Table Of ContentExtensional Tectonics in the
Basin and Range Province Between
the Southern Sierra Nevada
and the Colorado Plateau
The Basin and Range Province of Southern Nevada
and Southeastern California
June 30-July 7, t 989
Field Trip Guidebook T t 38
Leaders:
Brian ~ Wernicke }. Kent Snow Gary}. Axen B. Clark Burchfiel
Kip V Hodges }. Douglas Walker Peter L. Guth
American Geophysical Union, Washington, D.C.
Copyright 1989 American Geophysical Union
2000 Florida Ave., N.W., Washington, D.C. 20009
ISBN: 0-87590-606-0
Printed in the United States of America
COVER Precambrian crystalline basement rocks of the Copper Canyon
turtleback exposed below highly extended Tertiary strata, Black
Mountains, Death Valley, California (Stop 5-1).
IGC FIELD TRIP T138:
EXTENSIONAL TECTONICS IN THE BASIN AND RANGE PROVINCE
BETWEEN THE SOUTHERN SIERRA NEVADA AND THE COLORADO PLATEAU
TABLE OF CONTENTS
INTRODUCTION 1
GEOLOGIC OVERVIEW 1
DAY 1: CRATON AND FRONTAL THRUST BELT NEAR LAS VEGAS 12
DAY 2: SUPERIMPOSED THRUST AND NORMAL FAULTING, COLORADO PLATEAU TO
EASTERN MORMON MOUNTAINS 20
DAY 3: WESTERN PART OF THE MORMON MOUNTAINS, MEADOW VALLEY WASH, AND
MUDDY MOUNTAINS 29
DAY 4: TERTIARY EXTENSION IN THE SHEEP RANGE AREA, NORTHWESTERN
CLARK COUNTY, NEVADA , 33
DAY 5: SPRING MOUNTAINS BREAKAWAY ZONE, AMARGOSA CHAOS, AND THE
DEATH VALLEY PULL-APART BASIN 39
DAY 6: MIDDLE MIOCENE(?) THROUGH QUATERNARY EXTENSION, NORTHERN
PANAMINT MOUNTAINS AREA, CALIFORNIA 45
DAY 7: NEOGENE DEXTRAL TRANSLATION OF THE COTTONWOOD MOUNTAINS AREA,
CALIFORNIA 56
DAY 8: NEOGENE EXTENSION BETWEEN THE GRAPEVINE MOUNTAINS AND SPRING
MOUNTAINS, CALIFORNIA AND NEVADA 67
ACKNOWLEDGEMENTS 75
REFERENCES ' 75
v
Leaders:
G. J. Axen, J. K. Snow, and B. P. Wernicke
Department of Earth and Planetary Sciences
Harvard University
Cambridge, MA 02138
B. C. Burchfiel and K. V. Hodges
Department of Earth Atmospheric, and Planetary Sciences
i
Massachusetts Institute of Technology
Cambridge, MA 02139
P. L. Guth
Department of Oceanography
U.S. Naval Academy
Annapolis, MD 21402-5026
J. D. Walker
Department of Geology
University of Kansas
Lawrence, KS 66045
vii
IGC FIELD TRIP T138
EXTENSIONAL TECTONICS IN THE BASIN AND RANGE PROVINCE
BETWEEN THE SOUTHERN SIERRA NEVADA AND THE
COLORADO PLATEAU
Brian P. Wernicke1, J. Kent Snow1, Gary J. Axen1, B. Clark Burchfiel2, Kip V. Hodges2, J. Douglas
Walker3, Peter L. Guth4
INTRODUCTION 2 and 3, we will transect the same structural level
in the thrust belt farther north, where severe
The purpose of this field trip is to examine the extension has overprinted the frontal thrusts. On
tectonic history of one of the planet's best-exposed Day 4 we will venture deeper into the core of the
intracontinental rifts, the Basin and Range orogen and examine the first major thrust plate
province. The trip is run as a transect at the above the frontal thrust zone, the Gass Peak
latitude of Las Vegas, Nevada, where the province Wheeler Pass thrust plate, and major extensional
is relatively narrow (about 360 km measured east structures developed within its upper plate. On
west). While the emphasis of the trip is on Days 5 and 6 we will transect the same structural
Cenozoic extensional tectonics, much of the level in the Mesozoic thrust belt as on Day 4, but
discussion will center on pre-Cenozoic geology, as farther south where extension is still greater and
the pre-€xtensional geological framework must be localized closer to the thrust plane. On Days 7 and
thoroughly understood in.order to piece together 8, we will observe the structurally highest levels of
the extensional history. Because the amount of the thrust belt at these latitudes, and examine the
crustal pull-apart is large (about 250 km oriented relationships between strike-slip faulting, normal
west-northwest) fragments of crust preserved in faulting, and rotation of crustal fragments. The
widely separated basin ranges are similar to one guidebook is organized into a geologic overview of
another, and in a number of cases pre-extension the entire transect, followed by separately authored
geologic features within these fragments provide the articles for each day of the trip. Each article
basis for accurate tectonic reconstructions. contains a geologic overview ofthe day followed by
The Basin and Range province, and the a roadlog, which contains specific information
Cenozoic extensional tectonism it represents, is relevant to individual stops.
spatially coincident with the Paleozoic and
Mesozoic thrust belts of the Cordilleran orogenic
belt. The basic architecture of the Cordilleran GEOLOGIC OVERVIEW
orogen near Las Vegas consists of east-vergent folds
and thrusts of Mesozoic age overprinted by down The Basin and Range province near the
to-the-west normal faults of mid-Miocene to Recent latitude of Las Vegas has an ideal regional tectonic
age. The strategy of the field trip will be to setting for a province-wide reconstruction of
progress from the craton to progressively higher Cenozoic extension (Figure 0-2). The pre
structural levels of the Mesozoic thrust belt, where extension geology is more straightlorward than at
it is ultimately intruded out by the Mesozoic Sierra other latitudes, because the regionally conformable
Nevada batholith (Figures 0-1 and 0-2). Cordilleran miogeocline is exposed across the entire
On Day 1 we will examine the craton and width of the province (Figures 0-2 and 0-3). The
frontal thrusts near Las Vegas, where the Cenozoic miogeocline is disrupted by east-vergent Mesozoic
extensional overprint has not been severe. On Days thrust faults that make local reconstructions more
complicate~ than they might be in their absence.
However, the thrusts are distinctive enough and the
extensional separation of crustal blocks great
lDepartment of Earth and Planetary Sciences, enough that they provide the markers necessary to
Harvard University, Cambridge, Massachusetts tightly constrain large-scale reconstructions. The
2Department of Earth, Atmospheric, and thrusts are thus more an aid than a complication,
Planetary Sciences, Massachusetts Institute of for discrete markers within the miogeoclinal section
Technology, Cambridge, Massachusetts are few, and in most cases the determination of
3Department of·Geology, University of Kansas, fault offsets based purely on isopachs and facies
Lawrence, Kansas trends is limited by the uncertainty in their precise
4Department of Oceanography, U.S. Naval location, and by the assumption of their initial
Academy, Annapolis, Maryland geometry [e.g. Stewart, 1983; Prave and Wright,
T138:
IGC FIELD TRIP T138
EXTENSIONAL TECTONICS IN THE BASIN AND RANGE PROVINCE
BETWEEN THE SOUTHERN SIERRA NEVADA AND THE
COLORADO PLATEAU
Brian P. Wernicke1, J. Kent Snow1, Gary J. Axen1, B. Clark Burchfiel2, Kip V. Hodges2, J. Douglas
Walker3, Peter L. Guth4
INTRODUCTION 2 and 3, we will transect the same structural level
in the thrust belt farther north, where severe
The purpose of this field trip is to examine the extension has overprinted the frontal thrusts. On
tectonic history of one of the planet's best-exposed Day 4 we will venture deeper into the core of the
intracontinental rifts, the Basin and Range orogen and examine the first major thrust plate
province. The trip is run as a transect at the above the frontal thrust zone, the Gass Peak
latitude of Las Vegas, Nevada, where the province Wheeler Pass thrust plate, and major extensional
is relatively narrow (about 360 km measured east structures developed within its upper plate. On
west). While the emphasis of the trip is on Days 5 and 6 we will transect the same structural
Cenozoic extensional tectonics, much of the level in the Mesozoic thrust belt as on Day 4, but
discussion will center on pre-Cenozoic geology, as farther south where extension is still greater and
the pre-€xtensional geological framework must be localized closer to the thrust plane. On Days 7 and
thoroughly understood in.order to piece together 8, we will observe the structurally highest levels of
the extensional history. Because the amount of the thrust belt at these latitudes, and examine the
crustal pull-apart is large (about 250 km oriented relationships between strike-slip faulting, normal
west-northwest) fragments of crust preserved in faulting, and rotation of crustal fragments. The
widely separated basin ranges are similar to one guidebook is organized into a geologic overview of
another, and in a number of cases pre-extension the entire transect, followed by separately authored
geologic features within these fragments provide the articles for each day of the trip. Each article
basis for accurate tectonic reconstructions. contains a geologic overview ofthe day followed by
The Basin and Range province, and the a roadlog, which contains specific information
Cenozoic extensional tectonism it represents, is relevant to individual stops.
spatially coincident with the Paleozoic and
Mesozoic thrust belts of the Cordilleran orogenic
belt. The basic architecture of the Cordilleran GEOLOGIC OVERVIEW
orogen near Las Vegas consists of east-vergent folds
and thrusts of Mesozoic age overprinted by down The Basin and Range province near the
to-the-west normal faults of mid-Miocene to Recent latitude of Las Vegas has an ideal regional tectonic
age. The strategy of the field trip will be to setting for a province-wide reconstruction of
progress from the craton to progressively higher Cenozoic extension (Figure 0-2). The pre
structural levels of the Mesozoic thrust belt, where extension geology is more straightlorward than at
it is ultimately intruded out by the Mesozoic Sierra other latitudes, because the regionally conformable
Nevada batholith (Figures 0-1 and 0-2). Cordilleran miogeocline is exposed across the entire
On Day 1 we will examine the craton and width of the province (Figures 0-2 and 0-3). The
frontal thrusts near Las Vegas, where the Cenozoic miogeocline is disrupted by east-vergent Mesozoic
extensional overprint has not been severe. On Days thrust faults that make local reconstructions more
complicate~ than they might be in their absence.
However, the thrusts are distinctive enough and the
extensional separation of crustal blocks great
lDepartment of Earth and Planetary Sciences, enough that they provide the markers necessary to
Harvard University, Cambridge, Massachusetts tightly constrain large-scale reconstructions. The
2Department of Earth, Atmospheric, and thrusts are thus more an aid than a complication,
Planetary Sciences, Massachusetts Institute of for discrete markers within the miogeoclinal section
Technology, Cambridge, Massachusetts are few, and in most cases the determination of
3Department of·Geology, University of Kansas, fault offsets based purely on isopachs and facies
Lawrence, Kansas trends is limited by the uncertainty in their precise
4Department of Oceanography, U.S. Naval location, and by the assumption of their initial
Academy, Annapolis, Maryland geometry [e.g. Stewart, 1983; Prave and Wright,
T138:
@ STOP WITH HIK·E-BRING WATER
Fig. 0-1: Map of the Basin and Ran~e province near the latitude of Las Vegas showing field trip stops,
geographic names, major highways tnumbers in circles are keyed to Defense Mapping Agency 10x20
sheets, scale 1:250,000), and locations of other figures. Mountain ranges are shaded, valleys are
unpatterned.
1986a,b]. The great thickness of the thrust-faulted in the region because it lies at low elevation, and in
miogeocline gives good depth control on the rain shadow of the Sierra Nevada and more
cross-sectional reconstructions, which is locally in southerly ranges. In addition, much of the geology
excess of15 km (Figure 0-3). Exposure is excellent is developed within carbonate rocks, which crop out
T138: 2
• ..STOP AT ROADSIDE. II LODGING
well in desert regions. width (Figure 0-2). The median high is centered
The regionally averaged topographic pattern of on the Spring Mountains, Sheep Range and Las
the Basin and Range at the latitude ofLas Vegas is Vegas Range, while the lows include the Colorado
one ofhigh flanks, comprising the Sierra Nevada on River trough/Lake Mead area on the east and the
the west and the Colorado Plateau on the east, and Death Valley region on the west (Figure 0-1). As
two broad, low-lying areas on either side of a discussed below, the two low-lying areas are highly
median high [Eaton et al., 1978]. This pattern extended, while the median high is less extended.
resembles that of the northern Basin and Range,
but at smaller scale because the province is halfthe
T138: 3
Lithologically, the miogeocline is divisible into
two main parts, including a Middle Cambrian and
older clastic wedge and a Middle Cambrian and
younger carbonate succession (Figure 0-3). The
clastic wedge thickens from less than 100 m on the
craton to the east, where basal strata are Lower
Cambrian, to more than 5000 m in western areas
where most of the sequence lies below basal
Cambrian beds. The Paleozoic sequence is entirely
marine, except for some Permian strata that are
partly nonmarine [Wright et al., 1981; Stone and
Stevens, 1987]. Westward thickening of the
carbonate succession occurs in part by thickening of
individual units and in part by the pinching in of
Ordovician, Silurian and Devonian strata beneath a
major sub-Upper Devonian disconformity (Figure
0-3). On the craton, Upper Devonian strata lie
disconformably on Upper Cambrian. To the west,
they lie on progressively younger strata until a fully
developed Ordovician, Silurian, and Devonian
section is present. The youngest marine strata in
the region are Triassic, and are overlain in eastern
"areas by nonmarine clastics locally·as young as
Fig. 0-2: Regional setting of the field trip area Cretaceous, and in western areas by Lower
with respect to major components of the Mesozoic volcanics [e.g. Wright et al., 1981]. In
Cordilleran orogen [from Wernicke et al., 1988]. sections in the transition zone between craton and
miogeocline, the highest Paleozoic strata present on
Basement, Proterozoic Basin, and Miogeoclinal the craton, including the Kaibab and Toroweap
Wedge Formations, pinch out westward beneath the basal
Mesozoic unconformity (Figure 0-3) [e.g. Tschanz
Precambrian Y (mostly ca. 1.7-1.4 Ga) and Pampeyan, 1970; Burchfiel et al., 1974]. In
crystalline basement in the region lies westernmost sections of the miogeocline, complex
nonconformably beneath unmetamorphosed unconformities and facies changes in Carboniferous
sediments of Precambrian Y (1), Precambrian Z or and Permian strata indicate Permian tectonism
Cambrian age (Figure 0-3). Precambrian Y (1) [Stone and Stevens, 1984; 1988a].
and Z strata of the Pahrump Group (Figure 0-3) The primary lateral facies changes within the
are locally present in ranges west and~southwest of miogeocline include a transition from quartzite and
the Spring Mountains between basement and siltstone in eastern exposures ofthe Precambrian Z
regionally persistent Precambrian Z to Cambrian Cambrian clastic wedge to predominantly shale and
strata that form the base of the Cordilleran carbonate in the west [Stewart, 1970], and a
miogeocline in the region [Stewart, 1970, 1972]. transition from mostly shallow marine limestone in
While the lower portion ofthe Pahrump is probably Carboniferous and Permian strata in eastern areas
Precambrian Y in age, the upper part appears to be to deep-marine shale, sandstone and limestone in
in gradational contact with the Cordilleran the west [Dunne et al., 1981; Stone and Stevens,
miogeocline, and thus is probably Precambrian Zin 1988b] (Figure 0-3). The increase in fine clastics
age [Miller, 1987]. The west-thickening and carbonate in the clastic wedge indicates a
Precambrian Z and Paleozoic miogeocline" (Figures transition from shelf to slope-and-rise facies
0-2 and 0-3) is overlain disconformably or with [Stewart, 1972], but early Paleozoic slope-and-rise
mild angular' unconformity bX locally thick deposits are not present east of the Sierran
accumulations ofMesozoic strata (Figure 0-3). batholith at this latitude (Figure 0-2). The
The most significant stratigraphic feature westward increase in clastics in Carboniferous
beneath the miogeoclinal strata is the northward strata probably represents the distal effects of the
pinchout of the ·Pahrump Group in the southern mid-Paleozoic Antler orogeny [e.g. Dunne et al.,
Death Valley region [Wright et al., 1974, 1981]. 1981], which farther north in central Nevada is
South of the pinchout, as much as 3000 m of expressed by the eastward thrusting of early
Pahrump strata are present below the basal units of Paleozoic slope-and-rise facies strata onto the shelf
the miogeocline in the southern Black Mountains, facies rocks, forming a broad, asymmetrical foreland
Kingston Range and Panamint Range (Figure 0-1). basin [e.g. Poole and Sandberg, 1977]. Structural
Over a distance of less than 10 km, the basal effects of the Antler and Permo-Triassic Sonoma
miogeoclinal unconformity cuts downsection orogenic events may be present in western portions
through the Pahrump Group and onto crystalline of the region [e.g. Nelson, 1981] including possible
rocks. truncation ofthe continental margin in Permian
T138: 4
