Geologic and Hydrologic 

Characterization and Evaluation 

of the Basin and Range Province 

Relative to the Disposal 

of High-level Radioactive Waste 

Part III Geologic and Hydrologic Evaluation 

GEOLOGICAL SURVEY CIRCULAR 904-C 

This is Part III of a series of reports being prepared 

by the U.S. Geological Survey in consultation with 

States in the Basin and Range Province. 
BASIN AND RANGE 

Provice Working Group 

U.S. Geologi~al Survey Members 

Chairman of the Province Working Group: Member: 

M.S. Bedinger 

Hydrologist 

Water Resources Division 

Denver, CO 

ARIZONA 

Member: 

Larry D. Fellows 

Associate Director and State Geologist 

Arizona Bureau of Geology and Mineral 

Technology 

Thcson, AZ 

Alternate: 

H. Wesley Peirce 

Principal Geologist 

Arizona Bureau of Geology and Mineral 

Technology 

Thcson, AZ 

CALIFORNIA 

Member: 

Robert Streitz 

Geologist 

California Division of Mines and Geology 

Sacramento, CA 

IDAHO 

Member: 

Frank Sherman 

Chief, Ground-Water Section 

Idaho Department of Water Resources 

Boise, ID 

Alternate: 

Darrel Clapp 

Chief, Technical Services Bureau 

Idaho Department of Water Resources 

Boise, ID 

NEVADA 

Member: 

John Schilling 

State Geologist 

Nevada Bureau of Mines and Geology 

University of Nevada, Reno 

Reno, NV 

Alternate: 

Susan L. Tingley 

Deputy to the Director 

Nevada Bureau of Mines and Geology 

University of Nevada, Reno 

Reno, NV 

K.A. Sargent 

Geologist 

Gelogic Division 

Denver, CO 

State Memblers and Alternates I 

NEW MEXICO 

Member: 

Emery Arnold 

State Geologist 

New Mexico Mining and Minerals Division 

Santa Fe, NM 

Succeeded in July, 1982 by: 

James Hill 

State Geologist 

New Mexico Mining and Minerals Division 

Santa Fe, NM 

Alternate: 

Frank Kottlowski 

Director 

New Mexico Bureau of Mines and Mineral Resources 

Socorro, NM 

TEXAS 

Member: 

Christopher Henry 

Geologist 

Thxas Bureau of Economic Geology 

University of Texas at Austin 

Austin, TX 

Alternate: 

Douglas Ratcliff 

Associate Director 

Thxas Bureau of Economic Geology 

University of Texas at Austin 

Austin, TX 

UTAH 

Member: 

Genevieve Atwood 

State Geologist 

Utah Geological and Mineral Survey 

Salt Lake City, UT 

Alternate: 

Don R. Mabey 

Senior Geologist, Applied Geology 

Utah Geological and Mineral Survey 

Salt Lake City, UT 
Geologic and Hydrologic 

Characterization and Evaluation 

of the Basin and Range Province 

Relative to the Disposal 

of High-level Radioactive Waste 

Part III Geologic and Hydrologic Evaluation 

By M.S. Bedinger, K. A. Sargent and B. T. Brady 

GEOLOGICAL SURVEY CIRCULAR 904-C 

This is Part III of a series of reports being prepared 

by the U.S. Geological Survey in consultation with 

States in the Basin and Range Province. 
United States Department of the Interior 

WILLIAM P. CLARK, Secretary 

Geological Survey 

Dallas L. Peck, Director 

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1985 

Free on application to the Branch of Distribution, Eastern Region, U.S. Geological Survey, 604 South Pickett Street, Alexandria, VA 22304 
FIGURE 1. 

2. 

3. 

4. 

5. 

6. 

7. 

8. 

9. 

10. 

11. 

12. 

13. 

14. 

CONTENTS 

Page 

Summary............................................................. 1 

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

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Evaluation of Province subdivisions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . 2 

Trans-Pecos subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 

Rio Grande subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Southern Mexican Highlands subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Transition subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 

Sonoran Desert subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Salton Trough subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

Mojave subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 

Death Valley subprovince . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . 17 

White River subprovince. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 

Bonneville subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

Lahontan subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

Lake and Lava subprovince . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 

Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 

References cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 

ILLUSTRATIONS 

Page 

Map of Basin and Range Province as defined for this study showing extent and names of subprovinces. . . . . 3 

Map of the Trans-Pecos subprovince, New Mexico and Thxas, showing prospective areas for further study 4 

Map of the Rio Grande subprovince, New Mexico and Thxas, showing prospective areas for further study. . . 6 

Map of the Southern Mexican Highlands subprovince, Arizona and New Mexico, showing prospective 

areas for further study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

Map of the Transition subprovince, Arizona and New Mexico, showing prospective areas for further study. . . . . . 10 

Map of the Sonoran Desert subprovince, Arizona, California, and Nevada, showing prospective areas 

for further study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 

Map of the Salton Trough subprovince, California . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 

Map of the Mojave subprovince, California, showing prospective areas for further study . . . . . . . . . . . . . . . . 16 

Map of the Death Valley subprovince, California and Nevada, showing prospective areas for further study. . . . . . 18 

Map of the White River subprovince, Arizona, Nevada, and Utah, showing prospective areas for 

further study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 

Map of the Bonneville subprovince, Idaho, Nevada, and Utah, showing prospective areas for further study. . 22 

Map of the Lahontan subprovince, California, Nevada, and Oregon, showing prospective areas 

for further study . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 

Map of the Lake and Lava subprovince, California, Nevada, and Oregon . . . . . . . . . . . . . . . . . . . . 25 

Map of the Basin and Range Province showing prospective areas for further study . . . . . . . . . . . . . . . . . . . . 26 

III 
CONVERSION FACTORS 

Metric unit Conversion factor Metric/English unit 

square kilometers (km2) X 0.386 square mile ( mi2) 

meter (m) X 3.281 foot (ft) 

kilometer (m) X 0.621 mile (mi) 

millimeter (mm) X 0.039 inch 

IV 
Geologic and Hydrologic Characterization 

and Evaluation of the Basin and Range Province 

Relative to High-Level Radioactive Waste 

PART Ill 

GEOLOGIC AND HYDROLOGIC EVALUATION 

by M.S. Bedinger, K.A. Sargent, and B.T. Brady 

SUMMARY 

This report describes the first phase in evaluating the 

geology and hydrology of the Basin and Range Province for 

potential suitability of geohydrologic environments for isolation of high-level radioactive waste. The evaluation of the 

Province applies the guidelines, discussed in Part I (Bedinger, 

Sargent, and Reed, 1983) of this report to the geologic and 

hydrologic information compiled for the Province in Part II 

(Sargent and Bedinger, 1983). 

The geologic and hydrologic factors considered in the 

Province evaluation include distribution of potential host rocks, 

tectonic conditions and data on ground-water hydrology. Potential host media considered include argillaceous rocks, tuff, 

basaltic rocks, granitic rocks, evaporites, and the unsaturated 

zone. The tectonic factors considered are Quaternary faults, 

late Cenozoic volcanics, seismic activity, heat flow, and late 

Cenozoic rates of vertical uplift. Hydrologic conditions considered include length of flow path from potential host rocks to 

discharge areas, interbasin and geothermal flow systems and 

thick unsaturated sections as potential host media. 

The Basin and Range Province was divided into 12 

subprovinces; each subprovince is evaluated separately and 

prospective areas for further study are identified. About onehalf of the Province appears to have combinations of potential 

host rocks, tectonic conditions, and ground-water hydrology 

that merit consideration for further study. 

The prospective areas for further study in each subprovince 

are summarized in a brief list of the potentially favorable 

factors and the issues of concern. Data compiled for the entire 

Province do not permit a complete evaluation of the favorability 

for high-level waste isolation. The evaluations here are intended 

to identify broad regions that contain potential geohydrologic 

environments containing multiple natural barriers to radionuclide migration. 

1 

INTRODUCTION 

This report, the third of three parts, evaluates 

areas within the Basin and Range Province for 

their potential to contain geohydrologic environments suitable for isolation of high-level radioactive waste. Based on geologic and hydrologic factors, 

regions are identified that appear to warrant further investigation. Information used in evaluation 

includes distribution of potential host rocks, tectonic conditions, and ground-water hydrology. This 

and supplementary information on Pleistocene 

hydrologic features, are discussed in Part II (Sargent 

and Bedinger, 1983) of this report. References to 

reports and sources of information cited in the 

report on characterization of the geology and hydrology (Part II) are not repeated in this report (Part 

III). Evaluations follow the guidelines adopted by 

the Province Working Group described in Part I 

(Bedinger, Sargent, and Reed, 1983 ). 

The objective of this phase of evaluation is not to 

identify all prospective environments in the Basin 

and Range Province, but to identify regions of 

several thousands to several tens of thousands of 

square kilometers that appear promising for further study. The generalized data compiled for the 

Province evaluation stage will not permit complete 

evaluation of the factors being considered. For 

example; host-rock distribution is known principally from outcrops. Detailed evaluation would need 
data on subsurface distribution, thickness, depth, 

and physical properties. Another example is groundwater travel time. Time of ground-water flow from 

a point in the aquifer to the discharge area is a 

function of flow length, hydraulic conductivity, effective porosity, and hydraulic gradient. Of these, the 

principal data compiled for Province characterization were hydraulic gradient and length of flow 

path. 

ACKNOWLEDGMENTS 

The State members and alternates of the Province Working Group were the principal consultants 

and reviewers during the evaluation of geologic 

and hydrologic information and preparation of this 

report. In addition to the members of the Basin and 

Range Province Working Group and alternates, the 

following individuals are acknowledged for their 

assistance during various phases of preparation, 

compilation, and review of this report: John Hawley 

and William Stone of the New Mexico Bureau of 

Mines and Mineral Resources; and Robert B. 

Scarborough of the Arizona Bureau of Geology and 

Mineral Technology. Acknowledgment is given to 

Isaac Winograd, Newell Trask, Robert Schneider 

and George Dinwiddie of the U.S. Geological Survey 

for consultation during the process of Province 

evaluation and helpful suggestions and critical 

review of the report. 

EVALUATION OF 

PROVINCE SUBDIVISIONS 

The Basin and Range Province is herein divided 

into 12 subprovinces (fig. 1 ), that are convenient 

subdivisions for evaluating the geology and hydrology of the Province. Subprovinces are further subdivided into ground-water units, which in turn, are 

systematically numbered within each subprovince. 

The method used in defining ground-water units is 

described in Part II of this report (Sargent and 

Bedinger, 1983). The boundary of the Basin and 

Range Province, as used for this study, closely 

follows the physiographic province defined by 

Fenneman (1928). The boundary, as used here, follows the natural ground-water flow-unit boundaries that define most of the study area. 

TRANS-PECOS SUBPROVINCE 

The Trans-Pecos subprovince of Texas and New 

Mexico (fig. 2) includes basins tributary to the Rio 

Grande, and a large closed basin of interior drainage. 

2 

The bedrock includes Precambrian basement rocks, 

Paleozoic and Cretaceous sedimentary rocks, and 

Tertiary volcanic and intrusive rocks. Structurally, 

this subprovince is transitional between the nearhorizontal Paleozoic rocks of the interior craton to 

the east, and the complex structure of the Basin 

and Range Province to the west. 

Granite and syenite occur both as deep-seated 

masses and laccoliths. The deep-seated masses may 

be potential host rocks in the saturated and unsaturated zones. Near-surface bodies, such as laccoliths, 

may be potential host rocks in the unsaturated 

zone. Shale beds of Permian, Upper Cretaceous, 

and lower Tertiary age crop out in the subprovince. 

Argillaceous rocks as thick as 460 meters ( 1,500 

feet) occur in units 0101 and 0102. Ash-flow tuff 

beds are thin, generally less than 20 meters ( 65 

feet); however, within caldera collapse zones, thicknesses as great as 800 meters (2,600 feet) have been 

reported in unit 0103. Individual basalt flows generally are less than 15 meters (50 feet) thick, but 

locally, aggregate thicknesses of basalt flows may 

be about 150 meters (500 feet). Evaporites occur as 

interbeds of the Yeso Formation of Permian age in 

the northern part of unit 0104, and as bolson deposits of Tertiary and Quaternary age in the Salt Basin 

(unit 0104). 

Much of the subprovince appears to be relatively 

stable as evidenced by little seismic activity and 

heat flow, slow rate of vertical movement ( 1 to 2 

meters or 3 to 6 feet per 10,000 years), absence of 

Quaternary volcanic rocks, and few mapped Quaternary faults; however, data are limited for the 

subprovince. Reilinger, Brown, and Powers (1980) 

present releveling data that indicate tectonic uplift 

in the Diablo Plateau east of El Paso (unit 0104). 

Long flow paths from potential host rocks near 

and at the boundaries of basins to natural discharge areas or ground-water withdrawal areas may 

be indicative of long flow times. Ground water is 

withdrawn for irrigation in many basin-fill areas. 

Locally, ground-water use is limited because of 

saline water (dissolved-solids concentrations greater than 1,000 milligrams per liter) in basin fill. 

Interbasin ground-water flow from unit 0104 is 

inferred to occur both eastward into the Pecos River basin, and westward into the narrow sections of 

unit 0103 bordering the Rio Grande. These interbasin 

flows are inferred by Gates and others ( 1980), on 

the basis of water-budget data, and the presence of 

a water-table depression on the west side of unit 

0104. This depression is not due to pumping and is 
~ 

12 

LAKE AND LA V ~ 

SUBPROVINCE 

06 

.,. 10 BONNEVILLE 

• SUBPROVINCE 

0 100 200 300 400 500 KILOMETERS 

09 WHITE RIVER _.__,__ __ SUBPROVINCE 

03 .SOUTHERN MEXICAN 

HIGHLANDS SUBPROVINCE 

0 100 200 300 MILES 

MEXICO 

01 TRANS-PECOS 

~SUBPROVINCE 

30° 

FIGURE 1.-Map of the Basin and Range Province as defined for this study showing extent and names of subprovinces. 
0 

I 

100 200 300 400 500 KILOMETERS I I I I I I •' 

0 100 200 300 MILES 

FIGURE 2.-The Trans-Pecos subprovince, New Mexico and 

Texas, showing prospective areas (shaded) for further 

study. Ground-water units are numbered; the first two 

digits refer to the subprovince; the second two digits 

are unique for each ground-water unit within the subprovince. Arrows indicate the general direction of ground4 

water flow at the water table; black areas are natural 

discharge areas; dashed lines are streams that receive 

ground-water discharge. Areas outlined by solid hachured 

lines are areas or significant ground-water withdrawal 

by wells, or in unit 0104, a natural depression in the 

water table (noted by*). 
presumed to indicate downward flow from the watertable aquifer to deeper aquifers. 

The unsaturated zone is greater than 150 meters 

(500 feet) thick in parts of the subprovince. Large 

areas with a thick unsaturated zone underlie the 

northern part of unit 0104, and occur under the 

topographically higher parts of units 0101, 0102, 

and 0103. 

The statements in the following table pertain to 

units 0101 and 0102, part of unit 0103, and parts of 

unit 0104 (shaded in figure 2), which appear to 

merit consideration for further study: 

Potentially favorable factors 

• Potential host media include saturated and unsaturated 

intrusive plutonic granite and syenite. Locally, tuff and 

basalt may be potential host rocks in the unsaturated zone. 

• Available mapping and data indicate regionally little heat 

flow, vertical movement, and seismicity; few Quaternary 

faults, absence of Quaternary volcanic activity. 

• Little tectonic activity and studies showing slow rates of 

vertical uplift would appear to indicate slow denudation 

rates. 

• Long flow paths from ground-water divides to natural 

discharge areas and areas of large ground-water withdrawal. 

• Small ground water yields would be expected from igneous 

intrusive rocks. 

Issues of concern 

• Problems in differentiating shallow laccolithic intrusive 

bodies from plutonic masses. 

• Areas of Quaternary faulting, recent uplift and seismicity 

have been identified and need to be studied further to 

determine the extent of tectonic activity. 

• Natural flow paths may be shortened by ground-water 

withdrawal. 

• Complicated geology in the Marathon fold belt (unit 0101) 

and the Chihuahua tectonic belt (unit 0103) present problems in defining the geohydrologic framework of the 

subprovince. 

In the central part of unit 0104, and in that part 

of unit 0103 bordered on the west by the Rio Grande and on the east by unit 0104, ground-water flow 

paths are relatively short, and ground-water withdrawal is locally large. Ground-water flow is not 

well-defined where interbasin flow is inferred to 

occur from unit 0104. These areas are considered to 

be less favorable for further study. 

RIO GRANDE SUBPROVINCE 

The Rio Grande subprovince of New Mexico and 

Texas (fig. 3) follows the structural trough that 

extends from Mexico into Colorado. The subprovince 

includes the broad alluvial valley of the Rio Grande, 

and its adjacent uplands, composed largely of 

5 

Paleozoic sedimentary and Cenozoic intrusive and 

extrusive rocks. The subprovince includes, east of 

the Rio Grande, three structural basins-the J omada 

del Muerto in the central part of unit 0203, the 

Estancia basin in unit 0202, and the Tularosa basin 

in unit 0201. The Jornada del Muerto is a broad, 

elongate synclinal basin of Paleozoic and Mesozoic 

sedimentary rocks overlain by deposits of Tertiary 

and Quaternary age. The Estancia basin is a topographically closed synclinal basin, bordered on the 

east and west by Precambrian crystalline rocks 

overlain by sedimentary rocks of Paleozoic age and 

basin fill of Quaternary and probably Thrtiary age. 

South of the Estancia basin is the Tularosa basin, 

an elongated graben bounded by Paleozoic rocks of 

the San Andres Mountains on the west and the 

Sacramento Mountains on the east. The basin fill is 

of late Thrtiary and Quaternary age. The Tularosa 

basin extends southward to the Rio Grande at the 

Texas-Mexico border. Surface drainage in the central part of the basin is closed; ground-water discharge is by evapotranspiration in the central part 

of the basin, seepage to the Rio Grande, and withdrawal by wells in the vicinity of El Paso. Surface 

drainage of units 0203 and 0204, bordering the Rio 

Grande, is to that river. 

Precambrian and Thrtiary granitic rocks and structurally complex Precambrian metamorphic rocks 

crop out in the mountains along the common border 

of units 0201 and 0203. Tertiary granitic rocks crop 

out in unit 0201, and Precambrian granitic rocks 

crop out in unit 0202 and in the northern part of unit 

0203. Scattered Precambrian and Thrtiary granitic 

rocks crop out west of the Rio Grande in unit 0204. 

Shale of Paleozoic and Mesozoic age crop out in 

the subprovince. Argillaceous rocks with some 

interbedded coarser clastic units are as thick as 550 

meters ( 1,800 feet). Broad facies changes are common in the shale units. Thin-bedded marine evaporites occur in the rocks of Permian age in all units. 

Saline ground water is found in association with 

these evaporites. 

Laharic breccia ranging in thickness from 600 to 

1,070 meters (2,000 to 3,500 feet) occurs in units 

0203 and 0204, and may be a potential host rock 

with confining and sorptive barriers to flow of water 

and radionuclides. Ash-flow tuff of Oligocene age is 

believed to be as thick as 900 meters (3,000 feet) in 

units 0203 and 0204, where it is associated with 

calderas. Basaltic rocks, as much as 240 meters 

( 800 feet) thick are sparsely distributed in unit 

0204. 

Thctonic activity in the Rio Grande subprovince 
0 

I 

0 

FIGURE 3.-The Rio Grande subprovince. New Mexico and 

Texas, showing prospective areas (shaded) for further 

study. Ground-water units are numbered; the first two 

digits refer to the subprovince; the second two digits 

are unique for each ground-water unit within the sub6 

------32° 

province. Arrows indicate the general direction of groundwater flow at the water table; black areas are natural discharge areas; dashed lines are streams that receive groundwater discharge. Area outlined by solid hachured line is 

area of significant ground-water withdrawal by wells. 
presumably is related to the Rio Grande rift. The 

principal evidence of this tectonic activity is the 

significant density of Quaternary faults and seismic epicenters in the northern parts of 0203 and 

0204; the significant heat flow (greater than 2.5 

heat-flow units) in the southern part of units 0203 

and 0204; and occurrence of basalt of late Cenozoic 

age in the central parts of unit 0203 and the southern parts of units 0203 and 0204. Reiter, Shearer, 

and Edwards ( 1978) consider geothermal anomalies along the Rio Grande rift evidence of underlying magma bodies. Reilinger and Oliver ( 1976 ), and 

Reilinger and others ( 1980) have ascribed the crustal doming observed in the Socorro area to activity 

of an underlying magma body. Rates of uplift are 

slow ( 1 to 2 meters or 3 to 6 feet per 10,000 years) in 

most of the subprovince. East of the Rio Grande, a 

narrow zone of Quaternary faults parallels the western boundary of unit 0201. Several Quaternary basalt 

vents occur in the northern one-half of unit 0201. 

Thermal springs and wells in the Rio Grande valley 

(units 0201, 0203, and 0204) are evidence of discharge at the surface and to basin fill from hydrothermal convection systems related to the significant 

heat flow in the Rio Grande rift. 

Ground-water quality is variable and in much of 

the subprovince the water is saline. West of the 

river (unit 0204), the ground water generally contains less than 500 mg/L (milligrams per liter) of 

dissolved solids; east of the river in unit 0203, the 

ground water generally contains 500 to 1,000 mg/L 

of dissolved solids. In the central part of unit 0203, 

the Jornada del Muerto, the dissolved-solids concentrations commonly range from 2,000 to 5,000 

mg/L. In units 0201 and 0202, the dissolved-solids 

concentrations generally range from 500 to 5,000 

mg/L and are as much as 25,000 mg/L in unit 0201. 

The large dissolved-solids concentrations of the 

water in much of the Rio Grande subprovince are 

derived from solution of marine evaporites in the 

Paleozoic and Mesozoic bedrock. Saline ground water 

in many parts of the subprovince has limited large 

ground-water withdrawals. Ground-water withdrawal is greatest from basin fill near El Paso and from 

alluvium and basin fill in the irrigated parts of the 

Rio Grande Valley. 

Ground-water flow paths from potential host rocks 

near ground-water divides to natural discharge areas 

in units 0201 and 0203 are relatively long and flow 

times are possibly very long. Unsaturated zones 

are thick (greater than 150 meters or 500 feet) in 

many areas throughout the subprovince. Granitic 

7 

rocks occur in the thick unsaturated sections in 

parts of unit 0201. 

Pleistocene Lake Otero occupied the playa of 

unit 0201. If pluvial conditions recur, a significant 

change in the ground-water flow regime in unit 

(0201) may be an increase in height of the groundwater divide south of the Lake Otero playa and a 

greater percentage of ground-water flow from the 

northern part of the unit discharged to the playa. 

Potential host rocks are granite, tuff, and laharic 

breccia in the saturated zone. These rocks also may 

have thick sections in the unsaturated zone. Areas 

containing potential host rocks with little tectonic 

activity, saline ground water, and long flow paths 

from potential host media to natural discharge areas 

are prospective units for further study. Unit 0204 

and the northern and southern parts of unit 0203 

are less suited for further study because of fewer 

occurrences of potential host rocks, significant heat 

flow, and greater tectonic activity. 

The statements in the following table summarize 

the favorable conditions and the issues of concern 

for units 0201 and 0202, and the central two-thirds 

of unit 0203 (shaded areas in figure 3): 

Potentially favorable factors 

• Potential host rocks are in saturated and unsaturated 

zones. 

• Tectonic activity generally is low as characterized by little 

seismicity and heat flow, slow uplift rates, little late Cenozoic volcanic activity and few Quaternary faults. 

• Ground water commonly is saline in basin fill and sedimentary rocks; potential igneous host rocks have little permeability, consequently, there is minimal inducement for watersupply development. 

• Long natural flow paths from potential host rocks to natural discharge areas indicate potentially long travel times. 

Issues of concern 

• Potential hazard due to volcanic activity needs to be 

considered. 

• Quaternary faults, which are mapped locally, need to be 

studied and hazards assessed. 

• Ground water generally is saline, but may be used for some 

purposes. 

Ground-water unit 0204 and the northern and 

southern parts of unit 0203 are considered to have 

less potential for further study because of the relatively significant seismic activity and heat flow, 

density of Quaternary faulting, local rapid rate of 

uplift in 0204, and generally shorter flow paths 

from ground-water divides to areas of natural 

discharge. 
SOUTHERN MEXICAN HIGHLANDS SUBPROVINCE 

The Southern Mexican Highlands subprovince 

of Arizona and New Mexico (fig. 4) consists of 

well-defined northwest-trending mountain ranges 

separated by wide valleys. The mountain ranges 

consist of Precambrian and Paleozoic rocks intruded by Mesozoic and Tertiary granitic stocks and 

plugs, that are partly overlain by marine and nonmarine sedimentary rocks of Cretaceous age, volcanic rocks of Tertiary age, and extensive basin-fill 

deposits of late Cenozoic age. Several of the topographically-closed basins in southeast Arizona and 

southwest New Mexico extend into Mexico. 

Granite and other intrusive crystalline masses of 

Precambrian and Tertiary age occur throughout 

much of the subprovince. Basaltic rocks are common locally, but generally are less than 50 meters 

( 150 feet) thick. Tuff is widespread, but only locally 

is of sufficient thickness to be considered a possible 

host rock. Tuff, which is 100 meters (330 feet) or 

more thick and that may warrant further study, is 

common in and near the calderas in units 0301, 

0302, 0303, 0304, 0305, 0306, and 0307. Laharic 

mudflow breccia, commonly 150 to 300 meters ( 500 

to 1,000 feet) thick, in units 0304 and 0306 may 

have potential for study as a host rock. Locally, 

shale occurs in thicknesses or 150 meters ( 500 feet) 

or more. Further study of shale would be needed to 

determine if it could be considered a potential host 

rock. Extensive anhydrite, gypsum, and possible 

salt deposits have been penetrated by drill holes 

near Safford (units 0306 and 0309), but the extent 

of the deposits are incompletely known from drilling data at this time (Peirce, 1981). 

Heat flow generally is less than 2.5 HFU (heat· 

flow units) except in parts of units 0301, 0302, and 

0303. However, local high-temperature [90° to 150° 

C (Celsius)] hydrothermal-convection systems are 

indicated by springs in units 0304 and 0306. Seis· 

micity and vertical uplift are low. Quaternary faults 

are sparse but widely distributed in the subprovince. 

Volcanic rocks of late Cenozoic age, generally of 

minor areal extent, have been mapped in units 

0301, 0302, 0304, 0305, and 0309. Tectonic condi· 

tions differ within the subprovince and tectonism 

generally is more intense in the New Mexico part of 

the subprovince. Long flow paths in most of the 

units indicate the possibility of long travel times, 

however, the potential for shortening of flow paths 

by development of water supplies from ground water 

8 

near ·potentially repository host media and the effect 

of recurrence of pluvial conditions need to be 

considered. Wilcox Playa (unit 0307) contained a 

lake and Lake Animas occupied the playa in unit 

0304 in Pleistocene time. Ground water generally is 

fresh except in the playa areas. The unsaturated 

zone has a thickness of 150 meters ( 500 feet) or 

greater principally on and near topographic divides 

in the Arizona part of the subprovince, whereas few 

occurrences of the unsaturated zone as great as 150 

meters ( 500 feet) are known to occur in the New 

Mexico part of the subprovince. 

Units 0301, 0303, 0304, 0306, 0307, 0308, and 

0310 (shaded areas in figure 4) are considered the 

best prospects for further study. Factors affecting 

their suitability are summarized in the following 

table: 

Potentially favorable factors 

• Potential host rocks include intrusive igneous rocks, laharic 

breccia, basalt, and tuff. 

• Tectonic activity is low. 

• Unsaturated zone probably is of sufficient thickness and 

extent to be considered for further study in the Arizona 

part of the subprovince. 

• Potential travel times may be long based on the long flow 

paths from potential host rocks to natural-discharge areas. 

Issues of concern 

• Hazard from Quaternary faulting and igneous activity 

must be assessed; may be restrictive locally. 

• Long, natural flow paths would be shorted by withdrawal 

of ground water downgradient. 

• Recurrence of lakes during pluvial climate would shorten 

flow paths. 

Units 0302,0305, and 0309 (fig. 4) generally have 

shorter flow paths from potential host rocks to 

natural-discharge and withdrawal areas. In addition, 

units 0301, 0302, and 0305 extend across the United States-Mexico International border, and some 

ground-water flow in these units probably moves 

from the United States into Mexico. 

TRANSITION SUBPROVINCE 

The Transition subprovince of Arizona and New 

Mexico (fig. 5 ), extending 800 kilometers ( 500 miles) 

from near the Colorado River in Arizona to the Rio 

Grande trough in New Mexico, is a geological and 

topographical zone of transition between the higher Colorado Plateau to the north, and the lower 

basin and range structure to the south. In New 
0 

0 

-

>< w 

0309 j :E 

'-" 3: 33° 

w 

z 

MEXICO 

110° 

0 

I 

100 200 300 400 500 KILOMETERS I I I I 1 

I I I 

0 100 200 300 MILES 

FIGURE 4.-The Southern Mexican Highlands subprovince, 

Arizona and New Mexico, showing prospective areas 

(shaded) for further study. Ground-water units are 

numbered; the first two digits refer to the subprovince; 

the second two digits are unique for each ground-water 

9 

unit within the subprovince. Arrows indicate the general 

direction of ground-water flow at the water table; black 

areas are natural discharge areas; dashed lines are streams 

that receive ground-water discharge. Areas outlined by 

solid hachured lines are areas of significant ground-water 

withdrawal by wells. 
34° 

0 100 200 300 400 500 KILOMETERS 109° 

I I I I I I I I I 

0 100 200 300 MILES 

FIGURE 5.-The Transition subprovince, Arizona and New Mexico, showing prospective areas (shaded) for further study. Ground-water units are 

numbered; the first two digits refer to the subprovince; the second two digits are unique for each ground-water unit within the subprovince. 

Arrows indicate the general direction of ground-water flow at the water table; black areas are natural discharge areas; dashed lines are streams 

that receive ground-water discharge. 
Mexico, the Transition subprovince consists of a 

block-faulted lava plateau. In Arizona, the subprovince consists of a high southward-facing dissected escarpment of Precambrian crystalline rocks, 

Paleozoic and Mesozoic sedimentary rocks, and 

Tertiary lavas. Drainage in most of the Transition 

subprovince is well developed, and streams drain 

to the Gila River, except for one closed basin, the 

Plains of San Augustin (unit 0401) in New Mexico. 

Potential host rocks include granite, basalt, and 

tuff. Granitic rocks of primarily Precambrian age 

crop out in the central part of unit 0404 and in the 

southern part of unit 0402. Basalt and tuff outcrops are widespread throughout the subprovince. 

Tuff associated with calderas in the central and 

eastern part of the region (units 0401, 0402, 0403, 

and 0404) is as thick as 600 meters (2,000 feet). 

Extensive outcrops of Precambrian shale, probably 

less than 60 meters ( 200 feet) thick occur in unit 0404. 

Tectonic activity, though locally intense, generally is low. Quaternary faults have been mapped in 

units 0401, 0402, and 0404. Seismicity generally is 

moderate with maximum magnitude of a few earthquakes as large as 5 and 6. Heat flow is less than 2.5 

HFU, except in unit 0402. Local ground-water convection of heat flow is evidenced by hot springs 

in unit 0402 and 0403. Vertical uplift is less than 

2 meters (6 feet) per 10,000 years. Late Cenozoic 

volcanic activity is evidenced by lava flows and 

cinder cones in the northern parts of units 0401 and 

0403, and in unit 0404 adjacent to the Colorado 

Plateau. 

This subprovince generally is higher in elevation 

than adjacent parts of the Basin and Range Province, 

and receives greater precipitation. This results in 

greater recharge, integrated surface-drainage networks, and many streams that receive ground-water 

discharge. Two basins are closed: units 0401 and 

0406. Ground water in the Plains of San Augustin 

(unit 0401) may discharge in part within the basin 

by evapotranspiration. Large springs in unit 0403 

and in the Rio Grande basin (unit 0204 in the Rio 

Grande subprovince) are believed to represent 

interbasin flow from unit 0401 (John McLean and 

Robert Meyers, U.S. Geological Survey, oral commun., 1983 ). 

Ground-water quality generally is fresh and contains less than 500 mg/L of dissolved solids. Areas 

with saline ground water occur in the Verde River 

valley (western part of unit 0404 ), Gila River basin 

(unit 0402) and Salt River basin (eastern part of 

unit 0404). The unsaturated zone is believed to be 

11 

150 meters ( 500 feet) thick or greater in broad areas 

throughout the subprovince. During the Pleistocene 

Epoch, a lake occupying the playa of the Plains of 

San Augustin (unit 0401) had an areal extent of 

more than 1,000 square kilometers ( 400 square miles) 

and a water level more than 60 meters ( 200 feet) 

higher than the shallowest water level in the playa 

today. 

The northwestern part of unit 0404 and all of unit 

0401 (shaded in fig. 5) appears promising for further study, as summarized in the table below: 

Potentially favorable factors 

• Potential host rocks include unsaturated basalt and tuff; 

saturated and unsaturated granitic rocks. 

• Flow paths from potential host rocks to natural-discharge 

areas are long. 

• Quaternary faulting and seismic activity generally are low. 

Issues of concern 

• Ground water generally is fresh. 

• Interbasin flow of ground water from unit 0401 to units 

0403 and 0204 (Rio Grande subprovince) is not well known. 

• Hazard from volcanic activity needs to be assessed based 

on further study of upper Cenozoic volcanic rocks. 

• Hazards from seismic activity and faulting needs to be 

studied further. 

The unshaded part of the Transition subprovince 

(fig. 5) is considered to be less favorable for further 

study, because of generally short flow paths from 

potential host rocks to discharge areas, the prevalence of fresh ground water, and locally, areas affected by late Cenozoic volcanic activity. 

SONORAN DESERT SUBPROVINCE 

The Sonoran Desert subprovince of Arizona, California, and Nevada (fig. 6) includes basins in California, Nevada, and Arizona, many of which have 

surface drainage to the Colorado River. Many 

ground-water flow units in central Arizona terminate in depressions created by ground-water withdrawal. The mountain ranges are faulted blocks of 

Precambrian intrusive and metamorphic rocks, 

Mesozoic and Tertiary granitic intrusions and volcanic rocks. Basin fill, as thick as 3,000 meters 

(10,000 feet) and perhaps averaging 900 meters 

(3,000 feet) thick, ranges in age from middle Tertiary to Quaternary. 

Potential host rocks include granitic intrusive 

rocks and some metamorphic rocks in both the 

saturated and unsaturated zones. Granitic and other 

silicic to intermediate intrusive rocks of Precambrian, 

Mesozoic, and Tertiary age are widespread in the 
0 100 200 300 400 500 KILOMETERS I I I I I I 

0 100 zbo ~0 MILES 

FIGURE 6.-The Sonoran Desert subprovince, Arizona, 

California, and Nevada, showing prospective areas 

(shaded) for further study. Ground-water units are numbered; the first two digits refer to the subprovince; the 

second two digits are unique for each ground-water unit 

within the subprovince. Arrows indicate the general 

12 

direction of ground-water flow at the water table; black 

areas are natural discharge areas; dashed lines are streams 

that receive ground-water discharge. Areas outlined by 

solid hachured lines are areas of significant ground-water 

withdrawal by wells. 
subprovince. The Gunnery Range batholith of 

southwest Arizona, a particularly large body of 

quartz monzonite underlying about 40,000 square 

kilometers ( 15,000 square miles) of units 0507 and 

0523, has potential as a host media in the saturated 

and unsaturated zones. Basalt, tuff, basin fill, and 

possibly other rocks are potential host rocks in the 

unsaturated zones. Basalt crops out in sections 100 

meters (300 feet) or more thick in units 0531, 0534, 

and 0537 in California, and in the part of unit 0536 

in California. Basalt occurrences in Arizona and 

Nevada are generally less than 60 meters ( 200 feet) 

thick. Tuff greater than 90 meters (300 feet) thick 

occurs in California and Nevada in units 0531,0532 

and 0536. Occurrences of tuff in Arizona in units 

0503, 0508, 0515, 0516, 0517 and 0524 generally are 

less than 100 meters (330 feet) thick, but locally 

may be as much as 600 meters (2,000 feet) thick. 

Shale occurs in large outcrops, as great as 8 

square kilometers ( 30 square miles), in stratigraphic 

sections as thick as 140 meters ( 460 feet) in the 

southeastern part of the subprovince in Arizona in 

unit 0501. The shale, mostly Cretaceous in age, has 

undergone considerable tectonic deformation. Shale, 

mostly of Cambrian age, occurs as small scattered 

outcrops in California and Nevada. 

Thick evaporite deposits, mostly halite, occur in 

fault-block basins at Detrital Valley (unit 0530 ), 

Red Lake basin (unit 0528), and the Luke salt body 

(unit 0512) west of Phoenix. About 1,800 meters 

(5,900 feet) of anhydrite occur in the Picacho basin 

(units 0501 and 0502 ). Additionally, significant salt 

deposits may be present in the Higley basin (Peirce, 

1981) southeast of Phoenix (units 0505 and 0512). 

The region generally is low in seismicity, has few 

mapped Quaternary faults, and has a few late 

Cenozoic volcanic centers. Three poorly defined 

fault zones trend northward in Arizona. A cluster 

of faults occurs in unit 0536 (near Lake Mead) in 

Nevada and a concentration of faults is mapped in 

the western one-half of unit 0532 in California. 

There has been little recorded seismic activity in 

the subprovince; however, there are areas of many 

small earthquakes (such as the western part of unit 

0532) and a few epicenters of magnitude 5 and 6. 

Volcanic vents of late Cenozoic age are mapped in 

units 0532, 0534 and 0535 in California, and units 

0506, 0509, 0517, 0518, 0519 and 0524 in Arizona. 

Heat flow is between 1.5 and 2.5 HFU throughout 

the subprovince, and there are relatively few thermal 

springs in the subprovince. Vertical uplift is slight 

to moderate throughout most of the subprovince, 

although moderately rapid rates of uplift have been 

mapped in unit 0531 and the western part of unit 

0532 in California. 

Long natural flow paths exist from the groundwater divides to natural-discharge areas in many 

units. Concentrations of dissolved solids in ground 

water generally are less than 500 mg/L, but locally 

are greater in discharging playas. Withdrawal of 

water is large .in many ground-water units particularly in Arizona; withdrawal is nonexistent or 

negligible in some units in California and western 

Arizona. The unsaturated zone in many areas is 

greater than 150 meters (500 feet) thick. The thick 

unsaturated sections include both basin fill and 

bedrock. The surfaces drainage, except for Red 

Lake basin in unit 0528, is integrated and there is 

no evidence of pluvial lakes in the subprovince 

during the Pleistocene Epoch. 

The subprovince includes some of the more arid 

parts of the Basin and Range Province. Annual 

precipitation is as little as 10 centimeters ( 4 inches) 

or less and annual pan evaporation is as great as 

356 centimeters ( 140 inches). 

13 

Units that appear to have favorable combinations 

of potential host rocks, tectonic stability, and long 

flow paths for further study include units 0501, 

0503,0504,0507,0508,0509,0515,0516,0524,0525, 

0527, 0528, and 0530 in Arizona; units 0531, 0532 

(part), 0534, and 0535 in California, and unit 0536 

in California and Nevada. These areas are shaded 

in figure 6. Potentially favorable factors and issues 

of concern are summarized in the following table: 

Potentially favorable factors 

• Potential host media in the unsaturated or the saturated 

zones or both include granitic rocks, metamorphic rocks, 

tuff, basalt, and basin fill. 

• Long ground-water flow paths from potential host rocks in 

low permeability media indicate potential for long travel 

times to natural-discharge areas. 

• Tectonic activity is low as indicated by few seismic 

epicenters, and slow to moderate vertical uplift. 

• No evidence of Pleistocene lakes in the subprovince. 

• Crystalline igneous and metamorphic rocks yield small 

quantities of water to wells. 

• Precipitation is greatly exceeded by potential evapotranspiration. 
Issues of concern 

• Large ground-water withdrawals in some units result in 

shorter flow paths from ground-water divides to discharge 

areas. 

• Ground-water in most of the area is fresh. 

• Locally, hazards of seismic conditions, faulting, and volcanism need to be assessed. 

• Parts of western Arizona and California contain complex 

bedrock geology that is not well known. 

Units 0501, 0503, 0506, and 0523 are, in part, 

tributary to and extend across the International 

border with Mexico. Groundwater units 0526, 0529, 

0537, and units in central Arizona provide relatively short flow paths and limited outcrops of potential host rocks. 

SALTON TROUGH SUBPROVINCE 

The Salton Trough subprovince (fig. 7) of southem California is a large desert trough with a broad 

alluvial slope and delta plain. The trough is a northward extension of the basin in which lies the Gulf of 

California. The Salton Trough is bounded by mountain ranges on the northeast and on the southwest. 

The structural trough is open to the southeast 

where it is occupied by the Gulf of California. 

Granitic rocks are widespread in the ranges of 

the subprovince and are the primary potential host 

rocks. Small outcrops of basalt and tuff occur in the 

subprovince. 

Tectonically the subprovince is very active as 

evidenced by the numerous Quaternary faults, density of earthquake epicenters, Quaternary rhyolite 

occurrences, rapid rates of vertical movement, and 

significant heat flow. 

Relatively long flow paths from granitic intrusive rocks possibly provide long travel time to 

natural-discharge areas and areas of ground-water 

withdrawal in the basin fill. Thermal convective 

flow is substantiated by geothermal wells and 

springs in the subprovince. The water in much of 

the basin fill is saline. The thickness of the unsaturated zone may exceed 150 meters ( 500 feet) in the 

topographically higher parts of the mountain ranges. 

The trough was occupied by a large lake in the late 

Pleistocene with a maximum surface level116 meters 

( 380 feet) higher than at present. 

Flow paths from potential host rocks to the natural discharge areas may provide long flow times; 

however, due to the degree of tectonic activity, the 

subprovince as a whole generally is less favorable for 

14 

study than most other subprovinces. The following 

table summarizes the conditions in this subprovince: 

Potentially favorable factors 

• Potential host media primarily are granitic intrusive rocks 

in saturated and unsaturated zone. 

• Flow paths may provide long flow times from potential 

host rocks to discharge areas. 

Issues of concern 

• Subprovince is tectonically active. 

• Convective geothermal flow system in the subprovince is 

not defined. 

• The Salton Sea during the late Pleistocene was much larger; 

the water level was 116 meters ( 380 feet) higher than the 

present lake. During pluvial conditions, shorter flow paths 

from ground-water divides to natural discharge areas and 

less thickness and extent of the unsaturated zone may be 

inferred. 

MOJAVE SUBPROVINCE 

The Mojave subprovince of California (fig. 8) 

includes the Mojave River basin (in units 0703 and 

0707) and associated closed basins. The mountain 

ranges are mostly metamorphic rocks and granitic 

intrusions related to the Sierra Nevada batholith 

(west of the Basin and Range Province). The mountain ranges are irregular in outline and trend 

eastward, although major block-faulting trends 

northwestward. 

The primary potential host rock is Mesozoic 

granite. Basalt and shallow intrusives are of limited extent, but may be potential host rocks in the 

unsaturated zone. 

Tectonically this subprovince, located between 

the San Andreas fault (near southern boundary of 

the subprovince) and the Garlock fault (extends 

from westernmost part of unit 0707 through unit 

0709 into the Death Valley subprovince), is characterized by widespread, numerous Quaternary faults 

and seismic epicenters. Vertical movement is moderately great in the west to moderately low in the 

east. Heat flow in the subprovince generally is 1.5 

to 2.5 HFU. Quaternary faults and seismic epicenters are common in the western three-quarters of 

the subprovince, but only a few such features occur 

in the eastern one-quarter. Late Cenozoic volcanic 

activity is relatively common throughout. 

Flow paths from ground-water divides to naturaldischarge points and areas of withdrawal are long 

in many units, and indicate potentially long travel 

times. Ground-water withdrawal is large in many 

units. The water quality, generally suitable for most 

uses except in playa areas, does not preclude fur-
0 100 200 300 400 500 KILOMETERS 

I I I I I I I •• 

0 100 200 300 MILES 

FIGURE 7.-The Salton Trough subprovince, California. Ground-water units are numbered; 

the first two digits refer to the subprovince; the second two digits are unique for each 

ground-water unit within the subprovince. Arrows indicate the general direction of 

ground-water flow at the water table; black areas are natural discharge areas; dashed 

lines are streams that receive ground-water discharge. 

ther development in many units. Several of the 

playas were occupied by lakes or marshes in the 

late Pleistocene. Discharge of ground water is mostly internal to playas or to the Mojave River. 

Inter basin flow possibly occurs from unit 0703 into 

the Death Valley subprovince (Richard Moyle, U.S. 

Geological Survey, oral commun., 1982) Areas of 

unsaturated zone thicker than 150 meters ( 500 feet) 

15 

are widespread; the largest areas being present in 

the eastern part of the subprovince. 

The potential f.or further study of environments 

for storage of high-level radioactive waste is sharply contrasted between the eastern parts of units 

0702 and 0703, and the central and western part of 

the subprovince. The eastern parts of 0702 and 

0703 appear to have potential for further study 
0 100 200 300 400 500 KILOMETERS 

I I I I I I I •' 

0 100 200 300 MILES 

7 IGURE 8.-The Mojave subprovince, California, showing 

prospective areas (shaded) for further study. Groundwater units are numbered; the first two digits refer to 

the subprovince; the second two digits are unique for each 

ground-water unit within the subprovince. Arrows inbecause of generally low tectonic activity, common 

occurrence of granitic rocks, large areas of thick 

unsaturated zone, long flow paths, and minor 

ground-water withdrawal. 

16 

dicate the general direction of ground-water flow at the 

water table; black areas are natural discharge areas; 

dashed lines are streams that receive ground-water discharge areas ; outlined by solid hachured lines are areas 

of withdrawal by wells. 

Factors which have impact on the geohydrologic 

suitability for repository siting in the eastern parts 

of units 0702 and 0703 (shaded in figure 8 ), are 

summarized in the table below: 
Potentially favorable factors 

• Potential host rocks include granitic intrusive rocks in the 

saturated and unsaturated zones, and basalt, shallow 

intrusives, and basin fill in the unsaturated zone. 

• Quaternary faults and seismic epicenters are few; rates of 

vertical movement are moderate. 

• Long flow paths from potential host media to naturaldischarge areas provide prospectively long flow times 

through crystalline bedrock and fine-grained phases of the 

basin fill. 

Issues of concern 

• Hazards of tectonic activity needs to be assessed locally, 

especially volcanism. 

• Ground water is fresh, except in playa areas, and further 

development may occur. 

DEATH VALLEY SUBPROVINCE 

The Death Valley subprovince of California and 

Nevada (fig. 9) includes the large ground-water 

flow system that discharges in the Amargosa Desert, 

Death Valley, Owens Valley, and several smaller 

closed basins in California and Nevada. The mountain ranges are folded and faulted Precambrian and 

Paleozoic sedimentary rocks with some masses of 

deformed Mesozoic sedimentary rocks, and granitic intrusions, locally overlain by Tertiary and Quaternary volcanic rocks. 

Deep-seated granitic rocks, mostly of Mesozoic 

age with some of Tertiary and Precambrian age, are 

widespread. These rocks occur both above and below 

the water table within the depth considered for 

repositories. Basalt is common, particularly in California, 

and may be a prospective host rock in the unsaturated zone. Thick sequences of ash-flow tuff occur 

in and near calderas in the Nevada part of the 

subprovince. Shale and argillite of Precambrian 

and Paleozoic age crop out in the California part of 

the subprovince; middle Paleozoic shale occurs in 

the Nevada part of the subprovince. Thicknesses of 

undisturbed shale may be as great as 900 meters 

(3,000 feet); however, in most occurrences, the shale 

is structurally deformed, and may thin abruptly by 

faulting or folding. 

Tectonically the subprovince is dichotomous. The 

western part, including units 0804,0807,0811,0812, 

0813, 0814, and 0815, has numerous Quaternary 

faults and late Cenozoic volcanic activity, high heat 

flow, rapid rate of vertical uplift, and many seismic 

epicenters. In May 1982, the U.S. Geological Survey issued a "Notice of Potential Volcanic Hazard" 

for the Mammoth Lake area (in units 0807 and 

0815 ). The potential volcanic hazards in the Mam17 

moth Lake area are described by Miller and others, 

( 1982 ). In contrast, the eastern part of the subprovince 

is relatively inactive tectonically. Exceptions in the 

eastern part of the subprovince include Quaternary 

faults in units 0802, 0803, and 0808. Quaternary 

faults generally are sparsely mapped in each unit 

with greater concentrations locally. Aside from the 

numerous man-made earthquakes at the Nevada 

Test Site and the seismically active area in unit 

0809, the seismic activity in the eastern part of the 

subprovince is low. Volcanic activity of late Cenozoic age in the eastern part of the subprovince is 

limited to small occurrences in the central part of 

unit 0802. Heat flow in the eastern part of the 

subprovince generally is between 1.5 and 2.5 HFU 

and less than 1.5 HFU in the northern part of unit 

0802 and 0808. Lachenbruch and Sass ( 1977) and 

Sass and Lachenbruch (1982) attribute the heat 

flow of less than 1.5 HFU to convective flow of heat 

from the area by ground water. The area is underlain, 

in part, by a regional aquifer in carbonate rocks. A 

major discharge area for the carbonate aquifer system is in the Amargosa Desert in the southwest 

part of unit 0802 in Nevada, where thermal water 

discharges from many springs or is pumped from 

wells. 

Long ground-water flow paths indicate the possibility of long flow times in units 0802 through 0810. 

Ground water generally is fresh in upland areas 

and saline in playa areas. Water use is large in units 

0804 and 0807, indicating human access to parts of 

the flow systems before the flow reaches naturaldischarge areas. 

Parts of the subprovince receives as little as 10 

centimeters ( 4 inches) of precipitation which is greatly exceeded by potential evapotranspiration. In 

this arid climate, thick sections of unsaturated zone 

are widely disturbed and a potential environment 

for radioactive-waste disposal in the subprovince. 

The largest area and greatest known thickness of 

the unsaturated zone in the Basin and Range Province occurs in and near the Nevada Test Site in unit 

0802. Several basins in the subprovince were occupied by lakes during the late Pleistocene. The effect 

of large changes in water level during pluvial conditions must be considered in studying sites in the 

unsaturated zone. 

Several of the units, 0804, 0807, 0811, 0812, 0813, 

0814, and 0815, in the western part of the subprovince 

appear to be less favorable for study because of 

greater tectonic activity. The areas for which further information would be useful in evaluating geo-
0 100 200 300 400 500 KILOMETERS 

J I I 1 I I I I' 

0 100 200 300 MILES 

FIGURE 9.-The Death Valley subprovince, California and 

Nevada, showing prospective areas (shaded) for further 

study. Ground-water units are numbered; the first two 

digits refer to the subprovince; the second two digits are 

unique for each ground-water unit within the subprovince. 

18 

Arrows indicate the general direction of ground-water 

flow at the water table; black areas are natural discharge 

areas; dashed lines are streams that receive ground-water 

discharge. Areas outlined by solid hachured lines are of 

significant ground-water withdrawal by wells. 
hydrologic environments include units 0801, 0802, 

0803, 0805, 0806, 0808, 0809, and 0810 (shaded 

areas in figure 9 ). The potentially favorable factors 

and issues of concern for those units are summarized in the table below: 

Potentially favorable factors 

• Potential host media in both the saturated and unsaturated zones include tuff, basalt, granitic rocks, and basin fill. 

• Little tectonic activity in much of the northern part in 

Nevada and the southeastern part in California. 

• Ground-water flow paths are long from ground-water divides 

to natural discharge areas. 

• Dilution of wastes may be effected along some flow paths 

by large flow in underlying carbonate aquifer. 

• Precipitation is greatly exceeded by potential evapotranspiration. 

Issues of concern 

• Tectonic hazards need to be assessed locally. 

• Effect of changes in water level and length of flow paths 

during pluvial conditions need to be evaluated. 

WHITE RIVER SUBPROVINCE 

The White River subprovince of Arizona, Nevada 

and Utah (fig. 10) includes the White River and 

Muddy River basins as well as part of the Virgin 

River basin, all of which are tributary to the Colorado River (Lake Mead), and several topographically closed basins in central Nevada. The mountain 

ranges, many of which are more than 2,400 meters 

( 7,900 feet) above sea level, are north-trending ridges of complexly deformed Paleozoic rocks, consisting, 

in large part, of limestone and dolomite. Younger 

tuff and lava occur in the southern and western 

parts of the subprovince, and lie with angular discordance on the Paleozoic rocks. 

Granite and tuff are the most promising host 

rocks for further study. Thick sections of ash-flow 

tuff are common, especially in and near calderas. In 

many areas, tuff occurs where the depth to water is 

150 meters (500 feet) or greater. Granitic rocks 

occur in widespread, but sparse, outcrops in both 

the saturated and unsaturated zones. Shale of Paleozoic 

age is widespread, but most outcrops show structural complexities, and are doubtful prospects as 

relatively uniform, and minable host rock. 

Quaternary faults and seismic activity are common in the region, but neither is intense, except 

locally. Heat flow generally is less than 2.5 HFU. 

Quaternary volcanic centers occur in several units 

( 0901 and 0905 ). The rate of vertical uplift is moderately rapid. 

19 

Long travel times may exist in all ground-water 

units, but the moderate- to long-flow lengths of as 

much as 64 kilometers ( 40 miles) indicate the potential for long travel times in units 0902, 0908, 0909, 

0910, 0911, and 0912. Ground water generally is 

fresh, with dissolved-solids concentrations less than 

500 mg/L in upland areas and near ground-water 

divides. Dissolved-solids concentrations of ground 

water are as much as 5,000 mg/L in some naturaldischarge areas, and range from 1,000 to 5,000 

mg/L where associated with gypsum and anhydrite deposits in the bedrock, mainly in the southern part of the subprovince. 

Occurrences of granite and tuff in thick unsaturated zones are features worthy of further study as 

potential repository environments. Withdrawal points 

for ground water and recurrence of pluvial conditions may shorten flow paths from potential host 

rocks. Geothermal springs reflect relatively deep 

circulation of ground water. Pluvial lakes occupied 

several of the closed basins in the northern part of 

the subprovince in the late Pleistocene. 

All units appear to be favorable prospects for 

further study. Units 0902, 0908, 0909, 0910, 0911, 

and 0912 (shaded in fig. 10) appear slightly more 

favorable for further study than the others. The 

potentially favorable factors and issues of concern 

in these units are summarized in the following table: 

Potentially favorable factors 

• Rocks in unsaturated and saturated zones are prospective 

host media- potential host rocks include granitic rocks 

and ash-flow tuff. 

• Quaternary faults, late Cenozoic volcanism, and seismicity 

are not intense, except locally. 

• Long flow paths from ground-water divides to natural 

discharge areas exist in most units. 

• Dilution of wastes may occur along some flow paths because 

of large flow in underlying carbonate aquifer. 

Issues of concern 

• Quaternary faulting and seismic activity is locally intense 

and associated hazards need to be assessed. 

• Generally fresh water may be developed for water supplies. 

• Flow paths and flow times in the areas of multiple aquifers 

are not completely known and may be difficult to define. 

Units 0901, 0903, 0904, 0905, 0906, 0907 appear 

to be less favorable areas for further study because 

of fewer potential host rocks and shorter groundwater flow paths. 
0 100 200 300 400 500 KILOMETERS , I 'I I I I •' 

0 100 200 300 MILES 

FIGURE 10.-The White River subprovince, Arizona, Nevada 

and Utah, showing prospective areas (shaded) for further 

study. Ground-water units are numbered; the first two 

digits refer to the subprovince; the second two digits are 

unique for each ground-water unit within the subprovince. 

20 

Arrows indicate the general direction of ground-water 

flow at the water table; black areas are natural discharge 

areas; dashed lines are streams that receive groundwater discharge. 
BONNEVILLE SUBPROVINCE 

The Bonneville subprovince of Idaho, Nevada, 

and Utah (fig. 11) includes mostly closed drainage 

basins, as well as several basins tributary to the 

Snake River northwest of the subprovince in Idaho. 

Large closed basins include the Bonneville Salt 

Flat, Great Salt Lake, and the Sevier Desert. Smaller closed basins are included in the western and 

southern parts of the subprovince. 

The mountain ranges are complexly folded and 

faulted Paleozoic rocks that were divided into northtrending structural blocks by Tertiary and Quaternary faulting. In the southern part of the subprovince, 

volcanic rocks form large parts of some mountain 

ranges. In the northern part, volcanic rocks are 

young, and occur mostly in the basins. 

Potential host rocks include principally granitic 

rocks and ash-flow tuff. Basalt exceeding 100 meters 

( 330 feet) in aggregate thickness has been mapped 

in one area in unit 1003. Granite of Tertiary age is 

exposed in unit 1012 in Idaho; in units 1002, 1003, 

1005B, 1005D, 1005E, and 1010D in Utah; and in 

units 1005B, 1006 and 1007 in Nevada. 

Thin tuff, generally less than 60 meters ( 200 feet) 

thick, occurs in the Idaho part of the subprovince. 

However, tuff as thick as 900 meters (3,000 feet) 

occur in the southern part of the subprovince in 

units 1001, 1002, 1003, and 1005B. Undifferentiated volcanic rocks, including basalt flows and ashfall tuff, occur in unit 1005A. Laharic breccia greater 

than 600 meters (2,000 feet) thick has been reported in unit 1017 in Idaho. 

Argillaceous rocks occur widely in stratigraphic 

sequences 300 to 1,800 meters ( 1,000 to 6,000 feet) 

thick as shale, slate, and schist, but most are structurally deformed. A ~hick 1,500-meter (5,000-foot) 

section of evaporites was penetrated in two wells in 

unit 1005A at an initial depth of about 750 meters 

(2,500 feet). 

Tectonically, the zone bordering the eastern edge 

of the subprovince, along the Wasatch Range, and 

parts of Idaho are active. Hydrothermal convection systems discharging hot water (greater than 

90°C) occur mostly in the subprovince near the 

Wasatch Range and in the Raft River area (unit 

1012). In the center and western part of the subprovince, 

deep hydrothermal systems are indicated by warm 

(20° to 90°C) geothermal-spring discharges. Upper 

Cenozoic volcanic rocks occur in units 1002, 1005A, 

1012, 1016, and 1017. The western part of the subprovince 

is relatively inactive tectonically; Quaternary faults 

21 

and earthquake epicenters are sparse. Vertical uplift 

associated with isostatic rebound following the decline 

in water level of Pleistocene Lake Bonneville has 

been documented (Crittenden, 1963). 

The Bonneville subprovince contains some large 

ground-water flow systems discharging to large 

saline lakes and playas. Flow units in the western 

part of the subprovince generally contain the long 

flow paths with potentially long flow times and 

potential host rocks. Pleistocene Lake Bonneville 

extended over a large part of the subprovince at an 

elevation about 270 meters ( 890 feet) higher than 

the present Great Salt Lake. Many of the basin-fill 

areas are irrigated with ground water. Ground water 

is fresh outside the major natural discharge areas. 

Much of the subprovince has unfavorable prospects for further study because of the probable lack 

of potential host rocks and significant tectonic activity. 

Units 1003, 1005A (part), 1005B (part), 1005E (part), 

1006, 1007, 1008, and 1009 (shaded in fig. 11) are 

prospective areas for further study. The potentially 

favorable factors and issues of concern in these 

units are summarized in the following table: 

Potentially favorable factors 

• Potential host media includes the saturated and unsaturated zones in tuff, granitic rocks and basalt. 

• Tectonic activity is low, except locally. 

• Ground-water flow paths from potential host media to 

natural discharge areas are long. 

• Dilution of wastes may be effected by larger regional flow 

systems at depth. 

Issues of concern 

• Tectonic hazards are locally of concern and need to be 

addressed in further studies. 

• Interbasin flow is inferred to occur in carbonate rocks at 

depth; definition of deep flow and travel times from potential host rocks to discharge areas need to be defined. 

• Development of additional water supplies may shorten 

flow paths to accessible environment. 

• Effect of recurrence of pluvial conditions on ground-water 

travel time and extent of unsaturated zone needs to be 

further studied. 

Other units in the Bonneville subprovince are 

characterized by generally greater tectonic activity, 

locally high heat flow, absence of prospective host 

media, and relatively short flow paths to the accessible 

environment. A large part of the subprovince may 

be inundated by lakes during a recurrence of pluvial 

climate. 

It should be noted, that although ground-water 

flow paths are upward and flow paths are relatively 

short in the large ground-water discharge areasBonneville Salt Flat in unit 1005, Great Salt Lake 
0 

I 

0 

100 200 300 400 500 KILOMETERS 1 

16~ ~b0 1 3t0 MILES 

FIGURE 11.-The Bonneville subprovince, Idaho, Nevada, 

and Utah, showing prospective areas (shaded) for further 

study. Ground-water units are numbered; the first two 

digits refer to the subprovince; the second two digits are 

unique for each ground-water unit within the subprovince. 

22 

Arrows indicate the general direction of ground-water 

flow at the water table; black areas are natural discharge 

areas; dashed lines are streams that receive groundwater discharge. Areas outlined by solid hachured lines 

are areas of significant ground-water withdrawal by wells. 
basin in unit 1010, and much of the Sevier Desert in 

unit 1005A-the rate of ground-water movement 

at depths of 300 to 900 meters (1,000 to 3,000 feet) 

is probably very slow. The velocity at such depths 

is slow because of the small average flux density (a 

relatively slow discharge rate throughout a very 

large area), and the permeability of the fine-grained 

and evaporitic basin-fill sediments is low. Also, the 

fine-grained basin-fill sediments have a significant 

potential retardation rate for radionuclides. These 

generalizations are true to some degree for all discharging 

playa areas. In general, we have not considered 

playa discharging areas as favorable environments 

for waste isolation, one reason being the fact that 

longer travel times exist upgradient from the playas. 

LAHONTAN SUBPROVINCE 

The Lahontan subprovince of California, Nevada, 

and Oregon (fig. 12) encompasses the major interior drainage basins of northern and western Nevada, 

including the Humboldt, Truckee, and Walker Rivers, 

and several large discharging playas-Black Rock 

Desert, Smoke Creek Desert, Pyramid Lake, Dixie 

Valley, Walker Lake, and Carson Sink. The area of 

Pleistocene Lake Lahonton, as well as several small 

closed basins are within this subprovince. The mountain ranges are fault blocks of complexly folded and 

faulted Triassic and Jurassic sedimentary rocks 

overlain by Tertiary volcanic rocks. 

Potential host rocks in the subprovince include 

granitic rocks, basalt and ash-flow tuff. Granitic 

rocks are widespread, with most appearing to be 

extensions of the Sierra Nevada intrusion. Basalt 

and andesite are widespread, but individual flows 

commonly are less than 15 meters (50 feet) thick. 

Ash-flow tuff is not uniformly distributed, but occurs 

in thicknesses greater than 90 meters ( 300 feet) in 

units 1106, 1107, 1108, 1112, and 1117. 

Shales and other argillaceous rocks occur in the 

easternmost part of the subprovince in stratigraphic sections as thick as 1,800 meters (5,900 feet). 

Virtually all these units have been folded and 

thrust-faulted. 

Quaternary faulting and seismicity generally are 

great, particularly in the western part of the subprovince. 

Upper Cenozoic volcanic rocks have been mapped 

in units 1112 and 1119; volcanic rocks of possible 

Quaternary age occur in units 1117 and 1118. Heat 

flow is greater than 2.5 HFU, in the northern part 

of the subprovince, from the eastern margin of unit 

1112 to the western border of the subprovince. 

Hydrothermal convection systems with tempera23 

tures greater than 90°C are indicated by the many, 

widespread thermal springs in the subprovince. 

Rates of uplift are moderately rapid and may be 

related in part to isostatic rebound of late Pleistocene 

Lake Lahontan. Pleistocene Lake Lahontan, with a 

surface elevation about 270 meters (890 feet) above 

the present basin floor, covered an area of 22,000 

square kilometers (8,500 square miles). 

Flow paths as long as 60 kilometers (37 miles) 

may provide long travel times from ground-water 

divides to natural-discharge areas in bedrock of low 

permeability. 

The northern parts of units 1112 and 1117 (shaded 

in fig. 12) may be prospective areas for further 

study, as summarized below: 

Potentially favorable factors 

• Potential host media exists in saturated and unsaturated 

zones. 

• Tectonic activity generally is low. 

• Long flow paths from ground-water divides to naturaldischarge areas may provide long travel times. 

Issues of concern 

• Heat flow is greater than 2.5 HFU in part of the area, 

indicating possible tectonic instability. 

• Ground water is fresh in most of the area. 

• Extent and thickness of the unsaturated zone would be 

decreased by recurrence of pluvial cycle. 

The other ground-water units and the southern 

parts of units 1112 and 1117 of the Lahontan subprovince 

are considered less favorable for further study because 

of tectonic activity, including Quaternary faulting, 

areas of late Cenozoic volcanism, historic earthquake 

activity and high heat flow. Parts of the area are 

characterized by short ground-water flow paths 

and evidence indicating widespread inundation during 

pluvial climates. 

LAKE AND LAVA SUBPROVINCE 

The Lake and Lava subprovince of California, 

Nevada, and Oregon (fig. 13) is a young, blockfaulted lava plateau with perennial lakes and numerous volcanic centers. Tertiary and Quaternary lava 

flows principally are basaltic and andesitic in composition and are intercalated with some ash-flow 

tuff. Prominent scarps, as high as 750 meters (2,500 

feet), mark the block-faulted basins, many of which 

have perennial lakes. Exterior drainage from part 

of the region is by the Klamath and Pit Rivers; 

other basins in the region are drained internally to 

saline perennial lakes, or ephemeral playa lakes 

having mud-salt flats. 
0 100 200 300 400 500 KILOMETERS 

I I I I I I ;' 

0 tOO 200 300 MILES 

FIGURE 12.-The Lahontan subprovince, California, 

Nevada, and Oregon, showing prospective areas (shaded) 

for further study. Ground-water units are umbered; the 

first two digits refer to the subprovince; the second two 

digits are unique for each ground-water unit within the 

Potential host rocks primarily include basalt and 

small outcrops of ash-flow tuff. Granitic rocks are 

limited to a few relatively small outcrops. Unsaturated sections thicker than 150 meters ( 500 feet) 

are limited in extent. 

24 

subprovince. Arrows indicate the general direction of 

ground-water flow at the water table; black areas are 

natural discharge areas; dashed lines are streams that 

receive ground-water discharge. 

Upper Cenozoic volcanic rocks are widespread 

west of 121° West longitude. Seismic activity and 

faulting are locally intense. Heat flow is greater 

than average for the subprovince ranging from 1.5 

to more than 2.5 HFU. Hydrothermal convection 
121° 119° 

\I 

121~ """ 

1214 r:.RNh~ ~AKE r\ 43° 

~- \ 

0 100 200 300 400 500 KILOMETERS I I I I I I I ,. 

0 100 200 300 MILES 

FIGURE 13.-The Lake and Lava subprovince, California, 

Nevada, and Oregon. Ground-water units are numbered; 

the first two digits refer to the subprovince; the second 

two digits are unique for each ground-water unit within 

the subprovince. Arrows indicate the general direction 

systems are indicated by the widespread occurrence of spring discharge with temperatures greater than 90°C. Rates of vertical uplift are 4 to 6 

meters (13 to 20 feet) per 10,000 years. 

Flow systems are in volcanic rocks and basin fill. 

Volcanic rocks, primarily basalt and basaltic andesite commonly are aquifers, and are inhomogeneous 

and difficult to delineate. Flow lengths from divides 

to natural discharge areas commonly are less than 

24 kilometers ( 15 miles). Flow times in largely per25 

of ground-water flow at the water table; black areas are 

natural discharge areas; dashed lines are streams that 

receive ground-water discharge. Areas outlined by solid 

hachured lines are areas of significant ground-water 

withdrawal by wells. 

meable basaltic rocks are probably not long. Ground 

water generally is fresh, dissolved-solids concentrations generally are less than 500 mg/L, except near 

playa lakes. The closed basins were occupied by 

pluvial lakes during the Pleistocene Epoch. 

The region contains limited areas favorable for 

further study because of the general lack of rocks 

for isolation of waste, commonly short groundwater flow paths, and tectonic activity in part of 

the subprovince. It is concluded that the subprovince 
12Q0 

0 

I 

0 

100 200 

•' I I 

100 

300 400 500 KILOMETERS 

I I ·, 

200 300 MILES 

FIGURE 14.-Prospective areas (shaded) for further study. 

is a relatively unfavorable prospect for further study, 

as summarized in the following table: 

Potentially favorable factors 

• Host media, though limited in extent, occur in both the 

saturated and unsaturated zones. 

• Tectonic activity is low in eastern part of subprovince. 

• A few long flow paths exist from prospective host rocks to 

natural discharge areas. 

Issues of concern 

• Granitic rocks are of very limited extent. 

• Unsaturated zone is of limited extent. 

• Tectonic activity very great locally, including extensive 

late Cenozoic volcanism in the western part of the subprovince. 

• Aquifers in basalt are difficult to define; flow times possibly are short. 

26 

CONCLUSIONS 

The preceding sections evaluate the subprovinces 

of the Basin and Range Province with the objective 

of identifying large areas that appear to be prospective for further study. It is repeated from Part I of 

this report (Bedinger, Sargent, and Reed, 1983) 

that evaluation cannot be made on the basis of 

individual factors alone. The ultimate evaluation of 

an environment needs to recognize the interrelationships of all factors and the effect of each in 

providing multiple barriers in an integrated system. 

The evaluations here identify geohydrologic environments in large areas that may contain potential 

repository sites and multiple barriers to radionuclide migration. A summary of the areas believed 
to be prospective for further study is shown in 

figure 14. In the next phase of this study, selected 

areas will be examined further. 

REFERENCES CITED 

Bedinger, M.S., Sargent, K.A., and Reed, J.E., 1983, Geologic and hydrologic characterization and evaluation of 

the Basin and Range Province, relative to the disposal 

of high-level radioactive waste-Part I, Introduction 

and guidelines: U.S. Geological Survey Circular 904-A, 

16 p., 1984. 

Crittenden, M.D., Jr., 1963, New data on the isostatic deformation of Lake Bonneville: U.S. Geological Survey 

Professional Paper 454-E, p. El-E31. 

Fenneman, N.M., 1938, Physiographic divisions of the 

United States (3rd ed. ): Annals of the Association of 

American Geographers, v. 18, no. 4, p. 264-353. 

Gates, J.S., White, D.E., Stanley, W.D., and Ackerman, 

H.D., 1980, Availability of fresh and slightly saline 

ground water in the basins of westernmost Texas: Texas 

Department of Water Resources Report 256, 108 p. 

Lachenbruch, A.H., and Sass, J.H., 1977, Heat flow in the 

United States and the thermal regime of the crust, in 

Heacook, J.G., ed., Nature and physical properties of 

the Earth's crust: American Geophysical Union, Geophysical Monograph 20, p. 626-675. 

Miller, C.D., Mullineaux, D.R., Crandell, D.R., and Bailey, 

R.A., 1982, Potential hazards from future volcanic 

27 

eruptions in the Long Valley-Mono Lake area, eastcentral California and southwest Nevada-A preliminary assessment to U.S. Geological Survey Circular 

877, lOp. 

Peirce, H.W., 1981, Major Arizona salt deposits: Arizona 

Bureau of Geology and Mineral Technology, Fieldnotes, 

v. 11, no. 4, p. 1-4. 

Reilinger, Robert, Brown, Larry, and PowPrs, Dennis, 1980, 

New evidence for tectonic uplift in the Diablo Plateau 

region, west Texas: Geophysical Research Letters, v. 7, 

no. 3, p. 181-184. 

Reilinger, Robert, and Oliver, Jack, 1976, Modern uplift 

associated with a proposed magma body in the vicinity 

of Socorro, New Mexico: Geology, v. 4, p. 583-586. 

Reilinger, Robert, Oliver, Jack, Brown, Larry, Sanford, Allan, 

and Balazs, Emery, 1980, New measurements of crustal 

doming over the Socorro magma body, New Mexico: 

Geology, v.8, p. 291-295. 

Reiter, Marshal, Shearer, Charles, and Edwards, C.L., 1978, 

Geothermal anomalies along the Rio Grande rift in 

New Mexico: Geology, v. 6, p. 85-88. 

Sargent, K.A., and Bedinger, M.S., 1983, Geologic and 

hydrologic characterization and evaluation of the Basin 

and Range Province, relative to the disposal of highlevel radioactive waste-Part II, Geologic and hydrologic characterization: U.S. Geological Survey OpenFile Report 82-973, 30 p. 

Sass, J .H., and Lachenburch, A.H., 1982, Preliminary 

interpretation of thermal data from the Nevada Test 

Site: U.S. Geological Survey Open-File Report 82-973, 

30 p. 

*U.S. GOVERNMENT PRINTING OFFICE:1985-576-049 I 20022