constant elevation of southern tibet over the past 15 million years the uplift of the tibetan plateau an area that is 2 000 km wide to an altitude of about 5 000 m has been shown to modify global climate and to influence monsoon intensity mechanical and thermal models for homogeneous thickening of the lithosphere make specific predictions about uplift rates of the tibetan plateau but the precise history of the uplift of the plateau has yet to be confirmed by observations here we present well preserved fossil leaf assemblages from the namling basin southern tibet dated to approximately 15 myr ago which allow us to reconstruct the temperatures within the basin at that time using a numerical general circulation model to estimate moist static energy at the location of the fossil leaves we reconstruct the elevation of the namling basin 15 myr ago to be 4 689 895 m or 4 638 847 m depending on the reference data used this is comparable to the present day altitude of 4 600 m we conclude that the elevation of the southern tibetan plateau probably has remained unchanged for the past 15 myr

on the hellenic subduction zone and the geodynamic evolution of crete since the late middle miocene abstract in recent syntheses of the geodynamic evolution of the aegean area the hellenic subduction zone and in particular its initiation plays a central role two basic aspects of the recent comprehensive model put forward by le pichon angelier and co workers are a initiation of subduction along the hellenic arc is inferred to have taken place approximately 13 ma ago whereas several others have suggested approximately 5 ma and b migration of the trench system to the south southwest giving rise to an extensional regime in the back arc region which led to general subsidence and formation of the present day aegean sea new data on the structure of the upper mantle underneath the aegean area indicate that the former aspect requires modification the seismic velocity structure indicating a northward dipping slab down to a depth of at least 600 km and the depth distribution of earthquake hypocenters can not be reconciled with straightforward initiation of subduction approximately 13 ma ago estimates of about 5 ma for the time of initiation of the present subduction zone are even more difficult to reconcile assuming 400 km as an upper bound for the effect of stretching of the aegean sea and of other processes contributing to the separation of crete from the eurasian mainland we arrive at an age for the hellenic subduction zone of at least 26 ma as to aspect b geological data of crete lend strong support to the idea that on crete compressional tectonics is of much greater importance than current models imply combining geophysical and geological data we propose a modification of the tectonic evolution for the cretan segment of the hellenic arc whereas the basic process of extension caused by a migrating trench system roll back in a land locked basin remains a very useful and sound concept the tectonics of the margins of a region subject to stretching in this case crete may be more complicated than hitherto thought in our model the documented fragmentation of crete into several basins which started about 12 ma ago is not attributed to initiation of subduction but to inception of the roll back process compressional tectonics on crete is taken to be associated with deformation of the crust resulting from the overall tensional stress regime

global positioning system measurements of present day crustal movements in the arabia africa eurasia plate collision zone we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1994 at 54 sites extending east west from the caucasus mountains of southern russia georgia and armenia to the aegean coast of turkey and north south from the southern edge of the eurasian plate pontus block to the northern edge of the arabian platform viewed from a eurasia fixed reference frame sites on the northern arabian platform move n38 13 w at 20 3 mm yr roughly consistent with the velocity implied by nuvel 1a circuit closure n23 7 w at 24 2 mm yr the motion of arabia appears to be transferred directly to the region of turkey north of the suture however eastern turkey is characterized by distributed deformation while central western turkey is characterized by coherent plate motion involving westward displacement and counterclockwise rotation of the anatolian plate internal deformation within the central part of the anatolian plate is less than 2 mm yr the anatolian plate is decoupled from eurasia along the right lateral strike slip north anatolian fault naf this different response in eastern and western turkey to the collision of arabia may result from the different boundary conditions the hellenic arc forming a free boundary to the west and the asian continent and oceanic lithosphere of the black and caspian seas forming a resistant boundary to the north and east we derive a best fitting euler vector for anatolia eurasia motion of 29 2 0 8 n 32 9 0 4 1 3 0 1 m y the mapped surface trace of the naf corresponds well to a small circle about this pole the new euler vector implies an upper bound for naf slip rate of 30 2 mm yr i e assuming all relative motion is accommodated along the naf using the nuvel 1a euler vector for arabia eurasia and the gps euler vector for anatolia eurasia we determine an arabia anatolia euler vector of 31 2 n 45 2 e 0 9 0 1 m y and an upper bound on the east anatolian fault slip rate of 15 3 mm yr the aegean trough region of western turkey deviates significantly from coherent plate rotation in addition to rotating with anatolia this region shows roughly n s extension at a rate of 14 5 mm yr taken together with satellite laser ranging results along the hellenic arc the contemporary pattern of deformation indicates increasing motions toward the arc suggesting that the westward displacement and counterclockwise rotation of anatolia is driven both by pushing from the arabian plate and by pulling or basal drag associated with the foundering african plate along the hellenic subduction zone

palynological evidence for the latest oligocene early miocene paleoelevation estimate in the lunpola basin central tibet uplift of the tibetan plateau is ultimately driven by the cenozoic collision between the indian and eurasian plates and their continued convergence one approach for studying the tibetan plateau uplift is to verify the paleoelevation changes from collision to present day this is important for understanding both the tectonics and the climatic effects the new high resolution palynological record of the uppermost oligocene to the lowest miocene strata from the lunpola basin indicates that the vegetation types during the latest oligocene earliest miocene were dominated by mixed coniferous broadleaved forests being different from the modern steppe vegetation by using the coexistence approach to the fossil pollen records after calibration the effects of temperature difference and the lapse rate a maximum paleoelevation of 3190 100 m asl was estimated in the lunpola basin in the latest oligocene earliest miocene being 1500 to 2000 m lower compared with the previous oxygen isotope paleoelevation in the same region

long term seismicity of istanbul and of the marmara sea region we examine the long term seismicity of the marmara sea region in turkey over a period of twenty centuries to attempt to answer two questions 1 how well recorded in history is the earthquake activity of this region and 2 does seismicity over this long period of time differ from that over the present century we study this densely populated and fast developing region because it is one of the most tectonically active regions on the continents that appears today to be relatively quiescent

tectonics and magmatism in turkey and the surrounding area this volume contains 23 papers from a range of international contributors describing recent research into the tectonics and magmatism of turkey and its surroundings this region is sited at the collision zone between eurasia and afro arabia and as such provides an extraordinarily complete and well exposed record of the staged tectonic evolution of this sector of the alpine himalayan orogen the geological history of this area involves separation of continental fragments from the margin of gondwana their migration across the tethyan oceans the subsequent closure of these oceans and finally the development of the neotectonic regime which continues to evolve to the present day such a comprehensive record is relevant to the understanding of collisional zones worldwide the volume is divided into five sections tethyan evolution neotethyan ophiolites post tethyan basin evolution neotectonics and igneous activity the first two sections deal with tethyan oceans whose growth and subsequent closure dominated the geodynamic framework in the mesozoic and cenozoic the subsequent sections deal with more recent geological developments from the balkan peninsula in the west to the transcaucasus in the east that followed consumption of the tethyan oceans there is a broad mix of papers throughout the volume wide ranging review papers on ocean development and extensional tectonics are followed by detailed descriptions of petrology and geochemistry and geographically focused studies on basin evolution specific aspects of extensional and strike slip tectonics and discussions of the relationship of magmatic activity to the tectonic development of the area tectonics and magmatism in turkey and the surrounding area presents up to date results and ideas from a large number of international contributors on a wide range of current research activity in this region it is essential reading for all geoscientists with an interest in both academic and applied aspects of eastern mediterranean geology

paratethyan mediterranean connectivity in the sea of marmara region nw turkey during the messinian the sea of marmara region is thought to have been a gateway between paratethys and the mediterranean since the middle miocene and is therefore an important control on water mass exchange between the two realms the miocene successions in the northeastern aegean and northwestern marmara regions indicate that the first mediterranean marine transgression to affect these areas occurred during the late serravallian in the northeastern aegean region frequent marine incursions occurred during the tortonian and messinian stages the messinian stage in this area is represented by a package of brackish to fresh water carbonates with some marine sandstone siltstone interbeds alcitepe formation which conformably overlies the tortonian kirazli formation the messinian sequence is overlain with an erosional contact by a shallow marine siliciclastic sequence goztepe formation of zanclean age with its brackish to fresh water carbonates and broadly constrained age the messinian sequence is interpreted as being coeval with the upper evaporite lago mare sequence observed in western mediterranean basins in the western marmara region the pontian messinian alcitepe formation consists of bioclastic and oolitic limestones with basal clastic rocks it conformably overlies the fluvio lacustrine siliciclastic sediments of the middle to upper miocene kirazli formation and is overlain by fluvio lacustrine sediments of the kimmerian 5 5 3 2 ma truva and tevfikiye formations with an erosional contact the bioclastic limestones of the alcitepe formation in the western marmara region contain a molluscan and ostracod fauna that are endemic to paratethys these fauna indicate deposition in a shallow brackish to fresh water environment faunal and paleomagnetic analyses of a section of the alcitepe formation at yenimahalle canakkale confirm that the formation is of pontian age and represents chron c3r 6 04 5 24 ma the ostracod analysis indicates that during deposition of the alcitepe formation salinity increased from brackish in the lower part to more saline conditions in the upper part ostracod valves have low 87sr 86sr values relative to coeval late miocene ocean water this indicates that exchange between the sea of marmara region and the global ocean was restricted throughout this period fossil and sr isotope evidence suggests however that there was a paratethyan marmara connection during the deposition of the lower part of the alcitepe formation with paratethyan influence reaching the north aegean connection via marmara between paratethys and the mediterranean was not re established until the late aktchagylian late pliocene the re connection was caused by both increased activity on the north anatolian fault and global sea level rise

morphotectonic evidence from the southern branch of the north anatolian fault naf and basins of the south marmara sub region nw turkey this study investigated the morphotectonic evidence from the southern branch of the north anatolian fault naf and the south marmara sub region nw turkey the south marmara sub region has two uplifts located in the south and north and a depression between these uplifts the uplifts are bounded by the southern branch of the naf the southern branch is divided into the yenice gonen ygfz manyas mustafakemalpasa mmf uluabat ufz and bursa bfz faults the relation between the active tectonics and recent morphology were evaluated by using the geomorphic indices gis af asymmetry factor t topographic symmetry factor sl river length gradient index smf mountain front sinuosity gis were used to define the effects of tectonism on morphology and were used to calculate the relative tectonic activity index iat the values obtained through the gis indicate a young tectonism in the study area the study area morphometrically presented two iat classes class 1 high relative tectonic activity and class 2 moderate relative tectonic activity the present gps data and iat classes of the southern branch faults of the nafz were correlated all of the calculations and field data reveal that the southern branch of the naf is the main tectonic element forming the geomorphology of the south marmara sub region

tectonic evolution of the gediz graben field evidence for an episodic two stage extension in western turkey western turkey is one of the most spectacular regions of widespread active continental extension in the world the most prominent structures of this region are e w trending grabens e g gediz and buyuk menderes grabens and intervening horsts exposing the menderes massif this paper documents the result of a recent field campaign field geological mapping and structural analysis along the southern margin of the modern gediz graben of pliocene 5 ma age this work provides field evidence that the presently low angle ductile brittle detachment fault is cut and displaced by the high angle graben bounding normal faults with total displacement exceeding 2 0 km the evolution of the n s extension along the gediz graben occurred during two episodes each characterized by a distinct structural styles 1 rapid exhumation of menderes massif in the footwall of low angle normal fault core complex mode during the miocene 2 late stretching of crust producing e w grabens along high angle normal faults rift mode during pliocene quaternary times separated by a short time gap the later phase is characterized by the deposition of now nearly horizontal sediments of pliocene age in the hanging walls of the high angle normal faults and present day graben floor sediments the evolution of extension is at variance with orogenic collapse and or back arc extension followed by the combined effect of tectonic escape and subduction rollback processes along the aegean cyprean subduction zone consequently it is misleading to describe the miocene sediments exhumed on shoulders of the gediz graben as simple graben fill

geology of the saros graben and its implications for the evolution of the north anatolian fault in the ganos saros region northwestern turkey abstract palaeo and neo tectonic evolutions of the gulf of saros northwestern turkey were investigated based on geological mapping geomorphology seismicity and gps measurements in this area three overlapping basins were differentiated the thrace enez and saros basins the thrace basin opened during the middle eocene on the continental strandja massif as a post collisional fault controlled extensional basin after the closing of the intra pontide ocean to the south this basin reached its greatest extent during the late eocene early oligocene and then turned into an intramontane terrestrial basin from the middle miocene onwards the enez basin opened along the southern margin of the former thrace basin as an e w trending half graben during the middle miocene the age and geometry of this basin corresponds to the extensional basins of the aegean graben system to the south stratigraphy and structures related to the north anatolian fault indicate that the fault started to be active since pliocene and modified older structures the fault zone evolved in two stages in and around the gulf of saros during the initial stage the fault was trending as a single segment with a transpressional nature and without any stepping and caused thrusting and folding subparallel to the main trace of the fault since the late pliocene the fault was left stepping in the saros area giving rise to the saros pull apart basin we modelled these two stages by using boundary element method and found that there is a good correlation between the modelling results and geology and geomorphology

supradetachment basin evolution during continental extension the aegean province of western anatolia turkey we present a detailed structural and stratigraphic record of a neogene quaternary supradetachment sedimentary succession in the aegean extensional province of western anatolia and we compare its tectonic features and evolution to those of other well documented supradetachment basins around the world the sedimentary fill of the alasehir basin records the uplift and exhumation of a core complex in the footwall of a detachment fault within the central menderes massif accumulation of footwall derived clastic sediments in this basin started ca 20 ma shortly after the initiation of the approximately e w trending alasehir detachment and its shear zone and continued until ca 2 ma major sedimentary facies types include fluvial and alluvial fan deposits debris flow and mass flow deposits and locally developed lacustrine rocks these sedimentary units were accumulated largely in distal depocenters within the extending basin as the low angle 15 28 detachment faulting created little accommodation space near the basin margins while producing high back shed topography in the uplifted menderes core complex the drainage system was dominated mainly by extension parallel transverse streams during the main phases of basin evolution extension parallel scissor hinge faulting produced differential uplift and subsidence in the adjacent fault blocks changed the direction of sediment transport and drainage patterns over short distances and resulted in the local uplift of the older basin strata these processes led to the development of subbasins with lateral variations in basement topography strata thickness and sedimentary facies distribution and generated a segmented basin architecture high angle synthetic and antithetic faults that formed extensively after 3 ma caused back tilting of the sedimentary strata formation of half grabens with their own axial drainage systems and development of angular unconformities with the onset of this crustal scale block faulting the detachment fault ceased to operate and the quaternary gediz graben started to develop at the northern end of the alasehir supradetachment basin our comparative evaluation of select basins shows a maximum sediment thickness of 3 km average extension rates of 6 to 8 9 mm yr 1 and accumulation rates of 0 1 0 2 mm yr 1 uncorrected for compaction in supradetachment basins in general the rates and amounts of extension the geometry of detachment faulting the rates of footwall uplift and the kinematics and interplay of different fault systems are the most important factors controlling three dimensional structural architecture and evolution of supradetachment basins

formation of internally drained contractional basins by aridity limited bedrock incision 1 low internal relief aridity and internal drainage characterize the puna altiplano plateau and the tibetan plateau and the tarim basin structurally these areas are reverse fault bounded terrains with intervening wedge top basins that store thick accumulations of sediment for millions of years orographic barriers along the margins of these basins are oriented normal to moisture bearing winds resulting in regional aridity the combination of this aridity rapid shortening and uplift rates and resistant exposed lithologies coincides with the location of these internally drained basins we hypothesize that these large internally drained areas persist indefinitely when uplift overwhelms the fluvial systems and defeats the channel network to test this hypothesis we developed models of channel defeat to examine the threshold conditions required to fragment the channel network the results of these models suggest that low erodibility rocks moderate to high uplift rates and low precipitation favor defeat of orogen traversing channels most coupled tectonic landscape development models prevent the development of internal drainage and so may overestimate the voracity of erosion in regimes that favor internal drainage profoundly influencing predicted orogenic growth patterns

age determination for segments of the north anatolian fault naf northern branch by 234u 230th dating of sogucak yalova range front travertines south marmara turkey abstract the sogucak travertine occurrences developed along north segment of the north anatolian fault naf in yalova province marmara region turkey the range front type travertines outcropping over an approximately 1 km2 area with 20 40 m thickness are middle thick bedded and back tilted southward or horizontally lithology of the travertines includes physolite stalactites stalagmites cave pearls sharp pebble carbonate nodules spherical roller intricate shapes and laminated banded travertines geochemical analysis was performed on six samples of the travertines the samples showed high calcite composition averagely 98 and mg carbonite content varying from 0 87 to 1 33 the travertines were deposited by means of normal faults as indicated by structural and morphological relationship with active tectonics 234u 230th dating of the travertines provided an age range from 61 318 3 091 to 231 944 141 902 ka findings show that the travertine deposition and deployment of faults in the region occurred approximately at 231 ka corresponding to middle pleistocene therefore the age of both travertines and naf was determined as middle pleistocene

discovery of the oldest european ruminant in the late eocene of bulgaria did tectonics influence the diachronic development of the grande coupure abstract we describe the oldest known european ruminant bachitherium thraciensis sp nov from late eocene latest bartonian or early priabonian strata in bulgaria the new specimen which possesses the most primitive dental morphology known in the bachitheriidae family predates its western european relatives by at least 4 5 myr the discovery suggests that ruminants dispersed into europe in a series of east to west waves preceding and following the eocene oligocene boundary probably originating from asia the oldest ruminant reported here migrated into southeastern europe during a second wave comprising the grand coupure dispersal event ruminants moved into western europe at the eocene oligocene boundary a third wave composed by bachitheriidae and tragulidae arrived in western europe 2 myr later in the earliest oligocene the origin of this east to west diachronism was probably facilitated by orogenesis that episodically allowed dispersal of ruminants from asia through southeastern europe and into western europe in what we herein term the bachitherium dispersal event however none of the abundant perissodactyl fauna from southeastern europe migrated to western europe during this time because like their relatives in central asia they may not survive to terminal eocene cooling and aridity

paleocene to pliocene low latitude high elevation basins of southern tibet implications for tectonic models of india asia collision cenozoic climate and geochemical weathering the elevation history of the tibetan plateau promises insight into the mechanisms and dynamics that develop and sustain high topography over tens of millions of years we present the first nearly continuous cenozoic elevation history from two sedimentary basins on the southern tibetan plateau within the latest cretaceous to eocene gangdese arc oxygen isotope and 47 clumped isotope compositions of nonmarine carbonates allow us to constrain carbonate formation temperature and reconstruct the paleoprecipitation record of the eocene to pliocene oiyug basin and paleocene to eocene penbo basin we exploit the systematic decrease of surface temperature and meteoric water 18o values with elevation to derive paleoelevation estimates for these basins minimally altered and unaltered pedogenic and lacustrine carbonates from the oiyug basin yield 47 cdes relative to the carbon dioxide equilibrium scale cdes values of 0 625 to 0 755 which correspond to temperatures of 1 30 c using a 47 thermometer for low temperature carbonates similarly the penbo basin yielded 47 cdes values of 0 701 to 0 726 corresponding to temperatures of 6 12 c the apparent evidence for survival of primary clumped isotope values in the face of substantial burial and heating is an important result for the field of carbonate clumped isotope thermometry our paleoelevation estimates for the eocene to pliocene oiyug basin 6 5 4 1 km support previous evidence that high elevations were attained in southern tibet by at least ca 30 ma stable isotope results allow for the possibility of significant topographic subsidence during the miocene as a result of regional extension in the penbo basin our paleoelevation estimates for the paleocene to eocene nianbo formation 4 4 1 3 1 7 km and eocene pana formation 4 1 1 2 1 6 km extend the altitude record of the southern tibetan plateau to pre india asia collision these results support the lhasaplano model of an andean type continental margin tectonic system the rise of the himalayas and tibet is often invoked to understand isotopic proxies for global chemical weathering in the cenozoic and has constrained the debate on the nature of co2 climate weathering feedbacks the nature of the tibetan paleoelevations from pre to postcollision as presented here indicates that high relief at low latitude prevailed on the asian margin much earlier than previously thought thus high topography alone at low latitude is not sufficient to account for the cenozoic weathering proxy record

quantifying the rise of the himalaya orogen and implications for the south asian monsoon we reconstruct the rise of a segment of the southern flank of the himalaya tibet orogen to the south of the lhasa terrane using a paleoaltimeter based on paleoenthalpy encoded in fossil leaves from two new assemblages in southern tibet liuqu and qiabulin and four previously known floras from the himalaya foreland basin u pb dating of zircons constrains the liuqu flora to the latest paleocene ca 56 ma and the qiabulin flora to the earliest miocene 21 19 ma the proto himalaya grew slowly against a high similar to 4 km proto tibetan plateau from similar to 1 km in the late paleocene to similar to 2 3 km at the beginning of the miocene and achieved at least similar to 5 5 km by ca 15 ma contrasting precipitation patterns between the himalaya tibet edifice and the himalaya foreland basin for the past similar to 56 m y show progressive drying across southern tibet seemingly linked to the uplift of the himalaya orogen

active tectonics of the north and central aegean sea summary in this paper we examine the connection between the westward motion of turkey relative to europe and the extension in and around the aegean sea the principal new data available since the last attempt to synthesize the tectonics of this region by mckenzie 1978 are much improved focal mechanisms of earthquakes constrained by p and sh body wave modelling as well as by first motions these mechanisms show that the faulting in the western part of the aegean region is mostly extensional in nature on normal faults with a nw to wnw strike and with slip vectors directed nnw to nne there is evidence from palaeomagnetism that this western region rotates clockwise relative to stable europe in the central and eastern aegean and in nw turkey distributed right lateral strike slip is more prevalent on faults trending ne to ene and with slip vectors directed ne palaeomagnetic data in this eastern region is more ambiguous but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations relative to europe in the south the strike slip faulting that enters the central aegean from the east appears to end abruptly in the sw against the nw trending normal faults of greece the kinematics of the deformation is controlled by three factors the westward motion of turkey relative to europe the continental collision between nw greece albania and the apulia adriatic platform in the west and the presence of the hellenic subduction zone to the south as the right lateral slip on the north anatolian fault enters the aegean region it splays out becoming distributed on several parallel faults the continental shortening in nw greece and albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed e w right lateral shear and thus leads to e w shortening in the northern aegean which is compensated by n s extension as the southern aegean margin can move easily over the hellenic subduction zone the dynamics of the system once initiated is self sustaining being driven by the high topography in eastern turkey and by the roll back of the subducted slab beneath the southern aegean the geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate in spite of its extreme simplicity a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the aegean region including the slip vectors and nature of the faulting in the eastern and western parts the senses and approximate rates of rotation the overall extensional velocity across the aegean and the distribution of strain rates as seen in the seismicity and topography or bathymetry and using geodetic measurements as part of this study we re examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 gulf of corinth earthquakes and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting an important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves

the active main marmara fault abstract this paper presents selections from and a synthesis of a high resolution bathymetric sparker and deep towed seismic reflection data set recently acquired by the french ifremer r v le suroit in an e w deep trough that forms the northern half of the sea of marmara in nw turkey it includes the first high resolution complete bathymetric map of this area a single throughgoing dextral strike slip fault system which is the western continuation of the northern branch of the north anatolian fault cuts this trough lengthwise and joins the 1999 8 17 kocaeli earthquake fault with the 1912 8 09 arkoy murefte earthquake fault both of which display strike slip offset in its eastern one fourth the structure follows closely the northern margin of the deep trough whereas in the west it hugs its southern margin the eastern one fourth of the structure has a minor component of its displacement distributed across the deep trough owing to a possible original bend in the course of the dextral structure the present course of the north anatolian fault in the sea of marmara originated some 2 105 a ago by cutting across the older basin fabric generated by a dominant nne ssw extension before it began taking up major motion in the pliocene

the andean type gangdese mountains paleoelevation record from the paleocene eocene linzhou basin abstract paleoelevation reconstruction using oxygen isotopes is making a significant contribution to understanding the cenozoic uplift of the himalayas and the tibetan plateau this paper presents new oxygen and carbon isotopic compositions from well dated tertiary paleosols lacustrine calcareous carbonates and marls from the nianbo 60 54 ma and upper pana formations 51 48 ma of the linzizong group in the linzhou penbo basin the sediments of the nianbo formation which are 180 m thick were deposited in alluvial fans braided rivers fan deltas and on nearshore to offshore lacustrine settings whereas those of the upper pana formation are 100 m thick and are comprised predominantly of proximal alluvial fan and braided river deposits correlations between the lithofacies and stable isotopic compositions suggest that the basin was mainly a hydrologically open environment it is confirmed that the 18 o c and 13 c c values from nianbo and pana formations have not yet been reset by late stage diagenesis based on petrographic examination oxygen isotope of the fossil ostracodes and tectonic deformation of strata the paleoelevations are reconstructed using the corrected most negative paleosurface water 18 o psw values these imply that the linzhou area had attained an elevation of 4500 400 m during the period of the indo asian collision i e achieved a near present elevation and may form an andean type mountain range stretching the gangdese arc before collision the gangdese mountains probably maintained high elevations since at least the paleocene and could play a crucial role in the climate change in the interior of the tibetan plateau during the early cenozoic the paleogeomorphic scenario of the eocene tibet is proposed to exist at two high mountains in excess of 4500 m that sandwiched a low elevation basin

a record of uranium series transport at nopal i sierra pena blanca mexico implications for natural uranium deposits and radioactive waste repositories abstract studies of uranium series u series disequilibria within and around ore deposits provide valuable information on the extent and timing of actinide mobility via mineral fluid interaction over a range of spatial and temporal scales such information is useful in studies of analogs of high level nuclear waste repositories as well as for mining and mineral extraction sites locations of previous nuclear weapons testing and legacy nuclear waste contamination in this study we present isotope dilution mass spectrometry u series measurements for fracture fill materials hematite goethite kaolinite calcite dolomite and quartz from one such analog the nopal i uranium ore deposit situated at pena blanca in the chihuahua region of northern mexico the ore deposit is located in fractured unsaturated volcanic tuff and fracture fill materials from surface fractures as well as fractures in a vertical drill core have been analyzed high uranium concentrations in the fracture fill materials between 12 and 7700 ppm indicate uranium mobility and transport from the deposit uranium concentrations generally decrease with horizontal distance away from the deposit but in this deposit there is no trend with depth below the surface isotopic activity ratios 238u 234u 230th 232th linear age trends and u th pa model ages indicate an actinide mobility evolution that can be characterized as complex and varied there is evidence of both open and closed system behavior for uranium depending on both sample and time scale the 234u 238u activity ratios indicate u mobility from 1 2 0 2 ma in the last 0 2 ma there is isotopic evidence for some u mobility but mostly u immobility in almost all cases the th pa radionuclides studied here have been immobile for the past 200 ka radium appears to have been recently 0 1 8 ka mobile due to ongoing fluid flow in the fractures overall the mainly closed system behavior for u th pa over the past 200 ka provides an indicator of the geochemical immobility of these actinides over time scales relevant for potential nuclear waste repositories situated in fractured unsaturated tuff

how wet was the arctic eocene rain forest estimates of precipitation from paleogene arctic macrofloras the eocene was the warmest part of the cenozoic when warm climates extended into the arctic and substantive paleobotanical evidence indicates broadleaf and coniferous polar forests paleontological temperature proxies provide a basis for understanding arctic early paleogene climates however there is a lack of corresponding proxy data on precipitation both leaf physiognomic analysis and quantitative analysis of nearest living relatives of an arctic macroflora indicate upper microthermal to lower mesothermal moist climates mean annual temperature 13 15 c cold month mean temperature 4 c mean annual precipitation 120 cm yr for axel heiberg island in the middle eocene leaf size analysis of paleocene and eocene arctic floras demonstrates high precipitation for the paleogene western and eastern arctic the predicted enormous volume of freshwater entering the arctic ocean as a result of northward drainage of a significant region of the northern hemisphere under a high precipitation regime would have strongly affected arctic ocean salinity potentially supporting arctic ocean azolla blooms high paleogene precipitation around the arctic basin is consistent with high atmospheric humidity which would have contributed significantly to polar and global eocene warming

lignite and carbonate deposition in middle lignite succession of the soma formation soma coalfield western turkey the middle miocene carbonate dominated units that are called the middle lignite succession of the soma formation from the soma coalfield of western turkey were analyzed and two facies associations containing eight facies were determined from the detailed measured sections of the opencast lignite mines the sedimentological stratigraphical and palaeobotanical data and regional geology indicate alluvial and or floodplain shallow freshwater carbonate lakes and lake margin environments including forest mountain swamps in the intramontane basin which was developed on the collision related basement rocks the middle lignite succession displays cyclic depositional nature consisting of alternating fine grained siliciclastic rock lignite and freshwater carbonate rock some diagenetic features and algal laminations structures in carbonate rocks as well as paleosol relics and geological evidence of the lignite forming paludal swampy conditions suggest alternating wet and dry periods in depositional system the lignite deposition occurred in wetlands that formed during deposition of the middle lignite succession in alluvial plain and shallow carbonate lake margins the paleobotanical palynological considerations sedimentological features and depositional setting of the middle lignite succession indicate a seasonal warm and semi arid or dry climate for lignite deposition the subsidence sediment supply seasonal climate topography and pre miocene carbonate basement may suggest main factors for lignite formation and preservation

peneplain formation in southern tibet predates the india asia collision and plateau uplift the uplift history of tibet is crucial for understanding the geodynamic and paleoclimatologic evolution of asia however it remains controversial whether tibet attained its high elevation before or after india collided with asia 50 m y ago here we use thermochronologic and cosmogenic nuclide data from a large bedrock peneplain in southern tibet to shed light on the timing of the uplift the studied peneplain which was carved into cretaceous granitoids and jurassic metasediments is located in the northern lhasa block at an altitude of 5300 m thermal modeling based on u th he ages of apatite and zircon and apatite fission track data indicate cooling and exhumation of the granitoids between ca 70 and ca 55 ma followed by a rapid decline in exhumation rate from 300 m m y to 10 m m y between ca 55 and ca 48 ma since then the peneplain has been a rather stable geomorphic feature as indicated by low local and catchment wide erosion rates of 6 11 m m y and 11 16 m m y respectively which were derived from cosmogenic 10 be concentrations in bedrock grus and stream sediment the prolonged phase of erosion and planation that ended ca 50 ma removed 3 6 km of rock from the peneplain region likely accomplished by laterally migrating rivers the lack of equivalent sediments in the northern lhasa block and the presence of a regional unconformity in the southern lhasa block indicate that the rivers delivered this material to the ocean this implies that erosion and peneplanation proceeded at low elevation until india9s collision with asia induced crustal thickening surface uplift and long term preservation of the peneplain

structural relationship between the sea of marmara basin and the north anatolian fault zone the north anatolian fault naf zone is 1500 km long extending almost up to the greek mainland in the west it is a seismically active right lateral strike slip fault that accommodates the relative motion between the turkish block and black sea plate the sea of marmara lies along the western part of the naf and shows evidence of subsidence in this area pure strike slip motion of the fault zone changes into extensional strike slip movement that is responsible for the creation of the sea of marmara and the north aegean basins the northern half of the sea of marmara is interpreted as a large pull apart basin this basin is subdivided into three smaller basins separated by strike slip fault segments of uplifted blocks ne sw basinal areas are covered by horizontally layered sedimentary sequences uplifted blocks have undergone compressional stress all the blocks are subsiding and are undergoing vertical motions and rotations relative to one another the uplifted blocks exhibit positive bouguer gravity anomalies according to gravity interpretation there is relative crustal thinning under the sea of marmara the northern side of the sea of marmara is marked by a distinctive deep rooted magnetic anomaly which is dissected and shifted southward by strike slip faulting the southern shelf areas of the sea of marmara are dominated by short wavelength magnetic anomalies of shallow origin

seismotectonic investigation of biga peninsula in sw marmara region using steerable filter technique potential field data and recent seismicity we examine seismotectonic setting of biga peninsula in western anatolia canakkale region using the steerable filter technique and recent seismicity one of the most important issues in geophysics is to observe borders or margins of tectonic geologic discontinues for this purpose we apply this filter technique to gravity anomaly map of biga peninsula we observe undetected buried faults in biga peninsula using the steerable technique where they have never been seen in the geological maps before these buried faults comply with recent seismicity for this region focal mechanisms of past earthquakes m 3 5 are in good agreement with fault orientations this observation shows that we have to take into account these fault locations and consider for preparing future seismic hazard maps the geometry of fault segments reveals mostly strike slip faulting regime with ne sw trending direction of t axis in the entire study region according to high resolution hypocenter relocation of the biga earthquake sequences in the observation period between 5 january 2005 and 14 november 2015 extends from n to s direction the stress tensor inversion results indicate a predominant normal stress regime with a nw se oriented maximum horizontal compressive stress s h according to strong discrepancy of density in the biga peninsula is characterized by numerous small segmented secondary faults these buried or undetected fault locations indicate that these segments are large enough to increase earthquake stress failure towards nw se and n s directions respectively seismotectonic setting of biga peninsula is divided into sub regions by ne sw trending secondary faults with normal and major strike slip components this output is verified by steerable filter and local regional seismotectonic analysis we propose a new seismotectonic model for biga peninsula and update the orientation of active fault segments according to our model north anatolian fault zone cross cuts the southern marmara basins as a narrow fault segment and continues towards aegean sea

present day kinematics of the middle east and eastern mediterranean the middle east and eastern mediterranean regions contain three major strike slip fault zones the dead sea fault zone dsfz and the north and east anatolian fault zones nafz and eafz these accommodate northward motion of the african and arabian plates relative to eurasia and westward motion of the small turkish plate this study deduces an internally consistent solution for the present day kinematics of these plates which is accurate to better than 20 and applicable throughout time since 5 ma by constraining the slip senses and rates on these strike slip fault zones the 7 0 5 mm yr 1 left lateral slip rate on the dsfz is associated with counterclockwise rotation of arabia relative to africa at 0 33 m y 1 around an eulcr pole near 33 n 23 e the nafz takes up counterclockwise rotation of the turkish plate relative to eurasia at 0 83 m y 1 13 around a pole at 31 n 35 5 e with right lateral slip rate 15 mm yr 1 the resulting prediction for the eafz involves 14 mm yr 1 left lateral motion and 2 mm yr 1 of shortening between arabia and turkey the triple junction of africa arabia and turkey is near the city of kahramanmaras this locality contains a narrow promontory bounded by ssw trending left lateral faults at the edges of the arabian and turkish plates which is loosely attached to the african plate moving westward relative to its interior at 4 mm yr 1

rift formation in the gokova region southwest anatolia implications for the opening of the aegean sea the time of the onset and the nature of the extension in the aegean area have been problematic owing to the confusion of neotectonic replacement structures with neotectonic revolutionary structures this paper concerns two rift systems of different ages and orientations in the gokova region of southwestern anatolia the first system has a northwest southeast trend with a middle to upper miocene infill whereas the second system is orientated in an east west direction and filled with plio quaternary rocks structural and palaeomagnetic data indicate that the first system originally had a north south trend and then bodily rotated anticlockwise to its present orientation before the end of the miocene both the orientations and the structural patterns of these cross cutting rift systems suggest that they resulted from two different and successive tectonic regimes regional geology suggests that the generative regime of the older system was characterized by north south compression and related to the palaeotectonic evolution of southwestern anatolia whereas that of the younger system is characterized by north south extension and relates to the neotectonic evolution of this region this inference contradicts at least in southwestern anatolia some recent claims that the extensional tectonics and the related rift formation in the aegean region began in the early miocene with the alleged demise of the compressional palaeotectonics during the late oligocene but is consistent with older views that placed the onset of north south extension into the later middle miocene the formation of the aegean sea seems to be the result of these two complicated and contrasting succesive tectonic regimes that have affected this region since middle miocene times

stable isotopes reveal southward growth of the himalayan tibetan plateau since the paleocene abstract original stable isotope compositions of carbonates representing conditions in the latest oligocene early miocene kailas and qiabulin areas both in southern tibet record oligocene miocene paleoelevations of the gangdese arc and the himalayan orogen and provide constraints on the formation of the himalayan tibetan plateau oxygen isotope compositions of bivalve shell paleosol and lacustrine carbonates indicate the preservation of unaltered isotopic signals of paleometeoric waters in the kailas and qiabulin areas whereas the oxygen isotopic compositions of liuqu eocene paleosols were likely altered by paleometeoric waters paleoelevation estimates using oxygen isotopes indicate the kailas area was at 4 9 km during 20 19 ma and the qiabulin basin was at 2 0 km during 24 21 ma but rose rapidly to 4 1 km between 21 and 19 ma these results suggest a steep south facing flank on the proto tibetan highland prior to the onset of the india asia collision the himalayan orogen began to be built against the pre existed high 4 5 km gangdese mountains in the early eocene and obtained elevations close to those of the present by the early miocene we propose that the southernmost tibetan plateau and himalayan orogen are the expression of an early eocene to early miocene southward migration of the locus of deformation early stage uplift is linked to the crustal thickening in the early eocene but the dramatic elevation gain in the early miocene may have been caused by indian slab rollback break off and coeval renewed underthrusting behind which late miocene to present east west crustal extension took place

gps derived strain rate field within the boundary zones of the eurasian african and arabian plates we use the gps velocity field 1988 1998 for eastern mediterranean and asia minor to determine the crustal deformation strain rate field in an area bounded by 35 n and 43 n and 20 e and 48 e we calculate the normal and shear strain rate components associated with the major faults and compare these qualitatively with seismological data uncertainties in the calculation of the strain rates reach 50 nstrain yr 1 in sparsely observed parts of anatolia whereas we estimate errors 20 nstrain yr 1 in the aegean and marmara regions the largest compressional strain rate components in the eastern part of the study area occur along the greater caucasus mountain front reaching 70 nstrain yr 1 1 nstrain yr 1 0 0317 10 15 s 1 the north anatolian fault zone is the clearest feature in the shear strain rate field it is expressed as a pronounced dextral strike slip fault zone reaching rates of up to 170 nstrain yr 1 this holds true also for the izmit area where the august 17 1999 earthquake occurred central anatolia is almost strain free whereas extension prevails in western anatolia the principal axes of extension vary around the n s direction with strain rates of up to 85 nstrain yr 1 these extensional areas coincide with graben features and normal faulting earthquakes the central and southwestern aegean sea is strain free with values far below 40 nstrain yr 1 the seismic cluster around the dodekanissa islands southeastern aegean sea coincides with nw se oriented extension attaining strain rates of up to 90 nstrain yr 1 this area of extension also exhibits recent active volcanism the entire hellenic arc shows compressional strain rates perpendicular to the arc the pliny strabo troughs along the eastern segment of the arc show left lateral shear strain rates reaching 80 nstrain yr 1 significant extension is found in central greece with a nne ssw oriented maximum of 120 nstrain yr 1 centered around the gulf of corinthos the kephalonia fault zone in nw greece is a distinct dextral fault zone separating apulia from the rapidly moving aegean microplate right lateral shear strain rates reach 150 nstrain yr 1

palaeogeographical evolution of the thrace neogene basin and the tethys paratethys relations at northwestern turkey thrace abstract the thrace neogene basin situated in northwestern turkey was initiated by strike slip faulting that was active from the early miocene until the end of the pliocene during the early miocene it began to form under the control of the thrace eskisehir fault zone initiated by continental collision in northwestern anatolia late oligocene early miocene during the late early miocene the basin was a site of mainly fluviatile and limnic sedimentation to the west and marine sedimentation via the paratethyan transgression in the north with the onset of the middle miocene the thrace block started to rotate in a counterclockwise sense and escaped westward with respect to the strandja istanbul block owing to rejuvenation of fossil fault systems within it in this period warm marine conditions were also established around the gulf of saros through a mediterranean originated transgression during the middle late miocene fluviatile and limnic conditions were created over the western thrace by the westerly propagation of the thrace eskisehir fault zone one of the principal results of the early middle miocene tectonics is the tilting of the strandja istanbul block to the south severing the tethys and the paratethys during the latest miocene early pliocene period the thrace eskisehir fault zone was deactivated because of the evolution of the north anatolian fault zone to the south the resurrected ganos fault zone situated on the dissected fossil suture zone in the sea of marmara also joined the north anatolian fault zone uplifting the gelibolu peninsula and thus severing the connection that existed between the sea of marmara and the paratethys the sea of marmara eventually became an endemic basin by the activity of the north anatolian fault zone

extensional compressional tectonics associated with the aegean arc comparison with the andean cordillera of south peru north bolivia extensional compressional tectonics are analysed along the convergent boundaries of the aegean arc and of the andean cordillera of south peru and north bolivia this paper deals only with deformations of miocene pliocene and pleistocene ages the prevailing regime in the aegean basin is extensional yet two compressional tectonic phases of u miocene l pliocene and of l pleistocene age have been recorded they are also known in many places all around the mediterranean thus forces that induce compressional tectonics in the aegean seem to have their origin outside the region they seem to be linked with changes in the conditions of convergence change in rate between the arabo african and eurasian plates beneath the andean cordillera of south peru north bolivia the subduction zone plunges at an angle of 25 30 as it does under the aegean arc there as in the aegean sea tectonics are predominantly extensional and several short lived compressional phases break up this extensional regime the latter may also be induced by changes of the conditions of convergence here between the nazca and south american plates beneath central peru north of the nazca ridge the subduction zone plunges at a small angle about 10 there neotectonic deformations are different in the recent they are essentially compressional or expressed by strike slip faulting geological data from the aegean and andes seem to demonstrate that the compressional deformation in the crust above subduction zones is strongly controlled by the stress conditions along convergent boundaries

the north anatolian fault a new look dedicated to the memory of three pioneers ihsan ketin sirri erinc and melih tokay and a recent student aykut barka who burnt himself out in pursuit of the mysteries of the north anatolian fault abstract the north anatolian fault naf is a 1200 km long dextral strike slip fault zone that formed by progressive strain localization in a generally westerly widening right lateral keirogen in northern turkey mostly along an interface juxtaposing subduction accretion material to its south and older and stiffer continental basements to its north the naf formed approximately 13 to 11 ma ago in the east and propagated westward it reached the sea of marmara no earlier than 200 ka ago although shear related deformation in a broad zone there had already commenced in the late miocene the fault zone has a very distinct morphological expression and is seismically active since the seventeenth century it has shown cyclical seismic behavior with century long cycles beginning in the east and progressing westwa

the u series ages of carnotites and implications regarding their formation the u series nuclides 230th 234u 238u 227ac 231pa and 210pb were analyzed in up to 75 carnotites from a group of trenches in southwestern israel though 230th234u had the large range of 0 14 to 0 99 its spatial distribution was not random and the ratio never exceeded unity 231pa230th was at least 91 concordant with 230th234u in four of five cases these facts together with the details of the 230th234u distribution especially among ten samples from one small block of rock indicate that 230th234u ages of carnotites are at least a reasonable approximation of true ages the unexpectedly widespread deficiencies in both 227ac and 210pb indicate that although carnotites are nearly closed to the migration of uranium they are open to those of actinium and to lead radon or radium a model of carnotite precipitation is presented which attributes the large range in 230th234u to a continual shift in the site of carnotite precipitation in keeping with a continual change in the geometry of joints this model may apply to other minerals as well

the hellenic subduction zone a tomographic image and its geodynamic implications new tomographic images of the hellenic subduction zone demonstrate slab penetration in the aegean upper mantle to depths of at least 600 km beneath greece the lower part of the slab appears to be detached at a depth of about 200 km whereas it still seems to be unruptured beneath the southern aegean schematically we derive minimum time estimates for the duration of the hellenic subduction zone that range from 26 to 40 ma this is considerably longer than earlier estimates which vary between 5 and about 13 ma

the north anatolian fault in the sea of marmara 1 using the detailed geometry and tectonics of the main marmara fault that connects the gulf of izmit fault with the ganos fault established by le pichon et al 2001 and the new gps data set recently analyzed by meade et al 2002 we confirm the existence of a marmara block delimited to the north by the northern branch of the north anatolian fault the marmara branch and to the south by the southern branch the kinematics of this block indicate that the marmara branch that crosses the sea of marmara is close to pure dextral strike slip at a rate of 23 mm yr on its whole length the short cinarcik section is the only one where a significant extensional component is predicted a simple kinematic model accounts for slip partitioning there with 8 10 mm yr of extension to the south of the basin and 23 mm yr of dextral strike slip along the northern cinarcik margin the new gps data demonstrate the existence of important asymmetric elastic loading along the main marmara fault that may have significant implications for the seismotectonics of the area the expected future large earthquake may rupture the whole main marmara fault the partitioning in the cinarcik basin may produce magnitude 7 normal faulting earthquakes if their repetition time is about 250 years the 1896 earthquake may have been one of these normal fault earthquakes the marmara block is less than 1 ma prior to its formation it was part of the anatolian block at this time the ganos fault was already a dextral strike slip fault but the fault system in the sea of marmara would have been affected by an extensional component increasing toward the east that accounts for the increasing size of the sedimentary basins eastward

biotic interchange through lowlands of tibetan plateau suture zones during paleogene a substantial biotic interchange took place between gondwanan india and laurasia immediately following the india eurasia collision located just north of the collision zone the role of the tibetan plateau in the geographic interchange of biota is still unknown because lack of fossil evidence here well preserved samara fossils of ailanthus the family simaroubaceae are described from the lunpola and nima basins central tibetan plateau ranging in age from the latest paleocene to the late oligocene these fossils are the largest samara fossils of this genus found so far characteristics such as the main ventral vein located in the intramarginal part of the samara and the stylar scar located on the midline of the seed suggest that they represent a new species which we herein name ailanthus maximus j liu t su et z k zhou sp nov these findings greatly expand the known spatial distribution of ailanthus in the paleogene and suggest that the tibetan plateau has played an important role in the migration of biota between gondwanan india and the northern hemisphere in addition a maximus is morphologically similar to a triphysa a living species which is naturally distributed in tropical and subtropical regions in southeast asia at elevation no more than 600 m indicating a tropical or subtropical lowland environment in the central tibetan plateau during the latest paleocene to late oligocene moreover together with previous paleoaltimetric estimates we propose that tropical or subtropical lowlands along the bangong nujiang suture zone and the yarlung zangpo suture zone existed in some parts of the tibetan plateau during the paleogene only obtained their current elevation during the neogene

pattern of normal faulting in the gediz graben sw turkey hanging wall deformation of the fault systems controlling the southern margin of the gediz graben were investigated separately within the plio quaternary and neogene predominantly miocene deposits of the graben fill fault styles observed in both packages share many similarities in terms of geometry and comprise conjugate fault sets that show clustering of strike orientations predominantly around wnw ese but also sw ne and nw se directions the main difference between the two units is observable in terms of fault dips and rake of the slickenside lineations measured on the exposed fault planes both measurements show a uni modal distribution for the plio quaternary deposits but a tri modal distribution for the neogene deposits this variation is probably related to the geometrical modification of the older faults by the process of domino style back rotation in the hanging wall of higher order faults similarities among the two units are not limited to geometrical aspects of the fault systems but also counts for the orientation of the principal stress axes that controlled the deformation during the deposition of each sedimentary package inversion of the fault slip data showed that approximately n s oriented extension which varies in the range of nnw sse and nne ssw controlled the faulting during the accumulation of the entire graben fill with almost no evidence of change in the state of stress during the graben evolution however some heterogeneity in terms of stress field is observable among the fault systems formed within the same time frame this heterogeneity is probably related to poorly defined direction of extension in the graben indeed low ratio in the order of 0 25 suggests that 2 and 3 are close in magnitudes and the direction of extension is not well constraint with a potential of 2 3 axes permutations local stress field anomalies related to fault segment interaction could also contribute to the observed heterogeneity

active crustal deformation in the marmara sea region nw anatolia inferred from gps measurements deformation in the boundary zone between the anatolian and eurasian plates has been determined by means of repeated global positioning system gps measurements three campaigns 1990 1992 1994 were carried out around the marmara sea the network lies within the active earthquake belt of nw anatolia extending from the western part of the north anatolian fault zone nafz to the aegean extensional province results of the dense network consisting of 52 sites clearly reveal the westward motion of anatolia the rates amount to 17 mm a 3 mm a on average relative to istanbul located at the northeastern edge of the sea of marmara based on the trajectories for the displacements of the observation sites it is concluded that the marmara sea forms a transition zone between the europe fixed region of thrace black sea eurasia and nw anatolia at the western extremity of nw anatolia the motion bends from w to wsw 247 the strain field calculated yields an e w oriented right lateral strike slip movement average 0 12 ppm a maximum 0 41 ppm a accompanied by ne sw extension average 0 12 ppm a maximum 0 52 ppm a at the eastern end of the marmara sea and n s extension at the aegean shore line comparisons with the directions of t axes derived from 65 fault plane solutions of earthquakes show remarkable agreement

westward propagation of the north anatolian fault into the northern aegean timing and kinematics we present new evidence for the propagation processes of the north anatolian fault folding in the dardanelles straits region allows us to document the timing of the deformation preceding and the finite displacement after the passage of the propagating tip of the fault the accuracy of the observations is due to interplay between deformation and the sea level changes in the mediterranean the well known messinian regression followed by the pliocene transgression the long term kinematics around the sea of marmara pull apart total displacement of about 85 km over the past 5 m y is similar to the present day kinematics deduced from space geodesy at a larger scale westward propagation of the north anatolian fault over nearly 2000 km in the past 10 m y appears to be associated with strain recovery suggesting that the continental lithosphere retains long term elasticity

a pulsed extension model for the neogene recent e w trending alasehir graben and the ne sw trending selendi and gordes basins western turkey abstract we have developed a significant body of new field based evidence relating to the history of crustal extension in western turkey we establish that two of the ne sw trending basins in this region the gordes and selendi basins whose sedimentary successions begin in the early miocene are unlikely to relate to late stage alpine compressional orogeny or to e w extension of tibetan type grabens as previously suggested we argue instead that these basins are the result of earlier late oligocene low angle normal faulting that created approximately n s scoop shaped depressions in which clastic to lacustine and later tuffaceous sediments accumulated during early mid miocene time separated by elongate structural highs these basins were later cut by e w trending plio quaternary normal faults that post date accumulation of the neogene deposits in addition we interpret the alasehir gediz graben in terms of two phases of extension an early phase lasting from the early miocene to the late miocene and a young plio quaternary phase that is still active taking into account our inferred earlier phase of regional extension we thus propose a new three phase pulsed extension model for western turkey we relate the first two phases to roll back of the south aegean subduction zone and the third phase to the westward tectonic escape of anatolia

rapid early middle miocene exhumation of the kazdag massif western anatolia apatite fission track analyses indicate that the kazdag massif in northwestern anatolia was exhumed above the apatite partial annealing zone between 20 and 10 ma i e early middle miocene with a cluster of ages at 17 14 ma the structural analysis of low angle shear zones high angle normal faults and strike slip faults as well as stratigraphic analysis of upper plate sedimentary successions and previous radiometric ages point to a two stage structural evolution of the massif the first stage encompassing much of the rapid thermal evolution of the massif comprised late oligocene early miocene low angle detachment faulting and the associated development of small supradetachment grabens filled with a mixture of epiclastic volcaniclastic and volcanic rocks kucukkuyu fm the second stage plio quaternary has been dominated by i strike slip faulting related to the westward propagation of the north anatolian fault system and ii normal faulting associated with present day extension this later stage affected the distribution of fission track ages but did not have a component of vertical normal movement large enough to exhume a new partial annealing zone the thermochronological data presented here support the notion that neogene extensional tectonism in the northern aegean region has been episodic with accelerated pulses in the early middle miocene and plio quaternary

physical analog modeling of pull apart basin evolution abstract pull apart basins are structural depressions formed by localized extension along strike slip fault systems typically at releasing bends or steps in the fundamental strike slip system analog modeling is used to evaluate the sequence of structural evolution of pull apart basins and factors that control their degree of structural asymmetry and geometry basin evolution internal structure and overall symmetry are investigated for oblique releasing step angles and with varying rates of displacement between brittle and ductile crust on opposing sides of the strike slip system while maintaining relative rates between brittle crust on opposing sides of the basin pull apart basin evolution is separated into three stages incipient early and mature incipient pull apart basins are characterized by formation of a normal fault bounded graben or half graben parallel to the oblique step between main strike slip zones in the early stage of formation additional normal faults form toward the basin interior from the original bounding faults and cross basin strike slip faults cut diagonally across the basin interior basin bounding normal fault systems are characterized by lateral variations of fault throw and localized relay ramps in the mature stage of evolution strike slip and normal faults join to completely bound the pull apart basin analog model results indicate that displacement associated with cross basin faults causes development of a through going strike slip fault that links the two main strike slip displacement zones ultimately resulting in a decline in normal fault activity asymmetric symmetric and hybrid pull apart basins all follow the same overall deformation sequence just described the asymmetry of a pull apart basin is controlled by the degree of decoupling between brittle and ductile crust beneath the two crustal blocks in relative motion this is modeled by maintaining a constant relative rate of motion between opposing fault blocks in all models but varying the rate between the blocks and the fixed model basement absolute rate models in which one side of the detachment is fixed with respect to the basement form asymmetric pull apart basins defined by a half graben with the master fault on the mobile side in models where opposing sides of the fault system are equally decoupled from the basement symmetrical pull apart basins form defined by horst and graben structures and master fault dominance switching sides along the length of the basin fault segmentation associated with relatively immature pull apart basins may be capable of arresting earthquake rupture late linkage of main strike slip zones by a cross basin fault could extend potential rupture area dramatically increasing the possibility for large magnitude earthquakes

middle miocene paleoaltimetry of southern tibet implications for the role of mantle thickening and delamination in the himalayan orogen the stable isotope composition of pedogenic and early diagenetic carbonates from the oiyug basin of southern tibet allows model estimates of the paleoaltimetry of the tibetan plateau for the middle miocene pedogenic calcium carbonate nodules have average d 18 occ values of 219 6 whereas nodular lacustrine dolomites range in composition from 27 6 to 25 5 the most negative of the carbonate isotope values can be used to constrain the oxygen isotope composition of paleoprecipitation from which model estimates of paleoaltimetry can be made model results indicate that the southern tibetan plateau achieved elevations of 5200 11370 2605 m by at least 15 ma our results are identical within uncertainty to previous workers paleoelevation estimates based on oiyug basin fossil floral physiognomy this is the first time that two paleoaltimeters have been directly compared and are in accord collectively these data strongly support tectonic models in which thickening of mantle lithosphere beneath the domain of crustal thickening and subsequent detachment of the mantle lithosphere plays an indiscernible role in the elevation history of this part of the himalaya tibet orogenic system

uranium thorium protactinium dating systematics abstract with precise 234u 230th and 231pa data available 230th and 231pa ages can now be tested rigorously for concordancy if the material is not concordant the isotopic characteristics of this material may be examined in some detail here models similar to those used to describe the u pb system are evaluated for use in u th pa studies for the case in which initial 230th and 231pa concentrations are effectively zero the systematics of concordia plots in relation to models of variation in 234u episodic u loss or gain continuous u loss or gain and continuous 234u 230th and 231pa gain or loss are considered for the case in which initial u concentration is significant for example in many carbonate deposits we also examine linear u uptake models for the case in which initial u concentration is effectively zero for example in teeth and bones such models should prove useful in interpreting data from materials that have behaved as open systems in particular these models may help constrain the nature of diagenetic processes and in some situations it may be possible to determine or constrain true ages with materials that have behaved as open systems

asymmetric slip partitioning in the sea of marmara pull apart a clue to propagation processes of the north anatolian fault between 1939 and 1999 the north anatolian fault naf experienced a westward progression of eight large earthquakes over 800 km of its morphological trace the 2000 km long north anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale 10 myr the sea of marmara is a large pull apart that appears to have been a geometrical mechanical obstacle encountered by the naf during its propagation the present paper focuses on new high resolution data on the submarine fault system that forms a smaller pull apart beneath the northern sea of marmara between two well known strike slip faults on land izmit and ganos faults the outstandingly clear submarine morphology reveals a segmented fault system including pull apart features at a range of scales which indicate a dominant transtensional tectonic regime there is no evidence for a single continuous purely strike slip fault this result is critical to understanding of the seismic behaviour of this region of the naf close to istanbul additionally morphological and geological evidence is found for a stable kinematics consistent both with the long term displacement field determined for the past 5 myr and with present day anatolia eurasia motion determined with gps however within the sea of marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull apart the loading associated with the westward propagation process of the naf may have provided a favourable initial geometry for such a slip separation

s p wave traveltime residuals from earthquakes and lateral inhomogeneity in the upper mantle beneath the aegean and the hellenic trench near crete

m 7 earthquake rupture forecast and time dependent probability for the sea of marmara region turkey we forecast time independent and time dependent earthquake ruptures in the marmara region of turkey for the next 30 years using a new fault segmentation model we also augment time dependent brownian passage time bpt probability with static coulomb stress changes cff from interacting faults we calculate mw 6 5 probability from 26 individual fault sources in the marmara region we also consider a multisegment rupture model that allows higher magnitude ruptures over some segments of the northern branch of the north anatolian fault zone beneath the marmara sea a total of 10 different mw 7 0 to mw 8 0 multisegment ruptures are combined with the other regional faults at rates that balance the overall moment accumulation we use gaussian random distributions to treat parameter uncertainties e g aperiodicity maximum expected magnitude slip rate and consequently mean recurrence time of the statistical distributions associated with each fault source we then estimate uncertainties of the 30 year probability values for the next characteristic event obtained from three different models poisson bpt and bpt cff using a monte carlo procedure the gerede fault segment located at the eastern end of the marmara region shows the highest 30 year probability with a poisson value of 29 and a time dependent interaction probability of 48 we find an aggregated 30 year poisson probability of m 7 3 earthquakes at istanbul of 35 which increases to 47 if time dependence and stress transfer are considered we calculate a twofold probability gain ratio time dependent to time independent on the southern strands of the north anatolian fault zone

cenozoic aridification in northwest china evidenced by paleovegetation evolution abstract although the cenozoic aridification of the asian interior was of global significance the timing of its evolution and the drivers remain controversial however knowledge of the spatiotemporal pattern of vegetation evolution can inform our understanding of the aridification process here we integrate 58 pollen records with well constrained chronologies from across asia and use the biomization method to quantitatively reconstruct the cenozoic evolution of the vegetation the results reveal the occurrence of desert in northwest china during 43 35 ma indicating a dry climate after 22 ma there was a further expansion of desert and steppe in northwest china indicating the existence of a permanent arid environment the aridity was intensified after 8 7 ma evidenced by the replacement of forest by steppe and desert we suggest that the permanent aridification since 22 ma was related to the uplift of the tibetan plateau and that the enhanced aridification since 8 7 ma was caused by ongoing global cooling

late oligocene early miocene evolution of the lunpola basin central tibetan plateau evidences from successive lacustrine records abstract widespread cenozoic sediments in and around the tibetan plateau tp are thought to have played an important role in explaining the process of the india asia collision as well as its interactions with global and regional paleoclimate however high resolution temporal frameworks of sedimentary sequences and controls on geological and climatic events are still absent to study the abovementioned issues we investigate the oligocene miocene lacustrine sequences the dingqinghu formation of the lunpola basin central tp in this work cyclostratigraphic analyses are conducted with gamma ray log and pollen data to establish a high resolution temporal framework ranging from ca 25 4 to 18 0 ma for the sections along these sections sediment accumulation rates are calculated with orbital signals to monitor clastic input of the lake basin elemental palynological and isotopic data are summarized to depict the paleoclimate and paleoelevation evolution of this drainage system integrating all these clues together we sort out a chronological list of events including lake basin tectonics and paleoclimate regional uplift took place at 23 7 ma simultaneously a distinct lake basin transition characterized by accelerated sediment accumulation rate is recognized about 0 2 ma later at 23 5 ma catchment scale drought occurred and maintained to the end of the sections our results demonstrate that paleoclimate did not impose decisive influence on the late oligocene early miocene evolution of the lake basin instead regional uplift and its associated accelerated exhumation of the source area resulted in the lake basin transition and paleoclimatic drought after reviewing the oligocene miocene sedimentary records distributed in and around the tp we argue that the 23 7 ma geological event of the lunpola basin is probably not a single case but a regional effect of a dramatic tectonic transition of the plateau

uranium series dating of carnotites concordance between 230th and 231pa ages abstract 231 pa 235 u and 230 th 234 u ages were determined for 17 carnotites from two areas in israel for this purpose a simplified one step method was used to purify the protactinium the extraction into tta thenoyl trifluoro acetone at high acidity using the test of concordance between the two dating methods 12 of the 17 carnotites were found to have acted as closed chemical systems whereas 4 seem to have gained uranium the details of the relationships between the 231 pa 235 u and the 230 th 234 u ages suggest that the uranium gain which took place in the latter 4 cases occurred in a manner which was approximately continuous and linear

the bursa gonen depression nw turkey a complex basin developed on the north anatolian fault in this study we show that the southern branch of the north anatolian fault has been active since late pliocene time and that evidence of activity is supported by geological and seismological data the southern branch of the north anatolian fault consists of four segments from west to east yenice gonen manyas mustafakemalpasa uluabat and bursa these faults delimit the bursa gonen depression with the bandirma mudanya uplift to the north and uludag sularya uplift to the south the bursa gonen depression includes upper pliocene to recent sediments that thicken to the south suggesting a deposition pattern under active fault control study of fault kinematics suggests that the bursa gonen depression started as a small pull apart basin during late pliocene time and then evolved to a large depression the faults delimiting this depression are still active and capable of producing future earthquakes

regional scale tectonic evolution and the seismic velocity structure of the lithosphere and upper mantle the mediterranean region we present a numerical modeling approach designed for the verification of tectonic reconstructions and for a quantitative analysis of the seismic velocity structure of the lower lithosphere and upper mantle in this forward modeling procedure we use published reconstructions of the tectonic evolution of a region to predict the thermal structure from which we calculate physical quantities like p wave velocity basin subsidence and basement heat flow we show an application of this approach to two reconstructions of the late mesozoic and cenozoic evolution of the mediterranean region the resulting synthetic velocity models are tested against seismological models of the mantle structure obtained independently by delay time tomography subsidence and heat flow predictions are compared with actual observations to further constrain the geological assumptions underlying the forward models the mantle models predicted from reconstructions of the evolution of the mediterranean region correlate with major features in the tomographic images from our model results we conclude that the present distribution of seismic velocities in the mediterranean region is largely determined by the tectonic evolution during at least the last 40 m y this means we can verify processes represented in different tectonic scenarios with the seismologically determined velocity structure seen from a different perspective the model results contribute to understanding the causes of the velocity structure imaged by delay time tomography by showing how the tectonic evolution results in this structure

palaeomagnetic study of block rotations in the niksar overlap region of the north anatolian fault zone central turkey abstract this palaeomagnetic study investigates crustal deformation within and adjacent to the niksar overlap area of the north anatolian fault zone nafz in central east turkey the studied rock formations comprise 1 red limestones of late cretaceous age 3 sites 2 mafic lavas of eocene age on the north side 13 sites and south side 9 sites of the nafz and 3 volcanic rocks of pliocene quaternary age from the niksar pull apart basin within the nafz 8 sites comparisons with reference palaeofield directions computed from apparent polar wander paths of the eurasian and afro arabian plates identify two scales of regional and local tectonic rotation 1 1 a pre tilting remanence in the eocene volcanic rocks south of the nafz d i 144 1 47 5 95 7 6 is interpreted to reflect counterclockwise rotation by 30 40 from the reference palaeofields contemporaneous volcanic rocks from the north side of the nafz have the same reverse polarity recorded in pre tilting magnetisations the remanence is also rotated counterclockwise d i 152 4 42 5 95 11 3 but by about 8 less than the volcanics on the south side of the nafz hence similar amounts of rotation are observed on both sides of the nafz and are interpreted to reflect motions during the pre middle miocene collisional history in this sector of the pontides no distributed clockwise rotations anticipated from subsequent dextral motion along the nafz intracontinental transform are observed the slightly larger anticlockwise rotation found on the south side of the nafz probably records relative rotation of en echelon wedges by continental escape during post middle miocene strike slip along the transform 2 2 within the narrow zone of intense deformation along the nafz cretaceous limestones appear to be rotated clockwise by dextral strike slip motion whilst plio quaternary lavas within a fault bounded block in the overlap region associated with the niksar pull apart basin have magnetisations consistently directed 240 270 e magnetic inclinations are not diagnostic of polarity but both polarity solutions identify rapid clockwise rotation at rates in excess of 50 m y a normal polarity solution is favoured and implies that a block ca 5 km across has undergone a strike slip displacement of around 12 km within the nafz during the last polarity chron cretaceous eocene palaeolatitudes are closer to those predicted from eurasia than afro arabia but a study of older rocks is required to resolve affinities of this sector of the anatolian block theoretical models of crustal deformation across intracontinental transforms obeying power law behaviour and treating the lithosphere as a viscous medium predict that distributed clockwise rotations should be observed about as broad across the nafz these rotations are not observed instead intense clockwise rotation is confined to a narrow zone close to the major fault break the concentration of historic seismic activity here also implies that the bulk of the dextral motion between the eurasian plate and the anatolian block is accommodated by slip along faults close and parallel to the main trace of the nafz

revisiting of the paleocene orthopteran insect hylophalangopsis chinensis lin and huang 2006 in northern tibet abstract in the dazhuoma stratigraphic section near the gangni township amdo county northern tibet china the paleocene lower eocene niubao formation yields plenty of well preserved microfossils and insects a restudy of hylophalangopsis chinensis lin and huang 2006 an orthopteran insect from this formation indicates that it should be attributed to zeuneropterinae of stenopelmatidae instead of prophalangopsidae of hagloidea in the original study some characters preserved in this species are herein considered transitional between aboilinae prophalangopsidae and stenopelmatoidea supporting the deduction that a close relationship exists between stenopelmatoidea and aboilinae the close relationship of hylophalangopsis with the other zeuneropterines in canada and scotland indicates a middle late paleocene age for the lower niubao formation supported by some previous studies and further suggests a warm and humid climate in the dazhuoma area in the middle late paleocene supported by some important evidence

geodetic constraints on the tectonic evolution of the aegean region and strain accumulation along the hellenic subduction zone article i nfo we present evidence that gps velocity estimates of plate motions and fault slip rates agree to within uncertainties with geologic estimates during the most recent phase of the geologic evolution of the e mediterranean region post late miocene on this basis we use the gps differential velocities to estimate the timing of initiation of the principal structures in nw turkey the n aegean sea and central greece including the marmara sea the gulfs of evia goe and corinth goc and the kephalonia transform fault ktf we interpret these ages to indicate that the north anatolian fault propagated across the n aegean opening the goe and goc and initiating the ktf during the past 1 4 ma we further suggest that aegean extension that was earlier more distributed across the aegean basin became focused on this new fault system allowing the southern aegean and peloponnisos to translate sw with little internal deformation as observed today with gps this change in tectonic configuration may account for the clear geologic evidence for crustal thinning throughout the s aegean in apparent contradiction with low present day strain rates we further show that the low present day strain rate along the southern edge of the aegean micro plate requires substantial aseismic slip along the plate interface below crete consistent with the low level of historic subduction type earthquakes along this segment of the subduction zone

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

low elevation of the northern lhasa terrane in the eocene implications for relief development in south tibet the uplift history of tibet is crucial for understanding the geodynamic and palaeoclimatologic evolution of asia however the pattern of plateau uplift through space and time remains unresolved we use stable isotope data from palaeosol carbonates to reconstruct the eocene 46 ma elevation of the tangra yum co region northern lhasa terrane the difference between the oxygen isotopic compositions of the studied palaeosols and eocene surface water near the source of the indian monsoon indicates a palaeoelevation of 2590 730 910 m for tangra yum co present altitude 4600 m a similar palaeoaltitude is obtained by comparing our data with modern soils and taking past environmental changes into account combining our results with published palaeoelevation estimates for tibet suggests significant relief 2 km during the eocene when a low lying basin in the northern lhasa terrane was bounded by the qiangtang and gangdese mountain belts to the north and south respectively

fossil palm beetles refine upland winter temperatures in the early eocene climatic optimum eocene climate and associated biotic patterns provide an analog system to understand their modern interactions the relationship between mean annual temperatures and winter temperatures temperature seasonality may be an important factor in this dynamic fossils of frost intolerant palms imply low eocene temperature seasonality into high latitudes constraining average winter temperatures there to 8 c however their presence in a paleocommunity may be obscured by taphonomic and identification factors for macrofossils and pollen we circumvented these problems by establishing the presence of obligate palm feeding beetles chrysomelidae pachymerina at three localities a fourth tentatively in microthermal to lower mesothermal early eocene upland communities in washington and british columbia this provides support for warmer winter eocene climates extending northward into cooler canadian uplands

paleocene eocene record of ophiolite obduction and initial india asia collision south central tibet 1 uppermost cretaceous to eocene marine sedimentary sequences occur both to the south and north of the yarlung zangbo suture in south central tibet they consist of indian margin strata of the northern tethyan himalaya and asian margin strata of the gangdese forearc both assemblages are characterized by major changes in depositional environment and sedimentary provenance at 65 ma and an appearance of detrital chromium rich spinel of ophiolite affinity tio2 generally 0 1 wt during the paleocene ophiolitic melange exposed along the suture could have provided a source for detrital spinel the melange occurs in the hanging wall of a north dipping south directed mylonitic shear zone which includes a tectonic sliver of mafic schist amphibole from the schist yields 40ar 39ar ages of 63 ma which we attribute to cooling during slip along the shear zone and southward obduction of the melange melange obduction was coeval with the development of an angular unconformity within the gangdese forearc basin to the north between late maastrichtian time and 62 ma upper paleocene to middle eocene sandstones in the northern tethyan himalaya yield 200 120 ma u pb detrital zircon ages and 190 170 ma 40ar 39ar detrital mica ages these detrital grains were most likely sourced from regions north of the yarlung zangbo suture suggesting that onset of india asia collision in south central tibet is middle eocene or older in age collectively our results support previous suggestions that oceanic rocks were obducted onto the northern margin of india during latest cretaceous earliest tertiary time coeval changes in gangdese forearc sedimentation raise the possibility that this obduction event marks onset of tectonic interaction between india and asia at 65 ma alternatively in concert with the conventional view of eocene collision initiation the obducted oceanic rocks may be of intraoceanic origin while coeval changes in gangdese forearc sedimentation may be a consequence of an increase in the rate of ocean continent convergence following the demise of the intraoceanic subduction zone

stratigraphic response and mammalian dispersal during initial india asia collision evidence from the ghazij formation balochistan pakistan initial continental collision between india and asia is thought to have caused significant changes to global climate and biota yet its timing and biogeographic consequences are uncertain structural and geophysical evidence indicates initial collision during the early paleogene but sedimentary evidence of this has been controversial owing to the intense deformation and metamorphism along the suture zone modern orders of mammals that appeared abruptly on northern continents coincident with the global warming event marking the paleocene eocene boundary are hypothesized to have originated on the indian subcontinent but no relevant paleontological information has been available to test this idea here we present new paleomagnetic sedimentologic and paleontologic evidence to show that the lower eocene ghazij formation of western pakistan records continental sedimentation and mammalian dispersal associated with initial india asia collision our results are consistent with the initial collision occurring near the paleocene eocene boundary but modern orders of mammals appeared later in indo pakistan and thus did not likely originate on the indian subcontinent

counterclockwise rotation of the anatolian block abstract seismological and other data from the boundaries of anatolia are used to discuss the motion and plate tectonics of this block models which include a rotation of anatolia around a single pole are shown to be inconsistent with much of this data in particular a westward motion of anatolia which is the most commonly used model should be reconsidered models which use a single pole of rotation fail because they assume the north anatolian fault to be an ideal transform fault which describes all of the motion between anatolia and the black sea in effect internal deformation in the form of extension in western anatolia and for the most part strike slip faulting in eastern anatolia are important and account for some of the relative motion thus a more appropriate model for this region is one which not only stresses the dominance of the north anatolian fault but also recognises the importance of internal deformation and the limitation of classic plate tectonic models which this deformation implies the preferred model for the motion of anatolia is a nonuniform tight counterclockwise rotation approximated by the shape of the north anatolian fault as well as by the faults which splay from it to the south such a model is consistent with data from the boundaries of anatolia including the source mechanism of earthquakes and depth of benioff zone along the southern boundary of the block counterclockwise rotation of anatolia is the natural consequence of the collision of arabia with eastern anatolia coupled with subduction in the eastern mediterranean

high relief topography of the nima basin in central tibetan plateau during the mid cenozoic time abstract there remains inconsistence of uplift history of the tibetan plateau here we estimated paleoelevation of mid cenozoic nima basin located in central tibet using multi proxies they included meteoric water and vegetation isotope proxies based on hydrogen and carbon isotopic compositions d and 13c respectively of terrestrial plant wax lipid of n alkanes and temperature proxy derived from microbial membrane lipid of branched glycerol dialkyl glycerol tetraethers brgdgts lipid analysis on sedimentary rocks in the nima basin yielded 222 12 and 30 0 0 7 for d and 13c of n c29 alkane respectively and brgdgt derived mean annual air temperature maat of 21 5 3 1 c for the paleo basin using the sea level meteoric water 18o and miocene siwalik paleovegetation 13c as low elevation references values of d and 13c of n c29 alkane in this study suggested paleoelevations of 4546 m and 2800 m respectively whereas by using a subtropical sea surface temperature as a reference brgdgt derived maats suggested a paleoelevation of 893 m we believed that the three estimates reflect a high relief topography in the study basin during the mid cenozoic representing elevations of orographic barrier of southerly oceanic moisture basin catchment and basin lake level respectively this scenario implies a low elevation of the basin relative to the lhasa terrane located to the south during the mid cenozoic hence challenging the classical crustal thickening models assuming a simple crustal thickening uplift relationship

uranium series chronology and environmental applications of speleothems an increasing number of scientists recognize the value of speleothems1 as often extremely well preserved archives of information about past climate vegetation hydrology sea level nuclide migration water rock interaction landscape evolution tectonics and human action well constrained data are required to document past changes reconstruct past patterns and predict future responses of the earth system at a wide range of spatial and temporal scales speleothems are particularly useful in this regard because they can be found in many locations of the globe sampled at high resolution and reliably dated using high precision uranium series techniques speleothems are bodies of mineral material formed in caves as the result of chemical precipitation from groundwater flowing or dripping in a cave most speleothems are composed of calcite formed by slow degassing of co2 from supersaturated groundwater but aragonite and gypsum forms are also common particularly near cave entrances where evaporative effects are important a host of different speleothem types decorate the walls ceilings and floors of caves and their mineralogy and morphology is a function of fluid flow and chemistry of waters feeding a particular location as well as the ambient conditions temperature chemistry light in the air or water filled void subaerial forms include the familiar stalagmites stalactites draperies flowstones subaqueous forms include rimstone pools rafts mammillary calcite wall coatings and dog tooth spar for an extensive review of the types of speleothem that have been observed see hill and forti 1997 speleothems are used in a multitude of ways to explore past environmental conditions perhaps the most fundamental of which is their very presence or absence deposition of speleothems relies on sufficient water supply and soil co2 to enable dissolution and transport of reactants in the vadose zone to underlying caves in arid or glacial times conditions may not have been favorable for speleothem formation

palaeo altimetry of the late eocene to miocene lunpola basin central tibet the elevation history of the tibetan plateau provides direct insight into the tectonic processes associated with continent continent collisions here we present oxygen isotope based estimates of the palaeo altimetry of late eocene and younger deposits of the lunpola basin in the centre of the plateau which indicate that the surface of tibet has been at an elevation of more than 4 kilometres for at least the past 35 million years we conclude that crustal but not mantle thickening models combined with plate kinematic solutions of india asia convergence are compatible with palaeo elevation estimates across the tibetan plateau

active faults and evolving strike slip basins in the marmara sea northwest turkey a multichannel seismic reflection study abstract the north anatolian fault is a 1200 km long transform fault forming the boundary between the anatolian and eurasian plates near its western end it strikes through the marmara sea and is responsible for the creation of three deep marine depressions the north anatolian fault system and the linked basins in the eastern marmara sea were studied using newly acquired multi channel seismic reflection data in the marmara sea the north anatolian fault consists of a main strand and a few subsidiary branches the main strand is made up of the ganos 15 km long central marmara 105 km and north boundary 45 km fault segments the north boundary fault joins in the east to the izmit segment which was ruptured during the m s 7 4 earthquake on 17 8 1999 the north boundary fault is highly oblique to the regional displacement vector which results in the generation of a symmetrical fault wedge basin this cinarcik basin is a wedge shaped deep marine depression south of istanbul it is about 50 km long up to 20 km wide and 1250 m deep and is filled with pliocene to quaternary sediments over 3 km thick the north boundary fault joins in the west to the transpressional central marmara fault around the restraining segment boundary the syntransform sediments are being deformed into a large anticlinorium the cinarcik basin started to form when the westward propagating north anatolian fault intersected a northwest trending pre existing fault zone during the pliocene and bifurcated into nw and sw trending segments forming a transform transform transform type triple junction dextral strike slip movement along the arms of the triple junction led to the development of the cinarcik basin the present fault geometry in the marmara region was achieved later during the mid pliocene following the termination of the triple junction geometry south of the main north anatolian fault system there is a second active strike slip fault in the marmara sea made up of several segments a highly asymmetrical fault bend basin comprising pliocene quaternary sediments over 2 5 km thick is forming along a releasing fault segment of this south boundary fault system

tectonic evolution of the niksar and tasova erbaa pull apart basins north anatolian fault zone their significance for the motion of the anatolian block abstract the tasova erbaa and niksar basins are two adjacent pull apart basins along the north anatolian fault zone nafz within the tasova erbaa basin sedimentary lithofacies of the upper pontus formation plio pleistocene are asymmetrically distributed with laterally derived alluvial fans coarse braid plain deposits and axial braided stream deposits dominating the northern and western parts of the basin the basin has gently dipping sediments locally affected by pervasive extensional t faulting isolated compressional structures are associated with master faults deformation zone width 500 m pervasive extensional faults t and r and late stage pdz parallel compressional faults are also present an additional set of extensional faults trends perpendicular to the pdz accommodating secondary pull apart stretching within the basin the distribution of sedimentary facies and structural styles is consistent with that predicted by models for pull apart basins the adjacent niksar basin is an active pull apart basin possibly as young as 0 5 1 ma its modern drainage and sedimentary facies are symmetrically arranged adding the lengths of the tasova erbaa and niksar basin suggests 80 km total displacement along the north anatolian fault which is consistent with seymen itu ph d thesis 1975 sengor j geol soc 136 1979 269 282 and armijo et al tectonophysics 243 1999 135 154 who observed about 85 5 km total displacement along the north anatolian fault the change in course of the north anatolian fault marked by the formation of the niksar ezinepazari segment and this new geometry suggest that the anatolian block is rotating anticlockwise by having two separate poles one located near damascus and the other occurring north of the sinai peninsula this change may also mark the transfer of the anatolian triple junction from erzincan to karliova about 1 ma ago furthermore it appears that while the fault shortcuts the older basin a new generation of pull apart basins is formed due to changes of boundary conditions along the fault zone

global positioning system constraints on plate kinematics and dynamics in the eastern mediterranean and caucasus we present and interpret global positioning system gps measurements of crustal motions for the period 1988 1997 at 189 sites extending east west from the caucasus mountains to the adriatic sea and north south from the southern edge of the eurasian plate to the northern edge of the african plate sites on the northern arabian platform move 18 2 mm yr at n25 5 w relative to eurasia less than the nuvel 1a circuit closure rate 25 1 mm yr at n21 7 w preliminary motion estimates 1994 1997 for stations located in egypt on the northeastern part of africa show northward motion at 5 6 2 mm yr also slower than nuvel ia estimates 10 1 mm yr at n2 4 e eastern turkey is characterized by distributed deformation while central turkey is characterized by coherent plate motion internal deformation of 2 mm yr involving westward displacement and counterclockwise rotation of the anatolian plate the anatolian plate is de coupled from eurasia along the right lateral strike slip north anatolian fault naf we derive a best fitting euler vector for anatolia eurasia motion of 30 7 0 8 n 32 6 0 4 e 1 2 0 1 myr the euler vector gives an upper bound for naf slip rate of 24 1 mm yr we determine a preliminary gps arabia anatolia euler vector of 32 9 1 2 n 40 3 1 1 e 0 8 0 2 myr and an upper bound on left lateral slip on the east anatolian fault eaf of 9 1 mm yr the central and southern aegean is characterized by coherent motion internal deformation of 2 mm yr toward the sw at 30 1 mm yr relative to eurasia stations in the se aegean deviate significantly from the overall motion of the southern aegean showing increasing velocities toward the trench and reaching 10 1 mm yr relative to the southern aegean as a whole

the aegean sea we summarize briefly the main features of a kinematic model of evolution of the aegean area since 13 ma the formation of the aegean sea by extensional tectonics is related to the subduction of the mediterranean floor below the hellenic arc we then make a quantitative estimate of vertical movements in the aegean area on the basis of geological data and demonstrate that the outer arc was built since the beginning of this episode of subduction by vertical uplift the easiest way to explain the uplift is by underplating finally we discuss briefly the dynamics of the subduction marginal sea formation processes in this continental collision framework

estimates of seismic potential in the marmara sea region from block models of secular deformation constrained by global positioning system measurements we model the geodetically observed secular velocity field in north western turkey with a block model that accounts for recoverable elastic strain ac cumulation the block model allows us to estimate internally consistent fault slip rates and locking depths the northern strand of the north anatolian fault zone nafz carries approximately four times as much right lateral motion 24 mm yr as does the southern strand in the marmara sea region the data show strain accu mulation to be highly localized we find that a straight fault geometry with a shallow locking depth of 6 7 km fits the observed global positioning system velocities better than does a stepped fault geometry that follows the northern and eastern edges of the sea this shallow locking depth suggests that the moment release associated with an earthquake on these faults should be smaller by a factor of 2 3 than previously inferred assuming a locking depth of 15 km online material an updated version of velocity field data

gps and geologic estimates of the tectonic activity in the marmara sea region nw anatolia a dense network of 52 global positioning system gps sites is used to determine the velocity field and strain rate pattern at the western end of the north anatolian fault zone nafz in the marmara sea region nw anatolia based on four gps campaigns carried out biannually between 1990 and 1996 the detailed kinematic field of crustal motion is calculated the southernmost station shows an average rate of 22 3 mm yr oriented westward relative to istanbul eurasia this value is indicative of the dextral strike slip motion of nw anatolia relative to the black sea the gps velocity field reveals that the sites located on the thrace black sea block show negligible motion relative to istanbul the gps based deformation pattern of three sections crossing the westward prolongation of the nafz is compared with neotectonic data both the gps and the neotectonic data give clear evidence that most of the deformation occurs along a relatively narrow e w oriented zone this belt extends from the single fault trace of the nafz through the gulf of izmit the marmara sea the arkoy region and the gulf of saros into the north aegean trough nat in addition the cross sections show the increasing influence of the n s oriented extension in the aegean sea region from the comparison of the directions and rates of shear and normal strain deduced from gps data with geologic and seismic observations we conclude that the most active zone of dextral shear follows a line along mudurnu valley the northern marmara sea and the saros trough where it joins the nat

high and dry in central tibet during the late oligocene the time at which the tibetan plateau rose to its present high elevation remains controversial with estimates ranging from 40 ma to more recent than 7 ma new stable isotope analyses of modern and accurately dated ancient paleosol carbonate in the nima basin of central tibet point to an arid climate and high paleoelevation 4 5 5 km comparable to today s setting by 26 ma oxygen isotope values of ancient 26 ma soil carbonate are both very negative and indistinguishable after modest corrections for changes in global climate from the lowest least evaporated oxygen isotope values of modern soil carbonates in the area substantial enrichments in oxygen 18 in paleolacustrine carbonates as well as high carbon isotope values from paleosol carbonates indicate considerable lake evaporation and low soil respiration rates respectively and both are consistent with the present arid climate of the nima area blockage of tropical moisture by the himalaya and perhaps the gangdese shan probably has contributed strongly to the aridity and very negative oxygen isotope values of soil carbonate and surface water in the nima area since at least the late oligocene the maintenance of high elevation since at least 26 ma suggests that any flow of lower crust from beneath central tibet must have been balanced by coeval northward insertion of indian crust beneath the plateau

geodetic determination of the kinematics of central greece with respect to europe implications for eastern mediterranean tectonics we use a new satellite laser ranging global positioning system slr gps solution at seven sites in anatolia and aegea to obtain a better definition of the extrusion motion of the anatolian aegean block with respect to europe we show that this motion can be described in a first approximation by a counterclockwise rotation which transfers most of the motion of arabia to anatolia we combine 78 displacement vectors obtained at common points of two triangulation nets measured in central greece in 1895 and 1975 with the slr gps measurements to compute the velocity field over greece with respect to europe these measurements indicate that central greece is a zone of extension between the anatolian aegean counterclockwise rotation to the south and the northern greece clockwise rotation to the north this extension is principally localized within the gulf of corinth to the east but is distributed to the west we then extrapolate this velocity field to the whole aegea and western anatolia using recently published gps results as well as the slr results the narrow dextral north anatolian fault which limits the velocity field to the north progressively gives way to a much wider boundary zone where extension becomes dominant we show that the collision between the mediterranean ridge and africa began 3 6 ma and we describe the modifications that this collision has produced on the kinematic pattern both in aegea and on the mediterranean ridge