Vegetation and Climates of the 

Last 45,000 Ifeetfs in the 

Vicinity of the Nevada lest Site, 

South-Central Nevada

U.S. G EO.LQG tC A L SURVEY P H 0 F E,$ S I O'N A L P ATPE

Qn with the, 

.£ Department ®f Energy
Vegetation and Climates of the 

Last 45,000 Years in the 

Vicinity of the Nevada Test Site, 

South-Central Nevada

By W. GEOFFREY SPAULDING

U.S. GEOLOGICAL SURVEY PROFESSIONAL PAPER 1329

Prepared in cooperation with the 

U.S. Department of Energy

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1985
UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Hodel, Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

Library of Congress Cataloging in Publication Data

Spaulding, W. Geoffrey.

Vegetation and climates of the last 45,000 years in the vicinity of the Nevada test site, south-central Nevada.

(Geological Survey professional paper ; 1329)

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

Bibliography: p.

Supt. of Docs. No.: I 19.16:1329

1. Nevada Climate. 2. Paleoclimatology Nevada. 3. Vegetation and climate Nevada. 4.

Paleobotany Nevada. 

I. Title. II. Title: Nevada Test Site, south-central Nevada. III. United states. Dept. of Energy. IV.

Series. 

QC984.N3S63 1985 551.69793'3 84-600117

For sale by the Branch of Distribution U.S. Geological Survey 

604 South Pickett Street Alexandria, VA 22304
CONTENTS

	Page 

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

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

Objectives of study . . ........... ............ 2

Location of the study area ...................... 2

Regional climate ... .......... .............. 2

Plant communities ..... ......... .......... 4

Acknowledgments... .... .......... ^ ........ 6

Packrat-midden analysis .... .................... 6

Methods ... .......... ............... ..... 7

Sampling ....... ........................ 7

Analysis.... ...................... ..... 8

Modern analogs ..... .... ........... ..... 10

Climatic reconstruction ......................... 15

Radiocarbon dating........ .............. .... 16

The fossil record in selected areas ................... 20

Periphery of Amargosa Desert ................... 20

Specter Range .... .......................... 22

Eleana Range ... ..................... ..... 22

Early records from the Nevada Test Site ........... 23

Sheep Range and Eureka Valley .................. 23

Tule Springs ..... ............... ........... 23

Grand Canyon .......................... .... 24

Late Quaternary vegetation and climate ............... 27

Middle Wisconsin environments .................. 27

Page

Late Quaternary vegetation and climate Continued 

Middle Wisconsin environments Continued

45,000 to 35,000 years before present.....

35,000 to 23,000 years before present 

Late Wisconsin environments .... . . .....

Vegetation .... ... . ... ... ...

. ..... 27

....... 30

. ... .33

..... 33

Climatic regime ....... .... ......... . . 36

The transition period.... ... . . ........ 40

Major vegetation changes ....... ......... 40

Climates of the transition period . . ........ 42

The last 8,000 years ...... .... . . . ......... 44

Middle Holocene climatic variations . . .... ... 44

Late Holocene fluctuations ..... ... . ..... 45

Assessing paleoenvironmental reconstructions .......... 46

Accuracy of representation and general analogs . . ... 46

Elevational displacement ...... . ... ...... 46

Negative evidence ......... ... .... ..... 47

Radiocarbon dating. . ... . . . .... ... ... 47

Future climatic change... .... ..... . ..... .... 47

Atmospheric carbon dioxide ... ... . . .... 48

The next ice age ....... . . . . ....... 48

Summary and conclusions ... .... . . ... ..... 49

References cited ... ... ... ... .......... ... 52

Supplemental data . . . . . .... . . ... ..... . . 57

ILLUSTRATIONS

FIGURE 1. Map showing location of study area, the Nevada Test Site and vicinity, and locations

of figures 2, 12, and 13, and other selected sites ...................... .......................... 3

2. Map showing location of Nevada Test Site and figures 4, 6, 7, and 8 . . ................................... 4

3. Photographs showing the Eleana Range-2 packrat midden: A, General view of external face of the midden;

B, Closeup view of sampling column ......................................................... 7

4. Map showing Eleana Range fossil locality ..... ................ ................................... 8

5. Graphs of diversity as a function of the size of samples from the Specter Range-2 packrat midden .............. 10

6-8. Maps showing:

6. Specter Range and Point of Rocks fossil localities .............. ............................... 11

7. Owl Canyon fossil locality .................. . .............................. ............ 13

8. Last Chance Range fossil locality.......................... ................................ 14

9-11. Stratigraphic sketches of:

9. Sample columns from the Eleana Range-3 packrat midden ....... ................................ 20

10. Sample column from the Eleana Range-2 packrat midden ........................... ............ 21

11. Sample column from the Specter Range-2 packrat midden ....................................... 21

12. Map showing location of packrat-midden sites in the southeastern Sheep Range ............................. 24

13. Map showing location of packrat-midden sites in the western Sheep Range. ................... ............ 25

14. Diagram showing age and elevational distribution of late Quaternary

packrat-midden samples from the northern Mojave Desert ....................................... 26

15. Sketches of the Eleana Range fossil locality: A, Physiography of the Eleana Range-1 and -2 sites;

B, Modern vegetation at the Eleana Range-1 and -2 sites .... ................................... 28

16. Sketches of reconstructions of the Wisconsin vegetation of the Eleana Range fossil locality: A, Full-glacial 

(Wisconsin maximum) limber-pine woodland; B, Juniper-steppe shrub vegetation during the 

middle Wisconsin (about 45,000 years ago)............................................. 29

ill
IV CONTENTS

Page 

FIGURES 17-20. Diagrams showing:

17. Relative frequencies of selected plant taxa in macrofossil assemblages from the Eleana Range-3 midden. . 31

18. Relative frequencies of selected plant taxa in macrofossil assemblages from the Specter Range-2 midden. . 32

19. Distribution of juniper-shrub macrofossil assemblages of middle Wisconsin age

compared to the modern extent of similar associations in the Sheep Range ...................... 34

20. Abundance of selected plant taxa in macrofossil assemblages from the Eleana Range-2 (ER-2) midden ... 35

21. Graph showing changes in similarity between Wisconsin and modern flora of the Eleana Range locality. . ..... 36

22. Diagram showing current elevational range and Wisconsin fossil records of selected trees and shrubs . ... ..... 38

23. Graphs showing tree-ring chronologies from two limber-pine specimens from the

Eleana Range-2 (ER-2) midden........ ........................................... ..... 41

24. Diagram showing a time series of packrat-midden samples from the Eureka View locality,

northern Eureka Valley, Inyo County, California...................................... ..... 43

25. Graphs showing inferred past changes in global-ice volume and modeled future trends ............. ..... 49

TABLES

Page 

TABLE 1. Principal plant-community types and examples of representative plant associations on rock slopes ........... 5

2. Dry weight and percentage composition of different size fractions of packrat-midden samples after

dissolution and washing ................................................................ 9

3. Comparison of key plant taxa in modern packrat-midden debris with plants in the vegetation within

30 meters of the midden site............................................................. 12

4. Temperature and precipitation data from six stations in Nevada...................................... 15

5. Estimated range of values for mean annual temperature and precipitation at four key fossil localities

in the Nevada Test Site and vicinity ...................................................... 16

6. Packrat-midden sites, samples, and radiocarbon dates ............................................. 18

7. Paleoclimatic reconstructions for the full glacial period of the American southwest ....................... 37

8. Estimates of minimum displacement of Utah juniper and limber pine and resultant calculations of the

full-glacial decline in summer temperatures for southern Nevada ................................ 39

9. Range of minimum temperature values at 39 sites presently supporting creosote bush, and estimates

of the decline in late Wisconsin winter temperatures .......................................... 39

10. Summary of estimates of late Quaternary climate for the Nevada Test Site and vicinity ................... 50

TABLES 11-15. Modern packrat middens:

11. Plants in a recent midden from the Owl Canyon 3 site and plants growing in three habitats

within 30 meters ............................................................... 59

12. Plants in a recent midden from the Last Chance Range site and those growing within 30 meters ...... 60

13. Plants in a recent midden from the Specter Range 2 site and those growing within 30 meters ......... 61

14. Plants in a recent midden from the Eleana Range 3 site and those growing within 30 meters ......... 62

15. Plants in recent midden debris from the Connley Hills 1 and 2 sites, and growing within

30 meters of each locality ......................................................... 63

16-25. Ancient packrat middens:

16. Plants from the Owl Canyon (OC) locality................................................. 64

17. Plants from the Point of Rocks (PR) 1 site ................................................ 66

18. Plants from the Point of Rocks (PR) 2 and 3 sites ........................................... 68

19. Plants from the Last Chance Range (LCR) 1 site ........................................... 70

20. Plants from the Specter Range (Spc) 2 site ................................................ 72

21. Plants from the Specter Range (Spc) 3 site ................................................ 74

22. Plants from the Specter Range (Spc) 1 site ................................................ 76

23. Plants from the Eleana Range (ER) 2 site ................................................. 78

24. Plants from the Eleana Range (ER) 3 site ................................................. 80

25. Plants from the Eureka View (EV) fossil locality ........................................... 82
CONVERSION FACTORS V

CONVERSION FACTORS

Metric units in this report may be converted to inch-pound units by using the following conversion factors:

Multiply By To obtain

centimeter (cm) 0.3937 inch (in.)

gram(g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound (Ib)

kilometer (km) 0.6214 mile (mi)

kilopascal (kPa) 10 millibar (mbar)

meter (m) 3.281 foot (ft)

millimeter (mm) 0.03937 inch (in.)

millimeter per year (mm/a) 0.03937 inch per year (in/yr)

square kilometer (km2 ) 0.3861 square mile (mi2 )

cubic meter (m3 ) 35.31 cubic foot (ft3 )

degree Celsius (°C) °F = 9/5°C + 32 degree Fahrenheit (°F)
VI SYMBOLS

SYMBOLS AND DEFINITIONS LIST

Amberat crystalized (dehydrated) packrat urine

AT arboreal taxon (taxa)

14C radiocarbon, carbon-14; unstable isotope of normal 

carbon-12

A relative change in a given parameter (for example, 

ATa, change in mean annual temperature)

Extralocal a species not present in the vicinity of the site of 

its fossil occurrence

Extralimital a species not known to presently occur on a mountain mass where it is recorded as a fossil

Equable a temperature regime characterized by a limited 

seasonal range of temperatures

Full glacial a widely-used synonym for the Wisconsin 

maximum

IS Sorensen's similarity coefficient or index

N number of identified taxa

NISP number of identified specimens

NIS number of taxa of trees, shrubs, and succulents

P precipitation (Pa, average annual precipitation; 

Ps, average summer precipitation; Pw, average 

winter precipitation)

Percent P percent change from present average value of 

precipitation

Mesic relatively moist (mesophytic, characteristic of 

relatively moist habitats)

Pluvial increased rainfall exceeding present annual values 

by at least 50 percent

Paleonidology the study of ancient packrat middens

a standard deviation

T average value of temperature ( Ta, average annual 

temperature; Ts, average summer temperature; 

Tw, average winter temperature)

Percent T percent change from present average value of 

temperature

Thermophile a species characteristic of sere (hot) habitats 

(thermophilous, with an affinity for sere habitats)

Wisconsin the period of greatest development of continental 

maximum ice sheets in the Northern Hemisphere, about 

18,000 years ago

Xeric relatively dry (xerophytic, characteristic of relatively dry habitats)

B.P. radiocarbon years before present (1950). An age 

expressed in radiocarbon years before present is 

a statistical estimate of the remnant carbon-14 

in a given sample and not directly equivalent 

to a sidereal or calendar year age
VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS IN THE 

VICINITY OF THE NEVADA TEST SITE, SOUTH-CENTRAL NEVADA

By W. GEOFFREY SPAULDING

ABSTRACT

Major changes in the climate of the Nevada Test Site have 

occurred during the last 45,000 years. Understanding this climate 

variability is important in assessing the region's suitability for 

permanent nuclear-waste repositories. Future climatic changes 

probably will occur within the time the waste materials are 

hazardous. The nature and magnitude of previous fluctuations 

indicate the nature of future climatic change that may impact on 

a nuclear waste repository. Reconstructions of past vegetation 

are used to infer climatic conditions during the past 45,000 years. 

Plant macrofossils from ancient packrat (Neotoma spp.) middens 

provide the data for these analyses. Middens can be older than 

50,000 years, and they are common in the region. Each contains 

abundant mummified plant fossils, representing the plant species 

growing within about 30 meters of the site. Radiocarbon-dated 

midden samples provide detailed records of climate-induced 

vegetation change.

During the Wisconsin glacial age, from at least 45,000 years ago 

to about 10,000 years ago, juniper (Juniperus osteosperma) 

woodland was widespread below elevations of 1,800 meters in the 

desert lowlands. Steppe shrubs were common, as were shrubs 

typical of the drier phases of current woodland. Late Wisconsin 

subalpine conifer woodland, typified by limber pine (Pinus flexilis), 

occurred at elevations above about 1,800 meters. Plants that 

are sensitive to frigid temperatures, and those restricted to moist 

habitats, are missing or are very rare in the glacial-age macrofossil record.

Development of desert vegetation in the lowlands of the Nevada 

Test Site and vicinity had begun by about 15,000 years ago. 

Timing of the vegetation change from woodland to desertscrub 

was transgressive. At higher elevation desert sites, woodland 

did not disappear until after about 8,000 years ago. The earliest 

records of desert vegetation in the vicinity of the Nevada Test 

Site appear to antedate those from the Sonoran Desert by at 

least 4,000 years.

Climatic conditions at about 45,000 years ago at the Nevada Test 

Site were similar to those of northern Nevada at present. Average 

annual temperature was at least 2° Celsius less than that of 

current average annual temperature. Summers were drier and 

colder, and winter precipitation may have exceeded current 

quantities by 20 percent. By about 30,000 years ago, annual 

temperature may have been 3° to 6° Celsius less than present 

values. The trend toward maximum glacial conditions appears to 

have been reversed briefly several times. By about 18,000 years 

ago, the relative decrease in annual temperature is inferred to 

have been 6° to 7° Celsius. Average summer temperatures were 7° 

to 8° Celsius cooler than those of the present, and winter precipitation exceeded present quantities by as much as 70 percent. 

There was a relative decrease in summer rainfall, and average

annual precipitation probably did not exceed 40 percent of current 

quantities. Postglacial warming began as early as 16,000 years 

ago, and average annual temperatures probably approached 

present values by about 10,000 years ago. Differences exist 

between these paleoclimatic reconstructions and those that 

indicate a "pluvial" rainfall regime during the late Wisconsin. 

Temperatures appear to have been lower and rainfall less than the 

values proposed in models of an equable glaciopluvial.

Increased atmospheric carbon dioxide within the next 500 years 

probably will result in a 2° to 3° Celsius increase in annual 

temperature and intensified rainfall in the Nevada Test Site 

region. Analogs with previous glacial-interglacial cycles indicate 

that this "superinterglacial" may be no more than a relatively 

brief reversal in the protracted trend toward the next ice age. 

Current models indicate that, within the next 10,000 years, 

climatic conditions may be similar to those of the last glacial age.

INTRODUCTION

A fundamental challenge presented by the use of nuclear energy is the safe, long-term disposal of both highlevel and transuranic radioactive wastes. Proper storage 

of these materials, by-products of both commercial enterprises and nuclear weapons manufacture, requires isolation from the biosphere for a period exceeding their 

hazardous duration. Estimates of this duration range 

from 1,000 to 100,000 years (Winograd, 1981, p. 1458; 

Bredehoeft and others, 1978; Interagency Review Group, 

1978). Such lengths of time encompass global climatic 

changes greater than those that have occurred in recorded history. To assure prolonged integrity of any nuclearwaste repository, long-term environmental stability of 

that site needs to be considered, and impact of future 

climatic change needs to be anticipated.

Major global climatic changes occur at regular frequencies of about 10,000 to 100,000 years (Mitchell, 

J.M., 1976; Shackleton and Opdyke, 1973; Berggren and 

others, 1980). Changes from glacial to interglacial 

intervals, and back again, are quasi-periodic. These changes are caused by variations in net global solar-energy 

input, a consequence of the precession of Earth's orbit 

and the obliquity and eccentricity of its axial position 

(Imbrie and Imbrie, 1980, p. 943-944; Sergin, 1980, p.
VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

1480). Based on these findings, computer-simulated climatic models have been devised that indicate a significant probability that a new ice age will begin within the 

next 10,000 years (Imbrie and Imbrie, 1980, p. 949-951). 

The present Holocene Epoch is the last in a long series of 

relatively brief (7,000 to 20,000 years) interglaciations 

punctuating much longer (70,000 to 90,000 years) glaciations (Wright, 1972, p. 279-281; Broecker and Van Donk, 

1970, fig. 2; Berggren and others, 1980, fig. 11). Hence, a 

permanent repository for nuclear waste must withstand 

the effects of a major climatic change that may occur 

well within the hazardous duration of these materials.

OBJECTIVES OF STUDY

A site in or near the Nevada Test Site in south-central 

Nevada (fig. 1) is being evaluated as a permanent repository for both transuranic-contaminated and high-level 

radioactive wastes. The objective of this study is to 

characterize long-term climatic variability inherent to 

this area. Specifically, paleoenvironmental and paleoclimatic reconstructions spanning the last 45,000 years 

are offered to facilitate calculations of potential variations in water-table levels and ground-water recharge 

(Winograd, 1981, p. 1461; Winograd and Doty, 1980, p. 

76-85). Radiocarbon-dated plant macrofossil assemblages from ancient packrat (Neotoma spp.) middens in 

the Nevada Test Site and vicinity provide data for these 

paleoclimatic reconstructions. The uniformitarian assumption is made that climates of the last 45,000 years 

approximate the climates that will occur in the next 

100,000 years.

LOCATION OF THE STUDY AREA

The Nevada Test Site lies within the Basin and Range 

Province of western North America (Fenneman, 1931), 

on the southeastern margin of the physiographic Great 

Basin (Synder and others, 1964; Morrison, 1965) (fig. 1). 

With respect to flora, the site is located on the boundary 

of the Mojave Desert to the south and the Great Basin 

Desert to the north (Cronquist and others, 1972, figs. 55 

and 56). Topography consists of desert valleys with relatively high floors (exceeding 700 m) surrounded by mountains with maximum elevations usually less than 2,100 

m. Highlands of Tertiary volcanic rocks occupy much of 

the northern one-half of the site; while, in the south, 

uplands of Paleozoic carbonate rocks surround alluviated 

valleys. Two internally drained valleys, Yucca Flat and 

Frenchman Flat, are near the western boundary of the 

test site (fig. 2); playa elevation of Yucca Flat is 1,195 m, 

and playa elevation of Frenchman Flat is 939 m. Like

most valleys in southern Nevada, neither shows evidence of having contained "pluvial" lakes of Wisconsin 

age (Mifflin and Wheat, 1979, p. 15).

Some ground-water flow through the Nevada Test Site 

originates in volcanic highlands to the north, Pahute 

Mesa, Timber Mountain, and Yucca Mountain. The 

remainder enters the site from the east as underflow 

within the regional lower carbonate aquifer (Winograd 

and Thordarson, 1975, pi. 1; Winograd and Doty, 1980, 

fig. 1). Flow directions beneath the eastern part of the 

site are south and west from the highlands to springs at 

Ash Meadows in the Amargosa Desert. Ash Meadows is 

the site of an extensive network of springs; evidence 

exists for somewhat greater spring activity during the 

Wisconsin glacial age. Fossil tufa deposits occur as high 

as 40 m above present ground-water level in this area 

(Winograd and Doty, 1980, p. 48).

REGIONAL CLIMATE

South-central Nevada is arid to semiarid; dry air masses dominate upper air flow about 70 percent of the year. 

Continental polar (cool and dry) and continental tropical 

(warm and dry) masses are the most common. Moist 

maritime air (both tropical and polar) occurs with a 

frequency of only about 28 percent. Outbreaks of very 

cold and dry arctic air occur during the winter; however, 

these account for less than 5 percent of the air-mass type 

dominance through the year (Houghton and others, 1975). 

The study area is typified by an arid to semiarid climate, 

and, because evidence exists for increased effective moisture during late Quaternary time, climatic phenomena 

that cause precipitation in this area are of particular 

interest. The Nevada Test Site receives moisture as a 

consequence of two basic storm types: (1) Those resulting from winter cyclonic activity; and (2) those caused 

by intense summer convection.

During the cold season (late autumn through early 

spring), southward migration of the subtropical highpressure zone brings mid-latitude depressions to the 

southwestern United States. Winter precipitation results 

from either frontal-cyclonic (Pacific-type storms) or nonfrontal cyclonic circulation (Great Basin lows) (Houghton 

and others, 1975, p. 14; Bell, 1979, p. 376). In both 

instances, the Sierra Nevada to the west (fig. 1) is a 

major barrier to moist air moving inland from the Pacific. 

Pacific-type storms are caused by fronts trailing southward from eastward moving low-pressure cells. These 

lows are imbedded in prevailing westerlies; their normal 

track is inland from the Pacific Northwest into Canada, 

north of the study area (Bryson and Hare, 1974, fig. 26). 

However, a semipermanent low-pressure trough sometimes develops over the western United States and diverts
118° 117°

INTRODUCTION

116° 115° 114°

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EXPLANATION

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Base data from Defense Mapping Agency 

Operational Navigation Chart G-18

0 ID 20 30 40 50 MILES

0 10 20 30 40 50 KILOMETERS 

FIGURE 1. Location of study area, the Nevada Test Site and vicinity, and locations of figures 2, 12, and 13, and other selected sites.

Pacific-type storms far enough south to affect the study 

area (Sellers and Hill, 1974, p. 16). Southern Nevada 

usually is south of the low-pressure center, and maritime 

air contributing to resultant precipitation comes from 

the southwest. These winds skirt the southern edge of 

the Sierra Nevada that lies to the west of the study area 

(fig. 1), although the Transverse and Peninsular Ranges 

south of the Sierra Nevada create a substantial rainshadow. Maximum rain and snowfall from this type of 

disturbance usually occurs in western and northern 

Nevada (Houghton and others, 1975, p. 15).

In contrast to Pacific-type storms, Great Basin lows 

are non-frontal cyclonic disturbances; they are the chief 

source of winter precipitation in central and eastern 

Nevada. This type of "cut-off low" develops near the 

extremity of a front moving inland from the Pacific and 

is caused by strong thermal contrast between cold air 

behind the front and warmer air ahead of the disturbance

(Houghton and others, 1975, p. 16; Bell, 1979, p. 377). 

Great Basin lows may remain stationary over Nevada 

for a few days, but eventually move eastward under the 

influence of prevailing westerlies. Moisture-bearing winds 

are drawn into the area from the northwest. Although 

they occur less often than Pacific-type storms, Great 

Basin lows are important sources of winter precipitation, 

because the low is centered over the region and may 

remain for several days. Great Basin lows are most 

common from April to June; Pacific-type storms are 

more frequent between October and April (Houghton 

and others, 1975).

When the subtropical high-pressure belt shifts northward during the summer, the study area is removed from 

the effect of mid-latitude depressions. Summer precipitation is rarely the product of large-scale frontal activity; 

instead, it occurs as localized thunderstorms that are 

caused by intense vertical air currents over heated terrain.
VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

116°00'

Figure 6 

», Specter Range

and Point of 

I Rocks Sites

O

30'

B'

5' Base from Army Map Service

Maps NJ11-8, NJ11-9,

NJ 11-11, NJ 11-12

0 5 KILOMETERS

CONTOUR INTERVAL 1000 FEET 

DATUM IS SEA LEVEL

FIGURE 2. Location of Nevada Test Sile and figures 4,6,7, and 8 (see 

fig. I for the relative position of this map). Dots and numbers refer 

to packrat-midden sites discussed by Wells and Jorgensen (1964).

Such convection commonly is combined with orographic 

uplift and covergence over mountains to produce moistureladen thunderheads (Bell, 1979, p. 381; Sellers and Hill,

1974, p. 10). At the Nevada Test Site, about 25 percent of 

the annual precipitation falls during the summer (June 

through early September, Beatley, 1976, p. 21), a small 

proportion compared to values greater than 50 percent 

for summer rainfall in the Sonoran and Chihuahuan 

Deserts to the southeast (Bryson and Lowry, 1955; Hales, 

1974). In these southern deserts, the summer rainfall 

usually lasts from mid-July through early September, 

and results from maritime air carried inland from the 

Gulf of Mexico (Hales, 1974, p. 331; Bryson and Lowry, 

1955, p. 339). This high-level (above 70 kPa) flow is 

circulation on the western edge of the subtropical anticyclone commonly called the Bermuda High. However, 

southern Nevada is beyond the western limit of these 

northwest winds (Mitchell, V.L., 1976, fig. 3; Hales, 

1974, p. 334). Analyses indicate a negligible contribution 

of moisture from the Gulf of Mexico during the summer 

in western Arizona, adjacent Nevada, and California. 

Instead, surface low pressure that develops over heated 

desert terrain generates advective flow of maritime air 

northward from the Gulf of California and the Pacific 

Ocean (Hales, 1974, p. 341; Huning, 1978, p. 79). In the 

late summer (mid-July through mid-September), most of 

the precipitable water aloft in the Mojave Desert appears 

to originate from low-level northern flow, rather than 

from upper-level southeasterlies originating over the Gulf 

of Mexico.

Tropical storms of August through October produce a 

different kind of warm-season precipitation event. These 

low-pressure disturbances originate in the south and 

account for at least 25 percent of annual rainfall in the 

southern California deserts (Court, 1974, p. 212). Resultant precipitation patterns differ from those produced 

by summer thunderstorms; tropical storms are intense 

cyclonic disturbances (such as hurricane Kathleen of 

1976) that affect large areas. However, the majority of 

rain from these storms is restricted to area south of 

latitude 36° north (Huning, 1978, p. 83).

PLANT COMMUNITIES

Adequate reconstruction of paleoenvironments of the 

Nevada Test Site is in part dependent on understanding 

the taxonomy, ecology, and biogeography of the plant 

species currently in the area. Many of these were also 

part of the Wisconsin-age vegetation, and changes in 

their distribution and associations provide important 

clues to the climatic history of the region. Diverse 

topography, geology, and local climates of the Nevada 

Test Site combine to create a complex mosaic of plant 

associations. Vegetation ranges from sparse desertscrub 

(in the sense of Brown and others, 1979) in the lowest 

valleys to well-developed woodland on highlands at ele-
INTRODUCTION

vations above 2,000 m. Only shear cliffs and playa floors 

are devoid of plants. Even seemingly barren Paleozoic 

carbonate hills of the Amargosa Desert support diverse 

communities of widely spaced shrubs and succulents of 

short stature.

The botanical nomenclature used in this report follows 

Beatley (1976) in most instances, with exceptions after 

Munz (1974), Cronquist and others (1972), and Holmgren 

and Reveal (1966). Vegetation analyses focus on plant 

communities of rocky slopes near fossil packrat-midden 

sites. These are areas of relatively heterogeneous vegetation, where rough topography presents a variety of 

microhabitats for different plant species. Vegetation of 

such areas is not well-known because plant ecologists 

usually prefer study sites of uniform topography supporting homogeneous vegetation for their purposes 

(Langford and Buell, 1968, p. 97; Mueller-Dombois and 

Ellenberg, 1974, p. 46-48). So, although principal plantcommunity types recognized in this study (table 1) have 

direct analogs in Beatley's (1976, p. 27-72) treatment of 

the vegetation of the Nevada Test Site, some representative plant associations do not. Plants, such as matchweed 

(Gutierrezia microcephala) and Mohave pepperweed 

(Lepidium fremontii), are common dominants on rocky 

slopes. In contrast, some plant species that typify associations on alluvial fans, such as blackbrush (Coleogyne 

ramosissima) and desert-thorn (Menodora spinescens), 

are less abundant on rocky slopes. Vegetation classification presented in table 1 also differs from Beatley's 

(1976, p. 27-72), in that "transition desert" is not recognized as a plant-community type. Plant associations 

included in the "transition desert" by Beatley (1976, 

p. 41-52), such as those dominated by Coleogyne, LarreaGrayia-Lycium, and Lycium-Grayia, are considered in 

table 1 to be representatives of Mojave desertscrub 

(Brown and others, 1979, p. 10).

TABLE 1. Principal plant-community types and examples of representative plant associations on rock slopes

[Classification system follows that of Brown and others (1979)]

Representative Plant Associations Distribution and Common Associates

Great Basin Conifer Woodland

Pinus monophylla-Quercus gambelii-Juniper-us osteosperma

Pinus monophylla-Artemisia tridentata-Juniperus osteosperma

Volcanic highlands in the northern test site; generally at elevations above 1,950 meters (such as the eastern Pahute Mesa, 

Timber Mountain). Associates include Artemisia tridentata, 

Symphoricarpos longiflorus, Purshia tridentata, and 

Lupinus argenteus.

Highlands at elevations above 1,770 meters; restricted to xeric 

habitats at elevations above 2,100 meters. Common associates include Artemisia nova, Cowania mexicana, Haplopappus nanus, Brickellia microphylla.

Great Basin Desertscrub

Atriplex ccmescens-mixed scrub

Atriplex confertifolia-mixed scrub

The flanks of hills and rocky mesas, usually of volcanic substrate; at elevations from about 1,500 to 2,000 meters. 

Common associates are usually Great Basin desertscrub 

species such as Chrysothamnus nauseosus, C. viscidiflorus, 

Ephedra viridis, Tetradymia canescens, Artemisia nova.

On limestone and dolomite slopes; at elevations from about 

850 to 1,700 meters. Common associates are usually Mojave 

Desert shrubs such as Amphipappus fremontii, Ephedra 

torreyana, Larrea divaricata, Gutierrezia microcephala.

Mojave Desertscrub

Lepidium /Vemontu-mixed scrub

Gutierrezia microcephala-mixed scrub

Ambrosia dumosa-Larrea divaricata

On the talus slopes and ridges of calcareous mountains; at 

elevations from about 1,050 to 1,700 meters. Associates include a diverse complement of upper elevation Mojave 

desertscrub species such as Coleogyne ramosissima, Ephedra 

torreyana, Buddleja utahensis, and Lycium andersonii.

Talus slopes, cliff bases, and ridges; generally at elevations 

below 1,400 meters on calcareous substrates. Common associates include Larrea divaricata, Ambrosia dumosa, Ephedra 

spp., Amphipappus fremontii, Lycium pallidum.

On talus slopes, ridges, and mesas; generally at elevations 

below 1,200 meters. Normally occurring with lower-elevation 

Mojave Desert species such as Peucephyllum schottii, 

Eucnide urens, Gutierrezia microcephala, Echinocactus polycephalus. Atriplex confertifolia is common at some sites.
6 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

Plant associations classified as Great Basin conifer 

woodland are distinguished by dominance of single-needle 

piny on pine (Pinus monophylla) and Utah juniper 

(Juniperus osteosperma). In south-central Nevada, these 

pygmy conifer communities are restricted to elevations 

above 1,800 m. Dominant plant taxa in Great Basin 

desertscrub communities are those with northern floristic affinities, such as shadscale (Atriplex confertifolia) 

(Billings, 1949). These desertscrub associations usually 

occur below woodland, but above Mojave Desert vegetation. The plant species typical of lower elevation Mojave 

desertscrub vegetation, like creosote bush (Larrea 

divaricata) and white bursage (Ambrosia dumosa), have 

their center of distribution south of the Nevada Test 

Site. Exceptions include plant associations dominated 

by species endemic to the northern Mojave Desert, such 

as Shockley's boxthorn (Lycium shockleyi) and Bailey's 

greasewood (Sarcobatus vermiculatus var. baileyi). Many 

Mojave desertscrub species are at the northern limits of 

their distribution in the vicinity of the Nevada Test Site, 

and most are restricted to elevations below 1,800 m.

ACKNOWLEDGMENTS

Research for this study was done at the College of 

Forest Resources, University of Washington, and at the 

Civil Effects Testing Operations laboratory, Mercury, 

Nevada from 1979 to 1981. The counsel and assistance of 

Hans Claassen, Gary Dixon, Estella Leopold, Gene Rush, 

Fiorenzo Ugolini, Bill Wilson, and Ike Winograd are 

gratefully acknowledged. Deborah Naslund and Karen 

Haffnieter provided invaluable assistance in the field 

and laboratory. Radiocarbon dating was done by Steve 

Robinson at the U.S. Geological Survey, Menlo Park, 

facility and by Chris Radnell and Austin Long at the 

Laboratory of Isotope Geochemistry, University of 

Arizona, Tucson, Arizona. Sketches of the ice-age vegetation of the Eleana Range were done by Fred Paillet. 

Others who have aided in this research include Tom 

Ackerman, Ken Cole, Gene Doty, Phil Medica, Auda 

Morrow, Lonnie Pippin, Vera Markgraf, Peter Mehringer, 

Susan Spaulding, Bob Thompson, and Tom Van Devender.

PACKRAT-MIDDEN ANALYSIS

Comprehensive paleoenvironmental reconstruction 

depends on a reliable source of fossils. In temperate 

regions, our knowledge of late Quaternary climates is 

based primarily on organic remains preserved in lakes 

and bogs. However, sedimentary basins in arid regions 

usually do not provide well-preserved fossil remains, and 

other sources of information are required. In the early 

1960's, a new paleoecological tool was introduced, analysis of packrat middens or paleonidology (Wells and

Jorgensen, 1964; Wells, 1976; Spaulding, 1977, p. 3), and 

its use has provided novel insights into the late Quaternary environments of western North America. Paleonidology 

is the reconstruction of past vegetation from plant remains 

preserved in middens deposited in rock cavities by cricetid rodents of the genus Neotoma (packrats, woodrats, 

trade-rats, or go-atters).

All species of Neotoma share an acquisitive behavioral 

trait and construct houses or dens from plant debris 

collected nearby (Finley, 1958; Wells, 1976). Functionally specific areas within a packrat den include nest 

chambers, food caches, and trash middens (Van Devender, 

1973, p. 7-9). Plant debris from trash middens are the 

focus of this study. Middens contain primarily fecal pellets and plant remains in the form of shredded fibers, 

twigs, seeds, leaves, and flowers. Currently active middens are loose debris piles, while ancient middens are 

usually masses solidified by dehydrated urine. Middens 

often serve as urination points, and cementation is caused 

by saturation with urine which, upon drying, encases the 

refuse in a cohesive, crystalline mass. Crystallized packrat 

urine, called amberat, is hygroscopic and rehydrates 

during infrequent periods of high humidity. Capillary 

action draws rehydrated amberat to any fresh break on 

an indurated midden, where it then will dry and recrystallize. Within a few months, new breaks on ancient 

middens are sealed by a shiny layer of recently active 

amberat. Such surfaces are sticky whenever it is humid; 

in time, they incorporate dust and debris to become 

lusterless rinds that are no longer subject to rehydration. 

Hence, indurated packrat middens are self-sealing, with 

typically convoluted rinds that vary in thickness from a 

few millimeters to several centimeters (see figs. 3 and 4 

for views of the Eleana Range-2 midden).

Although the properties of amberat augment longevity of indurated middens, mummification is the prime 

means of preservation. Middens must be sheltered from 

rain in a cave or beneath a rock overhang to be preserved. 

Decomposition is rare in well-sheltered middens. Middens from exposed sites are degraded and of a "punky" 

consistency, with most of the amberat leached out by 

repeated wetting. Extensive termite damage is common 

in such samples. However, given adequate shelter, plant 

fossils from middens remain well preserved. Some are 

more than 50,000 years old and are among the oldest 

fossils preserved by mummification.

In most instances, 80 to 95 percent of the mass of an 

indurated packrat midden is soluble urine and particles 

less than 0.85 mm in size (table 2). Most of the remaining 

5 to 20 percent is composed of fecal pellets and plant 

debris. Identifiable plant remains normally comprise much 

less than 10 percent of the mass of an indurated midden, 

although they commonly number into the thousands per 

kilogram of unprocessed midden.
PACKRAT-MIDDEN ANALYSIS

FIGURE 3. The Eleana Range-2 packrat midden: A. General view of 

the external face of the midden; the rod at the top left of the midden is 

graduated in inches; B. Closeup view of the sampling column after 

removal of the weathering rind; nails are at 10-centimeter intervals; see 

figure 4 for the location of the Eleana Range-2 midden site.

METHODS

Paleonidology is a new scientific discipline with few 

established guidelines and few standardized methods. 

The first time series of macrofossil assemblages from 

single localities only were described in 1980 and 1981 

(Spaulding, 1980; Betancourt and Van Devender, 1981; 

Mead and Phillips, 1981). Therefore, a secondary objective of this study is to develop techniques that increase 

the resolution of inferences drawn from midden analysis 

and to test some assumptions of the discipline.

SAMPLING

Packrat middens occur in a great variety of sizes, 

shapes, and situations within a rock cavity. Guidelines 

for site and sample selection were devised to minimize 

the chances of collecting contaminated samples (those 

containing plant fossils of more than one radiocarbon 

age). Deposits in vertical fissures were not collected, 

because different-age debris falling from above may be 

incorporated into a midden. Middens displaying jumbled stratigraphy were rejected, including most of those 

that were not well-consolidated. Using these criteria, 

about one-half the indurated middens located were 

collected, and about two-thirds of those were chosen for 

detailed analysis.

Most indurated Neotoma middens are less than 0.5 m3 

in volume and provide samples from only a narrow span 

of radiocarbon time. However, larger deposits do exist; 

the volume of some exceed 4 m3 . A series of macrofossil 

assemblages from such a large deposit may span more 

than 10,000 years and is more useful for paleoclimatic 

reconstruction than one or two samples from many isolated sites. Hence, priority was given to locating and collecting those rare, large middens.

A midden judged suitable for analysis is first sketched 

and photographed. A vertical section of weathering rind 

is then removed; the exposed stratigraphy is sketched, 

and the position of samples to be taken is noted. A 

variety of chisels, wedges, and pry-bars are used to 

remove discrete blocks from the indurated mass. Ancient 

middens characteristically contain many minor laminae; 

major stratigraphic boundaries ususally are marked by 

interbedded weathering rinds. Midden sampling is facilitated by their tendency to split along the bedding planes 

defined by laminae. After removal, samples are placed in 

plastic bags. These bags are then wrapped tightly with 

masking tape (to avoid fracturing during transport) and 

labelled.
VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

37° 

07 30"

Base from US. Geological Survey Tippipah 

Spring, Rainier Mesa, Ammonia Tanks, and 

Buckboard Mesa 7 1/z minute quadrangles

0 1 MILE

0 1 KILOMETER

CONTOUR INTERVAL 100 FEET 

DATUM IS SEA LEVEL

FIGURE 4. Eleana Range fossil locality. (Sec figure 2 for the relative 

position of this map.)

All plant species within 30 m of a midden site are 

inventoried. Supplemental data are taken on other trees, 

shrubs, and succulents, and plant-community types, within 0.5 km of the site. Woody plants growing within 30 m 

were subjectively assigned the following abundance classes according to their importance in the local vegetation: 

5, very abundant; 4, abundant; 3, common; 2, occasional; 

1, rare. Most grasses and forbs are designated by an "X" 

in the modern plant lists, indicating their occurrence 

within 30 m of the midden sites.

ANALYSIS

In the laboratory, each midden sample is examined for 

stratification and, if necessary, split into subsamples for 

analysis. Samples are cleaned, weighed, rinsed ufcder 

running water, and then immersed in warm water. Smaller subsamples usually are saved for pollen analysis. 

Immersion for 2 to 4 days is usually sufficient to dissolve 

the amberat in most indurated samples, releasing the 

plant macrofossils. Upon disaggregation, the mass is 

washed through a nested pair of No. 6 (3.35-mm mesh) 

and No. 20 (0.85-mm mesh) 12-inch (30.5-cm) Tyler1 soil 

sieves. Material captured on the sieves is flushed with 

warm water, knocked onto paper blotters, and then dried 

in a forced-air oven at 50°C for 6 to 12 hours. The dried 

debris then is stored in labelled plastic bags. Prior to 

sorting, the debris is dry sieved through Nos. 6 and 20 

screens to disaggregate fibrous clots that develop on 

the screens during wet-sieving and to remove remaining 

fine chaff. The different size fractions are then weighed 

(table 2).

Identifiable plant fragments and faunal remains are 

handsorted and placed in labelled plastic vials. Identifications are made by comparing the fossils with modern 

reference specimens under a stereo-dissecting microscope. 

Certain biases are incorporated into identification of this 

fragmentary plant material. Grasses and composites 

(Poaceae and Asteraceae) are frequently difficult to identify under these circumstances (Van Devender, 1973, p. 

16-17; Spaulding, 1981, p. 76-79). Those that could not 

be identified to genus were grouped into the categories 

"Poaceae undetermined" or "Asteraceae undetermined." 

Similarly, fossils of plant genera with morphologically 

similar species were often difficult to identify to the 

species level. Hence, such fossil taxa as "Artemisia sec. 

Tridentatae," "Ephedra sp.," and "Eriogonum sp."

Traditionally, subjectively assigned relative values 

have been used to describe the abundance of taxa in a 

midden assemblage (for example, Wells and Berger, 1967; 

Phillips, 1977; Spaulding, 1981). This method was not 

used. Instead, the fossil data are reported in terms of the 

number of specimens counted in each midden sample 

(see Supplemental Data section). Relative abundance of 

a fossil taxon can be expressed as a percentage of the 

total number of identified specimens (NISP) counted in 

a sample (Grayson, 1979). One problem with this approach 

is the remains of a single aboreal taxon (AT) generally 

will be so abundant that they are impractical to count. In 

such instances, the total number of identified specimens 

minus the arboreal taxon (NISP-AT) still provides a 

useful parameter for calculating relative frequencies of 

all other fossil types. Relative importance of a superabunJUse of trade and firm names in this report is for identification purposes only 

and does not constitute endorsement by the U.S. Geological Survey.
PACKRAT-MIDDEN ANALYSIS 9

TABLE 2. Dry weight and percentage composition of different size fractions of packrat-midden samples after dissolution and washing 

[Wtw, sum of weight of the 3.35-millimeter and 3.35 0.85-millimeter fractions; Wti, initial weight of sample; ER, Eleana Range; Spc, Specter Range; PR, Point of Rocks;

OC. Owl Canyon; LCR Last Chance Range]

Site and 

sample 

no.

ER-2(1)

ER-2(2)

ER-2(3)

ER-214)

ER-2(5)

ER-2(6)

ER-2(7)

ER-2(9)

ER-2(10)

ER-2(11)

ER-3(2)

ER-3(3)

ER-3(4)

ER-3(6)

ER-3(7)

ER-3(8)2

ER-3(8)3

ER-3(9)

ER-3(10)

Spc-l(l)

Spc-l(2)

Spc-2(2)i

Spc-2(2>2

Spc-2(3)

Spc-2(6)

Spc-2(8)

Spc-2(10)

Spc-2(llh

Spc-2(ll)2

Spc-2(12)

Spc-3 A( 1 )

Spc-3A(2)

Spc-3B

PR-l(l)

PR-K3)

PR-2(2)

PR-2(3)

PR-3

OC-2(1)

OC-2(3)

OC-3U)

OC-3(2)

LCR-K2)

LCR-K3)

Initial 

weight 

(grams)

437

501

460

778

903

1,545

798

1,155

1,826

937

937

667

1,498

1,430

1,327

1,270

2,522

615

689

635

524

374

994

991

758

513

206

289

933

934

1,171

808

567

880

629

699

1,000

712

345

588

755

730

382

462

Weight of recovered material (grams) for the indicated 

size fractions (millimeters) below

3.35

18.6

32.1

53.2

35.2

37.8

92.2

64.1

58.5

58.4

18.7

74.9

54.1

165.1

77.0

120.5

89.0

221.5

46.2

27.2

110.0

161.0

29.8

104.0

38.8

14.4

34.5

6.6

55.0

71.0

22.0

21.9

26.7

11.2

26.2

41.5

23.6

70.9

9.3

15.0

36.2

6.9

20.0

8.9

17.6

3.35--0.85

25.5

26.1

22.5

36.7

28.8

108.3

45.8

54.6

112.1

48.8

32.7

43.0

71.5

49.2

71.0

58.2

112.1

36.0

35.6

47.0

48.0

28.0

60.0

57.4

16.6

26.3

12.9

32.0

13.0

47.1

53.9

51.6

30.9

30.1

27.3

22.6

40.1

50.1

22.9

37.2

17.5

18.1

12.0

28.0

1 ,0.85

4.2

6.1

5.7

8.8

4.4

22.7

11.0

15.1

41.3

14.7

17.3

21.2

38.5

20.3

27.0

30.6

75.7

20.2

16.6

10.0

9.0

7.1

11.0

15.4

17.2

12.2

5.2

4.0

13.0

13.9

10.6

13.8

7.5

12.1

12.4

9.2

17.7

21.4

10.6

12.5

4.2

7.1

3.6

12.7

Wtw

44.1

58.2

75.7

71.9

66.6

200.5

109.9

113.1

170.5

67.5

107.6

97.1

236.6

126.2

191.5

147.2

333.6

82.2

62.8

157.0

209.0

57.8

164.0

96.2

61.0

60.8

19.5

87.0

151.0

69.1

75.8

78.3

42.1

56.3

68.8

46.2

111.0

59.4

37.9

73.4

24.4

38.1

20.9

45.6

Wtw 

7^ xlOO Wti

(percent!

10.1

11.6

16.5

9.2

7.4

13.0

13.8

9.8

9.3

7.2

11.5

14.6

15.8

8.8

14.4

11.6

13.2

13.4

9.1

24.7

39.9

15.5

16.5

9.7

8.0

11.9

9.5

30.1

16.2

7.4

6.5

9.7

7.4

6.4

10.9

6.6

11.1

8.3

11.0

12.5

3.2

5.2

5.5

9.9

'Dry sieve only.

dant fossil type can be expressed as a concentration 

value. Preliminary analyses indicate that a useful parameter is the ratio of the weight of the fossils of a superabundant species to the weight of the sorted midden sample 

(all identifiable macrofossils and fecal pellets removed).

In this study, NISP counted in single assemblages 

ranges from 192 to 2,674. A minimum number of 1,000 

identified specimens was counted whenever possible. 

Variations in the number of identified plant taxa (N) in 

samples from the Specter Range-2 midden, as functions
10 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

of sample weight after washing and NISP, are presented 

in figure 5. Point of Rocks and Specter Range fossil 

localities are shown in figure 6. It appears that samples 

weighing less than 70 g after washing (about 350 to 

700 g initial weight, depending on amberat concentration) (table 2), or those with a NISP of less than 600, 

many provide underrepresentative estimates of N.

A widely used similarity coefficient proposed by 

Sorensen (1948) takes the form:

A + B 

where

IS ( similarity index ) is a percentage of the total number of taxa in both samples, with possible values 

ranging from 0 (none in common) to 100 (all taxa 

shared);

c is the number of plant taxa common to two samples;

A is the number of taxa in one sample; and

B is the number of taxa in the other. 

This formula gives weight to the species recurring in 

two assemblages (Mueller-Dombois and Ellenberg, 1974, 

p. 215) and, as a consequence, may be less sensitive to 

random variability in midden content. The total number 

of trees, shrubs, and succulents (Nts ) is used to compute IS, eliminating some of the bias created by the 

difficulty in identifying grasses and herbaceous species. 

If two samples have a taxon that is identified to genus 

in one and species in another (such as Ephedra viridis 

and Ephedra sp.), they are considered identical in computing IS.

MODERN ANALOGS

Validity of these paleoecological reconstructions rests 

on the fidelity with which macrof ossil assemblages reflect 

past vegetation. Neotoma forages only within a limited 

area around the den. Studies of different packrat species 

indicate that foraging distances seldom exceed 30 m and 

then only when brush or broken terrain provide cover 

(Bleich and Schwartz, 1975; Stones and Hayward, 1968; 

Cranford, 1977; Raun, 1966). Therefore, plant fossils 

from a packrat midden are autochthonous and represent 

only local paleovegetation.

Analysis of active packrat middens from different 

vegetation types addresses two interrelated questions: 

( 1 ) How closely do relative proportions of plant fragments 

correspond to their relative abundance in the local 

community; and (2) how complete an inventory of local 

vegetation is the list of plant taxa from a midden? Modern 

middens were treated in the same manner as fossil samples. 

Approximately 1 kg of loose debris was collected from a 

midden in a currently active den. A subsample of about 

500 g was soaked for a short time to simulate the

21, 

20- 

19 - 

18 

17 

16 

I 5 

14 

3 13 ~

$12- 

d 11 -

05 1Q __ 8 ?oo

li_ 

LL. 

O

H 21

£ 20 

119 

118

17

16 

15

14

13

12

II 

200 300 400 500 600 700 800 900 1000 1100

NUMBER OF IDENTIFIED SPECIMENS 

EXCLUDING ARBOREAL TAXA (NISP-AT)

10 20 40 60 80 100 120 140 160 180 200 

WEIGHT AFTER WASHING (Wtw), IN GRAMS

FIGURE 5. Diversity as a function of the size of samples from the 

Specter Range-2 packrat midden (data are from table 2). See figure 6 for 

the location of the Specter Range-2 midden site.

disaggregation treatment used on indurated middens; 

then it was wet-sieved and dried. Dry-sieving, sorting, 

and identification followed. NISP in these modern samples 

ranged from 999 to 2,069 (see Supplemental Data section). 

Indices of similarity between local vegetation and modern 

midden assemblages ranged from 67 to 84. These compare 

favorably with an average IS of 77 for 6 assemblages less 

than 1,200 years old from the Grand Canyon (Cole, 1981, 

p. 38) and an IS of 77 for a single modern midden from 

the Sheep Range (Spaulding, 1981, p. 70). An additional 

two modern middens from the Connley Hills, outside the 

study area in southeastern Oregon (lat 43° 16' N., long 

121°04' W.), were analyzed because these sites occur in 

low-diversity vegetation. Indices of similarity for these 

samples were higher than those for middens from the 

study area, 91 and 100, presumably because of the low 

number of plant species at the sites.

Between 17 and 27 percent of the plant taxa noted in 

the modern middens from the Nevada Test Site and 

vicinity were not observed at the midden sites. Most of 

these are rare occurrences in the midden samples, usually 

represented by relative percentages (of NISP) of less 

than 1 percent. Of the plant species in the current 

vegetation within 30 m of the sites, between 16 and 32
PACKRAT-MIDDEN ANALYSIS

07'30"

11

Base from U S. Geological Survey 

Specter Range 15 minute quadrangle

5 MILES

0 1

CONTOUR INTERVAL 200 FEET 

DATUM IS SEA LEVEL

FIGURE 6. Specter Range and Point of Rocks fossil localities (see figure 2 for the location of this map).

percent (excluding the Connley Hills samples) were not 

found in the modern midden debris. Again, most of these 

species are rare at the site today; none are common 

or abundant.

An array of the common species in the modern plant 

associations and active packrat middens is presented in 

table 3. The Owl Canyon-3 (fig. 7), Last Chance Range- 1 

(fig. 8), and Specter Range-2 (fig. 6) sites support Mojave 

desertscrub vegetation. The Eleana Range-3 (fig. 4)

and Connley Hills-1 sites are at transitions from Great 

Basin desertscrub to woodland; Connley Hills-2 is in an 

open juniper woodland. As mentioned previously, local 

vegetation of the Connley Hills sites is of low diversity 

(JVfS = 5). Modern middens at this locality provide a contrast with those from sites supporting relatively diverse 

vegetation in southern Nevada (Ms = 14 to 19).

Differences occur between observed abundance of plant 

species in modern vegetation and their frequency in
12 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 3. Comparison of key plant taxa in modern packrat-midden debris with plants in the vegetation

within 30 meters of the midden site

[See tables 11-15 in Supplemental Data section for a complete list of the plant species involved at each site; %, percent; NISP. number of identified specimens]

Current vegetation 

(relative abundance)

Site

Owl Canyon-3

Last Chance

Range- 1

Specter Range-2

Eleana Range-3

Connley Hills- 1

Abundant (4-5)

Ambrosia

dumosa

Gutierrezia

microcephala

Ambrosia

dumosa

Larrea

divaricata

 

Atriplex

canescens

Artemisia

tridentata

Chrysothamnus

nauseosus

Common (3)

Eucnide

urens

Peucephyllum

schottii

Pleurocoronis

pluriseta

Atriplex

confertifolia

Bromus rubens

Buddleja

utahensis

Eucnide urens

Atriplex

confertifolia

Ephedra

torreyana

Eriogonum

heermannii

Gutierrezia

microcephala

Prunus

fasciculata

Scopulophila

rixfordii

Stipa arida

Artemisia

tridentata

Stipa sp.

Ephedra viridis

Poaceae undet.

Occasional (2)

Echinocactus

polycephalus

Gutierrezia

microcephala

Nicotiana

trigonophylla

Stipa arida

Brickellia

watsonii

Buddleja

utahensis

Artemisia nova

Haplopappus

nanus

Pinus

monophylla

Symphoricarpos longiflorus

Juniperus

osteosperma

Bromus

tectorum

Abundant 

( >20 percent)

Larrea

divaricata

(37%)

Gutierrezia

microcephala

(22%)

Larrea

divaricata

(46%)

Atriplex

confertifolia

(42%)

Ephedra

torreyana

(21%)

Atriplex

canescens

(39%)

Poaceae undet.

(56%)

Juniperus

occidentals

(27%)

Recent midden 

(percent of NISP)

Common 

5<20 percent)

Linanthus sp.

(8%)

Eucnide urens

(6%)

Atriplex

confertifolia

(12%)

Ambrosia

dumosa (8%)

Eucnide urens

(5%)

Scopulophila

rixfordii

(12%)

Prunus

fasciculata

(8%)

Poaceae undet.

(18%)

Cowania

mexicana

(15%)

Pinus

monophylla

(8%)

Juniperus

osteosperma

(7%)

Chysothamnus

sp. (9%)

Occasional 

(2s 5 percent)

Cryptantha sp.

(4%)

Peucephyllum

schottii(3%)

Ambrosia

dumosa (3%)

Aristidasp. (2%)

Mortonia

utahensis

(4%)

Ephedra sp.

(3%)

Buddleja

utahensis (3%)

Brickellia

desertorum

(2%)

Buddleja

utahensis

(2%)

Poaceae undet.

(2%)

Oryzopsis

hymenoides

(3%)

Artemisia sec.

Tridentatae

Chrysothamnus

nauseosus (2%)

Bromus

tectorum (2%)
PACKRAT-MIDDEN ANALYSIS 13

TABLE 3. Comparison of key plant taxa in modern packrat-midden debris with plants in the vegetation

within 30 meters of the midden site Continued 

|See tables 11-15 in Supplemental Data section for a complete list of the plant species involved at each site; %, percent; NISP, number of identified specimens)

Current vegetation

(relative abundance)

Site Abundant (4-5) Common (3)

Connley Hills-2 Crysothamnus Artemisia

nauseosus tridentata

Bromus

tectorum

Juniperus

occidentalis

Abundant

Occasional (2) ( 20 percent)

Poaceae undet. Juniperus

occidentalis

(58%)

Recent midden

(percent of NISP)

Common

5<20 percent)

Chrysothamnus

nauseosus

(13%)

Poaceae undet.

(9%)

Artemisia

tridentata

(8%)

Sysimbrium sp.

(5%)

Occasional

(2^5 percent)

Chenopodium

cf. botrys (3%)

Chrysothamnus

sp.

116°12'30"

Amargosa Flat Th minute quadrangle

1MILE

1 KILOMETER

CONTOUR INTERVAL 200 FEET 

DATUM IS SEA LEVEL

FIGURE 7. Owl Canyon fossil locality. See (fig. 2 for the location of this map; 

position of the Owl Canyon-1 site is approximate.)

midden assemblage (table 3). Those species rated as 

common or abundant in modern vegetation (relative 

abundance values of 3 to 5) are not always common or 

abundant (relative frequencies > 5 percent) in modern

midden assemblages. Some shrubby Asteraceae appear 

underrepresented; however, there are exceptions, such 

as the abundance of Gutierrezia microcephala in the Owl 

Canyon-3 assemblage (table 3). Larrea divaricata appears 

over-represented in the Owl Canyon-3 midden, as does 

Juniperus in both modern assemblages from the Connley 

Hills. However, Larrea appears proportionately represented in the Last Chance Range-1 assemblages, as does 

Juniperus in the Eleana Range-3 sample. The Connley 

Hills-1 midden is of particular interest. The nearest 

junipers are at the woodland border, about 28 m from the 

rock shelter containing the midden, and there are none in 

the Chrysothamnus-dorrimated association nearer the 

site. Nevertheless, juniper twigs and seeds comprise 27 

percent of identified plant debris from the midden.

These data indicate that, in general, cacti are not 

disproportionately abundant in the packrat middens 

sampled. Pricklypear (Opuntia erinacea) occurs in the 

vicinity of Eleana Range-3, and barrel cactus (Echinocactus polycephalus) grows close to the Owl Canyon-3, 

Specter Range-2, and Last Chance Range-1 sites. Neither 

species is well-represented in those respective middens. 

Nor is the beavertail pricklypear (Opuntia basiliaris) 

(armed with many small spines) well-represented in the 

Owl Canyon-3 or Last Chance Range-1 assemblages.

Limber pine (Pinus flexilis) macrofossils occur as 

contaminants in recent midden debris from the Eleana 

Range-3 site. These three needle-fragments probably came 

from the large Pleistocene midden less than 2 m away, 

pieces of which litter the floor of the rock shelter. As both 

Cole (1981, p. 58-60) and Phillips (1977, p. 36) note, older 

material may contaminate a younger midden. However, 

recognizable contaminants of Wisconsin age (such as 

juniper twigs) were not found in recent midden debris 

from the Owl Canyon-3, Last Chance Range-1, or Specter 

Range-2 sites, even though each of these shelters also 

contains an ancient midden.

In summary, it appears the important plant species in
14 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

36°1 7'30'

36°15'

Base from U.S Geological Survey 

High Peak Th minute quadrangle

1MILE

1 KILOMETER

CONTOUR INTERVAL 200 FEET

WITH SUPPLEMENTARY

100-FOOT CONTOURS (DASHED)

DATUM IS SEA LEVEL

FIGURE 8. Last Chance Range fossil locality. (See fig. 2 for the location of this map.)

the vegetation are not always important constituents of 

modern packrat debris piles. However, the inverse of this 

observation is not necessarily true. The abundant taxa 

in the middens are usually common consituents of the

surrounding vegetation. Variations in proportionality 

appear to include bias both for and against individual 

plant species. Invariably there seem to be several species 

present in the modern vegetation that are not observed
PACKRAT-MIDDEN ANALYSIS 15

TABLE 4. Temperature and precipitation data from six stations in Nevada

[Data from U.S. Weather Bureau, 1965, and Environmental Data Service, 1961-78. Abbreviations for vegetation types are: Gds, Great Basin desertscrub; Mds, Mojave

desertscrub; wd. pinyon-juniper woodland, m, meter; mm, millimeter; °C, degrees Celsius]

Station ( vegetation ) ...

North latitude; west longitude . 

Elevation (m) . . . . 

Parameter . . ...

1931-60 

1961-78.

Station (vegetation) . . .

North latitude; west longitude 

Elevation (m) 

Temperature and precipitation . 

parameter ... ... ....

1931-60. . . ..........

1961-78 . ........

Beatty(Mds)

37°00'; 116°43' 

1,082 

Average Average 

temperature precipi- 

(°C) tation 

(mm)

January July Annual

5.2 26.3 15.0 134.6 

116 116 19 117

Austin (wd)

39°30'; 117°05' 

2,014 

Average Average 

temperature precipi- 

(°C) tation 

(mm)

January July Annual 

. -1.3 21.1 8.6 302.3

. -.8 21.4 8.6 364.9

117 117 114

Winnemucca (Gds)

40°54'; 117°48' 

1,311 

Average Average 

temperature precipi- 

(°C) tation 

(mm)

January July Annual 

-2.1 21.7 8.8 

-1.2 22.3 9.4 

117

Eureka (wd)

215.1 

205.4 

117

39°31'; 115°58' 

1,994 

Average Average 

temperature precipi- 

(°C) tation 

(mm)

January July Annual

-2.1 21.0 8.0 

J 14 114 U4

348.6 

i 14

Elko(Gds)

40°50'; 115°47' 

1,547 

Average Average 

temperature precipi- 

(°C) tation 

(mm)

January July Annual 

-4.9 20.8 7.4 

-3.9 21.2 7.9

Ely (wd/Gds

248.4 

254.4

)

39°17'; 114°51 r 

1,906 

Average Average 

temperature precipi- 

(°C) tation 

(mm)

January July Annual 

-5.6 19.7 6.8 

-4.9 19.7 6.8

221.0 

244.7

'Number of years of record (1961-78) if less than 18.

in the midden debris, and several species in the midden 

that are not found within the arbitrary 30-m foraging 

radius. The practical upper limit of Sorensen's (1948) 

similarity indices between middens and contemporary 

vegetation appears to be about 85 percent where plant 

communities are reasonably diverse (more than 15 woody 

species within a 30-m radius).

CLIMATIC RECONSTRUCTION

Inferences of past climate are made from plant fossils 

and are based on the premise that there have been no 

significant changes in environmental requirements of 

these species during the last 50,000 years. There is 

abundant evidence for stability in the morphology of the 

species used as climatic indicators; however, the hypothesis that genotypes are stable over such time periods is 

untestable. This study presents quantitative climatic 

reconstructions based on changes in plant-species distribution and comparisons between estimated climate 

considered necessary to support a given fossil-plant 

association and climate that currently exists at that site. 

Two sources of modern climatic data are used. The first 

source is data collected by Beatley (1974, 1976) for the 

express purpose of delimiting climatic variables responsible for present vegetation distribution in the Nevada 

Test Site. The second source is U.S. Weather Bureau

records of precipitation and temperature for six selected 

stations in Nevada (table 4). Four stations (Beatty, 

Eureka, Ely, and Austin) are in upland settings rather 

than near valley bottoms; the environment at these sites 

is more comparable to that of upland fossil sites. The two 

data sets are not directly comparable because the 

instrument stations used by Beatley (1974, p. 250) were 

at plant level (30 cm), and of different design than those 

of the U.S. Weather Bureau (at 1.5-m height). Temperature 

values presented by Beatley (1974, p. 250) are obtained 

from maximum-minimum thermometers; mean values 

are derived by averaging extreme temperatures recorded 

during the 2-week interval between readings.

The first step in these reconstructions is to estimate 

present climate of the fossil site. Data provided by Beatley 

(1974, table 1) are used to extrapolate estimated ranges 

of temperature and precipitation at fossil localities. One 

uncertainty is that most midden sites are on steep slopes, 

where orientation to the sun and relative elevation are 

important determinants of local climate. In contrast, 

Beatley's stations are on gentle slopes where orientation 

and relative altitude are less important, but where the 

effect of nocturnal cold-air drainage may be more pronounced. Such factors were considered when the current 

climatic parameters for critical fossil localities were 

estimated (table 5). The second step is to estimate the 

climate represented by a given fossil-plant assemblage, a
16 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 5. Estimated range of values for mean annual temperature and precipitation at four key fossil localities in the

Nevada Test Site and vicinity

(Habitat abbreviations are: Af, alluvial fan; MR. mesa top or ridge top; TL. talus slopes and ledges; W, dry wash. Abbreviations for plant species are: 

Amdu, Ambrosia dumosa; Arno, Artemisia nova: Artr. Artemisia tridentata; Atca. Atriplex canescens; Atco. Atriplex confertifolia; Gumi, Gutierrezia microcephala; Hysa. 

Hymenoclea salsola; Juos, Juniperus usteosperma; Ladi, Larrea divaricata; Lypa, Lycium pallidum: Pimo. Pinus monophylla: Prfa. Prunus fasciculata; m, meter: mm. millimeter: °C, degrees Celsius]

Habitats Vegetation

Estimated 

values for 

Analogous climatic stations' fossil locality

Eleva- Orientation 

Site) si tion (from grid Primary 

(m) north 1

Eleana Range 1,805

-2 and -3

Specter 1,190

Range-2

Point of 900

Rocks-1

Owl Canyon 795

-2 and -3

180°- TL

205°

15°- TL

25°

147°- TL

230°

180°- TL

230°

Site 

Secondary Tertiary Primary Secondary Tertiary No.

MR Af Atca Juos- Arno- 61

Pimo Artr 62

65

MR Gumi- Atco 2

Prfa 3

4

30

31

Af W Lypa- Ladi Hysa 1

Gumi 2

20

38

 W Amdu Gumi- 1

-Ladi Amdu 7

8

9

Mean 

Eleva- Vege- precipitation tation tation 

(m) type (mm)

1,756 Arno 206.0

1,750 Artr 205.5

1,676 Atca 183.6

1,088 Ladi 169.4

1,038 do. 176.3

1,055 do. 148.1

943 Atca 126.0

940 Atco 131.1

1,027 Ladi 140.7

1,088 do. 169.4

994 do. 136.4

949 Lypa 121.9

1,027 Ladi 140.7

963 do. 124.0

938 do. 120.1

989 do. 132.3

Mean 

temperature

(°Cl

12.4

11.9

10.9

14.5

16.7

14.7

13.5

13.5

15.2

14.5

14.7

13.7

15.2

14.5

16.2

14.2

Mean Mean 

precipi- temper- Remarks 

tation ature 

(mm) ( U C)

215- 11- Fossil locality

225 12 less than 1

kilometer

from sites

61 and 62.

170- 13- Fossil locality

190 14 less than 1

kilometer

from site 3.

110- 13.5- Fossil locality

120 14.5 in the bottom

of a canyon.

105- 16.5-

115 17.5

'From Beatley (1974, table 1).

process with even more uncertainties. In this analog 

approach, dominant plant species in macrofossil assemblages are assumed to characterize the local paleocommunity. If, for example, a midden contains abundant 

juniper and sagebrush with other Great Basin Desert 

shrubs, then temperature and precipitation values are 

estimated that coincide with sites at the lower limit of 

woodland in a relatively dry part of the State, where 

juniper grows with such shrubs today. In contrast, if a 

macrofossil assemblage contains abundant juniper and 

pinyon pine associated with woodland shrubs, then 

extrapolated climatic values are derived from sites that 

support such vegetation today, well above the lower 

limit of woodland. The range of present values at the 

fossil site are then subtracted from estimated values for 

past climate to derive changes in mean annual temperature 

( AT) and precipitation. Precipitation change is expressed 

as a percent change from present values (percent P). 

Values of ^47"and percent P should be comparable, whether 

derived from Beatley's data base or U.S. Weather Bureau 

records, provided that separate sets of calculations 

consistently use one or the other. This approach represents only the first approximation to interpret an 

extensive fossil record.

RADIOCARBON DATING

Questions concerning the dating of packrat middens 

are as critical as those addressing the representative 

nature of the plant macrofossil assemblage. It is assumed 

that macrofossils from a midden sample are contemporaneous within the standard deviation ( la) of that sample's 

radiocarbon ( 14C) age. The mixing of different-age macrofossils would lead to erroneous species associations, 

compromising paleoenvironmental reconstructions derived from them.

If the assumption of contemporaneity holds true, 

satisfactory dates could be obtained from any fraction 

of a packrat midden. Materials used for radiocarbon dating packrat middens range from whole samples of leafy 

strata and uriniferous residue (Wells and Jorgensen, 

1964, p. 1172; Wells, 1977, p. 239) to Neotoma fecal 

pellets and fragments of single plant species (Van Devender, 1977a, p. 237). Because mixing of different-age material is a possibility, a monospecific date is a more reliable 

estimate of the age of occurrence of that species (Van 

Devender, 1973, p. 31-33; Phillips, 1977, p. 21-22; 

Cole, 1981, p. 32). Multiple radiocarbon dates, using
PACKRAT-MIDDEN ANALYSIS 17

different materials, should be used to verify the age of 

critical samples.

An assessment of 21 multiple-dating tests on packrat 

middens used in various studies (Spaulding, 1981, table 

6) shows that 17 of the 58 radiocarbon dates were not 

within the expected age range at 10. Some of these tests 

were performed because contamination was suspected; 

excluding these tests leaves 11 dates that represent 

unanticipated discordancies. Caution is needed in evaluating a macrofossil assemblage controlled by a single 

radiocarbon date.

A total of 71 samples were dated using carbon-14 techniques (table 6). Nineteen of the 46 macrofossil assemblages collected in the vicinity of the Nevada Test Site 

were dated at least twice. In addition, this study was 

designed to intensively sample large middens from a few 

sites to gain chronologic continuity at individual localities.t Twelve middens from 7 localities were analyzed 

(table 6). Contrasts between samples thus could be used 

to identify anomalous assemblages that then were redated 

to verify their age.

The Eleana Range-3 packrat midden is of particular 

interest because of its great age and large size. It was 

subject to intensive radiocarbon analysis in an attempt 

to verify the ages of some of the oldest dated assemblages 

from the Southwest. Multiple dates are particularly important on samples with finite dates older than 30,000 

years, when the quantity of radiocarbon remaining in a 

sample is extremely small. Materials dated were curl-leaf 

mountain mahogany (Cercocarpus ledifolius) and Utah 

juniper (Juniperus osteosperma) wood, limber-pine (Pinus 

flexilis) seed coats, Neotoma fecal pellets, unidentified 

twigs, and undifferentiated organic debris (a mix of 

sticks, fecal pellets, and plant fiber) (table 6). Other than 

the wood and seeds, monospecific samples could not be 

dated. Fragments of a single plant taxon rarely were 

abundant enough to provide the minimum 10 g desired 

to date a sample older than 30,000 years.

Most of the units from the Eleana Range-3 midden 

appear to be contaminated. Multiple-dating tests were 

done on eight assemblages after the first series of radiocarbon ages failed to demonstrate normal superposition 

(fig. 9). Only one of the assemblages yields paired dates 

that are concordant at 10, ER-3(7)2 (table 6). Multiple 

ages on samples ER-3(3) and 3(8)s overlap at 20. The 

range of dates from the midden is from 14,200 to 49,900 

B.P. (radiocarbon years before the present) (table 6). 

Anomalously young ages occur at the bottom of two of 

the three sample columns (fig. 9). Dates on large pieces 

of wood were as much as 15,000 years older than on 

associated midden material; such contamination of 

younger strata with older debris may occur more often in 

large rock shelters and caves, where fossil material may 

be readily available. Packrats apparently may incorporate

older sticks that were foraged from other parts of the 

shelter into a midden. Thus, large pieces of wood may 

be undesirable as dating material, because of their attractiveness as materials for packrat-den construction.

Some of the galleries behind and between ledges of indurated midden contain different-age organic debris. A 

tunnel-like cavity between samples ER-3(13) and 3(14) 

that extends to the back wall of the shelter (fig. 9) was 

filled with loose reddish-brown dirt and seeds. Limberpine seed shells from this fill were dated at 14,200 B.P. 

(table 6). This indicates that at least part of the midden 

was occupied during the late Wisconsin as well as during 

the middle Wisconsin.

Van Devender (1973, p. 17-18) first noted that packrat 

middens do not necessarily contain normally superimposed layers and that a packrat may deposit debris 

beneath a ledge formed by an older indurated midden. 

Based on the radiocarbon analyses of the Eleana Range-3 

midden, it seems appropriate to extend this observation 

to note that some, but by no means all, middens may be 

so reworked by packrats throughout the millenia that 

they are undesirable for detailed paleoenvironmental 

reconstruction, no matter what their age. Only three assemblages from this midden had paired dates that were 

concordant at 20 ( table 6); only these assemblages will 

be used for paleoenvironmental reconstruction. These 

samples ER-3(3), 3(7)2, and 3(8)s, may possess enough 

temporal integrity to warrant detailed discussion.

Dating results on the Eleana Range-2 midden (site 

ER-2; 10,600 to 17,100 B.P.) are more encouraging. The 

first series of dates from the midden revealed that normal superposition appears to be the rule rather than the 

exception (table 6.) However, the lowermost unit yields 

anamalously young dates (fig. 10). This stratum also is 

friable and contains more insect fragments than the 

units above. The abundant mouse and pika (Ochotona 

sp.) feces suggest reworking by burrowing animals subsequent to initial deposition. Paired radiocarbon dates of 

14,310 (on Neotoma feces) and 10,800 B.P. (on undifferentiated plant debris) (table 6) from sample ER-2( 11) indicate that a mixing of older and younger material has 

occurred.

Radiocarbon analyses of samples from the Specter 

Range-2 midden (site Spc-2; 18,700 to 32,000 B.P.) also 

indicate normal superposition of layers, with the exception again of the bottom stratum. Dates on sample Spc-2( 12) 

are considerably younger than those from overyling strata 

(fig. 11; table 6). Unlike the dates on the lowest sample 

from the Eleana Range-2 midden, paired dates from 

sample Spc-2(12) are coeval at 10, yielding no evidence 

of mixing of different-age debris. This may be because 

the Specter Range-2 midden is suspended about 1 m 

above the floor of the rock shelter, perhaps precluding
18 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 6. Packrat-midden sites, samples, and radiocarbon dates

[Artr, Artemisia sec. Tridentatae; Cele, Cercocarpus ledifolius; fp, Neotoma fecal pellets; Juos, Juniperus osteosperma; Iv, leaves; Mout, Mortonia utahensis; Pifl, Pinus 

flexilis; sd, seeds; tg, twigs: uod. undifferentiated organic debris; upd, unidentified plant debris; wd. wood; Yusc. Yucca schidigera; In, 1 standard deviation]

Site

Eleana Range (ER) 2

(lat37°07l8"N.,

long 1 16 ° 14 '03 "W.,

elevation 1,810 m).

Eleana Range (ER) 3

(lat 37°07'15"N., 

long 1 16 ° 13 '49 "W.,

elevation 1,800 m).

Eleana Range (ER) 3

(cont.)

Specter Range ( Spc ) 1

(lat36°38'31"N.,

Unit

I

I

II

II

II

III

IV

IV

IV

IV

IV

IV

IV

V

V

I

I 

I

I

II

II

III

III

III

III

IV

V

V

V

VI

VI

VI

VI

VI

VIII

IX

IX

__

Sample

No.

ER-2(1)

ER-2(2)

ER-2(3)

ER-2(4)

ER-2(4)

ER-2(5)

ER-2(6)

ER-2(6)

ER-2(7)

ER-2(7)/

2(8)

ER-2(9)

ER-2(10)

ER-2(10)

ER-2(11)

ER-2(11)

ER-3(2)

ER-3(2) 

ER-3(3)

ER-3(3)

ER-3(4)

ER-3(4)

ER-3(6)

ER-3(7)i

ER-3(7)2

ER-3(7) 2

3ER-3(p)

ER-3(8)2

ER-3(8)3

ER-3(8)3

ER-3(9)

ER-3(9)

ER-3(10)

ER-3(10)

ER-3(10)

ER-3(12)

ER-3(13)

ER-3(13)

4ER-3(u)

5ER-3(14)

Spc-l(l)

Spc- 1(2)

Radiocarbon 

date (±1(7)

10,620±120

11,700±85

13,180±65

14,090±320

15,300±130

14,260±110

14,500±110

14,830±80

14,760±100

15,380±100

15,890±120

17,100±130

17,100±90

10,800±90

14,310±110

49 800 + 3 ' 100 4y ' 8UU 2,300

42,500±1,300 

37,400±1,000

39,400±760

37,950±450

42,800±1,000

40,600±850

49,900+1,900

 1,500

44,500±1,1QO

46,100+1-200

 1,600

38,600±1,100

44,100±1,300

39,800±1,200

37,600±350

34,800±550

36,290±330

47,100 + 2,600

-2,000

32,500±800

35,450±650

45,400±1,500

22,940±150

29,120±17Q

40,500±1,000

14,200=^100

300±40

100 + 200 

 100

Laboratory

No.i

USGS-876

USGS-914

USGS-884

A-2927

USGS-875

USGS-874

USGS-885

USGS-886

USGS-887

USGS-888

USGS-889

USGS-890

USGS-1069

USGS-892

USGS-893

USGS-971

USGS-1260 

USGS-915

USGS-991

USGS-972

USGS-1261

USGS-973

USGS-916

USGS-974

USGS-975

USGS-687

USGS-917

USGS-918

USGS-976

USGS-1264

USGS-1061

USGS-919

USGS-993

USGS-1265

USGS-920

USGS-992

USGS-1062

USGS-977

USGS-1266

UW-635

UW-630

Material 

dated

Juos tg & sd

Artr tg

fp

Pifl Iv

Pifl wd

Pifl wd

Pifl Iv

fp

fp

Cele wd

fp

fp

Pifl Iv

upd

fp

uod

fp&tg 

upd

uod

fp

tg

uod

Cele wd

fp

uod

upd

Cele wd

Cele wd

fp

uod

fp

Juos wd

fp

uod

Cele wd

fp

upd

uod

Pifl sd

upd

Yusc Iv

Weighted 

average2

 

 

 

 

 

 

 

14,720±70

 

 

 

 

17,100±70

 

 

 

 

38,670±610

 

 

 

 

 

45,110=^870

 

 

 

37,800±340

 

 

 

 

 

 

 

 

 

 

__

 

long 116 ° 05'00 "W., 

elevation 1,040 m).
PACKRAT-MIDDEN ANALYSIS 19

TABLE 6. Packrat-midden sites, samples, and radiocarbon dates Continued

Site

Specter Range ( Spc ) 2

(lat36°40'l6"N.,

long 116° 12 '33 "W.,

elevation 1,190 m).

Specter Range ( Spc ) 3

(lat36°40'35"N.,

long 1 16 ° 12 '28 "W.,

elevation 1,100 m).

Point of Rocks (PR) 1

(lat36°34'l3"N.,

long 116°04'45"W.,

elevation 900 m).

Point of Rocks (PR) 2

(lat36°33'48"N.,

long 116°04'55"W.,

elevation 930 m).

Point of Rocks (PR) 3

(lat36°34'lO"N.,

longll6°05'10"W.,

elevation 910 m).

Owl Canyon (OC) 1<5

(lat36°24'N.,

long 116° 14' W.,

elevation ca. 790 m).

Owl Canyon (OC) 2

(lat36°24'27"N.,

long 116° 14 '23 "W.,

elevation 800 m).

Owl Canyon (OC) 3

(lat36°24'18"N.,

long 116° 14 '29 "W.,

elevation 790 m).

Last Chance Range ( LCR) 1

(lat36°17'25"N.,

long 116°07'40"W.,

elevation 960 m).

Unit

I

I

I

I

II

II

II

III

III

III

III

III

IV

IV

Sample 

No.

Spc-2(2)i

Spc-2(2h

Spc-2(2)2

Spc-2(2)2

Spc-2(3)

Spc-2(3)

Spc-2(6)

Spc-2(8)

Spc-2(8)

Spc-2(10)

Spc-^dlh

Spc-2(ll)2

Spc-2(12)

Spc-2(12)

Spc-3 A( 1 )

Spc-3A(2)

Spc-3 A( 2)

Spc-3B

PR-Kl )

PR-K1 )

PR-K3)

PR-2(2)

PR-2(3)

PR-3

OC-1

OC-2(1)

OC-2(2)

OC-3(1)

OC-3(2)

LCR-K2)

LCR-l(S)

Radiocarbon 

date (±!CT)

18,760±110

18,710±150

2l,400±1200

19,080±370

23,330±150

23,250±100

25,900±260

27,900±300

29,810±280

29,140±310

32,260±2,800

32, 100± 1,400

25,280±220

25,060±190

20,200±1,800

10,660±250

13,090±320

28,460±2,200

9,880±190

9,780±230

11,680±650

9,560±220

9,260±180

14,810±400

13,150±500

10,260±520

10,070±220

32,870±1,370

>28,700

9,280±210

11,760±90

Laboratory 

No.'

USGS-1063

USGS-994

UW-637

UW-638

USGS-998

USGS-1064

USGS-995

USGS-997

USGS-1065

USGS-1066

UW-639

UW-640

USGS-996

USGS-1067

A-2398

A-2399

A-2400

A-2401

A-2395

A-2396

A-2397

A-2393

A-2394

A-2927

1-4237

A-2402

A-2403

A-2412

A-2413

A-2414

A-2415

Material 

dated

uod

Juos tg & sd

Pimo Iv

Juos tg & sd

Juos tg

uod

Juos tg & uod

Juos tg & sd

uod

uod

Juos tg & sd

Juos tg & sd

Juos tg

uod

Juos tg & sd

fp

Juos tg

Juos tg

fp

upd

upd

upd

upd

tg

Juos tg

fpfp

Juos tg & sd

Juos tg & sd

Mout Iv

Juos tg & sd

Weighted 

average2

 

18,740±90

 

19,280±350

 

23,270±80

 

 

 

 

 

 

 

25,150±140

 

 

 

 

 

9,840±150

 

 

 

 

 

 

 

 

 

 

 

iUSGS, U.S. Geological Survey Radiocarbon Laboratory; A, University of Arizona, Laboratory of Isotope Geochemistry; UW, University of Washington, Department of 

Chemistry Radiocarbon Laboratory; I, Teledyne Isotopes.

2Average of paired dates from one sample, weighted toward the radiocarbon date with the smaller a (the more precise date) (Long and Rippeteau, 1974, p. 208). 

3Prospect sample removed prior to detailed stratigraphic analysis. 

4Sample from loose float on floor of shelter. 

5Loose fill in cavity between two indurated midden units. 

6Midden located and collected by P.J. Mehringer, Jr. (Mehringer and Warren, 1976). The site could not be relocated.
20 

WEST

VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

EAST

Unit

Unit

Column 2 RADIOCARBON YEARS 

BEFORE PRESENT

Unit

VI

VII 

VIII

IX

III 

Columns RADIOCARBON YEARS 

BEFORE PRESENT

m^mmm^<^mMy& iv^

n' i'j \ i u i i> M M

ER 3(9) ^

- --^

ER3(10)^^fT

^£^&-

^TfW'^pi^

 - _____ CD O/1 O\

ER3(13) ^-

ER3(14)

_______ 

^34,800±550 

 36,290±330 

^ 32,500±800 

 35,450±650 v 

^47,100-2000

TTIU SM I

CD O/C\

ER 3(7),

TTTTTTTTTT

ER 3(7)2 -=

' ^ \ ERSiS),'^

ER 3(8)2 -

ER 3(8)3 -=

4qqno+190°

^^44,500±1100

 . A.R 1 nr> +2000 ^ 4b,lCXJ_1000

^38,600±1100 _

 "

44,100±1300

^ 37,600±350 

~ 39,800±1 200

 45,400±1 500

^- 22,940±1 50 EX 

~ 29,1 20±1 70 CENTIMETERS ^..... ............)

 14,200±100 10- 

BT

0 5 10 

CENTIMETERS

DEGRADED M 

DEBRIS-FILLEC

Column 1 RADIOCARBON YEARS 

BEFORE PRESENT

ER 3(2)

ER 3(3)

42,500±1300 

49,800-2300

37,400±1000 

39,400±760

37,950±450 

42,800±1000

EXPLANATION

RIND

FIGURE 9. Sample columns from the Eleana Range-3 packrat midden (dashed lines indicate inferred correlations).

the bioturbation that occurs in the lower parts of middens that rest on rock-shelter floors.

THE FOSSIL RECORD IN SELECTED AREAS

Fossil packrat-midden sites in south-central Nevada 

can be placed into two categories. The first are those 

sites that lie within the floristic Mojave Desert, with 

middens that record vegetation on dolomite, limestone, 

or derived calcareous f anglomerates. In the vicinity of the 

Nevada Test Site, these range from elevations as low as 

790 m in the Amargosa Desert, to 1,830 m in the Spotted 

Range (figs. 1, 2). The second category are midden sites 

from the Eleana Range in the floristic Great Basin Desert (figs. 1,4). These rock shelters, developed in volcanic 

tuffs, lie at an elevation of about 1,800 m. Detailed lists 

of fossils from these sites are given in the Supplemental 

Data section, tables 16-25.

PERIPHERY OF AMARGOSA DESERT

The lowest midden sites in the region are on the eastern edge of the Amargosa Desert, at elevations ranging 

from 790 to 960 m (fig. 1). These are also the only sites

that provide records of glacial-age desert vegetation. 

Macrofossil assemblages from the Owl Canyon locality 

(fig. 7) date to the middle and latest Wisconsin (table 6). 

Present vegetation is sparse Mojave desertscrub on xeric 

dolomitic substrate. The most common plants on the 

rock slopes include matchweed (Gutierrezia microcephala), 

desert spruce (Peucephyllum schottii), white bursage 

(Ambrosia dumosa), and creosote bush (Larrea divaricata). 

The site of the Owl Canyon-1 midden, collected and 

dated by P. J. Mehringer, Jr., could not be relocated. It is 

near the mouth of the same canyon where the Owl Canyon-2 

site is located (fig. 7; P. J. Mehringer, Jr., Washington 

State University, oral commun., 1980). Radiocarbon dated at 13,150±500 B.P. [laboratory number 1-4237 (table 

6)] (Mehringer and Warren, 1976, p. 125), this midden 

contains abundant Utah juniper (Juniperus osteosperma) 

and Utah agave (Agave utahensis), indicating an open 

woodland at Owl Canyon-1 near the end of the Wisconsin (Spaulding, 1981, p. 152).

The two other sites, Owl Canyon-2 and 3, are on xeric 

south-facing slopes (fig. 7), and are of different age. 

Macrofossil assemblages from Owl Canyon-3, at an elevation of 790 m, contain abundant rubber rabbitbrush
PACKRAT-MIDDEN ANALYSIS 21

WEST 

Unit

IV

EAST

RADIOCARBON YEARS 

BEFORE PRESENT

ER2(1)

ER 2(2)

ER 2(4)

ER2(7)

ER2(8)

10,620±120

14,090±320

14,260±110 

14,500±110 

14,830±80 

14,760±100

15,380±100

15,890±120 

17,100±90

17,100±130 

10,800±90

14,310±110

CENTIMETERS 20 |

10 

EXPLANATION

DEGRADED MIDDEN BEDROCK

0 10 20 

CENTIMETERS

DEBRIS-FILLED VOID WEATHERING 

RIND

FIGURE 10. Sample column from the Eleana Range-2 packrat midden.

( Chrysothamnus nauseosus) and Utah juniper, and common Utah agave, and they date to the middle Wisconsin 

(about 33,000 B.P. and >29,000 B.P.) (table 6). Both 

rubber rabbitbrush and Utah agave are characteristic of 

higher elevation deserts. Agave is not known below elevations of about 1,200 m (Beatley, 1976, p. 269). The 

abundance of shrubs and succulents in the Owl Canyon-3 

assemblages may indicate desertscrub vegetation with 

occasional junipers, rather than a juniper woodland.

Two samples from the Owl Canyon-2 midden are radiocarbon-dated at 10,070 and 10,260 B.P. (table 6). They 

contain abundant Utah agave, but lack appreciable quanEAST

RADIOCARBON YEARS 

BEFORE PRESENT

Unit

19,080±370 

21,400±1200

25,900±260

27,900±300 

29,810±280

29,140±310

IV

WEST

RADIOCARBON YEARS 

BEFORE PRESENT

Unit

18,710±150 

18,760±150

23,250±100 

23,330±150

32,260±2800 

32,100±1400

25,060±190 

25,280±220

CENTIMETERS 

15-

10- 

5- 

0

EXPLANATION

DEGRADED MIDDEN

0 5 10 15 

CENTIMETERS

WEATHERING 

RIND

DEBRIS-FILLED VOID

FIGURE 11. Sample column from the Specter Range-2 packrat midden.

tities of rabbitbrush and contain no juniper (see Supplemental Data section). Desertscrub vegetation apparently 

was well-developed at this site by the close of the Wisconsin. 

However, none of the xerophytic species that characterize the present local vegetation are recorded. Instead, 

the terminal-Wisconsin plant community appears to have 

been dominated by shrubs and succulents that commonly occur at higher elevations (above 1,200 m) today.

Late Wisconsin and early Holocene desert vegetation 

also is documented by packrat middens at the Point of 

Rocks locality. At an elevation of 910 m, the Point of 

Rocks-3 site is about 5 m above a talus slope head on the 

southwest-facing flank of a ridge (fig. 6). A sparse desertscrub 

community dominated by white bursage (Ambrosia 

dumosa), creosote bush, and chaff-bush (Amphipappus 

fremontii) occurs at the site today. The Point of Rocks-3 

midden is dated at 14,810±400 B.P. (table 6) and contains abundant snowberry (Symphoricarpos longiflorus), 

an extralocal shrub, and common shadscale (Atriplex 

confertifolia)(see Supplemental Data section). It lacks
22 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

the remains of juniper and, as such, it is the oldest 

reported macrofossil record of desertscrub vegetation 

from the American southwest.

The Point of Rocks-1 site, at an elevation of 900 m, is 

about 30 m from the floor of the large wash issuing 

into the Amargosa Desert from Point of Rocks Pass 

(fig. 6). A radiocarbon date of 11,680 B.P. on sample 

PR-1(3) (table 6) is associated with a macrofossil assemblage containing abundant cactus spines (Opuntia sp.) 

and the common twigs and flowers of scalebroom 

(Lepidospartum latisquamum)and matchweed. Like the 

Owl Canyon-2 and Point of Rocks-3 assemblages, sample PR-1( 3) contains no arboreal species and is one of the 

first reported records of glacial-age desertscrub. Today, 

scalebroom is restricted to washes at elevations above

I,525 m (Beatley, 1976, p. 143). Its presence in this 

assemblage may indicate that some plant species in 

sample PR-1(3) were collected in the wash about 20 m 

away. Alternatively, conditions might have been such 

that this riparian species occurred on rocky slopes that 

are now too xeric to support it. Such a phenomenon has 

been noted in the midden record from the Sonoran Desert 

where some perennials, presently restricted to washes, 

occurred on hillsides during the late Wisconsin (Van 

Devender, 1973, p. 59.). The younger PR-l(l) sample, 

dated at 9,840 B.P. (table 6), is dominated by desert 

bitterbush (Purshia glandulosa), another extralocal species. 

Like the Owl Canyon-2 and 3 assemblages, those from 

Point of Rocks-1 document mesophytic desertscrub 

vegetation, dominated by species no longer near the site; 

with the exception of Owl Canyon-3, they contain no tree 

species.

Point of Rocks-2 site, at an elevation of 930 m, overlooks the alluvial fan that slopes westward to the Amargosa 

Desert, not far southwest of the Point of Rocks-1 site 

(fig. 6). At 9,260 and 9,560 B.P. the two desertscrub 

assemblages from Point of Rocks-2 are the youngest 

from the Amargosa Desert (table 6). Not coincidentally 

they contain more of the plant species that presently 

occur at the site, such as creosote bush and chaff-bush, 

than do the older midden samples from Point of Rocks-1 

or Owl Canyon.

The highest elevation midden site on the periphery of 

the Amargosa Desert is in the western Last Chance 

Range at an elevation of 960 m (figs. 2,8). The LCR-1(3) 

assemblage is dated at 11,760 B.P. (table 6), less than 

100 radiocarbon years older than the PR-1( 3) assemblage. 

Nevertheless, in contrast to sample PR-1(3), LCR 1(3) 

contains abundant juniper, indicating that between

II,600 and 11,800 B.P., the lower limit of woodland in 

this area was not far above an elevation of 900 m. The 

LCR-1( 2) assemblage at 9,280 B.P., is of comparable age 

to the PR-2 samples (table 6). Like the Point of Rocks-2 

assemblages, LCR-1( 2) contains many of the plants that

grow at the site today, although three of the four most 

abundant taxa are extralocal. Juniper was still present 

at this site at about 9,300 B.P., while it apparently was 

absent from the Point of Rocks and Owl Canyon localities well before this time.

SPECTER RANGE

Packrat middens from the northern Specter Range 

yield a different chronology of vegetation change. Macrofossil assemblages from the Specter Range-2 site, on the 

north side of a ridge at an elevation of 1,190 m (fig. 6), 

span more than 13,000 years, from about 32,000 to 18,700 

B.P. (table 6). Mojave Desert vegetation at the site 

today contrasts with midden samples that indicate a 

middle Wisconsin juniper or juniper-shadscale woodland, 

and a pinyon pine (Pinus monophylla)-juniper woodland 

during the Wisconsin maximum.

The Specter Range-3 site, downslope and north of 

Specter Range-2 site, is less than 50 m from the head of 

an alluvial fan that extends into Rock Valley (fig. 8). The 

ages of sample Spc-3A(l) at 20,200 B.P. and sample 

Spc-3B at 28,500 B.P. are approximately contemporaneous with some of the Specter Range-2 samples (table 6). 

Like the Spc-2 record, these Spc-3 assemblages document a juniper woodland lacking pinyon pine, but contain greater proportions of shrubs, such as winterfat 

(Ceratoides lanata), sagebrush, and shadscale.

Preliminary onsite inspection of the Specter Range-1 

midden, from the cliff bordering a large wash on the 

western edge of Mercury Valley (fig. 8), indicated it was 

younger than 3,000 B.P. However it was collected and 

analyzed because a marked dichotomy was noted between 

plant fragments visible in the midden and the surrounding vegetation. The top layer has a radiocarbon date 

of 300±40 B.P., whereas the bottom unit is subrecent

(100^?QQ (table 6). The older sample is dominated by 

fourwing saltbush (Atriplex canescens), whereas the 

younger sample contains abundant creosote bush.

ELEANA RANGE

The Eleana Range is a southerly extension of the 

Belted Range and Pahute Mesa (fig. 2). Two adjacent 

sites on south-facing slopes, Eleana Range-2 and -3 (fig. 

4), contain large indurated middens. Today, these sites 

are at the boundary between Great Basin desertscrub, 

occupying the talus slopes and valleys, and pinyon pinejuniper woodland, occurring on the mesa tops and northfacing slopes. The Eleana Range-2 midden records past 

vegetation from Wisconsin maximum to latest Wisconsin time. Samples from Units II through IV, from 13,200 

to 17,100 B.P. (fig.10), provide evidence for a limber-pine 

(Pinus flexilis) woodland with Great Basin Desert and
THE FOSSIL RECORD IN SELECTED AREAS 23

woodland shrubs as important understory species. The 

youngest samples are from Unit I. Dated at 11,700 and 

10,600 B.P. (table 6), they indicate a shift to a woodland 

dominated by jumper, pinyon pine, and pricklypear 

(Opuntia erinacea) species present in the modern woodland nearby.

As mentioned previously, radiocarbon analyses indicate that many assemblages from the complex Eleana 

Range-3 midden may be contaminated. Three samples 

that have statistically similar paired radiocarbon dates, 

and thus may contain valid species associations are: (1) 

Sample ER-3(8)s at 37,800 B.P.; (2) sample ER-3(3) at 

38,700 B.P.; and (3) sample ER-3(7)2at45,100 B.P. [ages 

expressed are weighted averages of two 14C dates on each 

sample (Long and Rippeteau, 1974)](table 6). These assemblages reflect an open jumper woodland that differed 

from both late Wisconsin plant communities recorded by 

the Eleana Range-2 midden and the present vegetation. 

Extralocals, such as curl-leaf mountain mahogany 

( Cercocarpus ledifolius), were present, and species important in the current woodland nearby were absent, such as 

Gambel oak (Quercus gambelli) and pinyon pine.

EARLY RECORDS FROM THE NEVADA TEST SITE

Wells and Jorgensen (1964) were the first to report on 

the significance of ancient packrat middens. Their initial 

studies were conducted in the vicinity of the Nevada Test 

Site (fig. 2) where some indurated packrat middens were 

found to contain abundant juniper. The presence of this 

tree fossil at sites supporting only desert vegetation 

today led Wells' colleagues to suspect that the middens 

were of considerable antiquity (Wells, 1976, p. 224). Of 

this early series, the lowest elevation sites are from the 

Ranger Mountains and lie between elevations of 1,100 

and 1,130 m (fig. 2). The Ranger Mountains-1 midden, 

dated at 16,800±300 B.P., contains a depauperate macrofossil assemblage,while samples from the Ranger Mountains-2 midden, dated variously from 10,100±160 to 

28,900±1,200 B.P., contain abundant shadscale and 

common pricklypear (Wells and Berger, 1967, table 1). 

Mercury Ridge-3 (at 1,250 m) is the only other midden 

of Wisconsin age, dated at 12,700±200 B.P. The remaining middens from Mercury Ridge, as well as those 

from Aysees Peak and the Spotted Range, are all of early 

Holocene age. All contain juniper, and the Spotted 

Range-2 midden also contains common pinyon pine 

(Pinus monophylla), although there is a discrepancy 

in the radiocarbon dates for this midden (reported as 

>40,000 and 9,550±90 B.P.) (Wells and Jorgensen, 1964, 

table 1; Wells and Berger, 1967, table 1). These middens 

document the persistence of juniper at high desert sites 

for more than 3,000 years after its extirpation from lower 

altitude sites in the Amargosa Desert (Spaulding, 1983).

SHEEP RANGE AND EUREKA VALLEY

Only four mountain ranges in the Mojave Desert have 

considerable relief above 2,200 m, the approximate lower 

limit of montane vegetation in this region. From west to 

east, these ranges are the Inyo Mountains and Panamint 

Range of California and the Spring and Sheep Ranges of 

Nevada (fig. 1). Late Quaternary vegetation of the Sheep 

Range, 60 km east-southeast of the Nevada Test Site, 

has been the subject of a recent packrat-midden study 

(Spaulding, 1981). This record consists of 52 macrofossil 

assemblages from 30 sites that span 900 m of topographic relief. Sheep Range midden sites extend the fossil 

record from limestone and dolomite substrates to 2,400 

m. Such rocks generally are lacking above an elevation of 

1,600 m in the Nevada Test Site. Current vegetation of 

the Sheep Range is like that of the Nevada Test Site, 

given similar topography and parent rocks; the packratmidden record is also similar. Below approximately 1,800-m 

elevation, Wisconsin age packrat middens from the southeastern Sheep Range (fig. 12) and the western Sheep 

Range (fig. 13) yield records of juniper-shrub vegetation 

analogous to records from sites such as Specter Range-2. 

Late Wisconsin middens from above 1,800-m elevation 

in the Sheep Range yield assemblages dominated by 

subalpine conifers (Pinus flexilis and Pinus longaeva) 

(Spaulding, 1981, fig. 27).

Midden data from the Sheep Range are synthesized in 

the regional fossil record of the northern Mojave Desert 

(fig. 14) with middens from the Nevada Test Site and 

vicinity. Two isolated records from the Blue Diamond 

area in the southern Spring Range (Spaulding, 1981, p. 

153-157) and middens from the Eureka Valley in California, 

140 km west-northwest of the Nevada Test Site (fig. 1) 

(Spaulding, 1980), also are included in figure 14. Packrat 

middens from the Eureka Valley are the only comprehensive Holocene time series from the northern Mojave 

Desert (see Supplemental Data section, table 25) and 

supplement the midden record from the periphery of the 

Amargosa Desert. Middens from the Amargosa Desert 

document the presence of late Wisconsin and early Holocene desert vegetation that differed from current desertscrub. Eureka Valley middens show transformation of 

this anomalous desertscrub to an essentially modernvegetation type.

TULE SPRINGS

Pollen-stratigraphic and geologic investigations at Tule 

Springs, in the Las Vegas Valley about 80 km southeast 

of the Nevada Test Site (fig. 1), provided some of the first 

detailed information on the late Quaternery environments 

of the Mojave Desert (Martin and Mehringer, 1965; 

Mehringer, 1967; Haynes, 1967). Although some conclusions reached during this earlier work require revision
24

36°30'

VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

16' 15'

< f .

SOUTH CREST-1\

36°27' -

1MILE

0 1 KILOMETER 

CONTOUR INTERVAL 400 FEET 

DATUM IS SEA LEVEL

EXPLANATION

 PACKRAT-MIDDEN SITE

FIGURE 12. Location of packrat-midden sites in the southeastern Sheep Range.

(Spaulding and others, 1983), palynological evidence for 

the expansion of woodland and Great Basin Desert plants 

during the Wisconsin corroborates evidence provided by 

packrat middens from nearby mountains. Important paleoecological inferences from Tule Springs came from pollen 

spectra of spring mound sediments of latest Wisconsin 

age. Relatively high frequencies of Juraperas and Artemisia 

pollen, coupled with juniper wood in the sediments, indicates an open juniper woodland with Great Basis Desert

species on the floor of the Las Vegas Valley (Mehringer, 

1967, p. 184-185).

GRAND CANYON

Wisconsin-age environments of the Grand Canyon have 

been the subject of several investigations. Packrat middens from the lower Grand Canyon of Arizona, 215 km 

east-southeast of the Nevada Test Site (fig. 1), provide
THE FOSSIL RECORD IN SELECTED AREAS

18' 17'

25

36°3B' 

WAGON CANYON-2 J ( (

\ I v

Base from U.S Geological Survey 

Black Hills and Whita Sage Flat 

Th minute quadrangles

1 KILOMETER

CONTOUR INTERVAL 400 FEET

SUPPLEMENTARY CONTOURS AT 200 FEET (DASHED)

DATUM IS SEA LEVEL

EXPLANATION

PACKRAT-MIDDEN SITE

FIGURE 13. Location of packrat-midden sites in the western Sheep Range.
26 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

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Spc-2(11) Spc-2(3) , 2 M'V */ M-2

^»~«*« ~®-® 1 / Desertscrub 

-^ . / ,R'2

^\ s/ \ ' / Spc-1 

/X LCR-1(3) LCR-1(2) 

^/PR-3 * {

oc-3(i)^ X OC:1^ X PRji

OC-2

1 1 1 1 1 A 1 1 1 1 1 I 1 1 1 1 1 1 1 1 1 1 I 1 1 ! 1 0 45 40 35 30 25 212019181716151413121110 9 8 7 6 5 4 3 2 1 

RADIOCARBON AGE, IN THOUSANDS OF YEARS BEFORE PRESENT

Fir- Pine ~ 

Forest

< 

Pygmy 

Conifer 

Woodland

_

-

Desertscrub

:

No Scale

CURRENT 

VEGETATION

EXPLANATION

INFERRED POSITION OF MAJOR VEGETATION 

ZONE BOUNDARIES

SAMPLES FROM VOLCANIC SUBSTRATE (THE

ELEANA RANGE LOCALITY) 

SAMPLES DOMINATED BY SUBALPINE CONIFERS

SAMPLES CONTAINING MONTANE CONIFERS 

SAMPLES CONTAINING ABUNDANT UTAH JUNIPER

ASSEMBLAGES WITH BOTH ABUNDANT JUNIPER 

AND PINYON PINE

SAMPLES WITH ABUNDANT JUNIPER AND COMMON LIMBER PINE

ANOMALOUS DESERTSCRUB ASSEMBLAGES

DESERTSCRUB VEGETATION ANALOGOUS TO

THAT AT THE SITE TODAY 

± 1(7 OF THAT SAMPLE'S RADIOCARBON DATE

Abbreviations for the fossil localities from the vicinity of the Nevada Test Site and Amargosa Desert 

are: A, Aysees Peak; ER, Eleana Range; F, Funeral 

Mountains; LCR, Last Chance Range; M, Mercury Ridge; OC, Owl Canyon; PR, Point of Rocks; 

R, Ranger Mountains; S, Spotted Range; Spc, 

Specter Range (fig. 1). Abbreviations for sites 

from the Sheep Range are: BC, Basin Canyon; 

BH, Black Hills; BW, Basin Wash; CT, Canyon 

Two; Dm, Deadman; DV, Desert View; Ey, Eyrie; 

Fm, Flaherty Mesa; HF, Hidden Forest Ph, Penthouse; SC, South Crest Sm, Sawmill Canyon; 

Sp, Spires; WC, Wagon Canyon; WW, Willow 

Wash (figs. 12, 13). The BDR (Blue Diamond 

Road) sites lie in the southeastern Spring Range, 

and the HTH (Horse Thief Hills) and EV(Eureka 

View) sites are in the northern Eureka Valley (fig. 

1). Data are from this report. Wells and Berger 

(1967), and Spaulding (1980, 1981)

FIGURE 14. Age and elevational distribution of late Quaternary packrat-midden samples from the northern Mojave Desert. Dashed lines indicate the 

approximate elevation of major vegetation zone boundaries on xeric slopes. Note changes in scale. The column to the right presents the current 

vegetation zonation.

an elaborate record from limestone slopes between elevations of 440 and 675 m (Phillips, 1977). Although current 

vegetation at most sites is desertscrub, late Wisconsin 

macrofossil assemblages document a juniper woodland 

with a diverse complement of desert species (such as 

Atriplex confertifolia, Agave utahensis, Ephedra sp., 

Echinocactus polycephalus) and some woodland associates (such as Symphoricarpos sp., Opuntia whipplei)( Phillips, 

1977; Mead and Phillips, 1981). Many species common 

in the late Wisconsin woodland of the lower Grand Canyon, 

such as blackbrush ( Coleogyne ramosissima), single-leaf 

ash (Fraxinus anomcda), and brittlebrush (Encelia farinosa), 

are rare or missing in similar-age middens from the 

Nevada Tbst Site and Sheep Range, partly because of the
LATE QUATERNARY VEGETATION AND CLIMATE 27

higher elevations of these Nevada sites. It also is probable that the precipitation regime of the Grand Canyon 

region was different from areas to the west and north. 

Assemblages in late Wisconsin packrat middens from 

farther east in the central Grand Canyon (Cole, 1981) are 

even more different from the Nevada fossil record, although 

these records are from the same altitudinal range.

The timing of latest Wisconsin vegetation change in 

the Lower Grand Canyon was distinctly different from 

that recorded by packrat middens from the Nevada 

Test Site and vicinity. Grand Canyon sites as low as 

560-m elevation supported juniper woodland well into 

the Holocene (until about 8,500 B.P.) (Phillips, 1977, p. 

85; Van Devender, 1977b; Cole 1982). In contrast, middens from the Amargosa Desert as high as 930-m elevation show that woodland gave way to desert vegetation 

by at least 14,800 B.P. at some localities (fig. 14)(Spaulding, 

1983).

LATE QUATERNARY VEGETATION 

AND CLIMATE

The Wisconsin macrofossil record from the northern 

Mojave Desert spans 1,600 m of topographic relief, from 

Owl Canyon in the Amargosa Desert (800 m) to the 

Hidden Forest (2,400 m) in the Sheep Range (Spaulding, 

1981, p. 144). The record provides a data base sufficient 

for estimates of paleoclimate that can be compared with 

estimates from other regions. Major environmental changes, 

such as that which occurred at the end of the Wisconsin, 

are evident in the composite packrat-midden record (fig. 14), 

but lower magnitude fluctuations can be better studied 

in time series from single midden sites. Plant community 

change usually takes place in the context of a single 

vegetation type; variations occurred in the composition 

of woodland during the Wisconsin, and changes occurred 

in desertscrub vegetation during the Holocene. Time 

series macrofossil assemblages at different sites, coupled with the use of relative frequencies of macrofossils, 

help discern these more subtle changes.

The Climate: Long-Range Investigation Mapping and 

Prediction (CLIMAP) project members' (1976, fig. 1) 

reconstruction of full glacial (18,000 B.P.) surface conditions 

of North America shows the Southwest as a region of 

sparse vegetation with a high surface albedo. However, 

woodland was widespread in this region, with a resultant 

albedo that was lower than today's. The cause of this 

discrepancy is the assumption that lowered temperatures 

during the late Wisconsin led to reduced competency of 

the atmosphere and, therefore, to less precipitation and 

sparse vegetation. However, this was not the case. Lowered 

temperatures and increased winter precipitation during 

the full glacial led to decreased evapotranspiration, greater

effective moisture, and increased vegetation cover in the 

arid West. The initial paleobotanical evidence for this 

difference (Martin and Mehringer, 1965; Mehringer, 1967; 

Wells and Berger, 1967) was not well depicted by CLIMAP 

(1976).

MIDDLE WISCONSIN ENVIRONMENTS

The middle Wisconsin has been correlated with oxygenisotope stage 3 in the deep-sea core record (Dreimanis 

and Raukas, 1975, p. 109-110 and 116), with bracketing 

dates of about 62,000 and 23,000 B.P. (Prell and Hayes, 

1976, fig. 3; Ruddiman and Mclntyre, 1981, fig. 2). Variations 

in the oxygen 16/oxygen 18 ( 160/180) ratios in the tests of 

benthic foraminifera in deep-sea cores provide an index 

of global ice volume (Shackleton and Opdyke, 1973) and 

indicate that interstadial conditions prevailed during 

this period. This was a time of generally lower continental 

ice sheet volume and warmer global temperatures, between 

the early and late Wisconsin stades [isotope stage 4 for 

the early Wisconsin and stage 2 for the late Wisconsin 

(Dreimanis and Raukas, 1975)].

Packrat-midden samples cannot be placed in a welldefined stratigraphic framework; each must be associated 

with a radiocarbon age. Because the practical upper limit 

of most radiocarbon-dating laboratories is about 30,000 

B.P., only the last 7,000 years of the middle Wisconsin lie 

within the dating range of most studies. The relatively 

large number of finite dates from Nevada Test Site that 

range from 30,000 to 45,000 B.P. are the result of radiocarbon 

assays performed at the high-precision facility of the 

U.S. Geological Survey at Menlo Park, California (Robinson, 

1979).

45,000 TO 35,000 YEARS BEFORE PRESENT

Four finite-age macrofossil assemblages from the northern 

Mojave Desert are older than 35,000 B.P. (fig. 14). The 

three from the Eleana Range-3 midden provide the oldest 

time series from a single site in the Southwest. The 

ER-3( 7 >2 assemblage is associated with two radiocarbon 

dates with a weighted average of 45,000±900 B.P. (Long 

and Rippeteau, 1974) (table 6). It indicates vegetation 

broadly similar to today's: An open woodland of Utah 

juniper and mountain mahogany ( Cerocarpus ledifolius), 

with well-developed stands of sagebrush (figs. 15, 16). 

Limber pine, the dominant tree during the succeeding 

full glacial, is absent from the ER-3(7)2 sample, as are 

many of the plants present today (such as Pinus monophyUa, 

Quercusgambelii, Rhus trilobata, andAtriplex canescens).

Based on the ER-3(7>2 macrofossil assemblage, 

precipitation at about 45,000 B.P. is inferred to have 

been no higher than the present values of roughly 185 to 

205 rnm/yr1 (table 5). Affinity of the fossil flora to present 

northern steppe and dry woodland suggests that a smaller
28 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

FIGURE 15. -Eleana Range fossil locality: A. Physiography of the Eleana Range-l and 2 sites: B. Modern vegetation at the 

Eleana Range-l and 2 sites. Sketches by Frederick Paillet, U.S. Geological Survey, 1981. (See fig. 4 for location of sites.)
LATE QUATERNARY VEGETATION AND CLIMATE 29

FIGURE lh. Reconstructions of the Wisconsin vegetation of the Eleana Range: A. Full-glacial (Wisconsin maximum) 

limber-pine woodland; B. juniper-steppe shrub vegetation during the middle Wisconsin (about 45,000 years 

ago). Sketches bv Frederick Paillet, U.S. Geological Survey, 1981.
30 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

proportion of precipitation fell during the summer (less 

than 10 percent as opposed to the present value of about 

25 percent). Absence of thermophilous species, such as 

saltbushes (Atriplex spp.), hopsage (Grayia spinosa), 

and appreciable quantities of pricklypear ( Opuntia spp.), 

from the ER-3(7)2 sample implies an average annual 

temperature 1° to 3°C lower than at present (table 5).

Only one other macrofossil assemblage from this region 

is broadly correlative with the ER-3(7>2 sample: Willow 

Wash-IB from the southeastern Sheep Range (figs. 12, 

14) (Spaulding, 1981, p. 86). Dated at 43,700±2,300 B.P. 

(USGS-548), this sample provides evidence for juniper 

woodland at a site that presently supports desertscrub 

vegetation, well below the lower limit of woodland (an 

elevation of 1,585 m). It is intriguing to note that, while 

the ER-3(7)2 macrof ossil assemblage bears a general 

resemblance to current dry woodland and steppe vegetation near the site (figs. 15,16), the Willow Wash-IB 

juniper asemblage provides a greater contrast with present vegetation there. However, indices of similarity 

between these two samples and current vegetation at 

their respective sites are comparable, with a value of 40 

for the ER-3(7)2 sample and 36 for the Willow Wash-IB 

sample (Spaulding, 1981, table 39). This indicates that 

the apparent stronger contrast between the Willow 

Wash-IB fossils and current flora is primarily because 

a single species, Utah juniper, no longer occurs there. 

Species common in more mesic phases of today's woodland are missing from the Willow Wash-IB sample, 

as they are from the ER-3(7>2 sample. The presence 

of several desert shrubs and succulents (such as Opuntia 

whipplei and Hecastocleis shockleyi) in the middle Wisconsin 

woodland at Willow Wash suggests that winter minimum 

temperatures were within 2° to 3°C of today's values.

Two younger assemblages from the Eleana Range-3 

midden, ER-3(3) and ER-3(8)s, have radiocarbon dates 

that overlap at \o (table 6). Macrofossils from these two 

assemblages suggest increased effective moisture and 

higher temperatures about 6,300 years after the deposition 

of ER-3(7)2. Artemisia sec. Tridentatae frequencies are 

lower in both ER-3(3) and ER-3(8)s; this decline is 

accompanied first by an increase in Junipems osteosperma 

in ER-3(3) (dated at about 38,700 B.R), and then Pinus 

flexilis and Cercocarpus ledifolius in ER-3(8)s (dated at 

about 37,800 B.P.) (table 6; fig. 17). The macrofossils 

of Grayia spinosa are a notable occurrence in ER-3(3). 

Normally restricted to desert communities, its presence 

here indicates that maximum mid-Wisconsin temperatures, within 1° to 2°C of present annual values, may 

have occurred around 38,700 B.P. The associated increase 

in juniper and decline in sagebrush frequencies (fig. 17) 

implies an increase in precipitation, perhaps 10 to 20 

percent above today's values (table 5). This increase may

have resulted in part from warmer summers and enhanced 

warm-season rainfall.

Macrofossils from the youngest sample in this interstadial 

sequence, the ER-3(8)s sample, at about 37,800 B.P., 

indicate highest effective moisture. Junipems osteosperma 

is in part replaced by Pinus flexilis and Cercocarpus 

ledifolius ( fig. 17). The importance of these dry woodland 

and subalpine species, coupled with the continued absence 

of plants of relatively mild-moist habitats (such as Pinus 

monophylla, Pinus ponderosa, Quercus gambelii), indicate 

the increase in effective moisture resulted from a temperature 

decline. Similar plant associations presently occur on 

south-facing slopes at about 2,800 m in the Toquima 

Range, 180 km to the north-northwest. The difference in 

elevation between analogous Toquima Range sites and 

Eleana Range-3 (about 1,000 m) indicates a decline of 

5°C in mean annual temperature relative to present 

values, assuming an annual temperature lapse rate of 

-0.5°C/100m (Major, 1977, p. 65 and 68). Average annual 

precipitation 10 to 20 percent greater than present values 

(table 5) also is consistent with the fossil record from the 

ER-3( 8)3 sample.

35,000 TO 23,000 YEARS BEFORE PRESENT

Thirteen macrofossil assemblages from the northern 

Mojave Desert date to the latest part of the middle Wisconsin. 

Specter Range-2 site at an elevation of 1,190 m provides 

the only detailed chronosequence from this period. The 

oldest assemblages are rather poorly dated at about 

32,000 B.P. (Spc-2(ll)i and 2(11)2) (table 6). In contrast 

to current Mojave desertscrub vegetation at the site, 

these samples contain abundant Utah juniper, as well as 

abundant-to-common shadscale (Atriplex confertifolia) 

and rock spirea (Petrophytum caespitosum). Five younger 

samples, ranging in age from 29,100 to 23,300 B.P., also 

contain abundant Utah juniper (fig. 18).

Rock spirea is a mesophytic petrophyte (rock-loving 

plant) now extinct in the Specter Range. Scopulophila 

rixfordii, on the other hand, is a thermophilous petrophyte 

still present nearby. It is not surprising that variations 

in relative frequency of these taxa in the Specter Range-2 

assemblages are inversely related (fig. 18). These fluctuations may represent short term changes in effective 

moisture, with high frequencies of Scopulophila indicating effectively drier conditions. Increases in the percentage of Petrophytum, characteristic of moister habitats, 

may indicate mesic episodes. Near-disappearance of both 

these species during the ensuing late Wisconsin (fig. 18) 

probably was caused by competition with more robust 

mesophytes.

While fluctuations of Scopulophila and rock spirea 

appear to reflect short-term changes, the longer duration 

decline in shadscale, accompanied first by an increase in
LATE QUATERNARY VEGETATION AND CLIMATE 31

SAMPLE | 

NUMBERS

PRESENT- 

<

37-

38-

39-

40-

42-

43

44-

45-

46-

3(mod)

> *

3(8)3

3(3)

3(7) 2 «

I 

\ 

\

^ \ 

\

]

\ i *

120 12 20 0 4 0 8 16 24 32 40 0 804 12 20 28 36 0 8040 8 16 24 32 900 

 PERCENT OF NUMBER OF IDENTIFIED SPECIMENS 

1300 1700

FIGURE 17. Relative frequencies of selected plant taxa in macrofossil assemblages from the Eleana Range-3 midden. (Vertical width of the bars is proportional to ±\O of the sample's radiocarbon date, except for the ER-3 (modern) sample assemblage; solid circle represents <1 percent of number 

of identified specimens.)

sagebrush and horsebrush (Tetradymia sp.) and then 

little-leaf mountain mahogany ( Cercocarpus intricatus), 

implies a progressive increase in effective moisture from 

32,000 to 25,000 B.R (fig.18). The Spc-2(3) fossil assemblage, 

dated at 23,300 B.R, indicates a reversal in this trend. It 

contains higher frequencies of shadscale and fewer mesophytes than older samples.

Isolated middens from elevations ranging from 790 to 

1,990 m provide additional data on enviroments of the 

Nevada Test Site during the last millenia of the middle 

Wisconsin. The oldest are broadly correlative with the 

Spc-2(ll) samples. At the lower end of the elevational 

gradient, in the Amargosa Desert, the OC-3(1) assemblage is radiocarbon-dated at about 33,000 B.R (fig. 14; 

table 6). Abundant rubber rabbitbrush ( Chrysothamnus 

nauseosus) and juniper in this midden sample indicate 

steppe vegetation with scattered trees. At the upper end 

of the altitudinal gradient, the Eyrie-5(2) assemblage, 

from a south-facing slope at an elevation of 1,860 m in 

the Sheep Range, is dated at 30,740 B.R (figs. 13,14). It 

records a xerophytic juniper woodland with pricklypear 

(Opuntiapolyacantha), sagebrush, and little-leaf mountain mahogany (Spaulding, 1981, table 23).

Younger macrofossil assemblages, dating from 28,300 

to 23,300 B.P., also yield records of juniper woodland 

with a diverse complement of xerophytic woodland and 

Great Basis Desert shrubs (Spaulding, 1981). Juniperus 

osteosperma was the only frequent arboreal species in 

this widespread woodland; pinyon pine is virtually unknown 

from the middle Wisconsin middens in the northern 

Mojave Desert. Occasional limber pine and white fir 

(Abies concolor) in the highest middle Wisconsin assemblage, 

SC-1(3) at an elevation of 1,990 m in the Sheep Range 

(fig. 14), indicate that this site was near the lower limit of 

montane conifer vegetation (Spaulding, 1981, p. 111).

Middle Wisconsin juniper-desert shrub assemblages 

from this region are broadly analogous to present vegetation at dry lower reaches of woodland. Contrasting estimated modern temperature and precipitation at such a 

site (the Eleana Range locality) with that for the Specter 

Range-2 site (table 5) indicates that average annual 

precipitation at about 30,000 B.R was 10 to 25 percent 

more than at present and that mean annual temperatures were at least 3°C lower than at present. The lower 

woodland boundary in more arid parts of the Sheep 

Range lies at about an elevation of 1,980 m. Calculations
COto

w 

o7 20 

< £ W Z -j LU 22 o w U QJH EL 24Z LU« U.

< s

r. w

DC LU 30

P 32

<

^ 34

r^fi

" 2(2) 1v r- 'Klz- 2(12)- 2(6)- 2(8)

2(10)

-2(11)r -_ T\\\ SBSS $$i'$ .,... .. ?] i^.) ; - ? i I l"}tl

0 100 10 20 30 40 500 10 20 30 400 10 20 300 10 20 30 40 50 600 10 200 10 20 30 40 0 100 

PERCENT OF NUMBER OF IDENTIFIED SPECIMENS 

800 1600

EXPLANATION

ABUNDANT TAXA 

[__I Shadscale 

Utah juniper

KV\\J Pinyon pine and '^^ Utah juniper

FIGURE 18. Relative frequencies of selected plant taxa in macrofossil assemblages from the Specter Range-2 midden. Vertical width of the bars is proportional to ±la of the sample's 

radiocarbon date (table 6), except for the Spc-2(8) and Spc-2 (modern) samples. Open bars for samples Spc-2(8) and Spc-2(ll), denote uncertain chronologic positions; solid circle 

represents < 1 percent of number of identified specimens. See table 6 for radiocarbon dates on those samples.)
LATE QUATERNARY VEGETATION AND CLIMATE 33

based on an elevational depression of juniper of 790 m (to 

the Specter Range-2 site at 1,190 m) and a lapse rate of 

0.5°C/100 m yield a ATa value of -4.0°C. However, calculations based on an elevational depression of 1,190 m to 

the Owl Canyon locality (790 m) yield a ATa of -6.0°C. 

The altitudinal zonation of vegetation in the northern 

Mojave Desert during the Wisconsin glacial age was 

unlike zonation that occurs under the present climatic 

regime. Utah juniper ranged from elevations less than 

800 m to at least 2,000 m; xerophytic woodland and 

steppe shrubs were common associates over much of its 

1,200 m altitudinal distribution. Arboreal species that 

often occur with Utah juniper at present (such as pinyon 

pine and ponderosa pine at higher elevations) are rarely 

recorded or completely missing from the fossil record. 

Trees most commonly associated with juniper in fossil 

assemblages from the higher altitude Sheep Range sites 

(Spaulding, 1981) are xerophytic subalpine conifers, 

bristlecone pine (Pinus longaeva) and limber pine (Pinus 

flexilis). Present extent of such plant associations in the 

Sheep Range is compared in figure 19 with their documented distribution in the Nevada Test Site area during 

the middle Wisconsin; the comparison illustrates an apparent paradox. An increase in effective moisture sufficient 

to permit Juniperus osteosperma to grow at xeric lowaltitude sites like Owl Canyon should have allowed other 

arboreal species to become successfully established at 

least at elevations above 1,500 m, assuming that gradients of effective moisture were the same then as now. 

However, xerophytic juniper woodland occurred on moist 

as well as dry sites to an elevation of at least 1,750 m 

(figs. 14,19); perhaps lapse rates of precipitation during 

the Wisconsin were different from present rates.

LATE WISCONSIN ENVIRONMENTS

The late Wisconsin stade of North America, the last 

period of major continental ice-sheet expansion, is correlated with oxygen-isotope stage 2 in deep-sea cores, coeval 

with the late Weichselian and Devensian stades of Eurasia 

(Bowen, 1978; Flint, 1971). Radiocarbon analyses of subsurface sediments from Searles Lake, California, 160 

km southwest of the Nevada Test Site, provide the best 

independent dates for the duration of this period in the 

Mojave Desert. The Parting Mud unit of Searles Lake 

encompasses the entire late Wisconsin; an average of 

seven radiocarbon dates on disseminated carbon from 

the bottom 50 cm of the unit is 23,300 ±1,175 B.P. (Stuiver 

and Smith, 1979, p. 74). Applying a correction factor of 

-900 radiocarbon years to this age to compensate for low 

radiocarbon per carbon ratios in high-bicarbonate waters 

(Peng and others, 1978, p. 327) yields a date of 22,600±1,175 

B.P. for initiation of late Wisconsin conditions at Searles 

Lake. The corrected average of seven radiocarbon dates

from the top of the Parting Mud (Stuiver and Smith, 

1979, p. 73), marking the end of late Wisconsin conditions, 

is 9,600±165 B.P.

VEGETATION

A date of about 22,600 B.P. for the beginning of late 

Wisconsin environmental conditions in the Mojave Desert is in accord with packrat-midden evidence from the 

Nevada Test Site. Although a gradual trend toward 

more mesophytic vegetation at Specter Range-2 began 

as early as 26,000 B.P. (fig.18), major biotic turnover 

from a juniper-shadscale to pinyon-juniper woodland did 

not occur until after about 23,300 B.P. (sample Spc-2( 3)) 

(table 6). Indeed, the Spc-2(3) assemblage indicates a 

reversal to conditions drier than those recorded by sample Spc-2(6) dated at about 25,000 B.P, and sample 

Spc-2(12), dated at about 26,000 B.P. (fig. 18).

The 4,000-year hiatus between sample Spc-2(3) and 

the late Wisconsin age Spc-2(2) assemblages (figs. 14, 

18) provides only a maximum age of 23,300 B.P. for the 

beginning of the late Wisconsin. No middens from the 

Nevada Test Site yield additional samples dating to this 

period except Specter Range-3A. This rather poorly dated assemblage (20,200±1,800 B.P.) (table 6) yields no 

evidence for a major vegetation change. Samples from 

the South Crest midden in the Sheep Range, a xeric site 

at an elevation of 1,990 m (fig. 12) document a transition 

from juniper to subalpine-conifer woodland prior to 

21,700±500 B.P. (fig. 14) (Spaulding, 1981, p. Ill, fig. 

27). This change, from a xerophytic juniper woodland to 

one apparently dominated by bristlecone pine (Pinus 

longaeva) and limber pine (Pinus flexilis), marks the 

initiation of a stadial climatic regime. Hence, packrat 

middens provide bracketing radiocarbon dates of 23,300 

and 21,700 B.P. for the beginning of late Wisconsin 

climatic conditions in the vicinity of the Nevada Test Site.

The Wisconsin maximum, or full glacial, is dated at about 

18,000 B.P. (CLIMAP, 1976), although local glacial maxima varied by several thousand years (Gates, 1976, p. 

1138; Bowen, 1978). In the Sheep Range, there were two 

periods when subalpine vegetation occurred below 2,000 

m; either (or both) could represent the full glacial. The 

first, recorded by packrat middens from the South Crest 

and Eyrie localities in the Sheep Range, ended by 19,000 

B.P. The second, with midden evidence from the Eyrie 

and Deadman localities in the Sheep Range, occurred 

between 18,600 and 16,800 B.P. (fig. 14) (Spaulding, 

1981, fig. 27). The magnitude of the latter event appears 

to have been great; at the Eyrie and Deadman sites, 

there were changes from xerophytic vegetation characterized by Utah juniper and pricklypear cacti ( Opuntia 

polyacantha and Opuntiaphaeacantha) to subalpine vegetation dominated by limber and bristlecone pine (Spaulding, 

1981, tables 23 and 24) (fig. 14).
34

300CM

2500 

2000 

1500 

VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

14). They may conflict with evidence for extensive, xerophytic juniper woodland at higher elevations in the region. 

A mesophytic pinyon-juniper association at the Specter 

Range-2 site (an elevation of 1,190 m) contrasts with late 

Wisconsin-age plant fossil assemblages commonly lacking pinyon pine from elevations 1,500 to 1,970 m in the 

Sheep Range (fig. 14). The cause of this anomaly is not 

readily apparent.

The Eleana Range-2 packrat midden spans most of 

the last one-half of the late Wisconsin from 17,100 to 

10,600 B.R Samples older than 13,000 B.R document a 

limber-pine woodland that contrasts with both older 

middle Wisconsin records from the Eleana Range-3 site 

and present desertscrub and sparse woodland at the 

locality (figs. 15,16). Changes in macrofossil frequencies 

toward the end of the limber-pine phase at Eleana Range-2 

appear to reflect late-glacial climatic change. A trend 

toward effectively drier conditions is indicated by the 

decline of silvery-lupine (Lupinus cf. argenteus) and fernbush ( Chamaebatiaria millefolium), two extralocal shrubs, 

accompanied by increasing relative frequencies of the 

xerophytic shrub, dwarf-goldenweed (Haplopappus 

nanus) (fig. 20). Decreasing relative percentages of plants 

typical of current Great Basin steppe (Artemisia sec. 

Tridentatae, Tktradymiasp., Chrysothamnus spp.) accompany these changes. This trend may have started as early 

as 16,000 B.R and appears to have been well underway 

by 13,000 B.R Variations in percentages of mountain 

mahogany ( Cercocarpus ledifolius) may represent reversals, when available moisture was somewhat higher 

(fig. 20). These data are in general accord with the 

record from Searles Lake (fig. 1), indicating a change at 

about 16,200'B.R (corrected date) from a lake at its 

maximum expansion to one undergoing dessication, with 

some reversals (Smith, 1979, p. 111).

The trend of increasingly xerophytic vegetation at 

Eleana Range-2 culminated in a profound change between 

13,200 and 11,700 B.R Limber pine-shrub woodland 

gave way to a community apparently dominated by 

Utah juniper, pinyon pine, and pricklypear (Opuntia 

polyacantha) (fig. 20). This transformation from a plant 

association with subalpine and steppe affinities to one 

resembling modern woodland in nearby mesic habitats 

signals the end of Wisconsin vegetation conditions at 

this site. Indices of similarity (fig. 21) show that latest 

Wisconsin ER-2(1) and 2(2) assemblages have many 

more species in common with current vegetation than do 

the middle Wisconsin samples from the nearby Eleana 

Range-3 site. Presumably this reflects a fundamental 

alteration of the regional climate. Climate during the

Specter Range-2 midden samples recording a meso- terminal Wisconsin, although somewhat more mesic than 

phytic pinyon-juniper woodland between 19,300 and 18,700 the present, was quite unlike the climate of either the 

B.R (fig. 18) do not appear to correspond to either period middle Wisconsin interstadial or most of the late Wisconof lowered subalpine vegetation in the Sheep Range (fig. sin stadial.

1000 

MESIC XERIC MESIC XERIC

500^

FIGURE 19. Distribution of middle Wisconsin juniper-shrub macrofossil assemblages compared to the modern extent of similar associations in the Sheep Range. Abbreviations for the fossil sites are: BH, 

Black Hills; Ey, Eyrie; OC, Owl Canyon; SC, South Crest; Spc, Specter 

Range; WC, Wagon Canyon; WW, Willow Wash. Abbreviations for 

the modern plant-community types are: SC, subalpine-conifer woodland; F-P, white fir-pondei-osa pine (Abies concolor-Pinus ponderosa) 

forest; EC, evergreen sclerophyll chaparral; P-J, pinyon-juniper 

woodland; DS, desertscrub. Stippled pattern shows distribution of 

similar assemblages during the middle Wisconsin and present day.
PRESENT

 oc 

uj O

CONCENTRATION, IN GRAMS PER KILOGRAM PERCENT OF NUMBER OF SPECIMENS 

FIGURE 20. -Abundance of selecter plant taxa in macrofossil assemblages from the Eleana Range-2 (ER-2) midden. A modern sample from the nearby E

presented at the top for comparison. Concentration values for the tree species are grams of fossils of a given taxon per kilogram of sorted matrix. Abu

of shrub and succulent species are presented as percentages of NISP-AT (Number of identified specimens excluding arboreal taxa). Solid circle repr

of identified specimens.
36 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE 

100

(8)3

 Eleana Range 3-

20

10 12 14 16 18 V 36 38 40 

RADIOCARBON AGE, IN THOUSANDS OF YEARS BEFORE PRESENT

42 44 46 48

FIGURE 21. Changes in similarity between Wisconsin and modern flora of the Eleana Range locality (note the break and change in the time scale; 

Sorensen's index of similarity is to the left). Compare the generally small indices of similarity for the late Pleistocene floras with the inferred 

continuity of physiognomy and structure of the vegetation (figs. 15, 16). Horizontal bars indicate ±l<7of that assemblage's radiocarbon age.

CLIMATIC REGIME

The record of global enviromental change shows that 

late Wisconsin climates represent maximum departure 

from present interglacial conditions (CLIMAP, 1976; 

Bowen, 1978). A perspective on environments of this 

period in the vicinity of the Nevada Test Site is gained by 

contrasting reconstructions presented here with earlier 

paleoclimatic models proposed for this region.

The most obvious evidence for differing ice-age climates 

in the Southwest are the empty basins that once contained 

vast freshwater lakes. In Nevada and Utah, the estimated total area of water during the late Wisconsin 

exceeds 89,000 km2 (Mifflin and Wheat, 1979, p. 53-55). 

Antevs (1948, p. 172-174; 1952, p. 98) correlated maximum 

expansion of these lakes with the greatest development 

of continental ice sheets in the Northern Hemisphere, 

a hypothesis corroborated by more recent studies 

(Broecker and Orr, 1958; Morrison and Frye, 1965). Their 

expansion most often has been attributed to greatly 

increased annual precipitation (50 to 100 percent over 

current amounts), coupled with a modest decline in average 

annual temperatures (2.5° to 5.0°C below those of the 

present) (table 7). This "pluvial" model of late Wisconsin 

climate in the Southwest invokes equable temperatures 

(cool summers and mild winters), characterized by considerably more rainfall than at present (Van Devender 

and Spaulding, 1979; Wells, 1979). However, the implicit 

climatic assumptions in the term "pluvial" demand 

rigorous testing.

Reconstruction of late-glacial vegetation based on 

fossil-pollen analysis have provided support for the pluvial model of southwestern climate. In particular, the 

hypothesized existence of extensive areas of ponderosa 

pine parkland and pinyon-juniper woodland was taken as 

evidence of mild, moist conditions (Martin and Mehringer, 

1965; Mehringer, 1965, 1967). However, the macrofossil 

record of xerophytic vegetation in the Mojave Desert 

fails to verify these reconstructions (Wells and Berger, 

1967, p. 1647; Spaulding, 1981, p. 207-208). More recently, Wells (1979, p. 311) has suggested that packratmidden data also indicate an equable late Wisconsin 

climate, characterized by a "*** pluvial increase in 

precipitation over the Southwest." One aspect of lateglacial biogeography used to support this thesis is the 

gradient of decreasing lower limits of pinyon pine at 

fossil sites with declining latitude, from the Mojave 

to the Sonoran Deserts. In the western Sonoran Desert, 

Pinus monophylla occurred as low as an elevation of 

510 m (Van Devender and Spaulding, 1979, table 1); 

in the northern Mojave Desert, its lowest fossil record 

is more than twice as high (1,190-m elevation at the
LATE QUATERNARY VEGETATION AND CLIMATE 37

TABLE 7. Paleoclimatic reconstructions for the full-glacial period of the American Southwest

\ATa , changes in °C (degrees Celsius) in annual temperature; ATS changes in °C in summer temperature; ATW , changes in °C in winter temperature; AP, change in annual 

precipitation in cm IcentimetersI; P, AP/modern P; %E (evaporation), /IB/modern E]

Author

Antevs (1952)

Antevs (1954)

Bachhuber and McClellan ( 1977 )

Brakenridge (1978)

Broecker and Orr (1958)

Galloway (1970)

Leopold (1951)

Mifflin and Wheat (1979)

Reeves (1966)

Snyder and Langbein (1962)

Van Devender ( 1973 )

'Minimum estimate.

2State-wide average.

Data base

Hydrologic budgets

Relict snowlines

Foraminifer

distributions

Relict cirques and

cryogenic deposits

Hydrologic budgets

?Solifluction

deposits

Hydrologic budgets

and snowline

changes

Hydrologic budgets

Hydrologic budgets

Hydrologic budgets

Packrat middens

Location

Lake Lahontan, Nevada

North-central New Mexico

Lake Estancia, New Mexico

Montana to Arizona

(lat 45°40'N to 33°20'N)

Lake Lahontan, Nevada

Sacramento Mountains,

New Mexico

Lake Estancia, New Mexico

Nevada, state-wide

Llano Estacado, west Texas

Lake Spring, Nevada

Western Arizona

ATQ ATS ATU,

-2. 5 to 

-3.0

-5.6 

-9.7 

1-7.0 

-5.0 

-10.5 -10.0 

-6.6 -9.0 -2.8

-2.8 

-5.0 -8.0 

3 -5.0 4_ 7 .2 

_3.0to 

-3.9

AP

+ 8 to

+ 16

+ 23

 

0

+21

-4.6

+ 18 to

+ 25

+ 8.4 to

+ 24

+ 39

+ 20

+ 12. 3 to

+ 22.0

%P

50 to

100

 

 

0

80

 

50 to

70

268

89

67

 

%E

-31

-39 to

^6

-10

-27

-30

 

Extrapolated by Morrison (1965); Schumm (1965); and Mifflin and Wheat (1979).

4Extrapolated by Schumm (1965) and Bnjckenridge (1978).

Specter Range-2 site)2 , and it was uncommon below 

1,550 m (Spaulding, 1976, p. 160) (fig. 14). Spaulding 

and others (1983) decline to accept Wells' (1979, p. 324) 

hypothesis that this vegetation gradient represented 

"*** pluvially increased summer rain***"; instead, they 

propose that it was caused by the near-absence of summer 

rain north of about lat 36°N. A second argument advanced 

by Wells (1979, p. 320) to support the model of an 

"equable glaciopluvial" is that: "In the Mojave Desert 

province, the upper part of the Pleistocene woodland 

zone was similar to the more mesic phases of the existing 

pinyon-juniper woodland*** (Wells and Berger, 1967)." 

The only macrofossil record of mesic pinyon-juniper 

woodland north of lat 35°N. reported by Wells and 

Berger (1967, table 1) is of apparent early-Holocene age 

(9,450±90 B.P.) and is largely irrelevant to the discussion of late Wisconsin climates. Based on an analysis of 

over 30 Wisconsin-age assemblages, Spaulding (1981, p. 

184) notes that pinyon and other mesophytic woodland 

plants are actually rare or missing from glacial-age woodland vegetation in the northern Mojave.

The paleoecological record from the Nevada Test Site 

and vicinity reveals a late Wisconsin vegetation dominated 

by plant species adapted to relatively cold, dry environments.

2Recent (October 1983) discovery of pinyon pine (Pinus monophylla) in a midden 

from the Stripped Hills, about 10 km west of the Specter Range-2 site, establishes a 

lower elevational record of 1,090 m for this species in the northern Mojave Desert.

There is no evidence for the presence of frost-sensitive 

desert plants, such as creosote bush, desert spruce, or 

white bursage, even at lowest elevation sites. Also, at 

higher elevations, there are few glacial-age fossils of 

plants characteristic of moist, temperate environments, 

such as ponderosa pine, Gambel oak, or Rocky Mountain 

juniper (Juniperus scopulorum). Instead, there was a 

zone of xerophytic pygmy-conifer woodland dominated 

by Utah juniper and, on rare occasion, single-needle 

pinyon pine and juniper together, from the lowest elevation 

sites up to elevations of between 1,800 and 2,000 m. A 

zone of subalpine conifer woodland characterized by limber 

pine on volcanic rocks, and limber pine and bristlecone 

pine together on calcareous substrate, occurred above an 

elevation of about 2,000 m (fig. 14) (Spaulding, 1981). 

Great Basin Desert and steppe shrubs, such as sagebrush, horsebrush ( Tetradymia sp.), and rabbittbrushes 

( Chrysothamnus spp.) were widespread in both types of 

woodland. There is no evidence for the distinct zone of 

mesophytic montane conifers (dominated by Pinus, 

ponderosa, Abies concolor, and Juniperus scopulorum} 

that currently separates pygmy conifer from subalpine 

woodland (fig. 14). These macrofossil data indicate a 

climate quite unlike that stipulated by pluvial models. 

Lower limits of woodland plant species were depressed 

during the Wisconsin, although the amount of elevational 

displacement varied among different taxa (fig. 22). Minimumdisplacement estimates for the two conifers most common
38 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

MINIMUM

DISPLACEMENT

(METERS)

1070

FOSSIL OCCURRENCES ( ) AND PRESENT RANGE ( ) 

 > «j> {§) > ) Pinus flexilis

580 > P. longaeva

P. ponderosa

-720 ® ) Abies coneolor

-770 Pinus monophylla

-1200 Juniperus osteosperma

-1150 /7//>es cf. velutinum

-670

-690

 ) Symphoricarpos 

cf. longiflorus

Fallugia paradoxa

320 <§ Atriplex confertifolia

LU LU c 

rr\ 1 3

D U. 

Z O L J.J

500 1000

CURRENT ELEVATIONAL 

RANGE

1500 2000 

ELEVATION, IN METERS

EXPLANATION

 WISCONSIN FOSSIL RECORDS OF 

SELECTED TREES AND SHRUBS

2500 3000

® TWO OR MORE FOSSILRECORDS 

AT A GIVEN ELEVATION

FIGURE 22. Current elevational range and Wisconsin fossil records of selected trees and shrubs; estimates of minimum displacement are to the left 

and (except for Atriplex confertifolia) are the elevation of a species' lowest fossil record subtracted from the elevation of its present lowest occurrence. 

All sites are north of lat 36°20' N. and south lat 37° N., west of long 115° W. and east of long 117°W., on calcareous substrate only.

in the late Wisconsin vegetation of southern Nevada, 

limber pine and Utah juniper, are among the greatest 

estimates; both occurred more than 1,000 m below their 

current lower limits. If it is assumed that the lower limit 

of these two species is determined by evapotranspirational 

stress caused by high summer temperatures, lapse-rate 

calculations can be used to derive estimates of full-glacial 

summer temperature declines (ATS }. Studies by Major 

(1977 p. 65) of present-day temperature regimes in arid 

and semi-arid mountains of California indicate summer 

lapse rates of -0.6 to -0.75°C/100 m. Applying these 

rates to displacement values for juniper and limber pine 

yields minimum estimates of ATS of about -6° to -9°C

(table 8). The range of overlap of values for the two 

species is from about -7° to -8°C.

Relative decline of full-glacial winter temperatures 

( ATW ) is a critical parameter in these reconstructions. A 

modest ATW of, say, -3.0°C would indicate an equable 

temperature regime with a low annual range of variation 

and a modest estimate of mean annual temperature decline. 

However, the marked lack of thermophilous plant species 

in even lowest elevation middens provides a strong argument 

against a conservative estimate of ATW. An example is 

creosote bush, which, according to Beatley (1974, table 

1), is excluded from sites with mean minimum temperatures 

lower than -1.4°C, and sites with extreme minimum
LATE QUATERNARY VEGETATION AND CLIMATE 39

TABLE 8. Estimates of minimum displacement of Utah juniper and limber pine and resultant 

calculations of the full-glacial decline in summer temperatures for southern Nevada

[Lowest elevation fossil record for Juniperus osteosperma is from Mehringer (1967); lowest record for Pinus flexilis is 

from Spaulding (19811. V Ts, relative decline in full-glacial summer temperatures; °C. degrees Celsius; m, meter]

Species

Lowest fossil site; 

elevation

Present 

lower limit

Minimum 

displacement

Juniperus osteosperma 

Pinus flexilis

Tule Springs, Las Vegas 1,900 m 1,200 m 

Valley; 700 m

Willow Wash-4, Sheep Range; 2,650 m 1,065 m 

1,585 m

Lapse rate calculations of A Ts

Lapse rate1 

(°C/100m)

-0.60

- .70

- .75

- .60

- .70

- .75

Minimum 

displacement

1,200 m

1,200 m

1,200 m

1,065 m

1,065 m

1,065 m

ATS

-7.2°C

-8.4°C

-9.0°C

-6.4°C

-7.5°C

-8.0°C

iValues from Major (1977).

TABLE 9. Range of minimum temperature values at 39 sites presently supporting creosote 

bush (Larrea divaricata), and estimates of the minimum decline in late Wisconsin winter 

temperatures necessary to exclude that species from all sites

\ATia, postulated minimum relative decline in full-glacial winter temperature; °C, degrees Celsius; data are from

Beatley (1974, table 1|]

Mean Minimum Temperatures

Lowest value (A) 

-1.4°C(site34)

Highest value (B) 

4.5°C (site 5)

ATW (A-B) 

-5.9°C

Mean of Extreme Minimum Temperatures

Lowest value (A) 

-16.8°C (site 34)

Highest value (B) 

-10.8°C (site 15)

ATW (A-B) 

-6.0°C

temperatures below -16.8°C (table 9). Because a ATW of 

less than -6.0°C would leave some low-elevation sites in 

the region with mean minima above -1.4°C (as measured 

by Beatley's method) and not exclude Larrea divaricata 

from the study area, full-glacial decline in winter temperatures 

must have exceeded that value (table 9).

Shadscale (Atriplex confertifolia] was widespread in 

the late Wisconsin juniper woodlands of southern Nevada. 

It occurred at higher elevations than it does today, probably 

in response to the absence of potential competitors that 

appear to determine its present upper limits (Spaulding, 

1981, p. 205). There is little fossil evidence for desertscrub 

species that occur at intermediate elevations above shadscale 

today, and the glacial-age juniper woodland seems to 

have been less diverse than present vegetation at the 

fossil sites (Spaulding, 1981, p. 194-199). This apparent 

decrease in floristic diversity is attributed to winter 

temperatures lower than those indicated by models of 

equable late-glacial climates. Expansion of shadscale, 

today typical of the most frigid desert habitats in the 

vicinity of the Nevada Test Site (Beatley, 1974, 1975), 

provides strong qualitative support for a relatively large 

decline in late Wisconsin winter temperatures and a 

fairly arid precipitation regime.

Averaging these minimum estimates of ATS and ATW 

yields a minimum value of about -7°C for the decline of 

mean annual temperature (ATa) during the late Wisconsin. 

Subtracting this estimate of ATa from the current mean 

annual temperature at the lowest elevation fossil locality, 

Owl Canyon at 795 m, yields a range of temperature 

values (10° to 11°C) characteristic of the lower reaches 

of modern woodland in the region (table 5). This is in 

agreement with glacial-age macrofossil assemblages from 

low-elevation sites dominated by dry-woodland and colddesert plants.

Reconstruction of the late Wisconsin precipitation regime 

of the Nevada Test Site and vicinity begins with estimates 

of seasonally. The late-glacial flora indicates a pronounced 

absence of summer rain. The abundance of Great Basin 

Desert taxa and scarcity of plants that today appear to 

require at least some summer moisture (such as Quercus 

spp., Coleogyne ramosissima) indicates the contribution 

of warm-season rainfall was less than 10 percent of the 

annual total. This is not unexpected because, during a 

glacial climatic regime, lowered temperatures would tend 

to suppress development of subtropical high-pressure 

systems presently responsible for winds that bring summer 

rains to the monsoonal Southwest (Van Devender and
40 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

Wiseman, 1977) and impede development of surface lowpressure systems that draw maritime air northward from 

the Gulf of California (Huning, 1978, p. 80).

The late Wisconsin flora of the northern Mojave Desert 

provide no evidence for the drastic relative increase in 

annual precipitation (in excess of 50 percent above present 

values) proposed by some authors (table 7). At this 

point, general analogs seem to provide the best approach 

for deriving estimates of full-glacial precipitation. In the 

White Mountains of California (fig. 1), average annual 

precipitation (Pa) near the lower limit of subalpine (limber 

pine) woodland (at about 2,800 m) (Mooney and others, 

1962, fig. 4) is calculated to be about 300 mm, based on a 

value of 350 mm/yr 1 at the Crooked Creek Research 

Station (at an elevation of 3,096 m) (La Marche, 1973, p. 

635), and a local precipitation lapse rate of 17 mm/100 m 

(Major, 1977, p. 66). Assuming this value (300 mm) 

approximates average annual precipitation during the 

full glacial at the Eleana Range locality, the estimated 

relative increase of Pa is 33 to 39 percent above today's 

amounts (table 5). This modest increase is supported by 

two tree-ring chronologies from the Eleana Range-2 packrat 

midden (fig. 23). Annual-ring widths of these two 

radiocarbon-dated limber pine specimens are extremely 

small, averaging less than 0.2 mm. It is unlikely that 

such sensitive tree rings would have been produced except 

by trees under appreciable stress. Estimates of relative 

increase in precipitation of less than 40 percent also are 

consistent with the full-glacial record of pinyon-juniper 

woodland at the Specter Range-2 site. A 30 to 40 percent 

increase over today's amounts (table 5) would result in 

values estimated to be between 226 and 265 mm/yr 1 . 

Present precipitation at Ely, Nevada, which lies at the 

lower limit of pinyon-juniper woodland, is 221 to 245 

mm/yr1 (table 4).

THE TRANSITION PERIOD

Several authors (Wright, 1976; Davis, 1981; Watts, 

1980) have emphasized the time-transgressive nature of 

vegetation change at the end of the last glacial age in 

other parts of the continent; this also appears to have 

been the case in the Mojave Desert. Contrary to the 

assertion of Van Devender and Spaulding (1979, p. 709), 

the packrat-midden record provides no evidence for 

contemporaneous vegetation change at all sites at about 

11,000 years ago (Spaulding, 1983, p. 256). Because 

synchroneity of vegetation change is not evident, there 

is a need for arbitrary time lines. The conventional dates 

of 10,000 B.P. for the end of the Wisconsin and 8,000 B.P. 

for the end of the early Holocene are adopted here.

MAJOR VEGETATION CHANGES

The latest Wisconsin (12,000 to 10,000 B.P.) vegetation 

at the Eleana Range-2 site was dominated by plants that 

presently occur nearby although a greater variety of 

mesophytes occured, including some full-glacial relicts. 

The abundance of pinyon pine and Utah juniper in ER-2( 2) 

and 2( 1) also indicates a denser vegetation than exists at 

the site today. Progressive desertification after about 

10,600 B.P. caused opening of the pinyon-juniper woodland 

and final extirpation of such extralocals as limber pine 

and curl-leaf mountain mahogany.

Development of postglacial woodland at the Eleana 

Range occurred between about 13,200 and 11,700 B.P. 

This is surprisingly early, relative to the date of about 

11,000 B.P. for the end of Wisconsin vegetation conditions 

throughout the Southwest suggested by Van Devender 

and Spaulding (1979, p. 706). However, the Eleana Range 

record agrees with many glacial, oxygen-isotope, and 

pollen chronologies that show impact of increasing northernhemispheric temperatures by at least 12,000 B.P. (Dansgaard 

and others, 1971; Porter, 1971; Barnosky, 1981; Mehringer, 

1967). The maximum of northern hemisphere summer 

insolation was reached by about 11,000 B.P. (Broecker 

and van Donk, 1970, fig. 10; Ruddiman and Mclntyre, 

1981, fig. 2). Thus, an early date for the response of 

vegetation at the Eleana Range-2 site to a warming 

climate is not unexpected, particularly if species such as 

limber pine were near the limits of their environmental 

tolerance here during late Wisconsin time.

An early change to postglacial vegetation conditions 

also took place at low elevations on the periphery of the 

Amargosa Desert. The Point of Rocks midden records 

(at elevations ranging from 900 to 930 m) indicate that, 

at least at some sites, woodland gave way to desertscrub 

prior to 14,800 B.P. The surprisingly early dates for 

desert vegetation at the Point of Rocks-3 site (14,800 

B.P.) and at the Point of Rocks-1 site (11,800 B.P.), 

indicates that woodland vegetation was not continuous 

below an elevation of about 1,000 m after about 15,000 

years ago (Spaulding, 1983). Instead, low elevations in 

the vicinity of the Nevada Test Site may have supported 

a mosaic of woodland, occupying mesic habitats, and 

desertscrub on xeric sites.

In contrast to the early records of shrub vegetation in 

the lowlands, middens from higher elevation desert sites 

show that juniper woodland persisted as late as 9,400 

B.P. in the Sheep Range (Spaulding, 1981, p. 191) and 

7,800 B.P. in the Spotted Range (Wells and Berger, 1967, 

table 1). These localities were in the upper part of the late 

Wisconsin zone of pygmy-conifer woodland (above an 

elevation of 1,200 m) (fig. 14). Effective moisture was 

sufficient at such higher altitudes to maintain xerophytic
LATE QUATERNARY VEGETATION AND CLIMATE 41

SAMPLE ER 2(5): 14,260±110 YEARS BEFORE PRESENT

10 20 30 40 50 60 70 80 90 100 110 120 130

SAMPLE ER2I4): 1 5,300±1 30 YEARS BEFORE PRESENT

50 60 

TREE-RING YEAR

100 110 120

FIGURE 23. Tree-ring chronologies from two limber-pine specimens from the Eleana Range-2 (ER-2) midden. (The radiocarbon date for each specimen also 

is shown; table 6.) The specimens are tied neither to a calendar year nor to the relative age of the tree and the time scale at the bottom is for illustrative 

purposes only. Cross-dating is not implied by the superposition of those two chronologies. Analysis by Harriet Garfinkel. Lincoln Laboratory, Massachusetts 

Institute of Technology.

woodland species after they had been extirpated from 

the lowlands.

An insight into the dynamics of vegetation change at 

the end of the glacial age is provided by contrasting 

similarity indices for midden samples from Owl Canyon 

and the Eleana Range. Macrofossil assemblages from 

the Owl Canyon-2 midden document vegetation conditions 

after juniper woodland gave way to desertscrub, and the 

two youngest assemblages from Eleana Range-2, after 

limber pine gave way to pinyon-juniper woodland. However, 

similarity coefficients between Owl Canyon-2 assemblages 

and the present vegetation at the Owl Canyon-2 site are 

less than 10, while those comparing ER-2(1) and 2(2) 

samples to the modern vegetaion exceed 70 (see Supplemental Data section) (fig. 21). The Eleana Range locality 

was near the upper limit of late Wisconsin pygmy-conifer 

woodland (fig. 14); plants such as juniper, pinyon pine, 

and pricklypear reached the Eleana Range-2 site soon 

after the triggering climatic change. However, thermophilous 

shrubs that typify present vegetation at Owl Canyon 

(such as creosote bush, desert spruce, and white bursage) 

were apparently absent from the region during the late 

Wisconsin. The dissimilarity between the latest Wisconsin 

and modern flora at Owl Canyon is thus ascribed, in 

large part, to lag time in northward migration of warmdesert shrubs.

The major vegetation change in the region at the end 

of the last glacial age, from subalpine-conifer to pinyonjuniper woodland and, at lower elevations, from pygmyconifer woodland to desertscrub, occurred at different 

times at different sites (fig. 14). An important variable 

that affected the timing of major vegetation change, 

exclusive of the timing of the forcing climatic change, 

was the position of the fossil site relative to the environmental 

tolerance of species growing there. Middens from xeric 

sites near the lower limit of a given vegetation zone (such 

as Owl Canyon, Point of Rocks, or the Eleana Range) 

record relatively early response to postglacial warming. 

Records from mesic sites, and from higher elevations 

within a given vegetation zone, are not as sensitive and 

document less vegetation response until the climate change 

had progressed quite far.

Desert vegetation took at least 6,000 years to spread 

over most of its present elevational range (fig. 14). In the 

northern Mojave, the transformation from woodland to 

desertscrub was nearly complete by about 9,000 B.P. 

These findings diverge from the model proposed by Van 

Devender (1977b, p. 190-191; Van Devender and Spaulding, 

1979, p. 708) indicating that widespread woodland persisted throughout the early Holocene in most of the 

Mojave Desert, abruptly giving way to desertscrub at 

about 8,000 B.P. Early Holocene woodlands probably
42 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

were more widespread farther south in the current 

Sonoran Desert.

Both final desiccation of the vast inland lakes of the 

Great Basin and ultimate demise of woodland vegetation 

in desert lowlands occurred between 10,000 and 8,000 

years ago. At Searles Lake, desiccation was complete by 

about 9,600 B.P., the end of a period of declining lake 

levels that, with one major reversal, began as early as 

16,200 B.P. (Smith, 1979, fig. 41; Peng and others, 1978, 

p. 325). In the vicinity of the Nevada Test Site, anomalous 

desertscrub vegetation had replaced woodland at most 

sites below an elevation of 1,600 m by about 9,000 B.P. 

(fig. 14). Anomalous desertscrub is a general term applied 

to past plant associations characterized by extralocal 

shrubs and succulents that also lack important elements 

of modern vegetation. Late Wisconsin and early Holocene 

middens from the periphery of the Amargosa Desert, 

and the Eureka Valley, document such vegetation (fig. 

14). Most shrub species abundant in the Point of Rocks, 

Owl Canyon-2, and Last Chance Range midden assemblages 

(at elevations between 800 and 960 m) typify present 

vegetation at elevations between 1,400 and 2,000 m.

It is not known when anomalous desertscrub vegetation 

gave way to plant communities characteristic of the 

present vegetation at the Amargosa Desert sites. At the 

Eureka Valley locality, 160 km to the northwest, final 

development of current plant associations was delayed 

until after 5,000 B.P. (fig. 24). The lag in this development, 

from the time of extirpation of woodland to establishment 

of desertscrub vegetation similar to today's, resulted in 

part from the time it took for warm-desert species to 

migrate northward. Expansion of these shrubs to 

more northerly latitudes probably began before 10,000 

B.P.; middens in the Amargosa Desert provide the earliest 

evidence for their arrival in the vicinity of the Nevada 

Test Site. Assemblages from Point of Rocks-1 and 2 

sites, dating between 10,000 and 9,000 B.P., are the 

oldest to contain such xerophytes as creosote bush (Larrea 

divaricata) and chaff-bush (Amphipappus fremontii). 

Creosote bush does not appear in the Eureka Valley 

record until about 5,500 B.P., and chaff-bush does not 

appear until 1,500 B.P. (fig. 24). Prior claims for the 

presence of creosote bush of Wisconsin age in the northern 

Mojave Desert (Spaulding, 1976, p. 160; 1980, p. 89) 

must await confirmation by radiocarbon dates run directly 

on those fossil remains. Until such tests are made, these 

earlier records must be considered dubious; they are not 

replicated in this study. Migration lags were an important 

aspect of postglacial vegetation development in the eastern 

United States (Davis, 1981; Watts, 1980) and, despite 

previous statements to the contrary (Van Devender and 

Spaulding, 1979, p. 710), appear to have played an equally 

important role in the transition to modern vegetation in 

the Southwest.

CLIMATES OF THE TRANSITION PERIOD

The latest Wisconsin and early Holocene vegetation of 

most of the Mojave Desert was xerophytic, relative to 

that at comparable sites in the Sonoran Desert. Desertscrub 

communities appear to have developed earlier in the 

Mojave. The oldest record of shrub-dominated vegetation 

in the vicinity of the Nevada Test Site exceeds 14,500 

years. In the southern Mojave Desert, evidence for the 

early inception (by at least 10,500 B.P.) of desertscrub 

comes from middens in the Marble Mountains, 230 km 

south of the Nevada Test Site (Spaulding, 1980). The 

elevation of these early desert-vegetation records in the 

Mojave Desert varies from 465 m in the Marble Mountains 

to 960 m in the Last Chance Range of Nevada. At the 

same time (11,500 to 9,000 B.P.), juniper woodland occurred 

at least as low as 520-m elevation in the Whipple Mountains 

of the western Sonoran Desert, 310 km south-southeast 

of the Nevada Test Site in the Colorado River Valley. 

Mead and others (1978, p. 185-186; Van Devender, 1977b) 

report that radiocarbon dates on these woodland assemblages 

are as young as 8,900 B.P. Other sites in western Arizona 

that confirm the presence of low-elevation woodland in 

the Sonoran Desert include those from the Artillery and 

New Water Mountains (Van Devender, 1973, table 3). 

Closer to the Nevada Test Site, in the extreme eastern 

part of the Mojave Desert, juniper woodland extended to 

at least an elevation of 560 m in the lower Grand Canyon 

(fig. 1). This early Holocene woodland was rich in shrub 

and succulent species; radiocarbon dates on these 

assemblages are as young as 8,900 B.P. (Phillips, 1977, 

table 1).

The early development of desertscrub vegetation in 

the Mojave Desert, and persistence of woodland in the 

Sonoran Desert and Grand Canyon, appears to have 

been a function of differing precipitation regimes. The 

cline of increasingly xerophytic vegetation from southeast 

to northwest parallels the existing gradient of warmseason precipitation from the summer-wet (monsoonal) 

Sonoran Desert to the summer-dry Mojave Desert. Thus, 

the dichotomy between paleovegetation of the two regions 

during the latest Wisconsin and early Holocene was 

probably also due to differences in the relative amount of 

summer rainfall. This author suggests that, beginning 

by 14,000 B.P., increasing summer temperatures led to a 

marked increase in summer, and perhaps autumn, 

precipitation in the present monsoonal Southwest (Sonoran 

and Chihuahuan Deserts). Transition period woodlands 

in these areas were probably maintained at low elevations 

by relatively high levels of effective moisture during the 

growing season. The Mojave Desert is farther removed 

from the sources of warm-season precipitation and may 

have been beyond the limits of major influence of this 

phenomenon. Desertscrub vegetation developed earlier 

in the Mojave Desert because there was inadequate
LATE QUATERNARY VEGETATION AND CLIMATE 43

o 

(/) 2 

Q

Z

-3 UJ lg«-

l a.

Z iu 

ul O

1" '

CC uj

0^8-

<

Samples 

EV3

EV2B 

EV1

EV2C

EV4(3) 

EV4(1) '

EV4(2)

EV5B

->

12H

14

16 1

EV5A

05050505050505050505050 

ESTIMATED RELATIVE ABUNDANCE

EXPLANATION 

 A VERY RARE (less than 5 fragments) OCCURRENCE

 CONNECTS CONSECUTIVE-AGE MIDDEN SAMPLES 

FROM THE SAME SITE

 CONNECTS SAMPLES FROM DIFFERENT SITES

FIGURE 24. A time series of packrat-midden samples from the Eureka View locality, northern Eureka Valley, Inyo County, California; estimated 

abundance of the species in the present vegetation is presented at the top for comparison; width of bars is equal to ±la of that sample's radiocarbon 

age (note break and change in time scale). EV, Eureka View; subjectively assigned relative abundance values are: 5, very abundant; 4, abundant; 

3, common; 2, occasional; 1, rare.

precipitation to compensate for increasing warm-season 

moisture deficits.

Between 12,000 and 8,000 years ago, the obliquity of 

the Earth was such that summer was a time of more 

intense insolation than it is today, and winters were 

less heated than at present (Bryson and Swain, 1981, 

p. 143-144; Kutzbach, 1981, p. 59). Peaks in northernhemispheric summer insolation and seasonal contrast 

may have resulted in 20 to 100 percent more summer 

rainfall than at present in some monsoonal regions (Kutzbach 

and Otto-Bleisner, 1982; Bryson and Swain, 1981, table 

2). Midden localities that document woodland vegetation 

in the desert West at this time, such as the lower Grand 

Canyon and the Whipple Mountains, are south and east 

of the Nevada Test Site and are closer to sources of 

tropical maritime air the Gulfs of California and Mexico.

The early postglacial woodland of the monsoonal Southwest 

probably did not result from persistence of the glacialage precipitation regime, as suggested by Van Devender 

(1977b, p. 192). Rather, juniper and other xerophytic 

woodland species may have been maintained at lower 

elevations than they occur at present by enhanced summer 

rainfall. Although there was probably a relative increase 

in summer rainfall over today's meager amounts in the 

Mojave Desert, it was insufficient to maintain woodland 

at low elevations.

At about 10,000 years ago, summer and fall precipitation 

in the vicinity of the Nevada Test Site may have exceeded 

present amounts by as much as 50 percent. This inference 

is based on the distribution pattern of woodland across 

the Southwest and the timing of its disappearance in 

different areas. Plant species indicative of increased summer
44 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

rainfall became more important in the Nevada Test Site 

midden record between 12,000 and 10,000 years ago. The 

abundance of Agave utahensis and cacti in the Owl 

Canyon-2 and Point of Rocks-2 assemblages is consistent 

with a thesis of increased warm-season precipitation 

during the Wisconsin to Holocene transition. In the 

Searles Lake area; the apparent latest Wisconsin expansion 

of shrub live-oak (Quercus turbinella) (Spaulding and 

others, 1983) may be evidence of increased summer rain. 

The interior race of this species is presently restricted to 

mountains of the monsoonal Southwest (Little, 1976, 

map 147). There may have been insufficient time for 

many other summer-rain dependent species to migrate 

into the area. Most appear to have been absent from the 

Southwest during the late Wisconsin (Van Devender and 

Spaulding, 1979, p. 708), and it may have taken them 

thousands of years to reach the borders of the presentday Mojave Desert.

The source of warm-season precipitation during the 

latest Wisconsin and early Holocene presumably was 

to the south in the Gulf of California and Pacific Ocean, 

or to the southeast in the Gulf of Mexico. Tropical storms 

of August through October that presently move up the 

trough of the Colorado River Valley may have been more 

common than they are today. There is no immediate 

evidence for a relative increase in precipitation over current values during the winter half-year, although effective moisture during the winter probably was greater 

than today. While summer temperatures are inferred to 

have been as much as 1° to 2°C higher than today, 

winter temperatures may have been 1°C lower than 

today. This is based on the observation that seasonal 

contrasts were unusually large in the northern hemisphere between 11,000 and 9,000 B.P. (Broecker and Van 

Donk, 1970, p. 190; Bryson and Swain, 1981, p. 143; 

Kutzbach and Otto-Bleisner, 1982).

THE LAST 8,000 YEARS

It generally is agreed that the middle Holocene was a 

time of increased northern-hemispheric temperatures 

(Deevey and Flint, 1957). However, estimates of the 

duration of this period of warm temperatures, and timing of the thermal maximum, differ from region to region. 

It appears that the period of maximum temperatures 

during the Holocene was time-transgressive (Wright, 

1976, p. 594). As with previous portions of this report, 

this climatic event is considered within the context of a 

time-stratigraphic unit, the middle Holocene. The date 

chosen for the beginning of the middle Holocene, 8,000 

years ago, is close to the time of final demise of woodland 

in high desert habitats of the northern Mojave Desert 

(fig. 14) (Wells and Berger, 1967, table 1), as well as its

decline throughout wide areas in the present Sonoran 

Desert (Van Devender, 1977b).

MIDDLE HOLOCENE CLIMATIC VARIATIONS

Pollen-stratigraphic data from north-central and northwestern North America are in general agreement with 

the Mojave Desert record. All show that the transition to 

postglacial vegetation conditions was complete by, at 

the latest, 9,000 B.P. (Barnosky, 1981; Webb and Bryson, 

1972; Heusser, 1977; Wright, 1976). The apparent conflict with evidence for delayed development of desert 

vegetation in the Sonoran and Chihuahuan deserts (Van 

Devender, 1977b; Van Devender and Wiseman, 1977, p. 

21) is probably due to more summer precipitation in 

these areas. Final extirpation of extralocals such as juniper in the lowlands of the monsoonal Southwest was 

delayed until the end of the early Holocene, when increased 

summer precipitation no longer compensated for warmseason moisture stress.

Martin (1963, p. 61) was among the first to suggest 

that the middle Holocene was a time of increased effective moisture, based on pollen data from southeastern 

Arizona. While little confirmation of an initial, early 

Holocene (10,500 to 8,000 B.P.) arid period is available 

(Van Devender, 1977b), Martin's hypothesis that there 

was enhanced summer rainfall between about 8,000 and 

4,000 B.P. has been strengthened by additional studies in 

the Chihuahuan Desert (Mehringer and others, 1967; 

Van Devender and Wiseman, 1977; Van Devender and 

Worthington, 1977). Lacustrine evidence indicates that 

this also was the case in the Mojave Desert, although the 

relative amount of summer rain probably was less. The 

hypsithermal-age saline lake in the Searles Basin (fig. 1) 

attained a depth of up to 45 m above the present playa 

surface. It may have been caused by a relative increase in 

frequency and amount of summer rain, although it is 

unknown why it was dry during the preceding early 

Holocene. An uncorrected radiocarbon date on wood 

from the Overburden Mud laid down by this saline lake 

is 3,520±190 B.P.; an uncorrected radiocarbon date on 

disseminated organic carbon is 6,630±390 B.P. (Smith, 

1979, p. 112, fig. 3).

Variations in the lower limit of pinyon-juniper woodland in the Sheep Range (fig. 1) also indicate increased 

effective moisture during the middle Holocene. Two middens from sites in current desert, about 150 m below the 

woodland boundary, contain abundant Utah juniper and 

common pinyon pine and are dated at 5,210±95 (the 

Desert View site) and 3,520±100 B.P. (the Basin Wash 

site) (fig. 14) (Spaulding, 1981, p. 209). Additional evidence for a moist hypsithermal in the vicinity of the 

Nevada Test Site includes the presence of extralocal
LATE QUATERNARY VEGETATION AND CLIMATE 45

pricklypears ( Opuntia polyacantka and Opuntia phaeacantha) in the Desert View midden, as well as the mesophytes longleaf bricked a (Bricklellia cf. longifolia) and 

desert-willow ( Chilopsis linearis) in the desertscrub assemblage from the Willow Wash-2 site in the Sheep Range 

(4,125±90 B.P.) (Spaulding, 1981, table 11).

As mentioned previously, it appears the middle Holocene 

also was a time of higher temperatures. Isolated middens from the Sheep Range, dating from about 4,130 to 

3,240 B.P., yield evidence for warmer winters. The record 

of desert-willow in the Willow Wash-2 midden is pertinent because the species is frost-sensitive and is restricted from such protected, cool sites today, even when there 

is adequate moisture. Warmer winter minima may be 

indicated by the presence of blue yucca ( Yucca baccata) 

in the CT-l(l) (3,310+100 B.P.) and Spires-1 middens 

(3,240±100 B.P.) (fig. 14); both sites presently lie more 

than 70 m above its upper limit (Spaulding, 1981, p. 136).

Northward migration of warm-desert shrubs continued through the middle Holocene. On xeric south slopes 

in the Eureka Valley (fig. 1), anomalous desertscrub 

characterized by shadscale, rayless brittlebush (Encelia 

virginensis), and cactus (Opuntia spp.) gave way to 

shadscale-creosote bush vegetation between 3,900 and 

2,600 B.P. (fig. 24). While the unusual aspect of midpostglacial plant communities at the Eureka View locality resulted in part from delayed immigration of thermophiles, 

many species that occurred on these xeric dolomite slopes 

during the middle Holocene are now restricted to more 

mesic habitats.

La Marche's (1973) dendrochronologic reconstruction 

of climate variation in the White Mountains of California, 

35 km northwest of the Eureka Valley (fig. 1), provides 

an independent data base for the middle and late Holocene. 

The remains of bristlecone pine (Pinus longaeva) trees 

occur far above present treeline there, which is rather 

firm evidence of fluctuations in its upper limit caused by 

long-term temperature changes. A period of relatively 

high temperatures is inferred from the start of the record 

at about 7,400 B.P. to between 3,500 to 3,000 B.P. La 

Marche (1973, p. 655) suggests that subsequent late 

Holocene lowering of treeline was caused chiefly by a 

decline in warm-season temperatures. For the purposes 

of this study, a date of 3,000 B.P. for the end of the 

middle Holocene is accepted.

LATE HOLOCENE FLUCTUATIONS

Although records of vegetation change over the last 

3,000 years are plentiful, they usually reflect environmental changes of a lower magnitude than most of those

discussed previously. Many late Holocene assemblages 

indicate increased effective moisture relative to both 

middle Holocene and modern conditions. In the Sheep 

range, the Canyon Two-l(l) midden sample (1,990±70 

B.P), at an elevation of 1,740 m, contains abundant 

juniper and common pinyon pine (fig. 14). An older 

sample from this midden, CT-1(2) at 3,310±100 B.P, 

contains only occasional juniper and no pinyon pine. 

This late Holocene record of woodland vegetation comes 

from a site that is surrounded by blackbrush desertscrub 

today. The current lower limit of woodland in this part of 

the range (fig. 12) is at an elevation of about 2,010 m, 

more than 200 m above the Canyon Two site (Spaulding, 

1977). Other middens from the Sheep Range that contain 

remains of woodland conifers 100 to 200 m below their 

current lower limits include the Basin Wash sample 

(3,520±100 B.P) and the Ey-2(l) sample at 2,920±90 

B.P. (fig. 11) (Spaulding, 1981, p. 141, p. 123-125).

Late Holocene vegetation change is evident in packrat 

middens from the Eureka Valley and the Specter Range. 

Assemblages from the Eureka Valley record final extirpation of such extralocals as indigo bush (Psorothamnus 

fremontii), cacti ( Opuntia basilaris and Opuntia echinocarpa), 

and desert spruce (Peucephyllum schottii), between about 

1,600 B.P and the present (fig. 24). A decline in the 

proportion and amount of summer precipitation may 

have caused local extinction of indigo bush and cacti. 

However, it is likely that lower winter temperatures 

eliminated desert spruce from this, its northernmost documented occurrence. The closest locality where Peucephyllum 

occurs today is on south-facing slopes of the Last Chance 

Range of California, 12 km southeast of the Eureka 

Valley sites.

Two assemblages from the Specter Range-1 site document desertscrub vegetation analogous to today's, although 

there appears to have been a shift in plant-community 

composition. Fourwing saltbush (Atriplex canescens) is 

the most abundant species in the sample dated at 300±100 

B.P. [sample Spc-l( 1)], while creosote bush and matchweed 

(Gutierrezia microcephala) are more important in the 

younger Spc-l(2) assemblage (lOO-foo B.P.) (table 6). 

This apparent shift to a xerophytic plant community in 

the last 300 radiocarbon years may be because of climatic change. An equally likely cause may be the effect of 

cattle grazing in the late 19th and early 20th century. A 

decline in the more palatable saltbush and an increase in 

unpalatable and disturbance-indicator shrubs (Larrea 

divaricata, Gutierrezia microcephala, Hymenoclea salsola) 

support the latter hypothesis. Similar observations are 

possible based on the data from subrecent packrat middens from the Eureka Valley (Spaulding, 1980).
46 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

ASSESSING PALEOENVIRONMENTAL 

RECONSTRUCTIONS

Packrat-midden analysis affords a high-resolution view 

of the environmental history of the Nevada Test Site and 

vicinity. However, potential errors and unknown variables that exist should be considered. Errors could be 

introduced in estimating modern climates at the fossil 

sites, in reconstructing past vegetation, or in extrapolating climatic parameters from reconstructions. Retrodictive 

studies, such as this one, describe phenomena that no 

longer exist; conclusions derived from such analyses 

cannot be tested through observation. However, they 

can be tested by attempts to replicate the fossil record 

and by application of proposed paleoclimatic parameters 

to models of physical systems, such as pluvial lakes and 

cryogenic deposits.

ACCURACY OF REPRESENTATION AND 

GENERAL ANALOGS

Plant-macrofossil assemblages from ancient packrat 

middens possess distinctive characteristics that permit 

identification of specific vegetation types. Analyses of 

modern middens in this study, and those performed by 

Cole (1981, p. 36-41; 1982), indicate that sufficient fidelity 

exists in the midden-vegetation relationship to permit 

accurate reconstruction to at least the community-type 

level (table 1). The possibility that first-order errors have 

been made in this study (such as reconstruction of juniper woodland when ponderosa-pine forest was actually 

present) is remote. Errors may exist in second-order 

reconstructions of specific plant associations (table 1), 

but this also is unlikely. Analyses of modern packrat 

middens show that plant species that are abundant or 

common in nearby vegetation are well-represented in the 

assemblages. Therefore, it is unlikely that a macrofossil 

assemblage would be interpreted as representing, say, a 

juniper-shrub woodland, when a pinyon-juniper woodland was actually present. Studies of modern middens 

thus far have failed to demonstrate consistent biases 

in foraging behavior of packrats that would invalidate 

the conclusions presented here. These paleoecological 

reconstructions usually are based on multiple macrofossil assemblages controlled by multiple radiocarbon dates. 

Non-representative assemblages may be sampled on 

occasion, but these would have little effect on paleoecological reconstructions based on many samples.

Diverse bioclimatic regions of the western United States 

provide a range of general analogs to the fossil records 

that are used to infer the nature of late Quaternary 

climates. Use of such analogs provides an effective paleoenvironmental tool, even though exact analogs between 

vegetation and environments of the late Pleistocene and

those of today probably do not exist (Hare, 1976; Birks, 

1981). Thus, the climate that existed at the time when 

xerophytic juniper woodland was widespread is assumed 

to have been more similar to that of current dry woodland than to that of less similar vegetation types in 

existence now. There are no logical alternatives to the 

assertion that, because the late Wisconsin vegetation of 

the Nevada Test Site region resembled current vegetation of northern Nevada, the past climate probably was 

more similar to the present climate of that area than any 

other area.

The fossil record provides evidence for various paleoecological phenomena which, in turn, are used to reconstruct different aspects of the past climate. Among the 

most important used in this study are values of the 

relative vertical displacement of individual species and 

the inferred absence of particular taxa from the region 

during the late Wisconsin.

ELEVATIONAL DISPLACEMENT

Estimates of minimum elevational displacement of 

limber pine and Utah juniper (table 8) are based on a 

large data set. Contributing environmental variables, 

such as aspect, exposure, and substrate, were considered 

in the calculation of displacement estimates (Spaulding, 

1981, p. 166-171). Wells (1977, p. 238) has cautioned that 

a vertical uncertainty of 100 m may exist in such estimates, 

because of the possibility of downslope transport of plant 

fragments from higher elevations. This is balanced, to 

some extent, by the probability that the lowest fossil 

record of a particular species does not reflect the lowest 

elevation that it attained. Neither consideration should 

seriously affect the validity of minimum estimates. For 

example, the three lowest fossil records of limber pine on 

calcareous substrate in the region are within 50-m elevation of each other and are from different sites (Spaulding, 

1981, table 35). At one of these sites, Basin Canyon-1 at 

an elevation of 1,635 m in the Sheep Range (Spaulding, 

1981, p. 136-140), limber pine is well represented in the 

macrofossil assemblages. It is improbable that these 

fossils represent downslope transport, because: (1) They 

are present in quantity; (2) the locality does not possess 

extreme topographic relief (Spaulding, 1981, fig. 20); 

and (3) two other middens from a different locality provide similar elevational records.

Occurrence of limber pine and Utah juniper far below 

their lowest modern populations is attributed to cooler 

summers during the late Wisconsin. These two taxa 

were chosen as indicator species of summer temperatures because they are the most xerophytic arboreal taxa 

in present subalpine (limber pine) and woodland (Utah 

juniper) vegetation. The assumption is made that their 

downward displacement primarily was due to increased
FUTURE CLIMATIC CHANGES 47

effective moisture caused by lowered temperatures, not 

by increased precipitation. The alternative that their 

expansion was due to a relative increase in rainfall is less 

likely. An increase in precipitation exceeding 50 percent 

of current amounts would have resulted in the expansion 

of mesophytic species (such as ponderosa pine or spruce) 

absent in the regional fossil record. Moreover, summer 

temperatures, rather than winter or average annual 

temperatures, are considered the critical variable controlling the lower limit of these trees because moisture 

deficits caused by higher temperatures occur during 

the summer.

There are no independent means available to test validity of lapse rates (table 8) used to convert estimates 

of minimum elevational displacement to estimates of 

changes in summer temperature (ATS ). However, it is 

perhaps less likely that actual Wisconsin-maximum lapse 

rates deviated significantly from values used here (table 

8. Indeed, values of ATS derived from the fossil records of 

Utah juniper and limber pine are close to those proposed 

by other workers using quite different methods (table 7).

NEGATIVE EVIDENCE

Absence of a species from a particular region is an 

important consideration in the study of present biogeographic and bioclimatic phenomena. Absence of shrubs 

intolerant of extremely low nocturnal temperatures, such 

as creosote bush, from the northern reaches of the Nevada 

Test Site is an indication of the severity of that region's 

winters (Beatley, 1974,1975). Unfortunately, it is impossible to demonstrate conclusively with the fossil record 

that a particular species was not present somewhere in 

the region. Despite comprehensive collections, the past 

vegetation of some habitats, such as alluvial fans, remains 

unknown. Some species may have been restricted to 

isolated sites with favorable microclimates during the 

Wisconsin. However, this would not invalidate the observation that the climate of that period did not favor those 

species. In the face of a large data base, it would be less 

reasonable to claim that these inferences are impermissible simply because they are based on negative evidence. 

However, negative inferences should be drawn from large 

data sets only and supported by other lines of evidence, 

and there is always the need for further replication.

Absence of creosote bush from the Wisconsin fossil 

record is attributed to winter temperatures that ranged 

below the limit of tolerance of that species. To this assumption can be added one qualification based on the possibility of competitive exclusion. Today certain habitats 

exist that are warm enough in the winter to support 

creosote bush; however, creosote bush is rare or absent. 

These sites are characterized by higher rainfall, and, in

the vicinity of the Nevada Test Site, such plant communities usually are dominated by blackbrush and, occasionally, 

species of Lycium ( Beatley, 1974, p. 255). Although competition between plants is difficult to demonstrate (Grime, 

1979), it is likely that creosote bush is absent from these 

communities because species such as blackbrush are 

more robust competitors in somewhat wetter habitats. 

Absence of creosote bush from the fossil record also may 

be due to such competitive exclusion, but it is considered 

unlikely. Many plant taxa that were common at lower 

elevations during the Wisconsin are typical of habitats 

that are too cold today for creosote bush. Plant species 

such as blackbrush are rare in the fossil record in the 

vicinity of the Nevada Test Site prior to about 12,000 

years ago.

RADIOCARBON DATING

Accurate radiocarbon dating of packrat middens is 

crucial to these paleoclimatic reconstructions. Mindful 

of past debates over methods in packrat-midden dating 

(Van Devender, 1977a; Wells, 1977), considerable care 

was taken in both the collection and description of ancient 

middens, and in the selection of samples for detailed 

analysis. As mentioned previously, less than 50 percent 

of the indurated middens located in the field were collected. 

Further examination and dissection of midden samples 

in the laboratory led to the rejection of others, on the 

basis of poor stratigraphic integrity and possible mixing 

of different-age plant debris. It is believed that many 

potential dating errors can be avoided by such rigorous 

sample selection. Reliability of these results is enhanced 

further by the use of time series from single sites. In a 

site-specific context, anomalous samples can be recognized more easily and subjected to further radiocarbon 

analyses. Therefore, there is little reason to suspect serious errors in the inferred vegetation associations or in 

the chronologies of vegetation and climate change presented here.

FUTURE CLIMATIC CHANGE

Various mechanisms operate on different scales of 

time (wavelengths) to affect climate. They range from 

diurnal solar forcing, with a frequency measured in hours, 

to epeiorogenic-orogenic events with a quasi-periodicity 

of, perhaps, between 10 to 100 million years (Mitchell, 

1976, p. 482-485). Based on current knowledge of climate 

dynamics and the geological record of past changes, 

major global climatic fluctuations likely will occur within the next 10,000 years. This is within the hazardous 

lifespan of radioactive wastes contemplated for storage at 

the Nevada Test Site. Although any prediction of the 

impact of future climatic change on the environment of
48 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

the Nevada Test Site is untestable (except indirectly by 

climate modeling) and speculative, it is nevertheless a 

critical aspect of overall assessment of site suitability.

Recent studies point to two separate phenomena as 

likely forcing mechanisms that may cause significant 

climatic change in the next 10,000 years. These are increases in global atmospheric carbon dioxide and changes in 

the elements of the Earth's orbit. Each is operating on a 

different time frequency. The former is anthropogenic 

and is occurring on periods of 100 years and less. Surfacetroposphere warming caused by increasing atmospheric 

carbon dioxide concentrations is rapid enough that the 

effects may be visible before the end of the century 

(Kellogg and Schware, 1981; Schlesinger, 1983). However, 

the combined effect of three orbital parameters that 

appear to drive the glacial-interglacial cycles [axial tilt, 

eccentricity, and deviation of the earth-sun distance 

(precession)] has demonstrable cycles of 10,000 to 100,000 

years. Because climate changes caused by astronomic 

modulation of solar insolation are of lower frequency, 

their immediate effects are not as apparent.

ATMOSPHERIC CARBON DIOXIDE

Likely consequences of increased atmospheric carbon 

dioxide have been identified using both general circulation and radiative-convective models of global climate 

(Ramanathan and Coakley, 1978; Manabe and Stouffer, 

1979). Most analyses are based on a projected doubling 

or quadrupling of carbon dioxide content of the atmosphere within the next 400 years. The result will be an 

increase in heating the surface-troposphere system by 

reflection of long-wave radiation from the Earth. The 

models of Ramanathan and others (1979, p. 4956) predict 

an increase in northern-hemispheric mean surface temperature of 3.2°C, assuming a doubling of atmospheric 

carbon dioxide. Manabe and Wetherald (1975, p. 9) note 

that a consequence of doubled atmospheric carbon dioxide concentration is the increase in heat energy available 

for evaporation. Hence, intensity of the "hydrologic cycle" 

(the entire ocean-land, evaporation-precipitation system 

in this case) would be enhanced, in their model, by about 

7 percent. A projected increase in rainfall also is implied 

by intensification of subtropical high-pressure systems 

by tropospheric warming (Manabe and Wetherald, 1975, 

p. 13). Schlesinger (1983) has recently reviewed model 

simulations of CO2-induced climate change.

In general, the projected relation of increased atmospheric temperatures to increased precipitation is analogous to paleoclimatic reconstructions that indicate an 

increased flow of tropical maritime air to land during the 

latest Wisconsin and middle Holocene. Increased temperatures during the early postglacial may have led to an 

enhanced summer monsoon in subtropical arid regions

(Kutzbach, 1981, p. 60; Bryson and Swain, 1981, table 

2). Another feature shared by both models, those used to 

predict the effect of carbon dioxide heating and those 

used to reconstruct the impact of increased insolation, is 

considerable seasonal and latitudinal variability in results 

(Ramanathan and others, 1979, p. 4956; Broecker and 

von Donk, 1970, p. 188; Kutzbach, 1981, p. 61).

The most important possible consequence of the increase 

in radiative heating of the surface-troposphere system is 

melting of the Antarctic ice cap (Etkins and Epstein, 

1982; Kukla and Gavin, 1981). Obviously, the resultant 

rise in sea level will have no direct effect on the environment of the Nevada Test Site. However, the anticipated 

rise in temperatures may well have a significant impact 

on the general climate of the Southwest and the Nevada 

Tbst Site in particular. Summer temperatures are expected to be higher than at present by a minimum of about 

3°C. Monsoonal circulation also will be enhanced. An 

increase in summer and fall precipitation by as much as 

50 to 100 percent over current amounts is not unrealistic 

(Bryson and Swain, 1981, table 2). This relative increase 

in precipitation is dependent on: (1) Intensity of the 

warming; (2) accuracy of current model-atmosphere 

projections; and (3) proximity of any given site to the 

source of maritime air. Because the Nevada Test Site is 

beyond the influence of monsoonal rains today, it is 

reasonable to anticipate less increase in annual rainfall 

here (perhaps no more than 50 percent) than in areas 

farther south and east.

THE NEXT ICE AGE

The relationship between variations in the Earth's 

orbital configuration and the record of ice-sheet contraction 

and expansion is well documented (Imbrie and Imbrie,

1980). The astronomical theory of climate states that 

modulation of solar radiation by changes in precession, 

obliquity, and eccentricity is the principal cause of Pleistocene 

ice ages. In particular, the Milankovitch model (Imbrie 

and Imbrie, 1980) relates orbitally controlled decreases 

in northern latitude summer insolation to the descent of 

snowline and development of perennial snowfields (Adam, 

1975; Johnson and McClure, 1976). Several feedback 

mechanisms then would enhance their growth to continental 

ice sheets (Ruddiman and Mclntyre, 1981, p. 617-618). In 

a like manner, deglaciations such as that which occurred 

at the end of the Wisconsin are associated with peaks in 

summer insolation in the northern hemisphere (Broecker 

and van Donk, 1970, fig. 10; Ruddiman and Mclntyre,

1981).

Given the inherent predictability of orbital parameters 

affecting incident solar radiation, and an adequate statistical 

model relating these variations to continental glaciation, 

future major global climate change can be predicted.
SUMMARY AND CONCLUSIONS 49

Broecker and van Donk (1970, p. 194) were among the 

first to observe that, based on their analyses, "*** the 

next 50,000 years should see unusually rapid expansion 

of continental ice sheets." This agrees with the subsequent 

work of Berger (1978, fig. 4e) that presents variations in 

astronomical parameters and isolation curves for the 

next 250,000 years. A minimum in northern-hemispheric 

summer insolation will occur within the next 10,000 

years. That this may result in initiation of a new glacial 

age is seen in the model projections of Imbrie and Imbrie 

(1980, figs. 7 and 8). Their nonlinear model was constructed 

to simulate global climatic response to orbital variations, 

as observed in the deep-sea core record of ^O/^O variations. 

After adjustment and tuning, good agreement was reached 

between the model's response to orbital input and the 

actual oxygen-isotope record of continental glaciation 

over the last 250,000 years (fig. 25). The model's response 

to future orbital input is seen as a continuation of the 

cooling trend that has been underway for about the last 

6,000 years, culminating in a glacial maximum in about 

60,000 A.P. (years after present). Another, less-pronounced 

stade is evident in the model output at about 23,000 A.P. 

(fig. 25). The gradual excursion of global climate to 

maximum stadial conditions, followed by relatively abrupt 

deglaciation after 60,000 A.P., is consistent with the 

"sawtooth" character of the primary glacial-interglacial 

cycle (Broecker and van Donk, 1970; Ruddiman and 

Mclntyre, 1981, p. 625).

In this context, it is useful to reaffirm the statement 

that the Wisconsin maximum at about 18,000 B.P. represents 

a maximum departure from current interglacial conditions. 

The magnitude of that stadial episode generally is 

representative of what may be expected during the next 

glacial maximum, based on oxygen-isotope record estimates 

of global ice volume. The last four glacial maxima, during 

isotope stages 2, 6, 8, and 10, all appear to have been of 

comparable magnitude, as is the projected maximum at 

about 60,000 A.P. The implication that there is an 

approximately equivalent limit to each glacial buildup, 

attained immediately preceding each deglaciation, is supported 

by studies of the mechanisms of continental glaciation 

(Ruddiman and Mclntyre, 1981; Broecker and van Donk, 

1970).

The combined potential impact of changing atmospheric 

carbon dioxide concentrations and orbitally induced solarinsolation variations can be summarized as follows: A 

brief but pronounced "super-interglacial" may well occur 

within the next 500 years, followed by a continued trend 

to the next glacial age, reaching a maximum in about 

60,000 years. The relative duration of the former event 

may be quite brief, perhaps no more than a short-lived 

perturbation in the progression of glacial ages. While 

more modeling is needed, it is doubtful that the carbon

Model output 801 pO 

50

-100 -50 0 50 100 150 200 

THOUSANDS OF YEARS BEFORE PRESENT

250

From Imbrie and Imbrie, 1980 Copyright 

1980 by the American Association for the 

Advancement of Science

FIGURE 25. Inferred past changes in global ice volume and modeled 

future trends (from Imbrie and Imbrie, 1980, p. 948; copyright 1980 

by the American Association for the Advancement of Science); orbitally 

induced irradiation variations for July at lat 65° N. are presented in 

^4; resultant output of Imbrie and Imbrie's(1980, fig. 7) optimum climatic 

response model is shown in 5; fluctuations in world ice-sheet volume 

are recorded in oxygen-isotope variations in two equatorial deep-sea 

cores Rcll -120 and V28-238 (C and D).

dioxide induced warming of the global climate will permanently 

affect the orbitally forced cycle of glacial ages.

SUMMARY AND CONCLUSIONS

Packrat middens provide an elaborate history of the 

late Quaternary environments of the Nevada Test Site. 

Radiocarbon-dated plant-macrofossil assemblages allow 

reconstruction of both the past vegetation and chronology 

of its change over the last 45,000 radiocarbon years. 

These, in turn, are the basis of models of local and 

regional paleoclimate. Nearly 100 individually dated 

macrofossil assemblages from the northern Mojave Desert, 

spanning 1,600 m of vertical relief, allow detailed 

characterization of the climatic stability of this region in 

general and the Nevada Test Site in particular.

A limited number of studies in western North America 

present paleoenvironmental reconstructions defined by 

specific climatic parameters (table 8). Because of the 

uncertainties inherent in such investigations (Hare, 1976; 

Birks, 1981; see also the fifth chapter of this report), 

many analyses resort to generalized conclusions. However, 

terms such as "equable," "pluvial," and "mild" are of 

limited use unless specified by a range of absolute values.
50 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 10. Summary of estimates of late Quaternary climate for the Nevada Test Site

and vicinity

[ATW, estimated changes in °C (degrees Celsius) of average winter temperature; ATg , estimated changes in °C of average 

summer temperature; A Ta, estimated changes in ° C of average annual temperature; % (percent) Pg, estimated percent 

changes in average summer precipitation relative to current amounts; %PW, estimated percent changes in average 

winter precipitation relative to current amounts; %Pa, estimated percent changes in average annual precipitation 

relative to current amounts; B.P., radiocarbon years before present]

Time

(B.P.I

45,000

38,700

37,800

30,000

18,000

10,000

*TW

-2 to -3

 

 

 

1-6

-lto-2

ATS

___

 

 

 

-7 to -8

+ lto+2

AT a

-lto-3

-lto-2

-5

-3 to -6

-6 to -7

0

%PS

1/-60

-40

 

 

-40 to -50

2 -50

%PW

+ 20

+ 25 to +50

 

 

+ 60 to +70

0

%pa

0

+ 10 to +20

+ 20

+ 10 to +25

+ 30 to +40

+ 10 to +20

1 Minimum estimate.

2 Maximum estimate.

Only explicit estimates can be used to model response of 

hydrologic systems to climatic change, and to test alternative 

models of past climates. Quantitative paleoclimatic estimates 

in this study (table 10) do incorporate a number of uncertainties 

that have been discussed previously. Therefore, the climatic 

reconstructions are expressed as either a range of values 

or as a limiting (maximum or minimum) parameter.

During the Wisconsin, plant communities differed in 

both distribution and composition from plant communities 

of today. Environmental gradients governing altitudinal 

segregation of plant species into vegetation zones were 

altered, and a different scheme of zonation was the result 

(figs. 14,22). In a region that now supports desert vegetation, 

Utah juniper woodland extended from near local base 

level up to a transition with limber pine woodland. Great 

Basin Desert plants, such as sagebrush, shadscale, and 

rabbitbush, were common in these woodlands. Although 

there is no evidence for vegetation without trees prior to 

about 15,000 years ago, steppe-shrub communities may 

have existed on alluvial fans unsampled by the midden 

method (Thompson and Mead, 1982) and on isolated, 

xeric habitats. There also is no evidence for glacial-age 

temperate-montane forest at higher elevations. Based on 

the macrofossil data, only two Wisconsin vegetation 

zones can be identified: Xerophytic pygmy-conifer woodland 

at low elevations (less than 1,800 m) and subalpineconifer woodland above that. This contrasts with the 

present sequence of vegetation zonation from desertscrub 

to, first, pygmy-conifer woodland; then, montane forest; 

and, finally, subalpine woodland (fig. 14). Not only was 

vegetation zonation during the Wisconsin simpler than 

today's, but plant associations also appear to have been 

less diverse. Many Mojave Desert species are rare or 

missing from the macrofossil record, as are many woodland 

and forest plants presently found in mild, moist environments.

The local chronology of climatic change is consistent 

with the global record of transitions from middle to late

Wisconsin and from late Wisconsin to Holocene. Records 

of middle Wisconsin interstadial (about 45,000 to 23,000 

years ago) environments document xerophytic juniper 

shrub associations at most sites. This was a time of 

reduced summer rainfall and accentuated winter precipitation. 

Average annual precipitation during the most mesic phase 

was perhaps as much as 20 percent above current amounts. 

The available record indicates that the warmest part of 

the middle Wisconsin was between about 45,000 and 

39,000 years ago, with average annual temperatures perhaps 

only 1° to 3°C below current values (table 10). Temperatures 

declined in the last 10,000 to 15,000 years of the middle 

Wisconsin interstadial, although there appear to have 

been marked reversals characterized by higher temperatures. 

The descent of subalpine woodland to at least an elevation 

of 1,800 m in the Eleana and Sheep Ranges marks the 

beginning of the late Wisconsin stade (about 23,000 to 

10,000 years ago) in this region. In the Specter Range, a 

vegetation turnover from juniper-shrub to pinyon-juniper 

woodland by about 19,000 B.P. may be evidence of the 

Wisconsin maximum. The northern Mojave fossil record 

provides no evidence for either equable temperatures 

(cool summers and warm winters) or a pluvial precipitation 

regime (annual rainfall exceeding 50 percent of current 

amounts). Late Wisconsin vegetation of the Nevada 

Test Site and vicinity was dominated by subalpine, dry 

woodland, and steppe species; it lacked frost-sensitive 

taxa and was of apparent lower diversity. A cold, continental 

climate with winter temperatures at least 6°C below 

those of today is indicated. Summer temperatures were 

depressed at least an equivalent amount, and average 

annual temperatures were perhaps 6° to 7°C lower than 

at present (table 10). There was a distinct lack of summer 

rain and a relative increase in winter precipitation by as 

much as 70 percent above current values. However, the 

estimated increase in average annual precipitation was, 

at the most, about 40 percent above present amounts 

(table 10).
SUMMARY AND CONCLUSIONS 51

This reconstruction of late Wisconsin climate in the 

northern Mojave Desert differs to some extent with 

reconstructions proposed for the monsoonal Sonoran 

and Chihuahuan Deserts to the south and east. Macrofossil 

evidence from that region has been interpreted as indicating 

both a pluvial precipitation regime and equable temperatures 

(Van Devender, 1973, table 3; Van Devender and Spaulding, 

1979, p. 708; Wells, 1979, p. 311). Contrasts between 

inferred paleoclimates in the vicinity of the Nevada Test 

Site and those to the southeast may be accounted for by 

regional climatic variations. The relative increase in late 

Wisconsin precipitation in the Sonoran and Chihuahuan 

Deserts apparently was greater than in the Mojave Desert. 

Two factors can account for this. First, an enhanced 

zonal (west to east) flow of upper-level air, coupled with 

southerly displacement of winter storm tracks, may have 

occurred as a consequence of a steepened arctic-equator 

temperature gradient during the late Wisconsin. The 

resultant increase in the frequency of Pacific-type winter 

storms is postulated to have been most pronounced south 

of lat 36° N. To the north, the relative increase in winter 

precipitation probably was less due to the barrier to 

easterly maritime air flow posed by the Sierra Nevada 

(fig. 1) (Van Devender and Spaulding, 1979, p. 708). A 

second factor is attenuation of the present southeastnorthwest cline of summer precipitation during the late 

Wisconsin. The northern Mojave, which today receives 

roughly 25 percent of its annual increment of precipitation 

during the summer, may have received practically no 

warm-season rainfall during the late Wisconsin. Farther 

to the south and east, there is evidence for some summer 

rainfall (Van Devender, 1973, p. 88), although it probably 

was less than today's amounts (Van Devender and Wiseman, 

1977, p. 21).

The relative decline in full-glacial (about 18,000 B.P.) 

temperatures proposed for the Nevada Test Site area, in 

the northern Mojave Desert (table 10), is roughly twice 

that estimated for sites in the current Sonoran Desert 

(Van Devender, 1973, table 3). This may be due, in part, 

to the pluvial environment and more southerly position 

of the latter region. Increased relative humidity and 

cloud cover would lead to relatively warm nocturnal 

temperatures. However, the evidence for very mild lateglacial winters in the monsoonal Southwest is equivocal. 

For example, the presence of chuckwalla (Sauromalus 

obesus) and desert tortoise (Gopherus agassizi) in the 

late Wisconsin woodlands of the Sonoran and Chihuahuan 

Deserts has been a basis for inferring a negligible decline 

in winter temperature (Van Devender and others, 1977, 

p. 61; Van Devender and Mead, 1978, p. 474). However, 

these animal species today occur as far north as Beatty, 

Nevada, where the mean January temperature is about 

4.5°C (table 4). Their presence in late Wisconsin woodlands 

in the vicinity of Ttocson, Arizona (mean January temperature

of about 9.8°C) would be consistent with a winter temperature decline of at least 5°C. Winter temperatures at 

least 5°C lower than at present also would explain the 

absence from the fossil record of many frost-sensitive 

subtropical plants characterizing the present Sonoran 

Desert (Van Devender, 1976, p. 65; Spaulding and 

others, 1983).

Vegetation change marking the end of the late Wisconsin 

was underway by at least 14,000 years ago in the northern 

Mojave Desert. At higher altitudes, the Wisconsin to 

Holocene transition (about 12,000 to 8,000 B.P.) is seen 

as the demise of subalpine conifer associations and inception 

of the present pinyon-juniper woodland and ponderosa 

pine forest. Below an elevation of about 1,800 m, the 

transition was characterized by extirpation of woodland 

plants and development of desertscrub vegetation. This 

major environmental change was both space- and timetransgressive (fig. 14). At sensitive sites, postglacial 

vegetation conditions were attained before about 12,000 

years ago and, at more "complacent" sites, after 9,500 

B.P. Widespread desert vegetation developed at least 

2,000 years earlier in the Mojave than in most areas of 

the Sonoran and Chihuahuan Deserts.

Climatic change of the Pleistocene to Holocene transition 

involved apparent concurrent increases in annual temperatures 

and summer rain, as well as a decline in winter precipitation. 

From about 11,000 to 10,000 years ago summer precipitation 

may have been as much as 50 percent higher than at 

present, although annual amounts in the northern Mojave 

probably were within 20 percent of current values (table 

10). Late persistence of woodlands at low elevations in 

the Sonoran and Chihuahuan Deserts (Van Devender, 

1977b) probably was due to this period of enhanced 

monsoonal precipitation. Annual range of temperatures 

at this time probably was somewhat greater than at 

present, with cooler winters and warmer summers. Winter 

temperatures increased into the Holocene; the middle 

Holocene (between 8,000 and 3,000 B.P.) may have been 

characterized by average annual temperatures 1° to 2°C 

above present values. Summer precipitation probably 

exceeded present amounts until between 3,000 and 4,000 

years ago.

Gradually declining temperatures have typified the 

last 4,000 to 6,000 years. It is likely that, at present, this 

trend is being reversed by heating caused by increasing 

atmospheric carbon dioxide concentrations. Temperatures 

in excess of 3°C above present values and increased 

rainfall may occur within the next 500 years. However, 

this anticipated "super-interglacial" interval is not expected 

to permanently reverse the orbitally driven trend toward 

the next ice age. If current theoretical models are adequate, 

then a new glacial age is to be expected within the next 

10,000 years.
52 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

REFERENCES CITED

Adam, D. P., 1975, Ice ages and the thermal equilibrium of the

earth, II: Quaternary Research, v. 5, p. 161-172. 

Antevs, Ernst, 1948, The Great Basin, with emphasis on glacial

and post-glacial times: Bulletin of the University of Utah,

v. 38, p. 1-24. 

 1952, Cenozoic climates of the Great Basin: Geologisches

Rundschau, v. 40, p. 94-108. 

.1954, Climate of New Mexico during the last glacio-pluvial:

Journal of Geology, v. 62, no. 2, p. 182-191. 

Bacchuber, F. W., and McClellan, W. A., 1977, Paleoecology of

marine foraminifera in pluvial Estancia Valley, central New

Mexico: Quaternary Research, v. 7, p. 254-267. 

Barnosky, C. W., 1981, A record of late Quaternary vegetation

from Davis Lake, southern Puget Lowland, Washington:

Quaternary Research, v. 16, p. 221-239. 

Beatley, J. C., 1974, Effects of rainfall and temperature on the

distribution and behavior of Larrea tridentata (creosote bush)

in the Mojave Desert of Nevada: Ecology, v. 55, p. 245-261. 

____1975, Climates and vegetation pattern across the Mojave/

Great Basin Desert transition of southern Nevada: American

Midland Naturalist, v. 93, p. 53-70. 

 1976, Vascular plants of the Nevada Test Site and centralsouthern Nevada: National Technical Information Service 

Report TID-26881, 308 p.

Bell, F. C., 1979, Precipitation, in Goodall, D. W., and Perry. R. A., 

eds.,Arid-land ecosystems Structure, function, and management: New York, Cambridge University Press, p. 373-392.

Berger, A. L., 1978, Long-term variations of caloric insolation 

resulting from the Earth's orbital elements: Quaternary Research, v. 9, p. 139-167.

Berggren, W. A., and others, 1980, Towards a Quaternary time 

scale: Quaternary Research, v. 13, p. 277-302.

Betancourt, J. L., and Van Devender, T. R., 1981, Holocene vegetation in Chaco Canyon, New Mexico: Science, v. 214, p. 

656-658.

Billings, W. D., 1949, The shadscale vegetation zone of Nevada 

and eastern California in relation to climate and soils: American Midland Naturalist, v. 42, p. 87-109.

Birks, H. J. B., 1981, The use of pollen analysis in the reconstruction of past climates A review, in Wigley, T. M. L., and 

others, eds., Climate and history: New York, Cambridge 

University Press, p. 111-138.

Bleich, V. C., and Schwartz, O. A., 1975, Observations on the 

home range of the desert woodrat, Neotoma lepida intermedia: Journal of Mammalogy, v. 56, p. 518-519.

Bowen, D. Q., 1978, Quaternary geology: New York, Pergamon 

Press, 221 p.

Brakenridge, G. R., 1978, Evidence for a cold, dry full-glacial 

climate in the American Southwest: Quaternary Research, 

v. 9, p. 22-40.

Bredehoeft, J. D., and others, 1978, Geologic disposal of high-level 

radioactive wastes Earth-science perspectives: U.S. Geological Survey Circular 779, 15 p.

Broecker, W. S., and Orr, P. C., 1958, Radiocarbon chronology of 

Lake Lahontan and Lake Bonneville: Geological Society of 

America Bulletin, v. 69, no. 8, p. 1009-1032.

Broecker, W. S., and van Donk, Jan, 1970, Insolation changes, 

ice volumes, and the O 18 record in deep-sea cores: Reviews of 

Geophysics and Space Physics, v. 8, no. 1, p. 169-198.

Brown, D. E., Lowe, C. H., and Pase, C. P., 1979, A digitized classification system for the biotic communities of North America,

with community (series) and association examples for the 

Southwest: Journal of the Arizona Academy of Science, v. 14, 

supplement 1, 16 p.

Bryson, R. A., and Hare, F. K., eds., 1974, Climates of North 

America: New York, American Elsevier Publishing Company, 

420 p.

Bryson, R. A., and Lowry, W. D., 1955, The synoptic climatology 

of the Arizona summer precipitation singularity: Bulletin of 

the American Meteorological Society, v. 36, p. 329-339.

Bryson, R. A., and Swain, A. M., 1981, Holocene variations of 

monsoon rainfall in Rajasthan: Quaternary Research, v. 16, 

p. 135-145.

CLIMAP (Climate: Long-range Investigation Mapping and Prediction) Project Members, 1976, The surface of the ice-age 

Earth: Science, v. 191, p. 1131-1137.

Cole, K. L., 1981, Late Quaternary environments in the eastern 

Grand Canyon, vegetation gradients over the last 25,000 

years: Tucson, University of Arizona, Ph.D. dissertation, 

170 p.

____1982, Late Quaternary zonation of vegetation in the eastern 

Grand Canyon: Science, v. 217, p. 1141-1145.

Court, A., 1974, The climate of the conterminous United States, 

in Bryson, R. A., and Hare, K. F., eds., Climates of North 

America: New York, American Elsevier Publishing Company, 

p. 193-261.

Cranford, J. A., 1977, Home range and habitat utilization by 

Neotoma fuscipes as determined by radiotelemetry: Journal 

of Mammalogy, v. 58, p. 165-172.

Cronquist, Arthur, and others, 1972, Intermountain flora, v. 1: 

New York, Hafner, 270 p.

Dansgaard, W., and others, 1971, Climatic record revealed by the 

Camp Century ice core, in Turekian, K.K., ed., The late 

Cenozoic glacial ages: New Haven, Yale University Press, 

p. 37-56.

Davis, M. B., 1981, Quaternary history and the stability of forest 

communities, in West, D. C., and Shugart, H. H., eds.. Forest 

succession Concepts and application: New York, SpringerVerlag, p. 132-151.

Deevey, E. S., Jr., and Flint, R. F., 1957, Postglacial hypsithermal 

interval: Science, v. 125, p. 182-184.

Dreimanis, Alexis, and Raukas, A., 1975, Did Middle Wisconsin, 

Middle Weichselian, and their equivalents represent an interglacial or an interstadial complex in the northern hemisphere?, 

in Suggate, R. P., and Cresswell, M. M., eds.. Quaternary 

studies: Wellington, Transactions of the Royal Society of 

New Zealand, p. 109-120.

Environmental Data Service, 1961-78, Climatological data, summaries: U.S. Department of Commerce, National Oceanic 

and Atmospheric Administration (published annually).

Etkins, Robert, and Epstein, E. S., 1982, The rise of global mean 

sea level as an indication of climate change: Science, v. 215, 

p.287-289.

Fenneman, N. M., 1931, Physiography of the western United States; 

New York, McGraw-Hill, 534 p.

Finley, R. B., Jr., 1958, The woodrats of Colorado Distribution 

and ecology: University of Kansas Publications in Natural 

History, v. 10, p. 213-552.

Flint, R. F., 1971, Glacial and Quaternary geology: New York, 

John Wiley, 802 p.

Galloway, R. W., 1970, The full-glacial climate in the southwestern 

United States: Annals of the Association of American Geographers, v. 60, no. 2, p. 245-256.

Gates, W. L., 1976, Modeling the ice-age climate: Science, v. 191, 

p. 1138-1144.
REFERENCES CITED 53

Grayson, D. K., 1979, On the quantification of vertebrate archaeofaunas, in Sheets, P. D., and Grayson, D. K., eds.. Advances 

in archaeological method and theory, v. 2: New York, Academic 

Press, p. 199-237.

Grime, J. P., 1979, Plant strategies and vegetation processes: 

New York, John Wiley, 222 p.

Hales, J. E., Jr., 1974, Southwestern United States summer monsoon source Gulf of Mexico or Pacific Ocean?: Journal of 

Applied Meteorology, v. 13, p. 331-342.

Hare, K. L., 1976, Late Pleistocene and Holocene climates Some 

persistent problems: Quaternary Research, v. 6, p. 507-518.

Haynes, C. V., Jr., 1967, Quaternary geology of the Tule Springs 

area, Clark County, Nevada, in Wormington, H. M., and 

Ellis, Dorothy, eds.. Pleistocene studies in southern Nevada: 

Nevada State Museum Anthropological Papers 13, p. 15-104.

Heusser, C. J., 1977, Quaternary palynology of the Pacific slope 

of Washington: Quaternary Research, v. 8, p. 282-306.

Holmgren, A. H., and Reveal, J. L., 1966, Checklist of the vascular 

plants of the Intermountain Region: U.S. Forest Service 

Research Paper INT-32, 160 p.

Houghton, J. G., Sakamoto, C. M., and Gifford, R. O., 1975, Nevada's 

weather and climate: Nevada Bureau of Mines Special Publication 2, 78 p.

Huning, J. R., 1978, A characterization of the climate of the California desert: Riverside, Desert Planning Staff, California 

Bureau of Land Management unpublished report, 220 p.

Imbrie, John, and Imbrie, J. Z., 1980, Modeling the climatic response 

to orbital variations: Science, v. 207, p. 943-953.

Interagency Review Group on Nuclear Waste Management, 1978, 

Report to the President: National Technical Information Service TID-29442, 149 p.

Johnson, R. G., and McClure, B. T, 1976, A model for northern 

hemispheric continental ice sheet variation: Quaternary Research, v. 6, p. 325-354.

Kellogg, W. W., and Schware, R., 1981, Climate change and society: 

Boulder, Colo., Westview Press, 178 p.

Kukla, George and Gavin, J., 1981, Summer ice and carbon dioxide: 

Science, v. 214, p. 497-503.

Kutzbach, J. E., 1981, Monsoon climate of the early Holocene 

Climate experiment with the Earth's orbital parameters for 

9,000 years ago: Science, v. 214, p. 59-61.

Kutzbach, J. E., and Otto-Bleisner, B. L., 1982, The sensitivity 

of the African-Asian monsoonal climate to orbital parameter 

changes for 9000 years B. P. in a low-resolution general circulation model: Journal of the Atmospheric Sciences, v. 39, 

p. 1177-1188.

La Marche, V. C., Jr., 1973, Holocene climatic variations inferred 

from treeline fluctuations in the White Mountains, California: 

Quaternary Research, v. 3, p. 632-660.

Langford, A. N., and Buell, M. F., 1968, Integration, identity, and 

stability in the plant association: Advances in Ecological 

Research, v. 6, p. 83-135.

Leopold, L. B., 1951, Pleistocene climate in New Mexico: American 

Journal of Science, v. 249, p. 152-168.

Little, E. L., Jr., 1976, Minor western hardwoods, in Atlas of 

United States trees, v. 3: U.S. Forest Service Miscellaneous 

Publication 1314, 210 maps.

Long, Austin, and Rippeteau, Bruce, 1974, Testing contemporaneity and averaging radiocarbon dates: American Antiquity, 

v. 39, p. 205-215.

Major, Jack, 1977, California climate in relation to vegetation 

in Barbour, M.G., and Major, Jack, eds., Terrestrial vegetation of California: New York, John Wiley, p. 11-74.

Manabe, Syukuro, and Stouffer, R. J., 1979, A CO-climate sensitivity study with a mathematical model of the global climate:

Nature, v. 282, p. 491-493.

Manabe, Syukuro, and Wetherald, R. T, 1975, The effects of doubling the CO2-concentration on the climate of a general circulation model: Journal of Atmospheric Sciences, v. 32, p. 3-15.

Martin, P. S., 1963, The last 10,000 years A fossil pollen record 

of the American Southwest: Tucson, University of Arizona 

Press, 87 p.

Martin, P. S., and Mehringer, P. J., Jr., 1965, Pleistocene pollen 

analysis and biogeography of the Southwest, in Wright, 

H. E., Jr., and Frey, D. G., eds., The Quaternary of the United 

States: Princeton, N. J., Princeton University Press, p. 433- 

451.

Mead, J. I., and Phillips, A. M., Ill, 1981, The late Pleistocene 

and Holocene fauna and flora of Vulture Cave, Grand Canyon, 

Arizona: Southwestern Naturalist, v. 26, p. 257-288.

Mead, J. I., Thompson, R. S., and Long, Austin, 1978, Arizona 

radiocarbon dates IX-carbon isotope dating of packrat middens: Radiocarbon, v. 20, p. 171-191.

Mehringer, P. J., Jr., 1965, Late Pleistocene vegetation in the Mojave 

Desert of southern Nevada: Journal of the Arizona Academy 

of Science, v. 3, p. 172-188.

____ 1967, Pollen analysis of the Tule Springs site, Nevada, 

in Wormington, H. M., and Ellis, D., eds., Pleistocene studies 

in southern Nevada: Nevada State Museum Anthropological 

Papers, v. 13, p. 129-200.

Mehringer, P. J., Jr., Martin, P. S., and Haynes, C. V., Jr., 1967, 

Murray Springs, a mid-postglacial pollen record from southern 

Arizona: American Journal of Science, v. 265, p. 786-797.

Mehringer, P. J., Jr., and Warren, C. N., 1976, Marsh, dune, and 

archaeological chronology, Ash Meadows, Amargosa Desert, 

Nevada, in Elston, Ronald, ed., Holocene enviromental change 

in the Great Basin: Nevada Archaeological Survey Research 

Paper 6, p. 120-150.

Mifflin, M. D., and Wheat, M. M., 1979, Pluvial lakes and estimated pluvial climates of Nevada: Nevada Bureau of Mines 

and Geology Bulletin 94, 57 p.

Mitchell, J. M., 1976, An overview of climatic variability and its 

causative mechanisms: Quaternary Research, v. 6, p. 481-494.

Mitchell, V. L., 1976, The regionalization of climate in the western 

United States: Journal of Applied Meteorology, v. 15, p. 920- 

927.

Mooney, H. A., St. Andre, G., and Wright, R. D., 1962, Alpine 

and subalpine vegetation patterns in the White Mountains 

of California: American Midland Naturalist, v. 68, p. 275-293.

Morrison, R. B., 1965, Quaternary geology of the Great Basin, in 

Wright, H. E., and Frey, D. G., eds.. The Quaternary of the 

United States: Princeton, N. J., Princeton University Press, 

p. 265-285.

Morrison, R. B., and Frye, J. C., 1965, Correlation of the middle 

and late Quaternary successions of the Lake Lahontan, Lake 

Bonneville, Rocky Mountain (Wasatch Range), southern Great 

Plains, and eastern Midwest areas: Nevada Bureau of Mines 

Report 9, 45 p.

Mueller-Dombois, Dieter, and Ellenberg, Heinz, 1974, Aims and 

methods of vegetation ecology: New York, John Wiley, 547 p.

Munz, P. A., 1974, A flora of southern California: Berkeley, University of California Press, 1,086 p.

Peng, T. H., Goddard, J. G., and Broecker, W. S., 1978, A direct 

comparison of 14C and 230Th ages at Searles Lake, California: 

Quaternary Research, v. 9, p. 319-329.

Phillips, A. M., Ill, 1977, Packrats, plants, and the Pleistocene
54 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

in the lower Grand Canyon: Tucson, University of Arizona, 

Ph. D. dissertation, 123 p.

Porter, S. C., 1971, Fluctuations of late Pleistocene alpine glaciers 

in western North America, in Turekian, K. K., ed., The late 

Cenozoic glacial ages: New Haven, Yale University Press, p. 

307-330.

Prell, W. L., and Hays, J. D., 1976, late Pleistocene faunal and 

temperature patterns of the Columbia Basin, Carribean Sea, 

in Cline, R. M., and Hays, J. D., eds., Investigations of late 

Quaternary paleoceanography and paleoclimatology: Geological Society of America Memoir 145, p. 201-220.

Ramanathan, V., and Coakley, J. A., Jr., 1978, Climate modeling 

through radiative-convective models: Reviews of Geophysics 

and Space Physics, v. 16, p. 465-489.

Ramanathan, V., Lian, M. S., and Cess, R. D., 1979, Increased 

atmospheric CO2-zonal and seasonal estimates of the effects 

of the radiation energy balance and surface temperature: 

Journal of Geophysical Research, v. 86, p. 4949-4957.

Raun, G. G., 1966, A population of Woodrats (Neotoma micropus) 

in southern Texas: Bulletin of the Texas Memorial Museum, 

v. 11, 62 p.

Reeves, C. C., Jr., 1966, Pleistocene climate of the Llano Estacado, 

Pt. 2: Journal of Geology, v. 74, no. 5, Pt. 1, p. 642-647.

Robinson, S. W., 1979, Radiocarbon dating at the U.S. Geological 

Survey, Menlo Park, California in Berger, Rainer, and Suess, 

H. W., eds., Radiocarbon dating: Berkeley, University of California Press, p. 268-273.

Ruddiman, W. F., and Mclntyre, A., 1981, Oceanic mechanisms 

for amplification of the 23,000-year ice volume cycle: Science, 

v. 212, p. 617-627.

Schlesinger, M. E., 1983, A review of climate model simulations of 

CO2 -induced climatic change: Corvallis, Ore., Oregon State 

University, Climate Research Institute Report no. 41, 135 p.

Schumm, S. A., 1965, Quaternary paleohydrology, in Wright, H. E., 

Jr., and Frey, D. G., eds., The Quaternary of the United States: 

Princeton, N. J., Princeton University Press, p. 783-794.

Sellers, W. D., and Hill, R. H., eds., 1974, Arizona climate 1931- 

1972: Tucson, University of Arizona Press, 616 p.

Sergin, V. Ya., 1980, Origin and mechanism of large-scale climatic 

oscillations: Science, v. 209, p. 1477-1482.

Shackleton, N. J., and Opdyke, N. D., 1973, Oxygen isotope and 

paleomagnetic stratigraphy of equatorial Pacific core V28- 

238 Oxygen isotope temperatures and ice volumes on a 105 

year and 106 year scale: Quaternary Research, v. 3, p. 39-55.

Smith, G. I., 1979, Subsurface stratigraphy and geochemistry of 

late Quaternary evaporites, Searles Lake, California: U.S. 

Geological Survey Professional Paper 1043, 130 p.

Snyder, C. T., Hardman, George, and Zdenek, F. F., 1964, Pleistocene lakes in the Great Basin: U.S. Geological Survey Miscellaneous Geological Investigations Map 1-416.

Snyder, C. T., and Langbein, W. B., 1962, The Pleistocene lake in 

Spring Valley, Nevada, and its climatic implications: Journal 

of Geophysical Research, v. 67, no. 6, p. 2385-2394.

Sorensen, T., 1948, A method of establishing groups of equal 

amplitude in plant sociology based on similarity of species 

content: Det Kongress Danske Videnske, Selskab Biologica 

Skrifter, v. 5, p. 1-34.

Spaulding, W. G., 1976, Late Quaternary vegetation change in the 

Sheep Range, Clark County, Nevada: American Quaternary 

Association Abstracts, p. 160-161.

 1977, Late Quaternary vegetational change in the Sheep 

Range, southern Nevada: Journal of the Arizona Academy of 

Science, v. 12, p. 3-8.

__ 1980, The presettlement vegetation of the California Desert: 

Riverside, Desert Planning Staff, California Bureau of Land 

Management unpublished report, 97 p.

__ 1981, The late Quaternary vegetation of a southern Nevada 

mountain range: Tucson, University of Arizona, Ph. D. dissertation, 271 p.

__ 1983, Late Wisconsin macrofossil records of desert vegetation in the American southwest: Quaternary Research, v. 19, 

p. 256-264.

Spaulding, W. G., Leopold, E. B., and Van Devender, T. R., 1983, 

Late Wisconsin paleoecology of the American southwest, in 

Porter, S. C., ed., The late Pleistocene of the United States: 

Minneapolis, University of Minnesota Press, p. 259-293.

Stones, R. C., and Hayward, C. L., 1968, Natural history of the 

desert woodrat, Neotoma lepida: American Midland Naturalist, v. 80, p. 458-476.

Stuiver, Minze, and Smith, G. I., 1979, Radiocarbon ages of stratigraphic units, in Smith, G. I., Subsurface stratigraphy and 

geochemistry of late Quaternary evaporites, Searles Lake, California: U.S. Geological Survey Professional Paper 1043, p. 

68-75.

Thompson, R. S., and Mead, J. I., 1982, Late Quaternary environments and biogeography in the Great Basin: Quaternary 

Research, v. 17, p. 39-55.

U.S. Weather Bureau, 1965, Climatography of the United States, 

supplement for 1931 through 1952 (no. 11-22) and supplement 

for 1951 through 1960 (no. 86-22): U.S. Department of Commerce, National Oceanic and Atmospheric Administration.

Van Devender, T. R., 1973, Late Pleistocene plants and animals 

of the Sonoran Desert, a survey of ancient packrat middens 

in southwestern Arizona: Tucson, University of Arizona, 

Ph. D. dissertation, 179 p.

____ 1976, the biota of hot deserts of North America during 

the last glaciation The packrat midden record: American 

Quaternary Association Abstracts, p. 62-67.

____ 1977a, Comment on Macrofossil analysis of woodrat 

(Neotoma) middens as a key to the Quaternary vegetational 

history of arid North America by P. V. Wells: Quaternary 

Research, v. 8, p. 236-237.

____ 1977b, Holocene woodlands in the Southwestern deserts:

Science, v. 198, p. 189-192.

Van Devender, T. R., and Mead, J. I., 1978, Early Holocene and 

late Pleistocene amphibians and reptiles in Sonoran Desert 

packrat middens: Copeia, no. 3, p. 464-475.

Van Devender, T. R., Phillips, A. M., Ill, and Mead, J. I., 1977, 

Late Pleistocene reptiles and small mammals from the Lower 

Grand Canyon of Arizona: Southwestern Naturalist, v. 22, 

p. 49-66.

Van Devender, T. R., and Spaulding, W. G., 1979, Development of 

vegetation and climate in the southwestern United States: 

Science, v. 204, p. 701-710.

Van Devender, T. R., and Wiseman, F. M., 1977, A preliminary 

chronology of bioenviromental changes during the Paleoindian 

period in the monsoonal Southwest, in Johnson, Eileen, ed., 

Paleoindian lifeways: Lubbock, West Texas Museum Association, The Museum Journal, v. 17, p. 13-27.

Van Devender, T. R., and Worthington, R. D., 1977, The herpetofauna of Howell's Ridge Cave and the paleoecology of the 

northwestern Chihuahuan Desert, in Wauer, R. H., and 

Riskind, D. H., eds., Transactions of the symposium on the 

biological resources of the Chihuahuan Desert region: U.S. 

National Park Service Proceedings and Transaction Series, 

no. 3, p. 85-106.

Watts, W. A., 1980, Late Quaternary vegetation of central Appa-
REFERENCES CITED 55

lachia and the New Jersey coastal plain: Ecological Monographs, v. 49, p. 427-469.

Webb, Thompson, III, and Bryson, R. A., 1972, Late- and postglacial climatic change in the northern Midwest, United States 

of America: Quaternary Research, v. 2, p. 70-115.

Wells, P. V., 1976, macrofossil analysis of woodrat (Neotoma) 

middens as a key to the Quaternary vegetational history of 

arid America: Quaternary Research, v. 6, p. 223-248.

____ 1977, Reply to comment by T. R. Van Devender: Quaternary 

Research, v. 8, p. 238-239.

1979, An equable glaciopluvial in the West Pleniglacial

evidence of increased precipitation on a gradient from the 

Great Basin to the Sonoran and Chihuahuan deserts: Quaternary Research, v. 12, p. 311-325.

Wells, P. V., and Berger, Rainer, 1967, Late Pleistocene history 

of coniferous woodland in the Mojave Desert: Science, v. 155, 

p. 1640-1647.

Wells, P. V., and Jorgensen, C. D., 1964, Pleistocene wood rat 

middens and climatic change in Mohave Desert A record of 

juniper woodlands: Science, v. 143, p. 1171-1174.

Winograd, I. J., 1981, Radioactive waste disposal in thick unsaturated zones: Science: v. 212, p. 1457-1464.

Winograd, I. J., and Doty, G. C., 1980, Paleohydrology of the 

southern Great Basin, with special reference to water table 

fluctuations beneath the Nevada Test Site during the late(?) 

Pleistocene: U.S. Geological Survey Open-File Report 80-569, 

97 p.

Winograd, I. J., and Thordarson, William, 1975, Hydrogeologic and 

hydrochemical framework, south-central Great Basin, NevadaCalifornia, with special reference to the Nevada Test Site: 

U.S. Geological Survey Professional Paper 712-C, C1-C126 p.

Wright, H. E., Jr., 1972, Interglacial and post glacial climates 

The pollen record: Quaternary Research, v. 2, p. 274-282.

_____ 1976, The dynamic nature of Holocene vegetation: Quaternary Research, v. 6, p. 581-596.

SUPPLEMENTAL DATA

Modern packrat middens. [Data from modern packrat middens analyzed in this study, tables 11-15.] 

Ancient packrat middens. [Data from ancient packrat middens analyzed in this study, tables 16-25.]

SUPPLEMENTAL DATA

TABLE 11. Plants in a recent midden from the Owl Canyon-3 site and plants growing in

three habitats within 30 meters

spec

index of similarity; SW, southwestern; NW, northwestern]

59

Species

Ambrosia dumosa

Amphipappus fremontii

Aristida sp.

Asteraceae undet. 

Atriplex confertifolia

Boraginaceae undet. 

Brickellia arguta

S. desertorum

Bromus rubens

Cheilanthes feei

Chorizanthe brevicornu

Cryptantha sp. 

Echinocactus polycephalus

Ephedra torreyana

Ephedra sp. 

Eriogonum heermannii

Erioneuron pulchellum

Eucnide urens

Festuca octoflora

Galium stellatum

Gilia rippleyi

Gutierrezia microcephala

Haplopappus brickellioides

Hilaria rigida

Larrea divaricata

Linanthus sp.

Nicotiana trigonophylla

Opuntia basilaris

Peucephyllum schottii

Physalis crassifolia

Plantago sp. 

Pleurocornis pluriseta

Poaceae undet. 

Prunus fasciculata

Salvia dorrii

Sitanion hystrix

Sphaeralcea ambigua

Stipa arida

NISP

N

Modern vegetation 

(relative abundance)

SW slope

(4) 

(1)

(1) 

(1) 

(1)

(X)

(1)

(2) 

(1)

(2) 

(3)

(1) 

(X)

(4) 

(1)

(1)

(1)

(1) 

(3)

(3)

(1)

(1)

(1) 

(1)

24 

16

NW slope

(3) 

(3)

(2)

(1) 

(1)

(1) 

(1)

CD

(5) 

(1)

(2)

(3) 

(1)

CD 

(1)

15

12

Wash

(3)

(1)

(D 

(1)

(1) 

(D

(X) 

C4)

(2)

(3)

(D 

(2)

12

7

Recent midden 

count

55 

3 

50

165 

4 

9

2 

10

1

9 

76

7

7

4

15 

125

453

764 

172

56

1

4 

15

21

35 

6

2,069 

26 

14

IS (SW slope vegetation to recent midden): 73

IS (NW slope vegetation to recent midden): 77

IS (wash vegetation to recent midden): 67

Number of plant taxa in midden debris, not observed in vegetation: 6

Number of plant taxa in local vegetation, not observed in the midden: 7
60 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 12. Plants in a recent midden from the Last Chance Range site and those growing

within 30 meters

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 4, abundant; 

3, common; 2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; N, number of 

plant taxa; Nts, number of species of trees, shrubs, and succulents; IS, Sorensen's index of similarity;]

Species

Ambrosia dumosa

Asteraceae undet. 

Atriplex confertifolia

Boraginaceae undet. 

Brickellia desertorum

Bromus rubens

Buddleja utahensis

Cheilanthes feei

Chorizanthe brevicornu

C. rigida 

Cryptantha sp. 

Echinocactus polycephalus

Ephedra funerea

E. torreyana 

Ephedra sp. 

Eriogonum fasciculatum

E. heermannii

E. inflatum

Eriogonum sp. 

Erioneuron pulchellum

Eucnide urens

Galium stellatum

Gilia sp.

Gutierrezia microcephala

Haplopappus brickellioides

Larrea divaricata

Lepidium fremontii

Lycium andersonii

Mirabilis sp.

Mortonia utahensis

Muhlenbergia porteri

Nicotiana trigonophylla

Opuntia basilaris

Phacelia sp.

Plantago sp. 

Pleurocoronis pluriseta

Poaceae undet. 

Prunus fasciculata

Salvia dorrii

S. mohavensis

Sphaeralcea sp.

Stipa arida

NISP

N

N

ts

Modern vegetation 

(relative abundance)

(4) 

(3)

(1) 

(3)

(3) 

(X) 

(X) 

(X)

(1) 

(1)

(11

(1)

(1) 

(X) 

(X)

(1) 

(3) 

(1)

(X) 

(2)

(4) 

(1)

(1) 

(1)

(2) 

(1) 

(X)

(1)

Q) 

(1)

(2)

31 

19

Recent midden 

count

127 

71 

189

11 

35 

12

45

2

1 

14 

5

52

11

9 

74

6

1 

2

728

11

2 

65

5 

9

12

15

4 

10 

2

24 

12

1,566 

28 

19

IS (vegetation at the site to plant debris in midden): 84

Number of plant taxa in midden debris, not observed in vegetation: 7

Number of plant taxa observed in local vegetation, but not observed in the midden: 5
SUPPLEMENTAL DATA

TABLE 13. Plants in a recent midden from the Specter Range-2 site and those growing

within 30 meters

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 

4, abundant; 3, common; 2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified 

specimens; N, number of plant taxa; A^s, number of species of trees, shrubs, and succulents; IS, Sorensen's 

index of similarity]

61

Species

Ambrosia dumosa

Amphipappus fremontii

Artemisia sec. Tridentatae 

Atriplex confertifolia

Boraginaceae undet. 

Brickellia watsonii

Brickellia sp.

Bromus rubens

Buddleja utahensis

Cryptantha conf ertiflora

Echinocactus polycephalus

Ephedra torreyana

Eriogonum deflexum

E. heermannii

E. inflatum

Fendlerella utahensis

Galium stellatum

Gilia sp.

Gutierrezia microcephala

Haplopappus brickellioides

Krameria parvifolia

Larrea tridentata

Leptodactylon pungens

Lycium andersonii

Oryzopsis hymenoides

Poaceae undet. 

Prunus fasciculata

Salvia dorrii

Scopulophila rixfordii

Sitanion hystrix

Sphaeralcea ambigua

Sphaeralcea sp.

Stipa arida

Stipa sp. 

Thamnosma montana

NISP 

N

N ts

Modern vegetation 

Crelative abundance).

Crest

(1) 

(3)

(3)

(2)

(U 

(2)

(1) 

(X)

(1)

(3)

CD

17 

CD

(D 

(2)

(l) 

(D 

(21

18 

13

Slopes

(2) 

(2)

(2) 

C2)

(X)

(3)

(X) 

(3)

(1)

(3) 

(1) 

(1)

(1)

(3)

(D 

(3) 

(D

(2) 

(D

19 

12

Recent midden 

count

2

533 

6

1 

7 

28

262 

6

3

2

20 

3

1 

81

1 

27 

103

14 

151

9

1 

4

1,266 

23

15

IS (crest vegetation to recent midden debris): 64

IS (slope vegetation to recent midden debris): 74

Number of plant taxa in midden debris, not observed in vegetation: 5

Number of plant taxa in local vegetation, not observed in the midden: 5

 Present but more than 30 meters from the site.
62 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 14. Plants in recent midden debris from the Eleana Range-3 site and those

growing within 30 meters

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 

4, abundant; 3, common; 2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified 

specimens; N, number of plant taxa; Nts, number of species of trees, shrubs, and succulents; IS, Sorensen's 

index of similarity)

Modern vegetation 

Species 

(relative abundance)

Artemisia nova

A. tridentata

Artemisia sec. Tridentatae 

Atriplex canescens

Boraginaceae undet. 

Brickellia calif ornica

Bromus rubens

Cowania mexicana

Crvptantha confertif lora

Cryptantha sp. 

Ephedra torreyana

E. viridis

Ephedra sp. 

Eriogonum caespitosum

E. fasciculatum

E. inflatum

E. microthecum

Festuca sp.

Forsellesia nevadensis

Haplopappus nanus

Heterotheca villosa

Juniperus osteosperma

Leptodactylon pungens

Linum lewis ii

Opuntia erinacea

Oryzopsis hymenoides

Penstemon sp.

Phacelia sp.

Pir.us flexilis

P. monophylla

Poaceae undet. 

Purshia tridentata

Quercus gambelii

Rhus trilobata

Salvia columbariae

Senecio multilobatus

Sphaeralcea sp.

Stanleya pinnata

Stipa sp. 

Symphoricarpos longiflorus

Symphoricarpos sp.

NISP 

N

N ts

IS (current vegetation to recant midden debris): 77 

Number of plant taxa in midden debris, not observed in vej 

Number of plant taxa in local vegetation, not observed in

(2) 

(3)

(4)

(1)

(X) 

(1) 

(X)

(1) 

(2)

(1) 

(1)

(X) 

(1) 

(1)

(2) 

(X)

(1) 

(1) 

(X)

If 

(X)

(X) 

(2)

(1) 

(X) 

(X)

(1) 

(1) 

(3)

(2)

29 

16

jetation: 6 

the midden: 9

Recent midden 

count

19

387 

10

153

1

16

2 

12

75

5

1 

26 

1

3 

3 

79

177 

1 

2

5 

17

4

999 

22 

15

 Present but not more than 30 meters from the midden.
SUPPLEMENTAL DATA 63

TABLE 15. Plants in a recent midden from the Connley Hills-1 and -2 sites, and those growing

within 30 meters of each locality

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 4, abundant; 

3, common; 2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; N, number of 

plant taxa; N^s, number of species of trees, shrubs, and succulents; IS, Sorensen's index of similarity]

Species

Amsinckia sp.

Artemisia tridentata

Boraginaceae undet.

Bromus tectorum

Chenopodium cf . botrys

Chrysothamnus nauseosus

C. viscidiflorus

Chrysothamnus sp .

Descurainia sp.

Juniperus occidentalis

Oryzopsis hymenoides

Poaceae undet.

Purshia tridentata

Ribes cereum

NISP

N

N ts

IS (current vegetation

IS (current vegetation

Number of plant taxa in

Number of plant taxa in

Number of plant taxa in

Number of plant taxa in

Connley Hills-1

Modern vegetation Recent midden

(relative abundance)

(X)

(4)

-

(2)

(5)

(1)

(X)

(1)

(3)

_

(1)

1,

10

5

to recent midden at Connley

to recent midden at Connley

count

2

25

8

35

37

2

148

11

432

8

904

_

1

613

12

5

Hills 1): 100

Hills 2): 91

Connley Hills 1 midden debris, not observed

vegetation at Connley Hills 1, not observed

Connley Hills 2 midden debris, not observed

vegetation at Connley Hills 2, not observed

Connley Hills-2

Modern vegetation Recent midden

(relative abundance) count

_

(3) 138

-

(3) 18

50

(5) 230

(1)

40

(X) 97

(3) 1,059

7

(2) 156

15

(1) 8

1,818

8 11

5 6

in vegetation: 0

in the midden: 0

in vegetation: 2

in the midden: 0
64 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 16. Plants from the Owl Canyon (OC) Locality

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 4, abundant; 3. common; 

2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; N, number of plant taxa; Nt*, number of 

species of trees, shrubs, and succulents; IS, Sorensen's index of similarity]

Owl Canyon-2

Vegetation Macrofossil assemblages 

(relative sample number and count

abundance) OC-2(1) OC-2(3)

Approximate radiocarbon age - 10,260 10,070 

Species 

Agave utahensls - 706 437

Agropyron sp. - 13 

Ambrosia dumosa (3)

Amphipappus fremontil (1)

Amslnckla sp. - 11

Anemone tuberosa - 55

Arlstlda sp. - - -

Arteralsla sec. Trldentatae - - -

Asteraceae undeL. - 5 13 

cf. Astragalus sp. (2 spp.) - 12 15 

Atrlplex confertlfolla - 2 -

Boraginaceae undet. - 17 

Brickellla arguta (1)

B. desertorum - - -

Brickellla sp. - 22 51

Bromus rubeus (X) - -

Buddleja utahensls - 83 161

Chellanthes feel - - -

Chorlzanthe cf. brevlcornu (X)

Chrysothamnus nauseosus - - 9

Clrstum sp. - 207 88

Crypt ant ha sp. (X) 

Echlnocactus polycephalus (3) - -

Encella sp. - - 1

Ephedra torreyana - - 

Ephedca sp. - 1 - 

Erlogonum heermannli - - -

Erlogonum sp. (X) 

Erloneuron pulchellum (2)

Eucnlde urens (3)

Fabaceae undet. - - - 

Fallugla paradoxa - 23

Festuca octoflora - - -

Gallum stellatum - - -

Gllla rippleyl (X)

Gutlerrezia mlcrocephala (2)

Junlperus osteosperma - - 1

Haplopappus brlckellioldea - - -

Hllarla rlglda - - -

Vegetation 

(relative 

abundance)

(3) 

(2)

(1) 

(1)

(X) 

(X)

(X) 

(2)

(1) 

(1)

(1) 

(2)

(X) 

(1) 

(X) 

(4)

(1) 

(X)

Owl Canyon-3

Macrofossil assemblages 

sample number and count

OC-3(mod) OC-3(1) OC-3(2)

32,900 >28,700 

324 185

55 - - 

3 - -

50 - - 

2 - 

165 - 5

4 41 4 

9 - 1 

2 - - 

10 - -

1 - -

4 6

9 - - 

468 1,345 

25 - 

76 - - 

7 - 7

7 - - 

1 -

15 - - 

125 

- 2 

2 -

453 

I/ I/

_
SUPPLEMENTAL DATA

TABLE 16. Plants from the Owl Canyon (OC) Locality Continued

65

Owl Canyon-2

Vegetation Macrofossll assemblages 

(relative sample number and count

Larrea dlvaricata

Lepldlum cf. fremontil

cf. Leptodactylon sp.

Llnanthus sp.

Lye lum sp. 

Nlcotiana trlgonophylla

Opuntia basilaris

Opuntla sp. 

Penstemon sp.

Peucephylluro schottil

Physalls crasslfolla

Plantago sp. 

Pleurocoronls plurlseta

Poaceae undet. 

Prunus fasciculata

Psorothamnus fremontli

Salvia dorrii

Scopulophila rlxfordll

Sitanion hystrlx

Sphaeralcea ambigua

Sphaeralcea sp.

Stipa arida

Stlpa sp. 

Symphorlcarpos longiflorus

NISP 

N

Nts 

IS (to current vegetation)

abundance) OC--2(1)

(3) 

1 

3 

12

(3)

(3) 

63 

44 

7 

17 

91

(1) 

29

(4)

1,315 

17 23 

10 14 

8

OC--2(3)

2

21

1

75 

33 

3 

1 

115

12

3

1,063 

24 

15 

8

Vegetation 

(relative 

abundance)

(2)

(1) 

(1)

(3)

(3) 

(1) 

(2)

(X) 

(1)

(X)

28 

20

Owl Canyon -3

Macrofossll assemblages 

sample number and count

OC--3(mod) OC764 

172

56 

1

4

15 

21 

35

6

2,069 1 

26 

16 

72

-3(1) OC--3(2)

3

1

130 129

2 9 

4 

3 

6 7 

279 614

2 11

33 34 

,329 2,360 

18 16 

16 13 

27 24

 Very abundant (>1,000), not counted.
66 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 17. Plants from the Point of Rocks (PR) I site

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 

4, abundant; 3, common; 2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; 

N, number of plant taxa; Nts, number of species of trees, shrubs, and succulents; IS, Sorensen's index of 

similarity]

Approximate radiocarbon age 

Species

Ameranthus sp. 

Ambrosia dumosa 

Ambrosia sp.

Amsinckia tesselata 

Amsinckia sp. 

Aristida sp.

Artemisia sec. Tridentatae 

Asteraceae undet. 

Atriplex canescans

Atriplex confertifolia 

Boraginaceae undet. 

Brickellia arguta

JB. watsonii 

Brickallia sp. 

Bromus rubens 

Ceratoides lanata 

Cheilanthes feei 

Chorizanthe rigida 

Coleogyne ramoslssima

Cryptantha sp. 

Echinocactus polycephalus

Ephedra funerea

Ephedra torreyana 

Ephedra sp. 

Eriogonum inflatum

Erioneuron pulchellum 

Erodium cicutarium 

Eucnide urens

Forsellesla nevedensis 

Galium Stellaturn

Vegetation

(reletive

abundance)

Macrofossil assemblages 

sample number and count

(2)

(X) 

(X)

(1)

(2) 

(1)

(X)

(X) 

(X)

(2)

(2)

(11

(X)

(3) 

(X) 

(2)

(2)

PR-l(l) PR-1(3)

9,840

36

11,680

13

50

10

56

89
SUPPLEMENTAL DATA

TABLE 17. Plants from the Point of Rocks (PR)-l site Continued

67

Gilia sp.

Gutierrezia microcephala

Krameria parvifolia

Langloisia setosissima

Larrea divaricata

Lepidium cf. fremontii

Lepidium sp. 

Lepidospartum latisquamum

Leptodactylon pungens

Lycium andersonii

L. pallidum

Lycium sp. 

Menodora spinescens

Nicotiana trigonophylla

Opuntia basilaris

0. echinocarpa

0. cf. ramosissima

Opuntia sp . 

Penstemon sp.

Peucephyllum schottii

Phacelia sp.

Plantago sp. 

Poaceae undet. 

Porophyllum gracile

Prunus fasciculata

Purshia glandulosa

Purshia sp .

Salvia dorrii

Scopulophila rixfordii

Sphaeralcea ambigua

Sphaeralcea sp.

Svmphoricarpos longiflorus

Thamnosma montana

Yucca brevifolia

NISP

N

N ts 

IS (to current vegetation)

Vegetation 

(relative 

abundance)

(4) 

(1)

(2)

(1) 

(3)

(1) 

(1)

(1) 

(1)

(X) 

(X)

(1)

(2) 

(1)

31 

19

Macrofo 

sample

PR-l(l)

76

142

25 

60

5

43

49

1 

30

6 

566

1

19

J 

2

12

1,256

24 

19 

37

ssil assemblages 

number and count

PR-1 (3)

1 

152

7

13 

185

3 

14

16

18 

258

1

42

117

2 

3

7 

17

1,098

23 

17 

39

 Species in the vicinity, but occurring more than 30 meters from the site.
68 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 18. Plants from the Point of Rocks <PR)-2 and -3 sites

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 4, abundant; 3, common; 2, occasional; 

1, rare; X, present within 30 meters; NISP, number of identified specimens; N, number of plant taxa; AT(S , number of species of trees, shrubs, and 

succulents; IS, Sorensen's index of similarity]

Approximate radiocarbon age 

Species 

Agave utahensis

Ambrosia dumosa

Amphipappus fremontii

Amsinckia sp.

Aristida cf. adscensionis

Artemisia cf. bigelovii

Artemisia sec. Tridentatae

Asteraceae undet. 

Atriplex cf. canescens

A. confertifolia

Boraginaceae undet . 

Brickellia arguta

Bromus rubens

Buddleja utahensis

Ceratoides lanata

Cheilanthes feei

Chorizanthe brevicornu

C. rigida 

Chorizanthe sp.

Chrysothamnus nauseosus

Coleogyne ramosissima

Coryphantha vivipara

Cryptantha spp. 

Draba sp.

Echinocactus polycephalus

Encelia virginensis

Ephedra funerea

E. torreyana 

Ephedra sp. 

Eriogonum heermannii

E. inflatum

Erioneuron pulchellum

Eucnide urens

Eurotia lanata

Fallagia paradoxa

Festuca octoflora

Forsellesia nevadensls

Galium stellatum

Gilia sp.

Gutierrezia microcephala

Gutierrezia sp.

Haplopappus brickellioides

Haplopappus cf. nanus

Hilaria ridiga

Krameria parvifolia

Lappula redowskii

Larrea divaricata

Lepidium fremontii

Lepidium sp. 

Leptojactylon pungens

Vegetation 

(relative 

abundance)

(2) 

(2) 

(X) 

(X)

(4)

(3) 

(X)

(X) 

(X)

(1)

(1) 

(2)

(X) 

(2)

(2) 

(3) 

(3)

(2) 

(2)

(1) 

(2)

Point of Rocks-2

Macrofossil assemblages 

sample number and count

PR-2(2) PR-2(3)

9,560 9,260

186 195

3 45 

2 

2 

31 21

5 30 

1

9 17 

9

2 

6 

66 103

4 8 

2 3 

1 

3

96 236 

8 15

9

2 

34 53 

1

1

30 2 

102 8

1 7

Point of Rocks -3

Vegetation Macrofossil assemblages 

(relative sample number and count

abundance) PR-3

34,800

(4) 

(3) 

(X) 5 

(3)

2 

14

(1) 415 

_ i

(1) 

(X) 

11

(X) 

(X)

101

11

1

21 

(1) 1

(2) 

(1) 

123 

5

(2) 

(1) 

1

(X) 4

(2)

(2) 9 

9 

(11

(3) 

(11

1
SUPPLEMENTAL DATA

TABLE 18. Plants from the Point of Rocks (PR)-2 and -3 sites Continued

69

Lycium andersonii

Lycium sp. 

Mirabilis sp.

Nicotiana trigonophylla

Opuntia basilaris

0. cf. erinacea

Oryzopsis hymenoides

Penstemon sp.

Petrophytum caespitosum

Peucephyllum schottii

Phacelia sp.

Pleurocoronis pluriseta

Poaceae undet. 

Prunus fasciculata

Scopulophila rixfordii

Sphaeralcea ambigua

Sphaeralcea sp.

Stephanomeria pauciflora

Stipa sp. 

Symphoricarpos longiflorus

Thamnosma montana

Tidestromia oblongifolia

Yucca brevifolia

Y. schidigera 

NISP 

N

N ts

Vegetation 

(relative 

abundance)

U)

(1)

(2) 

(2)

(1) 

(1)

I/

27 

17

Point of Rocks-2

Macrofossil assemblages 

sample number and count 

PR-2(2) PR-2(3)

2 

32 

2

1 

57 

442 

84

1 

2 

3

1,210 

28 

12 

41

2

34 

34 

3

104 

220 

171 

1

29 

18

1,390 

31 

18 

40

Vegetation 

(relative 

abundance)

(2)

(2) 

(X)

(2) 

(2)

27 

15

Point of Rocks -3

Macrofossil assemblages 

sample number and count 

PR -3

17 

19

2 

14

4

17 

1

151 

961

13

1,968 

28 

18 

24

 Species in the vicinity but occurring more than 30 meters from the site.
70 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 19. Plants from the Last Chance Range (LCR)-l site

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 4, abundant; 3, common; 

2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; AT, number of plant taxa; ATts, 

number of species of trees, shrubs, and succulents; IS, Sorensen's index of similarity]

Approximate radiocarbon age 

Species 

Agave utahensis

Ambrosia acanthicarpa

A. dumosa

Amslnckla sp.

Anemone tuberosa

Artemlsia sec. Tridentatae

Asteraceae undet. 

Atriplex confertifolia

Boraginaceae undet. 

Brickellia arguta

B. desertorum

Broraus rubens

Huddle j a utahensis

Castilleja sp. 

Cercocarpus intricatus

Cheilanthes feel

Chorizanthe brevicornu

C. riglda 

Cirsium sp.

Cryptantha cf. pterocarya 

Cryptantha sp. 

Echinocactus polycephalus

cf. Echinocereus sp.

Encella virginensis

Ephedra funerea

E. torreyana 

E. viridis

Ephedra sp. 

Eriogonum fasciculatum

Eriogonum heermannii

E. inflatum

Eriogonum sp. 

Erioneuron pulchellum

Eschscholtzla sp.

Eucnide urens

Forsellesla nevadensls

Galium stellatum

Gilia sp.

Gutierrezia mlcrocephala

Haplopappus brickelliodes

Junlperus osteosperma

Larrea divaricata

Lepidium fremontii

Lepldium sp. 

Lesquerella sp.

Lycium andersonli

Lycium sp. (not L. andersonii)

Mirabilis sp.

Mortonia utahensis

Muhlenbergia porterl

Nicotiana trigonophylla

Opuntia basilaris

0. cf. echinocarpa

Opuntia sp.

Vegetation 

(relative 

abundance)

(4)

(3)

(1) 

(3) 

(3)

(X) 

(X) 

(X)

(1)

(1) 

(1)

(1) 

(1) 

(X) 

(X) 

(1)

(3)

(1) 

(X) 

(2)

(4)

(1)

(1) 

(1) 

(2) 

(1)

Macrofossil assemblages 

sample number and count

LCR-l(mod)

127

71 

189 

11

35 

12 

45

2 

1

14 

5

52

11 

9

74

6 

1 

2

728 

11

2 

65

5 

9

LCR-K2)

9,280 

45

4

13 

1

101 

2

3

1

1

1 

1

14

5

2 

29

1

7 

170

28 

1 

110 

854

3

16

LCR-K3)

11,760

76 

17

1 

4 

82 

6

1

9 

6 

37

10 

5 

1

32

1 

64

719 

I/

29

14 

4

2 

10
SUPPLEMENTAL DATA

TABLE 19. Plants from the Last Chance Range (LCR)-l site Continued

71

Penstemon sp.

Phacelia sp.

Plantago sp.

Pleurocoronis pluriseta

Poaceae undet.

Prunus fasciculata

Salvia dorrii

S . mohavensis

Sphaeralcea sp.

Stanleya cf. elata

Stipa arida

Symphoricarpos longiflorus

Yucca brevifolia

NISP

N

Nts

IS (to current vegetation)

Vegetation 

(relative 

abundance)

(X)

-

(1)

-

_

(1)

(1)

_

_

(2)

_

_

_

31

19

-

Macrofossil assemblages 

sample number and count

LCR-l(mod)

_

12

_

15

4

10

2

24

_

12

_

_

1,566

28

19

79

LCR-K2)

5

3

2

-

43

_

36

_

19

3

_

4

217

1,751

34

20

31

LCR-1(3)

_

-

13

41

820

_

32

_

_

183

_

2,219

28

18

32

 Very abundant (>1,000), not counted.
72 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 20. Plants from the Specter Range (Spc)-2 site Continued

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 4, abundant; 3, common; 

2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; N, number of plant taxa; Nts, 

number of species of trees, shrubs, and succulents; IS, Sorensen's index of similarity]

Approximate radiocarbon age 

Species 

Ambrosia dumosa

Amphipappus fremontii

Artemisia sec. Tridentatae

Asteraceae undet. 

Atriplex confertifolia

Boraginaceae undet. 

Brassicaceae undet. 

Brickellia watsonii

Brickellia sp.

Bromus rubens

Buddleja utahensis

Castilleja sp. 

Ceratoides lanata

Cercocarpus intricatus

Chrysothamnus nauseosus

C. visidiflorus

Chrysothamnus sp.

Coleogyne ramosissima

Cryptantha cf. confertiflora

Ecliinocactus polycephalus

Ephedra rorreyana

Ephedra sp. 

Erigeron sp. 

Eriogonum deflexum

E. cf. fasciculatum

E. heermannii

E. inflatum

Fendlerella utahensis

Forsellesia cf. nevadensis

Galium stellatum

Cilia sp.

Gutierrezia microcephala

Haplopappus brickelliodes

H. cooperi - type 

Hecastocleis shockleyi

Juniperus osteosperma

Krameria parvifolia

Larrea divaricata

Lepldium sp. 

Leptodactylon pungens

Lesquerella sp. 

Lycium andersonii

Mortonia utahensis

Opuntia sp. 

Oryzopsis hymenoides

Penstemon cf. petiolatus

Petrophytum caespitosum

Pinus monophylla 

Pleurocoronis pluriseta

Poaceae undet. 

Prunus fasciculata

Purshia tridentata

Vegetation . Macrofossil assemblages

(relative , , . sample number and count

abundance)

Ledges 

Crest and Spc-2(mod) Spc-2(2) Spc--2(2) Spc-2(3) Spc--2(6) Spc-2(8) Spc--2(10) Spc^dl^ 

talus

18,740 19,290 23,280 25,900 -/ 27,900 29,140 -/ 32,260

(1) - - - ."-_ _- 

(3)-- ______

2 1 2 48 21 4 - 9 

2---- 28 3 

(3) (2) 533 - - 336 21 33 40 217

6 12---- 1 

(2)- ______

(2) (2) 7 - - - 

(2) 28 ----- -

-(!)- - -- 4 12 2

35 32 1 

--_ _ _ 5 - 3 -

--- x 4 3 _ _ _

(1) - !___-_- 

(!) _ ___--- 

(!)-- ______

(2) (3) 262 ----- - 

1 2 - - - - 1 

_ - _ !____- 

(X) - ____--

-_- _ _ 5 2 - - 

(1) (3) 6 - 3 2 1 - - 

(X)-- ______ 

- - 3 138 128 28 - 65 100

_ 1 

(DO)

(3) (3) 20 - - - - 

(1) 3 _____ 9

14 10 - 29 

__ ______ i

21 21 21 21 21 21 21

(1) (1) - ______

3/ - !___-_- 

(1) - 81 ----- -

-- - 8 13-- -- 1 

(1) ______

--- ______ 16

!____- 1 

-- 1-25 341- 1

- - - 7 12 150 51 36 207

- - - 631 2] - - 

-__ ___- 8 _

-- 27 3 122- 4 

(1) (3) 103 ----- -

--_ ____ i- l

Spc-2(ll) 2 Spc-2(12)

32,100 25,150

6 5

118 18 

1

25 

1 

5 

12

5

2 

1 5

211 7

19 

4 3

21 21

-

3 1

3

1 1 

4 

303 57

1
SUPPLEMENTAL DATA 

TABLE 20. Plants from the Specter Range (Spc)-2 site Continued

73

Salvia dorrii

Scopulophila rlxfordii

Sitanion histrlx

Sphaeralcea ambigua

Sphaeralcea sp.

Stanleya sp.

Stipa arida

Stipa sp.

Streptanthus sp.

Symphoricarpos longiflorus

Tetrad ymia sp.

Tharanosma montana

NISP

N

N 

ts

IS (to current vegetation)

Vegetation 

(relative 

abundance)

Ledges

Crest and Spc-2(mod) 

talus

(2) (]) 14 

(3) 151 

U) 

(1) 

- - 9

-

(1) (2) 

- - 1

-

(2) (1) 4 

1,268

18 20 24

14 13 17 

72

Macrofossil assemblages 

sample number and count

Spc-2(2) Spc-2(2) 2 Spc-2(3) Spc-2(6) Spc--2(8) Spc--2(10) Spc-2(ll) 1 Spc--2(ll) 2 Spc--2(12)

__!___ __ 

1 27 11 185 48 81 229 160

______ __

2 21--- 11-

1 - - - -

3_____ -- 

224 78 30 34 56 65 39 102 91 

4 1 61 44 14 2 57 14

1,059 306 727 225 314 192 713 1,089 386

16 17 19 16 15 12 20 20 16

11 11 13 11 13 9 14 12 12 

7 13 19 20 12 21 18 19 13

 Exact chronologic position uncertain, see table 6.

2/

 Very abundant (>1,000), not counted.

 Species in the vicinity, but occurring more than 30 meters from the site.
74 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 21. Plants from the Specter Range (Spc)-3 site

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 4, abundant; 

3, common; 2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; N, number of 

plant taxa; NIS , number of species of trees, shrubs, and succulents; IS, Sorensen's index of similarity]

Approximate radiocarbon age 

Species 

Ambrosia dumosa

Amphipappus fremontii

Aristida sp.

Artemisia sec. Tridentatae

Asteraceae undet. 

Atriplex confertifolia

Boraginaceae undet. 

Brickellia arguta

B. watsonii

Buddleja utahensis

Castilleja sp. 

Ceratoides lanata

Cheilanthes feei

Chrysothamnus nauseosus

Coleogvne ramosissima

Cowania mexicana

Cryptantha cf . pterocarya 

Cryptantha sp. 

Descurainia sp.

Echinocactus polycephalus

Encelia virginensis

Eohedra funerea

E. nevadensis

Ephedra sp. 

cf . Eriogonum fasciculatum

E. heermannii

E. inflatum

Fendlerella utahensis

Forsellesia cf. nevadensis

Galium stellatum

Gilia sp.

Grayia spinosa

Gutierrezia microcephala

Haplopappus cooperi (or nanus)

Juniperus osteosperma

Larrea tridentata

Lepidium fremontii

cf. Leptodactylon pungens

Vegetation 

(relative

abundance)

(1)

(2)

(1)

(2)

(3)

(1)

(3)

(2)

(X)

2/

_

(X)

(1)

(1)

(1)

(1)

_

(X)

_

(1)

(2)

(2)

_

2/

(3)

_

Macrofossil assemblages 

sample number and count

Spc-3A(l) Spc-3A(2)

20,200 I/

_

_

2 36

19 

118 9

-

_

_

1 

166 4

1 62

3

16

5

10 

15 

2

_

_

_

_

207

1 1

_ _

3 32

1 4

_

24

3 1

2 1

7

3/ 3/

_

2 5

1

Spc-3B

28,460

-

_

127

8 

201

1

_

_

21

_

3

_

_

-

_

.

_

1

_

_

17

2

_

2

_

_

2

3/

_

2

2
SUPPLEMENTAL DATA 

TABLE 21. Plants from the Specter Range (Spc)-3 site Continued

75

Lesquerella sp.

Lycium andersonii

L. pallidum 

Lye ium sp. 

Mirabilis sp.

Mortonia utahensis

Opuntia cf . erinacea

Opuntia sp. 

Oryzopsis hymenoides

Petrophytum caespitosum

Phacelia cf. rotundifolia

Phacelia sp.

Plagiobothrys jonesii

Poa fendleriana

Poaceae undet. 

Scopulophila rixfordii

Sphaeralcea amhigua

Sphaeralcea sp.

Stephanomeria pauciflora

Stipa arida

Symphoricarpos longiflorus

Tetradymla axillaris

Thamnosma montana

Yucca brevifolia

Yucca sp.

NISP 

N

N ts 

IS (to current vegetation)

Macrofossil assemblages Vegetation s

. . sample number and count

abundance) Spc-3A(l) Spc-3A(2)

1 - 

(2) 

(2) 

1 

- 2

5 

5 

(X) 3 2 

12 1 

(X) 

- 6

(X)

(1)

- 5 

(3) 10 8 

(2) 

2 -

(1) 

(2) 

91 609 

(1) 

(1)

- 3

423 1,107 

33 18 33 

20 15 22 

34 43

Spc-3B

2

1

1 

15

1 

114

162

686 

22 

15

17

 Contaminated sample, see table 6.

2/

 Species in the vicinity, but occurring more than 30 meters from the site.

 Very abundant (>1,000), not counted.
76 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 22. Plants from the Specter Range (Spc)-l site

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant; 4, abundant; 

3, common; 2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; N, number of 

plant taxa; Nts, number of species of trees, shrubs, and succulents; IS, Sorensen's index of similarity]

Approximate radiocarbon ages

Species 

Acamptopappus sphaerocephalus

Ambrosia dumosa

A. eriocentra

Amsinckia sp.

Arabis sp.

Aristida glauca

Asteraceae undet. 

Atriplex canescens

A. confertifolia

Boraginaceae undet. 

Brickellia arguta

B. desertorum

Bromus rigidus

B. rubens

Buddleja utahensis

Castilleja sp. 

Ceratoides lanata

Chorizanthe rigida

Chrysothamnus viscidif lorus

Coleogyne ramosissima

Coryphantha vivipara

Cryptantha sp. 

Cuscuta sp.

Descurainia sp.

Dichelostemma pulchellum

Echinocactus polycephalus

Echinocereus sp.

Encelia virginensis

Ephedra nevadensis

E. torreyana 

Ephedra sp. 

Eriogonum heermannii

E. fasciculatum

E. inflatum

In wash

(2) 

(1)

(X) 

(3)

(X) 

(X)

(X) 

(1)

(X) 

(3)

Vegetation 

(relative abundance)

On rocks On top 

and terrace of ridge

(1) 

(1)

(X) 

(X)

(1)

(3) 

(2)

(X) 

(1) 

(X) 

(1) 

I/

II

(1) 

(X)

(1)

I/ 

(1) 

(1)

(4) 

(X)

Macrofossil assemblages 

sample number and count

Spc-l(l) Spc-l(2)

300+40 100-100

3 21 

1 3

22 21 

625 140 

30 

2 5 

8 2

10

4 29

40 22

1 

1

1 

1 2

1

77 70 

3 4 

5 8
SUPPLEMENTAL DATA 

TABLE 22. Plants from the Specter Range (Spc)-l site Continued

77

Erioneuron pulchellum

Euphorbia sp. 

[ 'estuca octoflora

Cilia sp.

Grayia spinosa

Gutierrezia microcephala

Hilaria rigida

Hymenoclea salsola

Krameria grayi

Larrea divaricata

Lepidium fremontii

Lepidium sp . 

Leptodactylon pungens

Lycium andersonii

L. pallidum

In wash

(X)

(3)

(4) 

(1) 

(X)

(2) 

(1)

Vegetation 

(relative abundance)

On rocks On top 

and terrace of ridge

(1)

(X) 

(X) 

(1) 

(1) 

(X)

I/

(1) 

(2)

Macrofossil assemblages 

sample number and count

Spc-l(l)

2

35

75

15 

1 

87 

34

Spc-l(2)

1

6

55

171

84

576 

23

6

Lycium sp.

Kachaeranthera tortifolia (1)

Mirabilis bigelovii

Opuntia basila'fis

Opuntia sp. (not (3. basilaris)

Oryzopsis hymenoides

Oxytheca perfoliolata (X)

Phacelia sp. (X)

Plantago sp.

Poaceae undet. -

Psorothamnus fremontii

Salazaria mexicana (1)

Salsola kali (X)

Scopulophila rixfordii

Sphaeralcea ambigua (1)

Stanleya pinnata (1)

Stipa sp.

Thamnosma montana (1)

Yucca schidigera

Yucca sp.

NISP

N 26

N ts U 

IS (to current vegetation, combined)

(X)

(X) 

(2)

(X)

(1)

(1) 

(1) 

(X)

(1) 

(1)

(1) 

I/

1,165

35

25

73

55

1,469

34

24

70

 Species in the vicinity, but occurring more than 30 meters from the site.
78 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 23. Plants from the Eleana Range (ER)-2 site

[Relative abundance values for modern vegetation data are in parentheses; they indicate: 5, very abundant: 4, abundant; 

3, common; 2, occasional; 1, rare; X, present within 30 meters; NISP, number of identified specimens; TV, number of 

plant taxa; N^s, number of species of trees, shrubs, and succulents; IS, Sorensen's index of similarity]

Approximate radiocarbon age

Spec lea

Ag ro pyron s p .

ArrcuLhobtum sp.

A r 1st Ida sp.

Arlemlsjj^ jiovn^

A. UMiiisla sec. Tridentatae

Aslerareae undet.

ALripie-x canescens

Boraglnactiae undet.

HrickcJlia rnlifornica

RrickellJa sp.

Bcoraiis tcctorum

Iii!s LLL!llS. !; PCercocarpus lediloliiis

Cli.i_maeJ>ntiar.Iji mi Itefol ium

Clirysothaiiinur! IUUHCOSUS

c - vl?.t^dtLJJiEil5

CLI si inn sp.

Cowan i a muxu-aiui

CrypLanlh.i confcrt Jl lora

Crypjumtlia -;p.

I'Vhinocereus irijjloi-liiu I.itus

Kphedra iiov.Hleiisih

( : . v i r i (1 1 s

Kr tognnuin 1 .ssciculatum

R. In T In Linn var. dcflalum

K. microtlierum

Er logonum sp.

luipjiorbla sp.

Kestura sp.

I'orsclUsla nevadcuisi s

(HI Id sp.

i'MJCiSl'-'il'l'.'l?. £2145.

llen-rolliec.i v _i_los^

Ililaria James li

Ho 1 od Lsc-us micropliy LJiis

JiinJperuK oateospurma

I.upjdlum sp.

cf. l.cpLodacLvlon pun|;,ens

I,est|uurel la sp.-

Llnura JcwlsJl

I.iip-_lnus cf. <iL'geiiteu'j

Macliaerantlu'ra c.mc> scans

M.tclinet ant hera sp.

OpiinLia erinacen

(IpiintJa s)>.

Orj/zopsls hyrai;noidcs

VeiiaLcinoii sp.

Pu t iji_d_o r la piiKUjjl

I'lidi-ol la inusLei Ina

I'li.u-tlia s|>.

I'lntis I U-xJHs

1'. monopj.ylla

I'oa. u.u- niidi-l .

Vegetation 

(rejative

abundance) ER_?(1)

JO, 600

(X)

-

(X)

(1)

30

82

CO 6

24

(1)

2

(X)

5

1H

4

(2) 15

(1) 9

 1

\l

(X)

-

I/

(1)

(?-)

I/

(X)

(X)

3

1

(X)

i/

-

(1) 231

(X)

(X)

4

11 27

-

32

9

(X)

7

(2)

1

i/ 586

-

(X) 14

!/ i

y i

(X)

(X)

6

]/ 95

58

MacrofossJ] assemblages 

sample number and count

ER-2(2) ER-2(3) ER~2(4) ER-2(5) ER-2(6) ER-2(7) ER-2(9) £11-2(10)

11,700 13,200 14,090 14,300 14,600 14,800 15,900 17,100

3

__ 19 _____

-

_

45 153 178 317 100 U9 111 172

21 146 335 95 41 71 43 25

_

41 29 4 23 9 13 8 8

_,_

2 ______

__ ______

2 1 - - - -

390 106 25 1 6 139 10

11 14 56 90 61 54 20 24

]9 44 48 102 24 29 55 35

2 82 184 Jll 43 109 24 20

_

_

-

2- !____-

-

__ ______

-

 21 

__ ____ --

__ ___- __

5 - - 5 1 1 -

3 1 - - - - _ _

-

_

1 - - 1 - -

131 108 104 87 67 53 19

-

_

7 20 5 2 11 21

270 1 -

1 -

1 - 2 5 2 2 15 3

1 - 1 3 J 1

- -

6 12 86 256 170 191 145 212

__ ___- _ -

; -

576 - _ _ _ - - -

t -

6 7 27 17 18 15 11 15

2 - - 3 21 22

32 6 2 8 -

-

_

22 21 21 21 21 21 21 21

254 - -

127 116 4b 20 i 302 1 (>4 1 IW UMI
SUPPLEMENTAL DATA

TABLE 23. Plants from the Eleana Range (ER)-2 site Continued

79

i'runus fasciculata

1'urshia tridentata

(Juercus g-imbem.

Kliu^ U-j.J_obata_

Ribes c:f. veiiiUnum

Si\ 1 vi a dorrU

Scnecto inultllolutus

Sitanion hyst i ix

Sphatralcea cf. anib i gua

St.mloya p innata

St Ipa sp.

Symplioricarpos long If lor us

Syiiiphorii-.irpus .sp.

Tclradpnia canes cens

'I'er racism la sp.

NISI'

NISI'-AT

N

H LS

IS-3 '

 Species in the vicinity, but

- Very abundant (>1,000), not

-'includes tliose fosyil trees,

., , Macrofossil assemblages Vegetation 6

(relative sample number and count

abundance) ER-?.(j) ER-2(2) ER-2(3) ER-2(4) ER-2(5) ER-2(6) ER--2(7)

I/ _______

65 40 - 24 12 18 4

17 _______

y _______

2 2 3 - -

99 88 -

(X) - 5

(X) 3

y i i

(1) _______

(X) - 2 - - 1 1 -

I/ -__-__-

67 33 - -

(J) _______

6 3 67 183 208 222 186

1,521 1,719 1,186 1,461 1,570 1,088 1,069

1,480 1,173 1,185 1,461 1,570 1,088 1,069

28 33 27 20 25 24 20 17

10 23 18 13 17 15 12 1'J

79 86 58 59 48 45 4J

more than 30 meters from the site.

counted.

KR--2(9) KR--2(10)

_

1

-

-

_

-

_

-

-

-

-

-

-

214 160

927 988

927 9«8

20 16

12 10

45 40
80 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 24. Plants from the Eleana Range (ER)-3 site

[Relative abundance values for modern vegetation data are in parentheses; they indicate; 5, very abundant; 4, abundant; 3, common; 2, occasional; 1, rare; X, present within 

30 meters; NISP, number of identified specimens; N, number of plant taxa: NfS , number of species of trees, shrubs, and succulents; IS, Sorensen's index of similarity]

Approximate radiocarbon age 

Species 

Arteraisia nova

A. tridentata

Artemisia sec. Tridentatae

Asteraceae undet. 

Atriplex canescens

A. confertifolia

Boraginaceae undet. 

Brickellia californica

B. raicrophylla

Broraus tectorum

Ceratoides lanata

Cercocarpus ledifolius

Charaaebatiaria millefolium

Chenopodium sp.

Chryaothamnus nauseosus

C. viscidif lorus

Cirsiura sp.

Cowania mexicana

Cryptantha confertiflora

Cryptantha sp. 

Ephedra torreyana

E. viridis

Ephedra sp. 

Eriogonum caespitosum

E. fasciculatura

E. inflatura

E. microthecum

Festuca sp.

Forsellesia nevadensis

Gilia sp.

Grayia spinosa

Hapiopappus nanus

Heterotheca vilosa

Holodiscus microphyllus

Juniperus osteosperraa

Lepidium sp. 

Leptodactylon pungens

Lesquerella sp. 

Llnum lewisii

Linura sp.

Lupinus cf . argenteus 

Maohaeranthera canescens

Opuntia erinacea

Opuntia sp. 

Oryzopsib hymenoides

Penstemon sp.

cf. Petradoria puraila

Pharelia sp. 

Pinus flexilis

P. monophylla 

Pir.us sp.

Poaceae undet. 

PursMa triaeatata

Vegetation 

(relative 

abundance)

(2) 

(3)

(4)

(1) 

(1) 

(X)

(1) 

(2)

(1) 

(X)

(1) 

(2)

(1) 

(1) 

(X) 

(1) 

(X)

(2) 

(X)

(1)

(1) 

(X)

(1)

U

(X)

(X) 

(2)

Macrofossil assemblages 

sample number and count

ER-3(mod) ER-3(2) ER-3(3) ER-3(4) ER-3(6) ER-3(7) ER--3(8) 2 ER~3(8) ER-3(9) ER-3(10) ER--3(13)

I/ 38,700 I/ 11 45,000 I/ 37,800 I/ I/ I/

19 J46 358 150 210 456 328 293 129 167 85 

- 247 10 23 - 10 2 1 340 

387 - ___ _ _ ___

10 19 32 10 13 30 34 59 4 1 8

_________ 2 

200 195 294 260 231 198 316 224 516 120 

4---- 1361

1- - - ___

156 124 111 57 84 185 121 118 139 67 

---!----- - 

153 _ ___ _ - ___

1 - -i- - _._ i _ 

16 - 5 - 72 11 - -

_ _ _ - -

2 _____ 

-41-1- - 3 - - - 

12 21 13 18 5 30 20 12 12 48

21 67 14 1 9 24 10 4 - 

75 131 723 222 128 380 123 194 51 79 9

_ _ - 1

19 7 1 6 14 14 39 2 -

5___-_ _ _ i _ - 

_--- - ---399

1 4 432- 33 46 - -

17 - - 2 12 14 

26 2 2 14 9 3 - 81 10 297 

1- 1-1- ----- 

_ _ 12 - - _____ 

3 _ _ _ _ - _____ 

3 37 - 735 828 5 36 167 910 1,443 807 

79----- ____ i 

_ _- ____ i 

177 4 17 12 9 6 15 4 9 18 53 

1 1 - - - - _____
SUPPLEMENTAL DATA 81

TABLE 24. Plants from the Eleana Range <ER)-3 site Continued

Quercus gambelii

Rhus trilobata

Ribes cf. velutinum

Ribes sp.

Salvia coluinbariae

S. dorrii

Senecio multilobatus

Sphaeralcea sp.

Stanleya pinnata

Stipa sp.

Symphoricarpos longiflorus

Symphoricarpos sp.

Tetradymia sp.

NISP

N

N ts

g

Vegetation 

(relative

abundance)

2/

(1)

_

_

(X)

(X)

(1)

(1)

(X)

(2)

_

-

-

33

20

Macrofossil assemblages 

sample number and count

ER-3(mod) ER-3(2) ER-3(3) ER-3(4) ER-3(6) ER-3(7) 2 ER-3(8> 2 ER-3(8) ER--3(9) ER-3(10) ER-3(13)

2-_-_------

5 ----------

I - I - - - 1 - - -

!_4______

_

______ i

17 _________ i

__________

___ _ - - i _

__________

4 - 27 79 39 28 135 101 97 132 86

125 18 78 37 81 126 71 92 100 26

999 1,068 1,646 2,014 1,616 1,386 1,347 1,434 1,780 2,674 2,322

22 14 17 21 19 14 16 19 19 15 20

14 11 12 14 12 10 12 14 11 10 16

 Age uncertain, see table 6.

21

 Species in the vicinity, but more than 30 meters from the site.
82 VEGETATION AND CLIMATES OF THE LAST 45,000 YEARS, NEVADA TEST SITE

TABLE 25. Plants from the Eureka View (EV) fossil locality 1

[Macrofossil data are presented in terms of relative abundance classes; 5, very abundant; 4, abundant; 3, common; 2, occasional; 1, rare; 0, less than five fragments, 

a possible contaminant. B.P., before present; N, total number of plant taxa; Np, total number of woody perennials; IS, Sorensen's index of similarity 

between macrofossil assemblage and the modern plant community (using N); %, percent. Data from Spaulding (1980)]

Relative abundance of apecies 

in macrofossil assemblage

Approximate radiocarbon age

21 

2 / 

Species

Ambrosia dumos 

Amphipappus fremontii 

Amsinckia intermedia 

A- tesselata 

Amsinckia sp. 

Aristida adscensionis 

Artemisia sec. Tridentatae

Atriplex confertlfolia^

2/ 

Brickellia arguta 

Cheilanthes feeiChorizanthe cf. brevicornu

21 Chorizanthe cf. rigid a-'

cf. Chrysothamnus sp.

Echinocactus polycephalu

Encelia virginensis

21 Ephedra nevadensis 

Ephedra cf. viridis

2/

2,635+ 

140 B.P.

EV-4(1) EV-4 (2) EV-4 (3)

1,580+ 

140 B.P.

3,930+ 

180 B.P.

535+ 

150 B.P.

5,595+ 

210 B.P.

6,795+ 

190 B.P.

5,435+ 

220 B.P.

14,720+ 

530 B.P.

8,330+ 

250 B.P.

2/ 

Eriogonum inflatum 

E. fasciculatumEriogonum sp. 

Erloneuron pulchellum 

2/ Eucnide urens 

Euphorbia sp. 

Festuca sp.

Foresellesia nevadensis 

Gilla sp.-/ 

Gutierrezia microcephal

2 / 

Haplopappus brickellioides 

K. Iaricifoliui3 

Haplopappus sp. 

Hecastocleis shockleyi 

Juniperus osteosperma

2/

Larrea tridentat

Lepidium cf. fremontii

Lepidium sp.

Lycium sp.

cf. Machaeranthera sp.

Mirabilis sp.

Nama sp.-'

Nicotiana trigonophyll

Opuntia basllaris

(). echinocarpa

Opuntia sp.

Penstemon sp.

Peucephyllum schottii

21 Phacelia crenulata 

Phacelia sp.

21 

2f Physalis cf. crassifolia ' 

Pinus cf. flexilis 

Psorothamnus fremontii
SUPPLEMENTAL DATA 83 

TABLE 25. Plants from the Eureka View (EV) fossil locality Continued1

Relative abundance of species 

in inacrofossil assemblage

Salvia dorrii

cf. Sclerocactus sp.

Scopulophila rixfordiiSphaeralcea sp.

Stipa sp. 

Symphoricarpos cf. longiflorus

Tidestomia oblongifolia

2/ Viguiera retieulata 

N (26)

Np (15)

N /N (100) (58%) 

IS

EV-1 EV-2A

1

1

1 

3

19 18

12 8

63% 44% 

62 64

EV-2B

-

2 

22

13

59% 

58

EV-2C

1

1 

1

18

11

61% 

54

EV-3 EV-4(1)

1 1

1

2 

14 16

9 11

64% 69% 

50 38

EV-4(2) EV~4(3) EV-5A

- - 1 

1 

21- 

- - 1

- 1 - 

1

13 12 22

10 10 14

77% 77% 64% 

31 41 17

EV-5B

1

12

6

50% 

37

 In the northern Eureka Valley, Inyo County, California (1,390 to 1,555 meters; T. 7 S., R. 38 E., S^NW** sec. 23; Soldier Pass, 

California-Nevada 15" quadrangle).

2/ Plant species presently at site.

 Dominant plant species presently at site.

*U.S. GOVERNMENT PRINTING OFFICE.-1986 676-047/26010