TECTONICS, VOL. 8, NO. 3, PAGES453-467, JUNE 1989 EVOLUTION OF EXTENSIONAL BASINS AND BASIN AND RANGE TOPOGRAPHY WEST OF DEATH VALLEY, CALIFORNIA K.V. Hodges,L.W. McKenna,J. Stock •, J. Knapp, L. Page,K. Sternlof, D. Silverberg,G. Wrist2, and J. D. Walker 3 Department of Earth, Atmospheric,and Planetary Sciences,Massachusetts Institute of Technology, Cambridge Abstract. Neogeneextension in the Death Valley system remained active during development of region, SE California, has produced a variety of PanamintValley and, thus, during developmentof sedimentarybasins. Diachronousmovements on an modernBasin and Rangetopography as well. These array of strike-slip and normal fault systemshave results indicate that large-scale extension in the resultedin the uplift andpreservation of olderbasins Death Valley region,accommodated by movementon in modernranges. One of the bestexposed of these low- to moderate-angle normal fault systemsand is the Nova basin on the western flank of the high-angle strike-slipfault systems,is a continuing Panamint Mountains. The Nova basin includes over process. Basin and Range topography in the 2000 m of sedimentaryand volcanicrocks deposited PanamintValley- Death Valley areawas generatedat during denudation of the Panamint Mountains least in part by displacements on low-angle metamorphiccore complex in late Miocene(?)- early detachmentsrather than high-angle normal faults. Pliocenetime. The principalgrowth structure for the basinwas the Emigrant detachment,which initiated andmoved at a low angle. Modern PanamintValley, INTRODUCTION west of the range, developedas a consequenceof Late Pliocene- Recent,kinematically linked move- The fact that topographyin the Basin and Range ment on the right-slip, high-angleHunter Mountain Province of the western United States is controlled fault zone and the low-angle Panamint Valley by normal faulting has been recognizedfor over a detachment. Detailed mapping of the intersection century [e.g., Gilbert, 1875]. Surprisingly,there is between the Emigrant and Panamint Valley still no consensuson the geometric behavior of detachmentsdemonstrates that segmentsof the earlier observedrange-bounding faults as they dip beneath the adjacentbasins. For many decadesthe bulk of the geological community believed that the vast majorityof thesestructures are planar and dip steeply 1Now at Department of Earthand Planetary (see reviews by Thompson, [1967], and Stewart, Sciences,Harvard University, Cambridge [1971, 1978]), even thoughdetailed studiesin areas 2 Nowat GeologyInstitute, Swiss Federal of high relief and good exposure(like the southern Instituteof Technology,Z'tirich, Switzerland Basin and Range) have shownthat at least someof 3 Nowat Department of Geology,University of the structuresthat dip steeplyat the surfaceare listtic, Kansas, Lawrence. flattening abruptly beneath the adjacent basin [Longwell, 1945; Hamblin, 1965; Anderson, 1971; Copyright1989 Wright and Troxel, 1973]. by the AmericanGeophysical Union With the recognition that large-scale extension occurredin the Basin and Range in early to middle Papernumber 890TC00015. Tertiary time [Hamiltonand Myers, 1966; Hamilton, 0278-7407/89/89TC-00015510.00 1969; Proffett, 1977] and that much of this extension 454 Hodgeset al.: Evolutionof ExtensionalBasins West of DeathValley Fig. 1. Tertiaryfault systems of theDeath Valley region. Ranges are stippled. Normal and strike-slip faults are shownby heavylines; hatchures are on the hangingwall sideof normalfaults, and arrowsindicate relative motionon strike-slipfaults. HM, HunterMountain; HMFZ, HunterMountain fault zone;SV, SalineValley. The areashown in the tectonicmap (Plate 1) is outlined. may have beenaccommodated by movementon low- GEOLOGIC SETTING angle normal faults of regional extent [Armstrong, 1972; Wernicke, 1981, 1985; Allmendinger et al., The Death Valley area of southeasternCalifornia 1983], some workers postulated that the late has been the site of large-scaleextension since at Cenozoic development of Basin and Range least middle Miocene time [Cemen et al., 1982]. topographywas a fundamentallydifferent process This extension was accommodatedby listric and from earlier extension on low-angle faults [e.g., planar normal faults and by NW-trending, right- Zoback et al., 1981; Eaton, 1982]. This view was lateral strike-slip faults which served as transfer challengedby Hamilton [1982], who suggestedthat structures between normal fault systems. The Neogene- Recent Basin and Range topography interplay between normal and strike-slip fault formed concurrently with movement on large systems has led to the development of two detachmentsystems; by Dickinsonet al. [ 1987], who spectacularexamples of "pull-apart"[Burchfiel and argued that characteristic Basin and Range Stewart, 1966] or rhombhedral basins: Panamint topographyof mid-Tertiary age was controlledby Valley andcentral Death Valley itself. Thesevalleys low-angle faulting in the Galiuro Mountains, are separated by the Panamint Mountains, a southeasternArizona; and by Burchfiel et al. [1987], metamorphiccore complexwhich evolvedover the who demonstratedthat the modemfault boundingthe middle Miocene- Recentinterval (Figure 1). Panamint Mountains, southeastern California, must It is convenient to think of the northern and central have initiatedat an angleof lessthan 15ø . PanamintMountains in termsof four tectonicplates The Panamint Mountains (Figure 1) constitutean distinguishedby metamorphicgrade and structural especially interesting case for the study of history(Figure 2). The structurallylowest plate (or extensionalbasin evolution becausethey contain an "Parautochthon")consists of Precambriancrystalline uplifted, upper Miocene(?) - Pliocene basin, basementintruded by Miocene (?) graniteporphyry developed during the extensional evolution of a dikes [Hunt and Mabey, 1966; Stern et al., 1966]. "metamorphiccore complex,"that lies immediately The "Lower Allochthon"is composedof middle and adjacent to a modern Basin and Range basin: lower Proterozoic crystalline basementand upper PanamintValley. In this paper we discussthe age Proterozoic strata, which were metamorphosedat and structuralevolution of eachbasin and arguethat greenschistto lower amphibolitefacies conditions they formed as part of a continuousextensional between middle Mesozoic and early Tertiary time process in which low-angle faulting played a [Labotka et al., 1985] and have been intruded by dominant role. Cretaceousgranites. Several phasesof ductile to Hodgeset al.' Evolutionof ExtensionalBasins West of DeathValley 455 Stovepipe_•-• highest"Upper Allochthon"includes the following: Wells (1) somesmall (< 1 km2) structuralslices of Lower Allochthon and Middle Allochthon lithologiesat its easternmost exposures; (2) a thick section of BP Paleozoic rocks of Middle Allochthon affinity at PanamintButte (Figure 2); and (3) synextensional, 10 km Pliocenesedimentary and volcanic rocks of the Nova Formation [Hopper, 1947; Hall, 1971; Walker and Coleman, 1987]. The contactsbetween the four platesin the central Panamint Mountains are temporally distinct, consistentlytop-to-the-northwest, generally low- anglenormal faults. The structuresthat separate the Lower Allochthonfrom the Parautochthonare part of the Eastern Panamint fault system [Hodges et al., 1989]. This fault systemis exposednear the eastern foot of the Panamint Mountains and presentlydips shallowlywestward. Palinspastic reconstruction of a sequenceof Upper Miocenevolcanic rocks erupted synchronouslywith developmentof the fault system indicatesthat its originaldip musthave been 45ø-60 ø westward[McKenna and Hodges, 1989]. The family of structuresthat separatesthe Lower Allochthonfrom structurallyhigher plates is defined as the Tucki Mountain detachment system. The oldestfault in this system(> 10.7 Ma; Hodgeset al., [1989]) is the Harrisburg detachment, which presently dips eastward beneath the Middle Allochthon due to Pliocenedoming of the range but is inferredto have initially dippedwestward [Hodges Parautochthon MiddleAllochthon et al., 1987]. The youngestfault in the systemis the west-dippingEmigrant detachment, which servedas LowerAllochthon I i i i [ Upper Allochthon the principal growth fault for the Nova Basin. THE NOVA BASIN EmigrantSubsystem • PanamintFault Zone Valley TownePass Fault Hopper [1947] proposed the name "Nova Formation"for a thick sectionof alluvial fan deposits Fig. 2. Location and fault map of the Panamint ("fanglomerates")and intercalatedvolcanic rocks Range. Key indicatespattern and fault ornamen- exposed along the west flank of the northern tation; fault barbs are on the hanging wall side of PanamintRange. Hall [1971] abandoneduse of the low-angle structures. BP, Black Point; EF, term "Nova Formation" becauseHopper had been Emigrant fault; HF, Harrisburg Flats; HCP, Hall vague about its definition; instead,he preferredto Canyon Pluton; LCS, Little Chief Stock; PB, distinguisha variety of upperMiocene (?) - Recent Panamint Butte; PP, Pinto Peak; PVFZ, Panamint alluvial packages, based on their degree of Valley fault Zone; S, Skidoo townsite;SG, Skidoo induration, clast composition,and position in the Granite; TC, Tuber Canyon; TM, Tucki Mountain; sequencerelative to volcanichorizons. We believe TP TelescopePeak; TPF, Towne Pass fault; WC, that the "Nova Formation" nomenclature serves a Wildrose Canyon. The locations of Plate 1 and usefulpurpose by distinguishingthe more indurated Figure 5 are shownby the labeledboxes. upperMiocene (?) - Pliocenedeposits from the poor- ly consolidatedupper