isopach pattern of the lower cambrian zabriskie quartzite death valley region california nevada how useful in tectonic reconstructions new thickness measurements of the lower cambrian zabriskie quartzite indicate an original isopach pattern much less regular than once supposed and thus less useful as an indicator of the magnitude of lateral slip on the death valley fault system but within a wide range of possible restorations the isopachs conform with the locations of proterozoic highlands and basins the zabriskie quartzite being mature laterally persistent and unlike the underlying formations devoid of evidence of rifting apparently records the beginning of the passive stage of the developing cordilleran miogeocline

recurrence behavior of short term slow slip and correlated nonvolcanic tremor episodes in western shikoku southwest japan 1 from the national research institute for earth science and disaster prevention hi net tiltmeter data we determine time dependent source processes of seven repeating short term slow slip events sse in the western shikoku region southwest japan over the period from 2002 to 2007 the tiltmeters record clear signals of sses characterized by a slow rise a week long duration and a magnitude on the order of 10 2 10 1 rad we apply a time dependent slip inversion method to the tilt records for the seven sses for each sse a slip area migrates in the strike direction of the subducting slab at a rate of 10 km d 1 comparing the slow slip area with epicenters of accompanying nonvolcanic tremors in subday time resolution we find that the two phenomena are located on a smaller area than previously reported and migrate as a group a moment rate function for each sse exhibits good correlation with the temporal change in tremor activity a comparison of the slip distributions of all of the analyzed sses shows that there is a patch of slow slip area 30 km in diameter that is shared by all of the episodes in addition the location of the slip patch is in good agreement with the epicenters of tremors and very low frequency earthquakes these lines of evidence suggest that the identified slip patch is one of the main slow slip patches in the region and a recurrence of sses may be controlled by the patch and that these slow earthquakes might be different manifestations of a single slip process on the deep plate interface

cenozoic tectonism in the central basin and range magnitude rate and distribution of upper crustal strain a wealth of pre cenozoic geologic markers across the central basin and range province defined mainly by thrust faults developed within a miogeoclinal wedge makes it one of the best areas on earth to reconstruct large scale continental extension we use this 100 000 km 2 region bounded by the southern sierra nevada on the west and the colorado plateau on the east to illustrate the concepts of correlation and misalignment for regional strain markers and of strain compatibility and kinematic viability in palinspastic reconstructions the results indicate 250 to 300 km of west northwest motion of the sierra away from the plateau accommodated by both crustal thinning and north south shortening tertiary intermontane basin deposits and mineral cooling ages of deeply exhumed rocks constrain the overall kinematics of motion most of the westward motion occurred between 16 and 5 ma at rates near 2 cm yr slowing to 1 to 1 5 cm yr in the last 5 ma we have quantified the partitioning of strain between vertical crustal thinning via normal faults and map view plane strain via conjugate strike slip faults by placing a grid of 10 x 10 km elements on a retrodeformed map of the region and measuring the increase in area of grid elements between the undeformed and present day grids this analysis yields a maximum finite elongation of the basin and range at 36 n to 37 n of 3 4 oriented n73 w map view area balance shows that 20 percent of this elongation is compensated by north south shortening and 80 percent by crustal thinning this yields an average thinning factor for the upper crust of 2 7 between the sierra and plateau inconsistent with the hypothesis that neogene deformation in the central basin and range is predominantly dextral shear plane strain these results in concert with the observation that the southern sierra nevada has similar crustal thickness to the central basin and range support the hypothesis of large scale eastward flow of sierran deep crust during extension

late cenozoic sedimentation and volcanism during transtensional deformation in wingate wash and the owlshead mountains death valley abstract new 1 24 000 scale mapping geochemical analyses of volcanic rocks and ar ar and tephrochronology analyses of the wingate wash northern owlshead mountain and southern panamint mountain region document a complex structural history constrained by syntectonic volcanism and sedimentation in this study the region is divided into five structural domains with distinct but related histories 1 the southern panamint domain is a structurally intact gently south tilted block dominated by a middle miocene volcanic center recognized as localized hypabyssal intrusives surrounded by proximal facies pyroclastic rocks this miocene volcanic sequence is an unusual alkaline volcanic assemblage ranging from trachybasalt to rhyolite but dominated by trachyandesite the volcanic rocks are overlain in the southwestern panamint mountains by a younger late miocene fanglomerate sequence 2 an upper wingate wash domain is characterized by large areas of quaternary cover and complex overprinting of older structure by quaternary deformation quaternary structures record n s shortening concurrent with e w extension accommodated by systems of strike slip and thrust faults 3 a central wingate wash domain contains a complex structural history that is closely tied to the stratigraphic evolution in this domain a middle miocene volcanic package contains two distinct assemblages a lower sequence dominated by alkaline pyroclastic rocks similar to the southern panamint sequence and an upper basaltic sequence of alkaline basalt and basanites this volcanic sequence is in turn overlain by a coarse clastic sedimentary sequence that records the unroofing of adjacent ranges and development of n s trending west tilted fault blocks we refer to this sedimentary sequence as the lost lake assemblage 4 the lower wingate wash northern owlshead domain is characterized by a gently north dipping stratigraphic sequence with an irregular unconformity at the base developed on granitic basement the unconformity is locally overlain by channelized deposits of older tertiary red conglomerate some of which predate the onset of extensive volcanism but in most of the area is overlain by a moderately thick package of middle miocene trachybasalt trachyandesitic ash flows lithic tuff basaltic cinder basanites and dacitic pyroclastic debris and lahar flows with localized exposures of sedimentary rocks the upper part of the miocene stratigraphic sequence in this domain is comprised of coarse grained clastic sediments that are apparently middle miocene based on ar ar dating of interbedded volcanic rocks this sedimentary sequence however is lithologically indistinguishable from the structurally adjacent late miocene lost lake assemblage and a stratigraphically overlying plio pleistocene alluvial fan a relationship that handicaps tracing structures through this domain this domain is also structurally complex and deformed by a series of northwest southeast striking east dipping high angle oblique sinistral normal faults that are cut by left lateral strike slip faults the contact between the southern panamint domain and the adjacent domains is a complex fault system that we interpret as a zone of late miocene distributed sinistral slip that is variably overprinted in different portions of the mapped area the net sinistral slip across the wingate wash fault system is estimated at 7 9 km based on offset of proterozoic crystal springs formation beneath the middle miocene unconformity to as much as 15 km based on offset volcanic facies in middle miocene rocks to the south of wingate wash the northern owlshead mountains are also cut by a sinistral northwest dipping oblique normal fault referred to as the filtonny fault with significant slip that separates the lower wingate wash and central owlshead domains the filtonny fault may represent a young conjugate fault to the dextral southern death valley fault system and may be the northwest dipping fault imaged by cocorp studies similarly younger deformation in upper wingate wash is probably broadly related to distributed dextral shear along the panamint valley fault system earlier deformation late miocene is more difficult to constrain because of overprinting but appears to be dominated by an e w extension recognized by a nnw striking northeast dipping sinistral oblique normal faults n s striking normal faults that splay in the northern owlshead mountains and include the large west tilted fault blocks of the northern owlshead mountains

late cenozoic extensional transfer in the walker lane strike slip belt nevada mid miocene to pliocene 11 to 6 ma displacement on the shallowly northwest dipping silver peak lone mountain detachment system transferred 30 to 40 km of right slip from the furnace creek transcurrent fault 85 km east northeast to the central walker lane strike slip faults top to the northwest slip on the detachment was accompanied by upper plate extension on steeply dipping faults and large scale exhumation of midcrustal rocks of the lower plate complex doubly plunging northwest trending folds turtleback structures control the outcrop distribution of the extensional complex and formed in response to simple shear of the footwall complex activity on the detachment ceased as miocene pliocene 6 4 8 ma volcanic rocks were erupted and deformed during the final stage of northwest trending folding late pliocene to holocene displacement transfer shifted north to a curved array of steeply dipping faults that may be underlain by a shallowly northwest dipping detachment

late cretaceous extensional unroofing in the funeral mountains metamorphic core complex california new field and geochronologic data document the existence of late cretaceous extensional structures in the death valley region california nevada we have mapped two major low angle ductile shear zones that omit stratigraphy in the footwall of the funeral mountains metamorphic core complex intervening strata have been strongly attenuated although stratigraphic offset across the shear zones is only 1 5 km the presence of a large metamorphic discontinuity suggests that the amount of unroofing must be much greater the timing of shear zone formation attenuation and subsequent northwest vergent folding is constrained by u pb geochronology on 1 prekinematic or synkinematic and 2 postkinematic pegmatites deformation was taking place by 72 ma and had ended by 70 ma these results support earlier petrologic and geochronologic data that suggested substantial unroofing of the funeral mountains in late cretaceous time and add to a growing body of evidence for widespread mesozoic extension in the hinterland of the sevier thrust belt

re evaluation of the middle miocene eagle mountain formation and its significance as a piercing point for the interpretation of extreme extension across the death valley region california u s a abstract the death valley area of eastern california and southern nevada has been highly influential in the development of ideas about extreme crustal extension one of the tightest constraints on death valley extension is apparently provided by clasts in inferred alluvial fan deposits of the eagle mountain formation 15 11 ma and their source in the hunter mountain batholith now located 100 km from some of the deposits because alluvial fans are usually less than 10 20 km in radius the remaining separation has been interpreted as tectonic new research reported here suggests that the eagle mountain formation at its type location was deposited in a fluvial lacustrine setting and provides no constraint on either the magnitude or the direction of tectonic transport and or crustal extension confidence in palinspastic reconstruction thus depends on resolving ambiguities in the correlation of pre extensional markers or on the recognition of demonstrably proximal facies tectonically distributed across the region the succession at eagle mountain comprises 1 diffusely stratified monolithologic carbonate breccia and sandstone 140 m onlapping cambrian carbonate rocks at an unconformity with 110 140 m of relief fluvial or fluvially influenced 2 10 m of tabular bedded siltstone diamictite and sandstone lacustrine 3 cross stratified and channelized sandstone and polymict conglomerate bearing hunter mountain clasts with minor siltstone and carbonate 110 m mostly fluvial and 4 tabular bedded sandstone siltstone and minor carbonate 140 m mostly lacustrine eight prominent stratigraphic discontinuities mapped within the third interval are characterized by up to 15 m of local erosional relief and by abrupt upward coarsening from siltstone or carbonate to conglomerate or sandstone a fluvial interpretation for the same critical part of the succession is based upon the existence of the mapped surfaces the ubiquitous development of channels trough cross stratification and upward fining trends particularly between the mapped surfaces and the abundance of well rounded clasts in conglomerate paleocurrents are generally directed between southward and eastward although with considerable dispersion and they shift from approximately southward or southeastward in the mostly fluvial deposits to approximately eastward in the upper lacustrine interval an unusual feature of the eagle mountain formation at eagle mountain is the presence of five crosscutting conglomerate bodies interpreted as vertically infilled fissures of tectonic origin numerous normal reversed normal and oblique slip faults with up to 34 m of stratigraphic separation are thought to postdate sedimentation and tilting of the eagle mountain formation after 11 ma

localisation and temporal variability of groundwater discharge into the dead sea using thermal satellite data the semi arid region of the dead sea heavily relies on groundwater resources this dependence is exacerbated by both population growth and agricultural activities and demands a sustainable groundwater management yet information on groundwater discharge as one main component for a sustainable management varies significantly in this area moreover discharge locations volume and temporal variability are still only partly known a multi temporal thermal satellite approach is applied to localise and semi quantitatively assess groundwater discharge along the entire coastline the authors use 100 landsat etm band 6 2 data spanning the years between 2000 and 2011 in the first instance raw data are transformed to sea surface temperature sst to account for groundwater intermittency and to provide a seasonally independent data set t maximum sst range per pixel within biennial periods is calculated subsequently groundwater affected areas gaa are characterised by t 10 c this allows the exact identification of 37 discharge locations clusters along the entire dead sea coast which spatially correspond to available in situ discharge observations tracking the gaa extents as a direct indicator of groundwater discharge volume over time reveals 1 a temporal variability correspondence between gaa extents and recharge amounts 2 the reported rigid ratios of discharge volumes between different spring areas not to be valid for all years considering the total discharge 3 a certain variability in discharge locations as a consequence of the dead sea level drop and finally 4 the assumed flushing effect of old dead sea brines from the sedimentary body to have occurred at least during the two series of 2000 2001 and 2010 2011

the frictional behavior of lizardite and antigorite serpentinites experiments constitutive models and implications for natural faults laboratory studies of the frictional behavior of rocks can provide important information about the strength and sliding stability of natural faults we have conducted friction experiments on antigorite and lizardite serpentinites rocks common to both continental and oceanic crustal faults we conducted both velocity step tests and timed hold tests on bare surfaces and gouge layers of serpentinite at room temperature we find that the coefficient of friction of lizardite serpentinite is quite low 0 15 0 35 and could explain the apparent low stresses observed on crustal transform faults while that of antigorite serpentinite is comparable to other crustal rocks 0 50 0 85 the frictional behavior of both types of serpentinite is well described by a two mechanism model combining state variable dominated behavior at high slip velocities and flow dominated behavior at low velocities the two mechanism model is supported by data from velocity step tests and timed hold tests the low velocity behavior of serpentinite is strongly rate strengthening and should result in stable fault creep on natural faults containing either antigorite or lizardite serpentinite

time domain observations of a slow precursor to the 1994 romanche transform earthquake low frequency spectral anomalies have indicated that some large earthquakes are preceded by extended episodes of smooth moment release but the reality of these slow precursors has been debated because they have not been directly observed in the time domain high gain seismograms from the 14 march 1994 romanche transform event moment magnitude m w 7 0 show a precursory ramp with a moment of 7 1018 newton meters beginning about 100 seconds before the arrival of the high frequency p waves this precursor was the initial phase of a slow component of slip that released nearly half of the total moment of the earthquake such behavior may be typical for large earthquakes on the oceanic ridge transform system

thermal anomalies associated with forced and free ground water convection in the dead sea rift valley the dead sea rift valley is a left lateral transform along which several rhombshaped grabens were formed at the sea of galilee which is one of these rhomb shaped grabens ambiguous heat fluxes were measured 70 80 mw m 2 at the central part of the lake 36 mw m 2 at the lake s southern coast 10 km apart and most surprising about 135 mw m 2 at the southern golan heights 6 8 km east of the graben margin a detailed geologic cross section traversing the entire sedimentary basin was constructed the hydrodynamics in this cross section were analyzed quantitatively using a two dimensional finite element code that solves the coupled variable density ground water flow and conductive convective heat transfer equations on the basis of numerical simulations different mechanisms of basin scale groundwater convection are suggested for the two sides of the rift that could influence the transport of heat 1 forced convection gravitydriven flow of hot brines from deeper aquifers to the land surface at the western side and 2 large scale free convection buoyancy driven flow of deep ground water at the eastern side the different heat fluxes within the rift valley are attributed to the different lithologies and to the locations of specific conduits through which the hot ground waters ascend from deeper horizons these simulations also explain the different salinities of the hot springs on the two sides of the rift

seismic evidence for widespread serpentinized forearc upper mantle along the cascadia margin petrologic models suggest that dehydration and metamorphism of subducting slabs release water that serpentinizes the overlying forearc mantle to test these models we use the results of controlled source seismic surveys and earthquake tomography to map the upper mantle along the cascadia margin forearc we find anomalously low upper mantle velocities and or weak wide angle reflections from the top of the upper mantle in a narrow region along the margin compatible with recent teleseismic studies and indicative of a serpentinized upper mantle the existence of a hydrated forearc upper mantle wedge in cascadia has important geological and geophysical implications for example shearing within the upper mantle inferred from seismic reflectivity and consistent with its serpentinite rheology may occur during aseismic slow slip events on the megathrust in addition progressive dehydration of the hydrated mantle wedge south of the mendocino triple junction may enhance the effects of a slab gap during the evolution of the california margin

spatial and temporal distribution of seismicity along the northern mid atlantic ridge 15 35 n 1 a detailed investigation of the relationship between the spatial and temporal patterns of the seismic activity recorded by six autonomous hydrophones and the structure of the northern mid atlantic ridge between 15 and 35 n is presented two years of monitoring yielded a total of 3485 hydroacoustically detected events within the array recorded by four or more hydrophones the seismically active zone extends 20 km to either side of the ridge axis consistent with earlier results from studies of fault morphology along the axis hydrophone recorded activity shows important variations areas with intense and persistent seismic activity stripes stand in sharp contrast to areas that lack seismicity gaps the regions of persistent activity are a new observation at mid ocean ridges in general the patterns of seismically active inactive regions are also recognized in the 28 year teleseismic record implying that these patterns are maintained at timescales between a few years and a few decades we find no simple relationship between individual segment variables e g length or trend of the segment maximum offset of discontinuities or along axis change in mantle bouguer anomaly mba and water depths and number of hydrophone recorded events there does appear to be a correlation between axial thermal structure and seismicity regions of low and high numbers of events would thus correspond to thinner hotter and thicker colder lithosphere respectively seismicity may reflect thermal structure at short timescales decadal or longer while relief and inferred crustal thickness may integrate this structure over longer periods of time order of 1 myr

upper neogene stratigraphy and tectonics of death valley a review abstract new tephrochronologic soil stratigraphic and radiometric dating studies over the last 10 years have generated a robust numerical stratigraphy for upper neogene sedimentary deposits throughout death valley critical to this improved stratigraphy are correlated or radiometrically dated tephra beds and tuffs that range in age from 3 58 ma to

high angle origin of the currently low angle badwater turtleback fault death valley california the late cenozoic badwater turtleback fault separates an upper plate of volcanic and sedimentary rocks from a lower plate of predominantly mylonitic plutonic and metamorphic rocks the turtleback fault however is not a single continuous surface but consists of at least three generations of faults these faults occur as discrete crosscutting segments that progressively decrease in age and increase in dip to the west therefore they probably began at moderate to steep angles but rotated to lower angles with extensional strain if so lower plate mylonitic rocks also restore to steeper dips and suggest that transport of the upper plate occurred on moderate to steeply dipping surfaces in the middle and upper crust the crosscutting nature of the fault segments and their initial moderate to steep dips plus a possible offset marker on one of the segments are most consistent with moderate amounts of extension in the death valley region

rolling hinge or fixed basin a test of continental extensional models in death valley california united states two models are typically offered to explain severe continental extensional tectonism low angle detachment faults with alloch thonous sedimentary basins above a crustal rolling hinge or differential displacement on systems of distinct deeply rooted normal faults with in place sedimentary basins structural and stratigraphic relationships between the badwater turtleback and the adjacent furnace creek basin in death valley provide a test of these contrasting models there ductile extensional deformation of basement rock at the badwater turtleback coincided with brittle extensional deformation and local uplift in the adjacent furnace creek basin between 13 and 18 ma in the furnace creek basin crustal extension of this age is evident as 1 greater fault density and offset in pre 13 ma rocks relative to post 13 ma rocks and 2 the presence of laterally variable sedimentary breccias and conglomerates which indicate a syndepositional paleotopographic high this high is approximately on line with the likely projection of an early badwater turtleback fault the surface expression of the turtleback mylonites these relationships indicate that the badwater turtleback and furnace creek basin were contiguous prior to 13 ma and that the basin formed in place relative to the black mountains basement these findings support arguments for extension in the death valley area by distinct deeply rooted fault zones rather than by a rolling hinge detachment fault

a slow earthquake sequence on the san andreas fault earthquakes typically release stored strain energy on timescales of the order of seconds limited by the velocity of sound in rock over the past 20 years observations1 13 and laboratory experiments14 have indicated that rupture can also occur more slowly with durations up to hours such events may be important in earthquake nucleation15 and in accounting for the excess of plate convergence over seismic slip in subduction zones the detection of events with larger timescales requires near field deformation measurements in december 1992 two borehole strainmeters close to the san andreas fault in california recorded a slow strain event of about a week in duration and we show here that the strain changes were produced by a slow earthquake sequence equivalent magnitude 4 8 with complexity similar to that of regular earthquakes the largest earthquakes associated with these slow events were small local magnitude 3 7 and contributed negligible strain release the importance of slow earthquakes in the seismogenic process remains an open question but these observations extend the observed timescale for slow events by two orders of magnitude

large magnitude permian shortening and continental margin tectonics in the southern cordillera the last chance allochthon with displacement estimated to be 55 to 105 km and lateral extent possibly exceeding 300 km was inferred to be middle triassic and thus kinematically distinct from a belt of permian triassic deformation in the western mojave desert correlations of structures forming the death valley thrust belt which includes the last chance allochthon several subjacent structures and their inferred lateral equivalents suggest that prior to tertiary extension individual structures were laterally continuous for distances exceeding 150 km along strike from the nevada test site area southwest to the darwin plateau their inferred mesozoic age and the presence of an early triassic overlap sequence on the darwin plateau precluded projection of these structures farther south in spite of long recognized strain compatibility problems associated with large displacement on thrusts that apparently terminated there without suitable accommodation structures such as tear faults or lateral ramps these problems may be resolved if the last chance allochthon is permian consistent with structural correlations new isotopic data from post tectonic stocks and stratigraphic evidence a large permian turbidite basin near the darwin plateau can be interpreted as a marine foredeep resulting from emplacement of the 5 km thick allochthon rather than a local trough caused by transcurrent faulting during inferred permian triassic continental truncation i propose that anomalous eugeoclinal rocks in the western mojave desert have been emplaced against cratonic strata there by the last chance allochthon which foreshortened an originally narrow continental margin

stateline fault system a new component of the miocene quaternary eastern california shear zone the eastern california shear zone is an active north northwest trending zone of intraplate right lateral shear that absorbs 25 of pacific north america relative plate motion the stateline fault system sfs which includes several previously recognized discontinuously exposed quaternary structures along the california nevada border is in this paper defined as a continuous 200 km long zone of active dextral shear that includes from south to north the mesquite pahrump and amargosa valley segments recognition of this system expands the known extent of the eastern california shear zone 50 km to the east northeast from its traditionally recognized boundary along the death valley fault system proximal volcanic and rock avalanche deposits offset across the mesquite segment of the sfs indicate 30 4 km of slip on this structure since 13 1 0 2 ma this offset is an order of magnitude larger than previous estimates across this section of the sfs but it is consistent with larger offsets previously proposed for the central and northern sections the total offset and averaged slip rate since mid miocene time 2 3 0 35 mm yr are similar to those of other major faults across this portion of the basin and range which from east to west include the death valley panamint valley hunter mountain and owens valley fault systems however in contrast to these faults the average post mid miocene slip rate on the sfs is approximately twice that estimated from present day geodetic observations and an order of magnitude greater than estimates of average post mid pleistocene slip rates this discrepancy between long term short term and geodetically derived slip rates differs from other geologic geodetic slip rate discrepancies in the eastern california shear zone where geodetic slip rates are significantly faster than both long term and short term geologic slip rates this suggests that either the slip rate on the sfs has diminished over time such that the system is an abandoned strand of the relatively young eastern california shear zone or that the present day slip rate represents a transient period of slow slip such that strands of the shear zone must accommodate a complex spatial and temporal distribution of slip

hydrochemistry and groundwater system of the zerka ma in zara thermal field jordan abstract a groundwater flow model through the different geological successions from the upper cretaceous through the lower cretaceous sandstone and older units is presented in this paper the model is supported by the hydrochemical evolution of water types from the recharge areas in the highlands to discharge sites of thermal water at the slopes overlooking the dead sea the thermal water discharged in the zerka ma in zara areas consists of three end members mixed in different ratios with a component of old many thousands of years thermal water undersaturated in carbonate minerals and containing hundreds of milligrams per liter of free co2 the release of co2 gas upon discharge renders the water oversaturated with respect to carbonate minerals which results in aragonite precipitation the elevated temperature of the water in the reservoir 73 82 c is attributed to the presence of a heat storing layer topping the aquifer

distribution and provenance of the middle miocene eagle mountain formation and implications for regional kinematic analysis of the basin and range province conglomeratic strata from middle miocene sections in the central resting spring range and nearby eagle mountain california contain a clast assemblage including marble orthoquartzite fusulinid grainstone and coarse 1 m monzogabbro interstratified with tephras yielding laser fusion 40 ar 39 ar ages of 11 6 13 4 and 15 0 ma petrographic and geochronologic evidence ties the clast assemblage to a source area in the southern cottonwood mountains california 100 km west northwest of their present location in the upper 100 m of the resting spring range section conglomerates are derived almost exclusively from the southern cottonwoods source and sandstone modes are as much as 50 angular plagioclase derived from the monzogabbro the lack of dilution of this detritus by other sources and sedimentary features in both sections indicate 1 that deposition occurred on an alluvial fan with a north northeast paleoslope and 2 that transport of the gravels by sedimentary processes was probably 20 km north northeast in a direction normal to the present azimuth to their source therefore we interpret most or all of the net east southeast transport as a result of extensional and strike slip faulting between the cottonwood mountains and the resting spring range since 11 12 ma restoration of these deposits to a position 10 20 km north northeast of the eastern margin of the monzogabbro source east margin of the hunter mountain batholith yields a net tectonic displacement of the cottonwood mountains relative to the resting spring range of 104 km n67 w this result confirms previous reconstructions based on the restoration of isopachs in the cordilleran miogeocline pre cenozoic structural features and other proximal tertiary deposits in the region

uniqueness of geological correlations an example from the death valley extended terrain the northern death valley furnace creek fault zone is a major northwest trending fault system in the death valley region but the magnitude of offset and its significance to extensional tectonism in the region are controversial stratigraphic data have provided first order constraints on offset across the fault zone but offer limited resolution previous correlations of mesozoic thrust faults across the fault zone have relied on regional stratigraphic trends to fingerprint structurally similar thrust plates we show that a northeast trending mesozoic backfold within the predominantly east directed fold and thrust belt was probably continuous from the southern panamint range california to the belted range nevada the relative position of this antithetic structure allows uniquely compatible correlations of three mesozoic structures between two range blocks across the northern death valley furnace creek fault zone independent of stratigraphic arguments the offset structures have geometric properties of size vergence order and spacing that indicate a probability less than 10 4 of the mesozoic orogen identically repeating this structural suite in two unrelated places reconstruction of these correlative structures indicates 68 4 km n48 w 6 w of apparent dextral offset between the cottonwood and funeral mountains in general agreement with previous estimates based on stratigraphic observations but of substantially higher precision this reconstruction and the restoration of a 30 km separation between the funeral and grapevine mountains indicated by offset segments of the backfold suggest a simple pre extensional geometry for the mesozoic orogen in the death valley region consistent with observations from unextended blocks and analogous to that of the cordilleran orogen at the latitude of calgary alberta

isotopic analyses and hydrochemistry of the thermal springs along the eastern side of the jordan dead sea wadi araba rift valley abstract the isotopic composition of the present precipitation as well as the groundwaters of jordan is found to lie between the eastern mediterranean and the meteoric water lines whereas the isotopic compositions of precipitation and groundwater from north and central jordan plot between both lines those of southern jordan cluster closer to the meteoric water line the deep sandstone aquifer complex in central jordan receives water from the overlying tertiary upper cretaceous units as well as from the sandstones of southern jordan both contributions mix in the eastern part of central jordan flow from there in a westerly direction and discharge on the slopes above the dead sea at the interface of fresh groundwater and dead sea water mixing between the latter two waters takes place under a normal geothermal gradient the water is then discharged as thermal water with an isotopic composition following the equation d 3 97 18 o 16 9

tilt and rotation of the footwall of a major normal fault system paleomagnetism of the black mountains death valley extended terrane california paleomagnetic data have been obtained from miocene intrusions including crosscutting mafic and felsic dikes and proterozoic crystalline rocks to evaluate deformation during miocene and younger extension and unroofing of the black mountains death valley california synrift intrusions contain a well defined and at the site level well grouped magnetization interpreted to be of dual polarity the in situ direction of which is discordant in declination and inclination with an expected late cenozoic reference direction the oldest of these intrusions 11 6 0 2 ma gives a magnetite dominated remanent magnetization of high coercivity and high laboratory unblocking temperatures about 550 to 580 c that is interpreted to predate unroofing from midcrustal depths in situ site mean directions of this magnetization are directed toward the west and west northwest with moderate to shallow positive down and negative up inclinations the variation in direction of magnetization particularly inclination with site locality around the turtleback structures along the western flank of the black mountains is interpreted to result from folding of the intrusion after remanence acquisition younger intrusions 8 7 ma generally give magnetizations with inclinations similar to expected miocene values two populations of in situ site means are identified one with southwest declination and negative inclination the other with northward declination and positive inclination a preferred interpretation for footwall deformation involves from oldest to youngest 1 southwest side down tilting of the entire range block of some 20 to 40 to possibly 70 and at least locally folding of the crystalline rocks on a trend parallel to the death valley turtlebacks between 11 6 and 8 7 ma 2 progressive east to west footwall unroofing between 8 7 and ca 6 5 ma and 3 clockwise rotation 50 to 80 of much of the black mountains after the core detached from stable terrane to the west we interpret late rotation of the black mountains as oroflexure related to right lateral shear along the death valley fault zone

three dimensional model of the late cenozoic history of the death valley region southeastern california the accumulation of a large database on the timing and kinematics of late cenozoic deformation in the death valley region of southeastern california indicates a complex three dimensional history on the basis of paleogeographic reconstructions we suggest the system was initiated as a localized pull apart between two conjugate strike slip faults the garlock and furnace creek faults and evolved into a system characterized by distributed transtension related to the eastern california shear zone our reconstructions differ from previous models in the incorporation of significant vertical axis rotations of a number of crustal blocks to explain paleomagnetic data from the region the model may resolve 1 a long standing problem of the eastern termination of the garlock fault which is explained here as a complex system of splays that initially terminated in the pull apart between the furnace creek and garlock systems and 2 the complex architecture of the black mountains which is explained here in terms of initial extreme attenuation between the garlock and furnace creek systems with overprinting by a fold and normal fault system that operated simultaneously as a result of distributed transtension this model suggests much of the displacement field is taken up in rotations and translations and the actual crustal thinning in our model is relatively small 50 66 of original thickness

fold fault relationships in low angle detachment systems a close kinematic and timing relationship between low angle extensional faulting and upright to moderately inclined folding with fold axes parallel to the extension direction is established for two well exposed neogene detachment systems in the simplon region of the alps and in the death valley region of california fold amplitude is largest in the oldest mylonitic foliation of the footwall these folds are transected by younger mylonitic foliation s and cataclastic detachment faults which are themselves folded about similar axes in general the amplitude decreases and the wavelength increases for progressively younger fold structures consistent with a history of progressive folding during faulting the interplay between folding and faulting in the footwall reflects a component of shortening perpendicular to fold axial surfaces during extension parallel to fold axes this strain pattern can develop in regions with a transcurrent component or during lateral extrusion and does not necessarily require overall crustal thinning

paleogeographic reconstruction of the death valley extended region evidence from miocene large rock avalanche deposits in the amargosa chaos basin california large rock avalanche deposits are extremely useful tools in paleogeographic and tectonic reconstructions these deposits are large 0 1 km3 semicoherent snapshots of source area that were emplaced instantaneously in a sedimentary basin a rock avalanche deposit with a known age in a sedimentary basin requires the restoration of that basin to a position adjacent to the rock avalanche source area at the time of emplacement the miocene sedimentary section of the amargosa chaos and sperry hills basins in the southern death valley region contains deposits of large rock avalanches from both spatially and temporally separated source terranes the rock avalanche deposits in the amargosa chaos basin require the restoration of the basin to within 10 km of the kingston range prior to 7 8 ma west derived alluvial fan sediments in this basin can be confidently tied to the southern panamint mountains with early east derived alluvial fan sediments pre 7 8 ma tied to the kingston range moreover the pre 7 8 ma stratigraphy of the amargosa chaos basin is equivalent to the pre 7 8 ma stratigraphy of the miocene sedimentary section in the sperry hills prior to 7 8 ma the amargosa chaos and sperry hills basins were both parts of a larger sedimentary basin sedimentologic constraints on the geometry of the amargosa chaos basin indicate that throughout its history it was a half graben opening along a west dipping normal fault with substantial vertical relief in the uplifted footwall evidence for this topography exists in the form of multiple large rock avalanche deposits derived from footwall bedrock the axis of this basin trends northwest with the active basin bounding normal fault on the northeast margin at 7 8 ma the extension direction in the southern death valley region changed from southwest to northwest younger sediments including three younger rock avalanche deposits record the motion of the amargosa chaos basin away from the sperry hills basin top to the northwest displacement of 30 km along the amargosa detachment system is required between 7 8 ma and 4 9 ma between the sperry hills basin and the location of amargosa chaos basin in the southern black mountains continued post 4 9 ma northwest directed extension is required between the amargosa chaos basin and the southern panamint mountains in addition 15 km of right lateral slip on the southern portion of the grand view fault is required from 7 8 to 3 ma to move the sperry hills basin away from its pre 7 8 ma position adjacent to the kingston range

rise and tilt of metamorphic rocks in the lower plate of a detachment fault in the funeral mountains death valley california the funeral mountains in eastern california preserve a record of early cretaceous metamorphism followed by ductile deformation uplift and low angle normal detachment faulting 40ar 39ar age spectra indicate that cooling and uplift of the lower plate began in cretaceous time uplift was accommodated by normal sense movement along a wide northwest dipping shear zone mylonitic fabrics some of which have been dated as late cretaceous deformed older high temperature metamorphic textures analyses of shear bands mica fish and porphyroclasts grain shape fabrics and folds indicate that the upper surfaces moved toward 299 12 top to the northwest relative to lower surfaces uplift continued until the near present the youngest phase being accommodated by top to the northwest movement along the detachment fault which formed subparallel to lower plate mylonitic fabrics fission track apatite data indicate that exposure of the lower plate to the surface occurred sometime after 6 ma reconstruction along the movement vector places the grapevine mountains over the funeral mountains having been displaced at least 40 km isograds and thermobarometry in pelitic schist from the lower plate indicate increasing pressures and temperatures of equilibration toward the northwest the maximum temperature and pressure was determined on a sample from monarch canyon using thermobarometry 700 c at a depth of 32 km at chloride cliff 5 km southeast of monarch canyon 4 samples yielded 575 600 c at depths of 19 27 km at indian pass 17 km southeast of monarch canyon a temperature of 490 c was determined in the southern funeral mountains about 50 km southeast of monarch canyon conodont color alteration indexes indicate temperatures of 325 425 c these data indicate that the lower plate is presently tilted strongly to the southeast from the orientation it maintained at the peak of metamorphism thermochronologic data k ar on muscovite biotite and hornblende 40ar 39ar on hornblende and fission track on apatite titanite and zircon indicate that both tilting and the transition from ductile to brittle styles of quartz deformation are confined to the interval 21 6 ma during the latter part of this interval 11 6 ma rapid uplift and movement along the detachment fault are documented the findings support current theories of detachment fault evolution in which a dipping fault surface undergoes rotation to a subhorizontal orientation while the lower plate undergoes a comparable tilt

mesozoic and cenozoic extension recorded by metamorphic rocks in the funeral mountains california the funeral mountains metamorphic core complex like so many of these complexes in the north american cordillera contains early ductile structures related to mesozoic compressional tectonics that have been overprinted by structures related to later extension the core bounding detachment system formed in late miocene time and ductile extensional fabrics in its footwall have been viewed as evidence of a higher temperature stage in the same event integrated structural analysis and geochronology however indicate that ductile fabrics with a transport direction similar to the northwest direction of movement on the detachment are part of an older extensional event of late cretaceous age this event produced mylonitic fabrics a dominant foliation and well developed mineral and stretching lineations mesoscopic folds and a widespread crenulation lineation that developed during a late stage in this event also are consistent with northwest directed shear late cretaceous mylonitic fabrics are related to extensional shear zones within the core complex that have small stratigraphic offsets but may represent significant structural and metamorphic discontinuities rocks in the footwall of the shear zones experienced mid crustal depths that cannot be explained by the overburden available if the funeral mountains core rocks represent an intact block of mesozoic crust instead it appears that a significant section of mid crustal material may have been excised in late cretaceous time by the combined monarch canyon and chloride cliff shear zones as the result of gravitational instability of an overthickened crust in our interpretation this early extension was made possible by a waning of compression within the mesozoic thrust belt combined with a high regional heat flow due to the sierran arc this early extension took place 50 m y before development of the core bounding detachment system movement on which took place at low enough temperatures that deformation was predominantly brittle with some calc mylonite fabric development the youngest structures in the core are normal faults that cut the detachment and indicate a southwest transport direction orthogonal to those of both the earlier extensional events

comment and reply on isopach pattern of the lower cambrian zabriskie quartzite death valley region california nevada how useful in tectonic reconstructions comment

basement involved thrust faulting in a thin skinned fold and thrust belt death valley california usa although dominated by a strong late tertiary extensional overprint the turtlebacks of the black mountains of death valley display evidence for earlier possibly laramide age basement involved thrust faulting the thrust faults consist of now highly deformed contacts in which 200 m thick bodies of basement gneiss structurally overlie upper proterozoic metasedimentary rock in addition the faults contain locally preserved east directed mylonitic fabrics in their footwalls that are demonstrably early tertiary or older the association of these fabrics with laramide age pegmatite suggests that they may have formed concurrently with the intrusions these basement thrust faults are significant because they formed in a region long considered to have exclusively thin skinned deformation their presence also places new constraints on this part of the fold and thrust belt s preextension geometry by limiting the amount of late tertiary extension specifically these faults disallow the correlation of thin skinned structures that currently exist to the east and west of the black mountains

measurement of interseismic strain across the haiyuan fault gansu china by insar the haiyuan fault is part of a major left lateral fault system at the northeastern edge of the tibet qinghai plateau two m8 earthquakes 1920 and 1927 occurred along the fault bracketing an unbroken section of the fault identified as the tianzhu seismic gap we use interferometric synthetic aperture radar data from descending orbits of the ers satellites acquired between 1993 and 1998 along two adjacent tracks covering the gap to measure the current surface movements and better understand the present day mechanical behavior of this fault section the analysis of the radar data involves first the combined correction of orbital errors and errors associated with the phase delay through the troposphere a subset of the data is then selected based on the analysis of the residual noise spectra for each pair of data the selected interferograms are stacked and the average phase change rate is converted in fault parallel velocity assuming that the ground movement is horizontal and parallel to the fault velocity maps from both tracks show a zone of high velocity gradient across the fault a few kilometers wide consistent with left lateral slip on the haiyuan fault the average velocity field from the two tracks in their overlapping area is well fit with a single screw dislocation model in an elastic half space the derived fault slip rate at depth 4 2 8 mm yr is consistent with recent gps results the corresponding shallow apparent locking depth 0 4 2 km can be explained by a current low stress accumulation on the fault due to creep almost on the entire fault plane however unless it is transient this creep would be paradoxical with the occurrence of past large earthquakes along this fault section as revealed by paleoseismology an alternative model implying both shallow creep in the brittle upper crust and deep aseismic slip beneath the seismogenic layer separated by a locked section would be consistent with insar observations and with the potential for large earthquakes on the fault as well a two dislocation model with slip at 5 mm yr beneath 15 km and a transient creep rate of 11 mm yr between 2 and 7 km fits the insar data however the width and creep rate of the shallow creeping zone and their possible along strike variations are still poorly resolved with the present data set

teleseismic search for slow precursors to large earthquakes some large earthquakes display low frequency seismic anomalies that are best explained by episodes of slow smooth deformation immediately before their high frequency origin times analysis of the low frequency spectra of 107 shallow focus earthquakes revealed 20 events that had slow precursors 95 percent confidence level 19 were slow earthquakes associated with the ocean ridge transform system and 1 was a slow earthquake on an intracontinental transform fault in the east african rift system these anomalous earthquakes appear to be compound events each comprising one or more ordinary fast ruptures in the shallow seismogenic zone initiated by a precursory slow event in the adjacent or subjacent lithosphere

structure and regional significance of the late permian sierra nevada death valley thrust system east central california abstract an imbricate system of north trending east directed thrust faults of late early permian to middle early triassic most likely late permian age forms a belt in east central california extending from the mount morrison roof pendant in the eastern sierra nevada to death valley six major thrust faults typically with a spacing of 15 20 km original dips probably of 25 35 and stratigraphic throws of 2 5 km compose this structural belt which we call the sierra nevada death valley thrust system these thrusts presumably merge into a decollement at depth perhaps at the contact with crystalline basement the position of which is unknown we interpret the deformation that produced these thrusts to have been related to the initiation of convergent plate motion along a southeast trending continental margin segment probably formed by pennsylvanian transform truncation this deformation apparently represents a period of tectonic transition to full scale convergence and arc magmatism along the continental margin beginning in the late triassic in central california

cosmogenic 10be and 36cl geochronology of offset alluvial fans along the northern death valley fault zone implications for transient strain in the eastern california shear zone the northern death valley fault zone ndvfz has long been recognized as a major right lateral strike slip fault in the eastern california shear zone ecsz however its geologic slip rate has been difficult to determine using high resolution digital topographic imagery and terrestrial cosmogenic nuclide dating we present the first geochronologically determined slip rate for the ndvfz our study focuses on the red wall canyon alluvial fan which exposes clean dextral offsets of seven channels analysis of airborne laser swath mapping data indicates 297 9 m of right lateral displacement on the fault system since the late pleistocene in situ terrestrial cosmogenic 10 be and 36 cl geochronology was used to date the red wall canyon fan and a second correlative fan also cut by the fault beryllium 10 dates from large cobbles and boulders provide a maximum age of 70 22 20 ka for the offset landforms the minimum age of the alluvial fan deposits based on 36 cl depth profiles is 63 8 ka combining the offset measurement with the cosmogenic 10 be date yields a geologic fault slip rate of 4 2 1 9 1 1 mm yr 1 whereas the 36 cl data indicate 4 7 0 9 0 6 mm yr 1 of slip summing these slip rates with known rates on the owens valley hunter mountain and stateline faults at similar latitudes suggests a total geologic slip rate across the northern ecsz of 8 5 to 10 mm yr 1 this rate is commensurate with the overall geodetic rate and implies that the apparent discrepancy between geologic and geodetic data observed in the mojave section of the ecsz does not extend north of the garlock fault although the overall geodetic rates are similar the best estimates based on geology predict higher strain rates in the eastern part of the ecsz than to the west whereas the observed geodetic strain is relatively constant

assessing vertical axis rotations in large magnitude extensional settings a transect across the death valley extended terrane california models for neogene crustal deformation in the central death valley extended terrane southeastern california differ markedly in their estimates of upper crustal extension versus shear translations documentation of vertical axis rotations of range scale crustal blocks or parts thereof is critical when attempting to reconstruct this highly extended region to better define the magnitude aerial extent and timing of vertical axis rotation that could mark shear translation of the crust in this area paleomagnetic data were obtained from tertiary igneous and remagnetized paleozoic carbonate rocks along a roughly east west traverse parallel to about 36 n latitude sites were established in 7 to 5 ma volcanic sequences greenwater canyon and brown s peak and the 10 ma chocolate sundae mountain granite in the greenwater range 8 5 to 7 5 ma and 5 to 4 ma basalts on the east flank of the black mountains the 10 6 ma little chief stock and upper miocene basalts in the eastern panamint mountains and paleozoic pogonip group carbonate strata in the north central panamint mountains at the site level most materials yield readily interpretable paleomagnetic data group mean directions after appropriate structural corrections suggest no major vertical axis rotation of the greenwater range e g d 359 i 46 95 8 0 n 12 7 normal n 5 reversed r polarity sites little post 5 ma rotation of the eastern black mountains e g d 006 i 61 95 4 0 n 9 n 6 r sites and no significant post 10 ma rotation of the panamint range e g d 181 i 51 95 6 5 n 9 r sites in situ data from the greenwater canyon volcanic rocks chocolate sundae mountain granite funeral peak basalt rocks the little chief stock and paleozoic carbonate rocks remagnetized are consistent with moderate south east side down tilting of the separate range blocks during northwest directed extension the paleomagnetic data reported here suggest that the panamints shared none of the 7 ma to recent clockwise rotation of the black mountains crystalline core as proposed in recent models for transtensional development of the central death valley extended terrane

comment and reply on isopach pattern of the lower cambrian zabriskie quartzite death valley region california nevada how useful in tectonic reconstructions

the black mountains turtlebacks rosetta stones of death valley tectonics the black mountains turtlebacks expose mid crustal rock along the western front of the black mountains as such they provide keys to understanding the tertiary structural evolution of death valley and because of the outstanding rock exposure they also provide valuable natural laboratories for observing structural processes there are three turtlebacks the badwater turtleback in the north the copper canyon turtleback and the mormon point turtleback in the south although important differences exist among them each turtleback displays a doubly plunging antiformal core of metamorphic and igneous rock and a brittle fault contact to the northwest that is structurally overlain by miocene pleistocene volcanic and or sedimentary rock the turtleback cores contain mylonitic rocks that record an early period of top southeastward directed shear followed by top northwestward directed shear the earlier formed mylonites are cut by and locally appear concurrent with 55 61 ma pegmatite we interpret these fabrics as related to large scale basement involved thrust faults at the turtlebacks now preserved as areally extensive metamorphosed basement over younger cover contacts the younger and far more pervasive mylonites record late tertiary extensional unroofing of the turtleback footwalls from mid crustal depths available geochronology suggests that they cooled through 300 8c at different times 13 ma at badwater 6 ma at copper canyon 8 ma at mormon point at mormon point and copper canyon turtlebacks these dates record cooling of the metamorphic assemblages from beneath the floor of an 11 ma tertiary plutonic complex collectively these relationships suggest that the turtlebacks record initiation of ductile extension before 14 ma followed by injection of a large plutonic complex along the ductile shear zone ductile deformation continued during extensional uplift until the rocks cooled below temperatures for crystal plastic deformation by 6 8 ma subsequent low angle brittle fault slip led to final exposure of the igneous and metamorphic complex the turtleback shear zones can constrain models for crustal extension from map view as well as cross sectional perspectives in map view the presence of basement involved thrust faults in the turtlebacks suggest the black mountains were a basement

permian triassic plutonism and tectonics death valley region california and nevada significant contractional structures that deform permian rocks but predate an early triassic overlap sequence are recognized within the cordilleran orogen western united states thrusting in the death valley region of the orogen however has been regarded as middle triassic or younger and thus kinematically distinct we present new isotopic age limits on two posttectonic stocks that intrude major structures of the death valley thrust belt the stocks are no younger than middle triassic but are likely late permian in age consistent with stratigraphic and structural data suggesting that thrusting predates the overlap sequence we hypothesize that permian shortening may have affected more than 700 km of the cordilleran orogen at the same time arc activity began within cratonic north america but prior to early triassic emplacement of the structurally higher sonomian arc terrane

active displacement transfer and differential block motion within the central walker lane western great basin velocities determined for 50 global positioning system sites within the central walker lane indicate differential motion among tectonic blocks forming a boundary zone between the great basin extensional province and the sierra nevada the velocity field is related to displacement transfer from the owens valley and furnace creek fault systems of east ern california to transtensional structures of the walker lane and extensional faults of the central nevada seismic belt block boundaries are sharp and appear to be inherited from pre tertiary crustal structure the block geometries exert strong influence on dif ferential displacements concentrated along boundaries as belts of divergent transcurrent and convergent motion the aggregate velocity accounts for about 25 of the relative motion between the pacific and north american plates about 5 mm yr of the motion is localized along the eastern margin of the sierra nevada whereas about 10 mm yr is stepped 100 km east along a belt of east northeast trending transtensional faults that merge with northwest trending transcurrent structures of the walker lane about 6 mm yr of the velocity field is transferred to north northeast trending extensional faults of the central nevada seismic belt the heterogeneous distribution of motions is consistent with partitioning of a regional velocity field formed by westward extension and n408w directed shear

extensional tectonics in the death valley area california transport of the panamint range structural block 80 km northwestward in the hypothesis presented here the panamint range is a structural block that was detached during late cenozoic time from underlying rocks that now form the black mountains and was transported tectonically an estimated 80 km to the northwest transport occurred along a single low angle westward dipping detachment fault or perhaps along a system of such faults the estimate of 80 km of transport distance is based on the apparent right lateral offset of late precambrian and paleozoic facies and thickness trends along the furnace creek fault zone that bounds the detached block on the northeast the death valley turtleback surfaces are considered to be gigantic mullions related to the detachment surface

u th pb rb sr and ar ar mineral and whole rock isotopic systematics in a metamorphosed granitic terrane southeastern california mesozoic structural domes are developed in an older proterozoic crystalline basement of granitic to granodioritic foliate metaplutonic rocks in the halloran hills southeastern california isotopic analyses of whole rocks and mineral separates from these rocks by u th pb rb sr and ar ar techniques yield a complex pattern of discordance that is the result of a fairly simple geologic history individual mineral isotopic systems have variably equilibrated with each other in response to mesozoic regional metamorphism and locally to later heating during mesozoic batholith emplacement discordant u th pb zircon data indicate that the granitic core rocks are 1 710 ma and that one dioritic phase may be slightly older rb sr whole rock model dates scatter about 1 700 ma rb sr amphibole whole rock and u th pb amphibole dates are also proterozoic potassium feldspars retain a 207 pb 206 pb signature of their proterozoic age ar ar amphibole spectra from the flank of the main dome reveal disturbed dates of 1 450 ma to 1 100 ma and the dates become younger toward the structurally deeper core of the dome all remaining isotopic determinations yield mesozoic or younger dates for mineral whole rock systems rb sr whole rock apatite feldspar biotite analyses show nonequilibration of strontium isotopes with resultant mineral pair dates from 4 foliate plutonic rocks ranging from 200 to 50 ma no single metamorphic age is indicated by the rb sr data rb sr whole rock biotite dates are consistently younger than any other determinations and may be reduced by weathering or gain of nonradiogenic strontium from ground water u pb sphene and apatite analyses from rocks that yield 1 710 ma zircon dates are nearly concordant at 140 ma an amphibole from the structurally deepest rocks of the main dome that yield 140 to 150 ma u pb sphene dates has an ar ar plateau date of 144 ma the u pb sphene and ar ar amphibole analyses are believed to be the best age estimate for the end of the highest temperature phase of regional metamorphism th pb sphene and apatite dates and ar ar biotite dates cluster at 90 5 ma as a consequence of regional cooling during late cretaceous time following extensive mesozoic plutonism in the region at 97 to 90 ma we interpret the discordant mineral date patterns to have resulted from metamorphism of 1 700 ma plutonic rocks during the jurassic 140 50 ma and subsequent uplift and cooling to 200 c at about 90 ma on the basis of this study the isotope dating systems ranked in decreasing order of resistance to resetting are u th pb zircon concordia intercept rb sr whole rock rb sr amphibole u th pb amphibole pb pb whole rock ar ar amphibole rb sr sphene u pb sphene and apatite rb sr plagioclase potassium feldspar apatite th pb sphene and apatite ar ar biotite u pb feldspars rb sr biotite

quantifying dextral shear on the bristol granite mountains fault zone successful geologic prediction from kinematic compatibility of the eastern california shear zone abstractfor regional kinematic compatibility to be a valid boundary condition for continental tectonic reconstructions there must be tests that validate or invalidate kinematic model predictions in several reconstructions of western north america the displacement history of the mojave block continues to be unresolved the magnitude of displacement along the bristol granite mountains fault zone bgmfz which is the eastern margin of the eastern california shear zone ecsz in the mojave block is a key example of a long standing kinematic prediction that has defied a positive field test until now the ecsz is a network of late neogene and quaternary right lateral strike slip faults that extend from the gulf of california north through the mojave desert linking pacific north america plate motion with basin and range extension this network of faults accounts for 15 of post 16 ma plate transform motion geologic estimates of net dextral offset along the mojave portion of the ecsz 53 6 km are appro

structural geology of the montgomery mountains and the northern half of the nopah and resting spring ranges nevada and california more than 7 500 m of upper precambrian and paleozoic sedimentary rocks in the area of the montgomery mountains and the northern half of the nopah and resting spring ranges represent a typical cordilleran miogeosynclinal sequence during mesozoic time after a period of earlier mesozoic folding and high angle faulting these rocks were cut by thrust faults that divided the rock sequence into four structural units in the resting spring range and the montgomery mountains from the top down the units are 1 the montgomery thrust plate 2 the baxter thrust plate 3 the resting spring thrust plate and 4 the amargosa unit beneath the montgomery thrust fault in the montgomery mountains lies the six mile thrust plate which has limited extent but may be a major subunit of the baxter plate the montgomery thrust plate moved eastward along a single thrust but the resting spring thrust plate moved eastward along an anastomosing series of thrust faults which divided it into a series of lobes thrust faults in the resting spring range now dip east because cenozoic tilting has reversed their original subhorizontal or west dips in the nopah range there are three major structural units which are from the top down 1 the chicago pass thrust plate 2 the shaw thrust plate and 3 the nopah range unit structural units in the nopah range cannot be unequivocally correlated with those in the resting spring range and montgomery mountains and two hypotheses must be presented for correlation hypothesis 1 correlates the baxter thrust plate of the resting spring range with the shaw thrust plate of the nopah range and hypothesis 2 correlates the baxter thrust plate with the chicago pass thrust plate of the nopah range post thrusting structures are related to progressive west or northwest extension cenozoic folds around the north end of stewart valley are oblique and related to right slip on the northwest striking stewart valley fault these may be the oldest post thrusting structural features in the area right slip and high angle dip slip faults are probably contemporaneous forming ranges and valleys by pull aparts continued extension caused rotation of earlier high angle dip slip faults so that some of them are now subhorizontal some low angle faults are probably gravity slides and form gradations into more chaotic landslides

spatial variability in the structure of the roberts mountains allochthon western nevada structural variability in rocks of the upper plate of the roberts mountains thrust indicates a complex history of thrust emplacement during the mid paleozoic antler orogeny the roberts mountains allochthon consists predominantly of a highly deformed assemblage of structurally imbricated lower continental slope and continental rise sedimentary and volcanic rocks of early paleozoic age it has been interpreted variously as a back arc thrust and as a grounded accretionary prism that overrode the upper precambrian and lower paleozoic passive margin of western north america current understanding of structural and stratigraphic relations supports the second interpretation the trace of the roberts mountains thrust trends south southwesterly across nevada from near the idaho border to the vicinity of tonopah 38 n lat where it is interpreted to swing westerly and extend to the sierra nevada subparallel to the thrust trace is the trend of the western boundary of the late precambrian passive continental margin as deduced from lower paleozoic facies patterns and the 87sr 86sr 0 706 line the westerly deflection of these and younger trends has been attributed by some workers to crustal deformation of late mesozoic and or cenozoic age and by others to an original bend in the continental margin results presented here support the latter interpretation structures in the northern and central segments of the roberts mountains thrust characterized by south southwest trace consist of a single phase of folds and indicate easterly transport the inferred southern segment of the thrust with a westerly trend exhibits two and locally three phases of folds interpreted as being genetically related to emplacement of the thrust first phase folds in the south are correlated with folds in the central and northern segments of the thrust and after the effects of superimposed structures are geometrically removed also yield an easterly transport direction cross folds in the southern part of the allochthon and their absence to the north indicate different structural histories for the regions structures in the allochthon are interpreted as having developed during the formation of an accretionary prism differences in structural history are related to differential rates of slip on the allochthon s basal thrust during transport and emplacement development of cross folds in the south is thought to be due to a local reduction in the rate of displacement and corresponding internal shortening of the upper plate rocks caused by resistance to subduction of a west facing promontory of continental crust

a new hypothesis for the amount and distribution of dextral displacement along the fish lake valley northern death valley furnace creek fault zone california nevada 1 the fish lake valley northern death valley furnace creek fault zone a 250 km long predominantly right lateral structure in california and nevada is a key element in tectonic reconstructions of the death valley area eastern california shear zone and walker lane and central basin and range province total displacement on the fault zone is contested however with estimates ranging from 30 to 63 km or more here we present a new synthesis of available constraints preextensional thrust faults folds and igneous rocks indicate that offset reaches a maximum of 50 km neogene rocks constrain its partitioning over time most offset is interpreted as 13 10 ma accruing at 3 5 mm yr in the middle of the fault zone and more slowly toward the tips the offset markers imply 68 14 km of translation between the cottonwood mountains and resting spring nopah range 60 14 km since 15 ma through a combination of strike slip and crustal extension this suggests that a previous interpretation of 104 7 km based on the middle miocene eagle mountain formation is an overestimate by 50 our results also help to mitigate a discrepancy in the 12 0 ma strain budget for the eastern california shear zone displacement has previously been estimated at 100 10 km and 67 6 km for the basin and range and mojave portions of the shear zone respectively our new estimate of 74 17 km for the basin and range is within the uncertainty of the mojave estimate

slip styles in a spring slider model with a laboratory derived constitutive law for serpentinite a spring slider model with a laboratory derived constitutive law for serpentinite generates seismic slip aseismic slip or a combination of both such behavior is observed on oceanic ridge transform systems and portions of the san andreas fault and may be due to the presence of serpentinite the constitutive law combines two sets of equations a rate dependent flow equation which dominates at low velocities and a rate and state dependent set of equations which dominate at high velocities the combined model produces transient behavior with maximum slip velocities well in excess of the loading velocity metastable slip prior to the onset of high speed slip is produced in many simulations and may be analogous to the slow precursors observed for some oceanic ridge transform earthquakes this precursory slip results from the double valued nature of the steady state curve of the two mechanism model in which the state variable equations are rate weakening

earthquake scaling relations for mid ocean ridge transform faults 1 a mid ocean ridge transform fault rtf of length l slip rate v and moment release rate can be characterized by a seismic coupling coefficient ae at where ae v is an effective seismic area and at l3 2v 1 2 is the area above an isotherm tref a global set of 65 rtfs with a combined length of 16 410 km is well described by a linear scaling relation 1 ae at which yields 0 15 0 05 for tref 600 c therefore about 85 of the slip above the 600 c isotherm must be accommodated by subseismic mechanisms and this slip partitioning does not depend systematically on either v or l rtf seismicity can be fit by a truncated gutenberg richter distribution with a slope 2 3 in which the cumulative number of events n0 and the upper cutoff moment mc dcac depend on at data for the largest events are consistent with a self similar slip scaling dc ac1 2 and a square root areal scaling 2 ac at1 2 if relations 1 and 2 apply then moment balance requires that the dimensionless seismic productivity 0 0 atv should scale as 0 at 1 4 which we confirm using small events hence the frequencies of both small and large earthquakes adjust with at to maintain constant coupling rtf scaling relations appear to violate the single mode hypothesis which states that a fault patch is either fully seismic or fully aseismic and thus implies ac ae the heterogeneities in the stress distribution and fault structure responsible for relation 2 may arise from a thermally regulated dynamic balance between the growth and coalescence of fault segments within a rapidly evolving fault zone

large magnitude permian shortening and continental margin tectonics in the southern cordillera discussion and reply stone and stevens agree that apparent termination of large displacement on the last chance thrust near the darwin plateau is a major problem to be explained by any viable model of cordilleran geology their arguments against a permian age for thrusting however are deeply flawed the alternative structural relations they advocate in the darwin plateau southern inyo mountains and northern death valley areas result in a thrust belt that is not strain compatible that is retrodeformable to its original state without gaps or overlaps in the reconstruction

cenozoic tectonic evolution of the white mountains california and nevada the white mountains represent the westernmost range of the central northern basin and range province they are situated to the east of the unextended sierra nevada and represent a crustal block that is bounded along its western flank by the high angle white mountains fault zone the fault zone accommodates up to 8 km of total dip slip displacement investigation of the structural and thermal history of the white mountains indicates a two stage cenozoic tectonic evolution preextensional miocene volcanic rocks preserved along the eastern side of the range unconformably overlie mesozoic granitic basement and currently dip up to 25 to the east recording the total cenozoic tilt of the crustal block apatite fission track and u th he thermochronological data indicate that the white mountains underwent rapid exhumation and eastward tilting in the middle miocene starting at ca 12 ma geologic mapping 1 10 000 fault kinematic analysis and dating of younger volcanic sequences show that following middle miocene east west extension the white mountains have been dominated by right lateral transtensional deformation related to the walker lane belt the eruption of late miocene and pliocene volcanic sequences in the eastern white mountains postdates the majority of the uplift of the range as evidenced by infilling of paleodrainages and the presence of east directed flow fabrics fault kinematic indicators from the white mountains fault zone are characterized by apparent overprinting of dip slip fault motion indicators by right lateral slickenfibers and fault striations demonstrating that the range bounding fault system along the western side of the white mountains was reactivated as a dextral strike slip fault system at the northern and southern ends of the range pliocene right lateral transtension along this northwest southeast trending fault systems resulted in the formation of northeast trending pull apart basins that truncate the mountain range and transfer strike slip displacement eastward from the owens valley fault zone to the fish lake valley fault zone the inception of strike slip faulting in fish lake valley occurred at ca 6 ma as constrained by late miocene volcanic units right lateral faulting on the western side of the white mountains occurred at ca 3 ma and is distinctly younger than the faulting in the fish lake valley area indicating a westward migration of transcurrent deformation through time

frictional behavior of oceanic transform faults and its influence on earthquake characteristics 1 we use a three dimensional strike slip fault model in the framework of rate and state dependent friction to investigate earthquake behavior and scaling relations on oceanic transform faults otfs gabbro friction data under hydrothermal conditions are mapped onto otfs using temperatures from 1 a half space cooling model and 2 a thermal model that incorporates a visco plastic rheology non newtonian viscous flow and the effects of shear heating and hydrothermal circulation without introducing small scale frictional heterogeneities on the fault our model predicts that an otf segment can transition between seismic and aseismic slip over many earthquake cycles consistent with the multimode hypothesis for otf ruptures the average seismic coupling coefficient c is strongly dependent on the ratio of seismogenic zone width w to earthquake nucleation size h c increases by four orders of magnitude as w h increases from 1 to 2 specifically the average c 0 15 0 05 derived from global otf earthquake catalogs can be reached at w h 1 2 1 7 further in all simulations the area of the largest earthquake rupture is less than the total seismogenic area and we predict a deficiency of large earthquakes on long transforms which is also consistent with observations to match these observations over this narrow range of w h requires an increase in the characteristic slip distance dc as the seismogenic zone becomes wider and normal stress is higher on long transforms earthquake magnitude and distribution on the gofar and romanche transforms are better predicted by simulations using the visco plastic model than the half space cooling model

afterslip and aftershocks in the rate and state friction law istituto nazionale di geofisica e vulcanologia italy ingv centre national de la recherche scientifique cnrs exxonmobil upstream research company

early tertiary magmatism and probable mesozoic fabrics in the black mountains death valley california we report two early tertiary u pb zircon ages for pegmatite from the black mountains of death valley california these ages 54 7 0 6 ma and 56 3 ma are unique for much of southeastern california the samples belong to a pegmatite suite that occupies part of the footwall of the badwater turtleback a late tertiary extensional feature similar but undated pegmatite intrudes the footwalls of the copper canyon and mormon point turtlebacks farther south the pegmatite suite demonstrates that fabric development on the turtlebacks was at least a two stage process fabrics cut by these pegmatites likely formed during the mesozoic whereas those that involve them formed during late tertiary extension

interpretation and tectonic implications of cooling histories an example from the black mountains death valley extended terrane california abstract in the death valley extended terrane of california the black mountains have long been considered unique because they largely lack the miogeoclinal cover rocks characteristic of the surrounding ranges fission track ages presented here are combined with published40ar 39ar ages and used to construct cooling path envelopes for samples of precambrian crystalline basement and miocene plutonic rocks collected across the entire range the cooling history reconstructions are used to differentiate between contrasting miocene unroofing histories proposed for this range apatite and zircon fission track ages from the southeastern portion of the range suggest unroofing occurred there at 13 8 5 ma from temperatures well below 300 c cooling age data from the central black mountains indicate major unroofing at 8 5 6 0 ma from temperatures greater than 300 c old cooling ages from directly beneath the highly extended amargosa chaos rocks are consistent with the chaos rocks being part of an allochthonous slice that was tectonically transported from high crustal levels onto deeper crustal levels scenarios for the miocene unroofing history of this range rely heavily on interpretations of the depth of emplacement of miocene plutons in the core of the range thermochronologic and geobarometric data and thermal modeling of intrusion cooling suggest emplacement of an 11 6 ma pluton into the crystalline core at a depth of 10 15 km both the cooling age data and considerations of the local geology seem to preclude an unroofing history dominated by erosion of the overlying miogeoclinal section the morphology of the cooling path envelopes constructed here are similar to those constructed for detachment fault terranes the data are most consistent with unroofing involving tectonic denudation 10 15 km along a single westerly dipping detachment zone diachronous rapid cooling from southeast to northwest within the range is interpreted as a result of the lower plate undergoing flexural deformation as it pulls out from underneath a relatively rigid scoop shaped hanging wall block the rolling hinge model migration of unroofing and tilting within the range mimics the overall east to west sequential tilting and unroofing of range blocks in the death valley extended terrane similar thermochronologic evidence for sequential range scale tilting has been obtained from the lake mead extended region suggesting that this style of extension might provide an explanation for strongly extended domains in the basin and range province

thermal and barometric constraints on the intrusive and unroofing history of the black mountains implications for timing initial dip and kinematics of detachment faulting in the death valley region california unroofing of the black mountains death valley california has resulted in the exposure of 1 7 ga crystalline basement late precambrian amphibolite facies metasedimentary rocks and a tertiary magmatic complex the 40ar 39ar cooling ages obtained from samples collected across the entire length of the range 55 km combined with geobarometric results from synextensional intrusions provide time depth constraints on the miocene intrusive history and extensional unroofing of the black mountains data from the southeastern black mountains and adjacent greenwater range suggest unroofing from shallow depths between 9 and 10 ma to the northwest in the crystalline core of the range biotite plateau ages from 13 to 6 8 ma from rocks making up the death valley turtlebacks indicate a midcrustal residence with temperatures 300 c prior to extensional unroofing biotite 40ar 39ar ages from both precambrian basement and tertiary plutons reveal a diachronous cooling pattern of decreasing ages toward the northwest subparallel to the regional extension direction diachronous cooling was accompanied by dike intrusion which also decreases in age toward the northwest the cooling age pattern and geobarometric constraints in crystalline rocks of the black mountains suggest denudation of 10 15 km along a northwest directed detachment system consistent with regional reconstructions of tertiary extension and with unroofing of a northwest deepening crustal section mica cooling ages that deviate from the northwest younging trend are consistent with northwestward transport of rocks initially at shallower crustal levels onto deeper levels along splays of the detachment the well known amargosa chaos and perhaps the badwater turtleback are examples of this splaying process considering the current distance of the structurally deepest samples away from moderately to steeply east tilted tertiary strata in the southeastern black mountains these data indicate an average initial dip of the detachment system of the order of 20 similar to that determined for detachment faults in west central arizona and southeastern california beginning with an initially listric geometry a pattern of footwall unroofing accompanied by dike intrusion progresses northwestward this pattern may be explained by a model where migration of footwall flexures occur below a scoop shaped hanging wall block one consequence of this model is that gently dipping ductile fabrics developed in the middle crust steepen in the upper crust during unloading this process resolves the low initial dips obtained here with mapping which suggests transport of the upper plate on moderately to steeply dipping surfaces in the middle and upper crust

earthquake nucleation on faults with rate and state dependent strength abstract dieterich j h 1992 earthquake nucleation on faults with rate and state dependent strength in t mikumo k aki m ohnaka l j ruff and p k p spudich editors earthquake source physics and earthquake precursors tectonophysics 211 115 134 faults with rate and state dependent constitutive properties reproduce a range of observed fault slip phenomena including spontaneous nucleation of slip instabilities at stresses above some critical stress level and recovery of strength following slip instability calculations with a plane strain fault model with spatially varying properties demonstrate that accelerating slip precedes instability and becomes localized to a fault patch the dimensions of the fault patch follow scaling relations for the minimum critical length for unstable fault slip the critical length is a function of normal stress loading conditions and constitutive parameters which include dc the characteristic slip distance if slip starts on a patch that exceeds the critical size the length of the rapidly accelerating zone tends to shrink to the characteristic size as the time of instability approaches solutions have been obtained for a uniform fixed patch model that are in good agreement with results from the plane strain model over a wide range of conditions above the steady state stress the logarithm of the time to instability linearly decreases as the initial stress increases because nucleation patch length and premonitory displacement are proportional to dc the moment of premonitory slip scales by d3c the scaling of dc is currently an open question unless dc for earthquake faults is significantly greater than that observed on laboratory faults premonitory strain arising from the nucleation process for earthquakes may by too small to detect using current observation methods excluding the possibility that dc in the nucleation zone controls the magnitude of the subsequent earthquake then the source dimensions of the smallest earthquakes in a region provide an upper limit for the size of the nucleation patch

interseismic deformation and geologic evolution of the death valley fault zone 1 the death valley fault zone dvfz located in southeastern california is an active fault system with an evolved pull apart basin that has been deforming over the past 6 myr we present a study of the interseismic motion and long term stress accumulation rates to better understand the nature of both past and present day loading conditions of the dvfz using a 3 d semi analytic viscoelastic deformation model combined with geodetic velocities derived from the mobile array of gps for nevada transtension magnet network and the southern california earthquake center scec crustal motion map version 4 cmmv4 gps data we establish parameters for interseismic slip rate and apparent locking depth for four dvfz fault segments our preferred model provides good fit to the data 1 0 mm yr and 1 5 mm yr rms misfit in the fault perpendicular and fault parallel directions respectively and yields apparent locking depths between 9 8 17 1 km and strike slip rates of 3 7 mm yr for the segments we also determine subsidence 0 5 0 8 mm yr and extension 1 0 1 2 mm yr rates in the pull apart basin region with these parameters we construct a dvfz evolution model for the last 6 myr that recreates the motion of the fault blocks involved in the formation of the present day geological structures in death valley finally using coulomb stress accumulation rates derived from our model 0 25 0 49 mpa 100 yr combined with earthquake recurrence interval estimates of 500 to 2600 years we assess present day seismic hazards with calculated moment magnitudes ranging from 6 7 7 7

spatial variations in slip rate along the death valley fish lake valley fault system determined from lidar topographic data and cosmogenic 10be geochronology 1 the death valley fish lake valley fault zone dv flvfz is a prominent dextral fault system in the eastern california shear zone ecsz combining offset measurements determined with lidar topographic data for two alluvial fans with terrestrial cosmogenic nuclide 10be ages from the fan surfaces yields a late pleistocene slip rate of 2 5 to 3 mm yr for the northern part of the dv flvfz in fish lake valley these rates are slower than the late pleistocene rate determined for the system in northern death valley indicating that slip rates decrease northward along this major fault zone when summed with the slip rate from the white mountains fault the other major fault in this part of the ecsz our results suggest that either significant deformation is accommodated on structures east of fish lake valley or that rates of seismic strain accumulation and release have not remained constant over late pleistocene to holocene time

black mountains crustal section death valley extended terrain california recent reconstructions of cenozoic extension in the southern great basin juxtapose the panamint range above the black mountains and indicate major tectonic denudation of the black mountains during tertiary extension structural and geologic characteristics of the black mountains and consideration of the regional geology of surrounding ranges suggest that the black mountains block may represent a 10 to 30 km preextensional crustal section that has been uplifted along a major detachment zone geobarometry and ductile deformation features in a synrift intermediate to mafic batholith and metamorphism of eocambrian sedimentary rock on the western side of the range appear to support this hypothesis these data suggest that the black mountains block is one of the youngest and perhaps among the deepest exposed examples of cordilleran metamorphic core complexes

paleogeographic and structural significance of an upper mississippian facies boundary in southern nevada and east central california discussion and reply a major facies boundary separating meramecian lower upper mississippian shallow water carbonate platform rocks to the south east from coeval to slightly younger relatively deep water siliciclastic rocks to the northwest can be traced throughout southern nevada and east central california although the precise depositional relation between the two facies is not entirely clear the outer margin of the shallow water carbonate rocks almost certainly marks the edge of the carbonate platform in earliest late meramecian time this facies boundary is distinct and unambiguous enough that it and a parallel subfacies boundary within the carbonate platform rocks can be used to estimate amounts of displacement on cenozoic right slip faults in the region the carbonate siliciclastic facies boundary is offset by about 170 km in a right lateral sense parallel to the death valley furnace creek fault zone between the west side of that fault zone and the northeast side of the las vegas valley shear zone this offset is cenozoic in age and is interpreted to be distributed as follows 45 50 km on the las vegas valley shear zone 80 km on the death valley furnace creek fault zone 30 km on the stewart valley fault and an additional 10 15 km that is not specifically accounted for restoration of these offsets successfully reconstructs the meramecian carbonate shelf edge and aligns several thrust faults now exposed on opposite sides of the right slip faults

chapter 22 changing patterns of extensional tectonics overprinting of the basin of the middle and upper miocene esmeralda formation in western nevada by younger structural basins

a revised kinematic model for the relative motion between pacific oceanic plates and north america since the late cretaceous 1 the convergence between the pacific farallon and kula oceanic plates and the north american plate has provided a driving force for tectonic processes that have shaped the western margin of north america yet reconstructions of plate motion in the pacific basin have traditionally relied on the assumption of fixed hot spots in the last decade substantial cretaceous to paleogene motion between the pacific and atlantic hot spots has been recognized providing motivation to reevaluate the history of relative motion between pacific oceanic plates and north america by means of plate circuit reconstructions this paper presents new kinematic models based on two alternative plate circuits linking the pacific plate to north america since late cretaceous time when compared to models relying on fixity of pacific and indo atlantic hot spots our reconstructions suggest that the pacific kula and pacific farallon ridges were 600 1000 km closer to the western margin of north america and hence that the farallon and kula plates were smaller in late cretaceous to middle eocene time these findings cast significant doubt on the viability of a configuration of the farallon kula ridge that juxtaposes the kula plate with the southern part of the paleo north american margin during this time interval the results of our new reconstructions also suggest more oblique convergence between the farallon or kula plate and north america from the late cretaceous to the middle eocene related to the combination of dominantly northwest motion of the pacific plate and steady southwest motion of north america this provides an efficient mechanism for the coast parallel translation of some accreted terranes of north america it may also explain the structure of geological units in western north america such as the central belt of the franciscan complex which show a dominant coast parallel fabric formed during an interval coeval with the episode of oblique convergence

evidence for 65 km of dextral slip across owens valley california since 83 ma the golden bear dike in the sierra nevada and the coso dikes in the coso range crop out on opposite sides of owens valley california and strike roughly perpendicular to it neither dike reappears along strike across the valley new data demonstrate that the dike sets are ca 83 ma in age share nearly identical mineralogy and petrography and intrude similar wall rocks including distinctive 102 ma leucogranite dike bulk chemical and sr and nd isotope compositions are nearly indistinguishable these data suggest that the dike sets were originally continuous and were offset dextrally by 65 km this displacement estimate is consistent with other recent estimates of total slip across owens valley if faulting began during the pliocene the average slip rate was significantly faster than the current rate alternatively motion could have been episodic and have begun as early as the late cretaceous

petrologic constraints on the unroofing history of the funeral mountain metamorphic core complex california this is the published version copyright 1990 american geophysical union all rights reserved

tectonic subsidence of the early paleozoic passive continental margin in eastern california and southern nevada quantitative analysis of tectonic subsidence in cambrian and ordovician platform carbonates and associated strata exposed in the spring mountains nevada and the nopah funeral and inyo ranges california indicates that subsidence associated with this segment of the early paleozoic passive continental margin is exponential in form consistent with thermal contraction of the lithosphere following extension as in other parts of the north american cordillera continental separation in the southern great basin appears to have taken place between 590 and 545 ma these results are not sensitive to uncertainties in stratigraphic thickness biostratigraphic age control or paleobathymetry uncertainties in the cambrian time scale lead to predictable variations in the inferred time of onset of thermal subsidence but they have no effect on the inferred stratigraphic position of the rift to post rift transition a younger age for the base of the middle cambrian results in a younger inferred age of onset of thermal subsidence accompanied by greater rates of subsidence during the cambrian whereas a significantly older estimate of the onset of thermal subsidence can be obtained only if the base of the middle cambrian is substantially older than 540 ma a possibility that is inconsistent with available data results of the subsidence analysis are particularly significant because this is one of the few regions along the length of the north american cordillera where they can be compared directly to the geologic evidence for syn rift and post rift deposition basement involved faulting associated with the amargosa basin aulacogen ceased during deposition of the noonday dolomite which is thought to be older than 700 680 ma on the basis of stromatolites of late riphean affinity the overlying johnnie formation contains supposed vendian stromatolites younger than 700 680 ma if it is assumed that our results indicate the timing of the final rift to post rift transition then either the ages inferred from stromatolites are incorrect or the lithosphere was thinned regionally after deposition of the noonday the latter possibility is supported by limited geologic evidence for extension in latest proterozoic and early cambrian time the lack of appreciable physical evidence for crustal extension after deposition of the noonday however may imply that 1 a uniform extension model for lithospheric thinning is inappropriate for this part of the margin or that 2 some or all of the localities studied are continentward of the hinge zone and that the observed subsidence is exaggerated by flexural loading in a deeper basin to the west

thermochronologic evaluation of postcollision extension in the anatolide orogen western turkey 1 to better understand the driving mechanisms behind the transition from collision to extension in a convergent orogen data from multiple low temperature thermochronometers were obtained from the simav detachment fault sdf the earliest developed major extensional structure recognized in the western anatolide orogen of western turkey twenty two zircon fission track ft 26 apatite ft 12 apatite u th he ages and 26 apatite ft track length analyses are presented the data establish that the sdf was a major extensional fault active between 25 and 19 ma the coincidence in timing of magmatism with cessation of sdf activity implies the detachment became locked owing to doming induced by magma emplacement zircon ft ages away from the influence of miocene magmatism record rapid footwall cooling between 25 and 21 ma at a slip rate of up to 15 km myr and demonstrate that active ductile deformation along the sdf migrated northward with time apatite ft ages from the footwall of the sdf are spatially invariant over 100 km and consistently 2 3 myr younger than the zircon fission track ages from the same samples these data are consistent with a regional but relatively rapid erosion linked cooling phase that removed 2 3 km of overburden following cessation of sdf activity but before deposition of sedimentary rocks on the detachment surface at 16 4 ma postcollision extension of the anatolide orogen with development of the sdf can be best explained as the result of postcollision magmatism and thermal weakening of the crust inducing the extensional reactivation of an earlier major out of sequence thrust

covariance of structural and stratigraphic trends evidence for anticlockwise rotation within the walker lane belt death valley region california and nevada large magnitude relative rotations of range scale structural blocks are inferred to be products of crustal extension in the death valley region in california and nevada reconstructions of the extended terrain restore pre tertiary contractile structures with currently diverse trends into a relatively simple north northeast trending thrust belt we interpret trends of major contractile structures throughout the death valley region as characteristically discordant to and thus geometrically independent from stratigraphic trends we compare trends of pre tertiary contractile structures with paleoflow orientations in lower cambrian strata throughout the extended terrain significant differences between mean paleoflow orientations are consistent in magnitude and sense with differences observed in the structural trends available evidence does not support interpretation of paleoflow data from apparently rotated areas as representing an original paleogeography distinct from that of adjacent areas facies variations are present within the contractile structures we interpret the strong covariance throughout the study area between structural and paleoflow trends of diverse orientations as evidence for vertical axis rotations combined rotation estimates from these data indicate clockwise rotations of 85 12 for bare mountain and 73 24 for the striped hills but anticlockwise rotations of 30 35 and 87 29 respectively for the northern and southern grapevine mountains such large rotations of opposite sense may be related to north south shortening accommodated by conjugate strike slip faults during large magnitude extension in the death valley region but are difficult to explain as products of regional dextral shear within the southern walker lane belt

late cenozoic history and slip rates of the fish lake valley emigrant peak and deep springs fault zones nevada and california several well dated stratigraphic markers permit detailed assessment of the temporal and spatial variation in slip rates along the interconnected faults of the fish lake valley emigrant peak and deep springs fault zones in west central nevada and east central california right lateral motion on the fish lake valley fault zone apparently began ca 10 ma 11 9 8 2 ma associated extensional faulting probably began ca 5 ma 6 9 4 ma and resulted in the opening of fish lake valley and deep springs valley the long term lateral slip rate for the fish lake valley fault zone since about 10 ma is 5 mm yr 3 12 mm yr our preferred lateral slip rate for the central most active part of the fish lake valley fault zone decreased from about 6 to 3 mm yr from the late miocene to the early pleistocene increased to about 11 mm yr during the middle pleistocene and decreased to about 4 mm yr during the late pleistocene extension may account for some of the change in lateral slip rate during the pliocene the large increase in lateral slip rate during the middle pleistocene is circumstantially linked to an increase in vertical slip rates on the fish lake valley and deep springs fault zones at about the time of the eruption of the bishop ash 0 76 ma vertical slip rates along the three fault zones are also related to fault strike vertical rates are highest on north striking faults and approach zero on northwest striking faults the long lived slip history of the fish lake valley fault zone fits a tectonic model in which the death valley furnace creek fish lake valley fault system is integrated with right lateral shear on faults of the central walker lane and the eastern california shear zone to accommodate part of the pacific north american relative plate motion our research demonstrates that the fish lake valley fault zone accounts for about half the rate of 10 12 mm yr of pacific north american plate boundary shear accommodated within the basin and range province between about lat 37 and 38 n

the thermal springs of jordan the thermal springs alongside wadi araba dead sea and jordan valley jordan were investigated and sampled in a comprehensive field study of 2 weeks conventional physicochemical properties were measured in situ dissolved solids and isotopic composition were analyzed two main spring locations on the east side of the dead sea were mapped it became evident that the hottest springs are among the closest to prominent faults some springs are controlled by gas lift jordan s hot springs are described by means of a broad hydrochemical and physicochemical data set and several figures are presented based on their hydrochemistry the thermal springs are classified into four thermal provinces water genesis is discussed several geothermometers are applied to estimate reservoir temperatures observed discharge rate water temperature and isotopic composition are compared with data from the literature although discharge and water temperature are reported to be constant over the last decades groundwater overexploitation led to a shift of the isotopic composition what is documented for the first time in jordan thus the effect of groundwater mining on jordan s hot springs can be stated as a fact