the crustal deformation revealed by gps and insar in the northwest corner of the tarim basin northwestern china the northwestern corner of the tarim basin hereinafter the noctb is surrounded by the pamir salient the south tian shan mountains and the tarim basin the tectonic settings of these three structures dominate the crustal deformation patterns and seismic events in the noctb and its adjacent regions we integrated the gps and insar measurements to derive a large scale three dimensional velocity map of the noctb the gps data obtained during 38 campaigns between 1992 and 2013 were used to derive a horizontal velocity field 149 envisat asar images observed along four satellite tracks between 2003 and 2011 were processed to get a line of sight rate map based on the small baseline subset time series analysis method and a homogeneous isotropic model finally we modeled the dip angle slip rate and locking depth of selected faults the results indicate that the crustal convergence is not uniformly distributed across the noctb more than 50 of the n s shortening is absorbed by the tian shan mountains in the southwest whereas the n s shortening rates are low and therefore the strain accommodations are smaller in the east of the noctb the vertical displacement rates in the noctb range from 2 to 3 mm year with different magnitudes in different areas the main uplift areas are located on the junction region between frontal mpt and the southwestern stt including the kazkeaerte fault aikenerte fault the southern artux fault and part areas in north of the kalping fault the main subsident areas are located on central belt of stt including the totgumbaz alpaleh fault nothern artux fault the southwestern karatieke fault and the north of puchang piqiang fault compared with the substantial n s shortening rate of 10 mm year the vertical rate across each fault ranges from approximately 1 to 1 mm year suggesting that vertical movement in noctb area is relatively moderate at present both the horizontal and vertical rates show obvious changes across the kazkeaerte fault and the kuzgong fault revealing that the basin mountain junction region between the pamir the tarim basin and the south tian shan mountains is subject to accumulate strain and triggers stronger earthquakes the kuzgong fault plays an important role of transforming the crustal movements between the southwestern end of the stt and the north frontal mpt the displacement field from geodetic observations could not find any evidence that the puchang piqiang fault is a geological boundary of kepingtage nappe the modeled fault geometry and slip rate imply that three faults in the noctb are slipping at 6 10 mm year along a decollement fault that dips at 19 27 and is locked at a shallow depth of 6 10 km whereas some other faults are undergoing a status of interseismic slip deficit

regional crustal thickness and precipitation in young mountain chains crustal thickness is related to climate through precipitation induced erosion along the andes the highest mountains and thickest crust 70 km occur at 25 south a region of low precipitation westerly winds warm passing over the atacama desert precipitation is modest in the high andes and eastward over the altiplano severe aridity hence low erosion rates helps to account for the elevated volcanogenic contractional arc and high internally draining plateau in its rain shadow weak erosion along the north central arc provides scant amounts of sediment to the chile peru trench starving the subduction channel subcrustal removal might be expected to reduce the crustal thickness but is not a factor at 25 south the thickness of the gravitationally compensated continental crust cannot reflect underplating and or partial fusion of sediments but must be caused chiefly by volcanism plutonism and contraction contrasting climate typifies the terrane at 45 south where moisture laden westerly winds encounter a cool margin bringing abundant precipitation the alpine landscape is of lower average elevation compared with the north central andes and is supported by thinner continental crust 35 km intense erosion supplies voluminous clastic debris to the offshore trench and vast quantities are subducted however the southern andean crust is only about half as thick as that at 25 south suggesting that erosion not subcrustal sediment accretion or anatexis is partly responsible for the thickness of the mountain belt the himalayas plus tibetan plateau the sierra nevada plus colorado plateau and the japanese islands exhibit analogous relationships between crustal thickness and climate

ice dams outburst floods and glacial incision at the western margin of the tibetan plateau a 100 k y chronology from the shyok valley karakoram some of the largest and most erosive floods on earth result from the failure of glacial dams while potentially cataclysmic ice dams are recognized to have repeatedly formed along ice sheet margins much less is known about the frequency and longevity of ice dams caused by mountain glaciers and their impact on landscape evolution here we present field observations and results from cosmogenic nuclide dating that allow reconstructing a 100 k y long history of glacial damming in the shyok valley eastern karakoram south asia our field observations provide evidence that asia s second longest glacier the siachen once extended for over 180 km and blocked the shyok river during the penultimate glacial period leading to upstream deposition of a more than 400 m thick fluvio lacustrine valley fill 10 be depth profile modeling indicates that glacial damming ended with the onset of the eemian interglacial and that the shyok river subsequently incised the valley fill at an average rate of 4 7 m k y 1 comparison with contemporary ice dammed lakes in the karakoram and elsewhere suggests recurring outburst floods during the aggradation period while over 25 cycles of fining upward lake deposits within the valley fill indicate impounding of floods from farther upstream despite prolonged damming the net effect of this and probably earlier damming episodes by the siachen glacier is dominated by glacial erosion in excess of fluvial incision as evidenced by a pronounced overdeepening that follows the glaciated valley reach strikingly similar overdeepened valleys at all major confluences of the shyok and indus rivers with karakoram tributaries indicate that glacial dams and subsequent outburst floods have been widespread and frequent in this region during the quaternary our study suggests that the interaction of karakoram glaciers with the shyok and indus rivers promoted valley incision and headward erosion into the western margin of the tibetan plateau

the 2008 nura earthquake sequence at the pamir tian shan collision zone southern kyrgyzstan this research was funded by dfg bundle tipage pak 443 the came project bundle tiptimon funded by the german federal ministry of education and research support code 03g0809 and gfz we acknowledge funding for the earthquake task force deployment by gfz and the hannover ruck reinsurance company

climate tectonics and the morphology of the andes large scale topographic analyses show that hemisphere scale climate variations are a first order control on the morphology of the andes zonal atmospheric circulation in the southern hemisphere creates strong latitudinal precipitation gradients that when incorporated in a generalized index of erosion intensity predict strong gradients in erosion rates both along and across the andes cross range asymmetry width hypsometry and maximum elevation reflect gradients in both the erosion index and the relative dominance of fluvial glacial and tectonic processes and show that major morphologic features correlate with climatic regimes latitudinal gradients in inferred crustal thickening and structural shortening correspond to variations in predicted erosion potential indicating that like tectonics nonuniform erosion due to large scale climate patterns is a first order control on the topographic evolution of the andes

climatic versus tectonic control on river incision at the margin of ne tibet 10be exposure dating of river terraces at the mountain front of the qilian shan 1 we document late pleistocene holocene aggradation and incision processes at the mountain front of the qilian shan an active intracontinental fold and thrust belt accommodating a significant portion of the india asia convergence the shiyou river cuts through a nne vergent fault propagation fold with miocene red beds in the core and pliocene quaternary growth strata on the northern forelimb south of the anticline miocene strata dip 20 ssw suggesting a similar orientation for the basal decollement after aggradation of an 150 m thick late pleistocene valley fill the shiyou river formed three terraces the highest terrace located 170 m above the river constitutes the top of the fill the other terraces are fill cut terraces their treads are located 130 105 m and 37 m above the river respectively the 10be exposure dating of the terraces suggests that river incision accelerated from 0 8 0 2 mm yr 1 to 10 mm yr 1 at 10 15 kyr we interpret fast holocene river incision as largely unrelated to tectonic forcing the late pleistocene incision rate of 0 8 0 2 mm yr 1 places an upper limit of 2 2 0 5 mm yr 1 on the horizontal shortening rate assuming that incision is solely caused by rock uplift above a decollement dipping 20 however the actual shortening rate may lie between 2 2 mm yr 1 and zero because deformation of the terraces and the valley fill cannot be unequivocally demonstrated our estimate is consistent with the bulk shortening rate of 5 10 mm yr 1 across several faults in ne tibet derived from neotectonic and gps data although in case of the shiyou river holocene deformation is barely discernible owing to intense climate induced river incision

late eocene palaeogeography of the proto paratethys sea in central asia nw china southern kyrgyzstan and sw tajikistan

cenozoic crustal shortening between the pamir and tien shan and a reconstruction of the pamir tien shan transition zone for the cretaceous and palaeogene the magnitude of the late cenozoic crustal shortening during convergence of the pamir and tien shan was determined using a contemporary pattern consisting of facies zones palaeomagnetic data regarding the rotation of tectonic units and data on the structure of the tadjik depression by late cenozoic cretaceous and palaeogene facies zones were cut by the vakhsh trans alay overthrust and darvaz strike slip faults and a significant part of the cretaceous palaeogene tadjik basin was overthrust by the pamir massif the sediments of easternmost part of the basin are preserved in the tarim depression the facies zones of the southern slope of the afghan tadjik basin were deformed and moved northward a pattern of facies zones indicates a convergence between the pamir and tien shan over a distance of 300 400 km a number of cross sections through the tadjik depression were used to establish the structure before folding a rotation of tectonic units indicated by structural data conforms to the angles of rotation as determined in palaeomagnetic studies the data suggest 300 km of convergence between the pamir and tien shan stratigraphic lithological structural and palaeomagnetic data formed the basis for the construction of the palinspastically restored palaeogeographic and sedimentologic environments for the tadjik shallow sea basin which was situated between the pamir and tien shan before their convergence in the late cenozoic the maps were constructed for the eight stratigraphic levels of the cretaceous and palaeogene the tadjik sea was a bay in the enormous turan sea in the early aptian this bay was located in what is now the afghan tadjik basin in late cretaceous the eastern shore of the bay lay 600 700 km further eastward and in the eocene marine environments extended even further eastward but after the rupelian continental environments occupied all of this region 2000 elsevier science b v all rights reserved

exhumational history of the north central pamir 1 the pamir plateau forms a prominent tectonic salient along the western end of the tibet tarim margin despite its tectonic significance relatively little is known about the timing of major cenozoic tectonic events in the pamir here we present new apatite and zircon u th he ages bulk rock geochemistry and al in hornblende barometry results from the karakul graben a prominent north south oriented rift basin located 50 km south of the main pamir thrust although cooling ages do not record the onset of extension graben bounding normal faults provide exposures of otherwise slowly eroding rocks which record two cenozoic thermal events existing geochronology and new results suggest that granitic rocks in the karakul region were shallowly emplaced cooled very quickly through 300 c and have experienced less than 10 km of exhumation since the late triassic a long period of relatively slow exhumation throughout much of the late mesozoic and cenozoic was punctuated by two periods of accelerated exhumation during the middle eocene 50 40 ma and early miocene 25 16 ma we interpret the first period of accelerated exhumation as a result of tectonic uplift and subsequent erosion due to the northward propagation of the india asia collision we attribute the second period of rapid exhumation to a renewed phase of tectonism and plateau uplift in the pamir perhaps related to a break off event along the down going indian plate at 25 ma or to the onset of slip along the nascent karakoram fault

bioclastic carbonate sediments on the southwestern svalbard shelf the poleward continuation of one of the largest known arctic carbonate factories the western spitsbergenbank of the barents sea has been surveyed along the narrow sw svalbard shelf on this shelf formation of cold water carbonate sediments occurs under glaciomarine environmental conditions mya truncata and hiatella arctica colonized a soft glacio marine diamicton 3000 6000 years after the final retreat of the icedome from the sw svalbard shelf since 2600 yr b p an increase of along shelf bottom currents washed out the fine terrigenous deposits leaving behind a shelly lag deposit and winnowed boulders on a morainic shelf topography the most favourable depth interval promoting the establishment of an amalgamated bioclastic blanket is located in 50 80 m water depth in this interval strong bottom currents prevent sedimentation thus facilitating colonisation of filter feeding benthic communities dominated by balanus balanus and chlamys islandica additional skeletal components are supplied by echinoderms bryozoans serpulids brachiopods and gastropods in shallower water depths carbonate production is hampered by intense iceberg scouring and release of ice rafted debris from the still glaciated hinterland of svalbard in deeper water 80 m olive grey muds with dispersed pebbles rich in benthic foraminiferans clinocardium ciliatum and taxodont bivalves are present on all surveyed shelf banks the deepest unit is a blue mud in water depths 120 m with benthic foraminiferans taxodont bivalves and sipunculids compared to spitsbergenbank carbonate production is much more restricted and impoverished on the sw svalbard shelf but is still an instructive modern example for the formation of skeletal carbonates resting on tillites in the geological record

a model for drowned terrestrial habitats with associated archeological remains in the northwestern gulf of maine usa abstract marine geophysical techniques and geological measurement of sea level change allow detailed mapping of seafloor archeological sites and development of models in the northwestern gulf of maine the lowstand of sea level is only at 60 m depth but a prolonged stasis during the late quaternary sea level rise herein termed the slowstand occurred between 11 500 and 7500 calibrated years before present cal yr bp at depths of 15 25 m this slowdown caused substantial erosion of glacial deposits and formed terrestrial beaches wetlands and lakes these landforms attracted people whose tools were later discovered during present day scallop fishing activities our study areas at the green islands and bass harbor are within the lowstand and slowstand depth ranges but at highly exposed and sheltered sites respectively the green islands site has lost most of its former terrestrial sediment and there is no longer any context for recovered artifacts at the protected bass harbor site the remains of eroded moraines are associated with drowned spits and a former lacustrine estuarine basin cores at the bass harbor location encountered freshwater peat deposits and numerous shallow subtidal shell and plant fossils all deposited during the slowstand the two most important controls on the preservation of terrestrial landforms and associated human artifacts in the northwestern gulf of maine are the rate of sea level rise and degree of shelter of the site from waves

3 d seismic structure of kii peninsula in southwest japan evidence for slab dehydration in the forearc abstract kii peninsula is located in the forearc region of southwest japan and has distinct structural and tectonic features characterized by high seismicity in the crust and the subducting philippine sea slab high surface heat flow high 3he 4he isotopic ratio and a local change in the geometry of the subducting slab we have tried to determine detailed 3 d p and s wave velocity structures of this region using a large number of high quality arrival time data recorded by dense seismic networks on the japan islands from the obtained seismic velocities we further estimated 3 d distributions of poisson ratio crack density saturation rate and porosity parameter in the study area our results show significant heterogeneities in the crust and upper mantle wedge characterized by low seismic velocities high poisson ratio high values of crack density saturation rate and porosity these results suggest the existence of fluids in the crust and mantle wedge resulting from the dehydration of the subducting philippine sea slab which can explain the observed geophysical and geochemical features in kii peninsula

building and testing an a priori geophysical model for western eurasia and north africa we construct and evaluate a new three dimensional model of crust and upper mantle structure in western eurasia and north africa wena extending to 700 km depth and having 1 parameterization the model is compiled in an a priori fashion entirely from existing geophysical literature specifically combining two regionalized crustal models with a high resolution global sediment model and a global upper mantle model the resulting wena1 0 model consists of 24 layers water three sediment layers upper middle and lower crust uppermost mantle and 16 additional upper mantle layers each of the layers is specified by its depth compressional and shear velocity density and attenuation quality factors q p and q s the model is tested by comparing the model predictions with geophysical observations including crustal thickness surface wave group and phase velocities upper mantle n velocities receiver functions p wave travel times waveform characteristics regional 1 d velocities and bouguer gravity we find generally good agreement between wena1 0 model predictions and empirical observations for a wide variety of independent data sets we believe this model is representative of our current knowledge of crust and upper mantle structure in the wena region and can successfully be used to model the propagation characteristics of regional seismic waveform data the wena1 0 model will continue to evolve as new data are incorporated into future validations and any new deficiencies in the model are identified eventually this a priori model will serve as the initial starting model for a multiple data set tomographic inversion for structure of the eurasian continent

the alichur dome south pamir western india asia collisional zone detailing the neogene shakhdara alichur syn collisional gneiss dome complex and connection to lithospheric processes neogene syn collisional extensional exhumation of asian lower middle crust produced the shakhdara alichur gneiss dome complex in the south pamir the 1 km thick mylonitic brittle top nne normal sense alichur shear zone asz bounds the 125 25 km alichur dome to the north the shakhdara dome is bounded by the 4 km thick mylonitic brittle top sse south pamir normal sense shear zone spsz to the south and the dextral gunt wrench zone to its north the alichur dome comprises cretaceous granitoids gneisses cut by early miocene leucogranites its hanging wall contains non weakly metamorphosed rocks the 22 17 ma alichur dome injection complex leucogranites transition from foliation parallel centimeter to meter thick sheets within the asz into discordant intrusions that may comprise half the volume of the dome core secondary fluid inclusions in mylonites and mylonitization temperature constraints suggest alichur dome exhumation from 10 15 km depth thermochronologic dates bracket footwall cooling between 410 130 c from 16 4 ma tectonic cooling exhumation rates 42 c myr 1 1 km myr contrast with erosion dominated rates in the hanging wall 2 c myr 0 1 km myr dome scale boudinage oblique divergence of the asz and spsz hanging walls and dextral wrenching reflect minor approximately e w material flow out of the orogen we attribute broadly southward younging extensional exhumation across the central south pamir between 20 4 ma to i mostly northward foreland directed flow of hot crust into a cold foreland during the growth of the pamir orocline and ii contrasting effects of basal shear related to underthrusting indian lithosphere enhancing extension in the underthrust south pamir and inhibiting extension in the non underthrust central pamir

a new global crustal thickness map an up to date global compilation of crustal thickness and pn velocity values from published seismic refraction and surface wave data has been created from 297 referenced sources a total of 2508 crustal thickness and 1806 pn velocity values have been selected this represents a significant expansion of previous compilations the inclusion of surface wave data results in a more uniform coverage of the earth s surface than is possible by using only published refraction data the crustal thickness data are contoured on a global van der grinten projection this compilation currently resides in a computer data base and is available on computer compatible tape recommendations for improvement in form and content will be welcomed as periodic updates are anticipated

drainage systems and the development of normal faults an example from pleasant valley nevada abstract drainage systems in regions of active extension contain information about fault zone structure and development and particularly about the lateral growth of individual fault segments that is difficult to obtain by more conventional means such as the dating of sedimentary material we investigate drainage fault interaction in pleasant valley nevada where a large normal faulting earthquake occurred in 1915 we find geomorphological evidence for a propagation increase in length of several km at both ends of one of the 1915 fault segments at one end we estimate the propagation rate to be about 50 m per earthquake this estimate is uncertain but is within the range predicted by theoretical models of fault growth drainage along the axes of half graben in this region may be influenced by the spacing of tilted fault blocks the highest valleys are also the narrowest whether the axial streams succeed in reaching lower neighbouring sinks depends on whether sedimentation rates are able to keep basins filled to the levels of the basement highs that separate half graben of opposite polarity a knowledge of modern drainage fault interactions may help predict drainage systems and the position of potential syn rift reservoir sediments in older extensional terrains where fault configurations but not facies distributions are known from seismic reflection surveys

cenozoic uplift and subsidence in the north atlantic region geological evidence revisited abstract the topographic evolution of the passive margins of the north atlantic during the last 65 myr is the subject of extensive debate due to inherent limitations of the geological geomorphological and geophysical methods used for studies of uplift and subsidence we have compiled a database of sign time and amplitude where possible of topographic changes in the north atlantic region during the cenozoic 65 0 ma our compilation is based on published results from reflection seismic studies aft apatite fission track studies vr vitrinite reflectance trends maximum burial sediment supply studies mass balance calculations and extrapolation of seismic profiles to onshore geomorphological features the integration of about 200 published results reveal a clear pattern of topographic changes in the north atlantic region during the cenozoic 1 the first major phase of cenozoic regional uplift occurred in the late palaeocene early eocene ca 60 50 ma probably related to the break up of the north atlantic between europe and greenland as indicated by the northward propagation of uplift it was preceded by middle palaeocene uplift and over deepening of some basins of the north sea and the surrounding areas 2 a regional increase in subsidence in the offshore marginal areas of norway the northern north sea the northern british isles and west greenland took place in the eocene ca 57 35 ma 3 the oligocene and miocene 35 5 ma were characterized by regional tectonic quiescence with only localised uplift probably related to changes in plate dynamics 4 the second major phase of regional uplift that affected all marginal areas of the north atlantic occurred in the plio pleistocene 5 0 ma its amplitude was enhanced by erosion driven glacio isostatic compensation despite inconclusive evidence this phase is likely to be ongoing at present

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

new space geodetic constraints on the distribution of deformation in central asia abstract results from repeated measurements across a 90 sites global positioning system network in central asia provide direct evidence of current high rates of tectonic deformation far north of the india eurasia suture zone the data help to quantify both the partitioning of deformation within the seismically active tien shan and northern pamirs as well as the ongoing rotation of virtually undeformed blocks such as the tarim with respect to stable eurasia the nnw to sse shortening rates derived from the computations reach values of 23 3 mm yr 1 over the ranges studied suggesting that regional deformation rates have increased considerably within the study area since the onset of cenozoic shortening 20 25 myr ago

late cenozoic extension and crustal doming in the india eurasia collision zone new thermochronologic constraints from the ne chinese pamir 1 the northward motion of the pamir indenter with respect to eurasia has resulted in coeval thrusting strike slip faulting and normal faulting the eastern pamir is currently deformed by east west oriented extension accompanied by uplift and exhumation of the kongur shan 7719 m and muztagh ata 7546 m gneiss domes both domes are an integral part of the footwall of the kongur shan extensional fault system kes a 250 km long north south oriented graben why active normal faulting within the pamir is primarily localized along the kes and not distributed more widely throughout the orogen has remained unclear in addition relatively little is known about how deformation has evolved throughout the cenozoic despite refined estimates on present day crustal deformation rates and microseismicity which indicate where crustal deformation is presently being accommodated to better constrain the spatiotemporal evolution of faulting along the kes we present 39 new apatite fission track zircon u th sm he and 40ar 39ar cooling ages from a series of footwall transects along the kes graben shoulder combining these data with present day topographic relief 1 d thermokinematic and exhumational modeling documents successive stages rather than synchronous deformation and gneiss dome exhumation while the exhumation of the kongur shan commenced during the late miocene extensional processes in the muztagh ata massif began earlier and have slowed down since the late miocene we present a new model of synorogenic extension suggesting that thermal and density effects associated with a lithospheric tear fault along the eastern margin of the subducting alai slab localize extensional upper plate deformation along the kes and decouple crustal motion between the central western pamir and eastern pamir tarim basin

quaternary extension in southern tibet field observations and tectonic implications we summarize evidence for quaternary and active faulting collected in the field during three sino french expeditions to southeastern tibet 1980 1982 detailed mapping of quaternary and active faults as well as microtectonic measurements indicate that normal faulting has been the dominant tectonic regime north of the himalayas in the last 2 0 5 m y the maximum horizontal principal stress in south tibet appears to be only the intermediate principal stress 2 1 being vertical south of the chord joining the eastern and western syntaxes of the himalayan arc extensional strains are principally localized within seven regularly spaced rift zones three of which have been studied in some detail the extension direction is determined to be n96 e 7 mainly from statistical averaging of strikes of newly formed normal faults throw rates on normal faults are evaluated for different time spans 2 0 5 m y 60 40 kyr and 10 2 kyr b p using structural and topographic reliefs as well as synglacial and postglacial vertical offsets the rate of quaternary extension is about 1 m y 1 along an 1100 km long ese traverse across south tibet this corresponds to a spreading rate of 1 0 6 cm yr this rate and the divergent horizontal projections of slip vectors of earthquakes along the himalayan front constrain the rate at which rigid india underthrusts southern tibet to be 2 1 cm yr although most of the normal faults appear to be independent of and nearly orthogonal to the e w mesozoic tertiary tectonic fabric the yadong gulu rift appears to be guided for over 130 km by the older oblique ne sw nyainqentanglha range and fault zones along it this reactivated zone is the most prominent left lateral strike slip fault system in se tibet excepting this zone and the vicinity of the se extremity of the karakorum fault quaternary strike slip faulting is rare in south tibet i e south of the chord between the syntaxes of the himalayan arc north of the chord the tectonic style is different there minor conjugate strike slip faulting is widespread and appears to control quaternary normal faulting which is more diffuse and subdued than in south tibet along the chord the presence of a major zone of active right lateral en echelon strike slip faults karakorum jiali fault zone probably reflects the greater facility of eastward extrusion in north central tibet in response to the northward push of india the eastern himalayan syntaxis may be an obstacle to such extrusion movements south of the chord

textural and compositional characterization of recent sediments along a paraglacial estuarine coastline maine usa abstract textural and mineralogical characteristics of bottom sediments collected from the lower kennebec river estuary maine and adjacent nearshore region were used to differentiate subtidal sedimentary environments five depositional environments defined on the basis of bottom morphology bathymetry and dominant sedimentary processes estuarine channel channel margin outer bar shoreface and offshore possess distinct sedimentological characteristics trends in textural characteristics of these environments and those along the adjacent barrier beach include 1 systematic decrease in mean grain size from the estuarine channel to the offshore facies 2 similarity between the outer bar and estuarine channel sands 3 increase in sediment sorting from the channel margin and offshore to shoreface facies and 4 fining of the low tide terrace beachface and berm samples away from the bar welding region the fine grained nature of the offshore facies is the result of deposition of suspended sediment delivered to the coast during large flood events whereas the coarse fraction is contributed through the attrition of carbonate tests of the local macrofauna results of compositional analyses reveal 1 a decrease in shell fragments from the estuarine channel 50 to the offshore

multiple origins of large hummock deposits in alai valley northern pamir implications for palaeoclimate reconstructions abstract this paper interprets the origin of several of the largest hummocky landform assemblages in the alai valley northern pamir a formerly glaciated intermontane depression the vast hummocky deposits in the koman suu and achik tash river catchments are found to be of two contrasting modes of formation glacial hummocks deposited during koman and lenin glaciers withdraw and avalanche hummocks produced during catastrophic koman and lenin rock avalanches the origins of the deposits we assessed through remote and field based geomorphological mapping as well as sedimentological investigations which included clast analysis and the identification of micro scale agglomerates indicative of rock avalanche emplacement both the koman and lenin rock avalanches were large catastrophic events with run outs of 34 and 24 km respectively and a volume over 1 109 m3 each that occurred subsequent to glacier withdrawal from the area the complex conditions on the moment of the rock avalanche emplacement promoted unusual deposits geomorphology and extensive run outs the landslide landforms formed over the pre existing glacial hummocks and fluvial deposits and are geomorphologically and sedimentologically distinct from the larger glacial hummocks the reconstruction of this sequence of events has implications for how hummock dating should be interpreted this research illustrates large scale catastrophic landsliding in the glacial environment and adds to the ongoing debate about the misidentification of rock avalanche deposits as of glacial origin and their relevance to palaeoclimatological and palaeoseismological reconstructions

intracontinental subduction beneath the pamir mountains constraints from thermokinematic modeling of shortening in the tajik fold and thrust belt american philosophical society american association of petroleum geologists geological society of america exxon mobil corporation

landscape evolution at extensional relay zones 1 it is commonly argued that the extensional relay zones between adjacent crustal scale normal fault segments are associated with large catchment fan systems that deliver significant amounts of sediment to hanging wall basins this conceptual model of extensional basin development while useful overlooks some of the physical constraints on catchment evolution and sediment supply in relay zones we argue that a key factor in the geomorphic evolution of relay zones is the interplay between two different timescales the time over which the fault array develops and the time over which the footwall catchment fan systems are established results of numerical experiments using a landscape evolution model suggest that in isolated fault blocks footwall catchment evolution is highly dependent on the pattern and rate of fault array growth a rapidly linked en echelon fault geometry gives rise to capture of relay zone drainage by aggressive catchment incision in the relay zone and to consequent increases in the rate of sediment supply to the hanging wall capture events do not occur when the fault segments are allowed to propagate slowly toward an en echelon geometry in neither case however are large relay zone catchment fan systems developed we propose several physical reasons for this including geometric constraints and limits on catchment incision and sediment transport rates in relay zones future research efforts should focus on the timescales over which fault array development occurs and on the quantitative variations in catchment fan system morphology at relay zones

shallow water pockmark formation in temperate estuaries a consideration of origins in the western gulf of maine with special focus on belfast bay abstract a systematic mapping program incorporating more than 5000 km of side scan sonar and seismic reflection tracklines in the western gulf of maine has identified more than 70 biogenic natural gas deposits occupying 311 km2 in nearshore muddy embayments many of these embayments also contain pockmark fields with some exhibiting geologically active characteristics including the observance of plumes of escaping fluids and sediment pockmarks hemispherically shaped depressions of various size and depths formed through fluid escape of gas and or pore water are sometimes found within or outside gas fields although many gas fields lack pockmarks altogether although the origin of the natural gas remains unclear if coastal environments at times of lower sea level were similar to the present numerous lake wetland valley fill and estuarine sources of organic rich material may have formed on the inner shelf if these deposits survived transgression and remain buried they are potential gas sources intensive mapping of the belfast bay pockmark field in 1998 produced the first nearly continuous side scan sonar mosaic of a gulf of maine pockmark field with a corresponding 3 dimensional geological model generated from seismic data statistical analysis of pockmark geometry gas deposit loci and subsurface evidence for gas enhanced reflectors suggest that gas migration from deeper lateral sources along permeable subsurface strata may be the mechanism for pockmark formation in areas lacking gas curtain seismic reflections the coarse grained transgressive ravinement unconformity between pleistocene glacial marine mud and holocene mud may act as a conduit for distributing methane to the field s margins

long river profiles tectonism and eustasy a guide to interpreting fluvial terraces along three rivers at the mendocino triple junction northern california strath cut and fill terraces have formed in response to tectonic and eustatic processes detailed surveying and radiometric dating at multiple sites indicate that lower reaches of the rivers are dominated by the effects of oscillating sea level primarily aggradation and formation of fill terraces during sea level high stands alternating with deep incision during low stands a eustasy driven deposi tional wedge extends tens of kilometers upstream on all rivers tapering to zero thickness this distance is greater than expected from studies of the effects of check dams on much smaller streams elsewhere due in part to the large size of these rivers however the change in gradient is nearly identical to other base level rise studies the depositional gradient is about half that of the original channel middle to upper reaches of each fiver are dominated by the effects of long term uplift primarily lateral and vertical erosion and formation of steep unpaired strath terraces exposed only upstream of the depositional wedge vertical incision at a rate similar to that of uplift has occurred even during the present sea level high stand along rivers with highest uplift rates strath terraces have steeper gradients than the modem channel bed and do not merge with marine terraces at the river mouth consequently they cannot be used to determine altitudes of sea level high stands strath formation is a continuous process of response to long term uplift and its occurrence varies spatially along a river depending on stream power and hence position upstream strath terraces are found only along certain parts of a coastal stream upstream of the aggradational effects of oscillating sea level and far enough downstream that stream power is in excess of that needed to transport the prevailing sediment load for a given size fiver the greater the uplift rate the greater the rate of vertical incision and consequently the less the like lihood of strath terrace formation and preservation

carbonate accumulation on the inner continental shelf of maine a modern consequence of late quaternary glaciation and sea level change abstract accumulations of skeletal carbonates are associated with late quaternary glacigenic sediments on the inner continental shelf of maine despite cold waters that are generally considered corrosive to calcium carbonate these shelly lithosomes up to 100 caco3 are confined to a small area in the vicinity of mt desert island a granitic massif on the deeply embayed coast exposure to waves is a strong control on sediment accumulation and varies due to orientation of the coast presence of numerous islands and extremely irregular bathymetry postglacial regression and subsequent transgression have greatly influenced the nature and distribution of surficial sediments on shallow parts of the shelf less than approximately 60 in depth on the basis of bathymetry bottom sedimen properties and geophysical characteristics five major physiographic zones are recognized nearshore basins shelf valleys outer basins rocky zones and nearshore ramps thick deposits of marine mud often charged with natural gas and pockmarked in places exist inside sheltered embayments nearshore basins and offshore below the influence of sea level changes outer basins shallower areas are dominated by rock outcrops rocky zones that support a prolific fauna of calcareous organisms such as barnacles echinoderms mussels and assorted bivalves and gastropods there are no significant sources of terrigenous sediments nearby in their absence abundant sand and gravel size shell fragments accumulate in rocky zones and adjacent nearshore ramps form a thin layer capping glacial marine sediments and till and supply sediment for two carbonate sand beaches these deposits provide a useful analog for deciphering the origins of some ancient limestone diamictite successions

structural and seismic evidence for intracontinental subduction in the peter the first range central asia this paper examines the stratigraphy structure and seismicity of the peter the first range an actively deforming foreland basin in soviet tadjikistan the range represents a highly deformed segment of a large intracontinental basin the tadjik depression which is being shortened in response to the cenozoic convergence between two orogenic massifs the pamir and the tien shan ranges the late jurassic to paleogene stratigraphy of the peter the first range includes more than 2 000 m of shallow marine to nonmarine sediments deposited under relatively quiescent conditions close to sea level in contrast the correlative units of the northernmost pamir directly south of the peter the first range show evidence of proximity to a major uplifted source area to the south these mesozoic early cenozoic strata are overlain by thick sequences of alluvial sandstone and conglomeratic units that coarsen upward through the neogene and record the progressive uplift of the pamir shortening within the peter the first range is recorded by kilometer scale isoclinal upright to over turned folds and imbricate north verging thrusts that emerge near the northern edge of the range and mark the active tectonic boundary with the tien shan most of the deformation appears to postdate the accumulation of the mio pliocene molasse the stratigraphy and structure of the region are best explained by a model of the mesozoic tadjik depression as an intracontinental foreland basin developed in a back arc position with respect to the active andean or collisional orogens located in northern afghanistan and the pamir seismicity in the region is dominated by earthquakes extending from the surface to 12 km depth apparently occurring within the deformed sediments of the peter the first range a subhorizontal zone of relatively low activity at this depth may mark the location of a basal detachment that underlies a structurally thickened sedimentary section this aseismic zone is in turn underlain by a south dipping belt of seismicity that extends from about 17 to 35 km depth and which can be traced updip to the seismogenic crystalline basement of the tien shan range to the north we interpret this south dipping structure as a zone of intracontinental subduction that may be an updip continuation of the enigmatic intermediate depth wadati benioff zone beneath the pamir range to the south

erosional processes as a control on the structural evolution of an actively deforming fold and thrust belt an example from the pamir tien shan region central asia the foreland of the pamir mountains displays an unusual orogenic topography in which an active north vergent thin skinned fold and thrust belt shows no topographic foredeep in advance of the thrust sheets instead the thrusts are impinging on a topographic barrier formed by the southern edge of the tien shan the deformation front of this thrust belt is coincident with a deeply incised river valley occupied by a large river the surkhob we suggest that this river played a key role in the evolution of this orogenic system by acting as a lateral conveyor belt for the transport of mass delivered to the deformation front by thrusting on the basis of reconnaissance geologic mapping it is clear that the present system developed in the late miocene or pliocene when the tien shan were uplifted within an existing foreland basin as the tien shan highland developed a longitudinal river within the foreland basin was trapped between the north directed thrusts and the tien shan highland with continued deformation the river was squeezed into a narrow canyon and since that time the system has been in an unusual equilibrium where thrusting acts to push the deformation front northward toward the tien shan but fluvial erosion and transport act to keep it in a constant position geologic relationships indicate that the vakhsh thrust the frontal thrust of the north directed system is now emerging on an erosion surface beneath a thin quaternary cover throughout the canyon suggesting that the river has been unable to keep pace with the tectonic mass flux and the thrust front as well as the river have been pushed northward across the beveled edge of what was originally the southern edge of the tien shan we suggest that the original deformation front of the tien shan now lies 10 km south of the present day topographic front of the tien shan beneath the north vergent vakhsh thrust as indicated by 1 a near vertical zone of intense basement seismicity the petrovsky seismic zone 2 an en echelon array of backthrusts along the south flank of the peter the first range and 3 footwall cutoff relationships of the vakhsh thrust system order of magnitude mass balance considerations based on sediment budgets support this conclusion but suggest that the mass imbalance may be small thus large volumes of material may have passed through the thrust fron and been carried out of the system by erosion a relationship that may account for the narrow 30 50 km wide band of deformed sedimentary rock between the pamir salient and the tien shan the present near equilibrium is maintained by long term tectonic transport rates and fluvial transport rates the latter closely linked to climate particularly precipitation thus although there is apparently a mass pile up within this system other systems of this type might show grossly different structural and stratigraphic relationships depending on the amount of rainfall and corresponding variations in rates of fluvial sediment transport similar settings can be recognized in the active thick skinned thrust systems of the tien shan and ancient systems like the laramide belt of western north america

a new procedure for gridding elevation and stream line data with automatic removal of spurious pits abstract a morphological approach to the interpolation of regular grid digital elevation models dems from surface specific elevation data points and selected stream lines is described the approach has given rise to a computationally efficient interpolation procedure which couples the minimization of a terrain specific roughness penalty with an automatic drainage enforcement algorithm the drainage enforcement algorithm removes spurious sinks or pits yielding dems which may be used to advantage in hydrological process studies the drainage enforcement algorithm has also been found to significantly increase the accuracy of dems interpolated from sparse but well chosen surface specific elevation data moreover it facilitates the detection of errors in elevation data that would not be detected by more conventional statistical means and forms a sound physical basis for cartographic generalization

fault kinematic and geomorphic observations along the north tehran thrust and mosha fasham fault alborz mountains iran implications for fault system evolution and interaction in a changing tectonic regime summary neighbouring faults can interact potentially link up and grow and consequently increase the seismic and related natural hazards in their vicinity despite evidence of quaternary faulting the kinematic relationships between the neighbouring mosha fasham fault mff and the north tehran thrust ntt and their temporal evolution in the alborz mountains are not well understood the ene striking ntt is a frontal thrust that delimits the alborz mountains to the south with a 2000 m topographic front with respect to the proximal tehran plain however no large instrumentally recorded earthquakes have been attributed to that fault in contrast the sigmoidally shaped mff is a major strike slip fault located within the alborz mountains sinistral motion along the eastern part of the mff is corroborated by microseismicity and fault kinematic analysis which documents recent transtensional deformation associated with nne ssw oriented shortening to better understand the activity of these faults on different timescales we combined fault kinematic analysis and geomorphic observations to infer the kinematic history of these structures our fault kinematic study reveals an early dextral shear for the ntt and the central mff responsible for dextral strike slip and oblique reverse faulting during nw oriented shortening this deformation regime was superseded by ne oriented shortening associated with sinistral oblique thrusting along the ntt and the central western mff sinistral strike slip motion along subsidiary faults in the central mff segment and folding and tilting of eocene to miocene units in the mff footwall continued thrusting along the ntt took place during the quaternary however folding in the hanging wall and sinistral stream offsets indicate a left oblique component and quaternary strike slip reactivation of the eastern ntt segment close to its termination this complex history of faulting under different stress directions has resulted in a composite landscape with inherited topographic signatures our study shows that the topography of the hanging wall of the ntt reflects a segmentation into sectors with semi independent uplift histories areas of high topographic residuals and apparent high uplift underscore the fault kinematics combined our data suggest an early mechanical linkage of the ntt and mff fault systems during a former dextral transpressional stage caused by nw compression during ne oriented shortening the ntt and mff were reactivated and incorporated into a nascent transpressional duplex the youngest manifestation of motion in this system is sinistral transtension however this deformation is not observed everywhere and has not yet resulted in topographic inversion

along strike and downdip segmentation of the pamir frontal thrust and its association with the 1985 mw 6 9 wuqia earthquake

modeling topographical density for geoid determinationthis article is one of a series of papers published in this special issue on the theme geodesy in geoid computation effects of real three dimensional topographic masses on the earth s gravity field must be accurately quantified and in the stokes helmert scheme replaced with effects of those masses condensed on the geoid the most comprehensive modern schemes for evaluation of topographical effects account for terrain effects use a spherical model of topography and incorporate two dimensionally varying models of topographical mass density in this contribution we employ a three dimensionally varying model of topographical density we use newton s integration to determine the direct topographical effect dte on gravity and primary indirect topographical effect pite on gravity potential lastly we apply stokes integration to calculate the dte pite and secondary indirect topographical effect site on geoidal height we focus here on validation of our results and demonstration of our software s capabilities we present results for the simple geometrical shape of a disc under various rotati

active tectonics of the pamirs and karakorum the source parameters of moderate to large sized earthquakes and the spatial distribution of earthquake hypocenters are used to investigate the active tectonics and three dimensional configuration of the subducted lithosphere in the pamir karakorum intracontinental convergence zone the continental collision has resulted in intense deformation in the upper crust the deformation is distributed over a broad area and is absorbed by thrust and strike slip faulting along the northern margin of the pamirs where the deformation due to continental collision is most intense the northern pamir thrust and several major fault zones mark the present boundary most of the earthquakes that occurred in these fault zones are shallow crustal events with focal mechanism solutions correlated with the tectonic features of the region along the pamir front thrust faulting dominates while on the western and eastern edges of the pamirs the style of deformation is characterized by oblique thrusting with a component of strike slip motion thrust type events beneath the tadjik depression indicate that both the sedimentary rocks and the basement are involved in shortening right lateral strike slip motion is observed on the eastern edge of the pamirs where they border the tarim basin and in the talas fergana kun lun fault zone a southward dipping seismic zone beneath the pamirs and karakorum indicates that the asian lithosphere has been subducted along the pamir front to a depth of at least 200 km this interpretation is consistent with published geological and geophysical data focal mechanism solutions of some intermediate depth events beneath the pamirs show strike slip faulting with approximately n s horizontally oriented p axes indicating that nearly horizontal compression at the intermediate depth is the predominant mode of deformation a 90 km deep event beneath the karakorum is interpreted as occurring in the subducted asian lithosphere the fact that the p axis of this event is oriented parallel to the descending plate suggests downdip compression within the asian lithosphere the overall tectonics of the region is interpreted as a consequence of the underthrusting asian lithosphere being impinged upon by the shallow northward underthrusting indian lithosphere

tropical climate instability the last glacial cycle from a qinghai tibetan ice core an ice core record from the guliya ice cap on the qinghai tibetan plateau provides evidence of regional climatic conditions over the last glacial cycle 36 cl data suggest that the deepest 20 meters of the core may be more than 500 000 years old the 18 o change across termination i is 5 4 per mil similar to that in the huascaran peru and polar ice cores three guliya interstadials stages 3 5a and 5c are marked by increases in 18 o values similar to that of the holocene and eemian 124 000 years ago the similarity of this pattern to that of ch 4 records from polar ice cores indicates that global ch 4 levels and the tropical hydrological cycle are linked the late glacial stage record contains numerous 200 year oscillations in 18 o values and in dust nh 4 and no 3 levels

late palaeozoic and meso cenozoic tectonic evolution of the southern kyrgyz tien shan constraints from multi method thermochronology in the trans alai turkestan alai segment and the southeastern ferghana basin abstract in this paper we present new geochronological and thermochronological data from the turkestan alai segment of the southern kyrgyz tien shan the ferghana basin transition and the trans alai pamir foreland in the southern and central parts of the alai range towards the alai valley mainly post collisional granitoids were targeted for zircon u pb dating by laser ablation inductively coupled plasma mass spectrometry la icp ms apatite fission track aft and apatite u th sm he ahe thermochronology these granitoids and their thermally metamorphosed contact aureole yielded middle permian zircon crystallization ages of 284 4 to 264 5 ma aft ages both using the traditional external detector approach as well as using la icp ms for these samples are constrained to the miocene and range between 22 3 1 1 and 8 4 0 3 ma while the ahe ages are somewhat younger between 12 5 0 8 and 5 0 0 3 ma this low temperature thermochronological data suggests an early miocene onset of denudation in this area in the tien shan orogen continuing through the miocene and pliocene this denudation is interpreted as a response to reactivation of the mountain belt in the framework of india eurasia convergence and specific to this region of the pamir tien shan interaction on the northern slopes of the alai range at the edge of the ferghana basin a late palaeozoic conglomerate yielded a reset early cretaceous aft age of 118 7 ma pointing to an older denudation event with respect to those identified in the southern and central parts of the alai range a mesozoic sediment sample from the same region only contains a late triassic age component of 223 ma mesozoic and cenozoic age components on the other hand are all detected in the cenozoic sediments of the trans alai range at the transition between the southern alai valley and the pamirs revealing several meso cenozoic denudation events in the adjoining basement source rocks the age components in these detrital apatites are 207 ma 75 ma 18 ma and 3 ma

oceanic style subduction controls late cenozoic deformation of the northern pamir orogen abstract the northern part of the pamir orogen is the preeminent example of an active intracontinental subduction zone in the early stages of continent continent collision such zones are the least understood type of plate boundaries because modern examples are few and of limited access and ancient analogs have been extensively overprinted by subsequent tectonic and erosion processes in the pamir it has been assumed that most of the plate convergence was accommodated by overthrusting along the plate bounding main pamir thrust mpt which forms the principal northern mountain and deformation front of the pamir however the synopsis of our new and previously published thermochronologic data from this region shows that the hanging wall of the mpt experienced relatively minor amounts of late cenozoic exhumation the pamir orogen as a whole is an integral part of the overriding plate in a subduction system while the remnant basin to the north constitutes the downgoing plate with the bulk of the convergence accommodated by underthrusting herein we demonstrate that the observed deformation of the upper and lower plates within the pamir alai convergence zone resembles highly arcuate oceanic subduction systems characterized by slab rollback subduction erosion subduction accretion and marginal slab tear faults we suggest that the curvature of the north pamir is genetically linked to the short width and rollback of the south dipping alai slab northward motion indentation of the pamir is accommodated by crustal processes related to this rollback the onset of south dipping subduction is tentatively linked to intense pamir contraction following break off of the north dipping indian slab beneath the karakoram

deep seated gravitational slope deformation dsgsd and slow moving landslides in the southern tien shan mountains new insights from insar tectonic and geomorphic analysis we investigated deep seated gravitational slope deformation dsgsd and slow mass movements in the southern tien shan mountains front using synthetic aperture radar sar time series data obtained by the alos palsar satellite dsgsd evolves with a variety of geomorphological changes e g valley erosion incision of slope drainage networks over time that affect earth surfaces and therefore often remain unexplored we analysed 118 interferograms generated from 20 sar images that covered about 900 km2 to understand the spatial pattern of the slope movements and to identify triggering parameters we correlated surface dynamics with the tectono geomorphic processes and lithologic conditions of the active front of the alai range we observed spatially continuous constant hillslope movements with a downslope speed of approximately 71 mm year 1 velocity our findings suggest that the lithological and structural framework defined by protracted deformation was the main controlling factor for sustained relief and consequently downslope mass movements the analysed structures revealed integration of a geological structural setting with the superposition of cretaceous paleogene alternating carbonatic and clastic sedimentary structures as the substratum for younger less consolidated sediments this type of structural setting causes the development of large scale gravity driven dsgsd and slow mass movement surface deformations with clear scarps and multiple crest lines triggered planes for large scale deep mass creeps and these were related directly to active faults and folds in the geologic structures our study offers a new combination of insar techniques and structural field observations along with morphometric and seismologic correlations to identify and quantify slope instability phenomena along a tectonically active mountain front these results contribute to an improved natural risk assessment in these structures

exhumation history of the western kyrgyz tien shan implications for intramontane basin formation the dextral talas fergana fault separates the western from the central tien shan recent work has shed light on the cenozoic evolution of the eastern and central tien shan much less attention has been paid to the western tien shan in this contribution we present new thermochronological ages for the fergana and alai ranges that combined with the available data set constrain the cenozoic exhumation history of the western tien shan following a tectonically quiet early cenozoic period we suggest an onset of exhumation at 25 ma this early onset was followed by a period of slower exhumation and in some areas minor reheating a final strong late miocene rapid cooling event is well represented in the western tien shan as in other sectors of the range the early onset of uplift of the western tien shan dissected the previously continuous westernmost parathethyan sea progressively isolating basins e g fergana tarim and alai basins in the central asian hinterland moreover the coeval timing of late miocene uplift along the length of entire tien shan implies that neither the pamir nor tarim can be the sole driver for exhumation of the entire range

the 2015 mw7 2 sarez strike slip earthquake in the pamir interior response to the underthrusting of india s western promontory the pamir orogen central asia is the result of the ongoing northward advance of the indian continent causing shortening inside asia geodetic and seismic data place the most intense deformation along the northern rim of the pamir but the recent 7 december 2015 mw7 2 sarez earthquake occurred in the pamir s interior we present a distributed slip model of this earthquake using coseismic geodetic data and postseismic field observations the earthquake ruptured an 80 km long subvertical sinistral fault consisting of three right stepping segments from the surface to 30 km depth with a maximum slip of three meters in the upper 10 km of the crust the coseismic slip model agrees well with en echelon secondary surface breaks that are partly influenced by liquefaction induced mass movements these structures reveal up to 2 m of sinistral offset along the northern low offset segment of modeled rupture the 2015 event initiated close to the presumed epicenter of the 1911 mw 7 3 lake sarez earthquake which had a similar strike slip mechanism these earthquakes highlight the importance of ne trending sinistral faults in the active tectonics of the pamir strike slip deformation accommodates shear between the rapidly northward moving eastern pamir and the tajik basin in the west and is part of the westward lateral extrusion of thickened pamir plateau crust into the tajik basin the sarez karakul fault system and the two large sarez earthquakes likely are crustal expressions of the underthrusting of the northwestern leading edge of the indian mantle lithosphere beneath the pamir

gps velocity field for the tien shan and surrounding regions 1 measurements at 400 campaign style gps points and another 14 continuously recording stations in central asia define variations in their velocities both along and across the kyrgyz and neighboring parts of tien shan they show that at the longitude of kyrgyzstan the tarim basin converges with eurasia at 20 2 mm yr nearly two thirds of the total convergence rate between india and eurasia at this longitude this high rate suggests that the tien shan has grown into a major mountain range only late in the evolution of the india eurasia collision most of the convergence between tarim and eurasia within the upper crust of the tien shan presumably occurs by slip on faults on the edges of and within the belt but 1 3 mm yr of convergence is absorbed farther north at the dzungarian alatau and at a lower rate with the kazakh platform to the west the tarim basin is thrust beneath the tien shan at 4 7 mm yr with respect to eurasia the ferghana valley rotates counterclockwise at 0 7 myr 1 about an axis at the southwest end of the valley thus gps data place a bound of 4 mm yr on the rate of crustal shortening across the chatkal and neighboring ranges on the northwest margin of the ferghana valley and they limit the present day slip rate on the right lateral talas ferghana fault to less than 2 mm yr gps measurements corroborate geologic evidence indicating that the northern margin of the pamir overthrusts the alay valley and require a rate of at least 10 and possibly 15 mm yr

mesozoic ophiolites sutures and arge scale tectonic movements in afghanistan abstract the tectonic history of afghanistan appears to be the result of successive accretion of fragments of gondwana to the active margin of laurasia since the end of the paleozoic the margin in afghanistan lies along the present herat and panjshir faults south of hindu kush swings around the central pamirs and can presumably be traced along the present western altyn tagh and kunlun faults in tibet north of this boundary paleozoic rocks have been deformed in the upper paleozoic whereas south of it there is no trace of the hercynian orogeny the first collision of gondwanian fragments with laurasia probably occurred in the early mesozoic along the hindu kush and kunlun to the south ophiolites along the panjao and pangong nu chiang sutures respectively in central afghanistan and central tibet testify for another suturing event in the upper jurassic or lower cretaceous the indus tsangpo suture between india and tibet corresponds in eastern afghanistan to two ophiolite subbelts near kabul and khost both ophiolite complexes have been emplaced between maestrichtian and lower eocene by choking of two northward dipping subduction zones after complete contact between the indian and asian continents was achieved presumably in the end of eocene the penetration of india into asia caused large scale intra continental shortening a large part of the shortening was accommodated by strike slip faulting along mesozoic and more ancient sutures central afghanistan in particular was extruded to the west along the herat suture by the protrusion of the pamir wedge it subsequently collided with the lut block

soils as indicators of the pleistocene and holocene landscape evolution in the alay range kyrgystan abstract soils derived from quaternary glacial glaciofluvial and aeolian deposits in the alay range kyrgystan were studied to reconstruct the pleistocene and holocene landscape evolution geomorphologic studies radiocarbon dating of a horizons in palaeosols and iron fractionation were undertaken during the last glacial maximum lgm the abramov glacier in the alay range advanced down the koksu valley to an altitude of 2500 m asl about 50 km from the modern snout ela lowering about 600 m in addition several frontal moraine complexes could be identified at the valley bottom of the koksu river between 3100 m asl and the modern glacier snout at 3650 m asl the complexes can be assigned to the following glacier advances late glacial ela lowering 200 300 m early holocene to end of late glacial younger dryas ela lowering about 110 m neoglacial ela lowering about 50 m and little ice age ela lowering about 50 m similar glacier advances could be reconstructed according to the soil development on the lateral moraines near the abramov glacier at 3600 4000 m asl determination of pedogenic iron oxides corroborated the morphologic and radiocarbon results

cenozoic paleo environmental evolution of the pamir tien shan convergence zone abstract the retreat of the tethys sea and the uplift of the tibetan plateau play the critical roles in driving asian climatic changes during the cenozoic in the pamir tien shan convergence zone over 3000 m of cenozoic successions consisting of marine deposits in the lower continental clay and fine sand in the middle and molasse in the upper part record the evolution of the tethys sea the asian aridification and the deformation of the pamir in this work the existing biostratigraphic subdivisions and new electronic spinning resonance dating results were used to assign ages to formations within the ulugqat section sedimentary facies analysis and multi proxy indices were used to reconstruct the paleo environmental evolution the results show 1 the pamir tien shan convergence zone has undergone progressive environmental changes from shallow marine before 34 ma to arid land at 23 ma and finally to inter mountain basin by 5 3 ma 2 the overall increase in mean size of grains decrease in redness in magnetic susceptibility and in proportion of the ultrafine component of the sediments studied revealed a long term strengthening in potential energy to transporting medium cooling and enhanced continental aridity respectively 3 the easternmost edge of the tethys sea prevailed in the western tarim basin from late cretaceous to early cenozoic and finally retreated from this region around the eocene oligocene transition which in turn strengthened the asian aridification 4 accumulation of molasse with an upper age of 1 ma suggests that the deformation front of the pamir migrated to this area at or before that time

formulation and validation of a global laterally varying topographical density model abstract the distribution of masses within topography is extremely important for the evaluation of a rigorous geoid model most present day models of topographical density are either determined via gravity field inversions or have too coarse a resolution to be useful on a regional level the ideal solution would be to have a 3 dimensional 3d density model but such a dataset does not currently exist and would be quite complicated and expensive to develop as a substitute a 2 dimensional 2d topographical density model is presented here through the application of a high resolution lithological map by assigning probable surface density values and error estimates to the lithologies based on geological data the global lithology model glim is transformed into a laterally varying topographical density model unb topodens this model is then validated against present day global and regional topographical density models apart from some water and ice covered regions the unb topodens model agrees with all regional and global models at our disposal with the differences all falling within the 95 confidence region associated with the unb topodens model unb topodens is the first laterally varying topographical density model with associated error estimates that spans the globe at a 30 x 30 resolution and is therefore extremely useful for investigations of the crust and mantle isostasy gravimetric studies and various other disciplines

climate driven sediment aggradation and incision since the late pleistocene in the nw himalaya india abstract deciphering the response of sediment routing systems to climatic forcing is fundamental for understanding the impacts of climate change on landscape evolution in the kangra basin northwest sub himalaya india upper pleistocene to holocene alluvial fills and fluvial terraces record periodic fluctuations of sediment supply and transport capacity on timescales of 103 to 105 yr to evaluate the potential influence of climate change on these fluctuations we compare the timing of aggradation and incision phases recorded within remnant alluvial fans and terraces with climate archives new surface exposure dating of six terrace levels with in situ cosmogenic 10be indicates the onset of incision phases two terrace surfaces from the highest level t1 sculpted into the oldest preserved alluvial fan af1 date back to 53 4 3 2 ka and 43 0 2 7 ka 1 t2 surfaces sculpted into the remnants of af1 have exposure ages of 18 6 1 2 ka and 15 3 0 9 ka while terraces sculpted into the upper pleistocene holocene fan af2 provide ages of 9 3 0 4 ka t3 7 1 0 4 ka t4 5 2 0 4 ka t5 and 3 6 0 2 ka t6 together with previously published osl ages yielding the timing of aggradation we find a correlation between variations in sediment transport with oxygen isotope records from regions affected by the indian summer monsoon during periods of increased monsoon intensity and post last glacial maximum glacial retreat aggradation occurred in the kangra basin likely due to high sediment flux whereas periods of weakened monsoon intensity or lower sediment supply coincide with incision

fault behavior and characteristic earthquakes examples from the wasatch and san andreas fault zones paleoseismological data for the wasatch and san andreas fault zones have led to the formulation of the characteristic earthquake model which postulates that individual faults and fault segments tend to generate essentially same size or characteristic earthquakes having a relatively narrow range of magnitudes near the maximum analysis of scarp derived colluvium in trench exposures across the wasatch fault provides estimates of the timing and displacement associated with individual surface faulting earthquakes at all of the sites studied the displacement per event has been consistently large measured values range from 1 6 to 2 6 m and the average is about 2 m on the basis of variability in the timing of individual events as well as changes in scarp morphology and fault geometry six major segments are recognized along the wasatch fault on the basis of the most likely number of surface faulting events 18 that have occurred on segments of the wasatch fault zone during the past 8000 years an average recurrence interval of 400 666 years with a preferred average of 444 years is calculated for the entire zone geologic data on the distribution of slip associated with prehistoric earthquakes and slip rates along the south central segment of the san andreas fault suggest that the m 8 1857 earthquake is a characteristic earthquake for this segment comparisons of earthquake recurrence relationships on both the wasatch and san andreas faults based on historical seismicity data and geologic data show that a linear constant b value extrapolation of the cumulative recurrence curve from the smaller magnitudes leads to gross underestimates of the frequency of occurrence of the large or characteristic earthquakes only by assuming a low b value in the moderate magnitude range can the seismicity data on small earthquakes be reconciled with geologic data on large earthquakes the characteristic earthquake appears to be a fundamental aspect of the behavior of the wasatch and san andreas faults and may apply to many other faults as well

dynamic earth system and ecological controls of rainfall initiated landslides abstract rainfall initiated landslides continue to inflict damages and loss of life throughout the world processes and mechanisms revealed from hydrological geomorphic geotechnical pedological geological hydrochemical and biological investigations have advanced our understanding of these effects on slope stability however the interactions amongst these processes and attributes as they affect the initiation and propagation of landslides are not as well understood too often landslide studies are conducted from only one or at most two of these perspectives moreover while precipitation and hydrology are recognized as dynamic influences the earth system and ecological effects are often assumed to be static we assess the interplay of these processes related to landslides triggered by positive pore water accretion and loss of soil suction each of these conditions arguably requires a different view on the processes that cause slope failure and predictive approaches this review starts from the perspective of dynamic adapting earth and ecological systems and discusses how these attributes relate to landslide initiation mode location and timing specifically the role that large and small scale preferential flow plays in both contributing to and mitigating instability is elucidated including effects of bedrock exfiltration we also examine how and under what conditions these pathways manifest in different soils lithology and landforms the multiple effects of rhizosphere processes on slope stability are discussed including root reinforcement evaporation from canopies and litter layers transpiration and the role of root structure affecting preferential flow paths rainfall initiated landslides involve highly dynamic hydrologic earth surface and ecological processes that persist over a range of spatial and temporal scales however guidance for overcoming these challenges has been elusive a conceptual framework is presented to shed light on these dynamic and interactive processes that should lend insights into why and when certain slopes fail during storms while other seemingly similar slopes do not fail such advances will benefit landslide hazard assessments and disaster responsiveness protocols

seismotectonic range front segmentation and mountain belt growth in the pamir alai region kyrgyzstan india eurasia collision zone the trans alai range along the northern perimeter of the pamir region of kyrgyzstan is at the northern edge of the india eurasia collision zone the range defines a section of main pamir thrust which is divided into eastern central and western segments that record differential absorption of plate convergence the 50 km long east west striking central fault segment of the main pamir thrust has dip slip thrust fault offsets with a minimum holocene dip slip rate of 6 mm yr and is linked to the other segments via northwest striking dextral transfer the western transfer faults are well characterized geomorphically and the westernmost records the predominant transition to north vergent thrusting along the western segment via north vergent low angle thrust faults rooted in a steeply south dipping dextral shear zone in contrast the eastern segment deformation is widely distributed and geomorphically less evident but the transfer also takes place in a structurally complex zone asymmetric offset of a regionally correlated terrace geomorphic zonation and the distribution of historic earthquakes suggest that the central segment is mechanically linked with the western segment but not with the eastern segment the progressive closure of the alai valley by the northward advance of thrusting exemplifies the annihilation of an intramontane basin if the high surface uplift rates implied by these geologic observations have been maintained for the last few million years they attest to the high level of tectonic activity and the recency of construction of the trans alai range

gravity anomalies over the ferghana valley central asia and intracontinental deformation gravity anomalies over the ferghana valley a deep sedimentary basin in the western tien shan differ from those expected for local airy isostatic equilibrium by 120 mgal and imply a deficit of mass beneath the basin equivalent to a moho deeper by 10 km than prevails where isostasy holds although the ferghana valley is underlain by thick mesozoic and cenozoic sediment measurements of density show that this material cannot account for the deficit of mass gravity anomalies over both the surrounding mountain belts and the kazakh platform farther north imply that local airy isostatic equilibrium is approached flexure of a relatively thin effectively elastic plate thickness 10 15 km loaded by the present topography can account for the range of bouguer anomalies of 50 to 450 mgal over these regions we infer that approximately north south shortening of the relatively thin lithosphere has created mountains north and south of the basin has warped the basement of the immediate surroundings of the basin up by folding the mantle lithosphere and has forced the basin floor down beneath the ferghana valley it appears that the preexisting thermal structure and variations in crustal thickness have dictated the styles and distribution of deformation in this region

modern nearshore cold temperate calcareous sediments in the troms district northern norway abstract during the past 6400 years rocky coastal platforms and outer fjord troughs in the troms district northern norway 70 n became sites of considerable production and deposition of skeletal carbonate in a cold temperate environment under arctic solar radiation conditions because of poleward heat transfer by the norwegian current along the eastern margin of the north atlantic ocean the cold temperate marine climate persists beyond the arctic circle in the shallow subtidal zone carbonate generation is confined to benthic macroalgal ecosystems along the wave exposed margins of the coastal platforms kelp forests provide habitats for numerous carbonate secreting organisms such as barnacles echinoids and bivalves kelp with attached calcareous organisms is involved in many redistributional processes such as rafting and phylloid drift reef growth of coralline algae together with maerl deposits and rhodolith pavements dominate in wave sheltered platform areas this windward leeward zonation of carbonate production along the rocky coasts reflects specific properties of coralline algae versus kelp to withstand physical disturbances of episodic storms carbonate sediment in gullies or outer fjord troughs consists of molluscs bryozoans benthic foraminifers and verrucid barnacles terrigenous sediment loads delivered as spring meltwater discharge is trapped in the inner fjord troughs hydrodynamic concentration of calcareous skeletons is fostered by a complex topography that offers numerous sediment trapping areas along the rocky coastline and outer fjord troughs physiological adaptation of coralline algae to cope with extreme seasonality in solar radiation is a prerequisite for the formation of coralline algal reefs beyond the arctic circle which have carbonate production rates near those of subtropical coralline algal grounds

differential structural and geomorphic mountain front evolution in an active continental collision zone the northwest pamir southern kyrgyzstan western central and eastern segments of the trans alai mountain front in the northern pamir of kyrgyzstan have accommodated varying degrees of approachment of the pamir orogen with respect to the tien shan shan mountains to the north ongoing collision between the north western corner of the indian indenter and eurasia has resulted in closure of the intramontane alai valley which separates the tien shan and trans alai pamir ranges the different segments highlight the processes of shaping tectonically active mountain fronts in a semiarid environment in this study we have characterized this variation in processes with compilations of regional tectonic information detailed geologic and geomorphic maps topographic analyses and interpretation of seismic reflection data along the sinuous western segment of the mountain front dextrally oblique thrusting has created a wide 500 m zone of highly erodible fault gouge this fault zone impinges on the southern tien shan but complete basin closure is prevented by erosion due to the westward flowing kyzilsu river the kyzilsu valley forms the only outlet and is the vestige of a formerly contiguous sedimentary basin linking the tarim basin of china with the tadjik depression in the west numerous large landslides rooted in the fault zone have covered the active fault which is partially undercut by the kyzilsu river older large landslides in this setting are associated with different levels of fluvial terraces of the former or present course of the kyzilsu river suggesting a causative relationship between lateral fluvial scouring failure of mechanically weak mountain fronts ongoing faulting and mass transfer along the linear central segment deformation is confined to a narrow single south dipping thrust fault that juxtaposes pliocene pleistocene and holocene conglomerates in this sector the mountain front has numerous holocene offsets this prevailing structural style and the long term deformation are underscored by multiple flights of gently sloping pediments and glaciogenic terrace surfaces that abruptly terminate at the steep mountain front which also forms the boundary with the wide regraded piedmont in contrast closure between the pamir and tien shan is complete along the eastern segment the eroded and sinuous mountain front has been tectonically inactive during late quaternary time small drainage basin areas and low stream power apparently were not conducive to maintaining an eastern outlet to the tarim basin active deformation has stepped back into the orogen and now is concentrated along the markansu fault and within the tien shan to the north the large drainage basin area of the kyzilsu river and the constant glacially fed runoff guarantee that an effective interplay between tectonic uplift and erosion is maintained therefore the geomorphically different mountain front segments highlight the relationships between tectonic uplift and geomorphic processes which in turn are controlled by lithology topography and the history of sediment routing throughout the landscape

timing of fluvial terrace formation and concomitant travertine deposition in the upper sutlej river tirthapuri southwestern tibet and paleoclimatic implications abstract travertines are carbonates precipitated from hydrothermal springs and are relatively common on the tibetan plateau and occur along tectonically active faults the karakoram fault system is an active strike slip fault that extends from the pamir into southwestern tibet where it controls the course of the upper sutlej river and the occurrence of several hydrothermal springs including the tirthapuri hot springs multiple fluvial terraces that are partly capped by travertine are preserved in the tirthapuri area four main fluvial terrace levels labelled as t1 to t4 with increasing height above river were identified and several meter thick travertine platforms occur on the current river level as well as the t2 and t3 terraces sedimentological and petrographic observations suggest that the travertine platforms were deposited on active floodplains of the paleo and modern sutlej river and preserved from fluvial erosion because travertine precipitation was immediately followed by vertical river bed incision and thus terrace abandonment results of 230th u in combination with luminescence dating show that the deposition of travertine platform and river incision that led to the formation of t3 terrace 93 m above the sutlej took place at ca 127 5 ka the development of terrace t2 and overlying travertine platform 28 m above the sutlej occurred between ca 10 0 and 8 8 ka fluvial incision has arrived at the modern level at least ca 0 2 ka ago both the travertine deposition and major river incision are likely triggered by the intensified indian summer monsoon and are linked to phases of maximum monsoon strength during strong monsoon phases a large quantity of moisture is transported into southwestern tibet activating hot springs and thus travertine precipitation facilitating fluvial incision and stripping off sediments from the regional hill slopes at least over the last glacial cycle we suggest that the tirthapuri travertine and associated fluvial incision are sensitive indicators of peak monsoonal activity and can thus provide valuable insights into past climate change and climate driven landscape evolution on the southwestern tibetan plateau comparison of our findings with published data further suggests that monsoon controlled fluvial aggradation and incision during the early holocene is synchronous in southwestern tibet and the adjacent sector of the himalayan orogen north western sub to high himalaya

quaternary deformation in the eastern pamirs tadzhikistan and kyrgyzstan active deformation in the eastern pamir of central asia is concentrated on the margins of the orogen with minor deformation within the high terrain along the trans alai mountain front at the northern perimeter of the orogen quaternary thrusting is documented by uplifted pediments now at 500 m above the piedmont holocene fault scarps and large earthquakes with n to nw oriented p axes seismicity in the interior of the orogen outlines a n s belt that includes normal faulting events with e w oriented t axes n s striking active normal faults in the interior lake karakul region are compatible with these earthquakes they define an asymmetric graben with a master fault at the western basin margin in the southern pamirs dextral strike slip faults root in the dextral karakorum fault which bounds the pamirs to the east a mixture of dextral and reverse offsets totalling 135 m in pleistocene terraces and 8 m in late pleistocene holocene deposits demonstrates contemporary transpression indicating average displacement rates of 1 mm yr the concentration of young thrusts along the trans alai the northward migration of thrusting and the scarcity of other large scale shortening features within the eastern pamirs suggest that this part of the orogen moves northward en bloc and causes the progressive annihilation of the intermontane alai valley widespread dextral shear in the eastern pamirs both to the south and north of the extensional karakul depression and combined dextral strike slip and normal faulting in the muji tashgorgan graben of the chinese pamirs are interpreted as localized space accommodation phenomena formed during progressive transfer of compressional deformation along a dextral strike slip deformation zone with extensional stepovers

late cenozoic tectonic development of the intramontane alai valley pamir tien shan region central asia an example of intracontinental deformation due to the indo eurasia collision 1 the pamir indentor of the northwestern himalayan syntaxis is a first order feature demonstrating partly the northward extent of deformation due to the cenozoic indo eurasia collision the alai valley of kyrgyzstan at the northern end of the indentor is a strategically positioned e w trending intramontane basin that constrains the timing and extent of crustal deformation in this area of the collision zone to quantify the convergence accommodated across the alai valley during the late cenozoic we collected structural and stratigraphic field data reviewed existing soviet literature and analyzed migrated seismic reflection profiles to construct and restore two regional sections crosscutting the basin our study suggests that the development progressive closure and conversion of this formerly marine basin into a terrestrial intramontane basin result from two main deformation events 1 distributed north south contraction took place during the late oligocene early miocene accommodated one third to half of the total shortening and was followed by the formation of a regional erosion surface and 2 n s shortening resumed in the mid miocene and continues today during this second episode the thrust front migrated southward localized along the trans alai ranges and failed to reactivate earlier neogene structures horizontal shortening of about 35 across the alai valley implies relatively low strain rates and displacement rates of about 4 18 4 69 10 16 s 1 and 0 66 0 78 mm yr 1 respectively for the last 25 myr our study confirms other regional observations indicating that contractional deformation occurred far in the interior of the asian continent as early as the late oligocene

paleozoic accretion and cenozoic redeformation of the chinese tien shan range central asia the tien shan range in central asia contains two late paleozoic sutures the older southern suture marks the collision of a passive margin at the north of the tarim block and an active continental margin subduction under the latter was to the north the younger northern suture separates a northern carboniferous island arc from an active continental margin developed over a south dipping subduction zone the subduction direction under the island arc is unknown mesozoic elastics were deposited over the doubly sutured orogen rate and energy of sedimentation waned until deposition of oligocene conglomerates above a regional unconformity interpreted as marking the onset of deformation induced by the india asia collision molasse deposition accelerated in pliocene and quaternary time and deposition continues today as active thrusts generate relief paleozoic structures control the gross divergence of cenozoic thrusts across the orogen

late paleozoic tectonic amalgamation of northwestern china sedimentary record of the northern tarim northwestern turpan and southern junggar basins sedimentary rocks contained in basins adjacent to the tian shan provide a long and complex record of the late paleozoic continental amalgamation of northwestern china complementing that provided by rocks preserved within the range this record which comprises dramatic changes in sedimentary facies sediment dispersal patterns sandstone provenance and basin subsidence rates broadly supports previous interpretations of a two part evolution of the tian shan late devonian to early carboniferous collision of the tarim continental block with the central tian shan followed by collision of this combined block with island arcs in the north tian shan and bogda shan in late carboniferous early permian times the first collision resulted in widespread angular unconformities within the tarim basin continued convergence following the collision created a long lived flexural foredeep along the northern margin of the tarim block which received at least 2000 m of lower carboniferous through lower permian fluvial and marine sediment derived from the interior of tarim subsequent early permian continental extension of the northern tarim basin resulted in the deposition of interbedded nonmarine siliciclastic sedimentary rocks and mafic to felsicvolcanic rocks sandstone within this interval was derived from the paleo tian shan and is composed predominantly of lithic volcanic grains similar to the rhyolite in contrast to the tarim basin calc alkaline volcanic rocks and volcanogenic sedimentary rocks dominated carboniferous and permian sedimentation in the northern turpan and northwestern junggar basins volcanic arcs remained active in the north tian shan and bogda shan through the early late carboniferous depositing a kilometers thick interval of deep marine sediment gravity flows in the northwestern junggar basin major arc magmatism ceased in the late carboniferous in response to closure of the oceanic basin between the combined tarim central tian shan block and the north tian shan bogda shan arcs upper carboniferous through lower permian rocks in the northwestern junggar basin compose the sedimentary fill of a bathymetric basin of oceanic depth on the northern side of the volcanic arcs culminating in a 1000 m thick marine regressive sequence middle to upper permian sandstones were derived from the uplifted paleo tian shan and bear the distinctive provenance imprint of granitic rocks presently exposed within the range late permian subsidence of the junggar basin accommodated 5 km of nonmarine sediments however the cause of this subsidence and its relationship to regional tectonic events remain controversial

deep structure of the baikal rift zone revealed by joint inversion of gravity and seismology 1 the question of plate boundary forces and deep versus shallow asthenospheric uplift has long been debated in intracontinental rift areas particularly in the baikal rift zone asia which is colder than other continental rifts as previous gravity and teleseismic studies support the dominance of opposing mechanisms in the baikal rift we reconsidered both data sets and jointly inverted them this more effective approach brings insight into location of the perturbing bodies related to the extension in this region our new joint inversion method allows for inverting the velocity density relationship with independent model parametrization we obtain velocity and density models that consistently show 1 crustal heterogeneities that coincide with the main tectonic features at the surface 2 a faster and denser cratonic mantle nw of lake baikal that we relate to the thermal contrast between old and depleted archean siberian platform and paleozoic orogenic belt sayan baikal belt 3 three dimensional topographic variations of the crust mantle boundary with well located upwarpings and 4 the lithosphere asthenosphere boundary uplift up to 70 km depth with a nw dip our resulting velocity and density models support the idea of a combined influence of lithospheric extension and inherited lithospheric heterogeneities for the origin of the baikal rift zone index terms 1234 geodesy and gravity regional and global gravity anomalies and earth structure 7218 seismology lithosphere and upper mantle 8122 citation tiberi c m diament j deverchere c petit mariani v mikhailov s tikhotsky and u achauer deep structure of the baikal rift zone revealed by joint inversion of gravity and seismology