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FAULT

HEN

SPRING

CANYON CABIN

FAULT

GEOLOGIC QUADRANGLE MAP

RIVERSIDE QUADRANGLE, NEVADA

GQ–1770 (SHEET 1 OF 2)

Any use of trade names in this publication is for

descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey

For sale by U.S. Geological Survey Information Services

Box 25286, Federal Center, Denver, CO 80225

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

Qymm

emgg

emgg

emgg

emgg

emgy

emgy

emkp

emkp emkp

emkp

emkp

emgw

emgw

emgw

emgw

emsr

emsr

emsr

emsr emsr emsr

emsr

Xggn

Xggn

Xggn

Xggn

Xggn

Xggn

Xggn

Xggn

Xa

Xa

Xa

Xa

Xa

Xgrgn

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qan

Qot

Qot

ed

ed

ed

ed

ed

ed

Dsv

Dsv

Dsv

Dsv

Dsv

Dsv

Dsv Dsv

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Tab

Ym

Pkh

Pkh

emh

emh

emh

emh

emh

emh

Ygr

Ygr

Phb Phb

Phb

Phb

Phb

Phb

Phb

emst

emst

emst

emst

emst

emst

emst

el

el

el

el

el

eb

eb

eb

eb

eb

eb

Xgn

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Xgn

Xgn

Xgn

Xgn

Xgn

Xgn

Xgn

Xqm

Xqm

Xqm

Xqm

Xqm

Xqm

Xs

Qsv

Tmc

Tmc

Tmc

Tmc

Tmc

Tmc

Tmc

Tmc

Tmc

Tmc

Tmc

Qmt

Qymt

Qys

Qys

Qys

Qe

Qe

Qe

Qe

Qe

Qav

Qav

Qav

Qav

QTv

QTv

QTv

QTv

Qyms

Qyms

Qyms

Qgv

Qfv

Qfv

Qfv

Qfv

Qfv

Qtv

Qtv

Qtv

Qtv

Qyt

Qmt

Qyv

Qyv

Qyv

Qyv

Qyv

Qyv

et

et

et

et

et

et

et

et

et

et

et

et

Qym

Qym

Qym

Qym

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Tmca

ec

ec

ec

ec

ec

ec

Qs

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Qom

Qom

Qom

Pkfm

Ptwr

Ptbc

Ptbc

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Pe

Pe

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Mm

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Mm

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MDsc

MDsc

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MDsc

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en

en

en

en

Qc

Qc

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Qc

Qc

Qc

Qc

Qc

Qc

Qc Qc

Qc

Qc

Qc

Qc

Qc

Qc

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Qyms

Qsv

Qsv

Qsv

Qan

Qan

Qan

Qmm

Qymm

Tab

Tab

Tab

Pts

Pkfm

el

emh

Xgrgn

Xgrgn

emgy

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

Base from U.S. Geological Survey, 1983, provisional edition.

Projection: Universal Transverse Mercator.

10,000-foot State grid ticks based on Nevada coordinate system,

east zone.

1,000-meter Universal Transverse Mercator grid, zone 11.

1927 North American datum

Geology mapped in 1989–1992. Bedrock by R.G. Bohannon;

surficial deposits by D.L. Hoover and V.S. Williams.

Photocompilation by F.W. Simonds.

Editing and digital cartography by Alessandro J. Donatich

Color design by Virginia D. Scott

Manuscript approved for publication April 13, 1995

SCALE 1:24 000

1 0 1 MILE 1/ 2

1 .5 0 1 KILOMETER

CONTOUR INTERVAL 10 METERS

SUPPLEMENTARY CONTOUR INTERVAL 5 METERS

CONTROL ELEVATIONS SHOWN TO THE NEAREST 0.1 METER

OTHER ELEVATIONS SHOWN TO THE NEAREST METER

NATIONAL GEODETIC VERTICAL DATUM OF 1929

GEOLOGIC MAP OF THE RIVERSIDE QUADRANGLE, CLARK COUNTY, NEVADA

By

Van S. Williams, Robert G. Bohannon, and D.L. Hoover

1997

13°

APPROXIMATE MEAN

DECLINATION, 1997 TRUE NORTH

MAGNETIC NORTH

NEVADA

QUADRANGLE LOCATION

Quaternary units omitted

1000 m = 3281 ft

A A'

1500

1000

500

1500

1000

500

METERS METERS

emsr

emkp

emkp

emgy

emgy

emgg

emgg

emgw

emh

emst

emst

ed

ed

MDsc

MDsc Mm

Mm

Tab

eb el ec

et

Xgn

Xgn

Xqm

Xqm

en en Dsv

Dsv

el

?

A T

A T

FAULT

SPRING

HEN

Bunkerville

Ridge

Quaternary units omitted

1000 m = 3281 ft

METERS

1000

1500

B

1000

METERS

B'

1500

Xgrgn

Xggn

Xggn Pe

Pkfm Tab Xa Xa

Xqm

Pkh

Phb

Ptbc

Pts Ptwr

Mm

eu et

eb

ec eu

emh

emgw emgg

emgy

emkp

Dsv Mm Phb

ed

en

emst

emsr
DESCRIPTION OF MAP UNITS

Channel sand of Virgin River (Holocene)—Very pale 

orange, grayish-orange-pink, and moderate-orange-pink, 

mostly fine to medium sand, silt, and small amounts of 

gravel; unconsolidated, poorly sorted to well sorted, poorly 

bedded. Gravel is angular to subrounded cobbles and pebbles of gneiss, granite, pegmatite, quartzite, limestone, and 

dolomite, and well-rounded clasts of brown quartzite and 

black and green chert. Unit exposed in sand bars of Virgin River channel and as deposits in abandoned channels 

within flood-plain deposits along Virgin River. Surface of 

unit is characterized by bar-and-swale topography. No soil 

observed. Informally named for sands deposited along 

Virgin River. Thickness more than 2 m

Flood-plain deposits of Virgin River (Holocene)—Very 

pale orange and grayish-orange-pink sand and small 

amounts of gravelly sand and gravel; unconsolidated, 

mostly well sorted, poorly bedded. Unit covers about 60 

percent of floor of Virgin Valley. Surface of unit is 1–2 m 

above unit Qsv and is smooth and covered with heavy 

growth of mesquite where not cultivated. Exposed thickness 2 m

Alluvium of Nickel Creek (Holocene to late Pleistocene(?))—Very pale orange to yellowish-gray gravel, sandy 

gravel, and sand; unconsolidated, poorly to moderately 

sorted, poorly to moderately well bedded. Gravel is angular to subrounded clasts of gneiss, granite, pegmatite, 

quartzite, limestone, and dolomite. Clasts are mostly cobbles and pebbles in size, but include boulders as much as 2 

m in diameter. Unit includes the active-channel, floodplain, and low-terrace deposits of minor streams. Channels are commonly braided, and terraces are less than 1.5 

m above active channels. South of Virgin River, deposits 

are largely gravel and sandy gravel; north of river, deposits 

are largely sand. Surface of unit is characterized by barand-swale topography. Surface clasts mostly lack desert 

varnish, but some quartzite and fine-grained igneous and 

metamorphic clasts have dark-brown varnish that was 

probably inherited from older deposits; light-brown stains 

on some quartzite clasts may be postdepositional or inherited. Maximum soil development on terraces consists of 

stage I carbonate-enriched horizon with a maximum thickness of 0.5 m; local lenses of gravel may have patchy 

rinds of carbonate less than 3 mm thick on bottom of 

clasts; no B or A horizons observed. Informally named for 

deposits along Nickel Creek in central part of quadrangle. 

Exposed thickness more than 3 m

Colluvium (Holocene and Pleistocene)—Moderately consolidated to consolidated, nonbedded talus; talus consists 

of angular to subangular, pebble- to boulder-size clasts and 

minor amounts of sand derived from bedrock and unit 

Tab. Carbonate-enriched horizon and varnish similar to 

those of unit Qymm. Occurs on most steep slopes on 

unit Tab, but mapped only where extensive or where unit 

covers contacts of older deposits; slightly to extensively 

dissected. Commonly covers unit Tmc below the contact 

with overlying unit Tab. Maximum thickness probably less 

than 5 m

Slump blocks (Holocene and Pleistocene)—Blocks of moderately consolidated gravel from units Tab or Qot and underlying sand slumped from steep scarps that have been 

undermined by erosion of the softer underlying unit (usually Tmc). Some of the blocks have long been inactive as 

indicated by lack of disruption of unit Qymm surrounding 

the slump blocks, and others have formed recently. 

Slump block thickness ranges from 5 to 15 m

Eolian deposits (Holocene to late Pleistocene)—Very pale 

orange and yellowish-gray sand; unconsolidated; well sorted, no visible bedding. Forms sand sheets and dunes in and 

at edge of some tributary washes along north side of Virgin 

River. No soil observed. Maximum thickness about 20 m 

where sand sheets drape over cliffs north of Virgin River

Sandy terrace deposits of Virgin River (Holocene to late 

Pleistocene(?))—Very pale orange and grayish-orangepink sand and small amounts of gravelly sand and gravel; 

unconsolidated, mostly well sorted, poorly bedded. Alluvium in this unit contains less gravel than in older terrace 

deposits (QTv, Qyv, and Qgv) but is similar to alluvium on 

modern flood plain (Qfv). At mouth of Toquop Wash (fig. 

1), near center of northern edge of map area, this unit includes sediment from Toquop Wash interfingering with 

that from upper Virgin River. Along Virgin River, unit is 

preserved in small, isolated terraces that are about 6 m 

above the channel (Qsv) and commonly covered with a 

thin sheet of eolian sand (Qe). Stage I carbonate soil is 

0.3 m thick. Exposed thickness more than 6 m

Young terrace alluvium of Virgin River (late Pleistocene)—Pale-red, pale-reddish-brown, and light-brown 

gravel and sandy gravel; poorly sorted, poorly to well bedded; uncemented to well cemented by calcium carbonate. 

Gravel clasts are angular to subrounded gneiss, granite, 

pegmatite, quartzite, limestone, and dolomite mixed with 

lesser amounts of well-rounded, light-brown quartzite (Late 

Proterozoic and Lower Cambrian Prospect Mountain(?) 

Quartzite) and black and grayish-green chert; most clasts 

less than 0.3 m in diameter; maximum clast size 1 m. 

Stage II carbonate-enriched soil horizon about 1 m thick; 

no A or B horizon observed, but terrace surface is commonly covered with eolian sand. Forms a narrow terrace 

about 20 m above channel of Virgin River that widens to 

700 m wide just west of map area. Probably correlative 

with the Lost City terrace alluvium deposited by Muddy 

Creek in the Moapa Valley, about 30 km to the west 

(Gardner, 1972b). Maximum exposed thickness 20 m

Young terrace alluvium of Toquop Wash (late Pleistocene)—Gravel and sandy gravel similar to those in unit 

Qyv except that clasts are primarily from Mormon Mountains and lack the gneiss, granite, pegmatite, and chert 

common in Virgin River gravel. Soil consists of stage II 

carbonate-enriched horizon 0.5–1.0 m thick; no B or A 

horizons observed; surface mostly covered by eolian sand 

less than 0.3 m thick. Forms terrace at mouth of Toquop 

Wash in sec. 5, T. 14 S., R. 70 E., at north-central edge 

of map area. Depositional surface 20 m above present 

stream level. Informally named for deposits at mouth of 

Toquop Wash. Maximum exposed thickness 20 m

Young mountain-side pediment and fan alluvium (late 

Pleistocene)—Orange-pink, grayish-orange-pink, and yellowish-gray gravel, sandy gravel, and small amounts of 

sand; poorly consolidated, poorly sorted, poorly to moderately well bedded. Gravel clasts are angular to subrounded gneiss, granite, pegmatite, quartzite, limestone, 

and dolomite; clasts mostly less than 0.5 m in diameter; 

isolated boulders may be as much as 1 m in diameter. Soil 

consists of stage III carbonate-enriched horizon 0.8–1.3 m 

thick; no B horizon observed; Av horizon is 10–25 cm 

thick. Fan surfaces have moderately packed pavement; 

pale-brown to grayish-brown, dull to shiny, continuous to 

patchy varnish films are as thick as 0.25 mm on quartzite, 

gneiss, and pegmatite clasts; carbonate clasts in pavement 

etched to depth of 1 cm or less. Fan surfaces relatively intact and flat, but dissected by steep-sided washes that head 

above unit. Creosote bush prevalent. Unit present as terrace remnants 5–30 m above major washes and fan surfaces at lower elevations. Graded to upper surface of 

young Virgin River terrace alluvium (Qyv). Interbedded 

with thin beds of grayish-orange-pink to moderate-orangepink, poorly bedded fluvial sands of ancestral Virgin River 

in secs. 13 and 23, T. 14 S., R. 69 E. Unit is well exposed along Gold Butte road in sec. 23, T. 14 S., R. 69 

E., just south of point where Virgin River crosses western 

edge of map area. Maximum thickness about 20 m

Young sandy mesa-side pediment and fan alluvium (late 

Pleistocene)—Moderate-orange-pink to grayish-orangepink and yellowish-gray sand from the Muddy Creek Formation (Tmc) and pebble- to boulder-size clasts from the 

massive carbonate-enriched soil horizon capping Mormon 

Mesa, just west of map area. Poorly to moderately consolidated, poorly sorted, poorly to moderately well bedded. Soil consists of stage II carbonate-enriched horizon 

0.5–1.0 m thick; no B or A horizons observed; partly covered by patches of eolian sand (Qe) less than 0.3 m thick; 

unit may include some eolian sand. Fan surfaces rounded 

0–10 m from edge of dissecting washes; depositional surface flat and well preserved. Deposited on pediments cut 

on weakly consolidated Muddy Creek Formation across 

bench between Mormon Mesa escarpment and high 

terraces of Virgin River. Creosote bush prevalent; yucca 

sparse. Maximum thickness about 10 m

Younger middle terrace alluvium of Toquop Wash (middle Pleistocene)—Gravel and sandy gravel containing 

rocks from the Mormon Mountains similar to those in unit 

Qyt. Moderately to strongly cemented by calcium carbonate. Soil consists of stage III carbonate-enriched horizon 1–2 m thick; no B or A horizons observed. Preserved 

as discontinuous remnants about 35 m above Virgin River 

channel along a former course of Toquop Wash 2 km 

west of its present course. Surface has a moderately well 

packed pavement. Predominantly a thin layer of alluvium 

covering a terrace cut in an older alluvial fill. Maximum 

exposed thickness 15 m

Younger middle mountain-side pediment and fan alluvium (middle Pleistocene)—Pale-yellowish-brown, palered, and light-brownish-gray gravel, sandy gravel, and 

small amounts of sand; poorly to moderately consolidated, 

poorly sorted, poorly to moderately well bedded. Gravel 

clasts are angular to subrounded gneiss, granite, pegmatite, quartzite, limestone, and dolomite; clasts are mostly 

less than 1 m in diameter; boulders 1.5–2 m in diameter 

scattered throughout unit at higher elevations. Soil consists of stage II to III carbonate-enriched horizon 0.5–1.0 

m thick; no B horizon observed; maximum Av horizon 

thickness is 20 cm. Fan surfaces have moderately to tightly packed pavement; grayish-brown to brownish-black, dull 

to shiny varnish films as much as 0.25 mm thick on 

quartzite, gneiss, and pegmatite clasts; carbonate clasts in 

pavement etched to depths as much as 2 cm; isolated 

boulders 1–2 m in diameter protrude through pavement. 

Fan surfaces rounded as far as 10–30 m from edges of 

dissecting washes; washes that head above unit have steep 

sides below rounded surface; moderate internal dissection 

throughout map area. Creosote bush prevalent; sparse 

Joshua trees and yucca plants. Unit forms terraces along 

major washes and fan deposits that locally surround small 

hills of unit Tab. Interbedded with thin beds of moderateorange-pink and light-brown, poorly bedded fluvial sands 

of Virgin River for about 1 km south of Virgin River. Well 

exposed in roadcuts along Nevada Highway 170 between 

Riverside and Mesquite, Nev., just south of Virgin River. 

Maximum thickness more than 35 m

Older sandy mesa-side pediment and fan alluvium (middle Pleistocene)—Moderate-orange-pink to grayishorange-pink and yellowish-gray sand from the Muddy 

Creek Formation (Tmc) and pebble- to boulder-size clasts 

from the massive carbonate-enriched soil horizon capping 

Mormon Mesa. Poorly to moderately consolidated, poorly 

sorted, poorly bedded. Soil consists of stage III carbonateenriched horizon 0.5–1.5 m thick; no B or A horizons observed; locally covered by sheets of eolian sand (Qe); unit 

may include some eolian sand. Surfaces rounded 15–30 

m from edge of dissecting washes; moderate internal dissection throughout map area. These deposits are remnants of alluvium deposited on pediments cut on weakly 

consolidated Muddy Creek Formation (Tmc) and Virgin 

River terrace alluvium (Qav and Qgv) that underlie a wide 

bench between the cemented gravel of unit QTv and Mormon Mesa escarpment just north of map area. Downcutting by streams and retreat of Mormon Mesa escarpment 

has deprived these surfaces of their sediment and water 

supply so they are generally inactive and are gradually being destroyed by expansion of younger pediment surfaces 

about 10 m lower (Qys). Probably correlative to the Overton pediment alluvium in Moapa Valley (Gardner, 1972b). 

Creosote bush prevalent; yucca sparse. Maximum thickness about 20 m

Middle terrace alluvium of Toquop Wash (middle(?) Pleistocene to early(?) Pleistocene)—Gravel and sandy gravel 

containing rocks from the Mormon Mountains similar to 

those in unit Qyt. Moderately to strongly cemented by 

calcium carbonate. Soil consists of stage III–IV carbonateenriched horizon 1–2 m thick; no B or A horizons observed. Preserved as discontinuous remnants about 55 m 

above Virgin River channel along former course of Toquop 

Wash 2 km west of present course. Surface has wellpacked pavement. Maximum exposed thickness 20 m

Middle mountain-side pediment and fan alluvium (middle(?) Pleistocene to early(?) Pleistocene)—Pale-yellowish-brown, pale-red, and light-brownish-gray gravel and 

sandy gravel; moderately consolidated, poorly sorted, 

poorly to moderately well bedded. Gravel clasts are angular to subrounded gneiss, granite, pegmatite, quartzite, 

limestone, and dolomite; clasts are mostly less than 1 m in 

diameter; boulders 1.0–1.5 m in diameter scattered 

throughout unit at higher elevations. Soil consists of stage 

IV carbonate-enriched horizon about 25 cm thick over 

about 85 cm of mixed stage III and stage II carbonate-enriched horizon; no A or B horizons observed. This soil is 

largely developed in a colluvial mantle 1–2 m thick that 

covers the rounded radial ridges (ballenas as defined by Peterson, 1981) characteristic of this unit. Surface of this 

unit is distinctly more rounded than that of units Qymm

and Qym. Amount of original depositional surface remaining decreases westward across map area. Washes 

that head above unit have steep sides below rounded surfaces. Fan surfaces have moderately to tightly packed 

pavement; grayish-brown to brownish-black, dull to shiny 

varnish films as much as 0.25 mm thick on quartzite, 

gneiss, and pegmatite clasts; carbonate clasts in pavement 

etched to depths as much as 2 cm. Creosote bush prevalent; sparse Joshua trees and yucca plants. Maximum 

thickness more than 35 m

Middle terrace gravels of Virgin River (early(?) Pleistocene)—Pale-brown to dark-yellowish-brown gravel, sandy 

gravel, and pebbly sand; unconsolidated to weakly consolidated, well sorted, well bedded. Gravel clasts are similar 

to those of unit QTv, but clast sizes mostly less than 0.1 m 

and maximum size less than 0.5 m. Soil consists of stage 

IV carbonate-enriched horizon 1–2 m thick that was developed in sand and has been largely stripped away. Surface 

is tightly packed pavement of rounded cobbles coated with 

dark varnish. Exposed only in northwest corner of map 

area in secs. 2 and 11, T. 14 S., R. 69 E., with basal elevation of 490 m and maximum depositional surface elevation of 530 m (1 km west of map area). Extensively preserved west of map area. Maximum thickness 20 m

Sandy terrace alluvium of Virgin River (early(?) Pleistocene)—Very dark red, grayish-red, and grayish-blue-green, 

discontinuous sand, silt, and clay; unconsolidated to slightly consolidated, moderately to well sorted, moderately well 

to well bedded. Probably overbank deposits. Soil consists 

of stage III–IV carbonate-enriched horizon 1–2 m thick 

that is probably eroded. Best exposed in SWc sec. 1 and 

NWc sec. 12, T. 14 S., R. 69 E. with basal elevations of 

450–510 m. Informally named for deposits north of Virgin River that generally overlie unit QTv, interfinger with 

unit Qgv, and underlie unit Qyms. This unit in combination with boulder-cobble (QTv) and pebble-cobble (Qgv) 

channel gravel facies records a major filling event when 

the Virgin River aggraded more than 115 m and overtopped its canyon walls to spread out across a broad flood 

plain. This fill is probably older than the Overton terrace 

alluvium in Moapa Valley (Gardner, 1972b). Maximum 

thickness 30 m

Old terrace alluvium of Toquop Wash (early(?) Pleistocene)—Gravel, sandy gravel, and pebbly sand containing 

rocks from the Mormon Mountains similar to those in unit 

Qyt. Moderately to strongly cemented by calcium carbonate. Soil consists of stage III–IV carbonate-enriched 

horizon 1–2 m thick; no B or A horizons observed. Only 

preserved deposit caps a mesa that is 65 m above Virgin 

River channel and extends 2.8 km north of map area 

along a former course of Toquop Wash 1 km west of its 

present course. Surface has a well-packed pavement. 

Thickness: 35 m of gravel over 15 m of sand

Old mountain-side pediment and fan alluvium (early(?) 

Pleistocene)—Identical to unit Qmm but deposited at a 

level about 10 m above depositional surface of unit Qmm. 

Preserved only in a few isolated remnants near center of 

map area. Maximum thickness more than 35 m

Old gravel of Virgin River (early(?) Pleistocene to Pliocene)—Pale-red, pale-reddish-brown, and light-brown 

gravel and sandy gravel; slightly to very strongly cemented 

by calcium carbonate; poorly sorted, poorly to well bedded. Individual beds thicker than 8 m. Gravel clasts are 

angular to subrounded gneiss, granite, pegmatite, quartite, 

limestone, and dolomite mixed with lesser amounts of 

well-rounded, light-brown quartzite (Late Proterozoic and 

Lower Cambrian Prospect Mountain(?) Quartzite) and 

black and grayish-green chert; most clasts less than 0.3 m 

in diameter; maximum clast size 1 m. No soil observed. 

Forms cliffs along north side of Virgin River and tributary 

canyons in secs. 11, 12, and 14, T. 14 S., R. 69 E. Basal 

elevations increase from 430 to 480 m away from axis of 

ancestral valley. Informally named for deposits north of 

Virgin River that underlie unit Qav. Narrow, discontinuous terraces at levels about 35 and 55 m above present 

Virgin River channel were cut on this deposit during erosion of alluvial fill. These probably correspond to the period of deposition of units Qmt and Qymt, but no mappable deposits are preserved on cut terraces. Maximum 

thickness 50 m

Alluvium of Bunkerville Ridge (Pliocene)—Pale-brown, 

pale-yellowish-brown, light-brownish-gray, and pale-red 

gravel, sandy gravel, and gravelly sand. Includes many 

boulders 1–2 m in diameter. Distal part is clast supported, 

well consolidated, poorly sorted, and well bedded, and 

maximum clast size is 1 m; proximal part is matrix supported, well consolidated, poorly sorted, and poorly bedded, and maximum clast size is 8 m. Pale-red to grayishorange-pink gravelly sand that contains gravel beds less 

than 0.5 m thick is present in lowest part of unit along 

main wash east of Juanita Springs Ranch in secs. 11 and 

12, T. 15 S., R. 69 E. and at elevations of 600–650 m 

east of Nickel Creek. Soil on depositional surface consists 

of stage V carbonate-enriched horizon 3–6 m thick that 

has been stripped away in most places. Generally, unit is 

eroded into rounded, radial ridges covered with 2–3 m of 

cemented colluvium bearing thick stage III–IV carbonateenriched soil horizons; no B horizon observed; sandy and 

silty Av horizon has maximum thickness of 60 cm. The 

ridges are separated by deep, well-integrated tributary 

drainages, and relief ranges from 20 to 60 m within 5–7 

km of Virgin Mountains. The level of the ridge tops defines a smooth radial surface that is probably quite close to 

original depositional surface of most of unit. The level of 

the ridge tops near the mountain front in southeastern 

part of map area defines another surface that is slightly 

higher, and deposits there may be older than rest of unit. 

Alternatively, the higher surface may result from uplift and 

tilting of unit Tab along the mountain front. Tops of narrow ridges commonly littered with platy fragments from 

upper part of carbonate-enriched soil horizon; quartzite, 

gneiss, and pegmatite clasts on surface irregularly to continuously covered by brownish-black to black, dull to shiny 

desert varnish as much as 2 mm thick; limestone and dolomite clasts etched to depths of 1.5–3 cm. Base of unit 

generally conformably overlies the Muddy Creek Formation immediately above 1–2 m of conglomerate that resembles modern Virgin River gravel at an elevation of 

about 580 m. Elevation of base of unit Tab corresponds 

approximately to elevation of calcrete on Mormon Mesa. 

Maximum soil development on unit Tab is comparable to 

that on Mormon Mesa, which suggests that dissection of 

depositional surface of unit Tab began when depositional 

environment changed from closed basin to open basin. 

Joshua trees, yucca, and creosote bush prevalent on tops 

of ballenas. Informally named for good exposures in 

southern part of map area north of Bunkerville Ridge 

along drainages that originate in Virgin Mountains. Exposed thickness at distal margin 75 m

Muddy Creek Formation (Miocene)

Sandstone, siltstone, claystone, and minor conglomerate—Moderate-orange-pink, moderate-reddish-orange, 

light-red, and light-brown, fine- to medium-grained sandstone and small amounts of siltstone and claystone; partly 

consolidated, poorly to well bedded. Sandstone beds are 

moderately to well sorted; cross bedding and ripple marks 

common; individual beds generally die out within 50–200 

m, but bed sets may be continuous for 200–500 m or 

more; cemented by calcite, clay, or gypsum. A few sandstone beds contain insect burrows and root casts and bird 

and animal tracks. Fossil remains of Megatylopus (camels), Hemiauchenia (llamas), Aelurodon (dogs), Indarctos 

(bear), Equinae (horses), and Texoceros (pronghorns) 

found in formation on south side of Virgin River immediately west of map area indicate a medial Hemphillian 

(late Miocene) age (R.H. Tedford, American Museum of 

Natural History, unpub. data, 1978). Siltstone, claystone, 

and white tuffaceous sandstone and tuff appear to be 

more common within 1–1.5 km of Virgin River at elevations of 430–450 m. Unit contains thin (less than 0.3 m) 

bed of very light gray, slightly reworked air-fall tuff of very 

limited extent at 465 m elevation near southwest corner 

of sec. 1, T. 14 S., R. 69 E. Ash bed is about 160 m below top of Muddy Creek Formation at edge of Mormon 

Mesa, about 2 km to the west. Ash bed is just below an 

indistinct contact with overlying unit Qav, and there is a 

slight possibility that it may lie within unit Qav. Upper 

5–10 m of unit Tmc beneath unit Tab contains three 

marker beds: a lower sandstone, 1–1.5 m thick, that contains rip-up or slump clasts of grayish-green to grayishblue-green claystone that have a maximum thickness of 

0.5 m; a medial grayish-green to grayish-blue-green massive mudstone, 0.5–2 m thick; and an upper conglomerate, 0.3–2 m thick, that contains pebbles and cobbles of 

well-rounded brown quartzite (Late Proterozoic and Lower 

Cambrian Prospect Mountain(?) Quartzite) and black and 

grayish-green chert and lesser amounts of subangular to 

subrounded gneiss, granite, gray quartzite, pegmatite, 

limestone, and dolomite. The three marker beds may or 

may not be separated and overlain by sandstone typical of 

the unit, and each bed may or may not be present at any 

location. Lithologies of conglomerate clasts indicate that 

conglomerate was deposited by an ancestral Virgin River 

that was integrated to distant headwaters in Utah and may 

be much younger than the underlying, fine-grained part of 

the Muddy Creek Formation. It probably correlates to the 

tan quartzite-granite clast gravel (Gardner, 1968, p. 55) 

that is 30 m thick immediately beneath surface of southern tip of Mormon Mesa. Horse and puma teeth of Blancan (Pliocene) age (Longwell and others; 1965, M.C. McKenna, written commun., 1957) were found in similar 

gravels at southern tip of Mormon Mesa, but these fossiliferous gravels appear to overlie the lowest calcrete and the 

gravel beneath the calcrete. Outcrops of unit Tmc in 

northwestern part of map area are continuous with Muddy 

Creek Formation of Longwell (1928, 1936) and Longwell 

and others (1965). Maximum exposed thickness about 

170 m

Altered claystone and sandstone—Exposed around 

springs at Juanita Springs Ranch, near southwest corner 

of map area; white, very light gray, and grayish pink; silica 

and calcium carbonate deposited in pores and fractures

Kaibab Formation (Lower Permian)—Member subdivision 

follows that of Sorauf and Billingsley (1991)

Harrisburg Member—Limestone, gypsum, and siltstone; 

gray to whitish gray; marine and nonmarine; recessive, 

forms slopes that are generally covered with light-colored 

talus. Bedding is irregular, discontinuous, uneven, and 

wavy. Limestone occurs in moderately resistant beds that 

average 10 cm thick, and in poorly bedded units that commonly contain abundant chert pods. Limestone breccia is 

common; probably caused by dissolution of gypsum. 

Crops out only along mountain front on eastern edge of 

quadrangle. About 30 m thick

Fossil Mountain Member—Cherty limestone; fossiliferous; 

marine; very resistant, forms high ridges near eastern 

edge of quadrangle. Limestone is medium gray and chert 

is brown to translucent gray. Chert is abundant and occurs in nodules, beds, and elongated masses; chert commonly defines bedding, which is parallel, broadly discontinuous, and uneven; bedding thickness is uniform at 10–25 

cm. Fossils include abundant corals and marine mollusks. 

Thickness 100–150 m

Toroweap Formation (Lower Permian)—Member subdivision follows that of Sorauf and Billingsley (1991)

Woods Ranch Member—Limestone, dolomite, gypsum, 

siltstone, and sandstone; white, gray, light gray, and pink. 

Recessive unit between cliff-forming limestone units of 

Fossil Mountain Member of Kaibab Formation (Pkfm) and 

Brady Canyon Member of Toroweap Formation (Ptbc). 

Bedding is irregular, discontinuous, wavy, and uneven. 

Exposed only near mountain front on eastern edge of 

quadrangle where it is commonly covered by light-colored 

talus. Thickness 30–60 m

Brady Canyon Member—Medium-gray limestone and 

brown and light-gray chert; very resistant, forms prominent cliffs and ridges near eastern edge of quadrangle. 

Parallel, discontinuous, and even bedding defined by elongate chert bodies; beds are several centimeters to tens of 

centimeters thick. Chert is abundant, but less so than in 

Fossil Mountain Member of Kaibab Formation (Pkfm); individual chert masses average about 0.3 m long. Fossiliferous, contains marine mollusks. Exposed only near 

mountain front on eastern edge of quadrangle. Bedding 

character is similar to that of Woods Ranch Member 

(Ptwr). Thickness 90–140 m

Seligman Member—Limestone, dolomite, gypsum, siltstone, and minor sandstone; white, light gray, or pale red; 

marine and nonmarine. Recessive and commonly forms 

covered slopes below ridges of Brady Canyon Member 

(Ptbc). Exposed only near mountain front on eastern 

edge of quadrangle. Bedding character is similar to that of 

Woods Ranch Member (Ptwr). About 45 m thick

Esplanade Sandstone (Lower Permian)—Use of term Esplanade Sandstone for these rocks follows that of McKee 

(1975, 1982). Sandstone; red, light buff, and white; nonmarine. Moderately resistant, but poorly exposed in quadrangle. Bedding is wavy, discontinuous, nonparallel, and 

uneven; beds range from 0.5 to 2 m thick. Internal, lowangle trough and planar cross-stratification common. 

Sand grains are fine to very fine, grain supported, well 

rounded, well sorted, and composed of quartz; little or no 

matrix present; moderately friable to well indurated. 

Thickness 600(?) m

Bird Spring Formation (Lower Permian and Pennsylvanian)—Limestone, cherty limestone, arenaceous limestone, and calcareous sandstone. Limestone is gray, light 

gray, and white; cherty limestone is brown; arenaceous 

limestone is light gray and white when fresh, but weathers 

brown and yellow brown; sandstone is light yellow gray, 

weathers brown, and commonly forms conspicuous 

ledges. Bedding is parallel, even, and continuous with 

cross bedding common in sandstone; beds 0.5–1 m thick 

and alternately resistant and moderately resistant, causing 

stair-step erosional form throughout unit. Marine and locally highly fossiliferous. Basal 10 m of formation is 

slope-forming silty limestone and reddish-weathering siltstone. Thickness 360–400 m

Monte Cristo Limestone (Upper and Lower Mississippian)—Limestone; medium gray; some brown cherty zones; 

marine. Lithologically and in part temporally equivalent to 

the Redwall Limestone of the Colorado Plateaus province. 

Consists of five members of marine origin described by 

Hewett (1931) in Goodsprings mining district of Spring 

Mountains 130 km southwest of map area. From youngest to oldest, these are the Yellowpine, Arrowhead, Bullion, Anchor, and Dawn Members. The Yellowpine, which 

is lithologically equivalent to the Horseshoe Mesa Member 

of Redwall Limestone (McKee, 1974), is resistant, cliffforming, medium-grained, bioclastic, brownish-gray limestone that weathers medium gray. Minor amounts of 

brown chert are present; bedding is indistinct. The Arrowhead is nonresistant, dark-gray, aphanitic limestone that 

weathers yellowish brown; forms niche in cliff. Beds are 

parallel, wavy, even, and about 10–20 cm thick. Total 

thickness of member is about 10 m. The Bullion, which is 

lithologically equivalent to the Mooney Falls Member of 

Redwall Limestone (McKee, 1974), is resistant, mediumgray, medium- to coarse-grained, indistinctly bedded, bioclastic limestone that forms cliffs. The Anchor, which is 

lithologically equivalent to the Thunder Springs Member of 

Redwall Limestone (McKee, 1974), is a resistant, cliffforming, medium-gray, bioclastic, medium- to coarsegrained limestone containing brown chert. Chert is found 

in elongated masses and stringers that define irregularshaped, discontinuous, parallel beds about 10–20 cm 

thick; amount of chert varies from 20 to 50 percent of 

member. The Dawn, which is lithologically equivalent to 

the Whitmore Wash Member of Redwall Limestone (McKee, 1974), is resistant, medium-gray, coarse-grained, indistinctly bedded, crystalline and bioclastic limestone that 

weathers light gray and forms cliffs. The Monte Cristo 

Limestone forms a single uniform cliff that generally appears unbedded from a distance except where chert bands 

of the Anchor Member are present or where the Arrowhead Member forms niche. About 225–350 m thick

Sultan Limestone (Lower Mississippian and Upper Devonian)—Nomenclature and member subdivision follows regionally recognized descriptions by Hewett (1931), except 

that no lithology resembling his basal unit, the Ironside 

Member, has been recognized locally. Lithologic equivalent 

of Muddy Peak Limestone of Longwell (1928), mapped in 

some parts of southwestern Nevada, and equivalent in part 

to Temple Butte Limestone on Colorado Plateaus province

Crystal Pass Member (Lower Mississippian and Upper 

Devonian)—Limestone and dolomite; light gray; weathers 

light and medium gray; resistant, forms ledges and small 

cliffs; marine. Medium- to fine-grained, crystalline texture. 

Bedding is moderately well defined; beds are parallel, 

even, continuous, and 0.4–2 m thick. Thickness 60–100 

m

Valentine Member (Upper Devonian)—Limestone and 

dolomite; medium gray; weathers dark to medium gray; 

resistant, forms ledges and small cliffs; marine. Mediumto fine-grained, crystalline texture. Bedding is moderately 

well defined; beds are parallel, even, continuous, and 

0.4–2 m thick. Thickness 60–100 m

Nopah Formation (Upper Cambrian)—Dolomite and sandy 

dolomite; light gray; weathers to uniform pale yellowish 

gray; crystalline texture; moderately resistant, forms cliffs; 

marine. Beds are parallel, even, continuous, and a few 

centimeters to several meters thick. Base of unit is 

marked by thin sandy dolomite that erodes to recessive 

slope, is yellow to brownish gray, and weathers dark or 

medium brown. This discontinuous basal unit might be 

the Dunderberg Shale Member, but it is not differentiated 

on map. Distinguished from underlying dolomite (ed) by 

yellow color and slope-forming beds of the Dunderberg. 

About 60 m thick

Dolomite (Upper Cambrian)—Unnamed Cambrian dolomite of McKee (1945); light gray; weathers brownish gray; 

resistant, forms cliffs; marine. Upper part is glauconitic. 

Medium- to fine-grained, crystalline texture. Beds are parallel, even, continuous, and vary between 5 cm and 0.5 m 

thick. Thickness 100–130 m

Dolomite (ed) and Muav Limestone, undivided (Upper 

and Middle Cambrian)—Shown only on cross section 

B–B' where units do not extend to surface

Muav Limestone (Middle Cambrian)—Subdivision of the 

Muav follows that of McKee (1974) except for the informally designated “striped unit,” which is not present in 

Grand Canyon, but has been mapped at top of the Mauv 

to the east in Jacobs Well and Elbow Canyon 7 a-minute 

quadrangles of Arizona by Bohannon (1991). The Muav 

is probably lithologic equivalent of upper part of the Bonanza King Formation west of map area, which is Middle 

and Upper Cambrian

Striped unit—Limestone and dolomite; light-gray to white 

beds and medium-gray beds are interbedded; moderately 

resistant to recessive; marine. Limestone and dolomite intergrade laterally and vertically. Light-colored beds are 

composed of uniform, fine- to medium-grained, crystalline 

carbonate minerals having very indistinct, fine laminations. Darker beds are composed of fine-grained, crystalline carbonate minerals and about 10 percent silt that 

weathers yellow brown. Small-scale, trough cross-laminations present in darker beds. Bedding is parallel, even, 

and continuous; interbedding of light and dark layers, 

each 1–3 m thick, present throughout unit. Thickness 

75–100 m

Havasu Member—Dolomite and limestone; medium to 

dark gray; resistant, forms small cliffs and ledges; marine. 

Limestone and dolomite intergrade laterally and vertically. 

Bedding is indistinct, parallel, even, and continuous. Consists of fine-grained, crystalline carbonate minerals and 

about 10–20 percent yellow-brown-weathering silt. Thickness 40–50 m

Gateway Canyon Member—Subdivided into three informal units

Dolomite—Recessive, light-gray to white, finely laminated 

dolomite; beds are parallel, continuous, even, and 20 cm 

to 1 m thick. Thickness 20 m

Dolomite and limestone—Resistant, light-gray to browngray silty dolomite and limestone that form ledges and 

cliffs; contains internal cross-laminations. Thickness 10 m

Limestone and dolomite—Moderately resistant, lightgray to brown-gray sandy limestone and sandy dolomite 

that weather to a distinctive orange brown; fine, parallel to 

low-angle cross-laminations. Thickness 50 m

Kanab Canyon and Peach Springs Members, undivided—Silty limestone and dolomite; brown gray and dark 

gray; weathers yellow brown, rust brown, and brown gray. 

Limestone and dolomite intergrade laterally and vertically; 

resistant, forms cliffs and rugged outcrops; marine. Composed of fine- to medium-grained, crystalline carbonate 

minerals. Bedding is indistinct but parallel, wavy, and continuous on close inspection; beds range from 5 cm to 1 m 

thick. Thickness 75–90 m

Spencer Canyon, Sanup Plateau, and Rampart Cave 

Members, undivided—Silty limestone and dolomite; medium to dark gray; weathers medium gray, yellow gray, 

and brown gray; resistant, forms cliffs and ledges; marine. 

Composed of fine- to medium-grained carbonate minerals. 

Bedding is parallel, even, and continuous; beds range from 

a few centimeters to greater than 1 m thick; bedding is 

well defined by interbeds of yellow-brown silty carbonate 

rocks and medium-gray limestone. Thickness 60–110 m

Chisholm Shale (Middle Cambrian)—Shale, quartzite, and 

limestone; black to dark gray and gray green; marine. 

Lithologic equivalent of Flour Sack Member of Bright Angel Shale in Grand Canyon. Recessive, commonly forms 

gentle slope covered by well-developed soil horizon. Shale 

is interbedded with minor amounts of yellow-brown quartzite and rare limestone, which are relatively resistant and 

better exposed, but are less abundant than shale. Bedding 

in shale is parallel, even, and continuous; beds range from 

less than 1 cm to about 5 cm thick. Thickness 10–15 m

Lyndon Limestone (Middle Cambrian)—Limestone; dark 

gray, but commonly iron stained and weathers to rust colors and orange brown; marine. Lithologic equivalent of 

Meriwitica Tongue of Muav Limestone in Grand Canyon. 

Resistant, forms low ridges and hogbacks in larger valleys; 

caused by recessive shale above and below. Thickness 10 

m

Bright Angel Shale (Middle Cambrian)—Shale, and minor 

quartzite, limestone, and dolomite; black to dark gray, but 

weathers gray and light brown; marine. Shale is interbedded with yellow-brown quartzite in lower part and rare 

limestone and dolomite in upper part. Bedding is parallel, 

even, and continuous; beds range from less than 1 cm to 

about 5 cm thick. Recessive, forms slopes that are commonly covered. Thickness 60–100 m

Tapeats Sandstone (Middle and Lower Cambrian)—Sandstone and quartzite; pale red and light brown; weathers 

dark red and yellow brown; locally pebbly; probably 

nearshore marine. Resistant, forms steep slopes, cliffs, 

and knobs. Bedding is parallel, continuous, and even; 

beds range from 5 to 50 cm thick; most beds have low- to 

moderate-angle cross-stratification. Sand is well to moderately sorted, fine to medium, moderately well rounded, 

and composed predominantly of quartz. Upper part of 

formation is yellow-brown quartzite and lower part of formation is red arkosic sandstone. Thickness 65–80 m

Mylonite (Middle(?) Proterozoic)—Mylonite; matrix commonly black; strongly laminated, glassy matrix surrounds 

rounded grains of potassium feldspar. Only mapped 

where strongly developed in granodioritic gneiss (Xgrgn) 

and amphibolite (Xa) in southeastern part of map area, 

but mylonitic fabric is present locally in almost all other 

Proterozoic rock units. Age uncertain, but younger than 

granodioritic gneiss (Xgrgn) and probably amphibolite 

(Xa)

Granite (Middle Proterozoic)—Biotite-hornblende granite, 

granite gneiss, and quartz monzonite; epidote, apatite, and 

opaque minerals are common accessories. Light pinkish 

gray to brownish gray; predominantly medium grained 

and rarely coarse grained; holocrystalline in hand specimen; biotite bands present in many outcrops. Forms 

small pluton in south-central part of quadrangle where it 

intrudes biotite gneiss (Xgn) and garnet gneiss (Xggn). 

Assumed to be Middle Proterozoic in age because similar 

granites are that age in Gold Butte district 25 km south of 

quadrangle (Wasserburg and Lanphere, 1965)

Quartz monzonite (Early Proterozoic)—Biotite-hornblende 

quartz monzonite; sphene, apatite, and opaque minerals 

are common accessories. Light brownish white when 

fresh; weathers medium yellowish brown; coarse to medium grained; slightly to moderately developed foliation 

caused by alignment of hornblende and biotite. Occurs as 

dikes that intrude biotite gneiss (Xgn) in southwestern 

corner of quadrangle

Sillimanite-bearing gneiss and schist (Early Proterozoic)—Chiefly garnet-biotite-sillimanite-muscovite-quartz 

gneiss and schist; dark gray. Exposed only in extreme 

southeast corner of quadrangle

Garnet-bearing gneiss (Early Proterozoic)—Garnet-biotite 

paragneiss and schist; medium to dark gray with pink 

banding and splotches caused by abundant potassium 

feldspar; weathers dark reddish brown. Medium grained; 

porphyroblastic to crystalloclastic texture; well-developed 

foliation and incipiently developed to well-developed compositional layering locally forming bands 1–10 cm thick. 

Quartz, biotite, garnet, microcline, and oligoclase occur, in 

order of decreasing abundance. Garnet porphyroclasts 

are 0.5 mm to 1 cm in diameter, biotite plates are 

0.005–1 mm in diameter, feldspar grains are xenoblastic 

and 0.5–1 mm in diameter, and sillimanite is a common 

accessory occurring as minute prismatic crystals. Cut by 

numerous pegmatites. Occurs beneath Lower and Middle 

Cambrian Tapeats Sandstone (et) at many localities

Biotite-hornblende gneiss (Early Proterozoic)—Biotitehornblende gneiss; medium to light gray; weathers dark 

gray to dark brownish gray. Medium to coarse grained; 

banded into 2- to 5-cm-thick compositional layers in many 

areas, strong foliation elsewhere. Augen-biotite gneiss 

present locally with coarse pink microcline augens. 

Quartz, microcline, plagioclase, biotite, and hornblende 

are ubiquitous; accessories include sericite, apatite, opaque 

minerals, and sphene. Garnet rare. Occurs beneath Lower and Middle Cambrian Tapeats Sandstone (et) at many 

localities

Amphibolite (Early Proterozoic)—Amphibolite and hornblende-plagioclase gneiss; dark gray. Medium grained; 

0.5- to 2-cm-thick compositional bands are common and 

distinguish gneiss from amphibolite. In addition to banding, “salt and pepper” texture is common. Composition 

varies; in some areas rock is nearly 100 percent hornblende, in others hornblende and plagioclase are nearly 

equal. Present in southeastern part of quadrangle

Granodioritic gneiss (Early Proterozoic)—Chiefly biotitehornblende gneiss; includes small isolated pods of amphibolite. Dark gray; weathers dark brownish gray. Medium 

grained; well-developed, alternating light and dark compositional bands several centimeters to over 1 m thick. 

Commonly contains oligoclase, quartz, microcline, biotite, 

hornblende, and sillimanite. Present in southeast corner 

of quadrangle

Contact—Dashed where approximately located or projected 

on cross sections

Fault—Dashed where approximately located; dotted where 

concealed or projected on cross sections. Bar and ball on 

downthrown side. Opposed arrows indicate relative 

movement. In cross section B–B', T, movement toward 

viewer; A, movement away from viewer. Arrow shows direction and amount of dip

Strike and dip of bedding

Inclined

Vertical

Overturned

Strike and dip of foliation

Inclined

Vertical

Anticline

Syncline

INTRODUCTION

The Riverside quadrangle lies along the eastern edge of the Basin 

and Range province in southeastern Nevada. The map area extends from 

the Virgin Mountains northward to the edge of Mormon Mesa, and is traversed in its northern part by the narrow, incised valley of the Virgin River (fig. 1). Most of the map area lies in the southwestern part of the Virgin River depression (Bohannon and others, 1993).

The Virgin River depression, about 28 km wide, lies between the 

Mormon Mountains (maximum altitude 2,260 m) and East Mormon 

Mountains to the northwest and the Virgin Mountains (maximum altitude 

2,356 m) to the southeast and east. The Mormon Mountains are within 

the Sevier thrust belt, where a thin sheet of allochthonous lower Paleozoic 

strata tectonically overlies an autochthon consisting of Paleozoic and lower Mesozoic rocks. Detachment faulting associated with middle Miocene 

extension has produced strong local tilts, exposing Precambrian rocks at a 

few localities (Axen and others, 1990), notably in the East Mormon 

Mountains. The Virgin Mountains are entirely east of the thrust belt and 

they contain a complete, but dismembered section of autochthonous Paleozoic and Mesozoic strata. Strong uplift in the Virgin Mountains associated with middle Miocene extension and strike-slip faulting has resulted in 

the exposure of Proterozoic crystalline rocks along the entire southwest 

edge of the Virgin River depression.

The southern half of the Riverside quadrangle is within part of the 

uplifted strike-slip zone that marks the northwestern flank of the southern 

part of the Virgin Mountains. The quadrangle straddles the southwest 

end of Bunkerville Ridge, which is a complexly faulted and broken ridge 

of steeply dipping Paleozoic strata. The northern half of the quadrangle 

is covered by alluvium deposits that have developed within the Virgin River depression to the north of the uplifted zone.

Along the west side of the Virgin River depression, Mormon Mesa, at 

an altitude of about 560 m, is an erosional remnant of lacustrine and fluvial basin-fill deposits of the Muddy Creek Formation, the flattish top of 

which is underlain by an ancient, thick, resistant carbonate-rich calcrete 

soil (Gardner, 1972a). The Virgin River flows westward and southward 

from an altitude of about 550 m where it debouches from its gorge 

through the Virgin Mountains to an altitude of about 335 m at Lake Mead 

at the south end of Mormon Mesa (fig. 1). Piedmont plains rise steeply 

from the river to about 1,000 m altitude against the rugged Virgin and 

Mormon Mountains.

Identification of the deposits that post-date the Miocene Muddy 

Creek Formation are based mostly on topographic position, soil development, topographic expression, amount of dissection by washes that head 

within a deposit (internal dissection), and, to a lesser extent, on lithology 

and depositional environment. These criteria are described in detail in 

Hoover and others (1981).

Ages of post-Muddy Creek Formation deposits have not been determined by numerical dating techniques. Ages assigned to surficial deposits 

in this quadrangle are estimated on the basis of similarity of desert-varnish 

development, etching of carbonate clasts, packing of desert pavement, 

and comparison of the stage of soil-carbonate development (Gile and others, 1966) to that observed for Quaternary deposits at the Nevada Test 

Site, about 170 km northwest of the map area, where many numerical 

ages have been determined (Hoover, 1989).

The Riverside quadrangle lies in a transitional setting between the 

miogeoclinal section of Paleozoic and lower Mesozoic rocks to the west in 

the southeastern Great Basin province and the platform sequence of Paleozoic and Mesozoic rocks in the Colorado Plateaus province to the east. 

The quadrangle is in an area of east-to-west facies changes and westward 

thickening of Paleozoic strata. Because of this, the stratigraphic nomenclature established for rocks of the Colorado Plateaus province, chiefly in 

southern Utah and the Grand Canyon region, differs from that used regionally in the southern Great Basin. For example, the rock column of 

the Great Basin represents more geologic time and is subdivided into 

more stratigraphic units. In the Riverside quadrangle, we have incorporated geologic names from both of these provinces, and the nomenclatures have been interchanged. This choice was dictated by our assessment of the local stratigraphy and its similarity to other sections described 

in the literature. Certainly many alternative choices are possible.

Proterozoic rocks in the Riverside quadrangle and surrounding areas 

have been mapped and studied by Beal (1965). Where possible, we have 

tried to conform to his terminology. Parts of the rock descriptions used 

here, primarily mineralogical and textural information, are taken from 

Beal (1965).

GEOLOGIC HISTORY AND STRUCTURE

VIRGIN RIVER DEPRESSION

The Virgin River depression is a large tectonic basin that was extensionally deformed during Miocene time and filled with a thick sequence of 

basin-fill deposits. The upper part of the basin-fill deposits, the Muddy 

Creek Formation, averages about 1 km in thickness (Bohannon and others, 1993) and is widely exposed within the depression. Basalts within 

the Muddy Creek Formation have been dated at about 11.5–5.5 Ma (Miocene). The formation is mostly well-bedded, moderately consolidated, 

fluvial silt and sand in the Virgin River depression (Kowallis and Everett, 

1986), but to the west and southwest of the depression the formation is 

composed mostly of lacustrine deposits. The Muddy Creek basin of interior drainage was abruptly incised when the Colorado River and its tributaries were integrated through the present-day Lake Mead area.

The top of the Muddy Creek Formation and the adjacent piedmont 

slopes were deeply entrenched by newly established tributary drainages of 

the Virgin River system after the Muddy Creek basin was drained. Entrenchment resulted in erosional isolation of large parts of the lake floor 

and adjacent piedmont slopes. A thick calcrete developed during the Pliocene and Quaternary on the flat and gently sloping deposits; the 3-m-thick 

cap rock on Mormon Mesa is a classic example of this ancient calcrete.

By the beginning of Quaternary time the Colorado River–Virgin River system had entrenched itself to its present depth. All the Quaternary 

terrace deposits along the perennial Virgin River are the result of cyclical 

aggradation and degradation caused mostly by climatic fluctuations. The 

aggradational silt and sand deposits were probably the products of pluvial 

episodes during the Quaternary. The piedmont side streams had base 

levels controlled by the Virgin River. These side streams deposited inset 

fan and inset channel gravels in response to climatic fluctuations, possibly 

modified by Tertiary and Quaternary tectonic deformation associated with 

uplift of the Virgin Mountains.

The Tertiary and Quaternary alluvial deposits of the Riverside quadrangle are divided into four categories according to source of sediment and 

environment of deposition. For each category two to seven generations 

of deposits have been distinguished by geomorphic and pedogenic criteria.

Mainstream deposits of the Virgin River are predominantly sand and 

gravel and include little silt or clay. The gravel consists of a mixture of 

subangular Precambrian, Paleozoic, and Mesozoic detritus from the adjacent ranges as well as distinctive well-rounded cobbles of chert, quartzite, 

and volcanic rocks from the uplands of southwestern Utah and volcanic 

areas near Caliente, to the north. Flights of terraces indicate at least 

three prior intervals of deposition at levels about 6, 20, and 115 m above 

the modern channel (420–445 m elevation). The surface at 115 m (530 

m altitude) tops a fill more than 115 m thick (QTv, Qav, and Qgv) and 

records a major period of aggradation.

Alluvium from major tributaries on the north side of the river, such as 

Toquop Wash, is dominated by rocks eroded from the Mormon Mountains, and includes abundant carbonate clasts. Toquop Wash terraces 

record substantial lateral shifting of the channel and at least five prior intervals of deposition at about 6, 20, 35, 55, and 80 m (510 m altitude) 

above the modern channel. The lower two Toquop Wash terraces are 

graded to fill terraces along the Virgin River. The other Toquop terraces 

may be graded to strath terraces along the Virgin River that have formed 

by stripping of sandy alluvium from cemented gravels in the thick Virgin 

River fill (QTv, Qav, and Qgv).

Minor tributaries on the north side of the river deposited alluvium derived by erosion of the escarpment of Muddy Creek Formation exposed 

on the east side of Mormon Mesa and by reworking of high terrace deposits of the Virgin River. Such tributaries deposited thin layers of sandy 

pediment alluvium that includes well-cemented angular boulders eroded 

from the calcrete on the surface of Mormon Mesa. The deposits cover a 

bench between the Mormon Mesa escarpment and the inset canyon of 

the Virgin River, and are graded to resistant ledges of cemented Virgin 

River terrace gravels (QTv) 50–60 m above the modern Virgin River 

channel. Surfaces of sandy pediment alluvium occur at various levels that 

are grouped into younger (Qys) and older (Qyms) divisions.

Tributaries on the south and east side of the Virgin River have deposited coarse alluvium dominated by angular clasts of metamorphic and igneous Proterozoic rocks derived from the Virgin Mountains. These deposits form alluvial fans, thin alluvial mantles on pediment surfaces cut on 

older alluvium, and stream terraces inset into alluvial fans. At least six prior depositional intervals are recorded. The last five correspond approximately to terrace levels along the Virgin River and Toquop Wash, whereas the oldest depositional interval, represented by alluvium of Bunkerville 

Ridge (Tab), was probably contemporary with the upper part of the Muddy Creek Formation.

The alluvium of Bunkerville Ridge (Tab), the oldest and most widespread piedmont deposit in the Riverside quadrangle, underlies about twothirds of the piedmont slope below the Virgin Mountains in the central 

part of the map area. The alluvium consists of coarse poorly sorted bouldery gravel, sandy gravel, and gravelly sand eroded from the Virgin Mountains during late Tertiary time. The deposit is dissected 20–150 m deep 

by tributary streams of the Virgin River, and its surface, entirely erosional, 

has rounded bouldery interfluves. Remnants of a stage IV–V carbonaterich soil 3–6 m thick underlie these eroded interfluves.

On the lower part of the piedmont slope, remnants of five Pleistocene fan deposits are deeply inset below the ridges of the alluvium of 

Bunkerville Ridge (Tab) and above the modern depositional surface (Qan). 

They overlie the easily eroded silt and sand of the Muddy Creek Formation. The fan deposits consist mostly of eroded detritus from the alluvium 

of Bunkerville Ridge. The oldest of the inset fan deposits (Qom) is preserved only as a few scattered rounded radial ridges (ballenas as defined 

by Peterson, 1981). None of the original depositional surface is preserved. The next youngest (Qmm) has been reduced to ballenas in the 

western part of the map area but retains a greater proportion of its original depositional surface toward the east (upstream). It is entrenched as 

much as 55 m and locally contains remnants of a stage IV carbonate-rich 

soil. The third youngest fan deposit, younger middle mountain-side 

alluvium (Qymm), consists mostly of sandy gravel and has a preserved depositional surface that overlies a stage II–III carbonate-rich soil capped by 

a tightly packed cobble and pebble pavement. Modern washes are entrenched 20–40 m below the depositional surface of this deposit. The 

second youngest deposit, the young mountain-side alluvial fan deposits 

(Qym), consists of sandy gravel and has a well-preserved depositional 

surface that overlies a stage II–III carbonate-rich soil capped by a firm cobble and pebble pavement. Modern washes are entrenched 20–30 m below the depositional surface of this deposit.

Holocene alluvium on the piedmont is restricted to narrow washes 

entrenched into the alluvium of Bunkerville Ridge (Tab) and Pleistocene 

alluvial deposits. The alluvium of Nickel Creek (Qan) of late Pleistocene(?) 

to Holocene age constitutes the flood plains and low (<1.5 m) terraces of 

the modern piedmont washes.

The narrowness (0.3–1 km wide) of the entrenched valley of the Virgin River demonstrates the dominance of alluviation by the high-gradient, 

piedmont, side-stream washes over valley-widening lateral erosion by the 

Virgin River. The Virgin River meanders across the full width of its valley 

floor, giving it the appearance of an overfit stream. Its channel deposit is 

the channel sand of the Virgin River (Qsv), which consists of fine to medium sand, silt, and gravel. About 2–4 m above the active river channel are 

flood-plain deposits of the Virgin River (Qfv), which consist of overbank 

deposits of sand and subordinate amounts of sandy gravel and gravel.

BUNKERVILLE RIDGE—NORTHWEST FLANK OF

 VIRGIN MOUNTAINS

Bunkerville Ridge is an east-northeast-trending physiographic high on 

the west flank of the Virgin Mountains. The ridge is chiefly composed of 

Paleozoic strata that strike roughly parallel to the local trend of the physiographic high and dip northerly or are vertical to overturned to the north. 

The continuity of the ridge is broken in the Riverside quadrangle by two 

prominent low areas through which northeast-striking faults pass. These 

are in the south-central and southwestern parts of the quadrangle. These 

faults divide the ridge into three parts within the quadrangle, each with its 

own characteristics. In subsequent discussions these are referred to as the 

southwest, central, and northeast ridge segments. On the north side of 

the ridge, Pliocene and Quaternary alluvial strata of the Virgin River depression rest depositionally on the highly faulted Paleozoic rocks. The 

south side of the ridge is commonly marked by the depositional contact of 

the Tapeats Sandstone (et) on various Proterozoic crystalline rock units 

or by the two northeast-trending faults that have Paleozoic rocks on their 

northwest sides and Proterozoic rocks on their southeast sides. South of 

the ridge the quadrangle is underlain by various Proterozoic crystalline 

rocks that are faulted by two regionally prominent faults that have northeast trends, the Hen Spring and Cabin Canyon faults. The Hen Spring 

fault separates different gneiss units in the southeast corner of the quadrangle. In the adjacent Hen Spring 7 a-minute quadrangle to the east, 

the Hen Spring fault marks the southern edge of Bunkerville Ridge where 

it separates Paleozoic rocks from crystalline basement (Beal, 1965). The 

Cabin Canyon fault appears only in the extreme southeast corner of the 

Riverside quadrangle where it separates schist on the southeast from 

gneiss on the northwest.

The basal Cambrian strata that form the southwest ridge segment 

have intermediate northwest dips. A broad, open fold pair, whose axial 

plunge parallels the stratal dips, is defined by changes in strike of the 

beds. The syncline is well displayed, but the anticlinal axis is buried by 

Quaternary and late Tertiary deposits and is cut by a fault with a northeast 

trend. This suggests a sequence of events in which a flat section of Cambrian rocks was folded gently, later to be tilted more steeply and cut by 

faults. Both the large east-bounding fault and the one cutting the anticline 

exhibit a well-developed left separation of the basal Proterozoic-Cambrian 

contact. The separation on the fault between the southwest and central 

ridge segments is on the order of 1 km.

The central ridge segment is primarily a moderately northeast dipping homocline in Lower Cambrian to Mississippian rocks. Intermediate 

dips are common at high stratigraphic levels and steep dips are common 

near the base of the homocline. The Proterozoic-Cambrian contact is 

faulted in places and depositional in others, but it defines large open folds 

with northeast trends in the Proterozoic-Cambrian contact that are not 

obvious at higher levels in the homocline. Two large fault blocks rest tectonically above the homoclinal section of rocks. The faults beneath each 

block form two convex-up, spoon-shaped surfaces, each of which appears 

to plunge to the southwest, perpendicular to the strikes in the underlying 

homocline and to the orientation parallel to the basement crenulations. 

Northeast-dipping homoclines of Cambrian to Pennsylvanian rocks form 

the hangingwall blocks of each of the spoon faults. The stratigraphic separations suggest that each spoon was transported to the southwest relative to the underlying homoclinal block. The central part of the footwall 

homocline is offset with about 0.5 km of left separation by a northeasttrending fault that merges with the fault that forms the west-northwest 

side of the eastern spoon. The prominent northeast-trending fault that 

bounds the east side of this ridge segment has a well-developed left separation of the basement-Tapeats contact of almost 2.5 km.

The structural relations surrounding the two spoon-shaped fault surfaces suggest that they developed as a single normal fault surface that cut 

a flat-lying section of rocks. The original fault surface was probably gently 

crenulated and had a general northwest strike and a steep to intermediate 

southwest dip. Subsequent strong northeast tilting of both the hangingwall and footwall blocks resulted in the gentle southwest dip of the modern spoon-shaped surface. Erosion of much of the hangingwall preserved 

only the cuspate crenulations in the original surface.

The strata in the eastern ridge segment form a deformed north-dipping homocline. The basement–basal Cambrian contact is depositional 

and gently dipping all along this part of the ridge. Two small left-separation faults with north-northeast trends cut the contact. Strata in the higher stratigraphic levels in the homocline dip steeply to the north. At no 

point is there a complete section exposed in this segment of the ridge. A 

complex pattern of low- to intermediate-angle, north-dipping, normal 

faults disrupts the middle part of the homocline. Each of these faults locally eliminates part of the section, placing younger strata on older. At 

the eastern boundary of the quadrangle these faults merge into two, 

which in turn join with the Hen Spring fault to the east of the quadrangle. 

In map view the nearly continuous Tapeats Sandstone at the base of the 

homocline converges with Mississippian rocks in the homocline’s upper 

part at the eastern border of the quadrangle, indicating that, at that location, a large amount of section has been removed by the two faults.

A regional analysis suggests that the Hen Spring and Cabin Canyon 

faults are left-slip faults with approximately 20 km of offset (Anderson and 

Bohannon, 1993). The main evidence for this assertion comes from the 

apparent offset of basement types directly beneath the Tapeats Sandstone. The Tapeats lies on banded gneiss containing abundant, coarsegrained, pink potassium feldspar and quartz segregations everywhere to 

the north of the Hen Spring fault. These units are mainly the biotitehornblende quartz monzonite orthogneiss (Xgn) and the garnet-biotite 

paragneiss (Xggn). Beal (1965) showed that the Tapeats lies on either 

garnet-sillimanite-biotite pelitic schist with fine-scale banding or granodiorite gneiss just to the southeast of the map area, across the faults, at Virgin Peak (Anderson and Bohannon, 1993). The closest exposures of 

gneiss containing similar coarse-grained, potassium feldspar-rich segregations occurs south of the Front fault (which joins with the Hen Spring and 

Cabin Canyon faults to the east of the map area) about 5 km east of the 

Nevada-Arizona border (unit pegr of Moore, 1972).

REFERENCES CITED

Anderson, R.E., and Bohannon, R.G., 1993, Three dimensional aspects 

of the Neogene strain field, Nevada-Utah-Arizona tricorner area, in 

Lahren, M.M., Trexler, J.H., Jr., and Spinosa, Claude, eds., Crustal 

evolution of the Great basin and the Sierra Nevada: Cordilleran/ 

Rocky Mountain Section, Geological Society of America guidebook, 

Department of Geological Sciences, University of Nevada, Reno, p. 

167–196.

Axen, G.J., Wernicke, B.P., Skelly, M.F., and Taylor, W.J., 1990, Mesozoic and Cenozoic tectonics in the Sevier thrust belt of the Virgin River Valley area, southern Nevada, in Wernicke, B.P., ed., Basin and 

Range extensional tectonics near the latitude of Las Vegas, Nevada: 

Geological Society of America Memoir 176, p. 123–153.

Beal, L.H., 1965, Geology and mineral deposits of the Bunkerville mining district, Clark County, Nevada: Reno, Nev., Nevada Bureau of 

Mines and Geology, Bulletin 63, 96 p.

Bohannon, R.G., 1991, Geologic map of the Jacobs Well and southern 

part of the Elbow Canyon quadrangles, Mohave County, Arizona: 

U.S. Geological Survey Miscellaneous Investigations Series Map 

I–2167, scale 1:24,000.

Bohannon, R.G., Grow, J.A., Miller, J.J., and Blank, R.H., Jr., 1993, 

Seismic stratigraphy and tectonic development of Virgin River depression and associated basin, southeastern Nevada and northwestern Arizona: Geological Society of America Bulletin, v. 105, p. 

501–520.

Gardner, L.R., 1968, The Quaternary geology of the Moapa Valley, Clark 

County, Nevada: University Park, Pa., Pennsylvania State University 

Ph. D. dissertation, 162 p.

———1972a, Origin of the Mormon Mesa Caliche, Clark County, Nevada: Geological Society of America Bulletin, v. 83, p. 143–156.

———1972b, Pediments and terraces along the Moapa Valley, Clark 

County, Nevada: Geological Society of America Bulletin, v. 83, p. 

3479–3486.

Gile, L.H., Peterson, F.F., and Grossman, R.B., 1966, Morphological and 

genetic sequences of carbonate accumulation in desert soils: Soil Science, v. 101, p. 347–360.

Hewett, D.F., 1931, Geology and ore deposits of the Goodsprings quadrangle, Nevada: U.S. Geological Survey Professional Paper 162, 

172 p.

Hoover, D.L., 1989, Preliminary description of Quaternary and late Pliocene surficial deposits at Yucca Mountain and vicinity, Nye County, 

Nevada: U.S. Geological Survey Open-File Report 89–359, 45 p.

Hoover, D.L., Swadley, W C, and Gordon, A.V., 1981, Correlation characteristics of surficial deposits with a description of surficial stratigraphy in the Nevada Test Site region: U.S. Geological Survey OpenFile Report 81–512, 27 p.

Kowallis, B.J., and Everett, B.H., 1986, Sedimentary environments of 

the Muddy Creek Formation near Mesquite, Nevada, in Griffen, 

D.T., and others, eds., Thrusting and extensional structures and mineralization in the Beaver Dam Mountains, southwestern Utah: Utah 

Geological Association Publication 15, p. 69–75.

Longwell, C.R., 1928, Geology of the Muddy Mountains, Nevada, with a 

section through the Virgin Range to the Grand Wash Cliffs, Arizona: 

U.S. Geological Survey Bulletin 798, 152 p.

———1936, Geology of the Boulder Reservoir floor, Arizona-Nevada: 

Geological Society of America Bulletin, v. 47, p. 1393–1476.

Longwell, C.R., Pampeyan, E.H., Bowyer, Ben, and Roberts, R.J., 1965, 

Geology and mineral deposits of Clark County, Nevada: Nevada Bureau of Mines and Geology Bulletin 62, 218 p.

McKee, E.D., 1945, Stratigraphy and ecology of the Grand Canyon 

Cambrian, Part I of Cambrian history of the Grand Canyon region: 

Carnegie Institution of Washington Publication 563, p. 1–170.

———1974, Paleozoic rocks of the Grand Canyon, in Geology of the 

Grand Canyon, The Paleozoic: Flagstaff, Ariz., Museum of Northern 

Arizona, p. 42–64.

———1975, The Supai Group; subdivision and nomenclature: U.S. 

Geological Survey Bulletin 1395–J, p. J1–J11.

———1982, The Supai Group of Grand Canyon: U.S. Geological Survey Professional Paper 1173, 502 p.

Moore, R.T., 1972, Geology of the Virgin and Beaverdam Mountains, 

Arizona: Arizona Bureau of Mines Bulletin 186, 65 p.

Peterson, F.F., 1981, Landforms of the Basin and Range Province defined for soil survey: Nevada Agricultural Experiment Station, University of Nevada Technical Bulletin 28, 52 p.

Sorauf, J.E., and Billingsley, G.H., 1991, Members of the Toroweap and 

Kaibab formations, Lower Permian, northern Arizona and southwestern Utah: The Mountain Geologist, v. 28, no. 1, p. 9–24.

Wasserburg, G.J., and Lanphere, M.A., 1965, Age determinations in the 

Precambrian of Arizona and Nevada: Geological Society of America 

Bulletin, v. 76, no. 7, p. 735–758.

GEOLOGIC QUADRANGLE MAP

RIVERSIDE QUADRANGLE, NEVADA

GQ–1770 (SHEET 2 OF 2)

Any use of trade names in this publication is for

descriptive purposes only and does not imply 

endorsement by the U.S. Geological Survey

25

80

75

85

Toquop

Wash

alluvium

Mesa-side

pediment and

fan alluvium

Mountain-side

pediment and

fan alluvium

Virgin

River

alluvium

Sedimentary

rocks

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

Unconformity

CORRELATION OF MAP UNITS

late

Pleistocene

middle 

Pleistocene

early

Pleistocene

Holocene

Pleistocene

QUATERNARY

Pliocene

Miocene

Lower Permian

Upper Mississippian

Lower Mississippian

Upper Devonian

TERTIARY

PERMIAN

PENNSYLVANIAN

MISSISSIPPIAN

DEVONIAN

Qan

Tab

Qc

Qe

Tmc

Pkh

Pkfm

Ptwr

Ptbc

Pts

Pe

Phb

Mm

MDsc

Dsv

Hill slope

deposit

Eolian

sand

Unconformity

Upper Cambrian

Middle Cambrian

Lower Cambrian

CAMBRIAN

MIDDLE 

PROTEROZOIC

Xgrgn

emsr

Unconformity

Unconformity

Unconformity

et

eb

el

ec

Metamorphic and

igneous rocks

Ym

Ygr

Xqm

Xs Xggn Xgn

Xa

EARLY 

PROTEROZOIC

emkp

emgy

emgg

emgw

emh

emst

ed

en

eu









 



   

  



 















Qsv Qfv 

Qtv

Qyv Qyt

Qymt

Qmt

Qot Qgv

Qav

QTv

Qym

Qymm

Qmm

Qom

Qys

Qyms

Qs

Tmca

Qan

Qc

Qe

Tab

Tmc

Pkh

Pkfm

Ptwr

Ptbc

Pts

Pe

Phb

Mm

MDsc

Dsv

en

ed

eu

emst

emh

emgw

emgg

emgy

emkp

emsr

ec

el

eb

et

Ym

Ygr

Xqm

Xs

Xggn

Xgn

Xa

Xgrgn









 





 

 

 



 



 

 







 

 







Qsv

Qfv

Qs

Qtv

Qyv

Qyt

Qym

Qys

Qymt

Qymm

Qyms

Qmt

Qmm

Qgv

Qav

Qot

Qom

QTv

Tmca

Pahranagat

Wash

Meadow

Valley

Wash

California

Wash

Muddy

River

Virgin

River

Toquop

Wash

i15

Riverside

quadrangle

Virgin

Mountains

Bunkerville Ridge

Mormon

Mesa

East

Mormon

Mountains

Mormon

Mountains Meadow

Valley

Mountains

North

Muddy

Mountains

Arrow Canyon Range

GLENDALE

BASIN

VIRGIN

RIVER

DEPRESSION

Moapa Glendale

Logandale

Overton

Riverside

Mesquite

36°30'

37°

115° 114°30'

0

0

10 20 30 KILOMETERS

10 20 MILES

NEVADA

Area of

figure 1

Figure 1. Regional index map.

Lake

Mead

U.S. DEPARTMENT OF THE INTERIOR

U.S. GEOLOGICAL SURVEY

GEOLOGIC MAP OF THE RIVERSIDE QUADRANGLE, CLARK COUNTY, NEVADA

By

Van S. Williams, Robert G. Bohannon, and D.L. Hoover

1997