sedimentation and basin formation related to ophiolite nappe emplacement miocene sw turkey abstract the miocene kasaba basin in southwestern turkey is a peripheral foreland basin that resulted from the thrusting and emplacement of the lycian nappes ophiolite unit onto a previously stable carbonate platform the resulting basin fill is the product of the complex interaction of tectonic and sedimentary processes and records the timing and magnitude of tectonic events in the thrust belt initial emplacement of the nappes in the late aquitanian resulted in the foundering and irregular subsidence of the carbonate platform by burdigalian times continued loading of the carbonate platform resulted in the development of a sedimentary basin ca 170 km across fan deltas shed off the leading edge of the nappe pile passed basin wards into a series of small submarine fans at the same time a peripheral bulge developed in the central part of the carbonate platform along the margin of the basin opposite the nappe pile a thick wedge of sediments derived from the carbonate platform was shed northwestwards into the basin varying sedimentation rates and migrating facies belts in the overlying middle and upper miocene basin fill sequence document both the progressive emplacement of the lycian nappes approximately 100 km from the northwest over the basin margin and overstep of the peripheral bulge

synthrusting deposition of the pennsylvanian and permian strathearn formation northern carlin trend nevada abstract the middle upper pennsylvanian and middle lower permian strathearn formation belongs to the overlap assemblage of the antler orogen in nevada at beaver peak near the carlin trend of gold deposits it contains synorogenic conglomerate deposits associated with emplacement of a regionally extensive 1 km thick tectonic wedge that is floored by the coyote thrust normal marine conodont biofacies throughout the strathearn formation suggest middle shelf or deeper depositional environments the allochthon floored by the coyote thrust has been thrust above a middle upper pennsylvanian lower conglomerate unit of the strathearn formation a middle lower permian upper conglomerate unit the highest unit recognized in the strathearn formation as well as similarly aged dolomitic siltstone onlap directly onto ordovician quartzarenite of the vinini formation that makes up most of the coyote allochthon quartz grains and quartzarenite fragments of variable roundness and shape in the conglomerate units were derived from the presently adjoining tectonic lobe of mostly quartzarenite that advanced southeast present geographic coordinates during the late paleozoic into the developing strathearn basin chert fragments in the conglomerates probably were derived mostly from devonian slaven chert including a widespread thick melange unit of the slaven chert in the footwall of the coyote thrust lithologic and shape ratio data from approximately 4200 clasts at 17 sites of the two major conglomerate units in the strathearn formation at beaver peak are roughly similar in that they contain only chert and quartzarenite clasts and chert clasts predominate in both units they differ in the relative proportion of the two lithologies whereby quartzarenite clasts increase sixfold in the upper unit middle lower permian versus its content in the lower conglomerate unit relations at the unconformity between the upper conglomerate unit and its underlying quartzarenite shows quartzarenite fragments actually breaking away from an immediately subjacent source ordovocian quartzarenite which forms a tectonically uplifted wedge with the coyote thrust at its base became a source region for much of the quartzarenite detritus deposited preferentially in the upper parts of the strathearn formation the conglomerate units of the strathearn formation temporally bracket emplacement of the coyote thrust thrusting related to contractional reactivation of the robert mountains thrust system largely was completed by middle early permian

the geohydrologic setting of yucca mountain nevada abstract this paper provides a geologic and hydrologic framework of the yucca mountain region for the geochemical papers in this volume the regional geologic units which range in age from late precambrian through holocene are briefly described yucca mountain is composed of dominantly pyroclastic units that range in age from 11 4 to 15 2 ma the principal focus of study has been on the paintbrush group which includes two major zoned and welded ash flow tuffs separated by an important hydrogeologic unit referred to as the paintbrush non welded ptn the regional structural setting is currently one of extension and the major local tectonic domains are presented together with a tectonic model that is consistent with the known structures at yucca mountain streamflow in this arid to semi arid region occurs principally in intermittent or ephemeral channels near yucca mountain the channels of fortymile wash and amargosa river collect infrequent runoff from tributary basins ultimately draining to death valley beneath the surface large scale interbasin flow of groundwater from one valley to another occurs commonly in the region regional groundwater flow beneath yucca mountain originates in the high mesas to the north and returns to the surface either in southern amargosa desert or in death valley where it is consumed by evapotranspiration the water table is very deep beneath the upland areas such as yucca mountain where it is 500 750 m below the land surface providing a large thickness of unsaturated rocks that are potentially suitable to host a nuclear waste repository the nature of unsaturated flow processes which are important for assessing radionuclide migration are inferred mainly from hydrochemical or isotopic evidence from pneumatic tests of the fracture systems and from the results of in situ experiments water seeping down through the unsaturated zone flows rapidly through fractures and more slowly through the pores of the rock matrix although capillary forces are expected to divert much of the flow around repository openings some may drip onto waste packages ultimately causing release of radionuclides followed by transport down to the water table

3 d numerical simulations of earthquake ground motion in sedimentary basins testing accuracy through stringent models summary differences between 3 d numerical predictions of earthquake ground motion in the mygdonian basin near thessaloniki greece led us to define four canonical stringent models derived from the complex realistic 3 d model of the mygdonian basin sediments atop an elastic bedrock are modelled in the 1d sharp and 1d smooth models using three homogeneous layers and smooth velocity distribution respectively the 2d sharp and 2d smooth models are extensions of the 1 d models to an asymmetric sedimentary valley in all cases 3 d wavefields include strongly dispersive surface waves in the sediments we compared simulations by the fourier pseudo spectral method fpsm the legendre spectral element method sem and two formulations of the finite difference method fdm s and fdm c up to 4hz the accuracy of individual solutions and level of agreement between solutions vary with type of seismic waves and depend on the smoothness of the velocity model the level of accuracy is high for the body waves in all solutions however it strongly depends on the discrete representation of the material interfaces at which material parameters change discontinuously for the surface waves in the sharp models an improper discrete representation of the interfaces can cause inaccurate numerical modelling of surface waves for all the numerical methods considered except sem with mesh of elements following the interfaces a proper implementation of interfaces requires definition of an effective medium consistent with the interface boundary conditions an orthorhombic effective medium is shown to significantly improve accuracy and preserve the computational efficiency of modelling the conclusions drawn from the analysis of the results of the canonical cases greatly help to explain differences between numerical predictions of ground motion in realistic models of the mygdonian basin we recommend that any numerical method and code that is intended for numerical prediction of earthquake ground motion should be verified through stringent models that would make it possible to test the most important aspects of accuracy

antler orogeny a mediterranean type orogeny the late cenozoic thrust belts of the apennine carpathian and hellenic systems of the mediterranean region provide modern analogues for the middle paleozoic antler orogeny each of these young or active mountain belts formed in convergent systems in which thrusting occurred behind a zone of trench retreat while a region of extension developed contemporaneously within the hanging wall of the subduction systems dynamic models that have been recently developed for these tectonic systems provide a basis for interpretation for the antler belt many if not all of the geologic relations observed in the antler belt including the lack of a collided arc and subsidence of a broad extensional region behind the thrust belt are also present within these young mediterranean thrust belt systems if this interpretation is correct then the entire antler belt may have been preserved with no need for other tectonic elements to have been present west of the antler thrust belt and the havallah basin

formation stratification and mixing of the cores of earth and venus abstract earth possesses a persistent internally generated magnetic field whereas no trace of a dynamo has been detected on venus at present or in the past although a high surface temperature and recent resurfacing events may have removed paleomagnetic evidence whether or not a terrestrial body can sustain an internally generated magnetic field by convection inside its metallic fluid core is determined in part by its initial thermodynamic state and its compositional structure both of which are in turn set by the processes of accretion and differentiation here we show that the cores of earth and venus like planets should grow with stable compositional stratification unless disturbed by late energetic impacts they do so because higher abundances of light elements are incorporated into the liquid metal that sinks to form the core as the temperatures and pressures of metal silicate equilibration increase during accretion we model this process and determine that this establishes a stable stratification that resists convection and inhibits the onset of a geodynamo however if a late energetic impact occurs it could mechanically stir the core creating a single homogenous region within which a long lasting geodynamo would operate while earth s accretion has been punctuated by a late giant impact with likely enough energy to mix the core e g the impact that formed the moon we hypothesize that the accretion of venus is characterized by the absence of such energetic giant impacts and the preservation of its primordial stratifications

middle devonian mississippian stratigraphy on and near the nevada test site implications for hydrocarbon potential paleozoic strata on the nevada test site and surrounding area are affected by the intersection of several important geologic trends including the early paleozoic rift margin and the late devonian early mississippian antler orogenic foredeep upper paleozoic strata are lithologically diverse and include siliciclastic sediments carbonaceous shale clean quartzose sands bedded chert and chert lithic conglomerate and sand and various carbonates these are interpreted to have been deposited in a range of environments and water depths the resulting complex stratigraphy with its dramatic vertical and lateral changes is difficult to correlate even between nearby surface and subsurface sections our detailed stratigraphic studies on and near the nevada test site show that at least three distinct and largely coeval mississippian facies assemblages can be recognized when dated correlated and restored to their original relative geographic positions these sections allow a new reconstruction of the devonian and mississippian geologic history that includes 1 delineation of the antler foredeep basin and its clastic fill 2 description of the muddy marginal shelf that lay inboard of the foredeep and 3 correlation from that shelf to the outer fringes of the carbonate platform that characterizes the edge of the mississippian epicontinental sea the position and delineation of the mud dominated marginal shelf environment is particularly important because shales deposited under such conditions elsewhere in the great basin are the hydrocarbon source rocks for the pine valley and railroad valley oil fields on the nevada test site mississippian shale probably generated hydrocarbons in the past and still has an organic content and a thermal history appropriate for generating hydrocarbons

on the thermo chemical origin of the stratified region at the top of the earth s core abstract i developed a combined model of the thermal and chemical evolution of the earth s core and investigated its influence on a thermochemically stable region beneath the core mantle boundary cmb the chemical effects of the growing stable region are caused by the equilibrium chemical reaction between silicate and the metallic core the thermal effects can be characterized by the growth of the sub isentropic shell which may have a rapid growth rate compared to that of the chemically stable region when the present day cmb heat flow was varied the origin of the stable region changed from chemical to thermochemical to purely thermal because the rapid growth of the sub isentropic shell can replace the chemically stable region physically reasonable values of the present day cmb heat flow that can maintain the geodynamo action over 4 billion years should be between 8 and 11 tw to constrain the thickness of the thermochemically stable region beneath the cmb the chemical diffusivity is important and should be o 10 8 m 2 s to obtain a thickness of the thermochemically stable region beneath the cmb consistent with that inferred from geomagnetic secular variations 140 km however the strength of the stable region found in this study is too high to be consistent with the constraint on the stability of the stable region inferred from geomagnetic secular variations

the 1978 earthquake sequence near thessaloniki northern greece summary this paper presents a detailed study of teleseismically and locally recorded foreshocks and aftershocks of the 1978 thessaloniki earthquake sequence and discusses the relations between the locations and mechanisms of these shocks and the three dimensional geometry of faulting in the source region sixteen teleseismically recorded events were relocated using a relative relocation method and positioned geographically using the accurate locally determined location of the largest aftershock all these shocks had depths shallower than 15 km the spatial distribution of the foreshocks showed that the activity was initiated at the central part of the epicentral region progressed westwards and for about 20 days clustered in the region of the imminent mainshock no teleseismically recorded foreshock was located west of the mainshock location in less than 1 hr after the mainshock large aftershocks occurred west of it and in later stages spanned the entire western part of the epicentral region no teleseismically recorded aftershocks were located east of the mainshock locally recorded aftershocks were accurately located and provided a more detailed picture of the seismic deformation they occurred at depths between 3 and 12 km and in three distinct clusters separated by well defined gaps the largest foreshock on may 23 had a moment of 5 6 1024dyne cm and a mean displacement of 31cm the mainshock on june 20 had a moment of 5 2 1025dyne cm a strain drop of 4 0 10 5 static stress drop of 12 bar and a mean displacement of 64 cm these values are for one of the two possible interpretations of the aftershock distribution which suggests that the largest earthquakes of the sequence occurred on two different but adjacent fault segments the first event 1 on may 23 occurred along the central fault segment and was followed 28 days later by the second event 2 on june 20 along a western fault segment finally 61 days later another smaller earthquake event 3 occurred along another fault east of event 1

on the effect of the 3 d regional geology on the seismic design of critical structures the case of the kashiwazaki kariwa nuclear power plant

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

mid paleozoic age of the roberts thrust unsettled by new data from northern nevada the roberts thrust is a major thrust in nevada on which ordovician to devonian siliceous facies rocks were carried more than 80 km eastward over contemporaneous carbonate facies for more than two decades a mid paleozoic age for this structure has been widely accepted the bases for dating the thrust are 1 the assumption that the roberts thrust formed at the time of the antler orogeny a reliably dated mid paleozoic event and 2 the concept of an overlapping assemblage consisting of sedimentary strata deposited on both the allochthon and autochthon the first assumption is unproved and the second relies on another assumption that the overlap assemblage was not cut and telescoped by the roberts thrust in the years since a mid paleozoic age for the roberts thrust became widely accepted much new information on the stratigraphy and facies relations of mississippian rocks in northern nevada has accumulated one interpretation of these new data suggests that in the pinon range where a mid paleozoic age for the thrust was most convincingly displayed the overlap assemblage actually may have been cut by a major thrust that juxtaposed contrasting facies of mississippian rocks if so the principal evidence used to date the roberts thrust is compromised and the time has come for an agonizing reappraisal of all evidence bearing on the question a mid paleozoic age can no longer be taken for granted and a post paleozoic age cannot be ruled out

determination of oxygen diffusion rates in magnetite from natural isotopic variations the oxygen isotope compositions of magnetite grains hosted in a calcite marble from the bancroft terrane of the ontario grenville province vary systematically with grain size the 18 o values of magnetite and corresponding closure temperatures t c based on calcite magnetite range from 18 o 2 6 t c 505 c for a grain radius of 0 075 mm to 18 o 5 5 t c 660 c for a grain radius of 1 15 mm the 18 o of the calcite is constant within a scale of 100 m at a value of 12 3 the observed isotopic variations can be fit to the diffusion model of dodson by the method of least squares r 0 98 to yield an activation energy q 211 20 kj mole and a pre exponential factor d o 4 3 3 3 1 9 x 10 7 cm 2 s for a cooling rate of 4 c m y the activation energy estimate is independent of the assumed cooling rate but the calculated pre exponential factor varies as follows d o cm 2 s d t d t x 1 08 x 10 7 note d t d t is in c m y the activation energy is identical to an experimental determination by giletti and hess but the pre exponential factor is 100 times lower the difference is attributed to the water rich conditions in the experiments and the absence of fluid in the slowly cooled marbles investigated in this study the strong dependence of diffusion rate on water presence or f h 2 o may be used as a sensor for water rich fluids during cooling in natural systems

roberts mountains thrust relationships in a critical area northern sulphur spring range nevada at the orogenic front of the antler orogeny the roberts mountains allochthon lies on lower mississippian dale canyon formation and consists of middle and upper devonian woodruff formation slivers of silurian to lower devonian roberts mountains formation and ordovician vinini formation in structural succession devonian pilot shale mapped unconformably below dale canyon flysch was mapped previously as allochthonous woodruff formation the vinini recognized here was also mapped previously as woodruff the dale canyon was mapped previously as chainman shale recognition of pilot shale here necessitates the elimination of a previously postulated thrust plate in which woodruff was shown thrust upon devonian carbonate rocks it also makes more consistent the structural sequence within the roberts mountains allochthon along its frontal margin assignment of fine grained siliciclastic turbidites in the flysch trough of the antler foreland to the dale canyon formation eliminates anomalous use of chainman shale as a stratigraphic term and allows its useful retention for delta slope deposits distal to the diamond peak molasse the so called dry creek fault previously interpreted to cross the mapped area cannot be recognized some outcrops of devonian carbonate rocks previously mapped as in structural windows below woodruff formation are actually quaternary landslide blocks

mesozoic deformation in the nevada test site and vicinity implications for the structural framework of the cordilleran fold and thrust belt and tertiary extension north of las vegas valley detailed studies in the cp hills and mine mountain area of the nevada test site nts together with analysis of published maps and cross sections and a reconnaissance of regional structural relations indicate that the cp thrust of barnes and poole 1968 actually comprises two separate oppositely verging mesozoic thrust systems 1 the west vergent cp thrust which is well exposed in the cp hills and at mine mountain and 2 the east vergent belted range thrust located northwest of yucca flat regional structural relations indicate that the cp thrust forms part of a narrow sigmoidal belt of west vergent folding and thrusting traceable for over 180 km along strike the belted range thrust represents earlier mesozoic deformation that was probably related to the last chance thrust system in southeastern california as suggested by earlier workers a reconstruction of the pre tertiary geometry of the cordilleran fold and thrust belt in the region between the nts and the las vegas range bears a close resemblance to other regions of the cordillera and suggests that west vergent deformation developed in the hinterland of a part of the sevier fold and thrust belt characterized by substantial structural relief reconstruction of the fold and thrust belt also suggests that previous estimates of upper crustal tertiary extension north of the las vegas valley shear zone e g 80 guth 1981 are 2 or 3 times too large

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

long period lp events on mt etna volcano italy the influence of velocity structures on moment tensor inversion since a few decades volcanic long period lp events have been recorded on many active volcanoes and their study has been recognized as an important tool to characterize volcanic activity lp event analyses through moment tensor mt inversions have led to kinematic descriptions of various source mechanisms the main challenge in these inversions is to strip out the propagation effect in order to isolate the source hence the velocity model used controls the accuracy of the retrieved source mechanism we first carry out several synthetic tests of inversions on mt etna volcano italy four geological models with topography are considered with increasing complexity the most complex model is used to generate synthetic data while the other three models are used to calculate the greens functions for inversions the retrieved solutions from the three velocity models are similar the mt solutions for a deeper source are well retrieved while a shallower source test suffers from high uncertainties and strong misinterpretation of the source orientation the homogeneous model gives the lowest misfit value but source location and mechanism decomposition are inaccurate when a complex model different from the true one is used a high misfit value and a wrong solution is obtained we then incorporate our findings into the mt inversion of an lp event recorded on mt etna in 2008 we obtain very different solutions among the three models in terms of source location and mechanism decomposition the overall shape of the retrieved source time functions are similar but some amplitude differences arise especially for the homogeneous model our work highlights the importance of including the unconsolidated surface materials in the computation of green s functions especially when dealing with shallow sources

sedimentology and sequence stratigraphy of wedge top clastic successions insights and open questions from the upper tortonian terravecchia formation of the scillato basin central northern sicily italy abstract an up to 1250 m thick clastic succession the upper tortonian terravecchia formation trv has been analysed in detail in the middle late miocene scillato wedge top basin grown above an already deformed tectonic stack in the northern sicilian fold and thrust belt the study involved field based sedimentological and stratigraphic analyses aimed to determine to what extent both the depositional and sequence stratigraphic evolution of the scillato basin have been ruled by syn sedimentary compressional to transpressional tectonics widespread intraformational angular unconformities associated with sudden change of palaeocurrents pattern and successive source area shifting suggest that tectonics acted at least during the late tortonian as a major controlling factor during the sedimentation and generation of the sequential architecture of the basin infill six main facies associations were recognized respectively 1 gravelly braidplain a 2 alluvial plain with ephemeral ponds b 3 sandy gravelly river dominated delta front c 4 brackish prodelta clayey siltstones d 5 prograding delta slopes and delta front e and 6 delta top conglomerates and sandstones f these associations are arranged into two main successive depositional systems 1 the entrenched valley fill system evf and 2 a retrograding to prograding river dominated delta system rds both depositional systems and facies associations are arranged laterally and vertically to create a tectonically induced late tortonian transgressive regressive cycle developed in a time interval roughly coinciding with the iii order 3 1 eustatic cycle the scillato basin transgressive regressive cycle is internally modulated by a depositional sequence set consisting of four iv order sequences here named lts1 lts2 lts3 lts4 respectively bounded by tectonically enhanced unconformities the data here shown from the terravecchia formation suggest that the scillato basin is a good case study of tectonically controlled sequence stratigraphic evolution and an analogy for similar continental to shallow marine wedge top basin infill

sequence stratigraphy and evolution of the antler foreland basin east central nevada the mississippian antler foreland basin contains siliciclastic sedimentary rocks that record a series of orogenic events along the western margin of north america from about 350 to 320 ma our new stratigraphic and sedimentologic studies in nevada indicate that the strata are not generally progradiational as previously described and that uplift played a large role in basin evolution we have recognized three unconformity bounded stratigraphic sequences in the antler basin in central nevada the diamond range submarine fan system the newark valley fluvial and delta plain system and the green springs deltaic and shelf carbonate system they propose a two phase history for the antler orogeny 1 collision of the western edge of north america with the antler allochthon and downwarping of the continental margin 360 350 ma which resulted in deposition of the diamond range submarine fan system and 2 uplift and low amplitude folding of the basin 350 320 ma accompanied by deposition of a thin veneer of reworked siliciclastic sediments newark valley and green springs sequences across a shallow marine shelf siliciclastic sedimentation waned in the late mississippian and early pennsylvanian and gradually gave way to carbonate sedimentation

fan delta sequence in the archean fig tree group barberton greenstone belt south africa abstract the fig tree group of the barberton greenstone belt in south africa records the onset of tectonism and significant terrigenous and volcaniclastic sedimentation following a period of predominantly effusive volcanism in the southern part of the greenstone belt the lower fig tree conformably overlies the onverwacht group and can be grouped into either 1 volcaniclastic deposits consisting of pyroclastic and reworked volcanic detritus or 2 non volcanogenic terrigenous deposits of sandstone and conglomerate these petrologic groups are further divided into six lithofacies the lithofacies within the lower fig tree formation can be grouped into two facies associations 1 a subaqueous delta front association made up of fine grained airfall pyroclastic and slightly reworked pyroclastic debris along with resedimented land derived sandstone and conglomerate and 2 a subaerial association that is interpreted as forming from deposition of sandstone and conglomerate by flashy ephemeral stream processes on an alluvial fan surface the stratigraphic sequence coarsens upward from predominantly siltstone and fine grained sandstone at the base to pebble and cobble conglomerate at the top this sequence is interpreted as forming from the progradation of a fan delta into a body of relatively shallow quiet water composition of clasts in the conglomerates indicates that immediately underlying greenstone belt rocks or coeval volcanic rocks were the source for these coarse sedimentary accumulations erosion of uplifted greenstone belt terrain was apparently only to shallow levels both tectonic and volcanic activity played a role in producing several cycles of fan delta progradation

the shakeout earthquake scenario verification of three simulation sets summary this paper presents a verification of three simulations of the shakeout scenario an mw 7 8 earthquake on a portion of the san andreas fault in southern california conducted by three different groups at the southern california earthquake center using the scec community velocity model for this region we conducted two simulations using the finite difference method and one by the finite element method and performed qualitative and quantitative comparisons between the corresponding results the results are in good agreement with each other only small differences occur both in amplitude and phase between the various synthetics at ten observation points located near and away from the fault as far as 150 km away from the fault using an available goodness of fit criterion all the comparisons scored above 8 with most above 9 2 this score would be regarded as excellent if the measurements were between recorded and synthetic seismograms we also report results of comparisons based on time frequency misfit criteria results from these two criteria can be used for calibrating the two methods for comparing seismograms in those cases in which noticeable discrepancies occurred between the seismograms generated by the three groups we found that they were the product of inherent characteristics of the various numerical methods used and their implementations in particular we found that the major source of discrepancy lies in the difference between mesh and grid representations of the same material model overall however even the largest differences in the synthetic seismograms are small thus given the complexity of the simulations used in this verification it appears that the three schemes are consistent reliable and sufficiently accurate and robust for use in future large scale simulations

roberts mountains allochthon and the western margin of the cordilleran miogeocline in the northern ritter range pendant eastern sierra nevada california the truncated southwestern edge of the roberts mountains allochthon is exposed in the northern ritter range pendant in the eastern sierra nevada structurally overlying parautochthonous rocks of the cordilleran miogeocline the northern ritter range pendant exposes units that have the same stratigraphic affinities and structural relationships as rocks of the antler orogenic belt in nevada paleozoic metasedimentary rocks exposed in the pendant consist of two major units 1 a structurally complex disrupted chert and argillite unit interpreted to be correlative with the roberts mountains allochthon and 2 a stratigraphically coherent siliceous and calcareous unit the rush creek sequence that is interpreted to be part of a transitional outer shelf and slope assemblage of the lower paleozoic cordilleran miogeocline in the northern ritter range pendant the roberts mountains allochthon structurally overlies the rush creek sequence along a north striking steeply dipping fault zone that may be a preserved remnant of the roberts mountains thrust which in north central nevada emplaced the allochthon over outer shelf and slope strata of the cordilleran miogeocline during the late devonian early mississippian antler orogeny these stratigraphic and structural belts are truncated on the southwest side of the pendant by the gem lake shear zone a northwest trending dextral strike slip fault associated with the cretaceous sierra nevada batholith the northern ritter range pendant thus defines both the southwestern limit of the antler orogenic belt and the westernmost exposures of parautochthonous miogeoclinal rocks in the central cordillera

widespread effects of middle mississippian deformation in the great basin of western north america stratigraphic analyses in central and eastern nevada reveal the importance of a deformation event in middle mississippian time that caused widespread deformation uplift and erosion it occurred between middle osagean and late meramecian time and resulted in deposition of both synorogenic and postorogenic sediments the deformation resulted in east west shortening expressed as east vergent folding and east directed thrusting it involved sedimentary rocks of the antler foredeep as well as strata associated with the roberts mountains allochthon a latest meramecian to early chesterian unconformity with correlative conformable lithofacies changes postdates this deformation and occurs throughout nevada a tectonic highland created in the middle mississippian and lasting into the pennsylvanian and centered in the area west and southwest of carlin nevada shed sediments eastward across the antler foreland burying the unconformity post oro genic strata are late meramecian to early chesterian at the base and are widespread throughout the great basin the tectonism therefore occurred 20 to 30 m y after inception of the late devonian antler orogeny significantly extending the time span of this orogeny or representing a generally unrecognized orogenic event in the paleozoic evolution of western north america we propose a revised stratigraphic nomenclature for mississippian strata in nevada based on detailed age control and the recognition of unconformities this approach resolves the ambiguity of some stratigraphic names and emphasizes genetic relationships within the upper paleozoic section we take advantage of better stratigraphic understanding to propose two new stratigraphic units for southern and eastern nevada the middle mississippian gap wash and late mississippian captain jack formations

source related variability of site response in the mygdonian basin greece from accelerometric recordings and 3d numerical simulations abstract we compare different methods to estimate frequency domain amplification and duration lengthening of earthquake ground motion in the mygdonian basin greece amplification is measured by standard spectral ratios ssrs of horizontal component or by single station earthquake horizontal to vertical ratios ehvrs duration lengthening is measured either by the group delay method beauval et al 2003 and labeled gddl or based on the significant duration trifunac and brady 1975 and labeled tbdl the methods are applied both to high quality recordings of the european experimental site euroseistest array and to a large set of 3d synthetics computed in a new basin model for 1260 sources regularly distributed in depth distance and azimuth from the center of the array the analysis of the recordings in the center of the basin shows an anticorrelation between amplification and duration lengthening that is maxima resp minima of gddl correspond to minima resp maxima of ssr the maxima of gddl are also found to coincide with those of ssr variability this is confirmed by the analysis of the synthetics which also reveals a pronounced north south asymmetry of both amplification and duration lengthening caused by nonisotropic excitation of surface waves at the basin edges we find that all estimates of site response depend on source location and that ehvr is also strongly sensitive to energy partitioning in the analyzed wavefield we quantify the source related variability of each estimate discuss the biases in site response estimation using incomplete source catalogs and investigate whether the azimuthal dependence of site response can be identified in the recordings electronic supplement movies of simulated wave propagation figures of surface to downhole standard spectral ratio ssr group delay duration lengthening gddl earthquake horizontal to vertical ratio ehvr and synthetic waveforms

experimental determination of oxygen diffusion in liquid iron at high pressure abstract oxygen diffusion experiments in liquid iron have been performed at 3 18 gpa and 1975 2643 k using a multi anvil apparatus diffusion couples consisted of a pure iron rod and a sintered disk of fe 0 85 o 0 15 placed end to end in a vertical orientation images and chemical spot analyses were acquired along the full length of the quenched sample on lines perpendicular to the diffusion interface exsolution features that formed during quenching consist mostly of spherical oxide blobs of at least two size populations as well as feathery dendritic textures in more oxygen rich regions near the top of the samples diffusion during heating i e prior to reaching the peak annealing temperature t f is treated numerically to refine arrhenian parameters from simultaneous least squares fits to several concentration profiles obtained from experiments at constant pressure and variable t f diffusion coefficients range from 6 10 9 to 2 10 8 m 2 s 1 over the p t range of the study with activation enthalpies of less than 100 kj mol 1 we find a very weak effect of pressure on oxygen diffusion with an activation volume of 0 1 0 1 cm 3 mol 1 in agreement with computational studies performed above 100 gpa arrhenian extrapolation of diffusion coefficients for oxygen to p t conditions of the earth s outer core yields faster average diffusion rates 3 10 8 m 2 s 1 than for si or fe in silicon rich liquid iron alloys or pure liquid iron 5 10 9 m 2 s 1 reported previously oxygen diffusion data are used to constrain the maximum size of descending liquid metal droplets in a magma ocean that is required for chemical equilibration to be achieved our results indicate that if the earth s core composition is representative of equilibrium chemical exchange with a silicate magma ocean then it could only have been accomplished by large scale break up of impactor cores to liquid iron droplet sizes no larger than a few tens of centimeters

experiments on turbulent metal silicate mixing in a magma ocean we compare the results of laboratory fluid dynamics experiments with theoretical models of turbulent entrainment in two phase buoyant plumes and thermals to estimate the amount of mixing between the iron core of a planetesimal or planetary embryo and the molten silicates in a magma pool formed by its impact with a growing planet during accretion we demonstrate experimentally that turbulent plumes in immiscible fluids fragment into droplets and that the envelope of the droplet distribution is indistinguishable from the envelope of a turbulent plume in a single phase fluid under the same dynamical conditions implying that turbulent entrainment concepts are applicable to immiscible fluids mixing a series of experiments are made on the time evolution of a two phase turbulent thermal representing a planetesimal core falling under its own negative buoyancy in a spherical fluid representing an impact produced magma pool two stages of mixing are observed in these experiments the first corresponding to turbulent entrainment during free fall of the thermal the second corresponding to entrainment in turbulent gravity currents that form after the thermal reaches the base of the magma pool we demonstrate that the amount of mixing between metals and silicate liquids in a magma pool depends on the rouse number of the metal fragments and increases rapidly with the radius of the proto planet we derive a similarity model for metal silicate mixing in a spherical magma pool assuming a constant entrainment coefficient for the turbulent liquid metal phase this model supports our experimental finding that a small metal core of an impactor will become diluted i e mix within a deep magma pool but a large impacting core will not fully dilute before reaching the base of the magma pool

a review of the discrete wavenumber method we present a review of the discrete wavenumber dwn method the method introduced by bouchon and art 1977 allows the simple and accurate calculation of the complete green s functions for many problems in elastodynamics

investigation on the dynamic rupture of the 1970 ms 7 7 tonghai yunnan china earthquake on the qujiang faultinvestigation on the dynamic rupture of the 1970 ms 7 7 tonghai yunnan china earthquake on the qujiang fault

self diffusion and chemical diffusion in peridotite melt at high pressure and implications for magma ocean viscosities abstract self diffusion coefficients of si o mg and ca and chemical diffusion coefficients of ni and co have been determined experimentally up to 24 gpa and 2623 k in anhydrous peridotite liquid using a multi anvil press each diffusion couple consisted of a cylinder of isotopically natural peridotite enriched in 1 wt coo that was mated to a cylinder of chemically similar peridotite enriched in 18o 30si 25mg 44ca and 1 wt nio isotope abundance 18o 30si 25mg 44ca profiles along each sample length and perpendicular to the diffusion interface were analyzed by secondary ion mass spectrometry and ni and co concentration profiles were measured by electron microprobe analysis the rates of self diffusion of si o mg ca and chemical diffusion of ni and co decrease with increasing pressure from 4 to 8 gpa where diffusivity reaches a minimum and then increase with a further pressure increase to reach a maximum at 12 gpa the observed change in the pressure dependence at 8 10 gpa is likely caused by pressure induced structural changes and the formation of high coordinated intermediate species above 12 gpa diffusivities again decrease weakly with increasing pressure most likely as a result of further melt compaction when the coordination changes are complete predicted viscosities from self diffusion coefficients for oxygen obtained using the eyring equation are similar to viscosities measured by falling sphere viscometry including the observed changes of the pressure dependence the effect of pressure on diffusion and viscosity in peridotite melt is small compared with the effect of temperature indicating that the viscosity along the melting curve decreases with depth diffusion parameters determined in this study are used to estimate the viscosity of a magma ocean with a depth of 700 km the results indicate that the viscosity increases from 10 mpa s near the surface to a reach a maximum of 50 mpa s at a depth of 250 km at higher pressures the viscosity decreases to 10 mpa s at a depth of 300 km below which it remains almost constant

transition from turbidite to shallow water sedimentation in the lower salmian tremadocian lower ordovician of the stavelot massif belgium abstract the lower salmian tremadocian lower ordovician in the caledonian stavelot massif belgium consists of a sedimentary rock sequence which is thought to represent a transition from turbidite to shallow water sedimentation the succession starts with graptolitic mudstones and low density turbidites this is considered to be a relatively deep basin plain association the intermediate part is composed of finely laminated mudstones and siltstones with minor turbidites and is interpreted as a depositional slope sequence the upper part consists of siltstones which sometimes show wave influence and thick continuous sandstone bodies which are interpreted as offshore sand bars on a shelf this sequence is thought to represent the filling of a cambro ordovician epicontinental basin by a northward prograding clastic wedge characterized by high sedimentation rates

deformation dewatering and decollement development in the antler foreland basin during the antler orogeny we present evidence from north central nevada that structures in the antler foreland basin formed before lithification of kinderhookian flysch indicating that deformation occurred during emplacement of the roberts mountains allochthon onto the north american shelf during the late paleozoic antler orogeny a decollement coeval with prelithification structures developed within the foreland basin at the transition from fine grained sediments below to coarse grained sediments above and suggests that the roberts mountains allochthon entered its own foreland basin at mid level in the sediment section as do modern accretionary prisms at fore arcs growth of the decollement was facilitated by dewatering of the fine grained sediments and high fluid pressures at the base of the coarse grained section deformation of the footwall suggests either footwall collapse or fluid pressures lower than those along decollements in modern fore arcs

geologic and geophysical evidence for the influence of deep crustal structures on paleozoic tectonics and the alignment of world class gold deposits north central nevada usa abstract geologic data concur with geophysical and isotopic data that suggest the presence of deep crustal fault zones along the battle mountain eureka bme trend and elsewhere in nevada the fault zones may have originated during proterozoic rifting of the continent and were likely substantially reactivated and modified during paleozoic tectonism five distinct paleozoic structural and stratigraphic domains are defined that demonstrate the complexity of paleozoic tectonic events and also lead to hypotheses about ways in which the margin could have been modified the current locations of these domains adjacent to the geophysically and isotopically defined indicators of the buried continent edge corroborate their interactions with the continental margin during the tertiary preexisting crustal fault zones were intersected and reopened during episodes of extension and served as the conduits for deep sourced gold rich fluids which were disseminated into paleozoic slope facies sedimentary rocks forming sediment hosted carlin type and other deposits multiple factors including the locations of these deep seated structures the original configuration of the lower paleozoic continental margin of nevada and its subsequent reactivation during the paleozoic all were fundamental controls on the location of younger mineral deposits a clearer understanding of the original configuration of the margin and of the effects of subsequent paleozoic and mesozoic tectonic events on the margin would provide insight into the locations of these and other prospective mineral belts

a mid permian chert event widespread deposition of biogenic siliceous sediments in coastal island arc and oceanic basins abstract radiolarian and conodont of permian siliceous rocks from twenty three areas in teh the circum pacific and mediterranean regions reveal a widespread permian chert event during the middle leonardian to wordian radiolarian and or sponge spicule rich siliceous sediments accumulated beneath high productivity zones in coastal island arc and oceanic basins most of these deposits now crop out in fault bounded accreted terranes biogenic siliceous sediments did not accumulate in terranes lying beneath infertile waters including the marine sequences in terranes of northern and central alaska the permian chert event is coeval with major phosphorite deposition along the western margin of pangea phosphoria formation and related deposits a well known analogue for this event is middle miocene deposition of biogenic siliceous sediments beneath high productivity zones in many parts of the pacific and concurrent deposition of phosphatic as well as siliceous sediments in basins along the coast of california interrelated factors associated with both the miocene and permian depositional events include plate reorientations small sea level rises and cool polar waters

mississippian mud rocks of the eastern great basin stratigraphy tectonic significance and hydrocarbon potential a thick succession of mississippian mud rocks in the eastern great basin has historically been identified as the chainman shale and interpreted as a foreland basin deposit associated with the antler orogeny our work shows that this section is two distinct mud rock units separated by a late mississippian unconformity the gap wash formation is identified as the mud rock below the unconformity and chainman shale is restricted to mud rock above the unconformity poor exposure sparse age control and limited lithologic contrast have hampered identification and correlation of the mud rock units new research identifies subtle differences in rock type and mineralogical and source rock analyses show that the two formations have contrasting characteristics these are associated with petrophysical properties that can be correlated across the region the data show that the gap wash formation has significantly more organic carbon and better pyrolysis results than the chainman shale the gap wash also has mineralogy that could make it more suitable for treatment as a shale reservoir the new understanding of mississippian mud rocks in the great basin can focus future hydrocarbon exploration the mud rock units record regional mississippian paleogeographic evolution the gap wash formation was deposited into accommodation space created by the loading of the continental margin during the antler orogeny the chainman shale was deposited in a successor basin that formed in response to resumed continental margin contraction in the late meramecian to early chesterian and is not clearly associated with the antler orogeny

depositional facies of mississippian clastics antler foreland basin central diamond mountains nevada abstract in the central diamond mountains of eastern nevada about 2000 m of mississippian clastic strata in the chainman shale and diamond peak formation were deposited in the antler foreland basin paleocurrents and petrographic data confirm that the provenance to the west was the antler orogenic belt formed by emplacement of the roberts mountains allochthon the foreland clastic sequence rests disconformably upon and is overlain gradationally by shelf carbonates that were deposited along the cordilleran continental margin both before and after the antler event the basin fill thus contains a full record of the foreland subsidence that accompanied and followed the antler orogeny detailed facies mapping indicates that the clastic succession includes two main divisions a a lower retrogradational sequence 750 1000 m of basin slope and submarine fan sediment deposited as active tectonic subsidence increased water depths from neritic to bathyal and b an upper progradational sequence 1000 1250 m of delta slope and delta platform sediment deposited as passive isostatic subsistence accompanied progressive shoaling of the sediment surface the retrogradational facies contain prominent turbidites and include in ascending order 1 upper slope facies of shale with resedimented carbonates 2 lower slope facies of shale with olistostromal beds and lenticular sandstones 3 inner fan facies of shale with amalgamated conglomerate and sandstone packets and 4 midd e fan facies of interbedded shale and sandstone in thinning upward packets the progradational facies constitute a fan delta assemblage that includes 1 delta slope facies of shale and siltstone with ravine fill lenses of conglomerate and sandstone that become more prevalent upward 2 delta front facies of interbedded distributary coarse clastics and interdistributary fine clastics and bioclastic limestones and 3 delta plain facies of conglomeratic sandstones and red hutites in fining upward channel floodplain cycles the antler foreland basin thus contains both flyschlike and molasselike sequences in a characteristic succession that probably reflects collision orogeny followed by erosional denudation of orogenic highlands initial tectonic downflexure to form a deep water trough was later counteracted by sedimentation even though isostatic subsidence under sediment loading continued

observations and modeling of long period ground motion amplification across northeast china basin resonances can significantly amplify and prolong ground shaking and accurate site amplification estimates are crucial for mitigating potential seismic hazards within metropolitan basins in this work we estimate the site amplification of long period 2 10 s ground motions across northeast china for both surface waves and vertically incident shear waves the spatial distribution of relatively large site amplifications correlates strongly with known sedimentary basins for both wave types however the site response of surface waves is typically twice as high as that of shear waves at most basin sites we further show that these site amplification features can be well explained by predictions based on the local one dimensional structure at each site our results highlight the importance of accounting for surface wave contributions and demonstrate the usefulness of semi analytical theory for surface wave amplification which may be broadly applicable in future seismic hazard analysis

structure and dynamics of earth s inner core abstract the seismological exploration of the earth s inner core has revealed unexpected and puzzling structural complexities its elastic anisotropy is now well established and has been shown to vary spatially there is a well defined hemispherical dichotomy in anisotropy and attenuation and significant variations in the radial direction with weaker anisotropy in the uppermost regions and possibly different properties in an innermost inner core of radius 300 600 km perhaps even more puzzling is the observation of a stably stratified layer at the base of the outer core which has recently been proposed to result from melting of inner core material if confirmed the presence of this layer has major implications for our understanding of convection in the outer core inner core differential rotation with respect to the mantle remains controversial we will review here recent progress in understanding the dynamics of the inner core a number of different models have been proposed for the development of the inner core s structure and formation of the stable layer at the base of the outer core and particular care will be taken to clarify under which conditions the proposed mechanisms can be active

weak motion observations and modeling for the turkey flat u s site effects test area near parkfield california abstract in order to determine the stability of the weak motion site response and test the ability of geotechnical measurements to predict site response empirical transfer functions and theoretical site amplification functions were compared at several sites across turkey flat site effects test area near parkfield california observed site response relative to a bedrock reference site was determined for a given site by using the fourier amplitude spectral ratio method two separate studies were conducted a profile study and a site specific study surface bedrock site response between two cross valley rock stations separated by 2 km agreed to within 30 sensor separations of 10 and 20 m were used in the profile study at several sites spaced 100 m apart out onto the valley of the test area surface stiff soil site response over a sensor separation of 10 m is reproducible to within 30 for sensor separations of 20 m there are occasional significant variations in stiff soil site response by a factor of 2 to 3 in the 10 to 20 hz band for sensor separations of 100 m there are systematic variations in stiff soil site response by a factor of 3 to 10 in the 5 to 20 hz band related to variations in soil thickness site specific weak motion mean spectral ratios and their standard deviations sd9s serve as empirical predictions of strong motion transfer functions for the stiff soil conditions found at turkey flat observed transfer functions were modeled using relative amplification functions from the computer program shake a better fit to the amplitude of resonance peaks is obtained using damping values close to those measured in situ as opposed to damping values determined by laboratory tests inaccuracies in the standard geotechnical model for turkey flat real 1988 lead to inaccuracies in calculated weak motion transfer functions when compared with observations modeling of observed transfer functions indicates that the model fit is sensitive to 5 changes in s wave velocity uncertainties of 10 to 20 in field measurements of s wave velocity at turkey flat suggest that accurate and consistent prediction of weak motion may not be possible when based on field geotechnical measurements alone

simulation of the basin effects in the po plain during the emilia romagna seismic sequence 2012 using empirical green s functions the two main earthquakes that occurred in 2012 may 20 and 29 in the reggio emiliano region northern italy were relatively small mw 6 1 and mw 5 9 but they generated unexpected damages in a large area around the epicenter on some stations the observed seismic levels exceeded design levels recommended by the ec8 seismic code for buildings and civil engineering works the ground motions generated by the two mainshocks have specific characteristics the waveforms are mainly controlled by surface waves generated by the deep sedimentary po plain by local site effects and also on some stations by non linear behaviors in this particular context we test the ability of an empirical green s function egf simulation approach to reproduce the recorded seismograms in a large frequency band without any knowledge of the underground medium we focus on the possibility to reproduce the strong surface waves generated by the basin at distances between 25 and 90 km we choose to work on the second mainshock of the sequence mw 5 9 which occurred on may 29 2012 because it is better recorded by the seismological networks than the may 20th first mainshock we use a k 2 kinematic source model to generate a set of 100 slip distributions on the fault plane and choose the recordings of a close by mw 3 9 event as egf we then generate a set of broad band seismograms from 0 2 to 35 hz and compare them to the mainshock signals at 15 stations seismograms fourier spectra pga pgv duration stockwell transforms at epicentral distances from 5 to 160 km we find that the main specific features of the signals are very well reproduced for all the stations within and beyond the basin nevertheless at nearby stations the pga values are over evaluated which could be explained by the fact that non linear effects are not taken into account in the simulation process a better fit was found for a position of the nucleation point to the bottom west of the fault that suggest a directivity effect of the rupture process of the may 29th event towards the north east

mississippian through permian orogenesis in eastern nevada post antler pre sonoma tectonics of the western cordillera mississippian through permian strata in eastern nevada and related strata in southern nevada and southern idaho document a series of tectonic episodes that are either generally unrecognized or assigned to the antler or sonoma orogenies some of these were local and others were regional in scale and none fit either the antler or sonoma orogenies as normally defined they are listed below along with the last phase of the antler and the first phase of the somoma orogenies

dike hosted ores of the beast deposit and the importance of eocene magmatism in gold mineralization of the carlin trend nevada a reply we appreciate the comments of g d langstaff and the opportunity to elaborate on the origin of carlin type gold deposits langstaff focuses on two of the critical issues regarding these deposits their age and spatial association with igneous rocks although his comment mentions almost every known carlin type deposit our reply focuses on deposits in major districts direct dating of hydrothermal minerals and indirect dating based on crosscutting relations with pre syn or postmineral rocks in nevada have demonstrated that major deposits in all trends are eocene emsbo et al 1996 leonardson and rahn 1996 phinisey et al 1996 groff et al 1997 hall et al 1997 2000 hofstra et al 1999 hofstra and cline 2000 johnston 2000 ressel et al 2000a b tretbar et al 2000 although many carlin type deposits are not dated we emphasize that no deposit has been demonstrated to be any other age preliminary 40ar 39ar dating of white micas from mineralized eocene dikes at meikle and griffin in the carlin trend gives eocene ages ressel et al 2000b any discussion of the origin especially spatial association of carlin type deposits with igneous rocks must emphasize the northern and central carlin trend fig 1 deposits there constitute 60 percent of the total estimated contained gold in carlin type deposits of nevada and utah hofstra and cline 2000 we interpreted the 700 km2 aeromagnetic anomaly fig 1 there to reflect an underlying composite eocene intrusion emplaced between about 40

oxygen diffusion in magnetite the diffusion rate of oxygen in magnetite fe3o4 has been measured under hydrothermal conditions between 800 and 500 c at 1000 bars pressure and yields the arrhenius relation d 3 5 10 6 exp 45 000rt kcal g atom o the diffusion rate was found to be the same within the estimated uncertainty of a factor of 2 for measurements at 100 1000 and 2000 bars 20 200 mpa water pressure and for oxygen fugacities buffered by magnetite hematite and approximately ninio the activation energy and diffusion mechanism probably change to that given by castle and surman 10 at temperatures below 460 c the oxygen diffusion rate in magnetite is between those of quartz and hornblende closure temperatures fall in the range 380 c for 0 1 mm radius grains cooling at 1 c m y to 675 c for 1 mm radius and cooling at 1000 c m y if the present data are used but will be lower for the fine grain sizes and slow cooling rates if the castle and surman data are used

crustal structure of the ruby mountains and southern carlin trend region nevada from magnetotelluric data abstract we have collected about 150 magnetotelluric mt soundings in northeastern nevada in the region of the ruby mountains metamorphic core complex uplift and southern carlin mineral trend in an effort to illuminate controls on core complex evolution and deposition of world class gold deposits the region has experienced a broad range of tectonic events including several periods of compressional and extensional deformation which have contributed to the total expression of electrical resistivity most of the soundings reside in three east west profiles across increasing degrees of core uplift to the north bald mountain harrison pass and secret pass latitudes one short cross line was also taken to assess an east west structure to the north of the northern profile model resistivity cross sections were derived from the mt data using a 2 d inversion algorithm which damps departures of model parameters from an a priori structure geological interpretation of the resistivity combines previous seismic potential field and isotope models structural and petrological models for regional compression and extension and detailed structural stratigraphic interpretations incorporating drilling for petroleum and mineral exploration to first order the resistivity structure is one of a moderately conductive phanerozoic sedimentary section fundamentally disrupted by intrusion and uplift of resistive crystalline rocks late devonian and early mississippian shales of the pilot and chainman formations together form an important conductive marker sequence in the stratigraphy and show pronounced increases in conductance conductivity thickness product from east to west these increases are attributed to graphitization caused by elko sevier era compressional shear deformation and possibly by intrusive heating the resistive crystalline central massifs adjoin the host stratigraphy across crustal scale steeply dipping fault zones the zones provide pathways to the lower crust for heterogeneous upper crustal induced electric current flow resistive core complex crust appears steeply bounded under the middle of the neighboring grabens and not to deepen at a shallow angle to arbitrary distances to the west the numerous crustal breaks imaged with mt may contribute to the low effective elastic thickness t e estimated regionally for the great basin and exemplify the mid crustal steeply dipping slip zones in which major earthquakes nucleate an east west oriented conductor in the crystalline upper crust spans the east humboldt range and northern ruby mountains the conductor may be related to nearby graphitic metasediments with possible alteration by middle tertiary magmatism lower crustal resistivity everywhere under the profiles is low and appears quasi one dimensional it is consistent with a low rock porosity

wave propagation modelling of induced earthquakes at the groningen gas production site gas extraction from the groningen natural gas field situated in the netherlands frequently induces earthquakes in the reservoir that cause damage to buildings and pose a safety hazard and a nuisance to the local population due to the dependence of the national heating infrastructure on groningen gas the short term mitigation measures are mostly limited to a combination of spatiotemporal redistribution of gas production and strengthening measures for buildings all options become more effective with a better understanding of both source processes and seismic wave propagation detailed wave propagation simulations improve both the inference of source processes from observed ground motions and the forecast of ground motions as input for hazard studies and seismic network design the velocity structure at the groningen site is relatively complex including both deep high velocity and shallow low velocity deposits showing significant thickness variations over relatively small spatial extents we performed a detailed 3 d wave propagation modelling study for an induced earthquake in the groningen natural gas field using the spectral element method we considered an earthquake that nucleated along a normal fault with local magnitude of ml 3 we created a dense mesh with element size varying from 12 to 96 m such that with a dominant source frequency of 7 hz waveforms with a frequency content up to 10 hz could be accurately modelled the velocity density model is constructed using a 3 d geological model of the area including both deep high velocity salt deposits overlying the source region and shallow low velocity sediments present in a deep and narrow tunnel valley the results show that the 3 d density velocity model in the groningen area clearly plays a large role in the wave propagation and resulting surface ground motions and causes significant lateral variations in site response the highvelocity salt deposits have a dispersive effect on the radiated wavefield reducing the seismic energy reaching the surface near the epicentre in turn the presence of low velocity tunnel valley deposits can locally cause a significant increase in peak ground acceleration here we study induced seismicity on a local scale and use specfem3d to conduct full waveform simulations and show how local velocity variations can affect seismic records the author s 2018

timing and mode of emplacement of the roberts mountains allochthon antler orogeny this antler model involves incipient subduction of continental crust and miogeoclinal strata beneath an accretionary wedge composed primarily of oceanic sedimentary rocks and lesser outer shelf strata under thrusting and sediment obduction three phases of associated tectonism are 1 first emplacement phase in which only oceanic crust is subducted evidenced primarily by foreland epeirogeny 2 second emplacement phase in which incipient subduction of continental crust occurs and a flysch trough is formed 3 post emplacement phase of isostatic uplift of continental margin and allochthon accompanied by molasse sedimentation the first two phases associated with compressive movements of the antler orogeny of nevada occurred between mid frasnian and mid osagean time this interval equals about 23 m y based on c a sandberg9s estimates of the duration of conodont zones overlap of the surface trace of the roberts mountains thrust by the kinderhookian webb formation preceded final emplacement of the allochthon ordovician devonian and kinderhookian units in the allochthon as mapped in the carlin pinyon range area by smith and ketner overlie the oldest antler flysch kinderhookian age and are interpreted to have been encased within the antler clastic wedge during osagean time

kinematics of underthrusting in the paleozoic antler foreland basin field mapping and structural analysis of paleozoic rocks in the northern roberts mountains in central nevada reveal that fine grained siliciclastic strata deposited early in the history of the antler foreland basin underthrust and underplated as two discrete fault bound packets to the roberts mountains allochthon as it encroached upon the north american continental shelf underplating also resulted in the intercalation of north american outer shelf slope strata between the two foreland basin packets as the basal detachment of the roberts mountains allochthon stepped downward in the sedimentary section deformation of foreland basin and outer shelf slope strata was in response to ese in layer shortening accompanied by top ese layer parallel shear within 10 m of fault surfaces along which underplating and underthrusting occurred stratal disruption fold tightness and asymmetry and cleavage development near the lower and upper bounding faults are greater than in the center of underthrust packages indicat

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

earthquake ground motion in the mygdonian basin greece the e2vp verification and validation of 3d numerical simulation up to 4 hz n a low seismicity context the use of numerical simulations becomes essential due to the lack of representative earthquakes for empirical approaches the goals of the euroseistest verification and validation project e2vp are to provide 1 a quantitative analysis of accuracy of the current most advanced numerical methods applied to realistic 3d models of sedimentary basins verification and 2 a quantitative comparison of the recorded ground motions with their numerical predictions validation the target is the euroseistest site located within the mygdonian basin greece the site is instrumented with surface and borehole accelerometers and a 3d model of the medium is available the simulations are performed up to 4 hz beyond the 0 7 hz fundamental frequency thus covering a frequency range at which ground motion undergoes significant amplification the discrete representation of material heterogeneities the attenuation model the approximation of the free surface and nonreflecting boundaries are identified as the main sources of differences among the numerical predictions the predictions well reproduce some but not all features of the actual site effect the differences between real and predicted ground motions have multiple origins the accuracy of source parameters location hypocentral depth and focal mechanism the uncertainties in the description of the geological medium damping internal sediment layering structure and shape of the sediment basement interface overall the agreement reached among synthetics up to 4 hz despite the complexity of the basin model with code to code differences much smaller than predictions to observations differences makes it possible to include the numerical simulations in site specific analysis in the 3d linear case and low to intermediate frequency range

subaqueous sediment gravity flow deposits practical criteria for their field description and classification a new method for the description and classification of subaqueous sediment gravity flow deposits is proposed the classification scheme employs a convenient letter code and divides deposits individual beds into descriptive categories of two hierarchical levels facies and subfacies facies as the higher rank categories are distinguished chiefly on the basis of sediment type i e bed grain size texture a total of 13 facies have been distinguished g gravel gs gravel sand couplet gys gravelly sand s sand sm sand mud couplet ms mud sand couplet tm silt mud couplet mt mud silt couplet m mud mys muddy sand sym sandy mud myg muddy gravel gym gravelly mud subfacies as the lower rank categories are distinguished within the individual facies on the basis of the bed s internal structures the number of subfacies is unlimited and their labelling code includes particular facies symbols see above preceded by lower case letters denoting specific sedimentary structures and their vertical arrangement subfacies thus refer to the bed s intervals or divisions which are labelled as follows m massive unstratified and ungraded g graded unstratified and graded s plane stratified x cross stratified 1 parallel and or cross laminated q liquefied for example subfacies gsg graded to plane stratified gravel are gravel beds that have a lower graded interval and an upper plane stratified interval subfacies xg cross stratified gravel are gravel beds that are cross stratified throughout subfacies sls plane stratified to laminated sand are sand beds that have a lower plane stratified interval and an upper laminated parallel and or cross laminated interval

multiple estimates of soil structure at a vertical strong motion array understanding uncertainties from different shear wave velocity profiles abstract we present a detailed study of investigation of various shear wave velocity vs profiles at the tst site of the euroseistest test site we benefit from the availability of 62 vs models derived from earthquake records conventional seismic prospecting and seismic noise array measurements five groups of models provided from many different non invasive and invasive methods seismic interferometry stress strain analysis annealing simulation surface wave inversion cross hole and down hole tests and seismic noise array measurements lead to averaged vs profiles the estimate of vs models that we obtain differs depending on the technique used in such cases it becomes clear that it is better to understand the differences and not simply compute an average the percentage of the observed disparity with respect to the average reference model albeit is small becomes significant at certain depths and is associated with the existence of strong vertical discontinuities thus introducing an uncertainty on the interface definition between the main formations on the other hand the use of vs profiles in ground simulation studies especially 2d or 3d usually implies the need to represent them as gradient functions testing representative generalized power law functions we found that they fail to predict reliably the vs model for the total thickness of sediments to overcome this a third order polynomial function is proposed finally we test the sensitivity of average vsz index widely used in soil categorization and site amplification studies and find that all vs models either measured or proposed are equivalent in terms of vsz vanishing any discrimination between layering as well as models

a re evaluation of metal diapir breakup and equilibration in terrestrial magma oceans abstract due to mechanisms such as impact heating early atmospheric thermal blanketing and radioactive heating the presence of at least one global magma ocean stage in the early histories of terrestrial planets seems unavoidable in such a context a key question to constrain the early thermo chemical evolution of the earth is how much iron diapirs provided by differentiated impactors emulsified during their sinking towards the bottom of an early magma ocean in the past years several workers have focused on this question using however various approaches and making different assumptions while most studies favor rapid breakup and equilibration of iron bodies during their sinking through the magma ocean recent work suggests that iron bodies of size comparable or greater than a few tens of kilometers may preserve most of their initial volume as they reach the bottom of a magma ocean therefore leading to metal silicate disequilibrium to clarify the discrepancies and the differences among studies i have conducted a series of numerical simulations and theoretical calculations to derive the conditions and the timing for the breakup of metal diapirs of any size sinking through a silicate magma ocean with a large range of plausible viscosity values the obtained breakup criterion is used to derive stable diapir sizes and their ability to equilibrate with the surrounding silicates i show that for plausible magma ocean viscosities diapirs with initial radii smaller than the thickness of a magma ocean rapidly break up into stable diapir sizes smaller than 0 2 m at which metal silicate equilibration is rapidly achieved

the equation of state of a molten komatiite 2 application to komatiite petrogenesis and the hadean mantle new experimental data for the equation of state of a komatiitic liquid were used to model adiabatic melting in a peridotitic mantle if komatiites are formed by 30 partial melting of a peridotitic mantle then komatiites generated by adiabatic melting come from source regions that began their unmelted ascent in the lower transition zone 500 670 km or the lower mantle 670 km the great depth of incipient melting implied by this model suggests that komatiitic liquids may form in a pressure regime where they are denser than their coexisting crystals possibly the bulk mantle although komatiitic magmas are thought to separate from residual crystals in the mantle at a temperature 200 c greater than modem mid ocean ridge basalts morbs their ultimate sources are predicted to be diapirs that if adiabatically decompressed from initially solid mantle were more than 700 c hotter than the sources of morbs and were derived from great depth we also studied the evolution of an initially molten mantle i e a magma ocean our model considers the thermal structure of the magma ocean density constraints on crystal segregation and approximate phase relationships for a nominally chondritic mantle crystallization will begin at the core mantle boundary perovskite buoyancy at 70 gpa may lead to a compositionally stratified lower mantle with iron enriched magnesiowustite content increasing with depth large convective velocities in the magma ocean would prohibit crystal liquid fractionation by settling or flotation until quiescent boundary layers form such boundary layers could form when the crystal content of the magma reaches a critical value near 44 vol and in the late stages of crystallization around unmelted blocks of foundered protocrust matrix compaction and diapirism could also lead to fractionation effects the upper mantle could be depleted or enriched in perovskite components relative to the bulk mantle olivine neutral buoyancy may lead to the formation of a dunite septum in the upper mantle partitioning the ocean into upper and lower reservoirs but this septum must be permeable

revisiting the basin edge effect at kobe during the 1995 hyogo ken nanbu earthquake the basin edge effect i e the interference of the direct s wave with the surface wave diffracted off the basin edge has been invoked by many authors to explain the damage distribution during the january 17 1995 hyogo ken nanbu kobe earthquake here we present the results of numerical experiments obtained with the spectral element method in 2 d geometry our results confirm that the amplification of horizontal motion close to the basin edge can be twice as large as the one measured in the center of the basin this additional amplification is shown to depend strongly on the edge geometry and on frequency due to physical dispersion of diffracted surface waves in particular we obtain maximal amplification around 3 hz at frequencies critical for buildings