silicon dioxide (SiO2

) concentrations for acid leachates of borehole

samples, Nevada Test Site, Nye County, Nevada ....................................... 34

Figure 11. Graphs showing relation between δ87Srt, and depositional age for acid leachates

of borehole and outcrop samples, Nevada Test Site and adjacent areas, Clark,

Lincoln, and Nye Counties, Nevada, and Inyo County, California ..................... 35

Figure 12. Maps showing spatial distribution of δ87Srt, values for borehole and outcrop

samples from the Nevada Test Site vicinity, and in and adjacent to the eastern

part of the Nevada Test Site, Clark, Lincoln, and Nye Counties, Nevada, and Inyo

County, California ........................................................................... 37

Tables

Table 1. Ages and seawater strontium isotopic composition (87Sr/86Sr) of stratigraphic

units present in the Nevada Test Site region, southern Nevada ..................... 8

Table 2. Locations of boreholes from which core samples were obtained at the Nevada

Test Site, Nye County, Nevada ............................................................ 11

Table 3. Description of samples analyzed for strontium isotopic compositions from

boreholes at the Nevada Test Site, Nye County, Nevada .............................. 12

Table 4. Locations, stratigraphic unit designations, and descriptions of outcrop samples

analyzed for strontium isotopic compositions from the Nevada Test Site vicinity,

Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California ............ 17

Table 5. Oxide and elemental concentrations and strontium isotopic compositions

(

87Sr/86Sr) of nitric-acid leachates of core samples from boreholes at the Nevada

Test Site, Nye County, Nevada ............................................................ 23

Table 6. Bulk-rock analyses of selected trace element concentrations and strontium

isotopic compositions (87Sr/86Sr) in outcrop samples collected in the early 1990s

from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and

Inyo County, California ..................................................................... 28

Table 7. Selected trace element concentrations and strontium isotopic compositions

(

87Sr/86Sr) in core samples from boreholes UE-25 a #3 and UE-25 p #1, Nevada Test

Site, Nye County, Nevada .................................................................. 32
Multiply By To obtain

centimeter (cm) 0.3937 inch

gram (g) 0.03527 ounce, avoirdupois

kilometer (km) 0.6214 mile

meter (m) 3.281 foot

meter (m) 1.094 yard

millimeter (mm) 0.03937 inch

square kilometer (km2

) 0.6124 square mile

Conversion Factors, Datum, Definitions, and 

Abbreviations and Acronyms

Conversion Factors

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32.

Datum

Horizontal coordinates convention: Horizontal coordinates, given in meters, are referenced 

to the Universal Transverse Mercator (UTM) system of Easting (X coordinate) and Northing 

(Y coordinate) distances within Zone 11 and are based on the North American datum of 1927 

(NAD27).

Definitions

Isotope notation conventions: Strontium isotopic compositions are given as both atomic ratios 

of 87Sr/86Sr as well as delta strontium-87 (δ87Sr) calculated using the formula: 

δ87Sr = [(87Sr/86Srsample/

87Sr/86Srmsw)-1]×1000,

where 87Sr/86Srmsw is the value for modern sea water (msw) of 0.70920, and the resulting value is 

in parts per thousand or per mil (‰). In addition, delta strontium-87 can be calculated using the 

value for seawater 87Sr/86Sr at the time of rock deposition and is designated as δ87Srt.

Geochronological conventions: Abbreviations used to designate geologic time in this report are 

mega-annum (Ma) to specify a specific time in millions of years before the present, and millions 

of years (m.y.) to specify the duration of a remote time interval.

Units of concentration: Concentrations of chemical constituents measured in unknown rock 

samples are given in weight percent (parts per hundred, abbreviated by wt. %) for major 

elements in the form of oxides, and micrograms per gram (parts per million, abbreviated by 

μg/g) for trace elements. Concentrations of acids used to digest the carbonate fraction of rock 

samples are given in Molarity units equal to the number of moles of a solute per liter of solvent 

(abbreviated as M).
vi

Abbreviation Chemical Species

Al2O3 aluminum oxide, or alumina

Ba barium

CaO calcium oxide

CaCO3 calcium carbonate (calcite)

Ce cerium

La lanthanum

MgO magnesium oxide

MnO manganese oxide

Nb niobium

SiO2 silicon dioxide

Rb rubidium

Sr strontium

Th thorium

U uranium

Y yittrium

Zr zirconium

Acronym Definition

DOE U.S. Department of Energy

ICP-MS Inductively coupled plasma mass spectrometry

LCA lower carbonate aquifer

NTS Nevada Test Site

SRM Standard Reference Material

USGS U.S. Geological Survey

XRF X-ray fluorescence

Abbreviations and Acronyms
Abstract

Ground water moving through permeable Paleozoic 

carbonate rocks represents the most likely pathway for 

migration of radioactive contaminants from nuclear weapons 

testing at the Nevada Test Site, Nye County, Nevada. The 

strontium isotopic composition (87Sr/86Sr) of ground water 

offers a useful means of testing hydrochemical models of 

regional flow involving advection and reaction. However, 

reaction models require knowledge of 87Sr/86Sr data for 

carbonate rock in the Nevada Test Site vicinity, which is 

scarce. To fill this data gap, samples of core or cuttings 

were selected from 22 boreholes at depth intervals from 

which water samples had been obtained previously around 

the Nevada Test Site at Yucca Flat, Frenchman Flat, Rainier 

Mesa, and Mercury Valley. Dilute acid leachates of these 

samples were analyzed for a suite of major- and trace-element 

concentrations (MgO, CaO, SiO2, Al2O3, MnO, Rb, Sr, Th, 

and U) as well as for 87Sr/86Sr. Also presented are unpublished 

analyses of 114 Paleozoic carbonate samples from outcrops, 

road cuts, or underground sites in the Funeral Mountains, Bare 

Mountain, Striped Hills, Specter Range, Spring Mountains, 

and ranges east of the Nevada Test Site measured in the early 

1990’s. These data originally were collected to evaluate the 

potential for economic mineral deposition at the potential 

high-level radioactive waste repository site at Yucca Mountain 

and adjacent areas (Peterman and others, 1994). Samples were 

analyzed for a suite of trace elements (Rb, Sr, Zr, Ba, La, and 

Ce) in bulk-rock powders, and 87Sr/86Sr in partial digestions of 

carbonate rock using dilute acid or total digestions of silicaterich rocks. Pre-Tertiary core samples from two boreholes in 

the central or western part of the Nevada Test Site also were 

analyzed. Data are presented in tables and summarized in 

graphs; however, no attempt is made to interpret results with 

respect to ground-water flow paths in this report. Present-day 

87Sr/86Sr values are compared to values for Paleozoic seawater 

present at the time of deposition. Many of the samples have 

87Sr/86Sr compositions that remain relatively unmodified from 

expected seawater values. However, rocks underlying the 

northern Nevada Test Site as well as rocks exposed at Bare 

Mountain commonly have elevated 87Sr/86Sr values derived 

from post-depositional addition of radiogenic Sr most likely 

from fluids circulating through rubidium-rich Paleozoic strata 

or Precambrian basement rocks.

Introduction 

The Nevada Test Site (NTS), occupying approximately 

3,500 km2 in southern Nevada (fig. 1), has been the primary 

site for underground testing of nuclear weapons by the United 

States since the late 1950’s. Radioactive byproducts have 

been emplaced above and below the regional water table as 

a result of this testing (Laczniak and others, 1996, p. 2). In 

an effort to understand the movement of these radioactive 

contaminants (radionuclides) away from areas of underground 

testing, the U.S. Department of Energy (DOE) has established 

an Environmental Restoration Program to investigate the 

hydrologic pathways and travel times associated with 

regional ground-water flow beneath the NTS and vicinity 

(U.S. Department of Energy, 1991, p. 2). Fractures in Middle 

Cambrian through Devonian limestones and dolomites 

constituting the regional lower carbonate aquifer (LCA) are 

the most likely pathways for the transport of radioactive 

nuclides (Winograd and Thordarson, 1975, p. 119; Laczniak 

and others, 1996, p. 15).

Strontium Isotopic Composition of Paleozoic Carbonate 

Rocks in the Nevada Test Site Vicinity, Clark, Lincoln, and 

Nye Counties, Nevada, and Inyo County, California

By James B. Paces, Zell E. Peterman, Kiyoto Futa, Thomas A. Oliver, and Brian D. Marshall
NV19-4119_fig01A

Universal Transverse Mercator projection, Zone 11.

Shaded-relief base map from 1:250,000-scale Digital Elevation Model 

based on the North American Datum of 1927. Sun illumination from the northwest

at 40 degrees above the horizon. Intensity of green shading reflects increasing 

elevation between 1500 and 3500 m.

NEVADA

NEVADA

TEST

SITE

EXPLANATION

Nevada Test Site boundary

Borehole (with or without borehole

 identification No.)

Outcrop (with or without borehole

 identification No.)

89

0

0

5

5 10 MILES

10 KILOMETERS

NYE COUNTY

CLARK COUNTY

LINCOLN COUNTY

CLARK COUNTY

NYE COUNTY

NEVADA

CALIFORNIA

NYE COUNTY

INYO COUNTY

Beatty

Mercury

Amargosa

Valley

Springdale

Indian

Springs

Yucca

Flat

S P O T T E D

R A N G E

Indian Springs

Valley

Gold Flat

Frenchman

Flat

P I N T W A T E R R A N G E

Devils

Hole

Hills

Striped

Hills

Skeleton

Hills

Kawich

Valley

Death Valley

Spring Mountains

Pahute Mesa

Timber

Mountain

Yucca

Mountain

DEATH VALLEY

NATIONAL PARK

Bare

Mountain

Funeral Mountains

Specter Range

Emigrant Valley

Las Vegas Valley

Tikaboo Valley

Amargosa River

Fortymile Wash

111

106

108

109

89

87

88

90

91

92

93

94

95

96

97

98

99

103

104

105

100

101 102

107

112

500,000 520,000 540,000 560,000 580,000 600,000 620,000 640,000 660,000

4,140,000

4,120,000

4,100,000

4,080,000

4,060,000

4,040,000

4,020,000

4,000,000

UNIVERSAL TRANSVERSE MERCATOR-EASTING, ZONE 11, IN METERS

UNIVERSAL TRANSVERSE MERCATOR-NORTHING, ZONE 11, IN METERS

A.

US

95

US

95

SR

3 7 3

Figure 1. Location of borehole and outcrop samples from (A) the Nevada Test Site region; (B) in and adjacent to the 

Nevada Test Site; and (C) Bare Mountain and the Funeral Mountains, Clark, Lincoln, and Nye Counties, Nevada, and 

Inyo County, California. Boreholes and outcrop sites without labels in figure 1A are identified in figures 1B or 1C . Map 

numbers for outcrop samples are keyed to tables 4 and 6.

 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
NV19-4119_fig01B

550,000 560,000 570,000 580,000 590,000 600,000 610,000

UNIVERSAL TRANSVERSE MERCATOR-EASTING, ZONE 11, IN METERS

Universal Transverse Mercator projection, Zone 11.

Shaded-relief basemap from 1:250,000-scale Digital Elevation Model

using the North American Datum of 1927. Sun illumination from the 

northwest at 40 degrees above the horizon

UNIVERSAL TRANSVERSE MERCATOR-NORTHING, ZONE 11, IN METERS

4,120,000

4,110,000

4,100,000

4,090,000

4,080,000

4,070,000

4,060,000

4,050,000

4,040,000

Pahute

Mesa

Rock Valley

Frenchman

Flat

Timber

Mountain

Calico

Hills

E L E A N A R A N G E

Yucca Flat

Fortymile Wash

Jackass Flat

Rainier

Mesa H A L F P I N T R A N G E

Skeleton

Hills

Striped

Hills Mercury Valley

Amargosa

Flat

Shoshone

Mountain

S P E C T E R

R A N G E

0

0

5

5 10 MILES

10 KILOMETERS

EXPLANATION

Nevada Test Site boundary

Borehole (with borehole 

 identification No.)

89 Outcrop (with map No.)

TW-C

Arargosa

Valley

Mercury 65

66

67

68

69

70

71

72

73

74 75

78 79

80

81

82

83

84

85

86

114 113

110

76,77

Nevada Test Site

ER12-1

ER12-3

ER12-4

ER16-1

ER3-1

ER5-3#2

ER6-1#2

ER6-2

ER7-1

HTH#3

UE10j

UE15d

UE16d

UE1c

UE1h

UE2ce

UE7nS

UE-25 a#3

UE-25 p#1

TW-D

TW-C

Army#1

B.

US

9 5

US

9 5

SR

3 7 3

Figure 1. Continued.

Introduction 
NV19-4119_fig01C

0

0

5 KILOMETERS

5 MILES

EXPLANATION

54 Outcrop and underground sample sites

 (with map No.)

510,000 520,000 530,000 540,000

4,090,000

4,080,000

4,070,000

4,060,000

UNIVERSAL TRANSVERSE MERCATOR-EASTING, ZONE 11, IN METERS

UNIVERSAL TRANSVERSE MERCATOR-NORTHING, ZONE 11, IN METERS

Universal Transverse Mercator projection, Zone 11.

Shaded-relief basemap from 1:100,000-scale Digital Elevation Model

using the North American Datum of 1927. Sun illumination from the 

northwest at 40 degrees above the horizon

A M A R G O S A D E S E R T

Crater

Flat

F U N E R A L M O U N T A I N S

B A R E M O U N T A I N

C.

1 2,3

4

5

6

7

8

9-15

16,17

18

19

20

21

22-28

29

30

31

34-37 32,33

38 39

40

41-43

44

45

46

47

48

49

50-52

53

54

55

56,57

58

60 59

61,62

63

64

Figure 1. Continued.

 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Geochemical and isotopic data from ground-water 

samples are being used to evaluate possible ground-water 

flow paths in the DOE Environmental Restoration Program 

(Thomas and others, 2002; Hershey and others, 2005; Rose 

and others, 2006; Farnham and others, 2006). Conservative 

tracers (isotopes or elements that undergo negligible 

modification by water-rock interaction) typically are used 

to delineate ground-water flow paths and evaluate mixing 

of water masses from upgradient sources. These tracers are 

combined with other dissolved constituents in advectionreaction geochemical modeling (NETPATH, PHREEQC) to 

evaluate chemical evolution along postulated ground-water 

flow paths. However, to understand the potential contributions 

of rock and mineral constituents, chemical compositions of 

aquifer components are required as inputs in geochemical 

models. Isotope tracers of geochemical processes can help 

discriminate between alternative flow models whose solutions 

may remain non-unique based on chemical concentrations 

alone. Like other chemical constituents, an understanding of 

the range of compositions in both water and rock is required 

for constraining flow paths and for evaluating possible aquiferwater interactions.

Use of Strontium Isotopic Composition as a 

Ground-Water Tracer

The isotopic composition of strontium (87Sr/86Sr) can 

be used as a natural tracer of ground-water flow because 

the strontium ion (Sr+2) is soluble in aqueous solutions at 

levels allowing high-precision isotope measurement, because 

variations in rubidium-to-strontium (Rb/Sr) ratios in rocks 

of different type and petrogenetic origin result in distinctive 

87Sr/86Sr ground-water signatures, and because fractionation 

of heavy radiogenic isotopes (87Sr from 86Sr) is negligible for 

geologic processes (Peterman and Stuckless, 1992; McNutt, 

2000). However, unlike conservative tracers, 87Sr/86Sr values 

can be modified along ground-water flow paths by reaction 

with the aquifer rock. Studies have shown that Sr dissolved 

in ground water may not be in isotopic equilibrium with the 

aquifer through which it flows (Peterman and Stuckless, 

1992, and references therein). This disequilibrium commonly 

provides important insight into the ground-water flow 

system for which conceptual models may otherwise be 

oversimplified. For example, in several carbonate aquifer 

studies, 87Sr/86Sr ratios in ground-water samples are larger 

than those of the aquifer rock (Chaudhuri and others, 1987; 

Banner and others, 1989, p. 396; McKenna and others, 1992; 

Peterman and others, 1992, p. 827; Frost and Toner, 2004). 

This disequilibrium requires ground-water contributions 

from associated Precambrian rocks having higher 87Sr/86Sr 

signatures, but which typically were considered to be 

impermeable. 

The behavior of Sr and 87Sr/86Sr in ground-water flow 

systems depends on numerous factors including length of 

flow path, water-to-rock mass ratio, chemical reaction rates, 

Sr concentration and 87Sr/86Sr in solid and fluid phases, flow 

velocity, advective fluid mixing, dispersion, and ion exchange 

(Johnson and DePaolo, 1994, 1997). In aquifers dominated 

by fracture flow, the Sr isotopic composition of water is less 

likely to be modified by changes in rock 87Sr/86Sr values along 

a flow path than in aquifers dominated by matrix flow because 

of faster flow velocities, larger water-to-rock mass ratios, and 

slower reaction rates (Johnson and others, 2000). Therefore, 

in aquifers dominated by fracture flow or high permeability 

matrix flow, such as alluvium, Sr may be useful as a tracer of 

water from upgradient sources (Johnson and DePaolo, 1994, p. 

1576), at least at path lengths commensurate with the scale of 

the NTS. 

Chemical processes resulting in nonconservative behavior 

of Sr in ground water affect Sr concentrations to a greater 

extent than 87Sr/86Sr values. Losses of Sr from solution due to 

sorption and mineral precipitation will not change the 87Sr/86Sr 

ratio in the remaining fluid. Furthermore, desorption or cation 

exchange from reactive mineral surfaces along flow paths may 

not significantly affect 87Sr/86Sr values if the dynamics of flow 

and sources of Sr have remained unchanged over long periods 

(steady-state flow conditions). In contrast, rock dissolution 

can add Sr containing very different isotopic compositions to 

solution, particularly if ground water that is unsaturated, with 

respect to calcite or dolomite, flows into the LCA. 

Need for Strontium Isotopic Compositions of 

Paleozoic Carbonate Rock Data

Use of 87Sr/86Sr as a tracer in advection-reaction 

geochemical models of ground-water flow in the LCA 

requires knowledge of rock Sr concentrations and 87Sr/86Sr 

compositions. The structures of minerals constituting marine 

carbonate deposits result in rocks with relatively high Sr 

concentrations and low Rb concentration. Therefore, the 

87Sr/86Sr values inherited from seawater will not change 

appreciably with time due to the decay of 87Rb. However, 

previous studies demonstrated that at least some Paleozoic 

carbonate rocks in the NTS vicinity have nonmarine 87Sr/86Sr 

compositions indicating that radiogenic 87Sr from crustal 

sources was introduced into the carbonate rocks at some time 

in the past (Peterman and others, 1994; J. Kenneally, Lawrence 

Livermore National Laboratory, written commun., 1995). 

These studies indicate that Paleozoic carbonate rocks at the 

NTS can have a much wider range of 87Sr/86Sr values that are 

more radiogenic than values derived from a seawater origin. 

Introduction 
Ground water flowing through the LCA on the east side 

of the NTS commonly has 87Sr/86Sr values that are greater 

than values expected from seawater sources (Hershey and 

others, 2005; Farnham and others, 2006). Advection-reaction 

geochemical models of ground-water evolution between 

sample sites commonly require small amounts of mineral 

dissolution that would likely affect the 87Sr/86Sr of dissolved 

Sr in the water. However, because 87Sr/86Sr compositions of 

most carbonate rocks on the NTS generally are not available, 

the influence of water-rock reaction during chemical evolution 

along flow paths cannot be evaluated effectively. Therefore, 

it is necessary to better constrain rock 87Sr/86Sr values present 

along potential flow paths to more reliably utilize 87Sr/86Sr as a 

ground-water tracer. 

Description of Study Area

Because ground-water flow through the LCA represents 

the most likely scenario for transporting radionuclides 

beyond the eastern and southern boundaries of the NTS, 

characterization of 87Sr/86Sr in Paleozoic carbonate rocks 

constitutes the focus of this study. A small number of older 

carbonate rocks as well as a few samples of Paleozoic silicate 

rocks are also included. Most rocks constituting the LCA were 

deposited as chemical precipitates from Paleozoic seawater. 

Because this reservoir is well mixed on a global scale by 

vertical and lateral circulation patterns, its Sr isotope evolution 

has been well documented by examining samples from many 

other areas. Both the stratigraphy of pre-Tertiary rocks and the 

evolution of seawater 87Sr/86Sr are described in the following 

sections.

Pre-Tertiary Stratigraphy

Pre-Tertiary rocks of southeastern Nevada consist of 

a thick sequence of older (Neoproterozoic to Devonian 

in age) shallow-water marine sediments deposited in a 

miogeoclinal (passive continental shelf) environment 

and younger (Devonian to Mississippian in age) marine 

sediments deposited in a foreland basin along the Cordilleran 

continental margin. A generalized stratigraphic succession 

of the approximately 11,500-m-thick sequence of preTertiary rocks present on the NTS is shown in figure 2. The 

summary presented below is compiled from more detailed 

descriptions presented by Burchfiel (1964), Barnes and 

Christiansen (1967), Stewart and Poole (1974), Winograd 

and Thordarson (1975), Monsen and others (1992), Laczniak 

and others (1996), Trexler and others (1996; 2003), Slate and 

others (1999), and Page and others (2005). Age estimates for 

stratigraphic units from the NTS and surrounding areas are 

listed in table 1.

The oldest sedimentary rocks on the NTS consist of a 

2,800-m-thick series of Neoproterozoic and lower Cambrian 

deposits dominated by marine clastic sediments (quartzite, 

arkose, siltstone, and shale/argillite). Silty carbonate units, 

such as the Noonday Dolomite and dolomitic units in 

the Wood Canyon and Johnnie Formations, are present 

locally in this sequence. The well-cemented to moderately 

metamorphosed rocks of this sequence generally are 

considered to be poor transmitters of ground-water flow 

and constitute the lower clastic confining unit of Winograd 

and Thordarson (1975). The Lower-to-Middle Cambrian 

Carrara Formation contains siltstone and shale with thin, but 

persistent, limestone beds that become more common upsection. These time-transgressive lithologic changes reflect the 

regional transition to a depositional environment dominated by 

marine carbonate sedimentation.

The 5,200-m-thick section of Middle Cambrian through 

Devonian rocks is composed of marine limestones and 

dolomites with minor interbeds of sandy or silty clastic 

units (Barnes and Christiansen, 1967; Stewart and Poole, 

1974; Trexler and others, 1996, 2003; Slate and others, 

1999). Aquifer tests indicate very high degrees of water 

transmissivity through these units due to extensive secondary 

permeability along a well-connected network of solutionenhanced fractures, faults, and breccias (Winograd and 

Thordarson, 1975, p. 117; Laczniak and others, 1996). 

Collectively, these rocks constitute the LCA and provide 

the main pathways for ground-water flow between Tertiary 

basins. Because the few clastic units within this sequence 

(Dunderberg Shale Member of the Nopah Formation, the 

Ninemile Formation of the Pogonip Group, and the Eureka 

Quartzite) are thin and structurally disrupted, they do not 

constitute regionally effective confining units, though they 

may impede flow locally (Laczniak and others, 1996, p. 15).

Mississippian strata overlying Devonian and 

older carbonates of the LCA are mostly clastic rocks 

(conglomeritic sandstone, siltstone, shale, bioclastic 

limestone, and rare quartzite) to the west of Yucca Flat 

and carbonate to the east of the NTS (Winograd and 

Thordarson, 1975, p. 9; Trexler and others, 1996, 2003). 

These rocks reflect a change from sedimentation along a 

passive continental margin to clastic-dominated depositional 

environments in foreland basins associated with convergent 

tectonics of the Antler orogeny (Poole, 1974; Cole and 

others, 1997; Cole and Cashman, 1999; Trexler and others, 

2003). Up to 3,000 m of predominantly synorogenic 

siliciclastic rocks constitute the Late Devonian to Middle 

Mississippian Eleana Formation and laterally equivalent 

Gap Wash Formation as well as the overlying Late 

Mississippian Chainman Shale/Captain Jack Formations 

(Cole and Cashman, 1999; Trexler and others, 2003). 

 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
NV19-0119_NTSRock_FIG-02

Rock system Stratigraphic unit Abbreviation Hydrogeologic unit

Tertiary

Valley-fill deposits Alluvial aquifer

Volcanic rocks Volcanic aquifers and confining units

Lower Permian & Pennsylvanian Tippipah Limestone PPt Upper carbonate-rock aquifer

Mississippian and upper Devonian

Chainman Shale Mc

Upper clastic confining unit Gap Wash Formation

Eleana Formation

MDg

MDe

Devonian

Guilmette Formation Dg

Lower carbonate-rock aquifer

Simonson Dolomite Dsi

Sevy Dolomite Dsv

Devonian and Silurian Lone Mountain Dolomite DSlm

Silurian

Roberts Mountains Formation Sr

Laketown Dolomite Sl

Ordovician

Ely Springs Dolomite Oes

Eureka Quartzite Oeq

Pogonip Group

Antelope Valley Limestone Op-av

Ninemile Formation Op-n

Goodwin Limestone Op-g

Cambrian

Nopah Formation

Smoky Member €n-s

Halfpint Member €n-h

Dunderberg Shale Member €n-d

Bonanza King 

Formation

Banded Mountain Member €bb

Papoose Lake Member €bp

Carrara Formation

Upper part €c-u

Lower part €c-l

Lower clastic confining unit

Cambrian and Neoproterozoic Wood Canyon Formation €Zw

Neoproterozoic

Stirling Quartzite Zs

Johnnie Formation Zj

Noonday Dolomite Zn Not classified

Figure 2. Principal pre-Tertiary stratigraphic units and associated hydrogeologic units sampled in Nevada Test Site boreholes, Nye 

County, Nevada.

Introduction 
Symbol Stratigraphic unit Epoch Age range 

(m.y.)

Minimum 

87

Sr/86Sr

Maximum 

87

Sr/86Sr Mean87

Sr/86Sr

PPt Tippipah Limestone Pennsylvanian and Early Permian 270–325 0.7073 0.7084 0.7080

PMb Bird Spring Formation–undivided Late Mississippian and Early 

Permian

270–340 .7073 .7084 .7079

PMbl Bird Spring Formation–lower member Late Mississippian and Early 

Permian

270–340 .7073 .7084 .7080

Mm Monte Cristo group Early and Late Mississippian 325–354 .7077 .7084 .7079

Mc Chainman Shale Early and Late Mississippian 325–354 .7077 .7082 .7079

Mj Joana Limestone Early Mississippian 340–354 .7077 .7082 .7080

MDe Eleana Formation Late Devonian and Mississippian 325–369 .7077 .7083 .7080

MDg Gap Wash Formation Late Devonian and Mississippian 325–369 .7077 .7083 .7080

Dg Guilmette Formation Middle and Late Devonian 354–384 .7078 .7083 .7080

Df Fluorspar Canyon Formation Middle Devonian 369–384 .7078 .7079 .7079

Dsi Simonson Dolomite Middle Devonian 369–384 .7078 .7079 .7079

Dtc Rocks of Tarantula Canyon Devonian 354–410 .7078 .7088 .7082

Dsv Sevy Dolomite Early and Middle Devonian 369–410 .7078 .7088 .7082

Du Undifferentiated rocks of Devonian in age Devonian 354–410 .7078 .7088 .7082

DSlm Lone Mountain Dolomite Late Silurian and Early Devonian 384–420 .7079 .7088 .7085

DSu Undifferentiated rocks of Devonian or 

Silurian age

Devonian or Silurian 354–434 .7078 .7088 .7083

Sr Roberts Mountains Formation Silurian 410–434 .7080 .7088 .7084

Sl Laketown Dolomite Silurian 410–434 .7080 .7088 .7084

Oes Ely Springs Dolomite Late Ordovician 434–459 .7079 .7085 .7081

Op Pogonip Group Late Cambrian and 

MiddleOrdovician

459–498 .7084 .7091 .7089

Op-av Antelope Valley Limestone of Pogonip Group Early and Middle Ordovician 459–490 .7084 .7091 .7089

Op-g Goodwin Limstone of Pogonip Group Early Ordovician and LateCambrian 470–498 .7089 .7091 .7090

Ou Undifferentiated rocks of Ordovician age Ordovician 434–490 .7079 .7091 .7085

Table 1. Ages and seawater strontium isotopic composition (87Sr/86Sr) of stratigraphic units present in the Nevada Test Site region, 

southern Nevada.

[Stratigraphic units and epochs are from the U.S. Geological Survey Geologic Names Lexicon database (http://ngmdb.usgs.gov/Geolex/geolex_home.html). 

Age assignments are based on the time scale of Young and Laurie (1996), which McArthur and others (2001) used to construct the Paleozoic seawater curve (fig. 

3). Maximum, minimum, and mean Sr isotopic compositions are determined from values shown in figure 3 averaged over the time period given. Age ranges are 

given in millions of years before present (m.y.)]

Although silty carbonate beds present in the Late 

Mississippian Captain Jack Formation (and, to a lesser 

extent, Chainman Shale) reflect a return to shallow-water 

marine environments, the thick siliciclastic sediments have 

low permeability and form the upper clastic confining unit in 

western Yucca Flat and Jackass Flat that isolates most regional 

ground-water flow in the LCA (Winograd and Thordarson, 

1975, p. 43). Approximately 1,100 m of Pennsylvanian to 

early Permian Tippipah Limestone are preserved in two 

localities in the central NTS that unconformably overlie 

muddy shelf deposits of the Chainman Shale (Cole and 

Cashman, 1999). Winograd and Thordarson (1975, p. 30) 

included these rocks in the upper-carbonate-rock aquifer, but 

recognized their restricted distribution within the saturated 

zone and the limited role of the upper carbonate aquifer in 

regional ground-water movement. East of the NTS, the upper 

clastic confining unit is not present and Paleozoic carbonate 

rocks, regardless of age, form a single regional carbonate-rock 

aquifer (Laczniak and others, 1996, p. 15). 

   Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Symbol Stratigraphic unit Epoch Age range 

(m.y.)

Minimum 

87

Sr/86Sr

Maximum 

87

Sr/86Sr Mean87

Sr/86Sr

OCu Undifferentiated rocks of Ordovician or 

Cambrian age

Ordovician or Cambrian 434–509 0.7079 0.7091 0.7086

Cn Nopah Formation Late Cambrian 490–498 .7091 .7092 .7091

Cn-s Smoky Member of Nopah Formation Late Cambrian 490–498 .7091 .7092 .7091

Cn-h Halfpint Member of Nopah Formation Late Cambrian 490–498 .7091 .7092 .7091

Cn-d Dunderberg Shale Member of Nopah 

Formation

Late Cambrian 490–498 .7091 .7092 .7091

Cb Bonanza King Formation Middle and Late Cambrian 490–509 .7088 .7092 .7091

Cb-b Banded Mountain Member of Bonanza King 

Formation

Late Cambrian 490–498 .7091 .7092 .7091

Cb-p Papoose Lake Member of Bonanza King 

Formation

Middle Cambrian 498–509 .7090 .7092 .7090

Cu Undifferentiated rocks of Cambrian Age Cambrian 490–542 .7085 .7091 .7088

Cc Carrara Formation Early and Middle Cambrian 498–542 .7085 .7092 .7087

Cc-m Carrara Formation-Middle Part Early and Middle Cambrian 498–542 .7085 .7092 .7087

CZw Wood Canyon Formation Neoproterozoic and EarlyCambrian 509–600 .7079 .7088 .7084

CZw-u Wood Canyon Formation-Upper Member Early Cambrian 509–542 .7085 0.7088 .7086

CZw-l Wood Canyon Formation-Lower Member Neoproterozoic 542–600 .7085 .7079 .7084

Zs Stirling Quartzite Neoproterozoic 542–1,000 .7055 .7085 Undefined

Zs-c Stirling Quartzite-C Member Neoproterozoic 542–1,000 .7055 .7085 Undefined

Zs-d Stirling Quartzite-D Member Neoproterozoic 542–1,000 .7055 .7085 Undefined

Zj Johnnie Formation Neoproterozoic 542–1,000 .7055 .7085 Undefined

Zn Noonday Dolomite Neoproterozoic 542–1,000 .7055 .7085 Undefined

ZYb Beck Spring Dolomite Neoproterozoic and 

Mesoproterozoic

542–1,600 .7055 .7085 Undefined

ZYc Crystal Spring Formation of Pahrump Group Neoproterozoic and 

Mesoproterozoic 542–1,600 .7055 .7085 Undefined

Table 1. Ages and seawater strontium isotopic composition (87Sr/86Sr) of stratigraphic units present in the Nevada Test Site region, 

southern Nevada.—Continued

[Stratigraphic units and epochs are from the U.S. Geological Survey Geologic Names Lexicon (GEOLEX) database (http://ngmdb.usgs.gov/Geolex/geolex_

home.html). Age assignments are based on the time scale of Young and Laurie (1996), which McArthur and others (2001) used to construct the Paleozoic 

seawater curve (fig. 3). Maximum, minimum, and mean Sr isotopic compositions are determined from values shown in figure 3 averaged over the time period 

given. Age ranges are given in millions of years before present (m.y.)]

Evolution of Pre-Tertiary Seawater Strontium 

Isotopes

The isotopic composition of seawater has evolved 

through time due to the balance of fluxes from continental 

(fluvial inputs), mantle (volcanic and hydrothermal activity 

at mid-ocean spreading centers), and continental shelf 

(diagenesis and dolomitization of marine carbonate) sources 

(Peterman and others, 1970; Burke and others, 1982; Faure, 

1986; Peterman and Stuckless, 1992; Veizer and others, 

1999, Faure and Mensing, 2005, p. 440). Determination of 

the seawater 87Sr/86Sr evolution curve is possible because 

Sr concentrations in biogenic carbonate are high (Sr readily 

substitutes for Ca, especially in the aragonite crystal structure) 

whereas radioactive 87Rb [the parent isotope for 87Sr with a 

half-life of 48.8 million years (m.y.)] is excluded. Therefore, 

seawater Sr is incorporated into the crystal structure of marine 

calcite or aragonite and remains unchanged with time in 

Introduction 
rocks and carbonate fossils that have remained unmodified 

by secondary processes. Values of 87Sr/86Sr for Triassic 

through Cambrian brachiopods, belemnites, and conodonts 

and Neoproterozoic carbonate rocks from many locations 

around the world have been compiled to define the Paleozoic 

seawater 87Sr/86Sr evolution curve, shown in figure 3 along 

with bounding curves that represent probable uncertainties for 

mean seawater compositions at any one time period. Seawater 

87Sr/86Sr values fluctuated from a high of around 0.7092 during 

the late Cambrian Period to a low of around 0.7070 in the late 

Permian Period with numerous fluctuations in between. 

Post-depositional modification of 87Sr/86Sr can occur by 

several mechanisms including (1) accumulation of 87Sr from 

the radioactive decay of small amounts of 87Rb incorporated 

in the rock, especially in finely dispersed clay particles, (2) 

exchange of Sr with fluids during diagenesis or dolomitization, 

or (3) introduction of exotic strontium by hydrothermal fluids 

carrying radiogenic 87Sr derived from basement sources 

(Peterman and others, 1994). These processes typically drive 

rock 87Sr/86Sr compositions toward higher (more radiogenic) 

values. Dolomites with low Sr concentrations may be 

particularly susceptible to subsequent introduction of exotic 

Sr. 

Purpose and Scope

The purpose and scope of this report are to present 

chemical and 87Sr/86Sr data from cuttings and core samples 

of Paleozoic carbonate rocks from NTS boreholes (table 2) 

where ground-water data are available. Paleozoic rock 

samples from 20 boreholes in the Yucca Flat, Rainier Mesa, 

Frenchman Flat, and Mercury Valley were collected in 2005 

and 2006 from zones within the LCA that produced water. In 

addition to these recently acquired data, chemical and isotopic 

data acquired from the same laboratory also are reported for 

rock samples obtained in the early and middle 1990s. These 

samples are from outcrops located outside the NTS and from 

two boreholes in the southwestern part of the NTS. These 

data are discussed in Peterman and others (1994), but were 

not published previously. Data in this report are presented in 

geospatial, tabular, and graphic forms, and are discussed in 

terms of the degree to which the compositions may have been 

modified by post-depositional chemical processes. However, 

no attempt is made to interpret these data with respect to 

water-rock interactions, reactive-transport mechanisms, or 

ground-water flow-path identification. 

200 250 300 350 400 450 500 550 600 205.7 230 243 251 270 298 325 354 369 384 410 420 434 459 490 498 509 542

0.7070

0.7065

0.7075

0.7080

0.7085

0.7090

0.7100

0.7095

Pennsylvanian

Mississippian

Triassic

Permian

Devonian

Silurian

Ordovician

Cambrian

Neoproterozoic

87Sr / 86Sr

AGE (Ma)

Figure 3. Variation in strontium isotopic composition (87Sr/86Sr) of seawater during part of the Phanerozoic and 

Neoproterozoic based on analyses of unaltered brachiopods, belemnites, and conodonts from various locations 

worldwide. Dark curve represents the best-fit value for ages and 87Sr/86Sr values for data regressed by McArthur 

and others (2001) along with the 95-percent confidence level estimates (orange-shaded area). Solid vertical lines 

represent Period boundaries and dashed vertical lines represent Epoch boundaries based on the timescale of 

Young and Laurie (1996) as given in McArthur and others (2001), table 1.

10 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Analytical Methods

Core and cutting samples of Paleozoic rock core 

were obtained in 2006 from material archived at the U.S. 

Geological Survey (USGS) Core Library and Data Center in 

Mercury, Nevada. Intervals corresponding to water-producing 

zones were examined and samples were selected based on 

availability, representation of macroscopic features, and 

location in the stratigraphic section. Borehole intervals, sample 

types, stratigraphic units, and sample descriptions are given 

in table 3. Where only cuttings were available, samples with 

the largest fragment size were selected preferentially. In a few 

cases, special features were targeted, such as secondary calcite 

veins or altered breccia zones, to evaluate the differences 

between primary and secondary 87Sr/86Sr signatures; however, 

most samples were collected to evaluate unaltered, bulk-rock 

compositions. Stratigraphic units were assigned to samples 

using lithologic logs from borehole completion reports 

to DOE, which have been compiled recently by the U.S. 

Geological Survey (2006). Other sources include Maldonado 

and others, (1979) for borehole UE-25 a #3, and Carr and 

others, (1986) for borehole UE-25 p #1. These assignments 

were made by correlations with known stratigraphic sections 

or through biostratigraphic assignments, most commonly 

using conodonts (typically evaluated and reported as 

unpublished data by A. Harris, U.S. Geological Survey). 

Table 2. Locations of boreholes from which core samples were obtained at the Nevada Test Site, Nye County, Nevada.

[Location of sampling sites are shown in figure 1B. Additional information on these and other boreholes associated with the Department of Energy weapons 

testing program at the Nevada Test Site is available at http://nevada.usgs.gov/mercury/core.html. Abbreviations: DOE, U.S. Department of Energy; USGS, U.S. 

Geological Survey; m, meter; UTM, Universal Transverse Mercator]

DOE borehole 

identification No.

Borehole 

identification 

No.

USGS site 

identification 

No.

UTMEasting, 

zone 11

(m)

UTMNorthing, 

zone 11

(m)

Land

surface 

elevation 

(m)

Date

constructed

Borehole 

depth 

(m)

Army #1 Water Well Army #1 363530116021401 586,120 4,049,800 961.1 07–15–62 595.3

ER–3–1 ER3–1 370116115561301 594,658 4,097,339 1,343.2 05–20–94 855.6

ER–5–3 #2 ER5–3 #2 365223115561801 594,624 4,081,120 1,016.3 03–20–01 1,732.2

ER–6–1 #2 ER6–1 #2 365901115593501 589,617 4,093,357 1,199.5 10–05–02 975.4

ER–6–2 ER6–2 365740116043501 582,236 4,090,745 1,289.7 07–21–94 1,045.5

ER–7–1 ER7–1 370424115594301 589,315 4,103,275 1,294.2 02–09–03 762.0

ER–12–1 ER12–1 371106116110401 572,412 4,115,493 1,773.1 11–24–92 1,093.6

ER–12–3 ER12–3 371142116125102 569,748 4,116,592 2,250.9 04–28–05 1,496.0

ER–12–4 ER12–4 371311116105902 572,473 4,119,346 2,097.9 06–01–05 1,132.3

ER–16–1 ER16–1 370031116121102 570,900 4,095,916 2,000.4 07–01–05 1,220.7

UE–1c UE1c 370253116055201 580,223 4,100,394 1,282.2 02–11–64 573.0

UE–1h UE1h 370005116040301 582,983 4,095,224 1,217.7 07–03–68 1,023.5

UE–2ce Water Well UE2ce 370831116080701 576,804 4,110,773 1,452.2 01–23–77 502.9

UE–7nS UE7nS 370556116000901 588,644 4,106,091 1,331.0 07–14–76 672.1

UE–10j UE10j 371108116045301 581,527 4,115,645 1,394.1 02–24–93 796.4

UE–15d Water Well UE15d 371230116021501 585,061 4,118,301 1,397.9 04–17–62 1,829.1

UE–16d Eleana Water Well UE16d 370412116095101 574,301 4,102,761 1,427.7 03–03–81 914.4

UE–25 p #1 UE25p #1 364938116252102 551,509 4,075,663 1,113.9 05–24–83 1,805.0

UE–25 a #3 UE25a #3 365147116185301 561,079 4,079,703 1,385.6 10–10–78 771.1

USGS HTH #3 HTH #3 364830115512601 601,932 4,074,016 1,062.0 05–09–62 566.9

USGS Test Well C (WW-C) TW–C 365508116003501 588,208 4,086,130 1,194.8 03–30–61 518.2

USGS Test Well D TW–D 370418116044501 582,224 4,103,327 1,265.1 01–08–61 594.4

Analytical Methods 11
DOE borehole 

identification 

No.

Top 

depth 

(m)

Bottom 

depth 

(m)

Sample 

identification 

No.

Sample type Stratigraphic 

unit symbol Description

Army #1 261.8 261.8 Army 1(859) Core Cn-s Mottled medium-to-dark grey, medium-grained 

limestone. Minor fractures filled with thin white 

secondary calcite. No alteration apparent.

262.7 262.7 Army 1(862) Core Cn-s Friable, altered limestone consisting of equant, 

medium-grained, dark grey calcite crystals with 

intergranular iron-stained (clayey?) material. Also, 

several fragments of other rock or vein material 

present as rounded clasts.

299.3 302.4 Army 1(982)A Core Cn-h Uniform, coarse-grained, medium-grey dolomite. 

Minor color mottling between light and medium 

grey.

299.3 302.4 Army 1(982)B Core Cn-h Thick (>15 mm) vein of sparry white-to-reddish 

tan calcite cutting grey dolomite. Sample isolates 

calcite vein from host rock.

388.9 345.0 Army 1(1112) Core Cn-h Highly broken and altered limestone. Original light 

grey, medium grained carbonate is highly fractured 

and altered to friable, brown clay-rich material.

594.7 594.7 Army 1(1951) Core fragments Cb Fragments of equigranular, coarse-grained, light-grey 

limestone with abundant fractures, some of which 

contain secondary cement and red-brown staining.

ER–3–1 694.9 698.0 ER3–1(2280) Coarse cuttings Cb Medium-to-coarse grained, medium grey limestone.

786.4 789.4 ER3–1(2580) Cuttings Cb Massive fine-grained, light grey limestone.

ER–5–3#2 1,456.9 1,460.0 ER5–3 2(4780) Cuttings Dsv Medium-to-coarse grained, pinkish grey limestone.

ER–6–1#2 661.4 664.5 ER6–1 2(2170) Cuttings Dsv Coarse grained, white-to-light grey dolomite.

801.6 804.7 ER6–1 2(2630) Cuttings Sl Coarse grained, white-to-light grey dolomite.

862.6 865.6 ER6–1 2(2830) Cuttings Sl Coarse grained, white-to-light grey dolomite.

911.3 914.4 ER6–1 2(2990) Cuttings Oes Medium-to-coarse grained, grey dolomite.

ER–6–2 557.8 560.8 ER6–2(1830) Cuttings Cb Medium-grained, grey limestone.

648.9 648.9 ER6–2(2129) Core Cb Uniform medium-grained, brownish grey dolomite 

with scattered thin fractures containing finegrained white filling material.

725.1 725.1 ER6–2(2379) Core Cb (mineralized 

fault)

Mottled medium-to-coarse grained, dark grey 

dolomite. Mottling is caused by irregular patches 

of coarser, lighter crystals surrounded by finer, 

darker crystals. Rock is cut by scattered thin, 

white-calcite-filled veins.

796.4 796.4 ER6–2(2613) Core Dg Medium-grained, medium grey limestone with 

numerous thin fractures filled with white 

secondary calcite. No evidence of staining or 

alteration.

Table 3. Description of samples analyzed for strontium isotopic compositions from boreholes at the Nevada Test Site, Nye County, 

Nevada.

[Stratigraphic units are from lithology logs included in borehole completion reports to U.S. Department of Energy (see U.S. Geological Survey, 2006, for 

compilation of data and references, as well as Maldonado and others [1979], and Carr and others [1986]). Stratigraphic unit symbols are defined in table 1. Core 

and cutting samples were obtained in 2006 except for samples from boreholes UE–25 a #3 and UE–25 p #1, which were obtained in the early 1990s. Borehole 

depths are measured in feet below land surface. Abbreviations: DOE, Department of Energy; m, meter; mm, millimeter; >, greater than; <, less than; ±, plus or 

minus]

12  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
DOE borehole 

identification 

No.

Top 

depth 

(m)

Bottom 

depth 

(m)

Sample 

identification 

No.

Sample type Stratigraphic 

unit symbol Description

ER–6–2 829.5 829.5 ER6–2(2721.5) Core Dg (mineralized 

fault)

Mottled, fine-grained limestone consisting of light 

grey carbonate with extensive recrystallization and 

solution-breccia replacement textures. More-recent 

fractures commonly have light amounts of red 

staining.

ER–7–1 655.3 658.4 ER7–1(2150) Coarse cuttings Op Very coarse-grained, medium grey limestone with 

patches or veins of finer grained carbonate that are 

either the same color as rock mass or lighter cream 

to reddish tan to brownish red.

728.5 731.5 ER7–1(2390) Coarse cuttings Op Cuttings of very coarse-grained, medium grey 

limestone with very uniform consistency. No veins 

or accessory phases observed, but many of the 

calcite crystals and fragment surfaces are mildly 

stained brownish red.

ER–12–1 524.3 527.3 ER12–1(1720) Cuttings Lower Dg or upper 

Dsi

Fine-to-medium grained carbonate including both 

medium grey and dark grey components. Both 

graphite and dispersed fine-grained pyrite are 

common, as are fragment surfaces coated with 

reddish-brown staining.

1,018.0 1,021.1 ER12–1(3340) Cuttings Upper Dsv Homogeneous sample of coarse-grained, white-tolight grey carbonate. Fragments are clean with no 

staining or other discoloration on surfaces.

ER–12–3 1,103.4 1,106.4 ER12–3(3620) Cuttings Mid to Late 

Ordovician

Uniform medium-grained, dark-grey dolomite with 

minor thin, white carbonate veins. Some veins are 

stained red.

1,368.6 1,371.6 ER12–3(4490) Cuttings Mid Ordovician to 

Late Cambrian

Fine-to-coarse grained, light-to-dark grey limestone 

with minor color laminae in some fragments. 

Occassional thin, coarsely crystalline white 

carbonate veins. Minor iron staining.

1,475.2 1,478.3 ER12–3(4840) Cuttings Mid Ordovician to 

Late Cambrian

Fine-to-coarse grained, medium-grey limestone with 

laminae in some fragments. Occasional thin white 

carbonate veins. Pyrite present on one fragment, 

but no noticable iron staining.

ER–12–4 786.4 789.4 ER12–4(2580) Coarse cuttings DSu Cuttings dominated by medium- to coarse-grained, 

white-to-light grey dolomite. Small grains of 

an equant black mineral (oxidized pyrite?) are 

scattered throughout. Some surfaces have red 

staining.

1,051.6 1,054.6 ER12–4(3450) Coarse cuttings Mid Ordovician to 

Late Cambrian

Cutting sample includes a range of dolomite 

fragments. Coarse-grained, white-greenish-grey 

fragments are dominant, but medium-grained, 

medium-to-dark grey fragments also are common.

1,094.2 1,097.3 ER12–4(3590) Cuttings Mid Ordovician to 

Late Cambrian

Medium-to-coarse grained, medium-grey dolomite 

with abundant fine crystals of oxidized pyrite and 

coarse, white acicular mineral (tremolite?).

Table 3. Description of samples analyzed for strontium isotopic compositions from boreholes at the Nevada Test Site, Nye County, 

Nevada.—Continued

[Stratigraphic units are from lithology logs included in borehole completion reports to U.S. Department of Energy (see U.S. Geological Survey, 2006, for 

compilation of data and references, as well as Maldonado and others [1979], and Carr and others [1986]). Stratigraphic unit symbols are defined in table 1. Core 

and cutting samples were obtained in 2006 except for samples from boreholes UE–25 a #3 and UE–25 p #1, which were obtained in the early 1990s. Borehole 

depths are measured in feet below land surface. Abbreviations: DOE, Department of Energy; m, meter; mm, millimeter; >, greater than; <, less than; ±, plus or 

minus]

Analytical Methods 13
DOE borehole 

identification 

No.

Top 

depth 

(m)

Bottom 

depth 

(m)

Sample 

identification 

No.

Sample type Stratigraphic 

unit symbol Description

ER–16–1 1,079.0 1,082.0 ER16–1(3540) Cuttings Dg Cuttings are dominated by fine-grained, black 

carbonate with graphite-like sheen on surfaces. 

Other lithologies are present, but were excluded 

from sample.

1,158.2 1,161.3 ER16–1(3800) Cuttings Dg Medium-sized cuttings contain a heterogeneous 

suite of rock types, though most are carbonate. 

Lithologies range from coarse-grained, marble-like 

material to fine-grained, dark grey material similar 

to ER16–1(3540). Bulk material used for powder 

sample with no further picking.

HTH–3 563.9 566.9 HTH–3(1850) Core fragments Op Fragments of equigranular, coarse-grained, mediumgrey dolomite with abundant fractures, some 

of which contain micro-breccia and fine, white 

secondary cement ± brown staining.

TW–C 444.4 444.4 TW–C(1458) Core Dg Medium-grained, grey limestone cut by numerous 

fractures filled with <1- to 5-mm-thick white 

secondary calcite veins. Minor red staining in 

some veins.

446.6 446.6 TW–C(1463.5) Core Dg Coarse-grained, mottled grey limestone with 

extensive secondary veining and recrystallization 

that yields solution-breccia textures in areas. 

Secondary calcite is white to brownish red.

TW–D 540.4 541.6 TW–D(1773) Cuttings Cn-d Massive, fine-to-medium-grained, grey limestone. 

Coarse cuttings have spotty, clay-like coating on 

fragment surfaces.

UE–1c 545.6 548.6 UE1c(1790) Coarse cuttings Op Coarse-grained, grey limestone. Several chips have 

fine-grained, brownish material that coat fracture 

surfaces or form thin veins.

566.9 570.0 UE1c(1860) Coarse cuttings Op Massive, fine-to-medium-grained, light pinkish to 

greenish brown limestone.

UE–1h 902.2 905.3 UE1h(2960) Cuttings Cn or Cb Coarse grained, white-to-light grey dolomite.

UE–2ce 438.9 442.0 UE2ce(1440) Cuttings Cn or Cb Coarse grained, white-to-light grey dolomite.

UE–7nS 625.5 625.5 UE7nS(2052.2) Core Op-av Mottled limestone consisting of medium-to-coarse 

grained, light-brown limestone with irregular 

patches of fine-grained, brownish-red alteration 

product.

667.5 667.5 UE7nS(2190) Core Op-av Mottled coarse-grained limestone. Patches of coarse, 

light grey limestone are separated by lenses and 

veins of finer-grained, iron-stained material.

UE–10j 393.2 394.7 UE10j(1290) Coarse cuttings Cn-s Massive, fine-to-medium-grained grey dolomite. 

Rock is highly fractured with very thin white, claylike material commonly present in fractures.

Table 3. Description of samples analyzed for strontium isotopic compositions from boreholes at the Nevada Test Site, Nye County, 

Nevada.—Continued

[Stratigraphic units are from lithology logs included in borehole completion reports to U.S. Department of Energy (see U.S. Geological Survey, 2006, for 

compilation of data and references, as well as Maldonado and others [1979], and Carr and others [1986]). Stratigraphic unit symbols are defined in table 1. Core 

and cutting samples were obtained in 2006 except for samples from boreholes UE–25 a #3 and UE–25 p #1, which were obtained in the early 1990s. Borehole 

depths are measured in feet below land surface. Abbreviations: DOE, Department of Energy; m, meter; mm, millimeter; >, greater than; <, less than; ±, plus or 

minus]

14  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
DOE borehole 

identification 

No.

Top 

depth 

(m)

Bottom 

depth 

(m)

Sample 

identification 

No.

Sample type Stratigraphic 

unit symbol Description

UE–10j 567.8 567.8 UE10j(1863) Core Cn-h Fine-grained, dark-grey dolomite with distinct 1-to5-mm-thick bedding-plane laminations defined 

by thin, light brown stylolitic planes and thicker 

planes of white secondary calcite. Thin veins with 

white calcite also cut across bedding.

625.1 625.1 UE10j(2051) Core Cn-d Uniform, brownish-red, marly shale with conchoidal 

fracturing along shaley partings. Fine crystals 

are apparent under magnification. Some fracture 

surfaces have additional red staining.

656.5 656.5 UE10j(2154) Core Cb-b Massive coarse-grained, white-to-light grey dolomite. 

Minor fractures contain light brown staining.

UE–15d 1,816.6 1,817.8 UE15d(5960) Core Zj or Zn Mostly medium-grained, grey dolomite with planar 

foliation defined by color streaks and grain 

elongation, but also patches of greenish white, 

coarse-grained dolomite breccia. Accessory pyrite 

present in both phases.

1,827.0 1,827.0 UE15d(5994) Core Zj or Zn Fine-grained, medium-grey dolomite with lightcolored spots of coarser carbonate. Scattered 

fractures are filled with white secondary carbonate.

UE–16d 311.0 313.9 UE16d(1020) Cuttings PPt Massive, fine-to-medium-grained, grey limestone.

472.4 475.5 UE16d(1550) Cuttings MDe Very coarse, white-to-light grey limestone 

concentrated from heterogeneous lithologies 

(including volcanic and fine-grained carbonates) in 

cuttings sample by extensive hand picking.

UE–25 a #3 43.3 43.4 UE25a3–142 Core Mc or MDg Dark grey, very-fine-grained shale/argillite.

98.9 99.0 UE25a3–324 Core Mc or MDg Dark grey, very-fine-grained shale/argillite.

150.4 150.5 UE25a3–493 Core Mc or MDg Dark grey, very-fine-grained shale/argillite.

208.4 208.5 UE25a3–684 Core Mc or MDg Dark grey, very-fine-grained shale/argillite.

263.0 263.1 UE25a3–863 Core Mc or MDg Dark grey, very-fine-grained shale/argillite.

325.7 325.9 UE25a3–1069 Core Mc or MDg Dark grey, very-fine-grained shale/argillite.

435.9 436.0 UE25a3–1430 Core Mc or MDg Light tannish-grey, thermally altered shale/argillite.

525.0 525.1 UE25a3–1722 Core Mc or MDg Light grey, thermally altered shale/argillite.

562.5 562.6 UE25a3–1846 Core Mc or MDg Light grey, thermally altered shale/argillite.

637.8 637.9 UE25a3–2093 Core Mc or MDg Light grey, coarse-grained metasandstone.

697.2 697.3 UE25a3–2287 Core Mc or MDg Light greenish-grey, calcareous argillite.

741.1 741.2 UE25a3–2432 Core Du Dark orange-yellow, ferruginous clay seam.

759.6 759.7 UE25a3–2492 Core Du White calcitic marble.

766.4 766.5 UE25a3–2514 Core Du Light grey, laminated marble.

UE–25 p #1 1,277.9 1,278.0 HD–622 Core DSlm Light grey, massive, pelloidal dolomite.

1,284.1 1,284.2 HD–621 Core DSlm Light grey, fine-grained, massive dolomite.

1,798.3 1,798.4 UE25p 1–5900 Core Sr Dark grey, fine-grained dolomite with thin lamellae.

Table 3. Description of samples analyzed for strontium isotopic compositions from boreholes at the Nevada Test Site, Nye County, 

Nevada.—Continued

[Stratigraphic units are from lithology logs included in borehole completion reports to U.S. Department of Energy (see U.S. Geological Survey, 2006, for 

compilation of data and references, as well as Maldonado and others [1979], and Carr and others [1986]). Stratigraphic unit symbols are defined in table 1. Core 

and cutting samples were obtained in 2006 except for samples from boreholes UE–25 a #3 and UE–25 p #1, which were obtained in the early 1990s. Borehole 

depths are measured in feet below land surface. Abbreviations: DOE, Department of Energy; m, meter; mm, millimeter; >, greater than; <, less than]

Analytical Methods 15
Samples from road cuts or outcrops were collected 

between 1989 and 1994 as part of a study to evaluate the 

usefulness of strontium isotopes as indicators of epithermal 

mineralization in areas surrounding Yucca Mountain, Nevada, 

the potential site for a geologic repository for high-level 

radioactive waste (Peterman and others, 1994). Samples of 

mineralized and unmineralized Paleozoic carbonate rocks 

were analyzed to represent geologic map units in several areas 

to the west, south, and east of the NTS (table 4; fig. 1). In 

addition, core samples from Paleozoic strata underlying the 

Tertiary volcanic rocks constituting Yucca Mountain (borehole 

UE-25 p #1) were included. 

Samples of NTS core were split and representative 

fragments were selected for further processing. Samples of 

cuttings were examined under a binocular microscope and 

fragments of foreign material likely representing down-hole 

contamination by rock fragments from overlying lithologic 

units were removed. Final samples of cuttings and core 

fragments weighed between 3 and 50 grams (g). Outcrop 

samples were trimmed as much as possible in the field to 

remove weathering rinds or coatings of pedogenic carbonate 

and were subsampled further in the laboratory using a 

small diamond core drill (1.3-centimeter outside diameter). 

Resulting unweathered core samples ranged from 10 to 

20 g. All samples were crushed and then pulverized to less 

than 0.075 millimeters using a steel shatterbox. All rock 

preparation and analyses were done by USGS Yucca Mountain 

Project Branch personnel in Denver, Colorado, between 1990 

and 2006.

Analyses of the recently acquired NTS borehole samples 

were made on partial digestions (leachates) obtained by adding 

approximately 20 milliliters of 0.2 molar nitric acid to 0.1 g 

of rock powder. Acid solutions were allowed to react with 

rock powders in a 50°C incubator oven for 12 to 24 hours. 

Acid volumes were sufficient to maintain low pH in the final 

leachate solutions. Leachates then were analyzed for a selected 

suite of major and trace constituents (MgO, CaO, SiO2

, Al2O3, 

MnO, Rb, Sr, Th, and U) by inductively coupled plasma mass 

spectrometry (ICP-MS). Strontium was purified from the 

same leachates using Eichrom Sr-SPECTM resin and 87Sr/86Sr 

isotopic compositions were measured using a Finnigan MAT 

262TM multiple-collector thermal-ionization mass spectrometer 

operating in static mode. The instrument was calibrated 

using the USGS rock standard EN-1 (calcite from a modern 

Tridacna shell from Enewetok Lagoon in the western Pacific 

Ocean; Ludwig and others, 1988). To correct for instrument 

drift and eliminate small interlaboratory biases (Faure and 

Mensing, 2005, p. 78), measured 87Sr/86Sr values for samples 

in each magazine were normalized to the value obtained 

from the EN-1 standard measured in the same magazine and 

adjusted to an assigned value of 0.70920 for modern mean 

ocean water (Elderfield, 1986, p. 77). Replicate 87Sr/86Sr 

analyses of the uncorrected EN-1 standard varied by less than 

±0.00005 (0.007 percent) at the 95-percent confidence level 

(2-sigma). Results for the National Institute of Standards 

and Technology strontium carbonate standard, SRM 987, 

(accepted 87Sr/86Sr value of 0.71025; Faure and Mensing, 

2005, p. 79) analyzed between 1997 and 2006 yielded a 

weighted average 87Sr/86Sr value of 0.710270 ±0.000011 (95-

percent confidence limit) indicating that estimates of accuracy 

and precision are similar. Sr contributions from the chemical 

procedure (blank) were approximately 2×10-9 g, which are 

5–7 orders of magnitude lower than the total amount of Sr 

contributed from the samples. 

Rock powders from outcrop samples were analyzed 

before ICP-MS capabilities became available. Instead, selected 

elements (Rb, Sr, Y, Zr, Nb, Ba, La, and Ce) were analyzed by 

energy-dispersive XRF (X-ray fluorescence) spectroscopy on 

bulk rock powders. Results for the rock-forming constituents 

MgO and CaO are not available. 87Sr/86Sr was analyzed in the 

carbonate fraction by dissolving subgram powdered aliquots in 

1 molar hydrochloric acid followed by purification of Sr using 

cation exchange resins. 87Sr/86Sr values were measured using 

either the instrument described in the previous paragraph, or 

on one of two single collector instruments (National Bureau of 

Standards instrument or VG Isomass 54E) operating in peakhopping mode. The measurements were treated identically 

to those described above using results of EN-1 to normalize 

unknown 87Sr/86Sr values. Samples of drill core obtained in 

the early 1990’s from UE-25 p #1 (fig. 1B) were processed in 

the same manner as outcrop samples. Samples of Gap Wash 

Formation siliciclastic rocks (Eleana Formation equivalent; 

Trexler and others, 2003) from UE-25 a #3 (fig. 1B) as well 

as two of the outcrop samples (HD-1107 and HD-1114 with 

respective Map No. 4 and 5 in table 4) were digested using 

hydrofluoric and sulfuric acids prior to Sr purification.

To emphasize small but significant variations in 87Sr/86Sr, 

data also are reported as per mil (‰) deviations from modern 

seawater (87Sr/86Sr = 0.70920) using the equation

δ87

87 86

0 70920

Sr 1 1 000 Sr Sr unknown = − 



 



 ×

/

. , . (1)

Analytical uncertainties in δ87Sr values are typically 

less than ±0.07 per mil at the 95-percent confidence level. 

Although modern seawater provides a useful reference point 

for comparative purposes, it is desirable to know whether 

present-day 87Sr/86Sr compositions of the marine carbonate 

rocks have been modified from seawater 87Sr/86Sr compositions 

that were present at the time of deposition. Therefore, δ87Srt

values are computed using stratigraphic age assignments and 

paleoseawater 87Sr/86Sr compositions using the equation,

δ 87

t

87 86

unknown

87 86

paleoseawater

Sr Sr Sr

Sr Sr = −1 1, 













 × 000, (2)

where 87Sr/86Srpaleoseawater is derived from figure 3 and the 

stratigraphic ages listed in table 1. Explicit uncertainties for 

δ87Srt are not given in this report because of the difficulty in 

defining uncertainties to the age assignments. However, they 

are expected to be as much as an order of magnitude larger 

than those for δ87Sr. 

16  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Map

No.

Sample

identification

No.

Area Locality

UTM

Easting

(m)

UTM

Northing

(m)

Stratigraphic 

unit

Description

1 HD–1106 Funeral Mountains Chloride City 510,520 4,061,767 ZYb Calcitic marble.

2 HD–1111 Funeral Mountains Chloride City 510,222 4,061,921 ZYc Coarse-grained, thinly bedded marble.

3 HD–1112 Funeral Mountains Chloride City 510,222 4,061,921 ZYc Coarse-grained, thinly bedded marble.

4 HD–1107 Funeral Mountains Chloride City 510,869 4,060,843 ZYb Coarse-grained, thinly laminated 

dolomite with graphite layers.

5 HD–1114 Funeral Mountains Chloride City 510,271 4,062,537 ZYc Light grey, fine-grained, saccharoidal 

marble.

6 HD–1105 Funeral Mountains East of Chloride 

City

511,883 4,063,433 Zs-c Purple grey dolomite; weathers to reddish 

brown.

7 HD–1151 Bare Mountain Beatty 521,387 4,081,908 CZw Buff, thinly banded limestone 

interbedded with quartzite beds.

8 3C–1 Bare Mountain Black Marble Hill 533,950 4,066,327 Cb Not available.

9 HD–212 Bare Mountain Black Marble Hill 533,424 4,067,650 Cb Dolomite.

10 HD–214 Bare Mountain Black Marble Hill 533,424 4,067,650 Cb Intact dolomite.

11 HD–216 Bare Mountain Black Marble Hill 533,424 4,067,650 Cb Intact dolomite.

12 HD–218 Bare Mountain Black Marble Hill 533,424 4,067,650 Cb Intact dolomite.

13 HD–219 Bare Mountain Black Marble Hill 533,424 4,067,650 Cb Intact dolomite.

14 HD–220 Bare Mountain Black Marble Hill 533,424 4,067,650 Cb Bleached/tan dolomite.

15 HD–221 Bare Mountain Black Marble Hill 533,424 4,067,650 Cb Intact dolomite.

16 HD–1154 Bare Mountain Carrara Canyon 528,539 4,074,996 CZw-u Chocolate-brown, well-bedded limestone.

17 HD–1155 Bare Mountain Carrara Canyon 528,613 4,075,089 CZw Chocolate-brown, well-bedded limestone.

18 HD–538 Bare Mountain Carrara Canyon 529,207 4,075,399 Cb-p Very light grey, fine-to-medium grained 

calcitic marble.

19 HD–539 Bare Mountain Carrara Canyon 529,330 4,075,615 Cb-p Medium-to-dark grey fine-grained 

mottled dolomite with laminated 

texture and intervals containing 

partings of light brown silty dolomite.

20 HD–540 Bare Mountain Carrara Canyon 529,157 4,075,584 Cb-p Mottled dark and light grey, fine-grained 

dolomite.

21 HD–541 Bare Mountain Carrara Canyon 528,539 4,074,996 CZw-u Light brown, medium grained calcitic 

marble with minor grains of quartz 

sand.

22 HD–513 Bare Mountain Chuckwalla Canyon 531,820 4,078,706 Oes Medium grey, recrystallized dolomite 

with laminae of secondary chert.

23 HD–515 Bare Mountain Chuckwalla Canyon 531,845 4,078,860 Oes Medium light grey, fine-grained 

recrystallized dolomite.

24 HD–516A Bare Mountain Chuckwalla Canyon 531,844 4,078,891 Sr Medium dark grey, laminated, 

recrystallized dolomite.

25 HD–517 Bare Mountain Chuckwalla Canyon 531,795 4,078,983 Sr Medium grey, laminated, fine-grained 

recrystallized limestone.

26 HD–518 Bare Mountain Chuckwalla Canyon 531,794 4,079,106 Sr Medium grey, fine-grained, crystallized 

dolomite with sparse lenses of chert 

and calcified macrofossils.

Table 4. Locations, stratigraphic unit designations, and descriptions of outcrop samples analyzed for strontium isotopic compositions 

from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California.

[Map numbers are used to locate sites in figure 1. Stratigraphic units are from geologic maps listed in the text. Stratigraphic unit symbols are defined in 

table 1. Abbreviations: cm, centimeter; m, meter; UTM, Universal Transverse Mercator]

Analytical Methods 17
Table 4. Locations, stratigraphic unit designations, and descriptions of outcrop samples analyzed for strontium isotopic compositions 

from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California.—Continued

[Map numbers are used to locate sites in figure 1. Stratigraphic units are from geologic maps listed in the text. Stratigraphic unit symbols are defined in 

table 1. Abbreviations: cm, centimeter; m, meter; UTM, Universal Transverse Mercator]

Map

No.

Sample

identification

No.

Area Locality

UTM

Easting

(m)

UTM

Northing

(m)

Stratigraphic 

unit

Description

27 HD–519 Bare Mountain Chuckwalla Canyon 531,769 4,079,137 DSlm Very light grey, fine-grained 

recrystallized dolomite.

28 HD–520 Bare Mountain Chuckwalla Canyon 531,944 4,078,644 DSlm Light grey, fine-grained dolomite with 

white dolomitic mottling and crinoid 

debris.

29 HD–533 Bare Mountain Diamond Queen 

Mine

532,270 4,077,721 Op-av Mottled light-to-medium grey, finegrained limestone with massive texture 

and veins of pinkish grey carbonate.

30 HD–534 Bare Mountain Diamond Queen 

Mine

532,271 4,077,536 Op-g Medium light grey thin-bedded limestone 

with irregular light-brown silty 

partings.

31 HD–535 Bare Mountain Diamond Queen 

Mine

532,372 4,076,951 Cn-s Medium light grey, fine-to-medium 

grained recrystallized dolomite with 

massive texture.

32 HD–1415 Bare Mountain Fluorspar Canyon 523,463 4,083,239 Cb-p Unaltered carbonate.

33 HD–1416 Bare Mountain Fluorspar Canyon 523,488 4,083,177 Cb-p Unaltered carbonate.

34 HD–1417 Bare Mountain Fluorspar Canyon 522,993 4,083,084 CZw-l Lower member, Unit D.

35 HD–1418 Bare Mountain Fluorspar Canyon 522,919 4,083,114 CZw-l Lower member, Unit D.

36 HD–1419 Bare Mountain Fluorspar Canyon 522,968 4,083,145 Cb-p Unaltered carbonate.

37 HD–1420 Bare Mountain Fluorspar Canyon 522,893 4,083,237 Cb-p Unaltered carbonate.

38 HD–1421 Bare Mountain Fluorspar Canyon 522,745 4,083,114 CZw-l Lower member, Unit D; Sandy brown 

limey quartzite.

39 HD–527 Bare Mountain Fluorspar Canyon 528,094 4,082,390 Df Light grey, fine-grained recrystallized 

dolomite. Brecciated with local 

cementation of thin silica veinlets.

40 HD–528 Bare Mountain Fluorspar Canyon 527,798 4,081,927 Df Light-to-dark grey, fine-grained dolomite 

laced with boxwork of white dolomite 

veinlets.

41 HD–529 Bare Mountain Fluorspar Canyon 526,562 4,081,492 Cb-b Very light grey, fine- to medium-grained 

calcitic marble.

42 HD–530 Bare Mountain Fluorspar Canyon 526,562 4,081,584 Cb-b Medium light grey, fine-grained 

dolomitic marble.

43 HD–531 Bare Mountain Fluorspar Canyon 526,636 4,081,677 Cn-h Medium-to-dark grey, fine-grained 

calcitic marble with thin layers of 

dolomitic marble and olive-grey chert.

44 HD–542 Bare Mountain Fluorspar Canyon 523,018 4,082,868 CZw-l Pale orange, fine-grained dolomitic 

marble.

45 HD–543 Bare Mountain Fluorspar Canyon 523,883 4,083,271 Cb-p Light grey, fine-grained dolomitic marble.

46 HD–1152b Bare Mountain Gold Ace Mine 526,504 4,076,346 Zs-d Altered limestone with solution 

boxworks.

47 HD–1153 Bare Mountain Gold Ace Mine 526,653 4,076,161 Zs-d Buff (weathered) to grey (fresh) siliceous 

limestone.

48 HD–1142 Bare Mountain Secret Pass 529,582 4,081,471 Op-g Grey, thinly bedded limestone.

49 HD–1144 Bare Mountain Secret Pass 529,359 4,081,439 Df Medium grey, fairly massive, highly 

fractured limestone.

18 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Table 4. Locations, stratigraphic unit designations, and descriptions of outcrop samples analyzed for strontium isotopic compositions 

from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California.—Continued

[Map numbers are used to locate sites in figure 1. Stratigraphic units are from geologic maps listed in the text. Stratigraphic unit symbols are defined in 

table 1. Abbreviations: cm, centimeter; m, meter; UTM, Universal Transverse Mercator]

Map

No.

Sample

identification

No.

Area Locality

UTM

Easting

(m)

UTM

Northing

(m)

Stratigraphic 

unit

Description

50 HD–1400 Bare Mountain Sterling Mine 532,006 4,075,440 Cb-b Unaltered carbonate.

51 HD–1401 Bare Mountain Sterling Mine 532,006 4,075,440 Cb-b Unaltered carbonate.

52 HD–1402 Bare Mountain Sterling Mine 532,006 4,075,440 Cb-b Unaltered carbonate.

53 HD–641 Bare Mountain Sterling Mine 532,057 4,075,132 Cb-b Country rock adjacent to “red ore”.

54 HD–537 Bare Mountain Steves Pass 533,101 4,067,802 Zs-d Light brown, fine-to-medium grained 

recyrstallized dolomite.

55 HD–1146 Bare Mountain Tarantula Canyon 531,147 4,080,121 MDe Thin-bedded limestone consisting of 

rusty brown layers that are more 

resistant to weathering than medium 

grey limestone.

56 HD–1147a Bare Mountain Tarantula Canyon 532,039 4,079,908 Dtc Massive medium grey limestone with 

reddened zones, especially along 

fractures and bedding planes.

57 HD–1147b Bare Mountain Tarantula Canyon 532,039 4,079,908 Dtc Massive medium grey limestone with 

reddened zones, especially along 

fractures and bedding planes.

58 HD–522 Bare Mountain Tarantula Canyon 532,806 4,080,034 Dtc Very light-grey, fine-grained dolomite.

59 HD–523 Bare Mountain Tarantula Canyon 532,681 4,080,188 Dtc Medium-to-dark grey, fine-grained 

limestone with sparse chert nodules 

and minor calcite veins.

60 HD–526 Bare Mountain Tarantula Canyon 530,106 4,080,425 Cc-m Medium grey, fine-grained limestone 

mottled with light-olive-grey silty 

dolomite and cut by thin crystalline 

calcite veins.

61 HD–1138 Bare Mountain Telluride Mine 531,008 4,084,064 Op-av Medium grey, thinly bedded limestone 

with numerous secondary calcite 

vieins.

62 HD–1139 Bare Mountain Telluride Mine 530,935 4,083,971 DSlm Massive to brecciated dolomite and 

limestone.

63 HD–1141 Bare Mountain Telluride Mine 531,234 4,083,387 Op-av Thinly bedded limestone with 2- to 

6-cm-thick layers of alternating 

medium grey and greyish tan beds.

64 HD–1150b Bare Mountain Tungsten Canyon 530,850 4,073,217 CZw Orange-weathering carbonate.

65 HD–546 Striped Hills Outlier on west side 556,896 4,057,913 Dn Light-to-medium grey, fine-grained 

massive dolomite with mottling 

and brecciation. Light red ion oxide 

coatings on fracture surfaces.

66 HD–548 Striped Hills West side 559,200 4,058,576 Op-av Medium- to dark-grey, rusty-weathering, 

silty limestone.

67 HD–549 Striped Hills West side 559,152 4,058,390 Op-g Medium- to dark-grey limestone 

containing thin rusty-weathered lenses 

and fractures.

68 HD–550 Striped Hills West side 559,177 4,058,298 Op-g Medium- to dark-grey, very fine-grained 

limestone containing tan to pinkish 

grey silty laminae.

Analytical Methods 19
Table 4. Locations, stratigraphic unit designations, and descriptions of outcrop samples analyzed for strontium isotopic compositions 

from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California.—Continued

[Map numbers are used to locate sites in figure 1. Stratigraphic units are from geologic maps listed in the text. Stratigraphic unit symbols are defined in 

table 1. Abbreviations: cm, centimeter; m, meter; UTM, Universal Transverse Mercator]

Map

No.

Sample

identification

No.

Area Locality

UTM

Easting

(m)

UTM

Northing

(m)

Stratigraphic 

unit

Description

69 HD–551A Striped Hills West side 558,739 4,057,093 Op-g Medium-grey, medium-grained dolomite 

with red staining on microfractures.

70 HD–553 Striped Hills West side 558,959 4,057,557 Cn-h Medium- to dark-grey, very fine-grained 

limestone containing fractures with 

red-stained coatings on fractures.

71 HD–554 Striped Hills West side 558,835 4,057,464 Cb-b Light- and dark-grey, medium grained 

limestone with reddish iron oxide 

coatings on fracture surfaces.

72 HD–555 Striped Hills West side 558,168 4,057,028 Cb-b Medium-to-dark grey, very fine-grained 

limestone containing fractures with 

red-stained coatings on fractures.

73 HD–556 Striped Hills West side 558,145 4,056,781 Cb-b Light-to-medium grey, fine- to mediumgrained limestone with thin fractures of 

secondary calcite.

74 HD–557 Striped Hills West side 558,099 4,056,288 Cb-p Light-to-medium grey, medium-grained 

limestone with mottling and buff to 

light grey coatings on fracture surfaces.

75 HD–558 Striped Hills West side 558,025 4,056,164 Cb-p Mottled medium grey, fine-grained 

laminated limestone with patches 

of reddish iron oxide and white 

crystalline calcite.

76 HD–1422–1 Specter Range Rock Valley Wash 562,215 4,053,605 Cb-b Altered carbonate.

77 HD–1422–2 Specter Range Rock Valley Wash 562,215 4,053,605 Cb-b Altered carbonate.

78 HD–1423 Specter Range Rock Valley Wash 562,191 4,053,512 Cb-b Unaltered carbonate.

79 HD–1426 Specter Range Central 569,490 4,053,907 CZw Rusty-weathering dolomitic quartzite.

80 HD–1427 Specter Range Central 571,247 4,057,681 Cb-b Upper Bonanza King Formation with 

possible mineralization and thin rustycolored veins throughout.

81 HD–1428 Specter Range Central 570,884 4,056,569 Cb-b Light grey massive carbonate.

82 HD–1429 Specter Range Central 569,881 4,054,743 Cb-p Lower Bonanza King carbonate.

83 HD–1432 Specter Range Central 570,824 4,048,741 DSu Medium grey, porous carbonate.

84 HD–1434 Specter Range Point of Rocks Area 579,083 4,050,601 Dsv Brecciated carbonate.

85 HD–1435 Specter Range Point of Rocks Area 580,589 4,049,012 Cb Massive white marble.

86 HD–1436 Specter Range Point of Rocks Area 582,172 4,047,178 Cb-b Unaltered carbonate.

87 HD–110–1 Devils Hole Hills Above Devils Hole 563,572 4,031,182 Cb-b Dark grey limestone.

88 HD–471B Devils Hole Hills Above Devils Hole 563,448 4,031,120 Cb-b Unaltered carbonate.

89 GDR–8 Spring Mountains Cold Creek Spring 613,012 4,027,188 Cu Unaltered carbonate.

90 HD–229 Spring Mountains Lower Lee Canyon 634,380 4,031,346 PMbl Well bedded limestone with alternating 

medium grey and more weatherresistant medium tan layers.

91 HD–230 Spring Mountains Lower Lee Canyon 628,327 4,029,589 PMbl Thick-bedded-to-massive tan limestone.

20 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Table 4. Locations, stratigraphic unit designations, and descriptions of outcrop samples analyzed for strontium isotopic compositions 

from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California.—Continued

[Map numbers are used to locate sites in figure 1. Stratigraphic units are from geologic maps listed in the text. Stratigraphic unit symbols are defined in 

table 1. Abbreviations: cm, centimeter; m, meter; UTM, Universal Transverse Mercator]

Map

No.

Sample

identification

No.

Area Locality

UTM

Easting

(m)

UTM

Northing

(m)

Stratigraphic 

unit

Description

92 HD–231 Spring Mountains Lower Lee Canyon 627,318 4,028,773 Mm Medium grey, massive limestone.

93 HD–232 Spring Mountains Upper Lee Canyon 620,905 4,022,271 Cb-b Highly fractured, medium grey limestone 

with some silty layers.

94 HD–233 Spring Mountains Upper Lee Canyon 619,928 4,020,839 Cb-b White -to-light buff, coarse-grained 

limestone.

95 HD–235 Spring Mountains Upper Lee Canyon 618,762 4,018,574 Cn White-to-light buff, coarse-grained, thinly 

laminated limestone.

96 HD–236 Spring Mountains Upper Lee Canyon 622,300 4,022,414 Op Medium grey, poorly bedded limestone 

with high degree of fracturing.

97 HD–238 Spring Mountains Kyle Canyon 637,123 4,015,392 PMb Light grey, thick bedded-to-massive 

limestone that weathers to light buff.

98 HD–1000 Sheep Range Black Hills 649,365 4,049,285 Dg Light-grey, thickly bedded limestone with 

tension-gash veins common.

99 HD–999 Sheep Range Black Hills 646,898 4,048,163 Cn-s Black, fine-grained laminated dolomite.

100 HD–995 Pintwater Range Southern end 625,873 4,049,217 Oes Dark-black, fine-grained dolomite with 

local cherty layers.

101 HD–996 Pintwater Range Southern end 626,955 4,051,698 Op-av Dolomitized limestone with layers of 

nodular chert.

102 HD–997 Pintwater Range Southern end 628,655 4,054,344 Oes Black, fine-grained laminated dolomite, 

locally brecciated.

103 HD–998 Pintwater Range Southern end 627,652 4,054,945 Op-av Medium grey limestone with abundant 

bioturbation and macrofossils.

104 HD–1001 Pintwater Range Northeast side 631,216 4,089,675 Op-av Brownish, locally dolomitized limestone

105 HD–1006 Pintwater Range Northwest side 621,872 4,094,313 Op-av Grey limestone.

106 HD–990 Indian Springs 

Valley

Nellis Air Force 

Base

619,875 4,051,504 Op-av Dark grey limestone.

107 HD–1002 Indian Springs 

Valley

Central 623,337 4,069,985 Oes Medium grey to tan, coarsely 

saccharoidal dolomite.

108 HD–991 Indian Springs 

Valley

West side 614,367 4,054,604 Oes Black, fine-grained dolomite.

109 HD–993 Spotted Range Eastern side 610,588 4,058,715 Dsi Grey, medium-grained dolomite.

110 HD–994 Spotted Range Central 607,444 4,061,911 Mj Black, coarse-grained limestone with 

abundant crinoid debris.

111 HD–1004 Spotted Range Northeast side 618,367 4,070,685 Op-av Grey limestone with local silty 

laminations.

112 HD–1003 Spotted Range Northeast side 620,405 4,075,645 Dg Dark grey, fine-grained, massive 

limestone.

113 HD–1007 Yucca Flat North end Eleana 

Range

574,337 4,115,797 Op-g Medium grey, fossiliferous, thin-bedded 

limestone.

114 HD–1008 Yucca Flat North end Eleana 

Range

572,367 4,115,472 Dsv Dark grey, medium-grained, thick-bedded 

dolomite.

Analytical Methods  21
Major and Trace Element Chemistry

Most of the borehole samples (34 of 48) were readily 

soluble losing 90.9 to 100 percent of their original sample 

weight during the 0.2 molar nitric acid treatment (table 5). 

The remaining 14 samples lost between 4.1 and 86.8 percent 

of the original sample weight. The greater amounts of residue 

in these samples are assumed to consist mostly of silicate 

material. Most samples were readily identifiable as limestone 

or dolomite, based on their CaO and MgO contents (diamonds 

on fig. 4). Assuming that all of the dissolved CaO and MgO 

is derived from the carbonate fraction, calcite (CaCO3) mole 

percentages vary from 93.2 to 99.6 percent in limestone 

samples and 48.0 to 53.6 percent in most dolomite samples. 

A small number of samples have intermediate MgO contents, 

resulting in calcite mole percentages between 55.6 and 74.2 

percent. These values exceed the amount of calcite that can 

substitute into the dolomite crystal structure (Gaines and 

others, 1997, p. 450). The resulting linear trend between 

calcite and dolomite stoichiometric end members indicates that 

these samples represent mixtures of the two phases. Samples 

with intermediate compositions include core, cuttings, and a 

discrete sample of sparry vein carbonate [Army#1(982) B]. 

This observation indicates that excess CaCO3

 contents are 

intrinsic to some dolomite samples and are not the result of 

down-hole mixing of cutting fragments. 

15

20

25

30

35

40

45

50

55

60

0 5 10 15 20 25

MAGNESIUM OXIDE (MgO) CONCENTRATION, (WT. %)

CALCIUM OXIDE (CaO) CONCENTRATION, (WT. %)

Stoichiometric calcite

56.03 wt. % CaO

0 wt. % MgO

Stoichiometric dolomite

30.41 wt. % CaO

21.86 wt. % MgO

UE10j(2051)

ER16-1(3450)

ER16-1(3800)

ER6-2(1830)

ER5-3#2(4780)

ER12-1(1720)

Army#1(1951)

Army#1(982)B

Army#1(862)

UE16d(1550)

TW-C(1458)

TW-D(1773)

LEACHATES WITH SiO2 LESS THAN 5 WEIGHT PERCENT (WT. %)

LEACHATES WITH SiO2 GREATER THAN 5 WT. %

MIXING LINE BETWEEN CALCITE AND DOLOMITE

Figure 4. Relation between magnesium oxide (MgO) and calcium oxide (CaO) concentrations in acid leachates of 

borehole samples, Nevada Test Site, Nye County, Nevada. Sample descriptions and data are from tables 3 and 5. 

Error bars represent 2-sigma analytical uncertainty and are shown as 5 percent of the reported concentration value. 

22  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Table 5. Oxide and elemental concentrations and strontium isotopic compositions (87Sr/86Sr) of nitric-acid leachates of core samples 

from boreholes at the Nevada Test Site, Nye County, Nevada.

[Results are for samples collected and analyzed in 2006. Oxide concentrations are given in weight percentages, and elemental concentrations are given in 

micrograms per gram. The less than (<) symbol is used to indicate concentrations that are below minimum reporting limits and incorporate the measured dilution 

factors for each sample; the greater than (>) symbol is used to indicate concentrations that are above the range of standards used to define the calibration curve. 

Uncertainties for strontium isotopic compositions (87Sr/86Sr) are dominated by external errors for replicate analyses of the Sr isotope standard EN-1, therefore, a 

blanket 87Sr/86Sr uncertainty of 0.00005 is reported. Strontium isotopic compositions also are given in delta notation (δ87Sr = [(87Sr/86Srsample/

87Sr/86Srmsw)-1]

×1,000 and δ87Srt = [(87Sr/86Srsample/

87Sr/86Srpsw)-1]×1,000, where 87Sr/86Srmsw is the value for modern seawater and 87Sr/86Srpsw is the value for paleoseawater at the 

time of deposition). Abbreviations: MgO, magnesium oxide; CaO, calcium oxide; CaCO3, calcium carbonate (calcite); SiO2, silicon dioxide; Al2O3, aluminum 

oxide; MnO, manganese oxide; Rb, rubidium; Sr, strontium; Th, thorium; U, uranium; ‰, permil]

Sample

identification 

No.

Percent 

sample 

dissolved

MgO CaO

Mole 

percent 

CaCO3

SiO2 Al2O3 MnO Rb Sr Th U

87

Sr/86Sr 

(±0.00005

2σ)

δ87

Sr, ‰ 

(±0.07 2σ)

δ87Srt, 

‰

Seawater 

87

Sr/86Srpsw 

used

Army 1(859) 98.8 22.7 31.3 49.8 0.21 0.02 0.016 <0.79 30.4 <0.23 <0.23 0.70856 -0.90 -0.62 0.7090

Army 1(862) 69.2 18.2 31.8 55.6 1.69 1.10 .017 6.73 69.6 4.02 .55 .71132 2.99 3.27 .7090

Army 1(982)A 97.9 22.9 30.2 48.7 .22 .01 .026 < .87 30.7 < .26 < .26 .71027 1.51 1.65 .7091

Army 1(982)B 98.5 17.4 36.2 59.9 .23 .02 .018 < .88 37.9 < .26 < .26 .71023 1.45 1.59 .7091

Army 1(1112) 33.5 .81 44.4 97.5 3.14 1.85 .260 11.3 364 20 < .88 .71098 2.50 2.64 .7091

Army 1(1951) 100.0 15.5 37.4 63.3 .19 .01 .005 < .75 107 < .23 .28 .70935 .22 .22 .7092

ER3–1(2280) 98.8 2.6 50.0 93.2 < .20 .02 .027 < .94 543 < .28 < .28 .70958 .54 .54 .7092

ER3–1(2580) 99.7 1.1 49.3 96.9 < .22 .01 .004 <1.04 243 < .31 < .31 .70935 .20 .20 .7092

ER5–3 2(4780) 99.4 17.2 35.0 59.3 < .20 .03 .014 < .93 79.4 < .27 < .27 .71084 2.32 3.17 .7086

ER6–1 2(2170) 99.1 23.0 30.5 48.8 < .20 .02 .011 < .95 60.2 < .28 .75 .70809 -1.57 - .02 .7082

ER6–1 2(2630) 100.0 23.0 30.6 48.9 < .17 .01 .015 < .80 53.2 < .24 .54 .70816 -1.47 - .06 .7082

ER6–1 2(2830) 100.0 22.9 29.8 48.4 < .19 .01 .012 < .89 44.5 < .26 .41 .70825 -1.33 .08 .7082

ER6–1 2(2990) 95.6 23.0 30.4 48.6 .27 .06 .018 < .90 77.1 < .28 1.53 .70851 - .98 .01 .7085

ER6–2(1830) 79.3 16.0 31.5 58.6 1.55 > .97 .038 7.28 140 2.29 < .30 .71227 4.33 4.47 .7091

ER6–2(2129) 96.9 21.7 32.9 52.1 .54 < .08 .026 .88 70.5 < .26 < .26 .70854 - .92 - .50 .7089

ER6–2(2379) 97.7 21.1 33.9 53.6 .47 < .08 .014 < .84 47.0 < .26 .59 .71042 1.73 2.15 .7089

ER6–2(2613) 98.0 .71 51.4 98.1 .39 .01 .005 <1.02 103 < .29 .66 .70897 - .33 .94 .7083

ER6–2(2721.5) 98.5 .95 50.8 97.5 .36 < .08 .006 < .80 97.6 < .25 .33 .71103 2.58 3.86 .7083

ER7–1(2150) 90.9 .59 56.0 98.5 < .24 .03 .007 <1.12 425 < .34 .39 .70889 - .44 - .01 .7089

ER7–1(2390) 96.9 .49 55.5 98.8 < .18 .02 .004 < .86 452 .38 .36 .70884 - .50 - .08 .7089

ER12–1(1720) 51.2 18.2 36.1 58.7 .68 .45 .053 4.78 297 1.94 2.14 .71406 6.86 8.70 .7079

ER12–1(3340) 97.5 23.2 31.8 49.6 < .21 .01 .016 < .96 40.1 < .29 1.12 .71013 1.32 3.15 .7079

ER12–3(3620) 97.4 22.7 31.3 49.8 < .18 < .08 .012 < .84 105 < .25 .30 .70908 - .16 .26 .7089

ER12–3(4490) 77.3 .70 53.7 98.2 1.01 .31 .015 2.08 1,190 .67 2.54 .70937 .24 .24 .7092

ER12–3(4840) 72.1 1.10 53.0 97.2 1.29 > .45 .037 3.89 1,420 .83 5.43 .70928 .11 .11 .7092

ER12–4(2580) 97.9 22.1 30.6 50.0 .66 .18 .036 3.91 146 .30 .29 .71215 4.16 4.73 .7088

ER12–4(3450) 95.0 20.9 33.0 53.2 1.81 > .37 .018 21.5 113 .33 .49 .71007 1.23 2.93 .7080

ER12–4(3590) 98.0 21.4 32.0 51.8 1.77 .41 .020 6.27 133 < .33 < .33 .70847 -1.03 - .04 .7085

ER16–1(3540) 21.9 10.2 26.3 65.0 9.33 >1.50 .179 49.5 327 13.0 3.43 .71485 7.97 9.25 .7083

ER16–1(3800) 69.8 15.2 38.9 64.8 1.36 .33 .036 3.94 70.7 .88 1.55 .71084 2.32 4.16 .7079

HTH–3(1850) 99.0 21.6 30.5 50.4 .19 .01 .009 < .89 16.9 < .26 .29 .70872 - .68 .02 .7087

TW–C(1458) 100.0 10.6 42.4 74.2 .32 .06 .014 < .80 251 < .23 .25 .71072 2.15 3.42 .7083

TW–C(1463.5) 99.5 .99 51.49 97.4 .21 .03 .005 < .96 261 < .28 < .28 .71140 3.10 4.38 .7083

TW–D(1773) 86.8 10.7 40.6 73.2 .51 .18 .052 1.66 454 1.02 .51 .70939 .27 .27 .7092

UE1c(1790) 97.0 .27 51.6 99.3 .23 .03 .005 < .95 405 .63 .74 .70879 - .58 - .02 .7088

UE1c(1860) 77.5 1.15 50.1 96.9 1.02 .44 .150 3.75 327 2.04 .66 .70945 .35 .63 .7090

UE1h(2960) 99.8 22.1 30.5 49.9 .21 .01 .012 <1.00 46.5 < .31 .76 .70811 -1.54 -1.40 .7091

UE2ce(1440) 100.0 21.6 30.5 50.4 .22 .03 .015 < .94 24.3 < .29 < .29 .70854 - .94 - .09 .7086

UE7nS(2052.2) 56.6 .21 52.3 99.4 .65 .26 .050 1.68 292 3.9 .57 .71111 2.70 3.12 .7089

UE7nS(2190) 80.3 .17 52.2 99.6 .39 .10 .036 <1.04 276 .93 .4 .71134 3.02 3.30 .7090

UE10j(1290) 98.3 22.9 29.8 48.4 < .18 .02 .015 < .82 39.2 < .24 < .24 .70870 - .71 - .42 .7090

UE10j(1863) 94.1 22.9 29.4 48.0 .21 .04 .023 < .89 64.9 < .26 .83 .70862 - .82 - .53 .7090

UE10j(2051) 24.5 11.5 19.0 54.4 9.28 >3.87 .170 58 299 27.2 <1.21 .72089 16.49 16.49 .7092

UE10j(2154) 98.9 22.7 29.8 48.5 < .18 .02 .099 < .83 35 < .24 < .24 .70873 - .66 - .52 .7091

UE15d(5960) 97.3 21.6 31.2 51.0 .32 .10 .015 < .80 34.2 < .25 1.19 .71300 5.36 6.49 .7084

UE15d(5994) 96.1 20.4 30.9 52.1 .59 .17 .010 1.96 37.4 <.25 <.25 .71370 6.34 7.48 .7084

UE16d(1020) 98.9 .60 47.0 98.3 .26 .04 .001 <1.02 1,680 < .30 2.18 .70828 -1.30 - .03 .7083

UE16d(1550) 4.1 <1.89 31.5 96.0 6.23 1.68 .234 <22.9 660 <7.04 <7.04 .70889 - .43 .84 .7083

Major and Trace Element Chemistry  23
In contrast, three leachate samples with 0.95 to 11.5 

weight percent MgO concentrations plot off the calcitedolomite mixing trend and have elevated SiO2

 concentrations 

compared to other carbonate leachates (solid squares, fig. 4). 

These leachates —ER16-1 (3540), UE10j (2051), and UE16d 

(1550)— also had the lowest percent-sample-dissolved values 

(4.1 to 24.5 percent) and contained noticeable clay or volcanic 

constituents. These observations indicate that chemical 

compositions of these leachates are not derived exclusively 

from carbonate components and likely include ions leached 

from silicate minerals. 

Measurable amounts of SiO2 and Al2O3 in leachates 

indicates that small amounts of clay minerals may be present 

in many of the carbonate samples. The positive correlation 

between SiO2 and Al2O3 concentrations with a SiO2:Al2O3

weight ratio of 2:1 (fig. 5A) could be the result of variable 

amounts of clay minerals mixed in with the marine carbonate 

rocks. Systematic differences in SiO2

 concentrations between 

dolomite and limestone samples are not apparent (fig. 5B). 

Concentrations of Sr vary widely, but systematically, in 

the carbonate fractions of the 2006 borehole samples (fig. 6). 

Limestone samples have Sr concentrations ranging from 

97.5 to 1,680 micrograms per gram (μg/g) with a median 

value of 384.5 μg/g (N=16) whereas dolomite samples have 

Sr concentrations ranging from 16.9 to 146 μg/g with a 

median value of 46.5 μg/g (N=21). Carbonate samples with 

CaCO3 mole percentages between 55 and 74 percent have 

intermediate Sr concentrations with a median value of 140 μg/

g (N=11). 

Concentrations of Rb in leachates of most samples are 

less than the minimum reporting limits of around 1 μg/g 

(table 5). Rb concentrations generally increase with increasing 

SiO2 (fig. 7A) indicating that silicate minerals (most likely 

clays) are a repository of Rb. Dolomite and limestone samples 

have similar Rb concentrations, but because of their lower Sr 

concentrations, dolomite samples tend to have higher Rb/Sr 

ratios (fig. 7B). Most samples have Rb/Sr ratios less than 

about 0.05. For a Cambrian marine carbonate sample with a 

Rb/Sr ratio of 0.05 and an initial 87Sr/86Sr value of 0.70900 

(δ87Sr = -0.28), the decay of 87Rb during the last 500 m.y. will 

result in a present-day 87Sr/86Sr value of 0.71003 (δ87Sr = 1.17), 

an increase of about one in the third decimal place. If the 

same rock had a Rb/Sr ratio of 0.015 (the upper limit for most 

dolomite and limestone samples, fig. 7B), the present-day 87Sr/86Sr ratio would only evolve to 0.70931 (δ87Sr = 0.15). 

Only four clay-rich samples have Rb/Sr ratios higher than 

0.056 (fig. 7B).

Additional elements reported in table 5 include 

MnO, Th, and U. Concentrations of MnO are statistically 

uncorrelated with mole percent CaCO3 contents (linear 

correlation coefficient, r2, of 0.035) although the highest 

MnO concentrations are present in limestones. Samples with 

the lowest SiO2 concentrations also tend to have the lowest 

MnO and Th concentrations indicating the potential influence 

of clay minerals and the low solubility of these constituents 

in marine environments. In contrast, U concentrations are 

uncorrelated statistically with SiO2 and are present in similar 

concentration ranges in dolomite and limestone samples. 

Because CaO and MgO concentrations are not 

available from XRF analyses, quantification of calcite mole 

percentages in outcrop samples was not possible. Bulk-rock 

Sr concentrations range from 16 to 2,537 μg/g with most 

samples having between about 30 and 500 μg/g (table 6). 

Samples with Sr concentrations greater than 500 μg/g typically 

increase along with Zr concentrations (fig. 8A). Because Zr is 

a highly insoluble element in marine environments (mean Zr 

concentration in North Pacific Ocean water is 0.000015 μg/g; 

McKelvey and Orians, 1993) compared to Sr (mean seawater 

Sr concentration of 7.74 μg/g; Faure and Mensing, 2005, 

p. 437), Sr concentrations greater than 500 μg/g in outcrop 

samples likely are attributable to silicate constituents included 

in the rock. Concentrations of Rb typically cluster at values 

less than 5 μg/g and are not correlated with Sr concentrations 

(r2 value of 0.039 in fig. 8B). However, the crude correlation 

between Rb and Zr concentration (r2 value of 0.43 in fig. 8C) 

implies that both constituents are derived from terrigenous 

silicate components. Therefore, outcrop samples with the 

lowest Zr concentrations best represent the carbonate fraction 

of these bulk-rock analyses. A frequency distribution plot of 

Sr concentrations in samples having Zr concentrations less 

than 20 μg/g (fig. 8D) indicates a narrow frequency peak 

between 25 and 75 μg/g (mostly classified as dolomites in 

field descriptions) and a broader frequency peak between 100 

and 400 μg/g (mostly classified as limestones).

24  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
NV19-4119_fig05

LEACHATES WITH SiO2 LESS THAN 5 WEIGHT PERCENT (WT. %)

LEACHATES WITH SiO2 GREATER THAN 5 WT. %

MIXING LINE BETWEEN CALCITE AND DOLOMITE

0.01

0.1

1

10

ALUMINUM OXIDE (Al2O3) CONCENTRATION (WT. %)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

 SILICON DIOXIDE (SiO2) CONCENTRATION (WT. %)

A.

B.

Linear regression of carbonate leachates

y = 0.498 x - 0.08

r2 = 0.83

Leachates with SiO2

concentrations less than 

detection limits of 0.17 to 

0.24 wt. %

0.1 1 10

 SILICON DIOXIDE (SiO2) CONCENTRATION (WT. %)

40 50 60 70 80 90 100

MOLE PERCENT CALCITE (CaCO3)

Figure 5. Relation between (A) silicon dioxide (SiO2) and aluminum oxide (Al2O3) 

concentrations and between (B) silicon dioxide and mole percent calcite (CaCO3

) in 

acid leachates of borehole samples, Nevada Test Site, Nye County, Nevada. Error bars 

represent 2-sigma analytical uncertainty and are shown as 30 percent of the reported 

concentration value for Al2

O3 values less than 0.1 wt. % and SiO2 values less than 0.4 wt. 

%, and 15 percent for higher concentration values.

Major and Trace Element Chemistry  25
NV19-0119_NTSRock_FIG-06 STRONTIUM CONCENTRATION, IN MICROGRAMS PER GRAM

DOLOMITE

48-54 mole percent 

calcite (CaCO3)

(16.9 - 146 μg/g)

N = 21

Median = 46.5 μg/g

MIXED

55-74 mole percent 

calcite (CaCO3)

N = 11

Median = 140 μg/g

LIMESTONE

93-100 mole percent 

calcite (CaCO3)

(97.5 - 1,680 μg/g)

N = 16

Median = 384.5 μg/g

200

400

600

800

1,000

1,200

1,400

1,600

1,800

40 50 60 70 80 90 100

0

500

1,000

1,500

2,000

A.

B.

0

MOLE PERCENT CALCITE (CaCO3)

LEACHATES WITH SiO2 LESS THAN 5 WEIGHT PERCENT (WT. %)

LEACHATES WITH SiO2 GREATER THAN 5 WT. %

Figure 6. Relation between (A) strontium (Sr) concentration and mole percent 

calcite (CaCO3

) in acid leachates of borehole samples, and (B) distribution of 

strontium concentrations for acid leachates, Nevada Test Site, Nye County, Nevada. 

Error bars represent 2-sigma analytical uncertainty and are shown as 10 percent of 

the reported concentration value for strontium and are fixed at 4 mole percent CaCO3

.

26  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
NV19-0119_NTSRock_FIG-07

SAMPLES WITH Rb CONCENTRATIONS GREATER THAN 

 DETECTION LIMITS

SAMPLES WITH Rb CONCENTRATIONS LESS THAN 

 DETECTION LIMITS (VALUE GRAPHED BASED 

 ON 0.5×DETECTION LIMIT VALUE)

0

10

20

30

40

50

60

70

0.0

RUBIDIUM (Rb) CONCENTRATION, IN MICROGRAMS PER GRAM RUBIDIUM / STRONTIUM (Rb / Sr)

0.00

0.05

0.10

0.15

0.20

0.25

40 50 60 70 80 90 100

MOLE PERCENT CALCITE (CaCO3)

A.

B.

2.0 4.0 6.0 8.0 10.0

 SILICON DIOXIDE (SiO2) CONCENTRATION, IN WEIGHT PERCENT

UE10j(2051)

ER12-4(3450)

ER16-1(3450)

Army#1(862)

Figure 7. Relation between (A) rubidium (Rb) and silicon dioxide (SiO2) concentrations 

in acid leachates of borehole samples and between (B) rubidium/strontium (Rb/Sr) 

concentration ratios and mole percent calcite (CaCO3

) in acid leachates of borehole 

samples, Nevada Test Site, Nye County, Nevada. Error bars represent 2-sigma analytical 

uncertainty and are shown as 10 percent of the reported concentration value for 

rubidium values and 14 percent for rubidium/strontium values. Mole percentages of 

calcite are shown with fixed 2-sigma analytical uncertainties of 4 mole percent CaCO3

.

Major and Trace Element Chemistry  27
Map

No.

Sample

No.

Rock

type Rb Sr Zr Ba La Ce 87

Sr/86Sr ±2σ δ87

Sr

‰ ±2σ Unit δ87

Srt

‰

Seawater 

87

Sr/86Srpsw

used

1 HD-1106 Calcitic 

marble

14 1,424 54 0 8 ND 0.70748 0.00005 -2.43 0.07 Yb NC Undefined

2 HD-1111 Marble 7 1,453 40 191 0 4 .70727 .00005 -2.72 .07 Yc NC Undefined

3 HD-1112 Marble 3.3 1,614 55 187 6 13 .70735 .00005 -2.61 .07 Yc NC Undefined

4 HD-1107 Dolomite 4 1,660 47 46 0 0 .70720* .00005 -2.82 .07 Yb NC Undefined

5 HD-1114 Marble 0 2,537 78 11 5 10 .70940* .00005 .28 .07 Yc NC Undefined

6 HD-1105 Dolomite 5 75 31 126 33 60 .71343 .00005 5.97 .07 Zs-c NC Undefined

7 HD-1151 Limestone 8 1164 59 25 13 7 .70945 .00005 .35 .07 CZw 1.48 0.7084

8 3C-1 Carbonate 2.5 221 10 30 18 13 .71106 .00005 2.62 .07 Cb 2.76 .7091

9 HD-212 Dolomite 0 146 1 ND ND ND .71181 .00005 3.68 .07 Cb-b 3.68 .7092

10 HD-214 Dolomite 0 211 0 ND ND ND .71279 .00008 5.06 .11 Cb-b 5.06 .7092

11 HD-216 Dolomite 0 256 0 ND ND ND .71125 .00005 2.89 .07 Cb-b 2.89 .7092

12 HD-218 Dolomite 2 152 2 ND ND ND .71201 .00007 3.96 .10 Cb-b 3.96 .7092

13 HD-219 Dolomite 6.8 176 14 ND ND ND .71162 .00005 3.41 .07 Cb-b 3.41 .7092

14 HD-220 Dolomite 1 86 5 ND ND ND .71120 .00005 2.82 .07 Cb-b 2.82 .7092

15 HD-221 Dolomite 0 268 0 ND ND ND .71070 .00005 2.12 .07 Cb-b 2.12 .7092

16 HD-1154 Limestone 24 261 124 180 14 30 .72543 .00005 22.89 .07 CZw-u 24.0 .7084

17 HD-1155 Limestone 7 445 93 47 19 49 .71958 .00005 14.64 .07 CZw 15.8 .7084

18 HD-538 Marble .6 245 4 45 8 7 .70921 .00005 .01 .07 Cb-p .30 .7090

19 HD-539 Dolomite .6 28 0 34 20 16 .70999 .00005 1.11 .07 Cb-p 1.39 .7090

20 HD-540 Dolomite .6 23 0 31 8 12 .70922 .00005 .03 .07 Cb-p .31 .7090

21 HD-541 Calcitic 

marble

2.8 636 27 149 15 37 .72141 .00005 17.21 .07 CZw-u 18.4 .7084

22 HD-513 Dolomite 2.4 96 16 37 28 2 .70946 .00005 .37 .07 Oes 1.35 .7085

23 HD-515 Dolomite 1.3 58 1 42 8 2 .70875 .00005 - .64 .07 Oes .35 .7085

24 HD-516A Dolomite 2.4 71 9 42 28 2 .70981 .00008 .86 .11 Sr 1.42 .7088

25 HD-517 Limestone 16 311 36 88 22 16 .71319 .00005 5.63 .07 Sr 6.19 .7088

26 HD-518 Dolomite 7.9 63 31 113 8 12 .71105 .00005 2.61 .07 Sr 3.17 .7088

27 HD-519 Dolomite 1.9 64 0 45 8 10 .70882 .00008 - .54 .11 DSlm .03 .7088

28 HD-520 Dolomite .6 55 2 36 11 7 .70861 .00005 - .83 .07 DSlm .01 .7086

29 HD-533 Limestone .6 300 11 102 8 2 .71175 .00005 3.6 .07 Op-av 4.02 .7089

30 HD-534 Limestone 4.8 298 6 52 8 9 .71101 .00006 2.55 .08 Op-g 2.69 .7091

31 HD-535 Dolomite .6 39 0 32 28 2 .70877 .00006 - .61 .08 Cn-s - .47 .7091

32 HD-1415 Carbonate 0 113 4 0 7 3 .71648 .00005 10.27 .07 Cb-p 10.6 .7090

33 HD-1416 Carbonate 0 177 5 0 13 0 .71323 .00005 5.68 .07 Cb-p 5.97 .7090

34 HD-1417 Carbonate 0 979 47 34 12 38 .71829 .00005 12.82 .07 CZw-l 14.0 .7084

35 HD-1418 Carbonate 0 151 2 0 0 0 .72260 .00005 18.9 .07 CZw-l 20.0 .7084

36 HD-1419 Carbonate 0 166 4 2 15 11 .72327 .00005 19.84 .07 Cb-p 20.1 .709

37 HD-1420 Carbonate 0 66 1 0 6 0 .71905 .00005 13.89 .07 Cb-p 14.2 .709

38 HD-1421 Carbonate 2.8 627 28 47 13 31 .71374 .00005 6.40 .07 CZw-l 7.54 .7084

39 HD-527 Dolomite .6 47 0 25 18 10 .70816 .00007 -1.47 .10 Df .37 .7079

40 HD-528 Dolomite 1.1 60 0 39 8 11 .71152 .00005 3.27 .07 Df 5.11 .7079

41 HD-529 Calcitic 

marble

3 166 0 41 8 2 .71017 .00005 1.36 .07 Cb-b 1.36 .7092

42 HD-530 Dolomitic 

marble

.6 27 0 33 16 2 .70927 .00005 .10 .07 Cb-b .10 .7092

Table 6. Bulk-rock analyses of selected trace element concentrations and strontium isotopic compositions (87Sr/86Sr) in outcrop 

samples collected in the early 1990s from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, 

California.

[Trace element (Rb, Sr, Zr, Ba, La, and Ce) concentrations were determined by X-ray fluorescence on whole-rock samples and are given in micrograms per gram 

(μg/g). Concentrations below minimum reporting limits are indicated as “0”. “ND” indicates that concentrations were not determined. All strontium isotopic 

compositions (87Sr/86Sr) were determined on dilute hydrochloric acid leachates of powdered rock samples with the exception of two samples (map numbers 4 

and 5 marked with asterisks) which were determined on whole-rock digestions. 87Sr/86Sr uncertainties are typically, but not always, dominated by external error 

associated with reproducibility of the EN–1 standard (±0.00005). Strontium isotopic compositions are also given in delta notation (δ87Srt) = [(87Sr/86Srsample/

87Sr/ 86Srpsw)-1]×1,000, where 87Sr/86Srmsw is the value for modern seawater and 87Sr/86Srpsw is the value for paleoseawater at the time of deposition. δ87Srt

 values for 

rocks underlying the Wood Canyon Formation were not calculated (NC) because of the very large uncertainties in assigning ages and initial seawater 87Sr/86Sr 

values, which are designated as “undefined” Abbreviations and symbols: Rb, rubidium; Sr, strontium; Zr, zirconium; La, lanthanum; Ce, cerium; ‰, per mil]

28 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Map

No.

Sample

No.

Rock

type Rb Sr Zr Ba La Ce 87

Sr/86Sr ±2σ δ87

Sr

‰ ±2σ Unit δ87

Srt

‰

Seawater 

87

Sr/86Srpsw

used

43 HD-531 Calcitic 

marble

4.2 403 13 50 8 2 0.70960 0.00005 0.56 0.07 Cn-h 0.56 0.7092

44 HD-542 Dolomitic 

marble

4.5 371 8 39 20 28 .71010 .00005 1.27 .07 CZw-l 2.40 .7084

45 HD-543 Dolomite .6 200 2 39 16 21 .71551 .00005 8.90 .07 Cb-p 9.19 .7090

46 HD-1152b Altered

limestone

4 98 16 11 5 9 .71150 .00005 3.24 .07 Zs-d NC Undefined

47 HD-1153 Limestone 3 306 12 13 14 25 .71125 .00005 2.89 .07 Zs-d NC Undefined

48 HD-1142 Limestone 6 390 18 29 0 0 .70876 .00005 - .62 .07 Op-g - .20 .7089

49 HD-1144 Limestone 2 35 14 58 14 0 .70935 .00005 .21 .07 Df 2.04 .7079

50 HD-1400 Carbonate 0 56 0 0 12 8 .71265 .00005 4.87 .07 Cb-b 4.87 .7092

51 HD-1401 Carbonate 1.4 70 3 0 15 10 .71289 .00005 5.20 .07 Cb-b 5.2 .7092

52 HD-1402 Carbonate 0 67 1 0 13 0 .71173 .00005 3.57 .07 Cb-b 3.57 .7092

53 HD-641 Carbonate 0 62 7 0 20 25 .71703 .00008 11.04 .11 Cb-b 11.0 .7092

54 HD-537 Dolomite 9.1 115 29 61 36 66 .71275 .00005 5.01 .07 Zs-d NC Undefined

55 HD-1146 Limestone 0 283 8 147 4 0 .71292 .00005 5.25 .07 MDe 6.95 .7080

56 HD-1147a Limestone 14 197 20 140 8 12 .70926 .00005 .09 .07 Dtc .66 .7088

57 HD-1147b Limestone 2 120 5 23 6 7 .71088 .00005 2.37 .07 Dtc 2.93 .7088

58 HD-522 Dolomite 1.3 63 0 101 29 27 .70976 .00008 .79 .11 Dtc 1.35 .7088

59 HD-523 Limestone 6.7 172 7 141 8 13 .71029 .00005 1.53 .07 Dtc 2.10 .7088

60 HD-526 Limestone 2.5 668 20 55 13 6 .71018 .00007 1.38 .10 Cc-m 2.37 .7085

61 HD-1138 Limestone 9 777 40 37 12 0 .70884 .00005 -.51 .07 Op-av -.09 .7089

62 HD-1139 Dolomite/

limestone

2 65 20 0 16 0 .70935 .00005 .22 .07 DSlm .78 .7088

63 HD-1141 Limestone 10 1,140 54 57 14 0 .70906 .00005 - .2 .07 Op-av .22 .7089

64 HD-1150b Carbonate 7 507 25 38 7 22 .71722 .00005 11.31 .07 CZw 12.5 .7084

65 HD-546 Dolomite .6 45 0 36 25 24 .70886 .00006 - .48 .08 Dsi 1.36 .7079

66 HD-548 Limestone 8.5 382 8 42 17 18 .70921 .00007 .01 .10 Op-av .44 .7089

67 HD-549 Limestone 10.6 315 10 82 8 11 .70979 .00005 .83 .07 Op-g .97 .7091

68 HD-550 Limestone 3.7 297 7 45 23 13 .70921 .00005 .01 .07 Op-g .16 .7091

69 HD-551A Dolomite .6 47 1 30 19 19 .70929 .00005 .13 .07 Op-g .27 .7091

70 HD-553 Limestone 4.2 631 22 48 12 2 .71013 .00005 1.31 .07 Cn-h 1.31 .7092

71 HD-554 Limestone .6 496 9 42 8 8 .70937 .00005 .24 .07 Cb-b .24 .7092

72 HD-555 Limestone 2.1 348 10 44 16 16 .70936 .00005 .23 .07 Cb-b .23 .7092

73 HD-556 Limestone 3.2 362 9 50 8 7 .70938 .00005 .25 .07 Cb-b .25 .7092

74 HD-557 Limestone 1.9 207 3 36 15 2 .70912 .00005 - .11 .07 Cb-p .03 .7091

75 HD-558 Limestone 5.2 442 5 32 8 2 .70918 .00007 - .03 .10 Cb-p .11 .7091

76 HD-1422-1 Carbonate 30.2 528 74 118 11 14 .71255 .00005 4.72 .07 Cb-b 4.72 .7092

77 HD-1422-2 Carbonate 3 247 14 17 4 17 .71103 .00005 2.58 .07 Cb-b 2.58 .7092

78 HD-1423 Carbonate 19.6 204 51 82 16 0 .71003 .00005 1.17 .07 Cb-b 1.17 .7092

79 HD-1426 Carbonate 1.4 145 18 8 19 38 .71243 .00005 4.56 .07 CZw 5.55 .7085

80 HD-1427 Carbonate 3.8 334 20 10 0 0 .70937 .00005 .24 .07 Cb-b .24 .7092

81 HD-1428 Carbonate 0 175 5 0 6 5 .70899 .00005 - .30 .07 Cb-b - .16 .7091

82 HD-1429 Carbonate 3.3 292 14 10 9 4 .70911 .00005 - .13 .07 Cb-b .01 .7091

83 HD-1432 Carbonate 1.9 555 21 9 12 11 .70931 .00005 .16 .07 Cn .30 .7091

Table 6. Bulk-rock analyses of selected trace element concentrations and strontium isotopic compositions (87Sr/86Sr) in outcrop 

samples collected in the early 1990s from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, 

California.—Continued

[Trace element (Rb, Sr, Zr, Ba, La, and Ce) concentrations were determined by X-ray fluorescence on whole-rock samples and are given in micrograms per gram 

(μg/g). Concentrations below minimum reporting limits are indicated as “0”. “ND” indicates that concentrations were not determined. All strontium isotopic 

compositions (87Sr/86Sr) were determined on dilute hydrochloric acid leachates of powdered rock samples with the exception of two samples (map numbers 4 

and 5 marked with asterisks) which were determined on whole-rock digestions. 87Sr/86Sr uncertainties are typically, but not always, dominated by external error 

associated with reproducibility of the EN–1 standard (±0.00005). Strontium isotopic compositions are also given in delta notation (δ87Srt) = [(87Sr/86Srsample/

87Sr/ 86Srpsw)-1]×1,000, where 87Sr/86Srmsw is the value for modern seawater and 87Sr/86Srpsw is the value for paleoseawater at the time of deposition. δ87Srt

 values for 

rocks underlying the Wood Canyon Formation were not calculated (NC) because of the very large uncertainties in assigning ages and initial seawater 87Sr/86Sr 

values, which are designated as “undefined” Abbreviations and symbols: Rb, rubidium; Sr, strontium; Zr, zirconium; La, lanthanum; Ce, cerium; ‰, per mil]

Major and Trace Element Chemistry  29
Map

No.

Sample

No.

Rock

type Rb Sr Zr Ba La Ce 87

Sr/86Sr ±2σ δ87

Sr

‰ ±2σ Unit δ87

Srt

‰

Seawater 

87

Sr/86Srpsw

used

84 HD-1434 Carbonate 0 51 0 0 17 8 0.70804 0.00005 -1.64 0.07 Dsv 0.06 0.7080

85 HD-1435 Marble 1 501 21 13 7 14 .71282 .00005 5.10 .07 Cc 6.09 .7085

86 HD-1436 Carbonate 2 140 6 0 12 24 .70922 .00005 .03 .07 Cb-b .03 .7092

87 HD-110-1 Limestone 5 312 20 ND ND ND .70990 .00005 .99 .07 Cb-b .99 .7092

88 HD-471B Carbonate 10.7 345 36 107 21 15 .70980 .00009 .85 .13 Cb-b .85 .7092

89 GDR-8 Carbonate 2 275 5 ND ND ND .70913 .00005 - .10 .07 PMb 1.17 .7083

90 HD-229 Limestone 0 743 9 ND ND ND .70831 .00005 -1.26 .07 PMbl .01 .7083

91 HD-230 Limestone 0 132 0 ND ND ND .70827 .00005 -1.31 .07 PMbl - .04 .7083

92 HD-231 Limestone 2 564 2 ND ND ND .70844 .00005 -1.07 .07 Mm .34 .7082

93 HD-232 Limestone 0 25 0 ND ND ND .70857 .00005 - .89 .07 Cb-b - .75 .7091

94 HD-233 Limestone 0 28 0 ND ND ND .70933 .00008 .18 .11 Cb-b .18 .7092

95 HD-235 Limestone 0 29 0 ND ND ND .70847 .00007 -1.03 .10 Cn - .75 .7090

96 HD-236 Limestone 0 66 6 ND ND ND .70859 .00007 - .86 .10 Op - .01 .7086

97 HD-238 Limestone 8 263 82 ND ND ND .70790 .00005 -1.83 .07 PMb .00 .7079

98 HD-1000 Limestone 1 104 6 14 9 0 .70834 .00005 -1.21 .07 Dg .06 .7083

99 HD-999 Dolomite 3 29 13 32 18 0 .70881 .00005 - .55 .07 Cn-s - .27 .7090

100 HD-995 Dolomite 0 67 4 22 15 9 .70845 .00005 -1.06 .07 Oes .21 .7083

101 HD-996 Dolomite 2 327 14 25 18 13 .70912 .00005 - .12 .07 Op-av .17 .7090

102 HD-997 Dolomite 0 422 15 19 7 0 .70884 .00005 - .51 .07 Oes .76 .7083

103 HD-998 Limestone 3 345 11 43 0 0 .70880 .00005 - .56 .07 Op-av .01 .7088

104 HD-1001 Dolomite 1 233 9 29 5 0 .70912 .00005 - .12 .07 Op-av .17 .7090

105 HD-1006 Limestone 1 16 42 10 14 0 .70918 .00005 - .02 .07 Op-av .12 .7091

106 HD-990 Limestone 2 56 6 13 8 0 .70841 .00005 -1.11 .07 Op-av - .12 .7085

107 HD-1002 Dolomite 1 44 5 11 14 0 .70853 .00005 - .95 .07 Oes .32 .7083

108 HD-991 Dolomite 1 63 2 5 8 13 .70813 .00005 -1.51 .07 Oes .04 .7081

109 HD-993 Dolomite 0 22 0 30 9 14 .70862 .00005 - .82 .07 Dsi 1.01 .7079

110 HD-994 Limestone 0 470 15 42 13 0 .70817 .00005 -1.45 .07 Mj .10 .7081

111 HD-1004 Limestone 4 204 85 38 17 10 .70884 .00005 - .50 .07 Op-av - .08 .7089

112 HD-1003 Limestone 4 164 13 20 0 0 .70826 .00005 -1.32 .07 Dg - .05 .7083

113 HD-1007 Limestone 2 258 22 19 13 18 .70994 .00005 1.04 .07 Op-g 1.18 .7091

114 HD-1008 Dolomite 9 59 32 29 0 0 .70915 .00005 - .07 .07 Dsv .49 .7088

Table 6. Bulk-rock analyses of selected trace element concentrations and strontium isotopic compositions (87Sr/86Sr) in outcrop 

samples collected in the early 1990s from the Nevada Test Site vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, 

California.—Continued

[Trace element (Rb, Sr, Zr, Ba, La, and Ce) concentrations were determined by X-ray fluorescence on whole-rock samples and are given in micrograms per gram 

(μg/g). Concentrations below minimum reporting limits are indicated as “0”. “ND” indicates that concentrations were not determined. All strontium isotopic 

compositions (87Sr/86Sr) were determined on dilute hydrochloric acid leachates of powdered rock samples with the exception of two samples (map numbers 4 

and 5 marked with asterisks) which were determined on whole-rock digestions. 87Sr/86Sr uncertainties are typically, but not always, dominated by external error 

associated with reproducibility of the EN–1 standard (±0.00005). Strontium isotopic compositions are also given in delta notation (δ87Srt) = [(87Sr/86Srsample/

87Sr/ 86Srpsw)-1]×1,000, where 87Sr/86Srmsw is the value for modern seawater and 87Sr/86Srpsw is the value for paleoseawater at the time of deposition. δ87Srt

 values for 

rocks underlying the Wood Canyon Formation were not calculated (NC) because of the very large uncertainties in assigning ages and initial seawater 87Sr/86Sr 

values, which are designated as “undefined” Abbreviations and symbols: Rb, rubidium; Sr, strontium; Zr, zirconium; La, lanthanum; Ce, cerium; ‰, per mil]

30 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Strontium Isotopic Compositions

Values of 87Sr/86Sr for the carbonate fractions of borehole 

(tables 5 and 7), and outcrop (table 6) samples range from 

0.70720 to 0.72543 and have distributions that are skewed 

toward radiogenic values (fig. 9). For both sets of samples, 

approximately 54 percent of the 87Sr/86Sr analyses are within 

the range of Paleozoic seawater values between 0.7070 and 

0.7092. The remaining analyses have larger 87Sr/86Sr values, 

typically between 0.7093 and 0.7150. Data from Yucca Flat 

core and cutting samples do not form linear trends on plots 

comparing 87Sr/86Sr to reciprocal Sr concentration (fig. 10A) 

where binary mixing trends would plot as straight lines. 

Therefore, there is no indication that low Sr carbonates were 

more susceptible to addition of radiogenic Sr from secondary 

fluids than high Sr samples. Furthermore, there are no clear 

indications that elevated 87Sr/86Sr values in carbonate fractions 

are related to the presence of Rb-rich silicate components 

leached from the samples (fig. 10B). Although the two clayrich samples with the highest SiO2

 concentrations also have 

the highest 87Sr/86Sr values, similar trends are not present in 

samples with lower SiO2 concentrations.

NV19-0119_NTSRock_FIG-08

UNDIFFERENTIATED

DOLOMITE

LIMESTONE

20

40

60

80

100

120

140

A.

B.

0

5

10

15

20

25

30

35

RUBIDIUM (Rb) CONCENTRATION,

 IN MICROGRAMS PER GRAM

ZIRCONIUM (Zr) CONCENTRATION, 

IN MICROGRAMS PER GRAM

2,500

C.

2,500

RUBIDIUM (Rb) CONCENTRATION,

IN MICROGRAMS PER GRAM FREQUENCY

0

0

5

5

10

10

15

15

20

20

25

30

35

D.

0 500 1,000 1,500 2,000

STRONTIUM (Sr) CONCENTRATION,

IN MICROGRAMS PER GRAM

STRONTIUM (Sr) CONCENTRATION,

IN MICROGRAMS PER GRAM

0 100 200 300 400 500 600 800700

0 500 1,000 1,500 2,000

STRONTIUM (Sr) CONCENTRATION, 

IN MICROGRAMS PER GRAM

0 20 40 60 80 100 120 140

 ZIRCONIUM (Zr) CONCENTRATION, 

IN MICROGRAMS PER GRAM

0

Outcrop samples with

Zr concentrations <20 μg/g

N = 85

Linear regression of bulk-rock data

y = 0.0025x + 2.7

r2 = 0.039

Linear regression of bulk-rock data

y = 0.14x + 1.0

r2 = 0.43

Figure 8. Relation between (A) strontium (Sr) and zirconium (Zr) concentrations, (B) strontium and rubidium (Rb) concentrations, 

(C) zirconium and rubidium concentrations for bulk-rock outcrop samples, and (D) the frequency distribution of strontium 

concentrations for bulk-rock outcrop samples with zirconium concentrations less than or equal to 20 micrograms per gram, 

Nevada Test Site and adjacent areas, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California. Error bars represent 

2-sigma analytical uncertainty and are shown as 10 percent of the reported concentration value.

Strontium Isotopic Compositions  31
Values of δ87Srt

 calculated with respect to the estimates 

for Paleozoic seawater 87Sr/86Sr at the time of deposition range 

widely from -1.40 to 24.0 (tables 5–7; fig. 11). Estimates 

for the original seawater 87Sr/86Sr were made using the 

lithostratigraphic age assignments (table 1) and the Paleozoic 

seawater 87Sr/86Sr curve of McArthur and others (2001; fig. 3). 

In many cases, specific age and Paleozoic seawater 87Sr/86Sr 

values for individual samples were chosen from the ranges 

permissible in table 1 to obtain a δ87Srt

 value closer to 0.0. 

Although the Paleozoic seawater 87Sr/86Sr evolution curve 

is well established, error bars are not shown on figure 11

because of the difficulty in defining uncertainties for rock 

ages based on stratigraphic intervals that can span ranges 

of 10–50 m.y. or more. Values of δ87Srt close to 0.0 indicate 

that the carbonate rocks likely have retained their original 

Paleozoic marine Sr isotopic signatures. In some cases, 

these data may help corroborate age assignments based on 

biostratigraphic information (Banner, 2004, p. 167). However, 

it is preferable to obtain 87Sr/86Sr data from low-magnesium 

calcite constituting marine skeletons instead of from bulk 

rock to avoid post-depositional alteration (Veizer and others, 

1999, p. 62). Because all analyses reported here were done on 

bulk-rock samples, no attempts are made to refine depositional 

ages.

Table 7. Selected trace element concentrations and strontium isotopic compositions (87Sr/86Sr) in core samples from boreholes 

UE-25 a #3 and UE-25 p #1, Nevada Test Site, Nye County, Nevada.

[Siliciclastic lithologies for samples from surface to 697.2-m depth in borehole UE–25 a #3 consist of Mississippian (middle Chester to early Osage stages) 

Chainman Shale and Gap Wash Formation (Maldonado and others, 1979; Cole and Cashman, 1998). Underlying core is undifferentiated Devonian carbonate 

(Du). Stratigraphic units for borehole UE–25 p #1 are from Carr and others (1986). Stratigraphic unit symbols are defined in table 1. Analysis type: WR 

indicates that strontium isotopic compositions (87Sr/86Sr) were determined on whole-rock digestions using concentrated hydrofluoric, nitric, hydrochloric, 

and sulfuric acids; HCl–L indicates that 87Sr/86Sr values were determined on dilute hydrochloric acid leachates of powdered rock samples. Strontium isotopic 

compositions also are given in delta notation (δ87Sr = [(87Sr/86Srsample/

87Sr/86Srmsw)-1]×1,000 and δ87Srt

 = [(87Sr/86Srsample/

87Sr/86Srpsw)-1]×1,000, where 87Sr/86Srmsw is 

the value for modern seawater and 87Sr/86Srpsw is the value for paleoseawater at the time of deposition). Abbreviations and symbols: Rb, rubidium; Sr, strontium; 

Y, yittrium; Zr, zirconium; Nb, Niobium; Ba, barium; La, lanthanum; Ce, cerium; m, meter; ‰, per mil; ND, not determined]

Sample

identification 

No.

Borehole

Borehole 

depth 

(m)

Stratigraphic

 unit

Rb Sr Y Zr Nb Ba La Ce Analysis 

type

87

Sr/86Sr 

(±0.00005 2σ)

δ87Sr, ‰ 

(±0.07 2σ)

δ87Srt,

‰

Seawater 

87

Sr/86Srpsw

used

UE25a3–142 UE–25 a #3 43.3 Mc/MDg 48 89 45 320 16 115 ND ND WR 0.71554 8.94 10.4 0.7082

UE25a3–324 UE–25 a #3 98.8 Mc/MDg 90 176 41 173 20 182 ND ND WR .71616 9.81 11.4 .7081

UE25a3–493 UE–25 a #3 150.4 Mc/MDg 54 91 42 282 20 ND ND WR .71795 12.34 14.0 .7080

UE25a3–684 UE–25 a #3 208.4 Mc/MDg 84 177 44 212 21 210 ND ND WR .71539 8.73 10.5 .7079

UE25a3–863 UE–25 a #3 263.1 Mc/MDg 77 159 49 273 19 189 ND ND WR .71523 8.50 10.5 .7078

UE25a3–1069 UE–25 a #3 325.7 Mc/MDg 80 205 43 189 20 240 ND ND WR .71494 8.09 10.2 .7077

UE25a3–1430 UE–25 a #3 435.9 Mc/MDg 78 74 27 117 9 1,247 ND ND WR .71633 10.05 12.2 .7077

UE25a3–1722 UE–25 a #3 525.0 Mc/MDg 146 65 32 151 14 1,575 ND ND WR .72022 15.54 17.4 .7079

UE25a3–1846 UE–25 a #3 562.5 Mc/MDg 61 86 26 137 15 889 ND ND WR .72087 16.46 18.3 .7080

UE25a3–2093 UE–25 a #3 637.9 Mc/MDg 39 51 15 96 6 394 ND ND WR .72369 20.43 22.1 .7081

UE25a3–2287 UE–25 a #3 697.2 Mc/MDg 71 131 31 176 7 299 ND ND WR .71700 11.00 12.5 .7082

UE25a3–2432 UE–25 a #3 741.1 Du 2 87 33 6 2 ND ND WR .71323 5.68 7.10 .7082

UE25a3–2492 UE–25 a #3 759.6 Du 0 60 5 3 0 73 21 3 HCl-L .71111 2.69 4.04 .7083

UE25a3–2514 UE–25 a #3 766.4 Du 0 36 5 2 0 38 24 6 HCl-L .71080 2.26 3.60 .7083

HD–622 UE–25 p #1 1,277.7 DSlm 0 68 0 14 0 10 5 11 HCl-L .70907 - .19 .38 .7088

HD–621 UE–25 p #1 1,284.1 DSlm 0 62 0 11 0 0 9 0 HCl-L .70905 - .21 .35 .7088

UE25p 1–5900 UE–25 p #1 1,798.3 Sr 3 70 5 15 0 0 23 14 HCl-L .70835 -1.20 - .07 .7084

32  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
NV19-4119_NTSRock_FIG-09

MEASURED VALUES

RANGE FOR PERMIAN TO MISSISSIPPIAN SEAWATER

RANGE FOR DEVONIAN TO LATE PROTEROZIC SEAWATER

0.705 0.710 0.715 0.720 0.725

0

0

5

5

10

10

15

15

20

25

30

2006 Borehole samples

N = 48

Bin width = 0.0005

Outcrop samples

N = 114

Bin width = 0.0005

NUMBER OF SAMPLES 

87Sr / 86Sr

Figure 9. Distribution of strontium isotopic compositions (87Sr/86Sr) measured in borehole and outcrop 

samples, Nevada Test Site and adjacent areas, Clark, Lincoln, and Nye Counties, Nevada, and Inyo 

County, California. Permian and Pennsylvanian carbonates constituting the upper carbonate aquifer at 

the Nevada Test Site (fig. 2) typically have lower 87Sr/86Sr values than the older Paleozoic carbonates 

constituting the lower carbonate aquifer (87Sr/86Sr ranges from figure 3).

Strontium Isotopic Compositions  33
NV19-4119_NTSRock_FIG-10

0.7070

0.7080

0.7090

0.7100

0.000 0.010 0.020 0.030 0.040 0.050

1 / STRONTIUM CONCENTRATION, IN GRAMS PER MICROGRAM

0.060 0.070

0.7110

0.7120

0.7130

0.7140

0.7150

0.7160

87Sr / 86Sr 87Sr / 86Sr

A.

0.0 2.0 4.0 6.0 8.0 10.0

SILICON DIOXIDE (SiO2) CONCENTRATION (WT. %)

0.7070

0.7080

0.7090

0.7100

0.7110

0.7120

0.7130

0.7140

0.7150

0.7160

B.

EXPLANATION

LEACHATES WITH SiO2 < 5 WEIGHT 

PERCENT (WT. %) 

LEACHATES WITH SiO2 > 5 WT. %

PERMIAN TO MISSISSIPPIAN SEAWATER 87Sr/86Sr

DEVONIAN TO NEOPROTEROZOIC SEAWATER 87Sr/86Sr

Figure 10. Relation between (A) strontium isotopic compositions (87Sr/86Sr) and 

reciprocal strontium concentrations for acid leachates of borehole samples and 

(B) 87Sr/86Sr and silicon dioxide (SiO2

) concentrations for acid leachates of borehole 

samples, Nevada Test Site, Nye County, Nevada. Error bars represent 2-sigma 

analytical uncertainty and are shown as 10 percent of the reported concentration 

value for strontium and 15 percent for SiO2

.

34  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
NV19-4119_fig11

-2.0

-2.0

0.0

0.0

2.0

2.0

4.0

4.0

6.0

6.0

8.0

8.0

10.0

10.0

12.0

12.0

14.0

14.0

16.0

16.0

18.0

18.0

20.0

20.0

250

250

300

300

350

350

400

400

450

450

500

500

550

550

600

600

DEPOSITIONAL AGE (Ma)

DEPOSITIONAL AGE (Ma)

δ87Srt (PER MIL)

δ87Srt (PER MIL)

Permian

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

Neoproterozoic

Permian

Pennsylvanian

Mississippian

Devonian

Silurian

Ordovician

Cambrian

Neoproterozoic

2006 BOREHOLE SAMPLES

OUTCROP SAMPLES

Figure 11. Relation between δ87Srt, and depositional age for acid leachates of borehole and outcrop samples, Nevada 

Test Site and adjacent areas, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California. Data are from tables 

5 and 6. Four analyses with δ87Srt

, values between 20.0 and 24.0 are not shown. Shaded band depicts ±1 per mil deviation 

from the assumed paleoseawater value and is shown for reference.

Strontium Isotopic Compositions  35
Samples with measured 87Sr/86Sr values greater 

than 0.7093 in tables 5–7 have undergone obvious postdepositional addition of radiogenic Sr (Peterman and others, 

1994). Samples with elevated δ87Srt are present throughout 

the Paleozoic stratigraphic section in borehole and outcrop 

samples (fig. 11), indicating that 87Sr/86Sr alteration was 

not restricted to rocks formed during a narrow interval of 

Paleozoic time. Peterman and others (1994) documented that 

Paleozoic carbonates at Bare Mountain have elevated δ87Srt

values compared to samples from the Striped Hills, Specter 

Range, Spring Mountains, and mountain ranges east of the 

NTS (fig. 12). These anomalous δ87Srt values were obtained 

on samples from mineralized areas including the Stirling 

Gold Mine on the eastern flank of Bare Mountain. Peterman 

and others (1994, p. 1,321) postulated that hydrothermal 

mineralization was associated with Tertiary volcanic activity 

and involved localized plumes of thermal solutions which 

introduced radiogenic Sr derived from the Precambrian 

basement into carbonate rocks present at shallower crustal 

levels. Therefore, the spatial distribution of Paleozoic 

carbonate rocks with nonmarine 87Sr/86Sr compositions at and 

around the NTS (fig. 12) could be related to major crustal 

structures that provide fluid pathways and magmatic activity 

that provided thermal sources.

Paleozoic carbonates present in the northeastern part 

of the NTS have the potential to be affected by Tertiary 

magmatic activity constituting the southwestern Nevada 

volcanic field centered at Timber Mountain and Pahute Mesa 

(Byers and others, 1989; Sawyer and others, 1994). Results 

from this study indicate that Paleozoic limestone and dolomite 

beneath Rainier Mesa, Yucca Flat, and Frenchman Flat tend 

to have δ87Srt

 values intermediately between those measured 

at Bare Mountain and ranges southeast of the NTS (fig. 1; 

fig. 12A). Carbonate rocks with elevated δ87Srt are present 

near the bottom of borehole UE-15d (Rainstorm Member of 

the Johnnie Formation or Noonday Dolomite) underlying a 

thick section of Neoproterozoic siliciclastic rocks constituting 

the Lower Clastic Confining Unit in northern Yucca Flat. In 

western Yucca Flat and the Calico Hills, boreholes ER-16-1, 

ER-12-1, ER-6-2, UE-16d, and UE-25 a#3 penetrate thick 

sections of Eleana Formation, Gap Wash Formation, and 

Chainman Shale consisting of abundant litharenite, siltstone, 

and shale (fig. 1; fig. 12B). Clay minerals with elevated 

Rb/Sr in these siliciclastic rocks constituting the upper clastic 

confining unit are a possible source for radiogenic Sr in 

carbonate rocks present in these boreholes. Rocks constituting 

the upper clastic confining unit are not present in eastern 

Yucca Flat or Frenchman Flat, and carbonates from ER-3-1, 

ER-7-1, ER-6-1#2, and HTH #3 have retained their Paleozoic 

seawater signatures (fig. 12B). Other boreholes having LCA 

rocks directly underlying Tertiary volcanic or alluvial rocks 

may or may not have Paleozoic carbonate with elevated δ87Srt

values.

In several cases, Sr isotopic compositions were 

obtained from macroscopically unaltered and altered core 

samples [Army 1(859) and Army 1(862), TW-C(1458) and 

TW-C(1463.5)]. For both pairs, samples with brecciated 

textures, iron staining, and clay mineralization (table 3) 

had higher 87Sr/86Sr values than the sample lacking obvious 

alteration (table 5). The difference is most dramatic for 

leachates of samples Army 1(859) and Army 1(862) where 

the highly altered dolomite has Sr concentrations more than 

twice the value present in the unaltered dolomite and a δ87Srt

value of 3.84 compared to the near seawater value of -0.06 in 

the unaltered dolomite. Differences are not as large between 

samples TW-C(1458) and TW-C(1463.5) with negligibly 

higher Sr concentrations in the altered limestone (261 

compared to 251 μg/g) and δ87Srt values of 2.82 compared 

to 1.87. However, addition of radiogenic 87Sr is not always 

accompanied by obvious evidence for secondary alteration. 

Samples UE15d(5994), ER12-4(2580), ER6-2(1830), and 

ER5-3#2(4780) have δ87Srt values between 3.45 and 5.78, but 

do not show obvious macroscopic evidence of alteration. 

Finally, one pair of samples representing unaltered host 

dolomite [Army 1(982)A] and coarse secondary dolomite spar 

[Army 1(982)B] filling a cross-cutting vein were analyzed 

to investigate the degree of isotopic disequilibrium between 

the two materials. Leachates of both samples have similar 

Sr concentrations (30.7 compared to 37.9 μg/g; table 5) 

and analytically indistinguishable 87Sr/86Sr values (0.71027 

compared to 0.71023). These data are consistent with a local 

source of Sr for the younger dolomite spar. Although the 

age and petrogenesis of the secondary dolomite vein are not 

known, the thick filling of dense, coarsely crystalline dolomite 

is not likely to have formed under modern ground-water flow 

conditions.

36  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
NV19-4119_fig12A

Universal Transverse Mercator projection, Zone 11.

Shaded-relief base map from 1:250,000-scale Digital Elevation Model 

based on the North American Datum of 1927. Sun illumination from the northwest

at 40 degrees above the horizon. Intensity of green shading reflects increasing 

elevation between 1500 and 3500 m.

0

0

5

5 10 MILES

10 KILOMETERS

EXPLANATION

 -0.5 to 0.5

 0.5 to 1.5

 1.5 to 3.0

 3.0 to 10.0

10.0 to 25.0

Nevada Test Site boundary

D87Srt values (in per mil deviation 

 from seawater at time of deposition)

NYE COUNTY

CLARK COUNTY

LINCOLN COUNTY

CLARK COUNTY

NYE COUNTY

NEVADA

CALIFORNIA

NYE COUNTY

INYO COUNTY

Amargosa River

Fortymile Wash

500,000 520,000 540,000 560,000 580,000 600,000 620,000 640,000 660,000

4,140,000

4,120,000

4,100,000

4,080,000

4,060,000

4,040,000

4,020,000

4,000,000

UNIVERSAL TRANSVERSE MERCATOR-EASTING, ZONE 11, IN METERS

UNIVERSAL TRANSVERSE MERCATOR-NORTHING, ZONE 11, IN METERS

A.

Figure 12. Spatial distribution of δ87Srt, values for borehole and outcrop samples (A) from the Nevada Test Site vicinity, 

and (B) in and adjacent to the eastern part of the Nevada Test Site, Clark, Lincoln, and Nye Counties, Nevada, and Inyo 

County, California. Multiple samples from boreholes are shown as vertical arrays in order of depth within borehole (not 

to scale) with a leader indicating borehole location.

Strontium Isotopic Compositions  37
Figure 12. Continued.

NV19-4119_fig12B

Nevada Test Site

ER12-1

ER12-3

ER12-4

ER16-1

ER3-1

ER5-3#2

ER6-1#2

ER6-2

ER7-1

HTH#3

UE10j

UE15d

UE16d

UE1c

UE1h

UE2ce

UE7nS

UE-25 a#3

UE-25 p#1

TW-D

TW-C

Army#1

4,120,000

550,000 560,000 570,000 580,000 590,000 600,000 610,000

UNIVERSAL TRANSVERSE MERCATOR-EASTING, ZONE 11, IN METERS

UNIVERSAL TRANSVERSE MERCATOR-NORTHING, ZONE 11, IN METERS

4,110,000

4,100,000

4,090,000

4,080,000

4,070,000

4,060,000

4,050,000

4,040,000

Universal Transverse Mercator projection, Zone 11.

Shaded-relief base map from 1:250,000-scale Digital Elevation Model

using the North American Datum of 1927. Sun illumination from the 

northwest at 40 degrees above the horizon.

EXPLANATION

0

0

5

5 10 MILES

10 KILOMETERS

 -0.5 to 0.5

 0.5 to 1.5

 1.5 to 3.0

 3.0 to 10.0

10.0 to 25.0

Nevada Test Site boundary

D87Srt values (in per mil deviation 

 from seawater at time of deposition)

B.

38 Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
Summary and Conclusions

To contribute to a more accurate understanding of 

regional ground-water flow beneath the Nevada Test Site 

vicinity in southern Nevada using 87Sr/86Sr values, chemical 

and strontium isotope data are reported for rock samples 

representing water-producing horizons in the lower carbonate 

aquifer, as well as in the upper carbonate aquifer and lower 

clastic confining unit. Samples obtained in 2006 include 

core and cutting fragments from 20 boreholes located around 

Yucca Flat, Frenchman Flat, Rainier Mesa, and Mercury 

Valley. Partial digestions using dilute nitric acid were used 

to quantify MgO, CaO, SiO2, Al2O3, MnO, Rb, Sr, Th, and 

U concentrations in carbonate fractions, which constituted 

more than 90 percent of most rocks. Small amounts of 

SiO2 and Al2O3 in leachates are evidence that clay minerals 

may be present in many carbonate samples. Three samples 

containing visible shale or volcanic components have SiO2

concentrations as high as 5–10 weight percent. Dolomites 

have median Sr concentrations of 46.5 micrograms per gram 

(μg/g), substantially lower than the median value of 384.5 

μg/g for limestones. Because both rock types have similar 

Rb concentrations, dolomites tend to have higher Rb/Sr 

ratios. However, these values are low enough in most samples 

so that increases in 87Sr/86Sr caused by decay of 87Rb are 

not substantial. Values of 87Sr/86Sr analyzed from the same 

leachates of dolomites and limestones range from 0.70809 to 

0.72089 and show no dependency on Sr concentrations.

In addition to subsurface samples from NTS boreholes, 

114 samples from outcrop, road cut, and underground 

exposures of Paleozoic carbonates were collected and 

analyzed in the early-to-mid 1990s. These samples are from 

locations to the west, south, and east of the NTS including 

sites in the Funeral Mountains, Bare Mountain, Striped 

Hills, Specter Range, Spring Mountains, and ranges east of 

the NTS. Although results for these samples were discussed 

earlier (Peterman and others, 1994), the data have not been 

published. Like the borehole samples, dolomite tends to have 

lower bulk-rock Sr concentrations (typically 22–96 μg/g), 

whereas limestone tends to have higher Sr concentrations that 

commonly range up to about 500 μg/g. 

The distribution of Sr isotopic compositions from 

carbonate fractions of borehole and outcrop samples are 

skewed toward higher 87Sr/86Sr values. Many samples have 87Sr/86Sr values consistent with Paleozoic seawater 87Sr/86Sr 

values ranging from about 0.7070 to 0.7092. Samples with 

87Sr/86Sr values greater than 0.7093 have experienced postdepositional modification, which was caused by interaction 

with fluids containing radiogenic Sr. Carbonate rocks 

with modified 87Sr/86Sr values are present throughout the 

stratigraphic section. However, rocks with elevated 87Sr/86Sr 

are most common around areas of known mineralization at 

Bare Mountain, and in western Yucca Flat where the upper 

clastic confining unit may contribute radiogenic Sr from clay 

minerals with elevated Rb/Sr. Paleozoic carbonate rocks with 

non-marine 87Sr/86Sr signatures may show mineralogical or 

textural evidence of alteration; however, some samples with 

elevated 87Sr/86Sr show no obvious signs of post-depositional 

modification. The ranges of Sr concentrations and 87Sr/86Sr 

values presented in this report can be used in hydrochemical 

modeling efforts to represent the composition of carbonate 

rock dissolved during regional ground-water flow.

Acknowledgments

Leigh Justet and Gerald E. Magner helped collect core 

and cutting samples archived at the U.S. Geological Survey 

Core Library and Data Center in Mercury, Nevada. Richard 

W. Spengler, Michael D. Carr, Susan A. Monsen, John N. 

Aleinikoff, Fran Singer, and Beth Widman helped collect 

and describe outcrop samples. Shannon Mahan helped make 

strontium isotope measurements on outcrop samples analyzed 

in the early 1990’s. James C. Cole provided outcrop samples 

from parts of the Nevada Test Site and Nellis Air Force Base 

that were off limits to the authors. Technical reviews by 

Leigh Justet and James C. Cole improved the quality of the 

manuscript and stratigraphic unit assignments.

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42  Strontium Isotopic Composition of Paleozoic Carbonate Rocks, Nevada Test Site Vicinity, Nevada and California
For more information contact:

Director, Nevada Water Science Center

U.S. Geological Survey

2730 N. Deer Run Road

Carson City, Nevada 89701

http://nevada.usgs.gov
DS 280 Paces and others

Strontium Isotopic Composition of Paleozoic Carbonate Rocks in the Nevada Test Site

Vicinity, Clark, Lincoln, and Nye Counties, Nevada, and Inyo County, California