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

elastic full waveform inversion of multi component obc seismic data elastic full waveform inversion of seismic reflection data represents a data driven form of analysis leading to quantification of sub surface parameters in depth in previous studies attention has been given to p wave data recorded in the marine environment using either acoustic or elastic inversion schemes in this paper we exploit both p waves and mode converted s waves in the marine environment in the inversion for both p and s wave velocities by using wide angle multi component ocean bottom cable seismic data an elastic waveform inversion scheme operating in the time domain was used allowing accurate modelling of the full wavefield including the elastic amplitude variation with offset response of reflected arrivals and mode converted events a series of one and two dimensional synthetic examples are presented demonstrating the ability to invert for and thereby to quantify both p and s wave velocities for different velocity models in particular for more realistic low velocity models including a typically soft seabed an effective strategy for inversion is proposed to exploit both p and mode converted ps waves whilst p wave events are exploited for inversion for p wave velocity examples show the contribution of both p and ps waves to the successful recovery of s wave velocity

introduction to special issue on geologic remote sensing abstract herein we provide an overview of science and technology involved in remote sensing and outlines some practical constraints in applications to geological problems we further summarize diagnostic spectral features of important geological material that can be detected using satellite and air borne remote sensing finally the papers contained in the special issue are briefly introduced

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

mantle crust transition zone and origin of wehrlitic magmas evidence from the oman ophiolite abstract abundant exposure and well preserved outcrops in the oman ophiolite allow detailed observation of the transition from mantle to crust in an oceanic environment the mantle crust transition zone shows large lateral variations in thickness and composition but consists essentially of residual dunites and a magmatic component present as clinopyroxene and plagioclase impregnations and gabbro lenses compositionally the transition zone marks a gradational passage from mantle to crust the moho may be placed at the base of the continuous gabbroic crustal section structures both within the transition zone and near the base of the crust are nearly parallel to the moho however the dominant flow mechanisms differ from the upper mantle to the lower crust plastic flow dominates in the upper mantle while viscous flow resulting in strong magmatic fabrics dominates at crustal levels wehrlitic bodies within the crustal gabbro section are intruded from the transition zone into which they are rooted the parent magma of the wehrlitic instrusions is in fact a crystal melt mixture composed of olivine and chromite probably including a component of mantle xenocrysts and xenoliths and of reequilibrated basaltic melt

mapping of muslim bagh ophiolite complex pakistan using new remote sensing and field data abstract tethys is a relational gis database that combines geophysical remote sensing geochemical and geochronological data developed as a flexible resource for studying magmatic and geodynamic responses to continental collisions in this paper we demonstrate utility of our database by integrating field remote sensing and structural data for detailed mapping and tectonic emplacement of muslim bagh ophiolite of western pakistan this ophiolite forms the uppermost part of a nappe pile which accreted onto the indian continental margin during the closure of the neo tethys during a pre terminal collision that predated the final closure of tethys during the major collision between india and eurasia utilizing the tethys landsat aster imagery and a digital elevation model developed from the aster data are used to characterize the lithology and structure of the area use of image processing techniques improved the geologic map of the area for a better understanding of the tectonic emplacement of the muslim bagh ophiolite for the first time we report that the dikes in the muslim bagh ophiolite are cutting the metamorphic sole our preliminary geochemical data for sheeted dike complex suggest chemical affinities with arc related rocks this observation suggests that dikes were intruded in an island arc environment soon after the ophiolite was formed

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

petrogenesis of plagiogranites in the muslim bagh ophiolite pakistan implications for the generation of archaean continental crust high sio2 rocks referred to as oceanic plagiogranites are common within the crustal sequences of ophiolites however their mode of petrogenesis is controversial with both late stage fractional crystallization and partial melting models being proposed here we present new whole rock data from plagiogranitic dyke like bodies and lenses from the lower and middle sections of the sheeted dyke complex of the cretaceous muslim bagh ophiolite northwestern pakistan the plagiogranites have similar geochemical signatures that are inconsistent with them being the fractionation products of the mafic units of the muslim bagh ophiolite however the plagiogranites all display very low tio2 contents 0 4 wt implying that they formed by partial melting of mafic rocks melt modelling of a crustal gabbro from the muslim bagh ophiolite shows that the trace element signature of the plagiogranites can be replicated by 5 10 melting of a crustal hornblende gabbro with amphibole as a residual phase resulting in a concave up middle rare earth element pattern compositional similarities between the muslim bagh ophiolite plagiogranites and archaean ttg trondhjemite tonalite granodiorite has implications for the generation of juvenile archaean continental crust as the muslim bagh ophiolite was derived in a supra subduction zone it is suggested that some archaean ttg may have been derived from melting of mafic upper crust in early subduction like settings however due to the small volume of muslim bagh ophiolite plagiogranites it is inferred that they can be instructive on the petrogenesis of some but not all archaean ttg

seismic imaging of complex onshore structures by 2d elastic frequency domain full waveform inversion quantitative imaging of the elastic properties of the subsurface at depth is essential for civil engineering applications and oil and gas reservoir characterization a realistic synthetic example provides for an assessment of the potential and limits of 2d elastic full waveform inversionfwiof wide aperture seismic data for recovering high resolution p and s wave velocity models of complex onshore structures fwi of land data is challengingbecauseoftheincreasednonlinearityintroducedbyfreesurface effects such as the propagation of surface waves in the heterogeneous near surface moreover the short wavelengths of the shear wavefield require an accurate s wave velocity starting modeliflowfrequenciesareunavailableinthedata weevaluated different multiscale strategies with the aim of mitigating the nonlinearities massively parallel full waveform inversion was implemented in the frequency domain the numerical optimization relies on a limited memory quasi newton algorithm that outperforms the more classic preconditioned conjugate gradient algorithm the forward problem is based upon a discontinuous galerkin dg method on triangular mesh which allows accuratemodelingoffree surfaceeffects sequentialinversionsofincreasingfrequenciesdefinethemostnaturallevelofhierarchyin multiscale imaging in the case of land data involving surface waves the regularization introduced by hierarchical frequency inversions is not enough for adequate convergence of the inversion a second level of hierarchy implemented with complexvalued frequencies is necessary and provides convergence of the inversion toward acceptable p and s wave velocity models amongthepossiblestrategiesforsamplingfrequenciesintheinversion successive inversions of slightly overlapping frequency groups is the most reliable when compared to the more standard sequential inversion of single frequencies this suggests that simultaneous inversion of multiple frequencies is critical when consideringcomplexwavephenomena

adjoint tomography of the southern california crust using an inversion strategy based on adjoint methods we developed a three dimensional seismological model of the southern california crust the resulting model involved 16 tomographic iterations which required 6800 wavefield simulations and a total of 0 8 million central processing unit hours the new crustal model reveals strong heterogeneity including local changes of 30 with respect to the initial three dimensional model provided by the southern california earthquake center the model illuminates shallow features such as sedimentary basins and compositional contrasts across faults it also reveals crustal features at depth that aid in the tectonic reconstruction of southern california such as subduction captured oceanic crustal fragments the new model enables more realistic and accurate assessments of seismic hazard

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

distal ancestral rocky mountains tectonism evolution of the pennsylvanian permian oquirrh wood river basin southern idaho strata of the oquirrh wood river basin in southern idaho and northeastern nevada provide a record of the northern extent of basin development related to the pennsylvanian permian ancestral rocky mountains sedimentary facies distributions sediment dispersal patterns provenance analyses and subsidence analysis suggest that reactivated thrusting within a segment of the devonian mississippian antler orogenic belt roberts mountains allochthon caused subsidence of the oquirrh wood river basin reactivated thrusting within the antler belt was apparently the primary expression of ancestral rocky mountains tectonism in southern idaho and northeastern nevada stratigraphic architecture of the oquirrh wood river basin was generally controlled by deformation of the roberts mountains allochthon to the west of the basin the oquirrh wood river basin trends north northwest and is obliquely superposed on the eastern margin of the generally north trending roberts mountains allochthon uplift of part of the allochthon resulted in complex sediment dispersal patterns during early basin development early basin fill includes middle pennsylvanian chert pebble conglomerate derived from chert rich roberts mountains allochthon strata to the northwest and west of the basin these conglomerates were deposited in a shallow marine setting on the northwestern to western basin margin and were progressively reworked to the southeast continued reactivation of the antler belt in late pennsylvanian and early permian time resulted in the deposition of a thick quartzite pebble conglomerate sequence along the western basin margin crustal loading during this phase of deformation created a generally north trending foredeep in which as much as 3000 m of mixed siliciclastic carbonate turbidites were deposited in an anoxic marine environment the siliciclastic turbidite fraction was derived from the craton interior to the northeast of the basin whereas the carbonate fraction was derived from a carbonate platform on the eastern basin margin facies relationships sandstone and conglomerate provenance and basin subsidence history constrain the tectonic setting and evolution of the oquirrh wood river basin the oquirrh wood river basin probably developed as a flexural foredeep in front of a reactivated antler thrust belt in a compressional or transpressional setting if basin formation were driven by transpression the basin could be explained by models of the ancestral rocky mountains that relate deformation to the ouachita marathon orogenic belt on the southern margin of north america alternatively a recently proposed model relates the ancestral rocky mountains to pennsylvanian permian andean style convergence on the southwestern margin of north america although the age and location of the convergent margin are poorly constrained in this model it is generally supported by the west east to southwest northeast compression needed to form the oquirrh wood river basin

introduction to tethys an interdisciplinary gis database for studying continental collisions abstract the tethys gis database is being developed as a way to integrate relevant geologic geophysical geochemical geochronologic and remote sensing data bearing on tethyan continental plate collisions the project is predicated on a need for actualistic model templates for interpreting the earth s geologic record because of their time transgressive character tethyan collisions offer actualistic models for features such as continental escape collision induced upper mantle flow magmatism and marginal basin opening associated with modern convergent plate margins large integrated geochemical and geophysical databases allow for such models to be tested against the geologic record leading to a better understanding of continental accretion throughout earth history the tethys database combines digital topographic and geologic information remote sensing images sample based geochemical geochronologic and isotopic data for pre and post collision igneous activity and data for seismic tomography shear wave splitting space geodesy and information for plate tectonic reconstructions here we report progress on developing such a database and the tools for manipulating and visualizing integrated 2 3 and 4 d data sets with examples of research applications in progress based on an oracle database system linked with arcims via arcsde the tethys project is an evolving resource for researchers educators and others interested in studying the role of plate collisions in the process of continental accretion and will be accessible as a node of the national geosciences cyberinfrastructure network geon via the world wide web and ultra high speed internet2 interim partial access to the data and metadata is available at http geoinfo geosc uh edu tethys and http www esrs wmich edu tethys htm we demonstrate the utility of the tethys database in building a framework for lithospheric interactions in continental collision and accretion

geology structure geochemistry and aster based mapping of neoproterozoic gebel el delihimmi granites central eastern desert of egypt abstract the gebel el delihimmi granite intrusion located in the central eastern desert of egypt cuts the core of a major anticlinal structure of calc alkaline metavolcanics and ophiolitic melange rocks the intrusion is microscopically differentiated into granodiorite monzogranite syenogranite and alkali feldspar granite decorrelation stretch and band ratio techniques were applied to advanced spaceborne thermal emission and reflection radiometer data processing of aster swir bands enabled discrimination of el delihimmi granite phases and generation of a detailed lithologic map of the study area the structural and microfabric data suggest that the el delihimmi granite underwent at least two phases of deformations the first was related to the najd fault system during which the older granodiorite phase of the intrusion was affected by sinistral ductile shearing during the second phase monzogranite and syenogranite in the intrusion were affected by brittle e w compressional deformation geochemical data reported here reveal that the granodiorite phase has k 2 o na 2 o ratio 2 o na 2 o ratio 1 the granite phases are generally i type metaluminous to slightly peraluminous and are interpreted as formed above subducted slabs of oceanic lithosphere rather than in continental collision zones

tectonic setting of the bela ophiolites southern pakistan abstract the bela ophiolites consist of a 3 5 km thick sequence of basaltic pillow lava inter flow sedimentary rocks chert argillite limestone and diabase gabbro sills debris of serpentinite up to kilometer sized blocks serpentinite carbonate breccia and less commonly of basalt gabbro peridotite pelagic limestone and their metamorphic equivalents occur throughout the ophiolite sequence and may form extensive horizons the age of the ophiolites as indicated by pelagic microfauna is aptian early maestrichtian the lava flows belong to a spilite keratophyre basaltic andesite suite of tholeiites enriched in fe tio 2 and other trace elements the lava flows although similar to the e type morb differ in details such as la ta ratio ranges 9 62 18 04 for the bela lavas versus 10 15 for the morb the diabase gabbro sills are similar to the associated lava flows however due to their relative enrichment in certain elements e g fe ti hf th and ta etc they may represent more fractionated late melts a comparison of the stratigraphic and structural features of the bela ophiolites with modern oceanic environments reveals that these ophiolites probably originated in a large oceanic fracture zone leaky transform this is based on lithotectonic features such as the common occurrence of debris of foliated serpentinite and serpentinite carbonate breccia bearing rocks in the ophiolite sequence and on geodynamic considerations the fracture zone ancestral to the bela ophiolites probably acted as a boundary between the indian and the neo tethys plates during the cretaceous analogous to the present day owen fracture zone which separates the indian and the arabian plates this ancestral fracture zone was destroyed when transform movement gave way to oblique convergence culminating in the ophiolite obduction in paleocene early eocene time the ophiolite obduction on the west indian continental margin was preceded by alkaline wpb type volcanism which is represented by the porali basalts the bibai lavas and the deccan basalts

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

reprint of introduction to special issue on geologic remote sensing abstract herein we provide an overview of science and technology involved in remote sensing and outlines some practical constraints in applications to geological problems we further summarize diagnostic spectral features of important geological material that can be detected using satellite and air borne remote sensing finally the papers contained in the special issue are briefly introduced

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

direction of ophiolite emplacement inferred from cretaceous and tertiary sediments of an adjacent autochthon the bey daglari southwest turkey the late mesozoic to mid tertiary depositional history of an autochthonous block in southwest turkey is outlined in relation to the direction of emplacement of adjacent allochthonous units in this area a lively debate persists as to whether the antalya complex located along the mediterranean coast should be correlated with the lycian nappes sited to the northwest in central western anatolia both allochthonous bodies include mesozoic ophiolites and similar shallow to deep water sedimentary facies correlation of the antalya complex and the lycian nappes requires transport over the adjacent autochthon the bey daglari here field data from the southern part of the bey daglari are used to trace the depositional history of the autochthon from late cretaceous to late miocene time a pattern of late mesozoic pelagic carbonate deposition giving way to more heterogeneous sedimentation in the early tertiary is documented by early miocene the autochthon was blanketed by a thick sequence of miocene elastics mostly derived from an ophiolite evidence from sedimentary structures shows that transport was from the east and northeast depositional models are advanced which involve an early miocene delta submarine fan giving way in later miocene times to an alluvial fan demonstration that in this area the ophiolite material was derived from the east provides additional important evidence of the existence of a southerly mesozoic oceanic basin distinct in origin from the lycian nappes to the north

bela oceanic lithosphere assemblage and its relation to the reunion hotspot the bela ophiolite of pakistan contains a complete ophiolite accretionary wedge trench sequence emplaced onto the indian continental margin during the northward drift of india seychelles over the active reunion hotspot a structurally higher ophiolite overlies an accretionary prism which is thrust over a foreland basin shear sense determinations in peridotite mylonites in the ophiolite footwall and imbrication structures in the underlying accretionary wedge indicate an ese emplacement sedimentary rocks in the accretionary wedge indicate aptian albian pillow lavas initially deep water conditions and increasing influence from the continent until the maastrichtian the ophiolite emplacement was predated and accompanied by fe tholeiitic and alkaline magmatism related to the reunion hotspot and continuous incorporation of trench sediments into the accretionary wedge 39ar 40ar dating shows that the ophiolite formed around 70 ma intraoceanic subduction initiated between 70 and 65 ma obduction onto the indian passive margin occurred during the formation of the deccan traps at 66 ma and final thrusting onto the continental margin ended in the early eocene 50 ma the ophiolite emplacement occurred during the counterclockwise separation of madagascar and india seychelles which caused shortening and consumption of oceanic lithosphere between the african arabian and the indian seychelles plates

sensitivity study using a genetic algorithm inversion of amplitude variations with slowness a sensitivity study of elastic parameters in amplitude variation with slowness avs for small and large offset seismic data is presented in order to handle the non linearity associated with waveform or amplitude beyond the critical slowness an inversion algorithm based on bayes theory is used a genetic algorithm was used to obtain the a posteriori probability density ppd function the sensitivity analysis is performed on synthetic data containing p wave as well as converted s wave reflections four different two layer models which represent the typical range of avs responses associated with the gas sands normally encountered in exploration were used to examine how well the elastic parameters can be inverted for different parametrizations by comparing the ppd functions the sensitivity study results suggest that including wide angle data in the inversion can greatly enhance the quality of inversion the converted s wave reflections can provide valuable extra information that can be used to extract elastic parameters the results with noisy data demonstrate that the contrast of density and three velocity ratios can be estimated robustly with wide angle reflection data

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

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

the sole of an ophiolite the ordovician bay of islands complex newfoundland the early ordovician c 485 ma bay of islands ophiolite complex was obducted onto the laurentian rifted margin as the fore arc of an oceanic arc that collided with the margin during the mid ordovician c 470 ma the subduction zone was nucleated on an oceanic transform fracture zone part of whose remnants occur as the polyphase deformed and intruded mafic and ultramafic rocks of the coastal complex the ophiolite formed as a suprasubduction zone fore arc ophiolite at the spatial and temporal continuation of the ridge normal to the transform fracture zone subduction zone system and ne of a trench trench ridge triple junction a two pyroxene garnet granulite garnet amphibolite epidote amphibolite mafic metamorphic sole at the base of the ophiolite was generated roughly synchronously with the ophiolite by the metamorphism of mid ocean ridge basalt mafic rocks in the descending slab at about 10 kbar and quickly attached to the base of the overlying ophiolite during slab flattening and not by subduction zone extrusion the metamorphic sole is not a metamorphic aureole at the base of a hot obducting ophiolite plate slip vector triangles around the triple junction before collision and during obduction are constructed from the orientation of dykes in the sheeted complex and the trends of structures in the high to lower temperature parts of the sole and the obducted nappes of oceanic and continental margin rocks beneath the ophiolite linear structures in the sole amphibolites trend nnw the subduction direction those in the greenschist facies obducted oceanic and continental margin rocks trend wsw the obduction direction

the statistics of counting clasts in rudites a review with examples from the upper palaeogene of southern california usa the relative proportions of gravel sized particles of different lithology in rudaceous sedimentary rocks are generally determined in the field by clast counting clast counts are usually carried out qualitatively in order to assess sedimentary provenance however a review of the statistical aspects of clast counting suggests that this technique also can be applied quantitatively and to investigate a variety of other objectives during basin analysis geographical and stratigraphical changes in the relative proportions of clasts can be quantified statistically and used to characterize sediment dispersal patterns in space and time respectively statistical comparisons between clast assemblages can be used as a tool to match up rock units this approach may help to constrain tectonic or suspect terrane models or to document sediment recycling both counting and sampling errors contribute to the total probable error of a clast count sampling error results from the uneven distribution of clasts in outcrop perhaps caused by selective sorting counting error arises from a count of some number less than the total number of clasts in the population sampling and counting errors can be minimized by counting in closely spaced subsets and by counting a total of at least 400 clasts respectively thus a useful procedure is to count four closely spaced subsets of 100 each and combine the results for a total of 400 point counting should not be used because differences in particle size produce biased results a better method is to count all clasts above some minimum size within a specified area of outcrop analysis of upper palaeogene non marine conglomerates composing part of the sespe formation in california using confidence intervals hypothesis testing analysis of variance ratio analysis and varietal studies demonstrates that useful statistics can be derived by counting clasts

sedimentology and tectonic implications of cretaceous fan delta conglomerates queen charlotte islands canada the honna formation of coniacian age consists of several hundred metres of polymictic clast supported conglomerate associated with sandstone and mudstone five conglomerate facies are recognized ungraded beds inverse graded beds normal graded beds inverse to normal graded beds and parallel stratified beds these facies are interpreted as the deposits of subaqueous cohesionless debris flows and or high density turbidity currents the depositional environment was a deep water gravelly fan that draped a fault controlled basin margin slope the fan is inferred to have passed upslope directly into an alluvial fan unpreserved hence the name fan delta can be applied to the overall depositional system this type of fan delta of which the brae oilfield in the north sea is an example is defined here as a deep water fan delta the lack of a shelf is in marked contrast to other types of fan delta three facies associations are recognized in the honna formation subaqueous proximal fan conglomerates distal fan turbiditic sandstones and pro fan interfan mudstones with thin sandy turbidites the proximal fan is envisaged as an unchannelled gravel belt with a downslope length of at least 20 km such a long subaqueous gravel belt lacks a known modern analogue the distal fan was an unchannelled sandy extension of the proximal gravel belt it is postulated that the honna formation accumulated in a foreland basin which migrated westwards from the coast mountains where the wrangellia alexander terrane was colliding with north america in this model the honna fan delta was sourced by a west verging thrust sheet whose sole thrust was the sandspit fault immediately to the east deep water fan deltas appear to develop preferentially when eustatic sea level is relatively high so that the feeder alluvial fan is small and gravelly throughout in petroleum exploration and field development care should be taken to distinguish deep water fan deltas from base of slope canyon fed submarine fans because the two systems differ significantly in terms of coarse sediment distribution

waveform tomography reveals channeled flow at the base of the oceanic asthenosphere understanding the relationship between different scales of convection that drive plate motions and hotspot volcanism still eludes geophysicists using full waveform seismic tomography we imaged a pattern of horizontally elongated bands of low shear velocity most prominent between 200 and 350 kilometers depth which extends below the well developed low velocity zone these quasi periodic fingerlike structures of wavelength 2000 kilometers align parallel to the direction of absolute plate motion for thousands of kilometers below 400 kilometers depth velocity structure is organized into fewer undulating but vertically coherent low velocity plumelike features which appear rooted in the lower mantle this suggests the presence of a dynamic interplay between plate driven flow in the low velocity zone and active influx of low rigidity material from deep mantle sources deflected horizontally beneath the moving top boundary layer

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

bilelyeri group antalya complex deposition on a mesozoic passive continental margin south west turkey the bilelyeri group comprises complexly deformed mesozoic sedimentary rocks of continental margin affinities kumluca zone these are structurally intercalated between a coeval carbonate platform to the west bey daglari zone and late triassic ophiolitic rocks and sediments interpreted as emplaced marginal oceanic crust to the east godene zone four formations erected in the bilelyeri group record the later stages of continental rifting and the progressive development of part of a mesozoic passive continental margin the two late triassic formations the telektas tepe and the hatipalani formations are dominated by terrigenous clastic and calcareous clastic sediments including large detached blocks of reef limestone these rocks were laid down by mostly mass flow and turbidity flow into steep sided rift depressions organic reefs were constructed in bordering shallow seas while terrigenous clastic sediment was shed from exposed basement horsts thick sequences of mafic lavas were extruded norian in axial parts of the rift zones followed by a regional change to deposition of pelagic halobia bearing limestone this culminated in a major hiatus involving large scale sliding of shallow water limestones into deeper water the jurassic to early cretaceous derekoy formation mostly consists of siltstones radiolarian cherts and mudstones intercalated with redeposited limestones and black shales during this time parts of the margin were bordered by major offshore carbonate complexes constructed partly on basement fragments previously rifted off the parent continental areas black shales and reduced hemipelagic sediments were deposited in an elongate trough between the main platform and an offshore complex to the east some degree of margin reactivation in the early cretaceous is indicated by renewed deposition of turbiditic sandstone and chloritic clays in some distal sequences strong relative enrichment of manganese in some horizons is attributed to offshore volcanic exhalations subsequent regional subsidence in the mid to late cretaceous is suggested by a switch to predominantly calcareous pelagic sedimentation on the adjacent platform and the offshore massifs as well as on the bilelyeri margin tectonic disruption of the platform edge during the late cretaceous is implied by major redeposition of shallow water shelf limestones in proximal bilelyeri sequences the bilelyeri margin and the adjacent godene zone were tectonically deformed in latest cretaceous to early tertiary time and were thrust over the adjacent bey daglari platform in the early miocene viewed in an east mediterranean perspective the bilelyeri sequences were part of a locally north south trending segment of a regionally east west margin to a substantial oceanic area further south this segment apparently suffered significant strike slip deformation both during its construction and its later emplacement instructive comparisons can be made with other areas of the east mediterranean especially south west cyprus

u pb zircon crystallization age of the muslim bagh ophiolite enigmatic remains of an extensive pre himalayan arc distinguishing between these alternatives and unraveling the tectonics of this area cannot be fully understood until the timing of ophiolite formation is known in this paper we present u pb dating of zircons from plagiogranites within the sheeted dike component of the mus lim bagh ophiolite pakistan these critical new data provide clear evidence of the mag matic age of the intra arc or backarc origin of ophiolites correlated with himalayan arc sys tems and help resolve tethyan tectonics prior to the himalayan orogeny abstract the pre himalayan evolution of tethys is fundamental in interpreting the signifi cance of india s paleogene deceleration and the timing of the india eurasia collision the archetype continental collision that governs our understanding of collisional processes here we date zircons from plagiogranite sheeted dikes in the muslim bagh ophiolite that yield a u pb age of 80 2 1 5 ma this age is interpreted as dating the crystallization of plagiogranites that occur at the top of gabbro plutons as well as within sheeted dikes these represent highly fractionated magma chamber differentiates the plagiogranite s trace element abundances are typical of subduction petrogenesis and can be explained by the addition of slab derived components to a depleted mantle wedge muslim bagh ophiolite formation was coeval with the spongtang arc in a similar tectonic environment we interpret the chain of ophiolites within western pakistan as corollaries of the spongtang arc that formed 15 ma before they were obducted on the indian passive margin these form an extensive arc system that developed as oceanic crust in tethys foundered during india s migration north latest maastrichtian ophiolite sole formation and subsequent paleocene obduction of the arc onto india was the fi rst arc india collision a herald of the collisions to come later

application of multi source waveform inversion to marine streamer data using the global correlation norm conventional multi source waveform inversion using an objective function based on the least square misfit cannot be applied to marine streamer acquisition data because of inconsistent acquisition geometries between observed and modelled data to apply the multi source waveform inversion to marine streamer data we use the global correlation between observed and modelled data as an alternative objective function the new residual seismogram derived from the global correlation norm attenuates modelled data not supported by the configuration of observed data and thus can be applied to multi source waveform inversion of marine streamer data we also show that the global correlation norm is theoretically the same as the least square norm of the normalized wavefield to efficiently calculate the gradient our method employs a back propagation algorithm similar to reverse time migration based on the adjoint state of the wave equation in numerical examples the multi source waveform inversion using the global correlation norm results in better inversion results for marine streamer acquisition data than the conventional approach

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

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

elastic full waveform inversion of multicomponent ocean bottom cable seismic data application to alba field u k north sea elastic full waveform inversion of multichannel seismic data represents a data driven form of analysis leading to direct quantification of the subsurface elastic parameters in the depth domain previous studies have focused on marine streamer data using acoustic or elastic inversion schemes for the inversion of p wave data in this paper p and s wave velocities are inverted for using wide angle multicomponent ocean bottom cable obc seismic data inversion is undertaken using a two dimensional elastic algorithm operating in the time domain which allows accurate modeling and inversion of the full elastic wavefield including p and mode converted ps waves and their respective amplitude variation with offset avo responses results are presented from the application of this technique to an obc seismic data set from the alba field north sea after building an initial velocity model and extracting a seismic wavelet the data are inverted instages in the first stage the intermediate wavelength p wave v

multiparameter full waveform inversion of multicomponent ocean bottom cable data from the valhall field part 2 imaging compressive wave and shear wave velocities

nonlinear elastic waveform inversion of land seismic reflection data data from 53 shot records collected in a conventional land seismic reflection survey are inverted to obtain subsurface maps of short wavelength variations in elastic parameters impedance the inversion method employs a robust nonlinear iterative gradient algorithm which inverts waveform data thus there is no picking of travel times or amplitudes the algorithm is also computationnally expensive as it relies heavily upon elastic finite difference modeling in addition because a gradient search is employed to minimize the misfit between observed and modeled data we attempt to solve only the weakly nonlinear problem associated with the short wavelenghts of imedance information on the short wavelengths of impedance is mainly derived from amplitude variations of the data resolving the long wavelengths of velocity background is thought to be a highly nonlinear problem at least for waveform inversion and is not attempted herein for the inversion of this data set long wavelenghts have been derived from well logs located along the seismic reflection profile although the data set is dominated by unconverted p wave arrivals we obtain maps of the short wavelenghts of both p impedance and s impedance three well logs in the survey area confirm the validity of the p impedance map however no s velocity well log are available from this area there are channel sands of economic interest which have a thickness of approximately 10 m in one well and are very thin or absent in the other two wells the 10 m occurrence of channel sands is quite visible in both impedance maps we note that because inversion in three dimensions of a realistically sized data set is simply not possible on present day computers all modeling was performed in two dimensions and a rather crude conversion from spherical to cylindrical energy spreading was applied to the original field data before inversion other seismic reflection data in the survey area suggest that there is little lateral variation in the subsurface except for the channel sands thus we feel that a two dimensional inversion with energy compensation is justified

multiscale imaging of complex structures from multifold wide aperture seismic data by frequency domain full waveform tomography application to a thrust belt summary an application of full waveform tomography to dense onshore wide aperture seismic data recorded in a complex geological setting thrust belt is presented the waveform modelling and tomography are implemented in the frequency domain the modelling part is solved with a finite difference method applied to the visco acoustic wave equation the inversion is based on a local gradient method only the p wave velocity is involved in the inversion the inversion is applied iteratively to discrete frequency components by proceeding from low to high frequencies this defines a multiscale imaging in the sense that high wavenumbers are progressively incorporated in images the linearized waveform tomography requires an accurate starting velocity model that has been developed by first arrival traveltime tomography after specific pre processing of the data 16 frequency components ranging between 5 4 and 20 hz were inverted ten iterations were computed per frequency component leading to 160 tomographic models the waveform tomography has successfully imaged southwest dipping structures previously identified from other geophysical data as being associated with high resistivity bodies the relevance of the tomographic images is locally demonstrated by comparison of a velocity depth function extracted from the waveform tomography models with a coincident vertical seismic profiling vsp log available on the profile moreover comparison between observed and synthetic seismograms computed in the starting traveltime and waveform tomography models demonstrates unambiguously that the waveform tomography successfully predicts for wide angle reflections from southwest dipping geological structures this study demonstrates that the combination of first arrival traveltime and frequency domain full waveform tomographies applied to dense wide aperture seismic data is a promising approach to quantitative imaging of complex geological structures indeed wide aperture acquisition geometries offer the opportunity to develop an accurate background velocity model for the subsequent waveform tomography this is critical because the building of the macromodel remains an open question when only near vertical reflection data are considered

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

reconciling the geological history of western turkey with plate circuits and mantle tomography abstract we place the geological history since cretaceous times in western turkey in a context of convergence subduction collision and slab break off to this end we compare the west anatolian geological history with amounts of africa europe convergence calculated from the atlantic plate circuit and the seismic tomography images of the west anatolian mantle structure western turkish geology reflects the convergence between the sakarya continent here treated as eurasia in the north and africa in the south with the anatolide tauride block atb between two strands of the neotethyan ocean convergence between the sakarya and the atb started at least 95 90 myr ago marked by ages of metamorphic soles of ophiolites that form the highest structural unit below sakarya these are underlain by high pressure low temperature metamorphic rocks of the tavsanli and afyon zones and the oren unit which in turn are underlain by the menderes massif derived from the atb underthrusting of the atb below sakarya was since 50 ma associated with high temperature metamorphism and widespread granitic magmatism thrusting in the menderes massif continued until 35 ma after which there is no record of accretion in western turkey plate circuits show that since 90 ma 1400 km of africa europe convergence occurred of which 700 km since 50 ma and 450 km since 35 ma seismic tomography shows that the african slab under western turkey is decoupled from the african plate this detached slab is a single coherent body representing the lithosphere consumed since 90 ma there was no subduction re initiation after slab break off atb collision with europe therefore did not immediately lead to slab break off but instead to delamination of subducting lithospheric mantle from accreting atb crust while staying attached to the african plate this led to asthenospheric inflow below the atb crust high temperature metamorphism and felsic magmatism slab break off in western turkey probably occurred 15 myr ago after which overriding plate compression and rotation accommodated ongoing africa europe convergence slab break off was accommodated along a vertical ne trending subduction transform edge propagator step fault zone accelerating southwestward slab retreat of the aegean slab the se aegean slab edge may have existed already since early miocene times or before but started to rapidly roll back along the southeastern aegean step in middle miocene times penetrating the aegean region in the pliocene

the geochemistry of postkinematic mafic dike swarms and subophiolitic metabasites pozanti karsanti ophiolite turkey evidence for ridge subduction doleritic and gabbroic dike swarms cut the pozanti karsanti ophiolite and basal metamorphic sole but do not extend into the underlying melange or platform carbonates dike emplacement therefore postdated formation of the ophiolite and metamorphic sole but predated final obduction onto the tauride anatolide platform the dikes are compositionally similar to island arc basalts and basaltic andesites and were affected by retrograde static hydrothermal metamorphism over temperatures ranging from 900 c to below 450 c geochemical modeling of trace elements including rees show that the dikes are possibly fractionated products of multiple compositionally variable parental magmas the range of parental magmas is interpreted to represent variably mixed melt increments generated through polybaric fractional or continuous melting within a column of rising mantle material melt increments extracted from shallower parts of the melting column at lower pressures are more refractory and apparently pooled less efficiently than melt fractions generated from deeper sources and higher pressures amphibolite and greenschist facies metabasalt from the subophiolitic sole represent metamorphosed alkalic basalt and morb like basalt respectively the pozanti karsanti ophiolite probably constituted part of the fore arc mantle wedge directly above an intra oceanic subduction zone whereas the metamorphic sole represents material progressively transferred and accreted to the base of the ophiolite from the downgoing oceanic plate during subduction since late stage pre obduction dike swarms transect the metamorphic sole a probable subduction plane melt generation must have occurred below the wadati benioff zone and not in the overlying mantle wedge a probable source of parental liquids for the dikes may therefore be a subducting neo tethyan spreading center

trace element geochemistry of groundwater from quetta valley western pakistan this manuscript presents major minor and trace elements data for groundwater samples collected from wells tube wells springs and karezes from quetta valley quetta valley in pakistan has frequently experienced shortage of groundwater in recent years the water quality has had a sharp decline at many locations the study of groundwater resources in this valley is an attempt to understand the causes of and sources of contamination at several locations nitrate sulfate arsenic selenium chromium and nickel contamination has been determined the preliminary results indicate that these contaminations apparently result from a combination of rock alteration and mining activity in the area different water sources could have also contributed to the deterioration of the water quality of quetta valley this research provides the basis for future work which will involve detailed hydrological modeling and water quality studies

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

mapping in the oman ophiolite using enhanced landsat thematic mapper images abstract the large areal extent and complex nature of the terrain has meant that previous largely field based mapping programmes in the oman ophiolite have produced maps of internally inconsistent quality recognition of subtle changes and minor outcrops across the area of a 1 1 map sheet is possible in the field only by unrealistically exhaustive mapping by using parts of the short wavelength infrared spectrum landsat thematic mapper data have the capacity to capitalize on distinctions in the spectral reflectances of different rock types and their weathering products and to allow consistent mapping across the whole ophiolite decorrelation stretching of these data produces images in which it is possible to recognize variations in gabbro composition to identify small acidic gabbroic and ultramafic intrusions to discriminate the uppermost mantle from the deeper mantle to locate the moho precisely and to delineate gossans and areas subject to chloritic epidotic alteration off axis plutonism is more widespread and dispersed than previously appreciated the significance of certain faults is reassessed in the light of new insights provided by the imagery such data could be a valuable mapping tool in similarly exposed terrains in arid and semi arid regions even where already mapped at the 1 100 000 scale

successive shifts of the india africa transform plate boundary during the late cretaceous paleogene interval implications for ophiolite emplacement along transforms abstract the arabian sea in the nw indian ocean is a place where two major transform boundaries are currently active the owen fracture zone between india and arabia and the owen transform between india and somalia these transform systems result from the fragmentation of the india africa transform boundary which initiated about 90 myrs ago when the india seychelles block separated from madagascar to move towards eurasia therefore the geological record of the arabian sea makes it possible to investigate the sensitivity of a transform system to several major geodynamic changes here we focus on the evolution of the india africa transform system during the 47 90 ma interval we identify the late cretaceous 90 65 ma transform plate boundary along chain ridge in the north somali basin from 65 to 42 47 ma the india africa transform is identified at the chain fracture zone which crossed both the owen basin and the north east oman margin finally the transform system jumped to its present day location in the vicinity of the owen ridge these shifts of the india africa boundary with time provide a consistent paleogeographic framework for the emplacement of the masirah ophiolitic belt which constitutes a case of ophiolite emplaced along a transform boundary the successive locations of the india africa boundary further highlight the origin of the owen basin lithosphere incoming into the makran subduction zone

lithologic mapping in arid regions with landsat thematic mapper data meatiq dome egypt digital landsat thematic mapper tm data were evaluated for lithologic mapping capabilities over the meatiq dome area in the hyper arid eastern desert of egypt bi directional spectral reflectance data 0 4 2 5 m for powders of the major rock types exposed in the dome and published spectral reflectance data were used as guides in selecting tm band reflectance ratios that maximize discrimination of individual rock types on the basis of their respective mineralogies comparison of tm data with field and petrographic observations shows 1 increasing amounts of magnetite and other opaque minerals with low flat spectral reflectances decrease the ratio of tm band 5 1 55 to 1 75 to band 1 0 45 to 0 52 m 2 increasing amounts of hydroxyl bearing minerals with hydroxyl ion vibrational absorptions in tm band 7 wavelength region 2 08 to 2 35 m increase the ratio of tm band 5 to band 7 3 increasing amounts of fe bearing aluminosilicates that absorb in the band 4 wavelength region 0 76 to 0 9 m increase the product of the following two tm ratios band 5 to band 4 and band 3 0 63 to 0 69 m to band 4 and 4 thin 5 m desert varnish that covers many outcrops modulates but does not obscure the spectral reflectance signatures of the meatiq rocks the varnish consists of amorphous to poorly crystalline dioctahedral smectite iron oxides and or oxyhydroxides serpentinite mafic mylonite massive amphibolite quartzofeldspathic mylonite biotite schist and quartz phyllonite were mapped on the basis of their unique values in one or more of the three ratio images whereas coarse and fine grained granites granite gneiss and tonalite with similar mineralogies and tm band ratios were mapped as a group finer subdivisions were made where field traverses provided local verification results demonstrate that appropriate processing and presentation of landsat tm data can significantly augment field observations for lithologic mapping of large areas in arid regions

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

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

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

thrust loads and foreland basin evolution cretaceous western united states two dimensional modeling of loading during the formation of the idaho wyoming thrust belt shows that regional isostatic compensation by flexure of an elastic lithosphere is sufficient to control the formation of a foreland basin the flexural rigidity of the lithosphere is inferred to have been approximately 1023 nm 1030 dyne cm on the basis of palinspastic comparison of predicted downwarping due to the thrust plate loads to the shape of the sedimentary wedge on the west side of the cretaceous western interior seaway erosion of part of the uplifted thrust plates redistributed the load depositing it farther to the east thereby causing subsidence over a much wider area than could have been accomplished only by the loading by thrust plates paleotopography after major cretaceous thrust events was calculated the resulting mountainous terrain gentle alluvial plain and flat sea floor correspond well with the topography of the modern foreland thrust belt and basin system in the andes of south america and to paleogeographic reconstructions in the western united states thrust belt topography is controlled by the subsurface geometry of the thrust faults particularly the positions of ramp zones and by isostatic subsidence

the application of remote sensing techniques to the study of ophiolites abstract satellite remote sensing methods are a powerful tool for detailed geologic analysis especially in inaccessible regions of the earth s surface short wave infrared swir bands are shown to provide spectral information bearing on the lithologic structural and geochemical character of rock bodies such as ophiolites allowing for a more comprehensive assessment of the lithologies present their stratigraphic relationships and geochemical character most remote sensing data are widely available for little or no cost along with user friendly software for non specialists in this paper we review common remote sensing systems and methods that allow for the discrimination of solid rock lithologic components of ophiolite complexes and their structural relationships ophiolites are enigmatic rock bodies which associated with most if not all plate collision sutures ophiolites are ideal for remote sensing given their widely recognized diversity of lithologic types and structural relationships accordingly as a basis for demonstrating the utility of remote sensing techniques we briefly review typical ophiolites in the tethyan tectonic belt as a case study we apply integrated remote sensing studies of a well studied example the muslim bagh ophiolite located in balochistan western pakistan on this basis we attempt to demonstrate how remote sensing data can validate and reconcile existing information obtained from field studies the lithologic and geochemical diversity of muslim bagh are representative of tethyan ophiolites despite it s remote location it has been extensively mapped and characterized by structural and geochemical studies and is virtually free of vegetative cover moreover integrating the remote sensing data with ground truth information thus offers the potential of an improved template for interpreting remote sensing data sets of other ophiolites for which little or no field information is available

40ar 39ar dating of the emplacement of the muslim bagh ophiolite pakistan abstract the obduction related basal part of the muslim bagh ophiolite baluchistan pakistan and the underlying metamorphic sequence were studied structurally which demonstrated a wsw ene trending thrusting sequence for the initial obduction 40ar 39ar measurements on amphiboles and plagioclase from the subophiolitic metamorphic rocks and on plastically deformed and recrystallized dolerite samples from the base of the sheeted dyke complex give apparent ages between 70 7 5 0 and 65 1 4 1 ma interpreted as cooling ages dating approximately the formation of the plastic deformation and obduction the results indicate that the muslim bagh ophiolite represents a segment of ocean floor from the small and slow spreading ocean branch of the neo tethys located between the indo pakistani and the afro arabian plates the wsw ene oriented obduction of the muslim bagh ophiolite onto the indo pakistani continental margin occurred with the convergence of the neo tethys branch during the late cretaceous and before the tertiary collision of the indo pakistani plate with the eurasian plate

full 3d tomography for the crustal structure of the los angeles region we apply full 3d tomography f3dt to a regional dataset in the los angeles area in f3dt the starting model as well as the model perturbation is three dimensional and the sensitivity frechet kernels are computed using numerical schemes that account for the full physics of 3d wave propagation f3dt can account for the nonlinearity of structural inverse problem through iteration thus providing the most efficient means for assimilating seismic observations into dynamic ground motion models we have successfully applied a scattering integral si formulation of f3dt to improve a 3d elastic structure model the southern california earthquake center scec community velocity model version 3 0 cvm3 0 with lowest shear velocity clamped at 1 km sec in the los angeles region our data are time and frequency localized measurements of phase delay anomalies relative to synthetics computed from the 3d elastic starting model the frechet kernels for our measurements were computed by convolving the earthquake wave fields generated by point earthquake sources with the receiver green tensors rgts which are the spatial temporal fields produced by three orthogonal unit impulsive point forces acting at the receiver locations we inverted 7364 phase delay measurements of p and s body waves by using the lsqr method the revised 3d model laf3d provides substantially better fit to the observed waveform data than the 3d starting model to our knowledge this study is the first successful application of f3dt using real data in structural seismology

two dimensional full wavefield inversion of wide aperture marine seismic streamer data summary a 2 d full wavefield inversion method is presented for the processing of wide aperture data the diversity of information contained within such datasets may be handled in a complete manner by first matching the traveltimes of the main events and then progressing to waveform fitting of the data through explicit full wavefield modelling our wavefield inversion scheme is based upon a finite difference solution of the 2 d elastic wave equation in the time distance domain the strength of adopting such an approach is the ability to generate all possible wave types within a given 2 d model multiples converted waves etc and thus to simulate and accurately model complex seismic wavefields the aim of the inversion is to find the 2 d p wave velocity model that minimizes the least squared difference between the observed and synthetic data across the full range of offsets following extensive testing on synthetic data the wavefield inversion scheme has been applied to wide aperture real marine seismic streamer datasets we present results from the synthetic testing and the wavefield inversion of wide aperture real data out to 12 km offset that was recorded on a single streamer even though current computational restrictions allow only a small subsection of the data to be analysed these examples demonstrate the potential value of wide aperture 2 d full wavefield inversion

depositional setting and paleogeography of ordovician vinini formation central nevada the eugeoclinal strata of the ordovician vinini formation composes most of the roberts mountains allochthon rma its stratigraphy reconstructed in the roberts mountains can be precisely correlated throughout much of the rma and into coeval strata of the autochthonous miogeocline by means of graptolite and conodont biostratigraphy the vinini is a mixture of clastic lithologies with some limestone and greenstone coarse clastics characterized by well rounded and well sorted sands derived from cratonic sources occur in two separate intervals and provide critical data on depositional and paleogeographic setting the lower interval hundreds of meters thick was deposited in the latest ibexian earliest whiterockian and can be closely correlated throughout central nevada it is a mixture of quartz sandstone siltstone limestone and calcareous sandstone deposited by turbidity flows during a lowstand of sea level both eastern and western sources have been interpreted for these sands the upper interval is a prominent pure quartzite up to 20 m thick deposited as a prograding blanket of sand in the latest whiterockian earliest mohawkian it occurs in the vinini in the northern toquima range and in a parautochthonous sequence of transitional strata in the southern toiyabe range this interval represents the most basinward edge of the eureka quartzite more which was also deposited across the miogeocline the presence of sand of the eureka quartzite in the rma indicates that the basin in which the rma strata were deposited was immediately adjacent to the margin of north america in the ordovician less

aster capability in mapping of mineral resources of arid region a review on mapping of mineral resources of the sultanate of oman abstract advanced space borne thermal emission and reflection radiometer aster has exclusive capability to map minerals and ore deposits and able to discriminate rock types useful for geological applications especially the improved spectral and spatial resolutions of spectral bands of the sensor are well utilized by the exploration geologists working on arid region where the surface deposits are directly exposed to the sensor without disturbances of the vegetation several fruitful research studies have been carried out to map mineral resources in arid region with inaccessible rugged mountains and deserts area where it is difficult to do conventional geological mapping these were demonstrated and documented in the scientific publications using the aster spectral bands and image processing methods this study reviews scientific literatures published on mapping of the economic mineral resources of the sultanate of oman using aster and simples image processing methods

multiparameter full waveform inversion of multicomponent ocean bottom cable data from the valhall field part 1 imaging compressional wave speed density and attenuation multiparameter full waveform inversion fwi is a challenging quantitative seismic imaging method for lithological characterization and reservoir monitoring the difficulties in multiparameter fwi arise from the variable influence of the different parameter classes on the phase and amplitude of the data and the trade off between these in this framework choosing a suitable parametrization of the subsurface and designing the suitable fwi workflow are two key methodological issues in non linear waveform inversion we assess frequency domain visco acoustic fwi to reconstruct the compressive velocity vp the density or the impedance ip and the quality factor qp from the hydrophone component using a synthetic data set that is representative of the valhall oil field in the north sea we first assess which of the vp and vp ip parametrizations provides the most reliable fwi results when dealing with wide aperture data contrary to widely accepted ideas we show that the vp parametrization allows a better reconstruction of both the vp and ip parameters first because it favours the broad band reconstruction of the dominant vp parameter and secondly because the trade off effects between velocity and density at short to intermediate scattering angles can be removed by multiplication to build an impedance model this allows for the matching of the reflection amplitudes while the broad band velocity model accurately describes the kinematic attributes of both the diving waves and reflections then we assess different inversion strategies to recover the quality factor qp in addition to parameters vp and a difficulty related to attenuation estimation arises because on the one hand the values of qp are on average one order of magnitude smaller than those of vp and and on the other hands model perturbations relative to the starting models can be much higher for qp than for vp and during fwi in this framework we show that an empirical tuning of the fwi regularization which is adapted to each parameter class is a key issue to correctly account for the attenuation in the inversion we promote a hierarchical approach where the dominant parameter vp is reconstructed first from the full data set i e without any data preconditioning to build a velocity model as kinematically accurate as possible before performing the joint update of the three parameter classes during a second step this hierarchical imaging of compressive wave speed density and attenuation is applied to a real wide aperture ocean bottom cable data set from the valhall oil field several geological features such as accumulation of gas below barriers of claystone and soft quaternary sediment are interpreted in the fwi models of density and attenuation the models of vp and qp that have been developed by visco acoustic fwi of the hydrophone data can be used as initial models to perform visco elastic fwi of the geophone data for the joint update of the compressive and shear wave speeds

map view restoration of aegean west anatolian accretion and extension since the eocene 1 the aegean region greece western turkey is one of the best studied continental extensional provinces here we provide the first detailed kinematic restoration of the aegean region since 35 ma the region consists of stacked upper crustal slices nappes that reflect a complex paleogeography these were decoupled from the subducting african adriatic lithospheric slab especially since 25 ma extensional detachments cut the nappe stack and exhumed its metamorphosed portions in metamorphic core complexes we reconstruct up to 400 km of trench perpendicular ne sw extension in two stages from 25 to 15 ma the aegean forearc rotated clockwise relative to the moesian platform around euler poles in northern greece accommodated by extensional detachments in the north and an inferred transfer fault se of the menderes massif the majority of extension occurred after 15 ma up to 290 km by opposite rotations of the western and eastern parts of the region simultaneously the aegean region underwent up to 650 km of post 25 ma trench parallel extension leading to dramatic crustal thinning on crete we restore a detachment configuration with the mid cycladic lineament representing a detachment that accommodated trench parallel extension in the central aegean region finally we demonstrate that the sakarya zone and cretaceous ophiolites of turkey cannot be traced far into the aegean region and are likely bounded by a pre 35 ma n s fault zone this fault became reactivated since 25 ma as an extensional detachment located west of lesbos island the paleogeographic units south of the izmir ankara sava suture however can be correlated from greece to turkey

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

paleozoic evolution of southern margin of permian basin prior to late pennsylvanian time the permian basin of west texas was a part of the southern margin of the north american craton and was the site of shallow warm water carbonate deposition as the south american margin of gondwana gradually moved northwestward during late paleozoic time the oceanic floor deposits and overlying turbidite fan deposits between north america and south america became parts of large accretionary wedges of semiconsolidated sediments in a series of steps these wedges were folded and thrust toward the northwest against then finally onto the southern margin of north america these compressive steps caused the repeated piling up of the accretionary wedges to form rapidly eroding highlands on the cratonic margins repeated loading on the north american margin formed a series of elongate deep water depositional troughs fore deeps immediately north and west of the accretionary wedges and these received thick accumulations of turbidites the youngest of these deep basins include the northwestern part of the val verde basin to the north and the marfa basin to the west which received basinal deposits from within desmoinesian into early late permian time loading of the cratonic margin also resulted in renewed faulting along generally northwest to north trending older zones of weakness these zones are apparently of precambrian age on the craton the late paleozoic faults mainly had high angle to vertical fault planes and commonly had large components of horizontal displacement this fault system outlines the major uplifts and basins in the permian basin region the joining together of gondwana and euramerica across the marathon salient of the orogenic belt was essentially completed by mid wolfcampian time after that time the southern margin of the permian basin represented by the dugout and marathon allochthons and the diablo platform became a relatively stable tectonic area the glass mountains expose a series of north and northwest dipping cuestas of permian carbonate shelf and shelf edge deposits that accumulated on a platform constructed from these two allochthonous accretionary wedges these permian deposits prograded north and northwestward into the narrow hovey channel which connected the marfa basin with the southern end of the delaware basin carbonate reef growth finally restricted the inflow of marine water into the delaware basin near the end of late guadalupian time

alakir cay group antalya complex sw turkey a deformed mesozoic carbonate margin abstract the alakir cay group comprises complexly deformed mesozoic sedimentary rocks originally deposited along a passive carbonate margin the sediments now form a tectonically imbricated stack of thrust sheets kumluca zone emplaced westwards over a relatively autochthonous carbonate platform bey daglari zone the kumluca zone is bounded tectonically to the east by mafic and ultramafic rocks with related sediments godene zone representing oceanic crust produced during early stages of continental separation and originally forming the more distal part of the margin detailed mapping and structural analysis allow the thrust sheets to be pulled back to reconstruct a stretch of the carbonate margin about 10 km wide by 25 km long within the thrust sheets fragmentary basal sequences of quartzose sandstones hatip formation derived from the north were laid down during late triassic continental rifting subsequent late triassic halobia and radiolarian bearing calcilutites bozyer foramtion are comparable with peri platform deep water oozes found for example in the bahamas an end triassic hiatus involved substantial down margin sediment redeposition jurassic to early cretaceous sediments include both non calcareous and calcareous silts laid down together with radiolarites in deep water below the carbonate compensation depth karabuk formation an upward transition to cretaceous planktonic foraminiferal chalks is seen in some more proximal sequences tectonic disruption of the margin began in latest cretaceous time and ended with westward thrusting over the carbonate platform in the miocene small scale facies variation of the margin is illustrated by unstretching the thrust sheets and correlation of 33 measured logs particularly the sediments become more distal across the margin away from the carbonate platform along margin variation is especially evident in the thickness and composition of redeposited carbonates in the late triassic hemipelagic rocks comparison with other carbonate margin sequences in the antalya complex and elsewher implies that the alakir cay sediments represent deep water outer margin facies which lapped over adjacent oceanic crust more proximal redeposited carbonates are not seen perhaps due to overthrusting

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

dramatic pliocene quaternary subsidence of the southern rhodes basin and concomitant north tilting and uplift of the anaximander mountains the junction of hellenic and cyprus arcs eastern mediterranean sea abstract the anaximander mountains and the rhodes basin at the junction of cyprus and hellenic arcs are one of the tectonically most complex regions in the eastern mediterranean harmonically tilted messinian and the uppermost messinian pliocene successions across the northern and eastern margins of the rhodes basin showed that these regions experienced dramatic subsidence exceeding 1500 2500 ms 1125 1875 m 1500 m s 1 during the upper pliocene quaternary tilted upper pliocene quaternary growth strata wedges showing apparent north directed downlap along the northern foothills of the anaximander mountain suggested that this region experienced 1000 2500 ms 750 1125 m concomitant uplift the absence of faults showing extensional stratigraphic separations and the relative subsidence rates calculated using amount of tilting collectively suggest that the rhodes basin experienced sagging of its deeper basinal regions which is attributable to the loading effect of the building of the tauride mountains modified by the vertical axis rotations of the beydaglari block and the island of rhodes and the horizontal axis rotation of the anaximander mountain messinian and uppermost messinian pliocene were tectonically relatively quiet as shown by the harmonically structured and isopachous successions across the rhodes basin and anaximander mountain this interval coincides with the paleomagnetically determined 9 counterclockwise vertical axis rotation of the island of rhodes the dramatic subsidence observed within the rhodes basin and the concommitant uplift of the anaximander mountain and its western extension occurred broadly coincident with southeast tilting of the island of rhodes and its associated 500 600 m subsidence between 2 5 and 1 8 ma the northwest tilting between 1 5 and 1 1 ma and the associated re emergence of the southeastern coast the large counterclockwise rotation of the island of rhodes since 0 8 ma corresponds with the enormous subsidence observed across the northeastern sector of the rhodes basin which brought the shelf edge deltas from the near sea level to their present day depth of 1200 1500 m

evidence for late devonian movement within the roberts mountains allochthon roberts mountains nevada new evidence allows better understanding of the sequence of formations and emplacement events during the antler orogeny in the roberts mountains nevada lower to lower upper devonian strata were deformed and unconformably overlain by middle upper devonian siliceous shale and chert somewhere west of their present positions in the roberts mountains during a younger episode of deformation vinini group ordovician rocks were thrust over the devonian rocks that were still west of the present roberts mountains at the time of thrusting concurrent with this younger thrusting the webb formation accumulated at the toe of the moving allochthon in the early mississippian as the basal roberts mountains thrust stepped eastward it brought the whole allochthon to its present site above the webb sometime in the early mississippian

potential of esa s sentinel 2 for geological applications abstract sentinel 2 is esa s medium spatial resolution 10 60 m super spectral instrument aimed at ensuring data continuity for global land surface monitoring of landsat and spot several simulation studies have been conducted that show the potential of sentinel 2 for estimating biophysical and biochemical parameters such as leaf area index chlorophyll and nitrogen and spectral products such as the red edge position and ndvi time series providing data continuity for a number of other operational sensors this paper aims at simulating sentinel 2 products that are relevant to the geology and soil science community and we compare these to well established band ratio products from aster as the basis for the simulation we use airborne hyperspectral imagery from the hymap sensor which were spectrally and spatially resampled to the resolutions of aster and sentinel 2 using actual spectral response functions and pixel aggregate respectively the simulated image products demonstrate a good correspondence between aster and sentinel 2 vnir and swir bands a number of band ratios are proposed for sentinel 2 to derive the following products ferric iron ferrous iron laterite gossan ferrous silicate and ferric oxides these are compared to established band ratios of real aster data as well as simulated from hymap aster data and they correlate favourably investigating the spatial patterns reveals that there is a good match between the proposed sentinel 2 band ratio products and those of aster the resulting band ratio products are compared to the local geologic map of the imaged hydrothermal area the rodalquilar mining area cabo de gata volcanic field se spain it is shown that they support the existing conceptual geologic model of the epithermal deposit

3d prestack plane wave full waveform inversion prestack depth migration has been used for decades to derive velocity distributions in depth numerous tools and methodologies have been developed to reach this goal exploration in geologically more complex areas exceeds the abilities of existing methods new data acquisition and data processing methods are required to answer these new challenges effectively the recently introduced wide azimuth data acquisition method offers better illumination and noise attenuation as well as an opportunity to more accurately determine velocities for imaging one of the most advanced tools for depth imaging is full waveform inversion prestack seismic full waveform inversion is very challenging because of the nonlinearity and nonuniqueness of the solution combined with multiple iterations of forward modeling and residual wavefield back propagation the method is computer intensive especially for 3d projects we studied a time domain plane wave implementation of 3d waveform inversion we found that plane wave gathers