the tectonics and petroleum system of the qiulitagh fold and thrust belt northern tarim basin nw china the timing of hydrocarbon charging relative to trap formation is a key factor for evaluating the exploration potential of the qiulitagh fold and thrust belt qftb on the north flank of the tarim basin data obtained by this study indicate that structural traps were filled by hydrocarbons in two episodes in this area at least four major deformation events have been identified for the period of late cretaceous to pliocene the first event occurred in late cretaceous and led to the formation of paleo uplift structures the second event was characterized by thrust features and occurred in latest oligocene the third and fourth events were represented by compressional structures that were developed in late miocene and late pliocene respectively based on oil and gas source rock correlations and 1 d basin modeling two episodes of hydrocarbon generation and migration are proposed to be responsible for oil and gas accumulations in the qftb the two episodes of hydrocarbon charging from a source kitchen north of the study area took place in early miocene and pliocene respectively since the qftb was uplifted in late oligocene and late miocene the hydrocarbon generated during all two periods could migrate toward this area to form oil and gas accumulations in suitable structures

the grace satellite gravity and geoid fields in analysing large scale cratonic or intracratonic basins the recently released gravity potential field development derived from the gravity recovery and climate experiment satellite allows an unprecedented opportunity to use the gravity field to make global comparisons of structures of geological interest the spatial resolution of the gravity field is sufficiently good to map large scale or intracratonic and cratonic basins as the areal extent of these basins is 0 5 x 10 6 km 2 and greater we present the gravity anomaly bouguer geoid and terrain corrected geoid fields for a selection of nine large scale basins and show that the satellite derived field can be used to successfully identify distinctive structures of these basins e g extinct rifts underlying the basins and generally the isostatic state the studied basins are the eastern barents sea west siberian tarim congo michigan amazon solimoes parnaiba and parana basins we complete the mapping of the gravity field with a description of the basins in terms of areal extension and depth sedimentary age and presence and age of volcanism interpretation of the satellite gravity anomalies and considerations regarding the crustal thickness as known from seismic investigations allows us to conclude that for the greater part of the basins there is evidence for high density material in the lower crust and or upper mantle this density anomaly is at least partly compensating for the low density sedimentary infill instead of the crustal thinning mechanism for our selection of basins crustal thickness variations and moho topography cannot be considered as mechanisms of compensation of the sedimentary loading which is a clear difference to well defined rift basins

analyses of fault mechanisms and expansion of southwestern anatolia since the late miocene abstract neotectonic field studies and detailed analyses of neogene and quaternary fault mechanisms in southwestern anatolia enable us to recognize a succession of compressional and extensional events and to characterize the direction of corresponding regional stresses the three most important compressive phases occurred during the miocene and a much smaller one near the plio quaternary boundary the last one or two interrupted a widespread extension of much greater duration and amplitude the whole tectonic evolution resembles that of the aegean the large extension by normal faulting is consistent with a minimum stress along a nne ssw average direction it appears that this direction was n s during the pliocene and changed to ne sw sometime during the quaternary this dominant nne ssw extension which began during late miocene or earliest pliocene was related to the development of the southwestern anatolian graben system

three dimensional seismic geomorphology and analysis of the ordovician paleokarst drainage system in the central tabei uplift northern tarim basin western china high quality three dimensional seismic data acquired in the central tabei uplift tarim basin western china provide a rare opportunity to characterize in exceptional detail the three dimensional geomorphology of a deeply buried 5500 6500 m 18 045 21 325 ft ordovician unconformity and the related paleokarst drainage system an integrated approach was applied that emphasized integration of seismic data with available conventional core wireline logs and age equivalent outcrops the exceptional quality of the seismic data allowed a seismic detection limit of karstified features of less than 75 75 m 246 246 ft horizontally and 6 m 20 ft vertically interpreted geomorphologic and depositional elements include fluvial channels and canyons fluvial valleys sinkholes and tower karsts and hills the modern tower karst drainage system in guilin china is very similar to the mapped ordovician karst drainage system and is used as a modern analog the interaction between the surface karst drainage system and the shallow subsurface cave passage system is evidenced by the observation that surface canyons appear to initiate in areas associated with intense sinkhole development also surface river valleys tend to correspond to dip oriented surface depressions partly related to near surface cave collapse during burial into the deeper subsurface the combination of intrastratal collapse karstified strata and suprastratal collapse postkarst deposited strata created large damage zones hundreds of meters thick and kilometers wide coalesced collapsed paleocave systems can be interpreted from the unique circular pattern of faults observed in map view that are associated with seismic bright spots

sedimentation in pull apart basins active examples in eastern turkey the erzincan susehri niksar and lake hazar basins are actively evolving pull apart basins in eastern turkey their structural drainage and depositional systems generally support a pull apart basin sedimentation model based on ancient pull apart basin deposits this model involves marginal coarse grained sedimentation adjacent to master faults axial fine grained sedimentation away from master faults and high sedimentation rates however studies of the turkish pull apart basins suggest the following refinements in the model 1 detailed sedimentary facies patterns and the dominant facies of a pull apart basin vary according to basin shape climate drainage character and volcanic activity depositional environments near fault bounded margins include alluvial fan fan delta and alluvial apron depositional environments in central areas away from fault bounded margins include active braid plain inactive braid plain meander plain salt playa marsh lacustrine mouth bar delta and volcanic 2 i

strike slip duplexes abstract strike slip fault systems often contain zones of steep imbricate faults geometrically similar to imbricate fans and duplexes in dip slip thrust and normal fault systems they are evident in map view rather than in vertical sections examples of duplexes are cited from both active and ancient systems and from theoretical and physical models duplexes may form at bends on strike slip faults by a process kinematically analogous to the sequential imbrication of ramps on dip slip faults however some may form and many may initiate as non sequential riedel fractures at fault offsets or on straight fault segments this process is more marked than in dip slip systems where primary anisotropy such as bedding exerts more control on fault geometry strike slip duplexes may be shunted along the fault system parallel to the regional slip vector however duplexes or individual horses will usually also move up or down perpendicular to the slip vector because of the unconstrained upper surface to the fault system these factors mean that no section through a strike slip system should be expected to area balance the faults of strike slip duplexes and imbricate fans may root in kinematically necessary low dip faults or may converge downwards and appear in vertical sections as flower structures

middle late jurassic tectonostratigraphic evolution of central asia implications for the collision of the karakoram lhasa block with asia mesozoic basins in different regions of central asia provide important records for investigating relationships between intraplate deformation in central asia and tectonic processes at asian boundaries the present study gives a review of the stratigraphic and structural evolution of basins in different regions of central asia during the middle late jurassic it is shown that basins and mountain belts in northwest china experienced compressional deformation and were wholly or partially uplifted during the late middle late jurassic compared to extensively distributed middle jurassic coal bearing strata in northwest china upper jurassic strata characterized by red mudstones and conglomerates have a much smaller distribution in the mean time the tibet pamir plateau also underwent a folding and uplift event and upper jurassic sedimentary rocks are generally missing in the pamir and western tibet the intense compressional deformation and uplift event of the late middle late jurassic from the tibet pamir plateau to northwest china requires a new tectonic model as proposed here we suggest that the karakoram and lhasa blocks were a single giant block which was accreted to asia in the late middle jurassic earliest cretaceous and cross cut by the karakoram fault in the cenozoic during the callovian the western part of the karakoram lhasa block initially collided with the southern asian margin collision and continued convergence during the late middle late jurassic caused sinistral strike slip faulting along the central badakhshan fault and south tian shan suture accommodating crustal shortening in areas to the southeast of the faults the pamir western tibet tarim block qilian qaidam block and bei shan meanwhile the northeastward transpressional motion of the tarim block produced strong compressional stresses to areas north of the tarim block the kyrgyz tian shan central tian shan junggar basin and turfan basin with the northward movement of the karakoram lhasa block the eastern part of the karakoram lhasa block began to collide with the southern asian margin during the latest jurassic earliest cretaceous resulting in strong crustal deformation and thickening in east asia and central asia

cenozoic deformation of the tarim basin and surrounding ranges xinjiang china a regional overview abstract with its central position between the tibetan plateau and the tian shan range the tarim basin is a key element of the cenozoic asian orogenic system however a comprehensive regional study and more particularly the quantification of shortening through this basin and its margins are still needed to understand its role in the cenozoic deformation of asia from a compilation of previous works together with an extensive dataset of satellite field seismic and well data we provide a tectonic map of the cenozoic structures and four balanced geological transects of the tarim basin and its surrounding ranges based on this map and these cross sections we characterize the cenozoic deformation of the original proterozoic tarim block from structural restorations and crustal budgets we also quantify the compressive component of this deformation most of the cenozoic compressive deformation from 94 to 100 is concentrated in the ranges along the block margins to the west up to 78 23 km and 54 24 18 km of crustal shortening are accommodated across the compressive western kunlun and southwestern tian shan ranges while to the east up to 38 6 18 km and 15 20 15 km are accommodated across the transpressive altyn tagh and southeastern tian shan ranges a non negligible amount of compressive deformation up to 6 is also accommodated within the tarim basin by large basement cored uplifts with a vergence synthetic to the deformation of the tibetan plateau edge to the west the bachu uplift absorbs 5 km of the total crustal shortening of the western kunlun thrust system while to the south the tanan uplift accumulates 0 6 km of the altyn tagh strike slip system structural inheritance has a major influence on the cenozoic deformation since 33 3 to 100 of the total shortening is accommodated by reactivated basement structures inherited from the protero paleozoic history of the tarim block finally we argue that the basement cored uplifts in the centre of the basin imply a deformation transfer from the tibetan plateau to the tian shan above a deep crustal decollement decoupling the deforming crust from an underlying rigid mantle

early miocene kirka phrigian caldera western turkey eskisehir province preliminary volcanology age and geochemistry data abstract large rhyolitic ignimbrite occurrences are closely connected to the early miocene initiation of extension in the central western anatolia crossing the tavsanli afyon zones field and laboratory data performed at the apex of the eskisehir afyon isparta volcanic area allowed recognition of newly identified caldera structure named here kirka phrigian caldera transtensive distensive tectonic stresses since 25 ma ago resulted in the nnw sse elongation of the magma chamber and influenced the roughly elliptical shape of the subsided block caldera floor the caldera which is roughly oval 24 km 15 km in shape formed during a series of collapse events starting at 19 ma by the generation of a huge volume of extra and intracaldera ignimbrites intracaldera post collapse sedimentation and further volcanism at the northern edge at 18 6 ma were controlled through subsidence related faults with generation of a series of volcanic structures domes and lavas showing a large compositional range enriched mantle components within the subcontinental lithospheric mantle began to melt via decompression melting during the initiation of extension the heat resulting from the fractionation of ascending mantle melts produced the silicic compositions in large mushy crustal reservoirs interaction of these melts with fertile crustal rocks further caused crustal anataxis and consequently two different compositions rhyolite 1 and rhyolite 2 the eruptions of kirka phrigian caldera related ignimbrites were probably triggered by basaltic intrusion rock volumes and geochemical evidence suggest that silicic volcanic rocks come from a long lived complex magma chamber system after caldera generation there was a northern shift to small volume extra and intra caldera episodic rhyolitic basaltic trachy andesitic trachytic and lamproitic volcanism the latter being the youngest 16 2 ma indicating a more primitive magma input which originated in an enriched mantle lithosphere the rock succession provides a direct picture of the state of the magmatic system at the time of eruptions that generated caldera and post caldera structures and offers an excellent example of silicic magma generation and associated potassic and ultrapotassic intermediate mafic rocks in a post collisional extensional setting

growth destruction and volcanic facies architecture of three volcanic centres in the miocene usak gure basin western turkey subaqueous subaerial volcanism in a lacustrine setting abstract early to mid miocene extension in western anatolia related to plate tectonic motions resulted in the development of a number of normal fault bounded sedimentary basins as well as different styles and compositions of volcanic activity the usak and gure basins accumulated a thick fluvio lacustrine fill in which three distinct volcanic edifices elmadag itecektepe and beydagi and their deposits can overlap with each other and with the sediments produced by the background sedimentation in addition complete facies architectures of small volume monogenetic volcanoes have been recognised in association with the three large complex polygenetic volcanoes providing a complex mixed siliciclastic and volcaniclastic basin infill in the respective basins where volcanism took place all three volcanic centres display a complex succession of effusive and explosive volcanisms and their reworked deposits with abundant evidences of magma water interaction such as peperites for non explosive magma water interaction with the lacustrine water saturated sediment and standing water body in a large alkaline lake during the constructive phase proximal successions of pyroclastic flows pyroclastic falls and rarely surge deposits are associated with distally emplaced debris flow deposits sometimes of mixed volcanogenic and terrestrial origins and are interbedded with lacustrine sediments of the inay group all three volcanic centres then experienced a phase of volcano growth and degradation between 17 and 15 ma ago most likely related to a combination of tectonic movements on ne sw trending basement faults which triggered multiple flank collapses and volcanic debris avalanches elmadag and voluminous ignimbrite eruptions that triggered caldera formation itecektepe and beydagi volcanic centres lacustrine conditions persisted during the destruction and post destruction stages of the volcano s evolution as evidenced by indications of magma water interactions within the central collapse structures which also contain uplifted basement metamorphic rocks now exhumed in their eroded cores

formation and evolution of strike slip faults rifts and basins during the india asia collision an experimental approach the processes which have governed the formation and evolution of large tertiary strike slip faults during the penetration of india into eastern asia are investigated by means of plane strain indentation experiments on layered plasticine models the steady state deformation of plasticine obeys a power creep flow law e c t n the stress exponent n is between 6 and 9 at 25 c uniaxial plane strain tests on cubic specimens show that the growth of faults in layered plasticine results from strain softening a process observed for strain rates ranging from 3 5 10 5 to 3 6 10 3 s 1 fault or shear zones form after only 7 10 bulk strain subsequent deformation is controlled by the geometry of the fault pattern rather than the physical properties of the plasticine a series of nine plane strain indentation experiments shows the influence of boundary conditions as well as that of the internal structure of the plasticine model on the faulting sequence the ubiquity of strain softening in experimental deformation of a variety of rocks as well as the widespread occurrence of shear zones in nature suggest that long term deformation of the continental lithosphere may also be primarily influenced by the geometry of large faults which rapidly develop with increasing strain the deformation and faulting sequence observed in the plasticine indentation experiments may thus be compared to collision induced strikeslip faulting in asia particularly to total offsets and rates of movements on the faults the experiments simulate the evolution of the western ends of the strike slip faults which have probably been analogous to trench fault fault triple junctions the experiments also illustrate mechanisms for the formation of extensional basins such as the south china sea north china basin and andaman sea near active continental margins the basins which appear to absorb terminal offsets along major strike slip faults near such margins may result from mismatch between the sharply angular shape of the deformed continental edge and the more regularly curved trench along which the smoothly flexed oceanic lithosphere subducts the existence of distinct phases of strike slip extrusion corroborates the idea that the discontinuities in time which typify intracontinental tectonics and orogenic cycles may often result from strain localization and the ensuing discontinuous non steady state deformation of the continental lithosphere

multiple stage migration and accumulation of permian lacustrine mixed oils in the central junggar basin nw china abstract the permian lacustrine petroleum system in the central junggar basin northwest china has recently obtained exploration success these accumulations are characterized by mixed oils and multiple stage migration and accumulation this process however has not been well constrained limiting the understanding of the general laws of hydrocarbon migration and accumulation and making it difficult to define exploration strategies here we reconstruct this process mainly based on oil bearing fluid inclusion analyses including petrography homogenization temperature and sequential extraction inclusion petrography shows that petroleum inclusions dominantly display yellow fluorescence while intergranular free oils mostly display strong blue green fluorescence this implies that the reservoirs seem to have experienced at least two stages of hydrocarbon charge from different sources and or maturities the sources maturities are determined through reservoir sequential extraction analyses the free oils are mixed and sourced from the lower permian fengcheng formation p1f and the middle permian lower wuerhe formation p2w while the inclusion oils are also mixed and derived mainly from the p1f source both oils are characterized by moderate maturity homogenization temperature measurements of oil bearing fluid inclusions combined with reconstruction of reservoir burial and thermal history not only further verify multiple hydrocarbon charging events but also characterize the timing which indicates a three stage petroleum charging model during the first stage of the late triassic carboniferous reservoirs were charged by p1f sourced oils which were dysmigrated or remigrated to jurassic reservoirs during the second stage i e the early cretaceous in contrast the third stage from the late cretaceous represents another hydrocarbon charge event that is the primary oil accumulation sourced from the p2w rocks according to this model both primary and secondary oil accumulations contribute to the current region s exploration success and provide future exploration targets

prediction of ultrathin lacustrine sandstones by joint investigation of tectonic geomorphology and sedimentary geomorphology using seismic data abstract weak seismic signals from ultrathin 1 7 m sandstones increase uncertainties of thickness estimation imposing a significant challenge for accurate prediction of subtle hydrocarbon reservoirs these types of uncertainties however can be reduced by a combined use of kinematic travel time and dynamic amplitude information extracted from 3d seismic data in this case study in the kuqa depression of the tarim basin china we conducted an investigation of seismic based tectonic geomorphology and then sedimentary geomorphology in four steps 1 reconstruction of basin floor paleogeomorphology using a residual structure map of a closely underlain erosional unconformity 2 study of seismic lithology by seismic modeling and 90 phase adjustment of seismic traces 3 mapping of geomorphologic patterns of depositional systems on stratal slices and 4 combined analysis of tectonic geomorphology and sedimentary geomorphology for a better understanding of depositional history and reservoir distribution results show a good match between valley and lowland systems on the basin floor sandstone thickness trend and lobate sedimentary geomorphologic patterns indicating a widespread yet laterally highly variable ultrathin sandy fan delta system

the east anatolian fault an oblique collisional belt abstract the tectonic setting for the area around the arabia africa anatolia triple junction is described from combined landsat spot satellite image analysis and field observations since the late miocene the motion along the east anatolian fault generated major structures corresponding to shortening with a sinistral slip component the 150 km wide area of the triple junction is highly deformed by folding and thrusting distributed mainly on the border of the anatolian block in addition kinematic reconstructions confirm that the arabia anatolia relative motion is both sinistral and convergent the sinistral strike slip faults of the east anatolian fault zone are of second order and local consequences of the n s arabia anatolia collision

late paleozoic depositional history of the tarim basin northwest china an integration of biostratigraphic and lithostratigraphic constraints this study provides the first detailed lithostratigraphic and biostratigraphic constraints for improving stratigraphic resolution for hydrocarbon prospecting and exploration in the tarim basin a total of 49 stratigraphic units 38 formations and 11 members ranging in age from the latest devonian to permian are reviewed or redefined in terms of nomenclatures lithology age constraints and lateral distributions based on the detailed field works or newly published data of these the piqiang formation new formation is proposed to include the reefal carbonates of asselian sakmarian age from the northern tarim the subsurface upper paleozoic stratigraphic framework of the desert areas of the basin is also established for the first time the high resolution basinwide stratigraphic correlations reveal that the sedimentation of the basin in the late paleozoic was extremely uneven of these the famennian to changhsingian successions are completely recorded in the southwestern margin areas of the basin here five eustatic sedimentary cycles are well recognizable suggesting the sedimentation was more eustatically controlled and little affected by local tectonism the late paleozoic successions of both kalpin and taklimakan regions are commonly interrupted by major hiatuses at various horizons suggesting that the sedimentation was apparently modified by local tectonism of these the northward movement of the tarim block and its subsequent collision with the yili microcontinent part of the kazakhstan plate may be principally accountable for the discrepancy in the sedimentation of the various regions in the basin in the late paleozoic

late cenozoic slip on the talas ferghana fault the tien shan central asia although cenozoic crustal shortening and thickening by thrust faulting have built the present tien shan active right lateral shear on the northwest trending talas ferghana fault appears to be the most rapid localized deformation in the belt ephemeral stream valleys have been offset right laterally tens of metres new and published radiocarbon dates of organic material deposited in depressions blocked by offset ridges place upper bounds on the average holocene slip rate at 18 localities uncertainties allow 14 upper bounds to overlap the range of 8 16 mm yr and 95 confidence limits on such bounds at 11 sites are entirely within this range we infer that the rate of 10 mm yr is not simply an upper bound but applies to the late holocene epoch although the bounds on rates permit more rapid slip in the northwest than the southeast they do not place a useful constraint on variations in slip rate along the fault offsets of paleozoic facies boundaries imply a total right lateral shear of 180 250 km but early cretaceous sedimentary rock appears to have been offset only 60 10 km published paleomagnetic declinations of cretaceous miocene rock demonstrate 20 30 of counterclockwise rotation of the ferghana valley which lies just west of the talas ferghana fault with respect to stable parts of eurasia and 20 11 with respect to the central tien shan east of the fault these declinations are consistent with a maximum northwestward translation of 70 210 km of the ferghana valley at the talas ferghana fault and therefore with a similar maximum horizontal shortening across the chatkal ranges which lie between the ferghana valley and the kazakh platform estimates of crustal thickness beneath the chatkal ranges however permit only 60 100 km of cenozoic shortening if 100 km of slip on the talas ferghana fault accumulated at a constant rate of 10 mm yr it would imply an initiation of slip more recently than ca 10 ma long after india collided with the rest of eurasia

insights into the damage zones in fault bend folds from geomechanical models and field data abstract understanding the rock mass deformation and stress states the fracture development and distribution are critical to a range of endeavors including oil and gas exploration and development and geothermal reservoir characterization and management geomechanical modeling can be used to simulate the forming processes of faults and folds and predict the onset of failure and the type and abundance of deformation features along with the orientations and magnitudes of stresses this approach enables the development of forward models that incorporate realistic mechanical stratigraphy e g the bed thickness bedding planes and competence contrasts include faults and bedding slip surfaces as frictional sliding interfaces reproduce the geometry of the fold structures and allow tracking strain and stress through the whole deformation process in this present study we combine field observations and finite element models to calibrate the development and distribution of fractures in the fault bend folds and discuss the mechanical controls e g the slip displacement ramp cutoff angle frictional coefficient of interlayers and faults that are able to influence the development and distribution of fractures during fault bend folding a linear relationship between the slip displacement and the fracture damage zone the ramp cutoff angle and the fracture damage zone and the frictional coefficient of interlayers and faults and the fracture damage zone was established respectively based on the geomechanical modeling results these mechanical controls mentioned above altogether contribute to influence and control the development and distribution of fractures in the fault bend folds

extracting ocean generated tidal magnetic signals from swarm data through satellite gradiometry ocean generated magnetic field models of the principal lunar m2 and the larger lunar elliptic n2 semidiurnal tidal constituents were estimated through a comprehensive inversion of the first 20 5 months of magnetic measurements from european space agency s esa swarm satellite constellation mission while the constellation provides important north south along track gradiometry information it is the unique low spacecraft pair that allows for east west cross track gradiometry this latter type is crucial in delivering an m2 estimate of similar quality with that derived from over 10 years of champ satellite data but over a shorter interval at higher altitude and during more magnetically disturbed conditions recovered n2 contains nonoceanic signal but is highly correlated with theoretical models in regions of maximum oceanic amplitude thus satellite magnetic gradiometry may eventually enable the monitoring of ocean electrodynamic properties at temporal resolutions of 1 to 2 years which may have important implications for the inference of ocean temperature and salinity

using fluvial cyclicity to decipher the interaction of basement and fold thrust belt tectonics in a broken foreland basin vinchina formation miocene northwestern argentina abstract the miocene vinchina formation is made up of more than 5100 meters of siliciclastic sediments deposited mostly in fluvial environments in a broken foreland basin without any connection with the sea during a period of arid to semiarid climatic conditions repetitive changes in fluvial facies allow the subdivision of the formation into seven cyclothems each floored by a subaerial unconformity within sequence changes in fluvial systems determined by the proportion of channel vs floodplain multi story vs single story channels and channel connectedness were controlled by changes in accommodation proximal i e northern and younger sequences show transitions from braided to low sinuosity wandering or high sinuosity meandering fluvial systems whereas more distal sequences southern and older show changes from sand bed dominated to anastomosed systems bounding unconformities and facies stacking patterns are used to define six third order depositional sequences depositional sequences in the vinchina formation are either asymmetrical showing a fining upward trend or nearly symmetrical sand clock type each cyclothem is bounded by an incision surface sequence boundary developed during a base level i e fluvial equilibrium profile fall and initial base level rise floored by basal coarse grained deposits representing the low accommodation systems tract last the overlying sediments fine upward and contain both isolated and multistory sandstone bodies within extensive flood plain deposits corresponding to the early high accommodation systems tract hast this interval is sometimes capped by sheets of amalgamated sandstones corresponding to the late hast and developed during a decline in the rate of base level rise the development and or preservation of the capping amalgamated sandstones and therefore the symmetrical shape of the sequences is favored in high accommodation settings vertical and lateral facies changes recorded in the vinchina formation indicate that both the fold and thrust belt located to the west and an uplifted basement block to the north played important roles controlling subsidence source areas and drainage patterns the stratigraphic record of this broken foreland basin differ from the existing models for simple foreland basins and can be compared to those of the laramide sedimentary basins in the united states

cenozoic deformation of the kalpin fold and thrust belt southern chinese tian shan new insights from low t thermochronology and sandbox modeling abstract the kalpin fold and thrust belt ftb was active during the cenozoic and accommodated crustal shortening between the tian shan and tarim basin to constrain the timing of thrusting in the yimugantawu and kepingtag thrust sheets from north to south in the central area of the kalpin ftb we performed apatite fission track aft and apatite u th he ahe dating as well as sandbox experiments the aft central ages of the yimugantawu and kepingtag thrust sheets range from 93 0 to 148 7 ma single grain ahe ages of the kepingtag thrust sheet 10 7 27 1 ma are younger than those of the yimugantawu thrust sheet 15 1 82 5 ma indicating a southward propagation of the cenozoic deformation combined inverse and forward thermal modeling suggest that the yimugantawu and kepingtag thrust sheets underwent initial cooling and deformation at 25 20 ma and 15 10 ma respectively the sandbox experiments also suggest that the yimugantawu thrust sheet underwent deformation before the kepingtag thrust sheet was activated confirming the sequence revealed by low t thermochronology this study provides new insights into the timing of deformation at the northern margin of the tarim basin which can significantly enhance understanding of the tectonic evolution of central asia

impacts of the tectonic stress field on natural gas migration and accumulation a case study of the kuqa depression in the tarim basin china stress fluid and temperature are three of the major factors that impact natural gas migration and accumulation in order to study the influences of tectonic stress field on natural gas migration and accumulation in low permeability rocks we take the kuqa depression as an example and analyze the evolution of the structure and tectonic stress field at first then we study the influences of tectonic stress field at different tectonic episodes on fractures and fluid potentials through the numerical simulation method on the section across the kl2 gas field we summarize two aspects of the impact of the tectonic stress field on natural gas migration and accumulation firstly under the effects of the tectonic stress field the rock dilation increases with the added stress and strain and when the shear stress of rock exceeds its shear strength the shear fractures are well developed on one hand the faults which communicate with the hydrocarbon source rocks become the main pathways for natural gas migration on the other hand these positions where fractures are well developed near faults can become good reservoirs for natural gas accumulation secondly because fluid potentials decrease in these places near the faults where fractures are well developed natural gas can migrate rapidly along the faults and accumulates the impact of tectonic stress fields on natural gas migration and accumulation allows for hydrocarbon migration and accumulation in the low permeability rocks in an active tectonic compressive setting

lithospheric structure of western tibet a brief review abstract over the course of the last hundred years or so there have been countless seismic experiments conducted under the aegis of different research programs which have aimed to investigate the structure of the crust and uppermost mantle of the western tibetan plateau however there have been fewer detailed lithographic studies of the western sector of the tibetan plateau and those that have been conducted have principally fallen under the research umbrella of the antilope array network of tibetan international lithospheric observation and probe experiments in this paper we summarize the important research findings that have been gathered using comprehensive geophysical profiles and provide an overall view of the lithospheric structure of the western tibetan plateau that has resulted from the onset of tectonic collision and the continuous convergence of the indian and eurasian plates since 65 ma ago in western tibet the subducted indian lithospheric mantle is moving towards the northern edge of the plateau colliding with the tarim basin at 80 e however the tarim basin shows different nature of subductions in eastern central and western regions itself the maximum moho depth 93 km beneath the qiangtang terrane marks the northern margin of the decoupled underthrusting indian plate s lower crust and the lithospheric mantle the broader stronger terrain of the western tibetan plateau may indicate an eastward broadening shape and a lower cenozoic shortening and the relatively larger width of the lhasa qiangtang terranes may be a key factor controlling the geodynamic evolution of the tibetan plateau

resolution of direction of oceanic magnetic lineations by the sixth generation lithospheric magnetic field model from champ satellite magnetic measurements the champ satellite continues to provide highly accurate magnetic field measurements from decreasing orbital altitudes 350 km at solar minimum conditions using the latest 4 years 2004 2007 of readings from the champ fluxgate magnetometer including an improved scalar data product we have estimated the lithospheric magnetic field to spherical harmonic degree 120 corresponding to 333 km wavelength resolution the data were found to be sensitive to crustal field variations up to degree 150 down to 266 km wavelength but a clean separation of the lithospheric signal from ionospheric and magnetospheric noise sources was achieved only to degree 120 this new mf6 model is the first satellite based magnetic model to resolve the direction of oceanic magnetic lineations revealing the age structure of oceanic crust

seismic interpretation of the kelasu triangle zone in the southern tian shan foothills northwestern china seismic reflection data show that the kelasu structure a frontal structure of the south tian shan foothills thrust belt is a triangle zone with the upper detachment following an overpressured lower tertiary anhydrite zone and the lower detachment zone probably in the lower mesozoic seismic reflectors the south verging thrusts emerging at the surface are the small roof structures rooted in the upper detachment although the upper detachment was a relatively lubricated surface the passively folded formations show strong resistance to the blind wedging underneath particularly in the anticlines during the triangle zone development as a result of the massive shear forces created by the opposing movement of the two tectonostratigraphic units the top part of the thrust sheets immediately under the crest of the frontal anticline was ripped off in the form of backthrusting and brecciation the large backthrust fault blocks and breccias were retained in the anticlines whereas the underlying duplex continued wedging toward the foreland in the early formed duplex structures in the hinterland the tips of the thrust sheets were completely shredded leaving sharp angular contacts between the thrust sheets and the upper detachment surface different types of fractures and present day geostress stress of the earth measured along the wellbore interpreted from the borehole image logs suggest a complex deformation history and reversal of geostress the kelar gas reservoirs are located within the backthrust fault blocks under the frontal anticline the current model reduces the previous concerns about potential damage to the anhydrite seal by the surface thrusts because the thrusts occurred entirely above the seal more importantly because the reservoir rocks are repeated many times in the duplex thrust sheets below the continuous anhydrite seal any anticlinal structure of the upper detachment surface is a potential prospect

effect of basement structure and salt tectonics on deformation styles along strike an example from the kuqa fold thrust belt west china abstract the kuqa fold thrust belt kftb has a complex thrust system geometry and comprises basement involved thrusts decollement thrusts triangle zones strike slip faults transpressional faults and pop up structures these structures combined with the effects of paleogene salt tectonics and paleozoic basement uplift form a complex structural zone trending e w interpretation and comprehensive analysis of recent high quality seismic data field observations boreholes and gravity data covering the kftb has been performed to understand the characteristics and mechanisms of the deformation styles along strike regional sections fold thrust system maps of the surface and the sub salt layer salt and basement structure distribution maps have been created and a comprehensive analysis of thrust systems performed the results indicate that the thrust fold system in paleogene salt range can be divided into five segments from east to west the kela 3 keshen dabei bozi and awate segments in the easternmost and westernmost parts of the paleogene salt range strike slip faulting and basement involved thrusting are the dominant deformation styles as basement uplift and the limits of the cenozoic evaporite deposit are the main controls on deformation salt core detachment fold thrust systems coincide with areas of salt tectonics and pop up imbricate and duplex structures are associated with the main thrust faults in the sub salt layer distribution maps of thrust systems basement structures and salt tectonics show that paleozoic basement uplift controlled the paleozoic foreland basin morphology and the distribution of cenozoic salt in the kftb and thus had a strong influence on the segmented structural deformation and evolution of the fold thrust belt three types of transfer zone are identified based on the characteristics of the salt layer and basement uplift and the effects of these zones on the fault systems are evaluated basement uplift and the boundary of the salt deposit generated strike slip faults in the sub salt layer and supra salt layers at the basin boundary model a when changes in the basement occurred within the salt basin strike slip faults controlled the deformation styles in the sub salt layer and shear zone dominated in the supra salt layer model b a homogeneous basement and discontinues salt layer formed different accommodation zones in the sub and supra salt layers model c in the sub salt layer the thrusts form imbricate structures on the basal decollement whereas the supra salt layer shows overlapping discontinuous faults and folds with kinds of salt tectonics and has greater structural variation than the sub salt layer

junggar turfan and alakol basins as late permian to early triassic extensional structures in a sinistral shear zone in the altaid orogenic collage central asia the junggar turfan and alakol basins in northwestern china and kazakhstan formed as late permian to early triassic extensional structures in a broad sinistral shear zone between large strike slip faults that separate two main domains of the altaid orogenic collage this extension was in response to an inferred large l000 km sinistral motion of the east european craton with respect to the angaran craton during this time deformation associated with the formation of the basins was taken up in part by counter clockwise rotations of crustal blocks with respect to the altaid orogenic collage and to the angaran craton this event is the only important phase of extension in a region otherwise dominated by compressional tectonics throughout the phanerozoic the basement rocks of these basins formed by altaid subduction accretion through the latter half of the palaeozoic and the region was subsequently thrown into compression again during the mesozoic cimmeride and cenozoic alpide evolution

characterization of braided river delta facies in the tarim basin lower cretaceous application of borehole image logs with comparative outcrops and cores abstract borehole electrical image log with core like presentation is an efficient way to conduct sedimentary description in the subsurface the key is to set up a series of geological diagnostic criteria the subsurface lower cretaceous bashijiqike formation in the kelasu belt kuqa depression described as a sedimentary facies of braided river delta front has measured a mass of borehole image logs and open hole logs at depths more than 6000 m combined with comparative outcrops limited cores and thin sections high quality borehole images were fine calibrated to reveal their sedimentary details with the aim of subtle sedimentary interpretation in the uncored intervals the image elements all have corresponding geological indications the lithologies are interpreted including mudstones siltstones fine and medium sandstones and conglomerates and the sedimentary structures are interpreted in terms of various bedding types scoured surface and stacking modes thus interdistributary bay sandy or conglomerate subaqueous distributary channel and channel mouth bar are interpreted based on the lithologies sedimentary structures and textures basal and top contacts and succession variations furthermore determination of paleo current direction using borehole image logs is proposed for some time but is far from mature and need to consider tectonic deformation settings of studied stratigraphy based on this the paleo current in the kelasu belt is interpreted to flow southward from the southern tianshan to the depression during the early cretaceous which is consistent with the results derived from the heavy mineral analysis however the subaqueous distributary channels could frequently migrate locally and the paleo current direction changed at localities with an offset angle varied between 30 and 150 regionally the scale of single sand body decreases lakeward and the sand body may stretch at a maximum distance of 685 1 m along the flow direction the diagnostic criteria and the workflow for borehole image interpretation in this study will have potential application to subsurface sedimentary description and guide sedimentary architecture where cores are not available

tectonic implications of mars crustal magnetism mars currently has no global magnetic field of internal origin but must have had one in the past when the crust acquired intense magnetization presumably by cooling in the presence of an earth like magnetic field thermoremanent magnetization a new map of the magnetic field of mars compiled by using measurements acquired at an 400 km mapping altitude by the mars global surveyor spacecraft is presented here the increased spatial resolution and sensitivity of this map provide new insight into the origin and evolution of the mars crust variations in the crustal magnetic field appear in association with major faults some previously identified in imagery and topography cerberus rupes and valles marineris two parallel great faults are identified in terra meridiani by offset magnetic field contours they appear similar to transform faults that occur in oceanic crust on earth and support the notion that the mars crust formed during an early era of plate tectonics

the terminology of structures in thrust belts abstract a review of structures and geometric relationships recognized in thrust belts is presented a thrust is defined as any contractional fault a corollary being that thrusts must cut up section in their transport direction flats are those portions of a thrust surface which were parallel to an arbitrary datum surface at the time of displacement and ramps are those portions of thrusts which cut across datum surfaces ramps are classified on the basis of their orientation relative to the thrust transport direction and whether they are cut offs in the hangingwall or footwall of the thrust lateral variations in the form of staircase trajectories are joined by oblique or lateral ramps which have a component of strike slip movement an array of thrusts which diverge in their transport direction may form by either of two propagation models these are termed piggy back propagation which is foreland directed and overstep propagation which is opposed to the thrust transport direction an array of thrust surfaces is termed an imbricate stack and should these surfaces anastamose upwards a duplex will result the fault bounded blocks are termed horses a duplex is bounded by a higher roof thrust and a lower floor thrust the intersection of any two thrust planes is termed a branch line thrusts can be classified on the basis of their relationship to asymmetric fold limbs which they cut a further classification arises from whether a particular thrust lies in the hangingwall or footwall of another one the movement of thrust sheets over corrugated surfaces or the local development of thrust structures beneath will fold higher thrust sheets these folds are termed culminations and their limbs are termed culmination walls accommodation of this folding may require movement on surfaces within the hangingwall of the active thrust these accommodation surfaces are termed hangingwall detachments and they need not root down into the active thrust this category of detachment includes dip slip hangingwall drop faults which are developed by differential uplift of duplex roofs and out of the syncline thrusts which develop from overtightened fold hinges back thrusts as well as forming as hangingwall detachments may also form due to layer parallel shortening above a sticking thrust or by rotation of the hangingwall above a ramp

continental fault structure and the shallow earthquake source plate boundaries in continental crust are generally less sharply defined than in the oceans with seismicity spread over broad areas interplate displacements appear to be largely accommodated by networks of major fault zones a simple 2 level model for these important structures accounts for the depth distribution of most continental earthquakes and for the observed range of faulting styles and associated rock deformation textures the model consists of a seismogenic frictional slip regime overlying quasi plastic mylonite belts wherein shearing is largely accommodated aseismically due mainly to the changing response of quartz to deformation with increasing temperature shear resistance increases with depth to a peak value in the vicinity of the frictiona1 quasi plastic transition and then decreases rapidly the depth to which microseismic activity extends appears inversely related to regional heat flow and can be satisfactorily modelled as the frictional quasi plastic transition for different geotherms using laboratory determined flow laws for quartz bearing rocks larger earthquake ruptures m 5 5 tend to nucleate near the base of the seismogenic regime in the region inferred to have the highest shear resistance and concentration of distortional strain energy consideration is also given to the depression of isotherms and seismic activity in regions of thrusting and to the question of the downward continuation of major fault zones through the lithosphere decoupling of the upper crust on flat lying shear zones may accompany higher level dip slip and perhaps in some circumstances strike slip faulting being favoured by above average continental heat flow and a high quartz content in the middle or deep crust the average level of deviatoric stress within the seismogenic regime remains an outstanding problem

koroglu caldera mid west anatolia turkey volcanological and magmatological evolution abstract the koroglu caldera is a result of the eruption of seydiler ignimbrites which have been emplaced in two sequences known as lower seydiler ls and upper seydiler us the koroglu caldera measures 13 km 18 km contains a resurgent dome in the center and produced low aspect ratio ignimbrites which have been transported up to 50 km away from the source the ignimbrites show argillaceous weathering which decreases from the bottom towards the top of the deposits such a transition from ignimbrites to reworked tuffs indicates the development of a lacustrine environment over the ignimbrites spot image analysis shows that tectonic activity continued after the caldera collapse two main trends of tectonic elements ne sw and nw se have been distinguished the latter being the younger a nw se striking fault was used by lamprophyric magmas which were extruded into the post ignimbrite lacustrine deposits the lava flows and dikes trachybasalte trachyandesite also occur along the ring fractures of the caldera the dikes are composed of olivine phlogopite cr diopside salite k feldspar ba feldspar hyalophane the lava flows contain scarce cognate inclusions

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

experimental fracture strain and subsidence patterns over en echelon strike slip faults implications for the structural evolution of pull apart basins abstract claybox experiments show that with progressive left lateral displacement on basal left stepping en echelon strike slip faults an extremely complicated zone of evolving fracture strain and subsidence patterns develops in the overlying clay the fracture pattern is more complex than predicted by theoretical models and consists of a progressively widening array of riedel shears conjugate riedel shears and tension gashes above basal master faults conjugate riedel shears rotate anticlockwise and lengthen forming s shaped fractures riedel shears rotate both anticlockwise and clockwise those that rotate anticlockwise eventually open as tension gashes other tension gashes open where the ends of riedel and conjugate riedel shears link strain contours in the deformed clay show an asymmetrical z shaped pattern over the stepover area between basal en echelon faults in the early stages of displacement strain is distributed penetratively over a progressively broadening zone in later stages of displacement strain is partitioned into a narrow middle zone maximum strain is sustained always in the middle of the sheared zone and increases exponentially with progressive displacement subsidence is accommodated in the stepover area by oblique slip on many riedel and conjugate riedel shears distributed throughout the stepover area subsidence y exhibits a linear relationship with master fault displacement x described by y 0 36 x 1 4 the experimental fracture strain and subsidence patterns in clay over en echelon faults can be used as interpretive and predictive tools with which to constrain interpretations of static field examples especially in pull apart basins on the crustal scale where many similarities with the models exist

late permian paleomagnetic pole from dikes of the tarim craton china we have obtained a late permian paleomagnetic pole from dikes in the tarim craton of china directions of magnetization from 21 mafic and ultramafic dikes at three localities pass a fold test at the 95 confidence level the new paleomagnetic pole lies at lat 66 n long 181 e n 21 k 61 and 95 3 9 on the basis of a comparison with paleomagnetic data from adjacent tectonic units we conclude that 1 the late permian paleolatitude of the tarim craton differs from that of the sino korean craton suggesting that the two cratons were distinct tectonic units in late permian time 2 there was relative motion between the tarim craton and the siberian craton after late permian time and 3 negligible relative motions have occured between different thrust sheets in the keping bachu area of the north western tarim craton

impact of an interbedded viscous decollement on the structural and kinematic coupling in fold and thrust belts insights from analogue modeling abstract fold and thrust belts ftbs can be segmented both across and along strike because of various factors including tectonic and stratigraphic inheritance in this study we investigated along across strike structural interactions in a ftb propagating toward a foreland which displays contrasted lithological sequences a set of analogue models was performed in a compressional box where a single viscous level of varying width was interbedded within a frictional series the tectonic interaction between the viscous and the frictional provinces was tested both along and across strike results indicate that a frictional province influences the along strike tectonic evolution of an adjacent viscous province this influence decreases when the width of the viscous province increases the frictional provinces control the taper structural style obliquity of the structures trend and kinematics of the shallow deformation front of the viscous province results evidence how far a frictional province can impact the deformation of an adjacent viscous province for frictional viscous wedges it appears that the critical taper theory which is generally applied in 2 d should be likely considered in terms of 3 d moreover the kinematics of the deep deformation front shows mutual influences between the adjacent viscous and frictional provinces experimental results are compared to natural examples in the kuqa basin southern tian shan china and the salt range pakistan and give an insight to a better understanding of the dynamics of fold and thrust belts bearing a viscous decollement such as salt

characterizing seismic bright spots in deeply buried ordovician paleokarst strata central tabei uplift tarim basin western china anomalous seismic amplitude bright spots are a common feature in deeply buried 5500 to 6500 m ordovician limestone strata in the central tabei uplift area of the tarim basin in northwest china those anomalies have proven to be useful indicators of reservoir quality the bright spots as seen on seismic data are tied to high gamma ray low velocity zones in wireline logs and correspond to clastic cave sediment fills in the host limestone in core synthetic seismic models confirm this relationship between seismic bright spots and cave sediment fills a seismic traveltime map of the top ordovician unconformity illustrates erosional topography and seismic geomorphologic patterns associated with the unconformity with numerous sinuous fluvial channels and canyons fluvial valleys sinkholes and tower karsts and hills a mature surface drainage system interacted with a near surface karst system and allowed terrigenous sediments to enter an underground cave system karst related bright spots probably correspo

structural features of northern tarim basin implications for regional tectonics and petroleum traps the rhombus shaped tarim basin in northwestern china is controlled mainly by two left lateral strike slip systems the northeast trending altun fault zone along its southeastern side and the northeast trending aheqi fault zone along its northwestern side in this paper we discuss the northern tarim basin s structural features which include three main tectonic units the kalpin uplift the kuqa depression and the north tarim uplift along the northern margin of the tarim basin structural mapping in the kalpin uplift shows that a series of imbricated thrust sheets have been overprinted by strike slip faulting the amount of strike slip displacement is estimated to be 148 km by restoration of strike slip structures in the uplift the kuqa depression is a mesozoic cenozoic foredeep depression with well developed flat ramp structures and fault related folds the baicheng basin a quaternary pull apart basin developed at the center of the kuqa depression subsurface structures in the north tarim uplift can be divided into the mesozoic cenozoic and the paleozoic lithotectonic sequences in seismic profiles the paleozoic litho tectonic sequence exhibits the interference of earlier left lateral and later right lateral strike slip structures many normal faults in the mesozoic cenozoic litho tectonic sequence form the negative flower structures in the north tarim uplift these structures commonly directly overlie the positive flower structures in the paleozoic litho tectonic sequence the interference regions of the northwest trending and northeast trending folds in the paleozoic tectonic sequence have been identified to have the best trap structures our structural analysis indicates that the tarim basin is a transpressional foreland basin rejuvenated during the cenozoic

wavelet characterization of external magnetic sources as observed by champ satellite evidence for unmodelled signals in geomagnetic field models praveen kunagu 1 2 georgios balasis 3 vincent lesur 1 e chandrasekhar2 and c papadimitriou3 1helmholtz centre potsdam gfz german research centre for geosciences germany 2department of earth sciences indian institute of technology bombay powai mumbai 400076 india email esekhar iitb ac in 3institute for astronomy astrophysics space applications and remote sensing national observatory of athens greece

a sub salt structural model of the kelasu structure in the kuqa foreland basin northwest china abstract the kuqa foreland basin adjacent to the south tianshan mountains is a major hydrocarbon accumulation basin in western china the kelasu structural belt is the focus for hydrocarbon exploration in the basin due to the presence of ramp related anticline traps and a thick salt seal the model of the kelasu sub salt structure is still contentious because of the structural complexity and poor seismic imaging below the salt layer the area depth strain ads method is applied to the southern part of the kelasu fault a regional fault that cuts basement rocks the ads results are consistent with the seismic data which indicate that both thin skinned thrusting and basement involved deformation occur within the kelasu structure with the kelasu fault acting as the boundary between the two regions of contrasting deformation the ads results also suggest that the depth of the lower detachment of the thin skinned thrust belt is 9 5 10 km which may correspond to the base of the triassic the kelasu structure has undergone approximately 8 15 10 76 km of horizontal shortening in the east and 16 34 km in the west of the structure

the effect of overburden thickness on deformation mechanisms in the keping fold thrust belt southwestern chinese tian shan mountains insights from analogue modeling abstract the structural evolution of the keping fold thrust belt in the south chinese tian shan nw china is poorly understood here we present the results of a series of scaled sandbox models based on the structural architecture of the keping fold thrust belt in our investigation of the effect of overburden thickness on deformation mechanisms in fold thrust belts these models simulated the evolution of the keping fold thrust belt where the western segment was shortened with a thicker overburden relative to the eastern segment model results confirm that fewer thrust faults with wider spacing develop in thicker cover units whereas more thrust faults with narrower spacing develop in thinner cover units transfer zones also form as a result of faster and farther propagation in a segment with thicker overburden consistent with the prediction of the critical taper theory our modeling further shows that due to the episodic accretion of thrust wedges and non simultaneous formation of thrust faults the deformation front may locally propagate farther in the thinner overburden alternatively there may not be so much difference between two parts of sand layers with different thicknesses an observation that is inconsistent with the theoretical prediction the similarities between the model and real geological observations suggest that the variations in the overburden thicknesses across the piqiang fault transfer zone strongly influenced the development of the structural architecture of the keping fold thrust belt they further indicate that the growth of fold thrust belts in nature is episodic and that the propagation of deformation front cannot be simply predicted by the critical taper theory the overburden thickness variations across the piqiang fault transfer zone were produced by high angle reverse faulting along the pre existing piqiang selibuya fault during the late pliocene and associated crustal uplift and erosion of the hanging wall strata

high k volcanism in the afyon region western turkey from si oversaturated to si undersaturated volcanism volcanic rocks of the afyon province eastern part of western anatolia make up a multistage potassic and ultrapotassic alkaline series dated from 14 to 12 ma the early stage si oversaturated volcanic rocks around the afyon city and further southward are trachyandesitic volcanic activity 14 23 0 09 ma late stage si undersaturated volcanism in the southernmost part of the afyon volcanic province took place in three episodes inferred from their stratigraphic relationships and ages melilite leucitites 11 50 0 03 ma spotted trachyandesites tephryphonolites and lamproites 11 91 0 13 ma formed in the first episode trachyandesites in the second episode and finally phonotephrites phonolite basaltic trachyandesites and nosean bearing trachyandesites during the last episode the parameter q normative q ne lc kls ol of western anatolia volcanism clearly decreased southward with time becoming zero in the time interval 10 15 ma the magmatism experienced a sudden change in the extent of si saturation after 14 ma during late stage volcanic activity of afyon volcanic province at around 12 ma though there was some coexistence of si oversaturated and si undersaturated magmas during the whole life of afyon volcanic province

diverse pliocene quaternary tectonics in a transform environment san francisco bay region california the san francisco bay region occupies part of the diffuse transform boundary zone between the pacific and north american plates although dextral strike slip faulting is dominant the plate motion is expressed in a variety of ways some strike slip faults are parallel with the plate boundary but some are slightly oblique the major strike slip faults are zones in which an interplay occurs between strands some of which are en echelon this interplay may be responsible for some apparent pull apart basins and presumed normal faults along the calaveras fault zone in extensive areas between strike slip fault zones there are many compressional structures folds and reverse faults that are pliocene quaternary in age hence largely coeval with the strike slip faults some of the compressional structures are oblique to and others are parallel with the major strike slip faults we have divided the san francisco bay region into domains on the basis of the types orientations and relationships of structures or in one case lack of strong deformation each domain has responded in its own way to the regional northwest southeast dextral shear imposed by the relative plate motion in an attempt to understand the origin of various structures and the interrelationships among them we compared established models with our observations some observed geometric relationships agree quite well with classical coulomb anderson and simple shear models but others require further explanation models based on fault interaction seem to apply to certain cases for example the east bay hills domain which is between the left stepping calaveras and hayward rodgers creek fault zones is under compression resulting from interaction between the two strike slip zones

coal characteristics and biomarker investigations of dombayova coals of late miocene pliocene age afyonkarahisar turkey abstract in dombayova graben dinar afyonkarahisar western turkey a 203 m thick coal bearing zone of late miocene to pliocene age was recently drilled the zone hosts several coal beds with a total thickness of 46 m coal samples from the dombayova field were studied by means of standard proximate ultimate petrological analyses micro ftir spectroscopy and rock eval pyrolysis and organic geochemical analyses coal proximate analyses and the presence of carbonate minerals and fossil shell fragments point to alkaline surface waters of changing ph values due to fluctuations of the water level in the paleomire and or ca rich water influx low sulfur contents argue for sulfate limitation of bacterial sulfate reduction petrographic observations reveal that the coal is dominantly composed of weakly altered wood fragments and roots the mean random reflectance values of ulminite 0 33 ro indicate lignite rank of the coal the micro ftir data of macerals of huminite group indicate higher contributions of aliphatic hydrogen in textinite compared to more aromatic levigelinite the semi quantitative differences in the ratios of selected functional groups suggest that aromaticity and the extent of oxidation are higher in levigelinite aliphatic chains are longest in textinite and ulminite and shortest in texto ulminite and levigelinite we interpret this difference to point to a different origin of levigelinite probably from colloidal humic solutions that were gelified during diagenesis the concentrations of n alkanes and their distribution patterns provide evidence for higher terrestrial plants as the dominant source of organic matter decreasing pristane phytane ratios with depth are interpreted to reflect more reducing conditions during peat formation due to higher ground water level the absence of diasterenes is most probably caused by low clay mineral contents and is consistent with the presence of alkaline waters in the paleomire the presence of terpenoid hydrocarbons in the lignite indicates a major contribution of angiosperms to peat formation the positive relationship between the concentrations of perylene and lupane type triterpenoids suggests an increasing abundances of wood degrading fungi in the peat forming vegetation characterized by a high density of betulaceae

substratum transverse faults in kuqa foreland basin northwest china and their significance in petroleum geology abstract the importance of transverse faults in basin evolution and petroleum geology has been often emphasized however the transverse faults in the kuqa foreland basin the most important gas producing area in china have rarely been studied interpreted seismic sections and earthquake focal mechanism solutions as well as other geological and geophysical data allow us to identify a few widely spaced approximately ns trending transverse strike slip faults separating major structural units and to clarify the geometry and kinematics of these transverse faults hidden below thrust faults in the kuqa foreland basin two major structural domains can be distinguished transverse faults in the northern kuqa foreland basin are mainly nne trending sinistral indicating clockwise rotation of fault bounded blocks in contrast the predominant nw trending dextral faults in the southern kuqa foreland basin imply counterclockwise rotation of fault bounded blocks we propose a tectonic model in which crustal blocks are bounded by strike slip faults in a zone of simple shear rotation about vertical axis the strike slip faulting and thrust faulting in the kuqa foreland basin suggest that some of the convergence between south tianshan and tarim blocks may have been accommodated not only by obvious crustal shortening and thickening along thrust faults but also by rotation and possible lateral movement of the crust along transverse faults controlled by the remote collision of indian block with eurasian block since the miocene these reactivated substratum faults which may inherit from paleozoic deformation control various elements relevant to gas accumulation in the kuqa foreland basin which should expect to be paid more attention in the future these elements include maturity of tertiary and jurassic source rocks a difference in the regional cap of kumugelimu salt beds from east to west reservoir bed properties gas migration channels and traps formation in addition the strike slip faulting of the transverse faults may affect deformation of the sedimentary cover including making the western qiulitag structural belt to form an arcuated structure curved to the ssw

structural characterization of intracratonic strike slip faults in the central tarim basin the strike slip fault systems in the central tarim basin china afford an exceptional opportunity to document the structural characteristics and evolution process of small displacement intracratonic strike slip faults using three dimensional seismic reflection data these strike slip faults display subvertical segments at depth and en echelon normal fault zones where relatively shallow fault segmentation and flower structures can be commonly observed in plan view and cross section view respectively consistent with the notion that segment coalescence is the fundamental process for fault evolution the mean segment length of representative strike slip faults examined in this study is positively correlated to the measured fault offset the width of the en echelon normal fault zone is positively correlated with the estimated maximum overburden thickness the integrated data sets suggest that the evolution of the conjugate fault array followed a sequential evolution process instead of forming simultaneously the switch in slip direction of the master fault of the conjugate fault array is attributed to the change of stress orientation regarding individual strike slip faults increase in displacement induces the formation of faults with lower fault array angles linking initially formed en echelon normal faults in cross sections throughgoing fault surfaces can also form connecting the lower subvertical fault segment and the upper en echelon normal faults the presented data sets and evolution models established in this study can be used as tools to better predict the structural attributes of subsurface strike slip fault systems with important consequences for reservoir formation and hydrocarbon accumulation in the tarim basin in particular and in ancient marine basins in general

global basin classification system a proposed system classifies sedimentary basins worldwide into specific as well as general categories the geologic history of each basin may be subdivided into cycles using three parameters basin forming tectonics depositional sequences and basin modifying tectonics sedimentary basins may be simple with one or two tectonic sedimentary cycles or they may be complex polyhistory basins with many different cycles and events there are eight simple cycle types in this classification which cover continental continental margin and oceanic areas the eight basic cycle types their depositional fills and tectonic modifiers have been given letter and number symbols so that the specific geologic history of each basin may be written as a formula these formulas may then e compared and similarities or differences between basins noted

the influence of the water saturation on the strength of volcanic tuffs used as building stones moisture content is one of the most important factors influencing the strength of building stones ayazini and seydiler afyonkarahisar turkey tuffs were investigated with the goal to determine the influence of the water on their strength mercury porosimetry was used to determine the pore size distribution ayazini tuffs have pore sizes ranging from about 200 000 to 10 nm and seydiler tuffs ranging from about 7000 to 10 nm the tuff samples are immersed in water with different time periods of 1 6 24 and 48 h the following physico mechanical properties were measured for all the samples both in dry and saturated condition compressive strength and flexural strength test results were indicated by simple regression analysis good correlations were found between physico mechanical properties with dry and saturated tuff samples the results had shown their mechanical strength decreases in wet conditions for dry samples tested had 22 21 mpa uniaxial compression strength while 1 h immersed samples had 15 11 mpa which indicates a decrease of 31 96 after the 48 h water immersion time period the value of compression strength decreases by 43 99 and becomes 12 44 mpa

fault system impact on paleokarst distribution in the ordovician yingshan formation in the central tarim basin northwest china abstract the paleokarst unconformity at the top of the ordovician yingshan formation in the central tarim basin was exposed to air for at least 10 ma providing favorable conditions for the later formation of high quality reservoirs during the karstification process the fault system plays an important role in controlling the development of paleokarst this study characterized the fault system through the paleokarst features on the northern slope of the tazhong high and examined in detail the impacts of the fault system on paleokarst distribution formation micro imager logs and seismic curvature change rate were used for characterizing the fault system in different scales the results revealed three sets of faults in this region cross cutting relationships unconformities and relation between faults and karstification indicate mid to late ordovician thrust faults silurian devonian strike slip faults and permian tension faults bright spots in seismic records calibrated by formation micro imager logs were used for indicating paleokarst features and different depth distributions respectively furthermore the study employed spectral decomposition technique to characterize the morphology of paleocave complexes in detail the results show the mid late ordovician thrust faults heavily impacted the distribution of paleokarst mainly distributed along master and secondary thrust faults in shallow areas as well as along master basement involved thrust faults in deep strata and along the most pronounced area of paleokarst tazhong no 10 fault zone bounded by back thrusts the data provides new forecasting information for deep hydrocarbon exploration in paleokarst related reservoirs of the yingshan formation