late pleistocene uplift history along the southwestern marmara sea determined from raised coastal deposits and global sea level variations pleistocene raised coastal deposits characterized by locally abundant shells aragonite cemented beachrock and associated nearshore deposits border the western marmara sea at elevations of 0 50 m field observations confirm that these deposits formed during a series of transgressive and regressive events u th dates in 16 in situ shells from four localities show that the peak of the transgressions occurred during the highstands of oxygen isotopic stages 7 and 5 between 53 and 210 ka the elevations of these dated deposits can be used to quantify their post depositional uplift and indicate that the entire western marmara shelf including the strait of canakkale dardanelles has been rising at an average rate of 0 40 mm yr 1 since 225 ka the primary cause of uplift is the local compression associated with a restraining bend in the western segment of the north anatolian fault paleogeographic maps constructed using the average rate of tectonic uplift and detailed topographic and bathymetric maps reveal that prior to glacial oxygen isotopic stage 8 the marmara sea was never isolated from the aegean sea even when global sea level was low because the floor of the strait of canakkale was too deep early in its uplift history the dominance of mytilus edulis in raised coastal terraces dating from the lowstand of glacial oxygen isotopic stage 8 suggests that the degree of communication between the aegean sea and marmara sea was comparable to that of the present during the peak of glacial oxygen isotopic stage 6 the floor of the strait was subaerially exposed isolating the marmara sea for the first time in the pleistocene from the higher salinity mediterranean water inflow and possibly causing it to become a blackish water lake during interglacial isotopic stages 9 7 and 5 the strait of canakkale was very wide and deep 100 125 m and there were two subsidiary channels bolayir and eceabat channels providing additional links between the aegean sea the marmara sea further promoting significant water exchange between these basins the dominance of ostrea edulis in the raised terraces dating from isotopic stages 5 and 7 confirms an enhanced penetration of the mediterranean water mass into the marmara sea the history of communication between the black sea fed by central and northern european drainage systems and the low latitude mediterranean sea is of fundamental importance in understanding the genesis of organic rich sapropel deposits throughout the region the results presented in this paper caution against the simple assumption that sea level change alone controlled the degree of connection across this oceanographic gateway instead the physiography and paleoceanography of the region were controlled both by variations in global sea level and the rate of uplift in an area of active transpression

charging of the neogene penglai 19 3 field bohai bay basin china oil accumulation in a young trap in an active fault zone the penglai 19 3 pl19 3 oil field the largest offshore oil field in china was found in shallow reservoirs 700 1700 m 2297 5577 ft within the most active fault zone in east china the pl19 3 anticline was not finally formed until about 2 0 ma and is cut by densely distributed faults source rock and crude oil samples from the pl19 3 field were analyzed to determine the origin and formation mechanisms of this large oil field three organic rich oil prone source rock intervals exist in the bozhong subbasin each of which has a distinct biomarker assemblage oil samples from different wells have different biomarker associations and three source related oil classes were identified within the pl19 3 field based on biomarker compositions and multivariate analysis of the data the pl19 3 field displays considerable compositional heterogeneity the compositional heterogeneity within the field and comparison between oil samples from the pl19 3 field and those from nearby structures suggest three field filling directions which is consistent with the results of migration pathway modeling the pl19 3 field was charged in the north by oil generated from dongying formation source rocks in the eastern bozhong depression and bodong depression in the southeast by oil generated from shahejie formation source rocks in the miaoxi depression and in the northwest by oil generated from shahejie formation source rocks in the central bozhong depression oil charge from multiple source rock intervals and multiple generative kitchens and focusing of oil originating from a large area of the bozhong depression into the same trap resulted in rapid oil accumulation in the pl19 3 structure and the formation of this large oil field in a very young trap within an active fault zone

reservoir characteristics and their effects on hydrocarbon accumulation in lacustrine turbidites in the jiyang super depression bohai bay basin china abstract a great difference exists between the hydrocarbon charging characteristics of different tertiary lacustrine turbidites in the jiyang super depression of the bohai bay basin east china based on wireline log data core observation and thin section analyses this study presents detailed reservoir property data and their controlling effects from several case studies and discusses the geological factors that govern the hydrocarbon accumulation in turbidite reservoirs the lacustrine fluxoturbidite bodies investigated are typically distributed in an area of 0 5 10 km2 with a thickness of 5 20 m the sandstones of the tertiary turbidites in the jiyang super depression have been strongly altered diagenetically by mechanical compaction cementation and mineral dissolution the effect of compaction caused the porosity to decrease drastically with the burial depths especially during the early diagenesis when the porosity was reduced by over 15 the effect of cementation and mineral dissolution during the late stage diagenesis is dominated by carbonate cementation in sandstones high carbonate cement content is usually associated with low porosity and permeability carbonate dissolution secondary porosity zone and primary calcite dissolution is believed to be related to thermal maturation of organic matter and clay mineral reactions in the surrounding shales and mudstone two stages of carbonate cementation were identified the precipitation from pore water during sedimentation and secondary precipitation in sandstones from the organic acid dissolved carbonate minerals from source rocks petrophysical properties have controlled hydrocarbon accumulation in turbidite sandstones high porosity and permeability sandstones have high oil saturation and are excellent producing reservoirs it is also noticed that interstitial matter content affects the oil bearing property to some degree there are three essential elements for high oil bearing turbidite reservoirs excellent pore types low carbonate cement 15 and average permeability 10 md

continental crust composition constrained by measurements of crustal poisson s ratio deciphering the geological evolution of the earth s continental crust requires knowledge of its bulk composition and global variability the main uncertainties are associated with the composition of the lower crust seismic measurements probe the elastic properties of the crust at depth from which composition can be inferred of particular note is poisson s ratio this elastic parameter can be determined uniquely from the ratio of p to s wave seismic velocity and provides a better diagnostic of crustal composition than either p or s wave velocity alone1 previous attempts to measure have been limited by difficulties in obtaining coincident p and s wave data sampling the entire crust2 here we report 76 new estimates of crustal spanning all of the continents except antarctica we find that on average increases with the age of the crust our results strongly support the presence of a mafic lower crust beneath cratons and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions followed by magmatic underplating or a model in which crust formation processes have changed since the precambrian era

neotectonics in the eastern north anatolian fault region turkey advocates crustal extension mapping from sar ers imagery and digital elevation model abstract this paper concerns the neotectonics of the eastern part of the anatolian block bounded respectively to the north and the east by the north anatolian naf and the east anatolian faults eaf meeting at karliova the study is based on imagery of synthetic aperture radar sar scenes acquired by the european remote sensing ers satellite and on views of a digital elevation model dem complemented with fault analysis in the field we show that extensional tectonics associated with transcurrent displacements prevail in the karliova triangle and beyond new local releasing bends or pull apart basins and push up structures along the naf have been demonstrated more importantly anatolia is composed of blocks less than 50 km in width that are tilted and move relative to each other they are compatible with a detachment within the crust of anatolia we argue that an escape wedge has migrated through time from west to east with successive jumps to form the present day karliova triangle at each stage the escape wedge was easterly bounded by a ne sw striking fault zone similar to the eaf in each escape wedge clockwise block rotations predate strike slip tectonics along the n110 e striking naf this is the case for instance for the erzincan basin where the first movements were parallel to the sw striking ovacik fault an early equivalent of the eaf and turned later to the west the detached crustal blocks moved southwestward then westward and extended at the same time in order to occupy the increasing surface within the successive escape wedges this is not the behaviour of simple lateral extrusion of the anatolian lithospheric block induced by forces applied at its boundaries by the adjacent plates but rather that of detached crustal blocks submitted to extension as a consequence of backward retreat of the hellenic slab and buoyancy forces arising from crustal thickness differences

post rift anomalous thermal flux in the songliao basin ne china as revealed from fission track thermochronology and tectonic analysis abstract the songliao basin in northeastern china contains a nearly complete cretaceous sedimentary record it offers an unparalleled opportunity for studying the thermal behavior of a rifting basin adjacent to a subduction zone during various stages of its evolution the post rift thermal history of the songliao basin is here documented by systematic apatite and zircon fission track analyses on newly exhumed sandstone samples from the upper cretaceous quantou and qingshankou formations the combination of thermochronology results and stratigraphic records indicates that there was an unambiguous post rift thermal overprinting event in the songliao basin during the deposition of the nenjiang formation at 85 80 ma this fossil thermal anomaly has not been previously recognized from organic maturity indicators and or subsidence modeling the zircon fission track results indicate an estimated maximum paleo temperature as high as 170 220 c near the daqing placanticline fission track analyses of sampled apatites further define a restricted thermal anomaly in the central part of the basin based on the context of local lithospheric structure and adjacent plate tectonic history we conclude that the late cretaceous westward subduction of the paleo pacific plate not only produced vertical motions and directly controlled the topography of the songliao lake but also dominated the mantle heat flow beneath east asia this finding has significant implications for the evolution of thermal flux in the basin

basin modelling how well have we done model developers have been highly successful in building usable useful and reliable one dimensional models and in convincing explorationists to use them development of convenient universal software played an instrumental role in the acceptance of 1 d modelling the remaining weaknesses in technology and training while serious can be resolved through a few years of intensive work in certain specific areas 2 d and 3 d fluid flow modelling in contrast finds itself today largely in the position occupied by 1 d modelling more than a decade ago the concept of fluid flow modelling has not yet been adequately sold to explorationists mainly because existing software is often inadequate to meet the real needs of exploration personnel development of appropriate software will probably have to precede widespread popularization of fluid flow modelling to improve existing software two major areas must be addressed 1 making models more comprehensive by including all relevant geologic phenomena and 2 making software easier to use

seismic signature of the collision between the east tibetan escape flow and the sichuan basin abstract gps displacement vectors show that the crust in east tibet is being squeezed in an easterly direction by the northward motion of the indian plate and the sichuan basin is resisting this stream and redirecting it mainly towards indochina the longmen shan containing the steepest rise to the high plateau anywhere in tibet results from the strong interaction between the east tibetan escape flow and the rigid yangtze block sichuan basin but the kinematics and dynamics of this interaction are still the subject of some debates we herein present results from a dense passive source seismic profile from the sichuan basin into eastern tibet in order to study the deep structure of this collision zone using p and s receiver function images we observe a sudden rise of the lithosphere asthenosphere boundary lab from 120 to 150 km beneath the sichuan basin and from 70 to 80 km beneath eastern tibet in contrast the depth of the crust mantle boundary moho increases from 36 to 40 km beneath the sichuan basin and from 55 to 60 km beneath eastern tibet the 410 km discontinuity is depressed below eastern tibet by about 30 km although the 660 remains at nearly the same depth throughout the lms from these observations we conclude that the mode of collision that occurs between tibet and the sichuan basin is very different to that found between india and tibet in southern tibet we observe in essence the subduction of the indian plate which penetrates northwards for several hundred kilometers under central tibet the very thin mantle part of the lithosphere beneath eastern tibet may indicate delamination or removal of the bottom of the lithosphere by hot asthenospheric escape flow this process leads to the exceptionally steep topography at the eastern tibetan margin as a result of gravitational buoyancy this view is supported by the very unusual depression of the 410 km discontinuity beneath eastern tibet which could be caused by the dynamics of the sub vertical downward asthenospheric flow

late miocene transcurrent tectonics in nw turkey evidence from palaeomagnetism and 40ar 39ar dating of alkaline volcanic rocks a number of intra continental alkaline volcanic sequences in nw turkey were emplaced along localized extensional gaps within dextral strike slip fault zones prior to the initiation of the north anatolian fault zone this study presents new palaeomagnetic and 40 ar 39 ar geochronological results from the lava flows of nw turkey as a contribution towards understanding the neogene quaternary tectonic evolution of the region and possible roles of block rotations in the kinematic history of the region 40 ar 39 ar analyses of basalt groundmass indicate that the major volume of alkaline lavas of nw turkey spans about 4 million years of episodic volcanic activity palaeomagnetic results reveal clockwise rotations as high as 73 in thrace and 33 anticlockwise rotations in the biga peninsula movement of some of the faults delimiting the areas of lava flows and the timing of volcanic eruptions are both older than the initiation age of the north anatolian fault zone implying that the region experienced transcurrent tectonics during late miocene to pliocene times and that some of the presently active faults in the region are reactivated pre existing structures

distinct variations of crustal shear wave velocity structure and radial anisotropy beneath the north china craton and tectonic implications article i nfo this study presents the crustal shear wave velocity structure and radial anisotropy along two linear seismic arrays across the north china craton ncc from ambient noise tomography about a half to one year long ambient noise data from 87 stations were used for obtaining the inter station surface wave empirical green s functions egfs from cross correlation rayleigh and love dispersion curves within the period band 5 30 s were measured from the egfs of the vertical and transverse components respectively these dispersion data were then used to determine the crustal shear wave velocity structure vsv and vsh and radial anisotropy 2 vsh vsv vsh vsv from point wise linear inversion with constraints from receiver function analysis our results reveal substantial structural variations among different parts of the ncc the bohai bay basin in the eastern ncc is underlain by a thin crust 30 km with relatively low velocities particularly vsv and large positive radial anisotropy in the middle to lower crust such a crustal structure is no longer of a cratonic type and may have resulted from the widespread tectonic extension and intensive magmatism in this region since late mesozoic beneath the ordos basin in the western ncc the crust is relatively thicker 40 km and well stratified and presents a large scale low velocity zone in the middle to lower crust and overall weak radial anisotropy except for a localized lower crust anomaly the overall structural features of this region resemble those of typical precambrian shields in agreement with the long term stability of the region the crustal structure under the trans north china orogen tnco central ncc is more complicated and characterized by smaller scale velocity variations strong positive radial anisotropy in the middle crust and rapid change to weak to negative anisotropy in the lower crust these features may reflect complex deformations and crust mantle interactions probably associated with tectonic extension and magmaticunderplating during the mesozoic to cenozoic evolution of the region our structural images in combination with previous seismic geological and geochemical observations suggest that the phanerozoic lithospheric reactivation and destruction processes may have affected the crust especially the middle and lower crust of the eastern ncc and the effect probably extend ed to the tnco but may have minor influence on the crust of the western part of the craton

tectonic evolution of the marmara sea and its surroundings abstract the basins in the marmara sea are the products of a superimposed evolutionary history defined by two different aged fault systems the early miocene early pliocene thrace eskisehir fault zone and its branches and the late pliocene recent north anatolian fault and its branches the thrace eskisehir fault and its westward branching secondary fault systems define the early neotectonic signature in the region the late neotectonic period started at the end of the early pliocene when the north anatolian fault divided the thrace eskisehir fault into four parts during the late neotectonic period the north anatolian fault extended westward as a number of splays by joining with the ganos bandirma behramkale and manyas edremit fault zones the branches of the north anatolian fault zone nafz caused the evolution of a number of basins which differ in character depending on the trend and past characteristics of the older branches that became connected since the northern branch of the north anatolian fault is connected to the n80 e trending ganos fault zone gfz in the west a single buried fault has developed in the marmara sea causing the well known troughs and ridges superimposed onto the negative flower structure formed by the gfz in the early neotectonic period the middle strand which extends from iznik lake to bandirma is oriented east west up to the n60 e trending bandirma behramkale fault zone then turns southward in the vicinity of bandirma forming a region dominated by compressional tectonics this bending caused n30 e trending tension in addition to the strike slip motion between the eastern part of gemlik bay and bandirma bay the southern branch of the nafz on the other hand produced three pull apart basins with different characteristics along the yenisehir bursa and manyas segments the southern branch of the nafz connected to the manyas edremit fault zone which is oriented n45 e to the south of manyas and the associated bending and rotation caused a n15 e trending extension in addition to the strike slip regime between manyas and uluabat the branches of north anatolian fault cut through the thrace eskisehir fault at three places the east marmara sea region in gemlik bay and to the east of bursa giving lateral offsets of 58 59 7 8 and 10 11 km respectively the cumulative motion is 75 78 km corresponding to the total lateral offset of the north anatolian fault in the region the correlation of these offsets with global positioning system slip vectors and with stratigraphic results implies that the north anatolian fault reached into the marmara sea region about 3 5 million yr ago tectonic processes forming the marmara sea and its environs were initiated by the thrace eskisehir fault and its splays have been most recently controlled by the north anatolian fault and its splays during the last 3 5 million yr

basement structures of east and south china seas and adjacent regions from gravity inversion abstract the satellite derived gravity gives us an opportunity to investigate the basement structures of the east and south china seas since the satellite gravimetry could provide large scale gravity data with high resolution of 1 arc min by 1 arc min we isolate the residual gravity anomaly corresponding to the basement by subtracting the gravity anomalies of sediments and moho undulations from satellite derived free air gravity anomalies two methods namely gravity inversion method and convolution method based on flexure isostasy model are used to calculate the moho undulations in order to guarantee the accuracy of the moho undulations since it occupies large percentages of the gravity anomalies we invert the isolated gravity anomaly for the basement depths of east and south china seas and adjacent areas with resolution of 1 arc min by 1 arc min the basement depths of east and south china seas range from 0 5 km to 12 km and the moho depths vary between 6 km and 32 km the basement topography reveals many tectonic depressions and two spreading axes concealed by the sediments which are unseen in the bathymetry the two spreading axes correspond to the spreading ridges derived from magnetic anomaly and the sw ne oriented spreading axis extends sw much farther than that identified from magnetic anomaly almost reaching to the nam con son basin we also find that the faults constrain the distributions of basement depressions since the faults usually lie along the places where large changes of basement depth take place reversely the basement map could be used to identify the unknown faults besides according to the four profiles in the east and south china seas the mirror image relation was found between the basement topography and the underlying moho undulations that when the basement depth increases or decreases the corresponding moho depth decreases or increases

the surface rupture and slip distribution of the 17 august 1999 izmit earthquake m 7 4 north anatolian fault the 17 august 1999 izmit earthquake occurred on the northern strand of the north anatolian fault zone the earthquake is associated with a 145 km long surface rupture that extends from southwest of duzce in the east to west of hersek delta in the west detailed mapping of the surface rupture shows that it consists of five segments separated by releasing step overs herein named the hersek karamursel golcuk izmit sapanca lake sapanca akyazi and karadere segments from west to east respectively the hersek segment which cuts the tip of a large delta plain in the western end of the rupture zone has an orientation of n80 the n70 80 e trending karamursel golcuk segment extends along the linear southern coasts of the izmit gulf between karamursel and golcuk and produced the 470 cm maximum displacement in golcuk the northwest southeast striking golcuk normal fault between the karamursel golcuk and izmit sapanca segments has 2 3 m maximum vertical displacement the maximum dextral offset along the izmit sapanca lake segment was measured to be about 3 5 m and its trend varies between n80 e and east west the sapanca akyazi segment trends n75 85 w and expresses a maximum displacement of 5 2 m the karadere segment trends n65 e and produced up to 1 5 m maximum displacement the karadere and sapanca akyazi segments form fan shape or splaying ruptures near their eastern ends where the displacement also diminished

morphology displacement and slip rates along the north anatolian fault turkey 1 geological and geomorphological offsets at different scales are used to constrain the localization of deformation total displacement and slip rates over various timescales along the central and eastern north anatolian fault naf in turkey the naf total displacement is reevaluated using large rivers valleys 80 15 km and structural markers pontide suture 85 25 km tosya vezirkopru basins 80 10 km these suggest a neogene slip rate of 6 5 mm yr over 13 myr the river network morphology shows offsets at a range of scales 20 m to 14 km across the main fault trace and is also used to estimate the degree to which deformation is localized at a smaller scale the morphology associated with small rivers is offset by 200 m along the naf the age of these features can be correlated with the holocene deglaciation and a slip rate of 18 3 5 mm yr is determined this is consistent with a rate of 18 5 mm yr deduced independently from the 14c dating of stream terrace offsets over the short term gps data gives a similar rate of 22 3 mm yr all our results tend to show that most of the deformation between the anatolian and eurasian lithospheric plates has been accommodated along or very close to the active trace of the naf the difference between the neogene and the holocene slip rate may be due to the recent establishment of the current plate geometry after the creation of the naf

sedimentary basin inversion caused by igneous underplating northwest european continental shelf a considerable body of evidence indicates that many of the extensional sedimentary basins in the vicinity of the british isles underwent permanent exhumation during the tertiary the most dramatic indicator of this process is the present day absence of as much as 4 km of anticipated postrift thermal subsidence in basins just north and west of scotland any explanation of this observation must take into account the fact that the entire region has very small long wavelength free air gravity anomalies this important constraint implies either that the crust has been thickened or that low density material has been added to or formed from the lithosphere and rules out models that invoke flexural effects arising from the opening of the north atlantic tertiary epeirogeny is often attributed to compression that is assumed to be related in a general sense to alpine mountain building however to remove 3 km of sedi mentary rock from a basin 100 km wide requires 15 km of shortening minor tertiary compression is observed all over the continental shelf but nowhere is it sufficient to account for the required amount of uplift and erosion in addition exhumation dramatically increases from south to north whereas the observed compression decreases markedly in the same direction at the beginning of the tertiary rifting associated with the initiation of the iceland plume generated substantial volumes of melt inversion of rare earth element concentrations of mgorich igneous rocks suggests that a minimum of 5 km of melt was produced beneath at least part of the continental shelf we infer that much of this melt remains trapped within the lithosphere presumably close to the moho which acted as a density filter such underplating will generate rapid uplift

composition of the crust beneath southeastern china derived from an integrated geophysical data set 1 the nonuniqueness in determining the composition of the crust can be reduced by comparing the data for p wave velocity vp s wave velocity vs vp vs ratio mass density and lame impedances to data determined from laboratory measurements of these physical variables on a variety of crustal rock samples the composition of the crust along the tunxi wenzhou transect southeastern china is presented as a model based on a complete set of geophysical data involving seismic p wave and s wave velocity density gravity heat flow and temperature surveys which allow us to place tighter constraints on possible crustal models the yangtze and the cathaysia blocks have a crustal structure characterized by remarkable differences between the upper middle and lower crust integrated geophysics data are here interpreted to indicate 1 an average composition of granite gneiss for the upper crust with presence of mica quartz schist felsic granulite paragranulite and granite granodiorite beneath the yangtze block and basalt down to the upper part of the middle crust just over the jiangshan shaoxing fault followed laterally by granite gneiss beneath the songyang qintiang and wenping depressions 2 granite granodiorite and biotite gneiss for the upper half of the middle crust with presence of mica quartz schist beneath the cathaysia block 3 gabbro and in less proportion basalt for the lower part of the middle crust and 4 amphibolite for the lower crust with presence of mafic garnet granulite just over the jiangshan shaoxing fault and beneath the wenping depression

fission track evidence for late oligocene and mid miocene activity along the north anatolian fault in south western thrace apatite fission track ft analyses of sandstone samples collected across the trace of the ganos segment of the north anatolian fault naf in south western thrace turkey indicate that a significant structural discontinuity was in existence at least by the latest oligocene such discontinuity had a complex kinematic history as exhumation south of it occurred during the latest oligocene and north of it during the mid miocene our data imply that early pliocene westward propagation of the naf in the marmara region followed a pre existing structural discontinuity such discontinuity could be related to the development of the intra pontide suture marking the terminal closure of the intra pontide ocean during the oligocene

mirror symmetry of the crust in the oil gas region of shengli china abstract the concept of mirror image symmetry describes the correlation between the bottom of a sedimentary basin and the top of the underlying mantle the degree of mirror symmetry is analyzed here using thickness data from mesozoic cenozoic sedimentary basins and the moho depth with the purpose of investigating the implications for tectonics and exploratory practices in oil gas bearing basins our attention is focused on different tectonic elements of a multi scale tectonic partition in the oil gas region of shengli southeast of bohai bay china by applying standard least squares analysis methods to both datasets we obtained the average thickness h of the consolidated crust and the mirror symmetry factor a for every tectonic unit thereby allowing us to explore the correlation between the bottom depth of a sedimentary basin and the top of the underlying mantle a detailed analysis of data uncertainties and their potential effects led to small fluctuations of h and a within a narrow band around the mean values of 33 26 km and 1 43 respectively thus the results can be considered valid if they are constrained by these error bounds the issues of crust mantle interaction and the deviation of the crust from isostatic equilibrium are also addressed for their tectonic implications other structural parameters related to the deep rooted crust beneath the tectonic elements that make up the study region such as the ratio r of the thickness of the consolidated crust to the absolute value of the symmetry factor the ratio k of the maximum sediment thickness to the maximum uplift of the mantle and the product kh are also evaluated for their implications in geophysical prospecting the symmetry signature of the crust is compared to the symmetry of other sedimentary basins in china and in the world suggesting symmetry as a feasible prognostic tool in exploration for oil gas reservoirs the key result is that those locations where oil gas reservoirs have been found to date are basins in which the crust mantle interaction is active and the crust is isostatically compensated both of those parameters can be quantitatively constrained conversely oil and gas reserves are poor or nonexistent in regions where the crust mantle interaction is inactive and the crust is far from isostatic equilibrium however an intermediate case between these two extreme scenarios wherein the crust mantle interaction is rather moderate but the crust is in a state close to isostasy cannot be entirely ruled out

an overview of the earth crust under china abstract we assess the results of a number of deep seismic soundings performed in china over the last few decades and study the variations in crustal structure in 18 tectonic units comprised of three platforms and 15 fold systems thickness data on 344 mesozoic cenozoic sedimentary basins as well as data on moho depth are collected in order to discuss the relationship between the thickness of the basins and the average thickness of the consolidated crust in each tectonic unit the degree of mirror image symmetry between mesozoic cenozoic sedimentary basins and the uplifting topmost parts of the mantle is herein analyzed using deep geophysical data on sedimentary basins by applying standard methods of least squares analysis to both datasets we have obtained both the average thickness of the consolidated crust and the mirror image symmetry factor for every platform and tectonic fold system thereby allowing us to explore the correlation between the depths of the bottom of the sedimentary basins and the top of the uplifting mantle the thickness of the consolidated crust in china is found to be between 20 and 63 km following a pattern of gradual thickening from east to west expressed in terms of spatial seismicity and the concentration of seismic energy and according to the sharing out of earthquake hypocenters in the top 80 km of the earth the rheology of the area does not appear to suit the widely accepted jelly sandwich model for the continents which does not seem to be entirely valid in china the findings on the mirror image symmetry factor show that this parameter varies mainly in the range 0 5 to 1 8 compared with each other tectonic unit most of the tectonic systems in china appear to be isostatically compensated tibet is an exception in that the symmetry factor is positive for the gangdise nyainqentanglha 1 0 and himalayan 0 1 fold systems implying that these tectonic zones are far from being in the isostatic equilibrium of the other regions we have also analyzed the zoning characteristics through the logarithmic relationship ln r ln h a using the average thickness of the consolidated crust and the absolute value of the symmetry factor the key finding is that regardless of geographical location all the values of r h a for those sedimentary basins in which oil gas reservoirs have to date been found fall into the narrow range of values between 19 38 and 37 40 there is some appeal in a possible relationship involving the ratio of crustal thickness to symmetry factor more so when the results obtained appear to suggest a prognostic tool for exploratory practice in relation to oil gas reservoirs

slip partitioning in the sea of marmara pull apart determined from gps velocity vectors summary dislocation modelling is used to examine the gps velocity vectors for the marmara sea region first the vectors due to the known anatolia eurasia rotation are reproduced by introducing structures that approximate the large scale tectonics observed features of the smaller scale fault system in the marmara region are then progressively included with slip amplitudes and directions adjusted to fit an 80 vector subset of the gps data the motion in the marmara sea region is partitioned with the faults that bound the north of the basin carrying more strike slip motion than predicted from the anatolia eurasia plate motion and faults to the south having a greater perpendicular component taken together however there is no net opening across the marmara sea perpendicular to the overall trend of the boundary and thus deformation in the marmara region results only from the pull apart geometry of the north anatolian fault no extension related to the aegean system is needed to explain the observations the gps results are consistent with motion over the last 5 myr that has been determined from geological reconstructions

palaeostress analysis of tertiary post collisional structures in the western pontides northern turkey fingerprints of the opening of the western black sea basin and collision of pontides and sakarya continent along the intra pontide suture can be traced in the area between cide kastamonu and kurucasile bartin in northern turkey along the southern coast of the black sea the western black sea basin is an oceanic basin opened as a back arc basin of the northward subducting intra pontide ocean basement units related to this opening are represented by lower cretaceous and older units the first arc magmatism related to this subduction began during turonian times coeval with this magmatism back arc extension affected the region and caused development of horst graben topography this extensional period resulted in the break up of continental crust and the oceanic spreading in the western black sea basin during late santonian times during the late campanian early maastrichtian period the sakarya continent and pontides collided and arc magmatism on the pontides ended after this collision the western pontides thickened imbricated and developed a mainly n vergent foreland fold and thrust belt character since late eocene oligocene times the palaeostress directions calculated from thrust faults of this foreland fold and thrust belt are 4 6 156 6 for 1 6 4 66 1 for 2 and 83 2 261 9 for 3 the nature of the imbrica tion indicates that it was a northward prograding foreland system connected to a floor thrust detach ment fault at the bottom field observations on curved slickenfibres support the theory that the thrust faults of this imbricated structure have transformed to oblique thrusts and strike slip faults over time

carpathian foreland fold and thrust belt and its relation to pannonian and other basins the foreland fold and thrust belt of the carpathians can be traced from austria through the western and eastern carpathians to the south carpathian bend in romania where most of its structural units plunge beneath younger pliocene pleistocene cover folds in the youngest rocks at the south carpathian bend continue westward until all surface expression disappears before reaching the danube river the fold and thrust belt is flanked by elements of the european russian and moesian cratonal areas which are overlain by a variable width and thickness of foredeep deposits that are partly involved within the external fold and thrust belt internal to the fold and thrust belt are older parts of the carpathian orogene formed mainly on continental crust these older structures have significant differences in evolution between the western and eastern carpathians the foreland fold and thrust belt consists predominantly of flysch in its inner parts and molasse in its outer parts these sedimentary rocks are cut into a series of thrust sheets that have moved relatively toward the craton oldest flysch units are late jurassic and the youngest units are miocene some of the flysch units of the inner part of the belt may have been underlain by oceanic crust whereas the younger more external molasse units were underlain by continental crust timing of thrusting is only well constrained locally but suggests that deformation in the western carpathians developed during oligocene to miocene time in the eastern carpathians structural activity continued into the pliocene and deep earthquake activity at vrancea suggests subduction deformation is sti l locally active a volcanic arc of miocene to holocene age lies internal to the fold and thrust belt magmatic activity appears to have migrated externally and eastward in time contemporaneous with thrusting was the development of neogene basins in the intra carpathian region these basins exhibit a two phase subsidence history except for the pannonian and transylvanian basins fast initial subsidence followed by a period of slower linear subsidence the pannonian basin shows only a reasonably fast linear subsidence structural and thermal models indicate the basins were formed by about 100 stretching the convex east loop of the carpathian foreland fold and thrust belt is a result of the collision of continental fragments against a recess in the combined european moesian plate in this region subduction or downbending of the subducted slab results in an extensional stress field suggesting that thrusting and apparent compression along the mountain belt are only thin skinned superficial effects due to the inability to subduct light upper crustal material and detachment of the crust from the underlying lithosphere the dominant forces seem to be those acting on the downgoing slab which produce shortening along the plate boundary and plate geometry that inhibits rigid plate convergence

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

the north china basin an example of a cenozoic rifted intraplate basin the north china basin was a stable continental region that has undergone several distinct phases of rifting and subsidence during the mesozoic and cenozoic eras the last major phase featuring block faulting rapid subsidence and widespread calc alkaline basaltic volcanism began during early tertiary time this intraplate rifting appears to be the result of an approximately 30 extension and thinning of the lithosphere beneath the northeastern china by the late tertiary period active rifting had slowed and postrift thermal subsidence had begun this regional extension and subsidence resulted in the present day north china basin a large saucer shaped oil producing basin with thinner crust and lower upper mantle p and s wave velocities than the surrounding regions during the quaternary period however the subsidence rate increased in the north china basin the frequent occurrence of destructive earthquakes and observations of relatively high heat flow suggest that the quaternary tectonic activity differs from the late tertiary simple thermal subsidence pattern and may indicate a new phase of rifting

estimation of the pre north anatolian fault zone pseudo paleo topography a key to determining the cumulative offset of major post collisional strike slip faults abstract geometric analysis of the morphological elements in a fault controlled environment is a widely used application to investigate active tectonics in this study we analyze recent topographical data to reconstruct an inherited landform assumed to have been formed and then continuously deformed by multiphase tectonics retracing the steps of this complex evolution would allow for the parameters of the faulting kinematics to be deduced here we present a detailed description of the methodology by both graphical and analytical approaches and provide quantitative data for constraining fault behavior this case study focuses on the high topography of northern anatolia which is believed to have formed during the early miocene by significant uplift subsequent to the major phase of plate collision in this area this paleo topography was later cut and dissected after the initiation of a plate bounding continental strike slip fault zone called the north anatolian fault zone nafz results of our analysis reveal that the southern part of the studied portion of the nafz tilted westward with a maximum uplift of 290 m tilting corrected offsets measured along the nafz show that the average dextral displacement is 72 km however measured offsets increase up to 100 km towards the westernmost portion of the fault zone western part of the almacik block we discuss the possibility of analyzing large scale morphotectonic structures to shed light on some debated points related to the nafz evolution the methods described here can be applied to other post collisional strike slip faults worldwide and also to smaller scale morphological structures

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

the cenozoic rift system of the north china plain and the deep internal process abstract the cenozoic north china plain rift system generated on the site of a mesozoic rift system is the largest rifted basin in east china it trends nne with a total length of about 1000 km maximum width up to 400 km in its middle part and a width of 50 100 km at its south and north the largest thickness of the cenozoic deposits reaches 12 000 m and the accumulated thickness of the cenozoic basalts about 2000 m this rift system is a region of strong seismicity it has quite considerable differential crust movement at the present day the geophysical data indicate that the thickness of the crust and lithosphere beneath the rift system is approximately 4 8 km and 40 km thinner than that of the surrounding mountains this rift system has rather high heat flow values and residual gravity anomalies so far no low velocity anomaly of pn has been found in this region we infer that the formation of this rift system is caused by upwelling of the asthenosphere which is probably related to the convective roll induced by subduction of the pacific plate underneath the asiatic continent and the disturbance of the upper mantle in this region during the mesozoic

crustal structure and extensional deformation of thinned lithosphere in northern china abstract we herein present an interpretation of a 320 km long wide angle seismic profile between anxin and kuancheng which was obtained in 2002 the profile runs from the north china plain ncp where the lithosphere is just 70 km thick to the yanshan mountain folded belt ymfb where the lithosphere is180 km thick our model shows a crustal thickness that varies from 31 km under the ncp to 36 km under the ymfb the observed thinning of the crust in the ncp is about 14 which compares with an average extension of 24 41 at basin scale and 25 at lithosphere scale this finding suggests that the extensional deformation of the lithosphere in the north china block depends on depth the thin high velocity crust mantle transition zone has most likely originated after a delamination of the bottom of the crust and a concomitant intrusion of materials from the mantle the lower velocity of the lower crust may be attributed to the destruction of the lithosphere which permitted the lateral flow of melting materials above the moho from the ncp to the ymfb the differences found between the crust and the lithospheric mantle help to dispel any of the remaining uncertainty in the extensional factors and they may be attributed to detachment of middle crust and an intrusion of magma that originated in either lithosphere or asthenosphere we infer that the detachment of the middle crust lower crustal flow and magma intrusion probably lead to the underestimation of the crustal scale extensional factor and may represent the crustal response to the thinning of the lithosphere

mechanisms of petroleum accumulation in the bozhong sub basin bohai bay basin china part 1 origin and occurrence of crude oils the origin of the fourteen major oil fields in the bozhong sub basin bohai bay basin was studied based on the results of rock eval pyrolysis on more than 700 samples and biomarker analysis on 61 source rock samples and 87 oil samples the three possible source rock intervals have different biomarker assemblages and were deposited in different environments the third member of the oligocene dongying formation e3d3 32 8 30 3 ma in age is characterized mainly by high c19 c23 tricyclic terpane 0 75 high c24 tetracyclic terpane c26 tricyclic terpane 2 5 low gammacerane c30 hopane 0 15 and low 4 methyl steranes c29 steranes 0 15 ratios and was deposited in sub oxic to anoxic environments with significant terrigenous organic matter input the first e2s1 35 8 32 8 ma and third e2s3 43 0 38 0 ma members of the eocene shahejie formation have low c19 c23 tricyclic terpane and low c24 tetracyclic terpane c26 tricyclic terpane ratios and were deposited in anoxic environments with minor terrestrial organic matter input but have different abundances of 4 methyl steranes and gammacerane the hydrocarbon generating potential and biomarker associations of these three source rock intervals were controlled by tectonic evolution of the sub basin and climate changes three oil families derived from e2s3 e2s1 and e3d respectively and three types of mixed oils have been identified all large oil fields in the bozhong sub basin display considerable heterogeneities in biomarker compositions and originated from more than one source rock interval which suggests that mixing of oils derived from multiple source rock intervals or multiple generative kitchens and or focusing of oils originated from a large area of a generative kitchen is essential for the formation of large oil fields in the bozhong sub basin e2s3 and e2s1 derived oils experienced relatively long distance lateral migration and accumulated in traps away from the generative kitchen e3d3 derived oils had migrated short distances and accumulated in traps closer to the generative kitchen such a petroleum distribution pattern has important implications for future exploration there is considerable exploration potential for dongying derived oils in the bozhong sub basin and traps close to or within the generative kitchens have better chance to contain oils generated from the dongying formation

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

results of lithospheric studies from long range profiles in siberia several long range seismic profiles obtained during the last ten years in siberia show the complicated lithospheric structure of the siberian platforms the three component observations conducted at distances up to 3000 km made it possible to obtain information on p and s velocities in the crust on p velocity and q factor for the upper mantle and on the seismic boundaries responsible for reflected refracted and converted waves down to a depth of 400 700 km the crustal models are typical of old platforms of eurasia the average thickness of 40 km three layers with p velocities 6 2 6 5 7 0 km s and thicknesses of 10 15 km are distinguished the depth to the m discontinuity varies from 45 50 km beneath the old tunguss depression to 35 40 km beneath the younger vilyui basin the most complicated moho structure is observed in the boundary between the west siberian and the siberian platforms a strong inhomogeneity of p velocity models was revealed for the upper mantle the horizontal inhomogeneities are more larger in the uppermost mantle to depths of 80 100 km where p velocities vary from 8 0 8 2 km s beneath the young west siberian plate to 8 4 8 6 km s beneath some blocks of the siberian craton the fine vertical inhomogeneity was studied with reflections correlated after computer processing of seismograms they outlined several low velocity layers 20 50 km thick the layers were characterized by low q as well intensive waves were recorded from the transition zone between the upper and lower mantle the top of the zone is nearly horizontal in the area its depth is 400 25 km the bottom of the zone lies at about 700 km

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

mesozoic basins in eastern china and their bearing on the deconstruction of the north china craton abstract mesozoic basins occur widely in the eastern block and the neighboring area of the north china craton including the bohai bay the jiaolai the hefei and the north yellow sea in the north and the jianghan and the subei south yellow sea basins to the south their spatial temporal framework is the consequence of the indosinian and yanshanian tectonic regimes in eastern china and record the events related to mesozoic deconstruction of the north china craton our results demonstrate that the mesozoic tectonic evolution of the eastern north china craton was related to both sub crustal delamination and intra crustal extrusion or escape tectonics thus we propose that the mechanism of uplift of the yanshanian north china plateau and related lithosphere thinning in the eastern north china craton were related to sub crustal delamination at depth however the different distribution patterns of the basins on both sides of the tan lu fault system as well as the co existence of both compressional and extensional basins in the mesozoic indicate that these were controlled by escape tectonics in different tectonic parts of the crust

increase in melt fraction along a south north traverse below the tibetan plateau evidence from seismology abstract a mid crustal low velocity zone and crustal melt fraction contrast the lhasa block in the maxiang yangbajain zone with the tethyan himalayas in the south evidence from wide angle reflections is extended by vertical reflection and differential s to p wave teleseismic delays the temperature and rheology implied allow phase transitions which may change crustal buoyancy and elevation le pichon et al 1997 and may allow lateral mass flow in the uppermost mantle particular path geometries to a tight temporary teleseismic array allow detection of a decrease in velocity northward through the lhasa block a larger relative variation in late teleseismic s with respect to p indicates an increase in poisson s ratio hence of partial melt fraction this may be seen as evidence of a higher position of the mantle asthenosphere level tibet hence appears to be underlain by variation in the structure within the crust across the indus tsangpo suture and in the structure within the mantle further northward of the middle lhasa block these variations are most readily attributable to spatial variation in partial melt fraction and hence temperature which also induces phase transformations mode and amount of deformation and control of buoyancy on elevation may vary accordingly the dynamics of the system is evidenced by seismic anisotropy which we relate to ductile flow

the cenozoic tectonic evolution of the great north china two types of rifting and crustal necking in the great north china and their tectonic implications abstract the great north china underwent widespread continental rifting during cenozoic time that caused extension and necking of the crust in this area and formed four major rift systems in this paper we provide geological and geophysical evidence that rifting and extension in the western part of the great north china differs from that in its eastern part in age and nature the space time relationships show that the origins of the western rift group of the great north china are probably related to the tibet plateau tectonics whereas those of the eastern rift group are related to the subduction events in the western margin of the pacific plate furthermore the quaternary tectonic regime in the eastern part of the great north china differs from the neogene tectonic pattern and shows relations with western rifts we speculate that during the quaternary the processes that caused rifting in the west have spread further east and now affect the eastern part of the great north china

crustal structure across the three gorges area of the yangtze platform central china from seismic refraction wide angle reflection data abstract we present active source seismic data recorded along a 300 km long profile across the three gorges area of the western yangtze platform central china from west to east the profile crosses the zigui basin huangling dome and jianghan basin the derived crustal p wave velocity structure changes significantly across the tongchenghe fault that lies at the transition from the huangling dome to the jianghan basin west of the tongchenghe fault beneath the zigui basin and the huangling dome we observe a 42 km thick crust of relatively low average velocity 6 3 6 4 km s in contrast east of the tongchenghe fault beneath the jianghan basin the crust is only 30 km thick and has a high average velocity 6 6 6 7 km s a west east variation in crustal composition along the tongchenghe fault is also inferred west of the fault p wave velocities suggest a felsic composition with an intermediate layer at the base of the crust whilst east of the fault felsic intermediate and mafic crustal layers are apparent our results suggest that the crust beneath the jianghan basin has been thinned by rifting accompanied by intrusion of the lower crust by mafic dikes and sills the west to east division of the crust in the three gorges area coincides with first order geophysical contrasts in gravity topography crustal and lithospheric thickness

a comparison of foreland and rift margin sedimentary basins foreland and rift margin basins are compared on the basis of 1 their tectonic setting 2 reasons for subsidence and 3 their large scale geophysical and geological characteristics the thermal and mechanical properties of the underlying lithosphere are shown to be fundamental to the form of tectonic subsidence the lithosphere beneath foreland basins is flexurally downwarped by the loading of the adjacent fold thrust belt whereas tectonic subsidence at rifted margins is caused by mass replacement at depth during lithospheric extension on rifting and subsequent thermal contraction as the lithosphere cools the effects of rheology thermal maturity and lateral changes in properties of the lithosphere are outlined for foreland basins as is the topographic effect of possible phase changes beneath the fold thrust belt the thermal and rheological consequences of lithospheric extension at rift margins makes flexural subsidence relatively less important than in foreland basins flexure may however be partly responsible for uplift landward of the hinge line that is associated with rifting other mechanisms that could cause such uplift include depth dependent extension and thermal expansion due to the lateral diffusion of heat the models describing the evolution of these basins are shown to predict characteristics that are in accord with observations the superposition of foreland and rift margin basins as a result of ocean closure can lead to an overall basin stratigraphy that is complex such phases of basin subsidence must be separated according to the tectonic environment in which they formed in any analysis of the cause and consequences of basin evolution

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

early miocene adakite like volcanism in the balkuyumcu region central anatolia turkey petrology and geochemistry the balkuyumcu region located in the southwestern part of ankara in the izmir ankara suture zone central anatolia turkey consists of basic andesitic andesitic dacitic and rhyolitic rocks extruded during the early miocene 20 22 ma as a result of post collisional volcanism balkuyumcu volcanic rocks can be divided into two groups on the basis of their mineralogy and composition the basic andesitic ba and andesitic dacitic and rhyolitic adr groups the adr and ba group of rocks have adakite like and calc alkaline characteristics respectively the adr group has higher sio2 content sr y and la yb ratios and low mgo mg y and yb contents than the ba group both groups have nearly the same sr nd isotopic compositions and display similar normalized multi element patterns with enrichments in lile and lree depletions in nb ti zr p and a lack of eu anomalies major trace element and sr nd isotopic data indicate that both groups of rocks were derived from the same source but affected by different magmatic processes during ascent the adakite like rocks may have been produced by partial melting of thickened lower continental crust fractional crystallization also played a major role in their formation however the ba group rocks were derived from partial melting of lower continental crust that was probably delaminated these rocks appear to have had limited interaction with mantle peridodite during ascent to the surface

cenozoic faulting of the bohai bay basin and its bearing on the destruction of the eastern north china craton abstract the cenozoic bohai bay basin is located at the center of the eastern block of the north china craton the structural architecture of this basin provides important clues on the deep seated lithosphere thinning of the north china craton the cenozoic regional stress field is characterized by nw oriented extension however the various cenozoic structural patterns of normal faulting and related transverse folding in the bohai bay basin are controlled not only by cenozoic stress field but also by strain field and mesozoic basement fault assemblages in this area regionally the cenozoic tectonic features and the dynamic evolution of the eastern north china craton are dominated by two lithosphere penetrating fault systems including the sinistral tan lu fault system and the dextral lan liao fault system to the west of the lan liao fault system cenozoic extensional tectonics includes nne trending listric normal faults that controlled half grabens however between these two fault systems are wnw trending half grabens which show basement involved faulting in the north and overlapping relations between sedimentary cover and basement in the south to the east of the tan lu fault the north yellow sea basin is a wnw trending fault depression with faulting in the south and overlapping relations in the north these structural features are inherited from the mesozoic tectonic framework of this area whose tectonic characteristics were completely controlled by two opposite strike slipping faults the trans extensional or oblique rifting in the paleogene followed by extensional faulting and subsequent subsidence furthermore the culmination of the decratonization of the north china craton was also related to an eastward jump of cenozoic subduction of the pacific plate and the far field effect of eastward extrusion of cenozoic subduction of the indian plate and was not essentially restricted to the early mesozoic processes therefore the cenozoic especially 25 ma marks the time of cessation of the processes that led to lithosphere thinning and destruction of the eastern block of the north china craton

gravity anomalies flexure of the indian plate and the structure support and evolution of the himalaya and ganga basin bouguer gravity anomalies along four profiles across the western himalaya and ganga basin show large deviations from local isostatic equilibrium a deficit of mass characterizes the ganga basin and an excess underlies the lesser himalaya both can be understood if the indian plate is flexed down by the distributed load of part of the mountains the cross sectional shape of the ganga basin seems to be controlled by the deflection of the indian plate which we compute assuming the indian plate to overlie an inviscid fluid from the shapes of both bouguer anomaly profiles and the basement topography we place bounds on the flexural rigidity of such a plate if the ganga basin is a steady state feature then the age of the basal sediments in a given locality should be proportional to the distance of that locality from the southern edge of the basin if the rate of convergence of india and the himalaya were constant that rate should equal the distance divided by the corresponding age we find a rate of 10 to 15 mm a for the last 15 to 20 ma which is consistent with a large part of the 50 mm a rate of convergence between india and eurasia being absorbed by the eastward extrusion of parts of tibet profiles of bouguer gravity anomalies show only a small peak or plateau over the southern edge of the lesser himalaya implying that the boundary between the light sediments of the ganga basin and the heavier crustal rocks of the lesser himalaya is not sharp and that there exists some light material beneath the range we infer that some sediment deposited in the ganga basin has been underthrust beneath the lesser himalaya but the quantity is small most of this sediment probably is scraped off the indian plate to make the foothills of the range we find that the load of the high himalaya is too large to be supported solely by elastic stress in the indian plate if the flexural rigidity of the plate is constant and if no other external forces act on the plate the observed gradient in bouguer gravity anomalies increases from an average of about 1 mgal km over the ganga basin and lesser himalaya to about 2 mgal km over the high himalaya this increase in the gravity gradient implies that the moho dips more steeply 10 15 beneath the high himalaya than beneath the lesser himalaya 2 3 we interpret this steepening of the moho to be due to a weakening of the plate which allows it to bend more sharply beneath the high himalaya than farther south with the inclusion of a weak segment of indian plate beneath the high himalaya calculated anomalies show a somewhat increased gradient beneath the high himalaya but when the weight of the entire himalaya is used as a load on the plate calculated anomalies are more negative than observed therefore an external force system is needed to support much of the weight of the high himalaya as well as to bend the plate sufficiently beneath the high himalaya the magnitudes of the bending moment and the force per unit length that must be applied to the end of the plate are compatible with their sources being gravity acting on a part of india s mantle lithosphere stripped of its crust and underthrust beneath southern tibet

uplift and erosion of the san bernardino mountains associated with transpression along the san andreas fault california as constrained by radiogenic helium thermochronometry apatite helium thermochronometry provides new constraints on the tectonic history of a recently uplifted crystalline mass adjacent to the san andreas fault by documenting aspects of the low temperature 40 100 c thermal history of the tectonic blocks of the san bernardino mountains in southern california we have placed new constraints on the magnitude and timing of uplift old helium ages 64 21 ma from the large big bear plateau predate the recent uplift of the range and show that only several kilometers of exhumation has taken place since the late cretaceous period these ages imply that the surface of the plateau may have been exposed in the late miocene and was uplifted only 1 km above the mojave desert in the last few myr by thrusting on the north and south a similar range in helium ages 56 14 ma from the higher san gorgonio block to the south suggests that its crest was once contiguous with that of the big bear block and that its greater elevation represents a localized uplift that the big bear plateau did not experience the structure of the san gorgonio block appears to be a gentle antiform based on the geometry of helium isochrons and geologic constraints young ages 0 7 1 6 ma from crustal slices within the san andreas fault zone indicate uplift of a greater magnitude than blocks to the north these smaller blocks probably experienced 3 4 km of uplift at rates 1 5 mm yr in the past few myr and would stand 2 5 km higher than the big bear plateau if erosion had not occurred the greater uplift of tectonic blocks adjacent to and within the san andreas fault zone is more likely the result of oblique displacement along high angle faults than motion along the thrust fault that bounds the north side of the range we speculate that this uplift is the result of convergence and slip partitioning associated with local geometric complexities along this strike slip system transpression thus appears to have been accommodated by both vertical displacement within the san andreas fault zone and thrusting on adjacent structures

active tectonics of the alpine himalayan belt between western turkey and pakistan summary over 80 new fault plane solutions combined with satellite imagery as well as both modern and historical observations of earthquake faulting are used to investigate the active tectonics of the middle east between western turkey and pakistan the deformation of the western part of this region is dominated by the movement of continental material laterally away from the lake van region in eastern turkey this movement helps to avoid crustal thickening in the van region and allows some of the shortening between arabia and eurasia to be taken up by the thrusting of continental material over oceanic type basement in the southern caspian mediterranean makran and black sea thus central turkey bounded by the north and east anatolian strike slip faults is moving west from the van region and overrides the eastern mediterranean at two intermediate depth seismic zones one extending between antalya bay and southern cyprus and the other further west in the hellenic trench the motion of northern iran eastwards from the van region is achieved mainly by a conjugate system of strike slip faults and leads to the low angle thrusting of iran over the southern caspian sea the seismicity of the caucasus shows predominantly shortening perpendicular to the regional strike but there is also some minor elongation along the strike of the belt as the causcasus overrides the caspian and black seas the deformation of the eastern part of this region is dominated by the shortening of iran against the stable borders of turkmenistan and afghanistan the north east direction of compression seen in zagros is also seen in north east iran and the kopet dag where the shortening is taken up by a combination of strike slip and thrust faulting large structural as well as palaeomagnetic rotations are likely to have occurred in ne iran as a result of this style of deformation north south strike slip faults in southern iran allow some movement of material away from the collision zone in ne iran towards the makran subduction zone where genuinely intermediate depth seismicity is seen within this broad deforming belt large areas such as central turkey nw iran azerbaijan central iran and the southern caspian appear to be almost aseismic and therefore to behave as relatively rigid blocks surrounded by active belts 200 300 km wide the motion of these blocks can usefully be described by poles of rotation the poles presented in this paper predict motions consistent with those observed and also predict the opening of the gulf of iskenderun ne of cyprus the change within the zagros mountains from strike slip faulting in the nw to intense thrusting in the se and the relatively feeble seismicity in se iran baluchistan this description also explains why the north south structures along the iran afghanistan border do not cut the east west ranges of the makran within the active belts surrounding the relatively aseismic blocks a continuum approach is needed for a description of the deformation even though motions at the surface may be concentrated on faults the evolution of fault systems within the active zones is controlled by geometric constraints such as the requirement that simultaneously active faults do not in general intersect many of the active processes discussed in this paper particularly large scale rotations and lateral movement along the regional strike are likely to have caused substantial complexities in older mountain belts and should be accounted for in any reconstructions of them

crustal thinning and nature of extension in the northern north sea from deep seismic reflection profiling a regional network of deep seismic reflection profiles recorded in the northern north sea has been used to map mesozoic and cenozoic basin thickness and crustal thickness in the viking graben and adjacent platform areas depth to the reflection moho varies from about 20 km in parts of the viking graben to about 32 km beneath the shetlands and the norwegian margin the shallowing of the reflection moho beneath the viking graben implies crustal stretching factors for mesozoic extension greater than 2 in the center of the north sea basin the axis of crustal thinning is located directly beneath the viking graben the axis of the sedimentary basin steeply dipping basin bounding faults are imaged in the upper crust and several dipping reflectors are observed in the upper mantle but no continuous reflective feature extending from the sedimentary basin to beneath the moho is observed on any of the deep profiles thus these data do not support the existence of lithosphere penetrating low angle detachments zones of simple shear as the cause of extension in the northern north sea some of the mantle reflectors dip to the west and some to the east suggesting that simple shear if it occurs in the upper mantle is not of uniform sense rather these data suggest a complex depth dependent pattern of brittle extensional deformation in the upper crust pervasive ductile extension bulk pure shear in the lower crust which is decoupled from deformation in the mantle and extension accommodated by discrete dipping shear zones in the lithospheric mantle

polyphased block tectonics along the north anatolian fault in the tosya basin area turkey abstract the tosya basin is located in the bending segment of the north anatolian fault naf in turkey we have obtained original observations on the neotectonics from sar ers images digital elevation model dem and field structural analysis regional neogene deformation is characterised by the occurrence of several basins that are superimposed in time and space they result from differently oriented movements since 12 ma including southwestward motion along a fault subparallel to the naf we propose a model of polyphased tectonics related to the displacement of several individualised blocks in the first stage tortonian the north tosya block has moved toward the n250 azimuth parallel to the dextral n70 striking segment of the naf as a consequence a triple junction related compatibility basin was opened at the intersection with a n60 to n30 striking fault this pattern is similar to the karliova corner where the naf and the east anatolian fault meet in the second stage early pliocene middle pleistocene a segment of the former n70 naf was abandoned and the naf propagated eastward to form a n90 striking segment n90 naf cutting the former tosya block and basin into two parts the north tosya block has moved again and this new geometry has permitted a south tosya block to move parallel to the naf but with a higher rate which has induced compression in the tosya basin in the third stage holocene the south tosya block moved toward n240 obliquely to any of the naf segments this has resulted in the formation of two holocene pull apart type basins along the previous n60 to n30 striking fault while extensional faults were formed in the south tosya block estimated dextral displacement along the naf is 5 9 to 8 5 km at this stage this model of blocks moving in different directions including holocene local movements toward n240 means that the naf can be considered not to be a simple transform fault our model implies that the n90 naf was non existent before the early pliocene

hydrocarbon habitat of the offshore bohai basin china the bohai basin is a major continental petroliferous basin located in eastern china of which the offshore part of the basin contains more than one third of the total petroleum resources in the basin although the basin has been explored for nearly 40 years the offshore part of the basin is just reaching a moderately mature stage of exploration and its petroleum geological features are gradually becoming known the subduction of the pacific plate to the eurasia plate resulted in the convective upwelling of the mantle in the bohai area and triggered the development of nne and ne striking extensional faults along the mesozoic structures in the late paleocene causing the formation of the rift basin during the oligocene the depocenters and subsidence centers of the greater bohai basin migrated from west to east and from south to north and finally concentrated in the offshore part of the basin since the oligocene especially during the neogene due to the indentation of the india block to the eurasia plate the right lateral strike slip movement of the tan lu fault was relatively intense in the offshore part of the basin these characteristics led to the differences between the offshore and onshore sectors in sedimentation structural features and petroleum geology during the deposition of the dongying formation the offshore sector became the depocenter and subsidence center of the basin resulting in the deposition of the lower dongying formation mudstone source rocks while these mudstones are immature in the onshore part of the basin in the offshore bohai most major discoveries have been made in the drape anticlines on the rises in the upper tertiary reservoirs while the lower tertiary reservoirs within the half grabens only serve as secondary reservoirs as the neogene depocenter of the basin the offshore part accommodated some fine grained shallow lacustrine clastics of the lower minghuazhen formation serving as important regional seals for the neogene reservoirs a set of shallow faults and a central faulted anticlinal belt in the shallow upper tertiary sequences were formed during the neogene in the offshore sector under the influence of right lateral strike slip faulting of the tan lu fault these shallow faults networked with deep extensional faults serving as hydrocarbon conduits the central faulted anticline belt along the tan lu fault system also provides significant traps

composition of the uralide crust from seismic velocity v p v s heat flow gravity and magnetic data abstract p wave velocity vp s wave velocity vs poisson s ratio heat flow potential field and surface geological data are integrated to constrain a model for the composition of the uralide crust along the urseis transect the model is constructed using published laboratory measurements of vp vs and density for a variety of crustal rock types these laboratory data have been corrected for depth pressure and the uralides temperature depth function the model shows clear differences between the composition of the old continental crustal nucleus of the east european craton and the newly added crust of the accreted arc terranes to the east the crust of the east european craton is more felsic than that of the magnitogorsk and east uralian zones and the latter two have a lowermost crust whose characteristics indicate a high garnet content mafic garnet granulite and or the presence of hornblendite the overall composition of the arc terranes is basaltic physical properties suggest that eclogite is not present in the arc terranes or if present it exists in small amounts that are below the resolution of the data set the lack of eclogite in the lower crust favours an intracrustal differentiation model for the evolution of the bulk composition of the continental crust nevertheless the absence of surface uplift the lack of metamorphism and late orogenic mantle melts and the current crustal thickness indicate that crustal thinning did not affect the bulk composition of the uralide crust

heterogeneous stretching simple shear and basin development abstract the models of basin development which involve either homogeneous stretching of the whole lithosphere or displacement on a lithospheric scale shear zone are but two end members of a range of possible extensional models the homogeneous extension model thins the lower lithosphere beneath the thinned upper crust and superimposes a thermal subsidence basin on the earlier fault bounded basin the shear zone model offsets the zone of lower lithospheric stretching and thermal subsidence it is more likely that the zones of upper and lower lithospheric stretching will be heterogeneous and patchy but will often overlap in plan view this will produce localised uplift and subsequent thermal subsidence within the faulted basin and may explain many of the anomalies between the various stretching estimates made using different structural stratigraphic and geophysical techniques the model which combines heterogeneous lithospheric stretching and associated simple shear may explain 1 variations in dip of the major detachment zones in the large basins 2 variations in types of strain on or beneath the detachment zones 3 regional uplift of part of a basin to erode the earlier fault blocks and 4 the development of volcanism in basins with only low values of upper crustal extension the zone of stretched lower crust and lithospheric mantle may lie beneath the centre of the zone of upper crustal stretching or to one side it may be linked to the upper crustal zone by faults which dip consistently in one direction or by extensional systems which change their dominant dip direction with depth pulling out the mid crust as one or more wedges possible examples are discussed from the basin and range province and northwest european continental shelf

structure of crust and upper mantle beneath the ordos block and the yinshan mountains revealed by receiver function analysis a temporary seismological network of broadband three component stations has been deployed n s to investigate the crust and upper mantle structure across the ordos block and the yinshan mountains p wave receiver functions reveal the moho depth to be about 41 km beneath the central ordos block and down to 45 km beneath the northern ordos block a slight uplifting to 42 43 km beneath the hetao graben increasing to 47 48 km beneath the yinshan mountains and then decreasing to 44 km beneath the northern yinshan mountains along the profile in the ordos block the crustal vp vs ratio about 1 80 south to the hetao graben differs from that about 1 75 beneath the center ordos block the crustal vp vs ratio is significantly lower about 1 65 1 70 beneath the yinshan mountains the p wave receiver function migration imaging suggests relatively flat discontinuities at 410 and 660 km indicating the lack of a strong thermal anomaly beneath this profile at these depths and a low s wave velocity anomaly in the upper mantle beneath the hetao graben we suggest that the low s wave velocity anomaly may be attributable to heat and that the thermal softening advances the evolution of the hetao graben while the lower crustal ductile flows transfer from the hetao graben to the northern ordos block resulting in crustal thickening

geological characteristics and distribution patterns of hydrocarbon deposits in the bohai bay basin east china abstract the bohai bay basin in east china is a meso cenozoic continental fault bounded basin with abundant petroleum resources based on analyses of sedimentation history and tectonic and thermal evolution the vertical and horizontal distribution patterns of oil and gas are discussed in this paper the basin has characteristics of multiple cycles of depression and uplift and each depression has its own sedimentary system and pattern of oil generation the main source rocks are of lower tertiary sediments characterized by multi cyclic sedimentation multiple source reservoir caprock associations were developed abrupt changes of sedimentary facies and the development of numerous faults caused the formation of various types of oil and gas reservoir that constituted multiple oil and gas accumulation zones based on individual structure zones these accumulation zones are mainly distributed around the centre of source rock deposits and are restricted in the areas where source rocks are distributed

the effect of sea level changes on the morphology of mountain belts we have examined quantitatively the effect of large 200 m long period 50 m y sea level changes on the development of the landscape of old mountain belts on the basis of the available data we have assumed that the rate of denudation of these old landscapes is proportional to the average regional elevation y by a constant k 10 4 1000 years the results are as follows 1 in the absence of large sea level changes it will take in excess of 300 m y and more likely more than 450 m y to degrade a himalayan size mountain belt y 5000 m to a peneplain y 10 m for an old mountain belt that has been eroded to a regional elevation of 500 m it will take an additional 220 m y and more likely 390 m y to degrade to a peneplain 2 in a system in which the river valleys are graded with respect to base level the rate of downcutting is enhanced by the rate of uplift caused by the isostatic response to regional denudation with sea level base level rising the rate of downcutting is decreased by the rate of rise however transgression of the river valleys cannot take place until the rate of river valley uplift caused by isostatic response to the denudation is equal to the rate of sea level rise under usual conditions of sea level rise nonglacial this will not occur until the landscape has been degraded to a regional elevation of 60 m or less however under these conditions the decrease in the rate of downcutting in the river valleys greatly enhances the rate of degradation as a consequence older mountain bells already eroded to a regional elevation of 500 m or less may be further degraded to a peneplain y 10 m during an episode of persistent sea level rise at rates of several tenths of a centimeter per 1000 years for several tens of millions of years with sea level falling the landscapes evolve toward an equilibrium surface at which point the rate of degradation is equal to the rate of sea level fall 3 we have applied these concepts to the post triassic evolution of the ridge and valley province of the appalachians sea level probably rose 300 m during the interval from 205 to 95 ma which was sufficient to degrade those areas with a regional elevation of 500 m or less to a peneplain subsequent to this time from 80 to 10 ma sea level has fallen approximately 300 m sufficient to cause emergence of the former peneplain to a regional elevation y of 215 m which is approximately equal to the present day regional elevation of the appalachians since the ridge and valley province near harrisburg we have made a further test of this by attempting to restore the remanent peneplain surface i e the schooley mountain surface to its former elevation in the upper cretaceous and thus estimate the height that sea level had to be at that time by infilling the valleys with country rock up to 457 m which is the present elevation of the presumed former peneplain remanent surface and making the appropriate isostatic adjustments we may conclude that at a minimum sea level was 277 m above present in the upper cretaceous finally we conclude that large scale peneplanation can only take place during episodes of significant sea level rise 250 m over long periods of time 50 m y thus episodes of extensive peneplanation are indicative of sea level changes of this magnitude

structural anatomy and dynamics of evolution of the qikou sag bohai bay basin implications for the destruction of north china craton abstract the qikou sag is a complex cenozoic faulted basin at the center of the bohai bay basin the paleogene sediments in the basin show a maximum thickness of 11 000 m in paleogene representing intense crustal extension the sag has a typical dish like structure in the upper part with the central domain represented by a deep half graben and surrounded by different types of gentle slopes and sub sags linked with the basin margin uplifts the inner structure of the sag is jointly controlled by the basin margin extensional faults intrabasinal extensional tectonics and transfer tectonics the sag is divided into four different extensional tectonic domains by the basement fault along the coastline the haihe xingang fault and the qidong fault these sub sags are in turn controlled by different detachment systems the listric cangdong and hangu faults mark the major boundary faults controlling the extensional structure of the basin the structure and tectonics of the qikou sag provide a direct record of the late stages of rifting and destruction of the north china craton the mesozoic basement structures of the sag determine the tectonic styles in different sub sags the complete inversion of the structures in mesozoic profoundly influenced the development and evolution of the basin during paleogene we identify three main stages in the tectonic evolution of the qikou the oligocene faulting stage the miocene pliocene thermal subsidence stage and the pleistocene quaternary depression stage in the oligocene fault activities and the basin architecture were mainly controlled by the listric boundary fault system of the basin and the secondary fault system in the hanging wall under the detachment and extension in the upper crust since miocene the boundary fault of the basin underwent weak extension the upwelling of the upper mantle and the formation of corresponding shallow depressions contributed to the evolution and tectonic architecture of the qikou sag

isostatic response of the lithosphere with in plane stress application to central australia the relation between gravity and topography in central australia cannot be described by a conventional isostatic response function whether it assumes local or regional compensation or whether the crust behaves as an elastic or viscoelastic medium in particular the response function exhibits considerable anisotropy hence a theory for isostatic response has been developed for a crust in mechanical equilibrium of surface loads buoyancy and in plane forces and subject to erosion sedimentation and stress relaxation the observed north south response function exhibits extreme isostatic overcompensation at some wavelengths and this can be fully explained by the viscoelastic plate model with in plane compression the observed east west response function is consistent with models of regional or local isostatic compensation the response function implies an effective flexural rigidity of 5 10 1022 n m an effective maxwell relaxation time of 25 50 m y an in plane compression of 125 150 mpa and an erosion time constant of about 200 m y these parameters assume that the model evolved over a period of about 700 m y and are wholly consistent with the evolutionary model developed from geological observations

stratigraphic and structural development of the eastern pontides turkey this paper describes the stratigraphic and structural development of the eastern pontides north turkey based on section logging at eight localities construction of three structural profiles across the mountains and published literature the eastern pontides comprise a late carboniferous to miocene sequence resting on a basement of hercynian metamorphics late carboniferous to scythian sediments are continental clastics interpreted as having been deposited in an extensional half graben the middle triassic is limestone reflecting the development of a south facing passive margin in the late triassic the ocean palaeotethys began to close flysch was deposited in most places with minor shallow water limestones in the sinemurian above an inverted half graben all pre aalenian strata were deformed during the cimmerian orogeny after a phase of subduction related volcanism in the mid jurassic limestones were deposited during the late jurassic and early cretaceous mainly in shallow water the aptian and albian are absent due to doming in the western pontides prior to the opening of the western black sea but there is a thick sequence of upper cretaceous arc volcanic rocks and intervening turbidites the upper palaeocene is absent possibly due to rifting in the eastern black sea major compression affected the pontides from the eocene to the pliocene associated with the closure of the tethyan ocean oligocene and younger rocks are accordingly non marine

the north anatolian fault zone distributed neogene deformation in its northward convex part abstract the north anatolian fault zone is composed of two almost rectilinear branches which join in a northward convex bend in this bent zone the pontide anatolide collisional system has been cut across by two transpressional belts of fold and thrust and wrench faults of lower neogene age these structures were reactived during the neotectonic period the time of deposition of the pontus group for both of these deformational events and up to the present the tectonic regime remained generally transpressional with a nw se direction of compression and a ne sw direction of extension it is only recently during the upper pleistocene that the dextral wrench faults became more localized and more straight than previously the complexity of the eastern part of the north anatolian fault zone is better understood if one takes into account the role of inherited miocene pliocene transpressional structures

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

evolution of the middle strand of north anatolian fault and shallow seismic investigation of the southeastern marmara sea gemlik bay abstract the gemlik bay is developed as a pull apart basin during the late pliocene early pleistocene mainly controlled by west trending dextral strike slip faults along the middle strand of the north anatolian fault zone with the nw trending thrace eskisehir fault playing secondary role the north anatolian fault reached the eastern marmara sea 3 5 ma ago where its middle strand intersected the thrace eskisehir fault gps slip vectors measured on the armutlu and mudanya blocks show a displacement of 7 8 km during the last 3 5 ma the middle strand of the north anatolian fault zone has lower tectonic activity than the northern strand because uplift of the southeast marmara sea region has been continuous since the late pliocene the presence of fluviatile lacustrine and deltaic environments in the gemlik pull apart basin over the same period supports a lower lever of tectonic activity the transgressive marmara formation was deposited on top of these fluvio lacustrine deposits following the mediterranean inundation at 600 ka via the strait of canakkale the gemlik basin was affected both by two major sea level falls at 160 132 and 24 11 ka and minor short lived sea level variations as a result of becoming a lacustrine setting five times since 600 ka during these lowstands stacked delta successions were deposited around the lake and on the transgressed shelves of the marmara sea

late cenozoic tectonics and volcanism along the north anatolian fault new structural and geochemical data abstract different types of volcanic activity have developed along the north anatolian fault zone naf in turkey detailed analysis of satellite images and digital elevation models dems and field observations have been made in order to understand the tectonics and the distribution of volcanic vents in the anatolian block some faults are oblique to the naf and delimit extensional escape wedges vents rooted on open tension fractures show that emplacement of the volcanism is related to tensional fracturing of the anatolian continental block which we attribute to the onset of free borders in the south and west along the naf earliest extension 1 is directed s to ssw and the latest 2 towards w to wsw parallel to the sinistral slip along the naf major and trace element geochemical data indicate that the dominant calc alkaline rocks are associated with various alkaline lavas k ar ages of the volcanics range from 22 to 8 5 ma in galatia massif 900 to 100 ka in niksar and 3 to 12 ka in erzincan isotopic and trace element data are interpreted as reflecting a dominantly lithospheric mantle source slightly mixed with asthenospheric liquids most magmas were fractionated and contaminated by continental crust during their ascent 1 and 2 tectono volcanic events have propagated through time and space from west to east the 1 extension is late oligocene in the galatia massif late miocene in niksar and late pliocene in erzincan the 2 extension and strike slip event along the naf began in the late miocene in the galatia massif early pliocene in niksar and quaternary in erzincan signature from an asthenospheric source in the second event in the three regions suggests that an ancient suture zone galatia massif and or the lithospheric naf transform niksar and erzincan have served to channel small quantities of asthenospheric melts existing at the base of the lithosphere

a detailed receiver function image of the sedimentary structure in the bohai bay basin abstract if the site at which receiver functions are constructed is filled by sediments then the waveforms from these receiver functions are dominantly controlled by the sedimentary structures within the first few seconds after the direct p arrival based on this observation waveform data collected at 44 temporary seismic stations have been used to image the sedimentary structure of the bohai bay basin a major continental petroliferous basin in eastern china an adapted hybrid global waveform inversion method was applied to the receiver functions to extract structural information beneath each of the stations the derived s velocity structure provides for the first time a basin scale seismic image of detailed sedimentary stratification the sedimentary cover of the basin is about 2 12 km thick consisting of cenozoic mesozoic and paleozoic strata from top to bottom the structural features presented in the s velocity image coincide quite well with the depression uplift type of tectonic system in the bohai bay basin the reconstructed morphology of the sedimentary layers provides seismological evidence for the two stage evolution of the intracontinental basin that were caused by an intensive tectonic regime transition in late mesozoic immediately following the lithospheric reforming of the eastern china continent

gps constraints on continental deformation in the africa arabia eurasia continental collision zone and implications for the dynamics of plate interactions 1 the gps derived velocity field 1988 2005 for the zone of interaction of the arabian african nubian somalian and eurasian plates indicates counterclockwise rotation of a broad area of the earth s surface including the arabian plate adjacent parts of the zagros and central iran turkey and the aegean peloponnesus relative to eurasia at rates in the range of 20 30 mm yr this relatively rapid motion occurs within the framework of the slow moving 5 mm yr relative motions eurasian nubian and somalian plates the circulatory pattern of motion increases in rate toward the hellenic trench system we develop an elastic block model to constrain present day plate motions relative euler vectors regional deformation within the interplate zone and slip rates for major faults substantial areas of continental lithosphere within the region of plate interaction show coherent motion with internal deformations below 1 2 mm yr including central and eastern anatolia turkey the southwestern aegean peloponnesus the lesser caucasus and central iran geodetic slip rates for major block bounding structures are mostly comparable to geologic rates estimated for the most recent geological period 3 5 myr we find that the convergence of arabia with eurasia is accommodated in large part by lateral transport within the interior part of the collision zone and lithospheric shortening along the caucasus and zagros mountain belts around the periphery of the collision zone in addition we find that the principal boundary between the westerly moving anatolian plate and arabia east anatolian fault is presently characterized by pure left lateral strike slip with no fault normal convergence this implies that extrusion is not presently inducing westward motion of anatolia on the basis of the observed kinematics we hypothesize that deformation in the africa arabia eurasia collision zone is driven in large part by rollback of the subducting african lithosphere beneath the hellenic and cyprus trenches aided by slab pull on the southeastern side of the subducting arabian plate along the makran subduction zone we further suggest that the separation of arabia from africa is a response to plate motions induced by active subduction

nonlinear latitudinal transfer of wave activity in the winter stratosphere partial support for this work was provided through the national science foundation award ags 1333029

some observations on basin evolution and dynamics sedimentary basin evolution is intimately bound in with continental lithosphere dynamics deep seismic reflection profiling has revealed images of the crust and upper mantle that suggest linkages between the shape and structure of sedimentary basins as they evolve with the rheological responses to tectonic stress of upper and lower crust and upper mantle components of the lithosphere this is well illustrated by the european geotraverse lithosphere profile from north cape norway to tunisia the alpine mountain belt has a lithospheric root as well as a crustal root by virtue of its asymmetric disposition this may be the cause of compressive and tensile forces in close association in the upper crust which have created mountain uplift and basin subsidence extension and thrusting all in juxtaposition evidence for an elastic upper layer of crust above a plastic substratum can be used as a basis for modelling basin geometry structure and stratigraphy built upon the flexural nature of the upper crust such models go a long way towards simulating the evolution of basins such as the north sea viking graben in more detail analogue structural models can reveal the geometry of basin fill in relationship to crustal movement and the relationships between structure and sedimentation patterns however sedimentary basin modelling needs to begin with the quantitative simulation of depositional environments in relation to such factors as tectonics sea level variations sediment supply and erosion in order to match sedimentary architecture only then can the range of deposits be placed in space and time within a basin environment as building blocks within a dynamically evolving structural framework to create predictive models for comparison with geological reality