Surficial Geologic Map of the Ivanpah 30' x 60' 

Quadrangle, San Bernardino County, California, and Clark 

County, Nevada 

By David M. Miller 

Pamphlet to accompany 

Scientific Investigations Map 3206

2012

U.S. Department of the Interior 

U.S. Geological Survey 
ii

U.S. Department of the Interior 

KEN SALAZAR, Secretary 

U.S. Geological Survey 

Marcia K. McNutt, Director 

U.S. Geological Survey, Reston, Virginia: 2012

For product and ordering information: 

World Wide Web: http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS 

For more information on the USGS—the Federal source for science about the Earth, 

its natural and living resources, natural hazards, and the environment: 

World Wide Web: http://www.usgs.gov

Telephone: 1-888-ASK-USGS 

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government. 

Although this report is in the public domain, permission must be secured from the individual 

copyright owners to reproduce any copyrighted material contained within this report. 
iii

Contents 

Explanatory Notes ............................................................................................................................................................................1

Mapping Methods .........................................................................................................................................................................1

Map Classification ........................................................................................................................................................................1

Composite Symbols .....................................................................................................................................................................1

Conventions for Erosional Environments .....................................................................................................................................1

Quaternary Faults ............................................................................................................................................................................2

Cedar Canyon Area .....................................................................................................................................................................2

Cima Area ....................................................................................................................................................................................3

Cinder Cones Lava Beds and Old Dad Mountain Area ................................................................................................................3

Bristol Mountains ..........................................................................................................................................................................3

Acknowledgments ............................................................................................................................................................................4

Description of Map Units ..................................................................................................................................................................5

Depositional Landscape ...............................................................................................................................................................5

Anthropogenic Deposits ...........................................................................................................................................................5

Valley-axis Deposits .................................................................................................................................................................5

Wash Deposits.........................................................................................................................................................................5

Alluvial and Debris-Flow Deposits ............................................................................................................................................6

Eolian Deposits ........................................................................................................................................................................8

Mixed Alluvial and Eolian Deposits ..........................................................................................................................................8

Playa Deposits .........................................................................................................................................................................9

Lacustrine Deposit .................................................................................................................................................................10

Groundwater-Discharge Deposits ..........................................................................................................................................10

Erosional Landscape ..................................................................................................................................................................10

Colluvial and Landslide Deposits ...........................................................................................................................................10

Hillslope Deposits ...................................................................................................................................................................11

Pediment Surfaces .................................................................................................................................................................11

Volcanic Rocks ...........................................................................................................................................................................12

Substrate Materials ....................................................................................................................................................................12

References Cited ...........................................................................................................................................................................13

Tables 

Table 1. Characteristics of faults that are known to be, or that probably are, Quaternary in age. ..............................................2
This page intentionally left blank
1

Surficial Geologic Map of the Ivanpah 30' x 60' 

Quadrangle, San Bernardino County, California, and 

Clark County, Nevada 

By David M. Miller 

Explanatory Notes 

Mapping Methods 

This map was compiled from detailed surficial geologic maps where available (see index 

map and list of map sources, map sheet). The remainder was mapped at the scale of 1:100,000 by 

standard field methods and interpretation of remote-sensing images, including aerial photography 

and Landsat 7 data. Field methods included examining the geomorphology, surface and internal 

features, and soil development. Mapped geology was transferred from aerial photographs to GIS by 

digitizing, using mosaics of digital orthophoto quadrangles. Digitizing was conducted at screen 

scales of 1:25,000 to 1:35,000 to provide location accuracy. 

Map Classification 

Mapping followed the approaches developed by Yount and others (1994) that describe 

surficial deposits according to a matrix of age and depositional process. Unit symbols reflect this 

breakdown into age and process. However, in erosional environments, landform and surficial-cover 

attributes are described by the map-unit symbols, and age is generally not provided because the 

environments are spatially nonuniform with respect to age. 

Composite Symbols 

Surficial geologic units commonly form thin (<2 m) veneers over older surficial units and 

bedrock. In map areas where this relation is common, the unit labels designate two units separated 

by a slash (/). The younger, or overlying, unit is indicated first. Thus, Qya/Qoa indicates an area 

where a veneer of young alluvial fan deposits (Qya) overlies old alluvial fan deposits (Qoa), and 

Qya/fpg indicates an area where a veneer of young alluvial fan deposits (Qya) overlies felsic, 

grussy granite (fpg).

The lateral extent of individual deposits is commonly so small that each exposure cannot be 

shown individually at the map scale. Areas made up of deposits too small to show at map scale 

(representing >20% of the area) are indicated by unit labels separated by a plus sign (+); the most 

common deposit is listed first. Thus, Qya+Qia indicates an area that contains both Qya and Qia

deposits, and Qya is more common than Qia.

Conventions for Erosional Environments 

Erosional environments such as mountains and pediments are widespread and consist of 

thin, surficial sediment distributed irregularly among bedrock exposures. Materials in mountain 

areas are largely formed in place by weathering of the bedrock but may be transported short 

distances by mass-wasting and fluvial processes. Such materials are designated as “hillslope 
2

materials” regardless of transport mechanism. Thicker, areally consistent, and mappable hillslope 

sediment is distinguished as colluvium and landslide deposits. Pediments in this area are primarily 

Miocene in age (Dohrenwend, 1988; Miller, 1995) but have continued to evolve into the 

Quaternary, because Quaternary deposits are associated with many pediment surfaces. Map labels 

for both pediment and hillslope deposits include the underlying bedrock type. Bedrock material is 

classified in ten map units based on chemical composition and weathering characteristics. 

Pediments are erosional surfaces that present special challenges for mapping. They exhibit 

varying degrees of incision and cover by a sediment veneer, are formed in varying substrate rocks 

and deposits, and vary in age. Pediments are represented on the map by two unit labels separated 

by a hyphen (-). The first unit label indicates the degree to which the pediment is dissected and the 

second label indicates the substrate material. Thus, Qpv-fpg indicates a veneered pediment (Qpv) 

cut into grus-forming felsic plutonic rock (fpg).

Quaternary Faults 

Faults that probably ruptured Quaternary deposits are recognized in four areas of the 

Ivanpah 30' x 60' quadrangle. The faults do not appear to be Holocene in age. They are summarized 

below and in table 1. 

Table 1. Characteristics of faults that are known to be, or that probably are, Quaternary in age. 

 

 Fault 

Orientation Last rupture 

Striae Geomorphic expression Strike (°) Dip (°) Unit cut Unit uncut

Cedar Canyon 050 75 S. QToa Qiag none none

Round Valley 330 Qoa Qia none faceted ridges; vegetation lineaments

Cima 025 Miocene Qiag none linear hill front

Lava Beds E. 334 57 W. Miocene ~450 ka basalt none three strands in wash cuts

Lava Beds W. 311 58 E. QToa? Qia 13° SE. possible lineament in Qia

Old Dad 330 72 E.? Qoa Qia none linear mountain front

Bristol E. Miocene Qia? none linear mountain front

Bristol W. 320 90 Qia11 Qya4236° SE. scarp 1–2 m high

1Unit Qia1 is a subdivision of unit Qia mapped locally near faults but not shown on the map and is approximately 30 

ka (Miller and others, 2010). 

2Unit Qya4 is a subdivision of unit Qya mapped locally near faults but not shown on the map and is approximately 14 

to 9 ka (Miller and others, 2010).

Cedar Canyon Area 

The Cedar Canyon Fault (Hewett, 1956) lies in Cedar Canyon and separates rocks in Pinto 

Mountain from those in the Mid Hills. To the northeast, it separates rocks in the Blind Hills from 

those in the New York Mountains. In the easternmost exposure of the fault, it cuts not only bedrock 

but also surficial gravel assigned to unit QToa on the basis of the lack of original landform and the 

lack of soils in the bouldery deposit. Therefore, this fault ruptured during or after Pliocene to early 

Pleistocene time, but timing is imprecise because the local units are not dated directly. A parallel 
3

trace of the fault in the Blind Hills (Miller and others, 1991) does not demonstrably cut Quaternary 

deposits and, therefore, is not shown on the map.

Near the west end of the mapped Cedar Canyon Fault, two north-northwest-striking faults 

create sharp photo lineaments, scarps, and linear mountain fronts (Round Valley, table 1). No 

exposures of faults were confirmed in the field, but old alluvium appears to be cut by one fault to 

form a rounded scarp and intermediate alluvium is not cut. Lineaments defined by enhanced 

vegetation and topographic steps in Round Valley appear to represent continuations of the faults. 

These faults apparently are middle Pleistocene and older. 

Cima Area 

Three kilometers southwest of the town of Cima, California, Miocene gravels underlie a hill 

that rises above the surrounding subdued plain. The hill has a linear, steep northwest side and 

dissected, eroded, more gently sloping southeast side. Gravels underlying the hill are similar to 

those in the adjacent plain, suggesting that the topographic relief may reflect young faulting. No 

Quaternary deposits are cut by the presumed fault along the linear margin of the hill, but the 

preserved lineament in readily eroded sediment may indicate a Pliocene to Pleistocene age for last 

rupture on the presumed fault. 

Cinder Cones Lava Beds and Old Dad Mountain Area 

Skirvin and Wells (1990) described several Quaternary faults cutting middle Pleistocene 

lava flows in the Cinder Cone Lava Beds area northeast of Kelbaker Road and similar faults to the 

southwest near Old Dad Mountain. Our investigations in the lava beds area failed to establish that 

these faults cut the lava flows. Our interpretation is that most faults are older than middle 

Pleistocene lava flows, yet they exhibit scarps in readily eroded Miocene gravel and, therefore,

may be early Quaternary in age. The faults are difficult to trace more than a few kilometers beyond 

the area of lava flows. The western fault (Lava Beds West) is exposed in wash cuts, where it 

exhibits breccia in sediment overlying Proterozoic gneiss, all of which is overlain by unfaulted late 

Pleistocene unit Qia sediment and unfaulted lava flows dated at 130±60 ka to 170±60 ka 

(Dohrenwend and others, 1984). A lineament that lies northwest of the faults exposed in wash cuts 

may represent inherited topography or faults displacing unit Qia. The former interpretation is 

indicated by the weight of the field evidence. Two kilometers to the northeast (Lava Beds East), 

three parallel fault zones are exposed in a wash, each overlapped by Pleistocene (460±80 ka; 

Dohrenwend and others, 1984) lava flows. Spectacular wash-bank exposures of the faults 

demonstrate that the faults cut Miocene gravel but not the lava flows. 

A fault along the southwest front of Old Dad Mountain cuts old colluvium, based on stage 

III+ calcic soil development, and does not cut late Pleistocene unit Qia deposits. The precipitous 

linear southwest front of Old Dad Mountain was apparently created by significant displacement 

along faults that are largely older than middle Pleistocene deposits that flank the mountain front. 

No evidence was found that supports a Quaternary age for faults along the northeast side of Old 

Dad Mountain. 

Bristol Mountains 

In the southwest corner of the Ivanpah quadrangle, Brady (1992) mapped several strike-slip 

faults cutting Miocene sediment in the Bristol Mountains and described one segment as cutting 

Quaternary deposits. No indisputably ruptured Quaternary deposits were noted during field 

investigations in the Ivanpah map area, but two of the fault segments mapped by Brady in the 
4

Ivanpah quadrangle are possibly Quaternary in age, based on straight, modestly eroded scarps in 

moderately indurated Miocene sediment. Each segment exhibits several splays. Farther south, 

Bedford and others (2006) demonstrated that late Pleistocene deposits are cut by some of these 

fault segments. Data in table 1 summarize observations in both the Ivanpah and Amboy map areas. 

Acknowledgments 

I thank the following individuals for sharing data and ideas that contributed to this report: 

David Bedford, John Dohrenwend, Rick Forester, Richard Hereford, Keith Howard, Nick 

Lancaster, Shannon Mahan, Eric McDonald, Les McFadden, Chris Menges, Geoff Phelps, Sue 

Phillips, Marith Reheis, Bob Reynolds, Kevin Schmidt, Paul Stone, Bob Webb, Steve Wells, 

Yvonne Wood, and Jim Yount. Many more individuals contributed valuable information by 

helping in the field and lab. Reviews by David Bedford and George Billingsley improved early 

versions of this manuscript and are greatly appreciated. 
5

DESCRIPTION OF MAP UNITS 

DEPOSITIONAL LANDSCAPE

ANTHROPOGENIC DEPOSITS

ml Made land or artificial fill (latest Holocene)—Material moved for 

construction purposes and agricultural disturbances sufficiently extensive 

to make landforms and deposits difficult to identify 

VALLEY-AXIS DEPOSITS 

Qav Active valley-axis deposit (latest Holocene)—Fine-grained deposits in valley 

axes characterized by anastamosing washes; complex, subtle interfluves; 

and complexly interfingering eolian sediments. Composed of moderately 

to poorly sorted fine gravel, sand, silt, and clay. Loose. Prone to 

flooding. Moderately vegetated. Contacts with active wash and fan 

deposits somewhat arbitrary 

Qyv Young valley-axis deposit (Holocene and latest Pleistocene)—Fine-grained 

deposits in largely inactive valley-axis locations characterized by 

anastamosing washes, gentle interfluves, and complexly interfingering 

eolian sediments. Composed of moderately to poorly sorted sand, silt,

and clay. Loose. Moderately vegetated. Soil development similar to that 

for unit Qya

WASH DEPOSITS 

Qaw Active wash deposit (latest Holocene)—Fluvial wash deposits characterized by 

surfaces and channels actively receiving sediments within the last few 

decades. Composed of moderately to poorly sorted sand and gravel. 

Loose. Prone to flooding. Generally lacks vegetation on surfaces active 

on annual basis or moderately vegetated (with cheesebush Hymenoclea 

salsola) on surfaces or channels active on decadal basis. Little or no soil 

development. Mapped mainly where ephemeral stream flow is 

channelized; distributed stream flow generally mapped as active alluvial 

fan deposits (Qaa) or active valley-axis deposits (Qav). Major washes 

drain New York Mountains to south and southeast and drain Ivanpah and 

Kelso valleys. Generally light in tone on aerial photographs 

Qyw Young wash deposit (Holocene and latest Pleistocene)—Largely inactive 

fluvial wash deposits composed of moderately to poorly sorted sand and 

gravel. Loose. Moderately vegetated, commonly with creosote bush. 

Smaller fluvial-wash tracts generally designated young alluvial fan 

deposit (Qya), particularly where distributed across fan rather than in 

confined channels, but designation is somewhat arbitrary. Soil 

development similar to that for unit Qya. Generally forms alluvial 

terraces flanking active washes 

Qiw Intermediate wash deposit (late to middle Pleistocene)—Inactive remnant of 

alluvial wash sediments generally forming high terraces along edges of 

major wash systems. Moderately compact. Sparsely vegetated. Smaller 

wash tracts are generally designated as alluvial fan deposits (Qia). Soil 
6

development similar to that for unit Qia. Levee-shaped terraces flanking 

large washes draining south from New York Mountains are several 

meters high and mapped as unit Qiw; they grade laterally into unit Qiag,

and boundary is defined by edge of levee landform 

ALLUVIAL AND DEBRIS-FLOW DEPOSITS 

Qaa Active alluvial fan deposit (latest Holocene)—Alluvial fan deposits 

characterized by surfaces and channels actively receiving sediments 

within the last few decades. Composed of poorly sorted gravel and sand. 

Loose. Prone to flooding. Generally lacks vegetation on surfaces active 

on annual basis or moderately vegetated on surfaces or channels active 

on decadal basis. Rough microtopography; strongly developed bar and 

swale in much of fan; less pronounced in distal fan. Generally, the 

annually active surfaces are a small part of the unit and form discrete 

channels. Little or no soil development. Contacts with active wash 

deposits (Qaw) are somewhat arbitrary, with wash unit commonly 

assigned to consistently inset channels. Generally light in tone on aerial 

photographs 

Qaag Active alluvial fan deposit composed of grus—Predominately clasts from 

granitic source that weathers to grus. Surface undulating with smooth 

microtopography; little channel incision 

Qya Young alluvial fan deposit (Holocene and latest Pleistocene)—Alluvial fan 

deposits characterized by surfaces that are abandoned or that receive 

infrequent flood deposits. Composed of poorly sorted sand and gravel. 

Loose to slightly compact. Weakly developed soil, expressed as incipient 

to weak sandy Av horizon and weak cambic horizon; stage I or no calcic 

soil (calcic stages follow Gile and others, 1966). Fairly rough surface 

topography in much of fan with moderate to faint remnants of bar and 

swale topography. Moderately to sparsely vegetated, especially with 

creosote bush (Larrea tridentata) and smaller desert shrubs. Generally 

no desert pavement. Incipient to weak varnish on clasts. As mapped, 

includes narrow channels of active alluvial fan deposits 

Qyag Young alluvial fan deposit composed of grus—Clasts from granitic 

sources that weather to grus. Surface undulating and smooth; little 

channel dissection. Soils are immature; pavements and Av horizon rare. 

Unit is common downslope of Cretaceous granite outcrops 

Qyad Young alluvial fan deposit composed of debris-flow deposits—

Dominated by debris flows of bouldery, matrix-supported material. 

Mapped only where determined from field study; deposits are more 

widespread than shown. Common along west side of Providence 

Mountains 

Qia Intermediate alluvial fan deposit (late to middle Pleistocene)—Alluvial fan 

deposits characterized by surfaces that have been abandoned for tens of 

thousands of years. Composed of poorly sorted sand and gravel. Loose to 

compact. Characterized by moderately developed to well-developed 

desert pavement with moderate to strong varnish on clasts on flat smooth 
7

fan surface that is partly incised by narrow channels. Very sparsely 

vegetated. Well-developed platy Av horizon composed of silt, very fine 

sand, and clay. Moderately to strongly developed Bt horizon and Stage 

I+ to III+ calcic horizon. At maximum, soil development is similar to 

that for cumulic soil on ~450 ka lava flow near Seventeen Mile Point, 

Kelbaker Road (Wells and others, 1985, 1995). Oldest form of the 

intermediate fan unit in this vicinity is dated between ~600 ka and ~400 

ka (Dohrenwend, 1991). Generally distinguished on aerial photographs 

by lack of vegetation, dark varnish, and smooth surface with deeply 

incised active channels. Pavement, varnish, and Av horizon subdued to 

absent at high altitudes (above ~1,100 m); Bt horizon thicker at high 

altitude; calcic horizon thin. Moderately vegetated at high altitude 

Qiag Intermediate alluvial fan deposit composed of grus—Made up of clasts 

from granitic source that weathers to grus. Surface is broadly undulating 

and intermittently active. Deposit has poorly developed Av and Bt 

horizons, and calcic horizon is present but variably developed. Qiag

deposits are extensive in Lanfair Valley area 

Qiad Intermediate alluvial fan deposit composed of debris-flow deposits—

Dominated by debris flows. Poorly sorted bouldery deposits with sand 

and mud matrix. Mapped only where verified by field observations 

Qoa Old alluvial fan deposit (middle to early Pleistocene)—Alluvial fan deposits 

characterized by degraded remnants of abandoned surfaces forming 

bouldery ridges. Compact to cemented. Moderately vegetated. 

Commonly forms pale-colored ballenas above active washes in upper 

parts of alluvial fans near mountain fronts. Forms rounded, deeply 

dissected terrane with little or no remnant depositional geomorphology; a 

few meters to tens of meters higher than surrounding surfaces. Many 

clasts on surface made up of disaggregated pieces of calcic horizon, 

contributing to pale appearance on aerial photographs. Most upper soil 

horizons stripped off by erosion but commonly has superimposed weak 

soils developed directly on calcic horizon. In places may have remnant 

varnished pavement clasts on the surface with very thin or absent Bt 

horizon, suggesting the surface once had pavement characteristics that 

have since been eroded. Stage IV and greater calcic horizons 2–6 m 

thick. Deposit mapped west of Halloran Spring has intact landform 

unusual for unit Qoa but contains >3-m-thick calcic horizon; may have 

origin in part from groundwater discharge, but deposit does not contain 

ostracodes. Qoa deposits east of New York Mountains form high,

rounded ridges with scattered Bt horizons on thick stage IV calcic 

horizons; these are difficult to separate from deeply eroded Qia deposits 

and QToa deposits with superimposed soil development. Contains 

Bishop Ash (~770 ka) in several exposures a few kilometers south of 

quadrangle (McDonald, 1994) 

Qoag Old alluvial fan deposit composed of grus—Made up of clasts from 

granitic source that weathers to grus; commonly underlies undulating,

nearly flat topography and has inconsistently developed Bt horizon; 

incised by narrow channels that expose pronounced calcic horizon 
8

QToa Extremely old alluvial fan deposit (Pleistocene to Pliocene)—Deeply eroded 

alluvial fan deposits characterized by no remnants of abandoned surfaces 

and no intact soil horizons. Compact, bouldery. Moderately vegetated. 

Forms deeply dissected terrane with little or no remnant depositional 

geomorphology; deposits generally did not form in present topography, 

as indicated by source directions or clast composition. May have several 

sets of buried paleosols exposed in wash-cut profiles. As mapped, 

includes patches of younger alluvial deposits 

EOLIAN DEPOSITS 

Qae Active eolian sand deposit (latest Holocene)—Eolian sand deposits that are 

active and subject to migration. Loose. Generally lacks vegetation. 

Composed of moderately sorted to well-sorted sand. Most active eolian 

sand deposits lie within Devils Playground area from south of Soda Lake 

to Kelso Dunes, where they are sourced by Mojave River flood materials 

(Lancaster and Tchakerian, 2003). Sand sheets east of Ivanpah Lake 

sourced by that playa. Subunits are locally divided by geomorphology: 

Qaed Active eolian sand dune deposit—Well-sorted sand in dune landforms 

Qaer Active eolian sand ramp deposit—Sand and rock in steep mantles of 

hillsides, representing climbing and falling dunes 

Qye Young eolian sand deposit (Holocene and latest Pleistocene)—Eolian sand 

deposits that are generally inactive. Loose. Sparsely vegetated. 

Composed of moderately sorted to well-sorted sand. Little or no soil 

development but reddened zones representing incipient B horizons 

present in some deposits. Dated by luminescence methods in Kelso 

Dunes area as general pulses of eolian sand deposition from 0.5 to 1.6, 

3.5 to 4.3, and 8 to 10 ka (Clarke, 1994; Lancaster and Tchakerian, 

2003). Subunits are locally divided by geomorphology: 

Qyed Young eolian sand dune deposit—Well-sorted sand in subdued, somewhat 

eroded dune landforms 

Qyes Young eolian sand sheet deposit—Broad, low-relief sheets of well-sorted 

sand generally devoid of surface dune forms. Sparsely vegetated; 

probably 1–4 m thick in most places 

Qyer Young eolian sand ramp deposit—Sand and rock in steep mantles of 

hillsides, representing climbing and falling dunes. Typically cut by small 

stream channels 

MIXED ALLUVIAL AND EOLIAN DEPOSITS 

Qyae Young mixed alluvial and eolian sand deposit (Holocene and latest 

Pleistocene)—Alluvial and eolian sediments that are thoroughly mixed, 

with alluvial processes dominating. Forms flatter surfaces than alluvial 

systems lacking significant eolian sand, because eolian sand additions 

mute topography. Gravelly sand with vague to well-defined, thin 

bedding. Loose. Sparsely vegetated, generally supporting creosote bush. 

Little or no soil development. Contacts with units Qyea and Qya

laterally gradational 
9

Qyea Young mixed eolian sand and alluvial deposit (Holocene and latest 

Pleistocene)—Eolian and alluvial sediments that are thoroughly mixed, 

with eolian processes dominating. Alluvial channels muted or invisible; 

deposit mostly sand with sparse gravel. Forms broad, flat surfaces. 

Loose. Sparsely vegetated by grasses; little or no soil development. 

Deposits commonly in distal fan environment and extensive east of Soda 

and Ivanpah Lakes and near Kelso Dunes. Contacts with adjacent units 

typically gradational 

Qiae Intermediate mixed alluvial and eolian sand deposit (late to middle 

Pleistocene)—Alluvial and eolian sand sediments that are thoroughly 

mixed, with alluvial processes dominating. Forms flat surfaces with 

sparse vegetation. Gravelly sand with vague to well-defined, thin 

bedding. Characterized by inconsistently developed pavement and Bt 

and calcic horizons. Moderately compact. Contacts with units Qia and 

Qiea laterally gradational 

Qiea Intermediate mixed eolian sand and alluvial deposit (late to middle 

Pleistocene)—Eolian sand and alluvial sediments that are thoroughly 

mixed, with eolian processes dominating. Alluvial channels muted or 

invisible; deposit mostly sand with sparse gravel that exhibits moderately 

developed bedding. Characterized by flat surface, inconsistently 

developed pavement, and one or more Bt horizons and calcic horizons. 

Moderately compact. Sparsely vegetated. Unit is common east of Soda 

Lake area. Contacts with adjacent units are laterally gradational 

PLAYA DEPOSITS 

Qap Active playa deposit (Holocene)—Playas actively receiving sediments within 

the last few decades. Composed of weakly bedded, poorly sorted, silt, 

clay, and sand; includes salts in some places. Mud-cracked; in places cut 

by linear fissures that support salt desert scrub plants. Compact. Prone to 

flooding. Generally flat surface, sparse or no vegetation. Subject to 

stream flow and standing water associated with rainstorms and to eolian 

deposition and erosion associated with windstorms. Generally pale color 

on aerial photographs 

Qaps Active playa sandy facies deposit—Playa deposits that typically support sparse 

salt desert scrub vegetation, generally near margin of playa where 

alluvial sediments intertongue with playa sediments. White to brown, 

calcareous clay to sand at Ivanpah Lake 

Qypf Young playa fringe deposit (Holocene and latest Pleistocene)—Playa fringe 

deposits that are rarely flooded. Composed of silt, clay, and sand. 

Compact. Forms flat plains with sparse vegetation, mainly grasses with 

sparse creosote bush or salt bush (Atriplex spp.). Consists of complexly 

mixed eolian, lacustrine, playa, alluvial, and groundwater-discharge 

origins. Moderately well vegetated by many species, but saltbush 

(Atriplex sp.) is common. Present adjacent to Ivanpah Lake playa 

QTop Extremely old playa deposit (early Pleistocene and Pliocene)—Exhumed 

playa and (or) groundwater discharge deposits west of Piute Range. 
10

Forms badlands that expose reddish, vaguely bedded, sandy mud. Thick 

stage V calcic horizon formed in upper part of deposit may be 1–2 Ma in 

age (Katzenstein and others, 1995); overlain by intermediate alluvial fan 

deposit (Qia) 

LACUSTRINE DEPOSIT 

Qil Intermediate lacustrine deposit (late to middle Pleistocene)—Pluvial lake 

sediments adjacent to playas. Moderately sorted to well-sorted sand and 

mud. Buried lacustrine sediment along west side of Ivanpah Lake is 

reddish, muddy sand that may represent the most recent pluvial cycle, 

but is undated 

GROUNDWATER-DISCHARGE DEPOSITS 

Qags Active groundwater-discharge spring mound deposit (Holocene)—Deposits 

in moist zone of active groundwater discharge. Composed of silt and fine 

sand, generally white to pale gray in color. Loose to compact. Abundant 

vegetation except where water is highly saline. Generally disturbed by 

anthropogenic attempts at water development. Generally consists of 

low, broad marshy area, but forms two salt-grass-covered spring mounds 

at Valley Wells in Shadow Valley 

Qygs Young groundwater-discharge spring mound deposit (Holocene and latest 

Pleistocene)—Silt and fine sand in zones of former groundwater 

discharge, commonly with significant calcium carbonate in the deposit. 

Top of deposit typically is cemented calcium carbonate; commonly 

forms light-colored, flat areas or dissected badlands. Loose to compact. 

Little vegetation. Salt grass cover is common. Mounds typically 10–30 m 

wide and 1–3 m high 

Qygw Young groundwater-discharge wetland deposit (Holocene and latest 

Pleistocene)—Former wetland deposits in lower Kelso Wash that 

resemble those of spring mounds but form a broad planar deposit. Dated 

by luminescence at 13.3±0.7 to 13.9±0.8 ka (Miller and others, 2010) 

Qigw Intermediate groundwater-discharge wetland deposit (late to middle 

Pleistocene)—Marly silt and fine sand in former zones of groundwater 

discharge. Generally white to green and light brown; compact. Contains 

one or more pedogenic calcic horizons in places near Valley Wells. Little 

vegetation; generally dissected. Buried wetland deposits are widespread 

in Shadow Valley 

EROSIONAL LANDSCAPE 

COLLUVIAL AND LANDSLIDE DEPOSITS 

Qmc Mass-movement colluvial deposit, undivided (Holocene and Pleistocene)—

Colluvial materials thicker than 2 m and covering a wide area. Rocky 

and poorly sorted. Little soil development to strongly developed Bt 

horizon and pronounced desert varnish on surface clasts 

Qymc Young mass-movement colluvial deposit (Holocene and Pleistocene)—

Colluvial materials thicker than 2 m and covering a wide area. Rocky, 
11

loose, and poorly sorted; commonly with open space between clasts. 

Little soil development and varnish on surface clasts 

Qimc Intermediate mass-movement colluvial deposit (Pleistocene)—Colluvial 

materials thicker than 2 m and covering a wide area. Rocky and poorly 

sorted; fine material between clasts. Strongly developed Bt horizon; 

surface clasts generally strongly varnished. Local development of Stage 

II to III calcic horizon 

Qiml Intermediate mass-movement landslide deposit (Pleistocene)—Landslide 

deposits forming hummocky topography. In places, has well-defined 

scarp indicating source breakaway, as well as lobate tongues below 

scarp. Rocky, commonly with mud matrix; generally has weak desert 

pavement; variably developed varnish on surface clasts; and strongly 

developed Bt horizon 

HILLSLOPE DEPOSITS 

The hillslope environment is characterized by patchy distribution of bare rock, thin 

deposits weathered from rock, and materials transported short distances by gravity and by 

water. Identified with substrate rock type (following hyphen in unit symbol) 

Qha Abundant hillslope deposits (Holocene and Pleistocene)—Hillslope materials,

such as colluvium, talus, weathered rock, and landslide deposits, cover 

>50% of bedrock. Generally <2 m thick or patchy distribution with small 

fraction of area covered by deposits >2 m thick 

Qhs Sparse hillslope deposits (Holocene and Pleistocene)—Hillslope materials,

such as colluvium, talus, weathered rock, and landslide deposits, cover 

<50% of bedrock. Generally <2 m thick and patchy distribution 

PEDIMENT SURFACES 

Pediment surfaces are gently-sloping erosional surfaces in various stages of erosion and 

burial. Generally forms in grussy granite (fpg) and partly consolidated (pc) materials composed 

mainly of granite clasts. Substrate materials indicated after hyphen (-) in unit symbol. Excellent 

examples of pediments can be found between Halloran Summit and Cima Dome and in the Mid 

Hills, (Dohrenwend, 1988; Miller, 1995). Pediment surfaces are divided into three general 

classes by surface characteristics: 

Qpv Veneered pediment—Fairly smooth veneer of sediment, generally <2 m thick, 

is present on the pediment; soil development variable. Bedrock 

exposures in small knobs, roadcuts, and washes used to identify 

pediment. May be partly dissected 

Qpi Incised pediment—Incised pediment with most of the surface expressed as flat 

surfaces of bare rock with patchy veneer of sediment; channels cut into 

rock serve to transport eroded sediment 

Qpd Deeply dissected pediment—Deeply dissected pediment identifiable by similar 

heights of bedrock knobs and pinnacles. Area between pinnacles may be 

covered with sediment or is bare rock 
12

VOLCANIC ROCKS 

Volcanic flows, cinder cones, and other volcanic deposits emplaced during the 

Quaternary are distinguished, because they interfinger with surficial deposits and affect surface 

processes

Qmv Mafic volcanic rocks (Quaternary)—Lava flows and cinder cones of basaltic 

composition in the Cinder Cone Lava Beds. Consists mainly of lava 

flows with subordinate cinder cones. Lava-flow surfaces lie 5–30 m 

above modern pediments and exhibit pedogenic development similar to 

alluvial fans of similar ages (Dohrenwend and others, 1984; Wells and 

others, 1985). Most Quaternary lava flows range from ~10 to 450 ka 

(Wells and others, 1985, 1995; Phillips, 2003) 

SUBSTRATE MATERIALS 

Buried rock and partly consolidated materials that underlie surficial deposits and 

pediment and hillslope veneers. Ages range from Pliocene to early Proterozoic. Substrate 

materials are subdivided by weathering characteristics and erosional products: 

ca Carbonate rocks—Carbonate-mineral rocks, such as marble, dolomite, and 

limestone. Commonly weathers to silt 

fp Felsic plutonic rocks—Plutonic rocks greater than about 68% SiO2, such as 

granite and granodiorite 

fpg Felsic plutonic rocks that weather to grus—Mostly Cretaceous in age. 

Weathered materials are chiefly quartz, feldspar, and micas 

fv Felsic volcanic rocks—Volcanic rocks greater than about 68% SiO2, such as 

rhyolite, rhyodacite, and felsite. Includes flows and ejecta. Weathered 

materials include quartz, feldspar, and clay 

mp Mafic plutonic rocks—Plutonic rocks less than about 68% SiO2, such as 

gabbro, diorite, monzodiorite, syenite, and alkalic rocks. Weathered 

materials are chiefly feldspar, amphiboles, and micas 

mv Mafic volcanic rocks—Volcanic rocks less than about 68% SiO2, such as 

dacite, andesite, and basalt. Includes flows and ejecta. Weathered 

materials are clay rich; alluvial fans with mafic volcanic source 

commonly are mantled by darkly varnished boulders 

mr Metamorphic rocks—Metamorphic rocks of mixed lithology, such as gneiss, 

migmatite, and structurally mixed rocks. Weathered materials are 

variable 

pc Partly consolidated materials—Moderately to weakly consolidated 

sedimentary deposits such as sandstone and conglomerate; locally 

includes volcanic rocks or highly altered rocks. Typically Tertiary in age. 

May form badland topography. Weathered materials are enriched in silt 

and clay 

sl Siliciclastic rocks—Silicic sedimentary and metamorphic rocks, such as 

sandstone and quartzite, shale, and siltstone. Weathered materials are 

common quartz with subordinate silt and clay 
13

References Cited 

Bedford, D.R., 2003, Surficial and bedrock geologic map database of the Kelso 7.5-minute 

quadrangle, San Bernardino County, California: U.S. Geological Survey Open-File Report 

03-501, scale 1:24,000, 34 p., at http://geopubs.wr.usgs.gov/open-file/of03-501/. 

Bedford, D.R., Miller, D.M., and Phelps, G., 2006, Preliminary surficial geologic map database of 

the Amboy 30- x 60-minute quadrangle, California: U.S. Geological Survey Open-File Report 

2006–1165, 28 p., scale 1:100,000, at http://pubs.usgs.gov/of/2006/1165. 

Brady, R.H., III, 1992, The eastern California shear zone in the northern Bristol Mountains, 

southeastern California, in Richard, S.M., ed., Deformation associated with the Neogene eastern 

California shear zone, southwestern Arizona and southeastern California: Redlands, Calif., San 

Bernardino County Museum Special Publication, p. 6–10.

Castor, S.B., 1991, Tertiary and Quaternary gravels in the Mescal Range, San Bernardino County, 

California: Redlands, Calif., San Bernardino County Museum Association Special Publication, p. 

84–86. 

Clarke, M.L., 1994, Infra-red stimulated luminescence ages from aeolian sand and alluvial fan 

deposits from the eastern Mojave Desert, California: Quaternary Science Reviews, v. 13, p. 

533–538.

Dohrenwend, J.C., 1988, Age of formation and evolution of pediment domes in the area of Cima 

volcanic field, Mojave Desert, California, in Weide, D.L., and Faber, M.L., eds., This extended 

land: Geological Society of America Field Trip Guidebook, Cordilleran Section Meeting, p. 

214–217. 

Dohrenwend, J.C., 1991, Surficial geology of the Cima volcanic field, eastern Mojave Desert, 

California, in Reynolds, J., ed., Crossing the borders—Quaternary studies in eastern California 

and southwestern Nevada: Redlands, Calif., San Bernardino County Museum Special 

Publication, p. 60–66.

Dohrenwend, J.C., McFadden, L.D., Turrin, B.D., and Wells, S.G., 1984, K-Ar dating of the Cima 

volcanic field, eastern Mojave Desert, California—Late Cenozoic volcanic history and landscape 

evolution: Geology, v. 12, p. 163–167.

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. 

Goldfarb, R.J., Miller, D.M., Simpson, R.W., Hoover, D.B., Moyle, P.R., Olson, J.E., and Gaps, 

R.S., 1988, Mineral resources of the Providence Mountains Wilderness Study Area, San 

Bernardino County, California: U.S. Geological Survey Bulletin 1712–D, 70 p., scale 1:62,500. 

Hewett, D.F., 1956, Geology and mineral resources of the Ivanpah quadrangle, California and 

Nevada: U.S. Geological Survey Professional Paper 275, 172 p. 

Katzenstein, Y.A., Kendrick, K., and Knott, J.R., 1995, A preliminary assessment of calcic soil 

development at Piute Gorge, Fort Piute Wilderness, California: Redlands, Calif., San Bernardino 

County Museum Association Quarterly, v. 42, no. 3, p. 125–126.

Lancaster, N., and Tchakerian, V.P., 2003, Late Quaternary eolian dynamics, Mojave Desert, 

California, in Enzel, Y., Wells, S.G., and Lancaster, N., eds., Paleoenvironments and 

paleohydrology of the Mojave and southern Great Basin deserts: Geological Society of America 

Special Paper 368, p. 231–249.

McDonald, E.V., 1994, The relative influences of climate change, desert dust, and lithologic 

control on soil-geomorphic processes and soil hydrology of calcic soils formed on Quaternary 
14

alluvial-fan deposits in the Mojave Desert, California: Albuquerque, University of New Mexico,

unpublished Ph.D. Dissertation. 

Miller, D.M., 1995, Characteristics, age, and tectonic implications of the Mid Hills pediment: 

Redlands, Calif., San Bernardino County Museum Association Quarterly, v. 42, no. 3, p. 69–74.

Miller, D.M., Miller, R.J., Nielson, J.E., Wilshire, H.G., Howard, K.A., and Stone, Paul, 1991, 

Preliminary geologic map of the East Mojave National Scenic Area, California: U.S. Geological 

Survey Open-File Report 91–435, scale 1:100,000, 7 p. 

Miller, D.M., Schmidt, K.M., Mahan, S.A., McGeehin, J.P., Owen, L.A., Barron, J.A., Lehmkuhl,

F., Lohrer, R., 2010, Holocene landscape response to seasonality of storms in the Mojave Desert: 

Quaternary International, v. 215, p. 45–61.

Miller, D.M., and Wooden, J.L., 1993, Geologic map of the New York Mountains area, California 

and Nevada: U.S. Geological Survey Open-File Report 93–198, 10 p., scale 1:50,000. 

Nielson, J.E., and Bedford, D.R., 1999, Geologic map of the Grotto Hills quadrangle, California 

and Nevada—A digital database: U.S. Geological Survey Open-File Report 99–35, scale 

1:24,000, at http://geopubs.wr.usgs.gov/open-file/of99-35/. 

Nielson, J.E., Turner, R.D., Bedford, D.R., 1999, Geologic map of the Hart Peak quadrangle, 

California and Nevada—A digital database: U.S. Geological Survey Open-File Report 99–34, 

scale 1:24,000, at http://geopubs.wr.usgs.gov/open-file/of99-34/. 

Phillips, F.M., 2003, Cosmogenic 36Cl ages of Quaternary basalt flows in the Mojave Desert, 

California, USA: Geomorphology, v. 53, p. 199–208. 

Skirvin, T.M., and Wells, S.G., 1990, Late Cenozoic structure, geometry, and landscape evolution 

of the Old Dad Mountain area, California: Redlands, Calif., San Bernardino County Museum 

Special Publication, p. 73–88.

Wells, S.G., Dohrenwend, J.C., McFadden, L.D., Turrin, B.D., and Mahrer, K., 1985, Late 

Cenozoic landscape evolution on lava flow surfaces of the Cima volcanic field, Mojave Desert, 

California: Geological Society of America Bulletin, v. 96, p. 1518–1529.

Wells, S.G., McFadden, L.D., Poths, J., and Olinger, C.T., 1995, Cosmogenic 3He surfaceexposure dating of stone pavements—Implications for landscape evolution in deserts: Geology, 

v. 23, p. 613–616.

Wilshire, H.G., 2002a, Digital version of "Open-File Report 92–181—Geologic map of the Indian 

Spring quadrangle, San Bernardino County, California": U.S. Geological Survey Open-File 

Report 02–272, scale 1:24,000, at http://geopubs.wr.usgs.gov/open-file/of02-272/. 

Wilshire, H.G., 2002b, Digital version of "Open-File Report 92–181—Geologic map of the Granite 

Spring quadrangle, San Bernardino County, California": U.S. Geological Survey Open-File 

Report 02–273, scale 1:24,000, at http://geopubs.wr.usgs.gov/open-file/of02-273/. 

Wilshire, H.G., 2002c, Digital version of "Open-File Report 92–181—Geologic map of the Cow 

Cove quadrangle, San Bernardino County, California": U.S. Geological Survey Open-File Report 

02–274, scale 1:24,000, at http://geopubs.wr.usgs.gov/open-file/of02-274/. 

Wilshire, H.G., 2002d, Digital version of "Open-File Report 92–181—Geologic map of the Marl 

Mountains quadrangle, San Bernardino County, California": U.S. Geological Survey Open-File 

Report 02–271, scale 1:24,000, http://geopubs.wr.usgs.gov/open-file/of02-271/. 

Yount, J.C., Schermer, E.R., Felger, T.J., Miller, D.M., and Stephens, K.A., 1994, Preliminary 

geologic map of Fort Irwin Basin, north-central Mojave Desert, California: U.S. Geological 

Survey Open-File Report 94–173, 27 p., scale 1:24,000.