Late Cenozoic Fault Patterns and Stress Fields in the Great Basin and Westward Displacement of the Sierra Nevada Block

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Late Cenozoic fault patterns and stress fields in the Great Basin and westward displacement of the Sierra Nevada block

Lauren Wright ABSTRACT Department of Geosciences The patterns of late Cenozoic faulting in the Great Basin Pennsylvania State University apparently delimit two deformational fields, each extensional University Park, Pennsylvania 16802 but contrasting in magnitude and style of extension. The field of smaller magnitude, which shows about 10 percent extension, occupies the northern and most of the central part of the Great Basin. It is characterized by steeply dipping normal faults and fault zone and ruptures that delineate the group of crudely gently tilted blocks, with a preferred north to northeast trend. aligned valleys of the well-known Walker Lane (Fig. 1), follow the suggestion of Becker (1934), Carey (1958), and Wise (1963) and Evidence of greater extension occurs in the other defor- favor a "megashear" model in which the right-lateral faults of the mational field, which lies between Walker Lane and the Sierra Great Basin, together with the San Andreas fault zone, compose Nevada and extends across the narrow southern end of the a major part of a large-scale right-lateral shear system involving Great Basin. This field contains most of the complementary much or all of the North American Cordillera. In the context of strike-slip faults (northwest-striking right-lateral and northeast- plate tectonics these faults are commonly represented as involving striking left-lateral faults), long recognized as major components a zone of transform faulting between the Pacific and North of the structural framework. It also contains abundant normal American plates (Atwater, 1970). In the megashear model, the faults, most of which strike north to northeast. In certain areas, normal faults theoretically are second-order features analogous to extension of 50 percent or more is indicated in the association tension-gash fractures. They also are commonly cited as products of an "oblique extension" that combines components of westerly of strike-slip and normal faults and in the palinspastic restora- extension and right-lateral shear (Hamilton and Myers, 1966). tion of fault blocks that have been steeply tilted along gently dipping normal faults. These contrasts in structural pattern and The most enduring interpretation is that the normal faults are first-order features that record a generally westward, non- apparent percentage of extension may be related to westward rotational crustal spreading. This "simple extension" model is movement of the Sierra Nevada block and southward narrow- rooted in the work of G. K. Gilbert and W. M. Davis, whose ob- ing of the Great Basin. servations in the early 1900s (before the strike-slip faults were The faults along which strike-slip displacement occurred recognized) led to the conclusion that the typical basin-range in late Cenozoic time appear to have functioned as conjugate block is bounded by normal faults. Recent proponents of "simple shears, the shears and associated normal faults being first-order extension" (that is, Gilluly, 1970; Scholz and others, 1971; Davis extensional features. The fault pattern also invites a simplistic and Burchfiel, 1973) have stated or implied that the strike-slip interpretation that is based on the orientation of three mutually faults within the Great Basin are relatively unimportant. perpendicular directions of stress. The major normal faults, Still other workers have argued that the complementary nature of the strike-slip faults holds the key to late Cenozoic which strike north-northeast in most parts of the Great Basin, deformation in the Great Basin and have interpreted these faults suggest a pervasive horizontal minimum compressive (maximum as conjugate shears produced in a nonrotational stress field tensional) stress that is oriented west-northwest. Maximum (Allison, 1949; Donath, 1962; Shawe, 1965; Hill and Troxel, 1966). compressive stress would be oriented perpendicularly where the In this model, shearing is generally ascribed to compression along horst and graben structure predominates and horizontally to the a north- to northeast-trending axis, and the normal faults are east-northeast where the strike-slip faults are abundant. viewed as release features striking parallel with the compressional axis. Objections have been raised to each of the three interpreta- tions: principally, (1) the "simple extension" model inadequately accommodates the complementary strike-slip faults (Hill and INTRODUCTION Troxel, 1966); (2) the "megashear" model lacks evidence of right- The patterns of late Cenozoic (post-Oligocene) faulting, which lateral displacement along the proposed northeast margin of the characterize the Great Basin (Fig. 1) of the Basin and Range prov- shear system (Gilluly, 1970) and inadequately accounts for the left- ince, have become increasingly well documented in recent years. lateral faults (implied by Davis and Birchfiel, 1973); and (3) the However, geologists continue to puzzle, as they have done for a compression, apparently implicit in the "conjugate shear" model, century and more, over the relationship that these patterns bear should have produced thrusts oriented at low angles to the free to large-scale crustal motions. Investigators apparently agree that surface of the Earth rather than the strike-slip faults at high the crust of the Great Basin is spreading relatively west to west- angles to the surface (Gilluly, 1963). northwest, causing movement on normal faults, which, although The following discussion explores an alternative interpreta- variously oriented, strike predominantly north-northeast. Opinions tion, shown schematically in Figure 2, that the fault pattern differ, however, concerning the role of two sets of strike-slip faults records a deformational environment featured by markedly con- also active in late Cenozoic time, one right lateral and northwest trasting degrees of extension. This interpretation is supported by striking and the other left lateral and northeast striking. features that, although previously noted, seem to have been under- Most recent workers, impressed with evidence of right-lateral emphasized. These include (1) the restriction of most of the strike- displacement along the northern Death Valley-Furnace Creek slip faults to a generally symmetrical region that bounds the Sierra

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Nevada on the east and spans the southern part of the Great Basin, where mountains of the Basin and Range province gen- Basin (Fig. 1), (2) the southward narrowing of the Great Basin erally trend north-northeast; this area is identified as deforma- between the Sierra Nevada block and the relatively rigid crust of tional field I in Figure 2. the Colorado Plateau and Middle Rockies, (3) indications of The region that extends westward from the Walker Lane to greater extensional strain in the southern Great Basin than in the the Sierra Nevada, however, has also been recognized as topo- much wider northern part, and (4) evidence that the Sierra Nevada graphically and structurally distinct from most of the rest of the block has moved considerably farther west, with reference to the Great Basin (Fig. 1). In that region a large proportion of the Colorado Plateau, than the areas north and south of the block. ranges trend northwestward, primarily as a result of the northwest- striking right-slip faults. Associated with these faults are abun- CONTRASTING PATTERNS OF LATE CENOZOIC dant, generally north- to northeast-striking normal faults and less DEFORMATION numerous east-northeast-striking left-lateral faults. That the Most of the Great Basin has long been recognized as a sys- region of prominent strike-slip faults extends eastward from the tem of horsts and grabens, marked by gently tilted fault blocks southern end of Walker Lane to the edge of the Colorado Plateau and steeply dipping normal faults. Such features are especially has been recently documented, mainly by Tschanz and Pampeyan characteristic of the central and northern parts of the Great (1970) in Lincoln County, Nevada, and by Anderson (1973) in the

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Lake Mead area. There the strike-slip faults are dominantly left patible with the interpretation that the strike-slip faults are shears lateral and show cumulative displacement measurable in tens of in a primarily extensional environment. Relatively intense spread- kilometres. On the basis mainly of the concentration of comple- ing, occurring between the ends of en echelon strike-slip faults, mentary strike-slip faults, the western and southern parts of the may have favored the localization of volcanic centers (Wright and Great Basin are identified separately in Figure 2 (field II). Troxel, 1968, 1971; Carr, 1974). The deformation style of field II is difficult to describe In spite of a growing body of data concerning the actual dis- simply, because many of the late Cenozoic structural features have placements on the strike-slip faults, it is insufficient for an ade- been incompletely studied or have proved difficult to interpret. quate overview. The most thoroughly investigated faults are the Very common within the field, however, are steeply tilted fault northwest-trending right-lateral faults that occupy Las Vegas blocks and low-angle normal faults, which are apparently indica- Valley, southern Death Valley, and the northern Death Valley- tive of severe extension. The fault blocks bounded by the low-angle Furnace Creek Wash depression. As much as 50 km of displace- normal faults commonly tilt at angles greater than 45° (Fig. 3); ment, all in late Cenozoic time, has been postulated for the Las these are characteristic of the complex structural feature termed Vegas shear zone (Longwell, 1971), but this displacement, if real, the Amargosa chaos (Noble, 1941; Wright and Troxel, 1973). apparently dies out rapidly northwestward. As much as 150 km of Also noteworthy are observations that the boundary between displacement has been ascribed to right-lateral faults and hypo- the two fields coincides with a westerly extension of the inter- thetical oroclinal folds in the Death Valley region (Stewart and mountain seismic belt (Lahr and Stevenson, cited by Thompson Poole, 1974), an interpretation based on apparent anomalies in and Burke, 1974; Smith and Sbar, 1974) and that the southern thickness of Cambrian and uppermost Precambrian formations. Great Basin, including much of field II, is on the average about However, pointing against displacement of this magnitude is much 1 km lower than the central part of the Great Basin (data from evidence from lower Precambrian formations of throughgoing iso- Suppe and others, 1975). The latter may indicate crustal thinning pachous lines, facies trend lines, and paleogeologic contacts that from field I to field II, perhaps an effect of greater extension. trend west-northwest through the belt of proposed dislocation, with very little indication of offset or bending (Wright and Troxel, COMPLEMENTARY STRIKE-SLIP FAULTS 1967; Roberts, 1974; Williams and others, 1974). McKee (1968) The right-lateral, northwest-trending faults east of the Sierra has presented evidence that Jurassic plutons have been offset as Nevada have been commonly ascribed to an eastward encroachment much as 48 km right laterally along the northern Death Valley- of faults of the San Andreas type. This assumption has been ques- Furnace Creek fault zone, but he implied that only a small part tioned by Gilluly (1970), who has observed that the physical char- of this displacement has occurred since mid-Tertiary time. acteristics of strike-slip faults of the Basin and Range province Displacements on the left-lateral faults of the eastern part of differ from those of the San Andreas system of the Pacific Coast field II apparently are comparable in magnitude with those of the provinces. Notably, the traces of the former tend to be more ir- right-lateral faults of the western part. Tschanz and Pampeyan regular and less continuous than those of the San Andreas system (1970) estimated as much as 14 km of left-lateral displacement on and to terminate abruptly, commonly within mountain ranges. northeast-trending faults (Pahranagat shear system) in southern Many, perhaps most, of the terminations and irregularities in Lincoln County, Nevada, and referred to them as tear faults. Evi- both the right-lateral and left-lateral faults occur where they are dence of cumulative left-lateral displacement of as much as 65 km joined by or pass into normal faults or where they are joined by was observed by Anderson (1973) on a zone of northeast-trending strike-slip faults of the other set. Such terminations, as well as the faults in the Lake Mead area. Still other faults, left-lateral and close association of strike-slip faults with normal faults, are com- trending northeast, occur in the western Nevada Test Site region

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BlACK MOUNTAINS

Figure 3. Generalized cross section, as shown in Figure 1, through region of central Death Valley, showing geometric evidence for

25 km large-magnitude crustal extension and inter- I 1 EH pretation that much of extension in Pre- Earlier Precambn- Later Precambrian Latest Precambrian MesozotcC) intru- Cenozoic intrusive Cenozoic sediment- Quaternary cambrian crystalline terrane has been accom- an crystalline com- Pahrump Group: and Cambrian sed- sive rocks and extrusive ary units alluvium modated by intrusion of bodies of igneous plex sedimentary units imentary units roCKS and diabase rock. Modified from Wright and Troxel (1973).

and the vicinity of the Timber Mountain caldera and have been features, as suggested by Thompson (1971). The latter origin is documented by members of the U.S. Geological Survey (for exam- clearly applicable to some of the smaller blocks but is much more ple, Poole and others, 1965). The distribution of these faults and difficult to apply to entire belts of mountain ranges such as the their relationship to those of the right-lateral set have been re- one in the cross section of Figure 3. Severe extension in the lower cently discussed by Carr (1974), who suggested that eruptive cen- part of the crust may have been accommodated by the emplace- ters and calderas along Walker Lane may be associated with ment of bodies of igneous rock rather than normal faulting northeast-trending zones of weakness between terminations in (Anderson, 1971a; Wright and Troxel, 1973). en echelon shear zones. Published analyses of fault geometry by Gilluly (1970), Stewart (1971), and Thompson and Burke (1973), mainly from NORMAL FAULTS observations in the area of field I, have yielded estimates of ex- Most of the recent accounts of basin-range faulting (for tension of 4 to 16 percent, 5 to 10 percent, and 10 percent, respec- example, Gilluly, 1963; Stewart, 1971; Thompson, 1971) imply tively. The 10 percent figure implies an absolute extension of that the steeply dipping normal faults, so well documented in the roughly 80 km at lat 40°N, where the Great Basin is about 900 northern and central parts of the Great Basin, characterize the km wide. If the southern part of the Great Basin, which is now other parts as well. Indeed, many of the major normal faults of about 350 km wide, should have been extended by 30 percent, it field II do strike northeast, and many of these may well extend also would have increased in width by approximately 80 km. deep into the crust at steep angles. However, the normal faults that dip at angles of less than 45° and are associated with steeply WESTWARD DISPLACEMENT OF THE SIERRA NEVADA tilted blocks occur in large areas within field II. These faults BLOCK characterize the Desert Range north of Las Vegas Valley and the Eaton (1932) apparently was the first to suggest that the South Virgin Mountains east of Lake Mead (Longwell, 1945) and Sierra Nevada block has moved preferentially westward, produc- have been observed at various other localities in southern Nevada ing extensional features in its wake and compressional features and northwestern Arizona, including the Eldorado Range about before it. He believed the westward movement to be greatest along 20 km south of Boulder City (Anderson, 1971a) and the Black the Garlock fault and to diminish northward. Evidence that the Mountains north of Lake Mead (Anderson, 1973). They also Sierra Nevada block has moved 60 to 80 km, in a left-lateral sense, characterize a large but incompletely defined area that spans along the Garlock fault (Smith, 1962) has been subsequently southern and central Death Valley (Hunt and Mabey, 1966; widely cited and accepted. The displacement apparently increases Wright and Troxel, 1973). Still other normal faults that flatten westward, from a zero point somewhere in the southern Death at shallow depths have been documented in the vicinity of Yering- Valley region to the Sierra Nevada (Troxel and others, 1972; ton, Nevada (Proffett, 1971). Davis and Burchfiel, 1973). Where mapped in detail, such as in the Eldorado Range In later versions of the concept of a west-moving Sierra Nevada (Anderson, 1971a) and in the southern Death Valley area (Wright block, Hamilton and Myers (1966) and Cook (1969) apparently have and Troxel, 1973), a palinspastic restoration of the strongly tilted represented the block as bounded on the north by a zone of right- blocks indicates that the faulted rock units have been extended as lateral dislocation that has caused the northern Sierra Nevada to much as 30 to 50 percent and perhaps more. Large extension is move westward away from the terrane of Mesozoic plutons and pre- also suggested by evidence that tens of kilometres of displacement batholithic metamorphic rocks of northwestern Nevada. Various have been transferred to normal faults from the Garlock fault zone features suggest that displacement there, as along the Garlock (Troxel and others, 1972; Davis and Burchfiel, 1973), the northern fault, is measurable in tens of kilometres. Especially obvious on Death Valley-Furnace Creek fault zone (Wright and Troxel, 1970), recently published geologic maps of California (Jennings, 1973) and strike-slip faults in the Lake Mead area (Anderson, 1973). and Nevada (Stewart and Carlson, 1974) is the arcuate bend in The origin of the low-angle faults of the Great Basin remains the belt of right-lateral faults of Walker Lane. The faults change undetermined (see especially Longwell, 1945; Stewart, 1971; in strike from about N30°W in the area southeast of Walker Lake Anderson, 1971a, 1971b; Thompson, 1971) and requires further to about N50°W west of Pyramid Lake (Fig. 1) and to an even study. Recent conjecture concerns the question of whether the more westerly orientation if the Honey Lake and Litchfield crust beneath the zone of low-angle faulting also has been ex- faults in California are assigned to the Walker Lake group. tended or whether the tilted blocks are superficial, gravity-impelled In an area west of Pyramid Lake, Bonham (1969) has ob-

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Downloaded from https://pubs.geoscienceworld.org/gsa/geology/article-pdf/4/8/489/3541379/i0091-7613-4-8-489.pdf?casa_token=BpatOfzDi0QAAAAA:I-cD_Xv5bIrFHXC8qZV_KLgSLVlog3hbNv7HXUpeHE94L-igR4lRplro2SnZbsuFoLXCXpSl by California Geological Survey, 19774 on 20 July 2019 served evidence (suggestive only) of a 30-km right-lateral offset faults of the Great Basin and to trends in the Precambrian base- of the northern limit of exposure of a unit of Tertiary rhyolite. He ment. Moreover, the preferred north-northeast trend of field I in also noted unlike facies of Mesozoic rocks on opposite sides of the the Basin and Range province approximately parallels the trend belt of right-lateral faults in the Pyramid Lake area. If the belt of the continental margin in early Paleozoic time and the mid- extends still farther westward, it would approximately coincide Paleozoic Antler orogenic belt. with various seismic and gravity anomalies (Eaton, 1963; Woollard Nevertheless, when plotted at the scale of Figures 1 and 2, and Joesting, 1964) that mark the break between the predomi- the faults of the Great Basin display a systematic arrangement nantly pre-Cenozoic sialic crust of the Sierra Nevada and the that may reflect the orientation of the late Cenozoic stresses and Cenozoic volcanic terrane of the Modoc Plateau. Projected still a stress field of relatively uniform orientation through most of the farther, it could include a fault, buried beneath Quaternary and Great Basin. The northwest-trending faults commonly have right- Pliocene deposits, that trends west-southwest across the northern lateral displacement and a preferred strike visually estimated end of the Great Valley. Pared gravity highs and magnetic anom- as north-northwest. Faults on which left-lateral displacement has alies, detected both north and south of the fault, suggest a been detected ordinarily strike east-northeast. The major normal possible 30 km of right-lateral displacement (Griscom, 1973). faults of both fields I and II display a preferred strike of north- The concept of preferential westward movement of the Sierra northeast, thus approximately bisecting the angle between the Nevada block is supported by the observations of Taubeneck (1971) preferred strikes of the two sets of strike-slip faults. This geometry along the right-lateral bend in the belt of plutons, which lies be- and consistency of displacement invite an interpretation based on tween the Sierra Nevada and Idaho batholiths. He has estimated Anderson's (1951) classification of faults according to the orienta- that approximately 50 km of offset has been accomplished in tion of three mutually perpendicular directions of stress (Fig. 2). Cenozoic time by right-lateral faulting, dike intrusion, and normal If this approach is valid, both the horst and graben structure of faulting in a broad belt that includes the right-lateral faults of field I and the conjugate strike-slip faults of field II indicate a Walker Lane. horizontal minimum compressive (maximum tensional) stress More recently, Lawrence (1976) delineated four major west- oriented west-northwest-east-southeast at right angles to the pre- northwest-trending zones of right-lateral displacement in southern ferred strike of the normal faults. Maximum compressive (mini- and eastern Oregon, which are compatible with the concept of mum tensional) stress would be vertically oriented where the a westward-drifting Sierra Nevada block and which support normal faults are mostly steeply dipping (about 60° or more) and Taubeneck's conclusions that the belt of displacement there is outline the horst and graben structure. It would be horizontally much wider than the Garlock fault zone at the southern end of oriented where the strike-slip faults and low-angle faults are the the block. Three of the four zones (Mount McLoughlin, Eugene- dominating structural features. Denio, and Brothers) lie within the area of Figure 1. Probably The coexistence in field II of the strike-slip faults and normal related to them is a fifth feature, the Likely fault of northeastern faults suggests that locally o, and a, interchange and that the California (Fig. 1), along which Gay and Aune (1958) observed difference between intermediate and maximum principal stress evidence of major right-lateral dislocation. may be small. The orientation of minimum principal stress re- As described by Lawrence (1976), the slices between the four mains fixed at approximately west-northwest. zones in Oregon are broken by normal faults that record east- The indicated west-northwest-east-southeast orientation for west extension. He explained the geometry of right-lateral displace- the minimum principal stress is in accord with a detailed consid- ment by citing evidence of progressively smaller amounts of ex- eration by Carr (1974) of stress orientation in the vicinity of the tension from slice to slice, south to north, and has suggested that Nevada Test Site, including the Timber Mountain caldera. From much of the 50 km of the right-lateral displacement proposed by the orientation of structural features, seismic data, stress and Taubeneck can be accommodated along the Eugene-Denio zone. strain measurements, and drill-hole enlargement, Carr concluded He has further suggested that the four zones of right-lateral dis- that the Nevada Test Site is undergoing N50°W to S50°E exten- placement function as tear faults that contribute to a westward sion coincident with the direction of minimum principal stress. bulge in the continent at the site of the Great Basin. Implicit in the proposed model and subject to future testing is the assumption that the cumulative late Cenozoic strike-slip DIFFERENTIAL EXTENSION MODEL displacements in the Great Basin east of the Sierra Nevada are The tectonic model of Figure 2 explains the distribution of modest, not exceeding in magnitude the cumulative extension late Cenozoic normal and strike-slip faults in the Great Basin, recorded in the normal faults east of the Sierra Nevada block. produced by westerly crustal extension with different degrees of This assumption seems reasonable, especially in view of the evi- magnitude but devoid of an oblique component. The strike-slip dence of compensation of motion already cited and because much faults are interpreted as conjugate shears concentrated in areas of the displacement claimed for the northern Death Valley-Furnace of large-magnitude extension where the steeply tilted fault blocks Creek fault zone has been attributed to pre-Cenozoic time. One and low-angle normal faults are also abundant. Such areas, in must also assume that the lateral displacements at each end of contrast with the more northly parts of the Basin and Range the Sierra Nevada block decrease progressively westward. Support- province where less severe extension is evident, apparently is ing this assumption is (1) the apparently still credible observation, spatially related to the west-moving Sierra Nevada block and to first made by Eaton (1932), that the extensional features east of the southward narrowing of the Great Basin. the Sierra Nevada are largely compensated by compressional fea- To assume that the orientations of the basin-range faults in tures to the west and (2) the suggestion by Hill and Dibblee (1953) the Great Basin accurately reflect the stress directions contem- that the "big bend" in the San Andreas is an expression of left- poraneous with them contains well-recognized hazards. As Stewart lateral movement on the Garlock fault. Some of the right-lateral (1971) and others before him have pointed out, the patterns of movement along the north margin of the Sierra Nevada block normal faulting, if observed in detail, tend to be highly irregular may well have been transferred northward into the volcanic terrane and thus difficult to analyze. The fault orientations must have of the Modoc plateau, which may be a locale of late Cenozoic been guided, in part, by lithologic and structural inhomogeneities, spreading devoid of sialic crust (Hamilton and Myers, 1966). ranging from subhorizontal to vertical, that were acquired during Still incompletely resolved in the formulation of the differ- a long history of sedimentation, deformation, and igneous activity. ential extension model are the problems of explaining (1) the Planes of weakness, established in Precambrian time, have clearly superposition of strike-slip and normal faults, (2) the significance influenced the orientation of some faults of late Cenozoic move- and origin of the low-angle normal faults, (3) the relation of the ment described by Wright and Troxel (1967) and Williams and fault system to the deep crust and upper mantle, and (4) the others (1974). As noted by Lucchitta (1974), the western part of the genetic, spatial, and temporal relation between the fault patterns Colorado Plateau contains faults that are oriented similarly to and volcanism.

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Allison, I. S., 1949, Fault pattern of south-central Oregon [abs. ]: Geol. Roberts, M. T., 1974, Stratigraphy and depositional envorinments of the Soc. America Bull., v. 60, p. 1935. Crystal Spring Formation, southern Death Valley region, Anderson, E. M., 1951, The dynamics of faulting: Edinburgh, Oliver and California, in Death Valley region, California and Nevada, Geol. Boyd Ltd., 204 p. Soc. America Cordilleran Sec. Guidebook: p. 49-57. Anderson, R. E., 1971a, Thin skin distension in Tertiary rocks of south- Scholz, C. H., Barazangi, M., and Spar, M. L., 1971, Late Cenozoic eastern Nevada: Geol. Soc. America Bull., v. 82, p. 43-58. evolution of the Great Basin, western United States, as an ensialic 1971b, Thin skin distension in Tertiary rocks of southeastern interarc basin: Geol. Soc. America Bull., v. 82, p. 2979-2990. Nevada: Reply: Geol. Soc. America Bull., v. 82, p. 3533-3536. Shawe, D. R., 1965, Strike-slip control of Basin-Range structure in- 1973, Large-magnitude late Tertiary strike-slip faulting north of dicated by historic faults in western Nevada: Geol. Soc. America Lake Mead, Nevada: U.S. Geol. Survey Prof. Paper 794, 18 p. Bull., v. 76, p. 1361-1378. Atwater, Tanya, 1970, Implications of plate tectonics for the Cenozoic Smith, G. I., 1962, Large lateral displacement on Garlock fault, tectonic evolution of western North America: Geol. Soc. America California, as measured from offset dike swarm: Am. Assoc. Bull., v. 81, p. 3513-3536. Petroleum Geologists Bull., v. 46, p. 85-104. Becker, Hans, 1934, Die Beziehungen zwischen Felsengiberge und grossen Smith, R. B., and Sbar, M. L., 1974, Contemporary tectonics and seis- Becken im westlichen Nordamerika: Deutsch. Geol. Gesell. micity of the western United States with emphasis on the Inter- Zeitschr., v. 86, p. 115-120. mountain seismic belt: Geol. Soc. America Bull., v. 85, Bonham, H. F., 1969, Geology and mineral deposits of Washoe and p. 1205-1218. Storey Counties, Nevada: Nevada Bur. Mines Bull. 70, 136 p. Stewart, J. H., 1971, Basin and Range structure: A system of horsts and Carey, S. W., 1958, The tectonic approach to continental drift, in grabens produced by deep-seated extension: Geol. Soc. America Carey, S. W., ed., Continental drift—A symposium: Hobart, Univ. Bull., v. 82, p. 1019-1044. Tasmania, p. 177-355. Stewart, J. H., and Carlson, J. E., 1974, Preliminary geologic map of Carr, W. J., 1974, Summary of tectonic and structural evidence for stress Nevada: U.S. Geol. Survey. orientation at the Nevada Test Site: U.S. Geol. Survey Open-File Stewart, J. H., and Poole, F. G., 1974, Lower Paleozoic and uppermost Rep. 74-176, 53 p. Precambrian Cordilleran miogeocline, Great Basin, western United Cook, K. L., 1969, Active rift system in the Basin and Range province: States, in Dickinson, W. R., ed., Tectonics and sedimentation: Tectonophysics, v. 8, p. 469-5 11. Soc. Econ. Paleontologists and Mineralogists Spec. Pub. 22, Davis, G. A., and Burchfiel, B. C., 1973, Garlock fault: An inter- p. 28-57. continental transform structure, southern California: Geol. Soc. Suppe, John, Powell, C., and Berry, R., 1975, Regional topographic, America Bull., v. 84, p. 1407-1422. seismicity, Quaternary volcanism, and the present-day tectonics Donath, F. A., 1962, Analysis of Basin-Range structure, south-central of the western United States: Am. Jour. Sci. v. 274A, p. 397-436. Oregon: Geol. Soc. America Bull., v. 73, p. 1-16. Taubeneck, W. H., 1971, Idaho batholith and its southern extension: Eaton, J. E., 1932, Decline of Great Basin, southwestern United States: Geol. Soc. America Bull., v. 82, p. 1899-1928. Am. Assoc. Petroleum Geologists Bull., v. 16, p. 1-49. Thompson, G. A., 1971, Thin skin distension in Tertiary rocks of south- Eaton, J. P., 1963, Crustal structure in northern and central California eastern Nevada: Discussion: Geol. Soc. America Bull., v. 82, from seismic evidence, in Bailey, E. H., ed., Geology of northern p. 3529-3532. California: California Div. Mines and Geology Bull. 190, Thompson, G. A., and Burke, D. B., 1973, Rate and direction of p. 419-426. spreading in Dixie Valley, Basin and Range: Geol. Soc. America Gay, T. E., Jr., and Aune, Q. A., 1958, Geologic map of California, Bull., v. 84, p. 627-632. Alturas sheet: California Dept. Natural Resources, Div. Mines, 1974, Regional geophysics of the Basin and Range province: scale 1:250,000. Ann. Rev. Earth and Planetary Sci., v. 2, p. 213-238. Gilluly, J., 1963, The tectonic evolution of the western United States: Troxel, B. W., Wright, L. A., and Jahns, R. H., 1972, Evidence for Geol. Soc. London Quart. Jour., v. 119, p. 133-174. differential displacement along the Garlock fault zone, California: 1970, Crustal deformation in the western United States, in Geol. Soc. America Abs. with Programs, v. 4, p. 250. Johnson, H., and Smith, B. L., eds., The megatectonics of Tschanz, C. M., and Pampeyan, 1970, Geology and mineral deposits of continents and oceans: New Brunswick, N.J., Rutgers Univ. Press, Lincoln County, Nevada: Nevada Bur. Mines Bull. 73, p. 83-84. p. 47-73. Williams, E. G., Wright, L. A., and Troxel, B. W., 1974, The Noonday Griscom, Andrew, 1973, Bouguer gravity map of California, Redding Dolomite and equivalent stratigraphic units, southern Death sheet: California Div. Mines and Geology Map sheet, 13 p. Valley region, California, in Death Valley region, California, Hamilton, Warren, and Myers, W. B., 1966, Cenozoic tectonics of the Geol. Soc. America Cordilleran Sec. Guidebook: p. 73-78. western United States: Rev. Geophysics, v. 4, p. 509-549. Wise, D. U., 1963, An outrageous hypothesis for the tectonic pattern Hill, M. L., and Dibblee, T. W., 1953, San Andreas, Garlock, and Big Pine of the North America Cordillera: Geol. Soc. America Bull., v. 74, faults, California: Geol. Soc. America Bull., v. 64, p. 443-458. p. 357-362. Hill, M. L., and Troxel, B. W., 1966, Tectonics of the Death Valley Woollard, C. P., and Joesting, H. R., 1964, Bouguer gravity anomaly region, California: Geol. Soc. America Bull., v. 77, p. 435-438. map of the United States: U.S. Geol. Survey. Hunt, C. B., and Mabey, D. R., 1966, Stratigraphy and structure, Death Wright, L. A., and Troxel, B. W., 1967, Limitations on right-lateral, Valley, California: U.S. Geol. Survey Prof. Paper 494-A, 162 p. strike-slip displacement, Death Valley and Furnace Creek Jennings, C. W., 1973, State of California preliminary fault and geologic fault zones, California: Geol. Soc. America Bull., v. 78, map: California Div. Mines and Geology Prelim. Rept. 13. p. 933-958. King, P. B., 1969, Tectonic map of North America: U.S. Geol. Survey. 1968, Evidence of northwestward crustal spreading and trans- Lawrence, R. D., 1976, Strike-slip faulting terminates the Basin and form faulting in the southwestern part of the Great Basin, Range province in Oregon: Geol. Soc. America Bull., v. 87, California and Nevada [abs.]: Geol. Soc. America Spec. Paper p. 846-850. 121, p. 580-581. Longwell, C. R., 1945, Low-angle normal faults in the Basin and Range 1970, Summary of regional evidence for right-lateral displacement province: Am. Geophys. Union Trans., v. 26, pt. 1, p. 107-118. in the western Great Basin: Discussion: Geol. Soc. America 1971, Measure of lateral movement on Las Vegas shear zone, Bull., v. 81, p. 2167-2174. Nevada: Geol. Soc. America Abs. with Programs, v. 3, p. 152. 1971, Thin-skinned, megaslump model of Basin-Range structure Lucchitta, lvo, 1974, Structural evolution of northwest Arizona and its as applicable to the southwestern Great Basin: Geol. Soc. relationship to adjacent Basin and Range province structures, in America Abs. with Programs, v. 3, p. 758. Geology of northern Arizona, Pt. I. Regional studies: Geol. Soc. 1973, Shallow-fault interpretation of Basin-Range structure, America Rocky Mtn. Sec. in Dejong, K., and Scholten, R., eds., Gravity and tectonics: McKee, E. H., 1968, Age and rate of movement of the northern part New York, John Wiley & Sons, p. 397-407. of the Death Valley-Furnace Creek fault zone, California: Geol. Soc. America Bull., v. 79, p. 509-512. ACKNOWLEDGMENTS Noble, L. F., 1941, Structural features of the Virgin Spring area, Death Reviewed by W. J. Carr, M. L. Hill, M. W. Reynolds, G. A. Valley, California: Geol. Soc. America Bull., v. 52, p. 941-1000. Thompson, B. W. Troxel, and Barry Voight. Poole, F. G., Elston, D. P., and Carr, W. J., 1965, Geologic map of the Supported in part by National Science Foundation Grant Cane Spring quadrangle, Nye County, Nevada: U.S. Geol. Survey GA 41700. Geol. Quad. Map GQ-455. Proffett, J. S., Jr., 1971, Late Cenozoic structure in the Yerington MANUSCRIPT RECEIVED DECEMBER 12,1975 district, Nevada, and the origin of the Great Basin: Geol. Soc. America Abs. with Programs, v. 3, p. 181. MANUSCRIPT ACCEPTED JUNE 1, 1976

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