Extensional 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, 1989 PDF
Preview Extensional 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, 1989
Extensional 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
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