evolution of the great river systems of southern asia during the cenozoic india asia collision rivers draining north from the pamir syntaxis abstract during uplift of the tibetan plateau and surrounding ranges tectonic processes have interacted with climatic change and with local random effects such as landslides to determine the development of the major river systems of asia rivers draining northward from the pamir syntaxis have three distinctive patterns that are controlled by different tectonic and climatic regimes west of the pamir the rivers have moderate but irregular gradients and drain northwards to disappear into arid depressions relatively steady uplift of the hindu kush in northern afghanistan allowed rivers to cut across the rising ranges modified by the shear along the harirud fault zone local faulting and by increasing rain shadow effects from the rising makran in the transition to the pamir the rivers have steeper but more even gradients suggesting more even flow and downcutting during uplift possibly related to larger glacial sources in the central pamir only one antecedent river the pyandzh appears to have kept its northward course with compression and uplift of the indenter and its course strangely corresponds with a major geophysical boundary a distorted subducted slab but not a geological boundary the other rivers are subsequent rivers developed along deformation fronts during development and northward displacements of the pamir structural units the above areas have sources north of the cretaceous karakorum south pamir andean margin on the eastern flank of the pamir in the kunlun and northern tibetan plateau the rivers rise similarly north of the cretaceous andean margin of southern tibet but then flow with low gradients across the plateau before cutting and plunging steeply down across the kunlun to disappear into the arid tarim these steep profiles are the result of late neogene uplift of the northern tibetan plateau and kunlun possibly modified by glacial diversion and river capture the drainage history of the pamir indenter can be reconstructed by restoring the gross movements of the plates and the tectonic displacements uplift and erosion of individual tectonic units most important changes in drainage took place in the last 10 million years late miocene to quaternary times as the pamir syntaxis developed

what controlled mid late miocene long term aridification in central asia global cooling or tibetan plateau uplift a review abstract debate continues over whether global cooling or uplift of the tibetan plateau provided the first order driver for the aridification moisture levels of central asia throughout the mid late miocene between about 17 and 5 ma this review attempts to throw new light on the relations between the aridification and these two key factors this paper examines the evolution of miocene climate both moisture and temperature within five separate regions of eurasia to help understand the large scale controls of long term moisture in central asia the five regions include 1 europe 2 high latitude asia 3 the east asian monsoon region 4 the south asian monsoon region and 5 central asia itself because moisture reaching central asia has to firstly cross at least one of the other four regions temperature proxy data compiled from these five regions correlate with ocean temperatures from the global deep sea oxygen isotope records furthermore compiled moisture proxy data from the four regions surrounding central asia co vary and correlate with each other this can be explained by positive feedbacks between drying and cooling and supports the assumption that global cooling provides a dominant driving factor for the drying of eurasia global cooling reduces the amount of water vapor held in the atmosphere and thereby can cause terrestrial drying however in central asia the moisture evolution shows less similarity with its surroundings the uplift of the tibetan plateau including the tianshan mountains could provide a possible explanation for this difference the changing topography resulting from uplift events over time and space strongly influenced the moisture patterns in central asia during miocene times future research on the spatial timing and amplitude of tibetan plateau uplift should be useful to understand the moisture processes in central asia during the miocene

the eastern termination of the zagros fold and thrust belt iran structures evolution and relationships between salt plugs folding and faulting 1 the zagros mountains result from the ongoing collision between the arabian and central iran plates the main features of the eastern zagros are 1 numerous emerged or buried salt diapirs made up of late precambrian hormuz salt and 2 the irregular along strike shape of the collision related detachment folds with frequent bending to understand this layout four geological cross sections have been constructed from the persian gulf foreland basin to the inner part of the zagros fold and thrust belt shortening in the deformed parts of the sections is less than 10 and is mainly accommodated by detachment folding we show that late cenozoic folding occurred in a region that was already punctuated by salt domes and diapirs in fact almost continuous halokinesis developed since the earlier paleozoic i e just short time after the deposition of the hormuz salt and continued up to the present these preexisting salt structures and their relevant local thickening strongly influenced both the localization and the direction of folds

did the growth of tibetan topography control the locus and evolution of tien shan mountain building the tien shan in central asia are the pre eminent example of intraplate mountain building and are typically considered an indirect result of the india eurasia collision via the northward indentation of the relatively strong precambrian lithosphere of the tarim plate into the relatively weak paleozoic lithosphere of the tien shan region this hypothesis fails to fully explain the concentration of tien shan mountain building along a tibet parallel axis located 500 700 km from tibet and also fails to explain the close synchronization of tien shan mountain building events with mountain building in tibet i suggest that bending stresses from lithospheric flexure in central asia exerted a critical influence on the locus and evolution of the tien shan models of paleogene to middle miocene flexure indicate that the growth of northeast tibet may have superimposed a strong bending stress field on the regional stress field the resultant stress field is characterized by strong topography normal tensile stress in the tarim basin and an 15 increase in compressive stress in the vicinity of the tien shan this stress field severely reduces the likelihood of mountain building south of the tien shan and increases the likelihood of mountain building within the tien shan this result suggests that the generation of bending stresses from lithospheric flexure is a viable and important mechanism for the propagation of stress and hence deformation into continental interiors

origin and development of artemisia asteraceae in asia and its implications for the uplift history of the tibetan plateau a review abstract the spatial and temporal evolution of artemisia and its relationship with the tibetan plateau tp uplift are examined by summarizing pollen data from 122 sites across china the pollen morphological data reveal that artemisia may have originated from the arid semiarid middle latitudes of asia in the late eocene and spread west and east in the oligocene as the result of early uplift of the tibetan plateau and the global cooling during the miocene artemisia reached the southeastern part of the tp and became common in the western tp due to the high elevation in these regions at the same time the asian monsoon prevented the spread of artemisia to the southern part of the tp since the pliocene especially in the pleistocene artemisia distribution was very similar to its current distribution which indicates that the topography of the tp and the paleoenvironmental conditions in the east asia became more like today thus the cenozoic origin and evolution of artemisia in the asia was strongly influenced by the uplift of the tp global cooling as well as monsoon development

the uplift history of the haiyuan liupan shan region northeast of the present tibetan plateau integrated constraint from stratigraphy and thermochronology abstractthe haiyuan liupan shan delimits the northeastern margin of the tibetan plateau we present the integrated results of new stratigraphic investigations apatite fission track analyses and related thermal history modeling tied to the structural fabric of this region these constraints provide insight into the timing of northward propagation of the plateau with 1 local relief creation and enhanced erosion in the latest jurassic to earliest cretaceous representing the local element of a complex regional far field deformation response to the lhasa qiangtang collision with the south asian margin 2 evidence for likely late cretaceous exhumation but this is uncertain given the regional sedimentary gap that exists across this interval 3 eocene relief generation as a first likely response to far field effects of the india asia collision and related to wider regional events recognized in this part of northwestern china and 4 the latest deformation episode propagating strongly into the haiyuan

central zagros fold thrust belt iran new insights from seismic data field observation and sandbox modeling 1 we present five generalized cross sections across the central zagros fold and thrust belt iran these sections show that the fold geometry varies significantly both horizontally and vertically the style is closely related to the changes in the mechanical behavior of the lithostratigraphic horizons and in particular to the presence of intermediate decollements within the sedimentary pile restoration of the sections shows amounts of shortening of the same order from one section to the other however it appears to be unequally distributed suggesting variations in basal decollement shear strength analogue modeling has been performed to systematically investigate the effect of an intermediate decollement level at different depths on the style of folding the models demonstrate that the position of intermediate decollements is an important factor controlling both structural style and fold wavelength models with shallow intermediate decollement show regularly and widely spaced anticlines in these models the fold wavelength depends directly on the thickness of the dominant competent layer and short wavelength superficial structures mask broad anticlines at depth models with deep intermediate decollement are characterized by the rapid propagation of deformation with small rate of shortening along this decollement influencing localization of forthcoming anticlines in the upper levels such propagation favors the development of duplexes and multiwavelength folds on this basis fold kinematics in central zagros is discussed using the variation of structural style along different folds as an indicator of the sequence of deformation detachment folding is the main folding style at least for the initial stages of deformation and thrust faults developed only at later stages some of these faults branched on decollement levels express the progression of folding whereas others are linked to late basement faults cutting through early structures in general the decollement levels are activated sequentially from deeper horizons to shallower ones however in one case gachsaran decollement a shallow decollement is activated during the early stages of folding and then abandoned during the subsequent evolution

mechanics of fold and thrust belts and accretionary wedges cohesive coulomb theory a critically tapered fold and thrust belt or submarine accretionary wedge is one that is on the verge of coulomb failure everywhere including its base where frictional sliding along a decollement is assumed to be occurring cohesion within a wedge can add significantly to the overall strength near the toe the effect of this is to decrease the near toe taper leading to a critical topographic profile that is concave upward if the decollement is planar we obtain an approximate self consistent solution for the state of stress within a thin skinned cohesive critical coulomb wedge and determine the relationship between the wedge taper and its strength and basal friction the theory is then applied to the presently deforming fold and thrust belt of western taiwan fitting of theoretical critical wedge shapes to topographic profiles and measurements of the step up angles of thrust faults from the basal decollement are used to constrain the taiwan wedge strength parameters an attractive assertion fully consistent with all the observations is that the mechanics of fold and thrust belts and accretionary wedges is governed by normal frictional and fracture strengths of rocks measured in the laboratory in particular if byerlee s law b 0 85 is adopted as the coefficient of sliding friction on the base we find a coefficient of internal friction 0 9 1 0 in the wedge and a wedge cohesion so 5 20 mpa other solutions having strengths and ambient stresses up to 4 times lower than this can also however satisfy the data

epicenter distribution and magnitude of earthquakes in fold thrust belts insights from sandbox models scaled analogue models are used to illustratethe eect of basal friction and erosion on fault activity andhence on epicentre distribution and magnitude of earth quakes in the sedimentary cover of active fold thrust belts model results suggest that in fold thrust belts shortenedabove low friction ductile decollements rock salt or over pressured mudstone low to moderate magnitude earth quakes mw 5 3 5 6 distributed over a wide area occuralong several long lived thrust faults conversely in areasshortened above high friction decollements large magnitudeearthquakes mw 6 6 6 8 distributed over a narrowzone are likely to occur along few short lived thrust ramps calculated magnitude of earthquakes from models and theirdistribution are in agreement with recorded earthquake pat tern from the zagros mountain belt which is partially short ened above a ductile decollement of hormuz salt formation model results also showed that erosion reactivates older in active thrusts and promotes formation of out of sequencethrusts

centrifuged models of gulf of mexico profiles abstract physical models dynamically scaled in a centrifuge are used to explore the importance of slope progradation in driving internal salt structures much further horizontally than they rise large increments of ductile plastic overburden added at normal gravity values simulated primary clastic sedimentary progradation of a clastic slope over a layer of buoyant fluid simulating salt during load increments at a nominal 800 g in a centrifuge this ductile topographic slope spread over the ductile decollement except for down to basin growth faults all the structures considered to be distinctive in the northern gulf of mexico are simulated in the models that are scaled such that 1 mm and 60 s in the model correspond to 1 1 5 km and 2 6 ma in the prototype ratios of the rate of advance to the rate of rise of the shelf break compared with the rate of advance and increase in relief of salt structures control how much of the deep autochthonous salt is squeezed ahead of the advancing shelf and the paths this salt takes to shallow structural levels the few three dimensional diapiric stocks which developed from many two dimensional mullions in the models spread stock canopies which advanced huge distances before some became tongue canopies by climbing over clastic sediments already aggraded in front of them the models emphasize the significance of ductile spreading of the clastic sediments now being discerned by backstripping

tectonics of western tibet between the tarim and the indus a tarim to indus traverse provides insight into the tectonics of western tibet the kunlun was the site of a mid paleozoic collision at least three phases of post paleozoic accretion have thickened the blanket of sediments that covers western tibet sizeable parts of western qiangtang have remained stable however since the mid mesozoic since the neogene deformation and volcanism have been localized near the edges of the plateau strike slip motion along the karakorum and altyn tagh faults has been coeval with overthrusting in the himalayas and kunlun such slip partitioning and the volcanism appear to result simply from northward subduction of india and southward subduction of the tarim as tibet is extruded eastwards by india s penetration into asia

indentation of the pamirs with respect to the northern margin of tibet constraints from the tarim basin sedimentary record the pamirs represent the indented westward continuation of the northern margin of the tibetan plateau dividing the tarim and tajik basins their evolution may be a key factor influencing aridification of the asian interior yet the tectonics of the pamir salient are poorly understood we present a provenance study of the aertashi section a paleogene to late neogene clastic succession deposited in the tarim basin to the north of the nw margin of tibet the west kunlun and to the east of the pamirs our detrital zircon u pb ages coupled with zircon fission track bulk rock sm nd and petrography data document changes in contributing source terranes during the oligocene to miocene which can be correlated to regional tectonics we propose a model for the evolution of the pamir and west kunlun wkl in which the wkl formed topography since at least 200 ma by 25 ma movement along the pamir bounding faults such as the kashgar yecheng transfer system had commenced marking the onset of pamir indentation into the tarim tajik basin this is coincident with basinward expansion of the northern wkl margin which changed the palaeodrainage pattern within the kunlun progressively cutting off the more southerly wkl sources from the tarim basin an abrupt change in the provenance and facies of sediments at aertashi has a maximum age of 14 ma this change records when the pamir indenter had propagated sufficiently far north that the north pamir was now located proximal to the aertashi region

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 middle miocene tectonic uplift of the northwestern part of the qinghai tibetan plateau evidenced by geochemical and mineralogical records in the western tarim basin the tarim basin in western china has been receiving continuous marine to lacustrine deposits during the cenozoic as a foreland basin of the qinghai tibetan plateau qtp clay mineralogy and geochemical proxy data from these sedimentary archives can shed light on climate and tectonic trends here we report on an abrupt mineralogical and weathering shift at 17 ma 1 myr in the miocene qimugan section in the northwestern part of the qinghai tibetan plateau the rapid shift involves decreasing trends of chemical weathering indices rb sr and ba sr ratios and of minor and immobile elements with respect to upper crust composition as well as increasing trends of na al and na ti ratios smectite chlorite and calcite contents we ascribe these trends to changing source rocks due to uplift of the northern part of the qtp leading to exposures of younger intrusive bodies and older gneisses schists and carbonate rich rocks these uplifts potentially caused regional aridification reducing chemical weathering the dating is indirect via magnetostratigraphically dated ostracod biostratigraphy and detrital zircon chronology and currently not good enough to compare the shift accurately in time with the onset of the global middle miocene climate optimum mmco at 16 5 ma nevertheless regional tectonics seem to have dominated over global climate as the warmer mmco is expected to have increased weathering indices and decreased na al and na ti rather than the observed reverse trends

computerized x ray tomography analysis of sandbox models examples of thin skinned thrust systems computerized x ray tomography applied to analog sandbox experiments performed in a normal gravity field makes possible the analysis of the kinematic evolution as well as the three dimensional geometry of models that simulate tectonic deformations most of the plastic or viscous analog materials generally used in a normal gravity field for such models have x ray attenuations compatible with medical scanner images models using soft cohesionless granular materials were studied faults in granular materials corresponding to dilatant zones with lower by 30 50 x ray attenuation are thus clearly visible in the tomography images kinematic analysis was done on imbricate thrust propagation in materials with an internal friction angle of 30 thrust propagation is controlled mainly by a triangular pop up structure resulting from the nucleation of two conjugate thrusts at the basal decollement the pop up structure is created immediately in front of the previous thrust three dimensional geometry analysis was tested on lateral ramps parallel to the transport direction lateral ramps were induced by changing the frictional boundary conditions at the bottom of the model though the lateral ramps strike almost parallel to the transport direction their dip angle is comparable to the dip angle of frontal ramps

commencing uplift of the liupan shan since 9 5 ma evidences from the sikouzi section at its east side abstract the cenozoic evolution of the liupan shan situated at the northeast of the tibetan plateau will provide constraints to test the models and mechanisms of the evolution of the plateau in this contribution the sikouzi section at the east of the liupan shan has been selected to study liupan shan s uplift history at around 9 5 ma constrained by the magnetostratigraphy the sediment and depositing architecture characteristics obviously changed synchronously flow direction changed from e w to w e and accumulation rate increased to more than double all these evidences suggest that the liupan shan initiated uplifting at around 9 5 ma subsequently a stage of intense uplift happened during 8 2 7 3 ma indicated by the apatite fission track aft data across the liupan shan regional comparison indicates that this stage of uplift is not only with local but also regional significance the miocene uplift of the tibetan plateau triggered the intensification of the east asian monsoon and asian intercontinental aridity which has been implied by the pollen results of the sikouzi section

late eocene sea retreat from the tarim basin west china and concomitant asian paleoenvironmental change the paleogene sediments of the southwest tarim basin along the west kunlun shan in western china include the remnants of the easternmost extent of a large epicontinental sea this shallow sea once extended across the eurasian continent before it retreated westward and eventually separated as the paratethys sea climate modeling results suggest that this sea retreat is an equally important forcing mechanism as the tibetan plateau uplift in the aridification of the asian continental interior and the intensification of the asian monsoon system the age and paleogeography of the retreat are poorly constrained hindering the understanding of its cause and paleoenvironmental impacts this study reports litho and biostratigraphic results from two sections recording the last major regression out of the tarim basin that is expressed by a regional transition from marine clastics and limestones to continental red beds rich micro and macrofossil assemblages including benthic foraminifera ostracods bivalves calcareous nannofossils and organic walled dinoflagellate cysts dinocysts indicate a shallow proximal and marine environment strong similarity to assemblages known from central asia and europe confirms that surface ocean connections extended across eurasia from the tarim basin to the western tethys during the latest eocene moreover the recovered fossil associations date the last marine sediments as earliest priabonian in age 37 ma overlap between dinoflagellate mps interval zone and calcareous nannofossil zone cp 14 the retreat of the sea from the tarim basin is time equivalent with the sea level lowstand at the bartonian priabonian boundary but pre dates both the oligocene miocene regional uplift of the pamir mountains and kunlun shan and the major eustatic sea level falls of the eocene oligocene transition 34 ma and mid oligocene 30 ma which are usually held responsible for the sea retreat furthermore a concomitant and significant aridification step occurs at 36 6 ma top of chron c17n 1n as recorded by regional sedimentary records of the xining basin along the northeastern tibetan plateau suggesting that the tarim sea served as a significant moisture contributor for the asian interior

geometry and kinematic evolution of the hotan tiklik segment of the western kunlun thrust belt constrained by structural analyses and apatite fission track thermochronology abstractthe western kunlun thrust belt defines the boundary between the stable tarim basin in the north and the intensely deformed cenozoic tibetan plateau in the south because of its important tectonic position understanding its tectonic evolution should have important implications for propagation of deformation from tibet to its neighboring cratonal regions during india eurasia convergence we here present new structural analyses based on field investigations and seismic reflection profiles across the hotan tiklik segment of the western kunlun thrust belt the results indicate that the structural section crosses two major thrust zones the tiklik zone in the hinterland to the south and the hotan zone in the foreland to the north within these the hotan thrust zone is thin skinned with its deformation characterized by fault bend folding and fault slipping along detachment layers whereas the tiklik thrust zone involves basement with its deformation driven by the currently steeply dipping tiklik faul

origin of chert in lower silurian longmaxi formation implications for tectonic evolution of yangtze block south china abstract upper ordovician katian to lower silurian rhuddanian strata in the middle upper yangtze block south china contain extensive chert beds although the origin of microcrystalline silica in these cherts is largely unknown in this study the mineralogy and structure of chert as well as major trace and rare earth elements are used to determine the origin of microcrystalline silica in 29 chert samples from longmaxi formation rhuddanian in baizitian outcrop west of kangdian uplift ku results show that 21 of the 29 chert samples have a biogenic origin 2 indicate a hydrothermal origin and 6 show a mixed origin cherts from baizitian outcrop are compared to contemporaneous cherts deposited east of ku cherts both east and west of ku are mainly biogenic in origin which is attributed to high productivity in the paleo seaway hydrothermal microcrystalline silica is relatively uncommon in the longmaxi formation across the middle upper yangtze block and only occurs in baizitian outcrop terrigenous influx contributed to chert accumulation both east and west of ku however cherts east of ku received much more clastic material than those in baizitian outcrop a comparison of chert composition and geochemistry to geological reconstructions of the middle upper yangtze block reveal that accumulation of hydrothermal chert is closely linked to tectonic evolution during the early silurian the middle upper yangtze block was in a compressional tectonic regime with limited heat supply and hence low hydrothermal circulation this is manifested in the paucity of hydrothermal microcrystalline silica in cherts east of ku in contrast hydrothermal microcrystalline silica in cherts west of ku is interpreted to have formed in an extensional tectonic regime with sufficient heat supply this research demonstrates that chert source is in part tectonic controlled and chert geochemistry can be used in reconstructing paleoenvironments

variation of structural style and basin evolution in the central zagros izeh zone and dezful embayment iran abstract structural style and its relationship to sedimentary facies and the evolution of sedimentary depocenters since late cretaceous times have been studied on the basis of one regional balanced transect and several updated isopach maps in the izeh zone and the dezful embayment central zagros this study relies on fieldwork data existing geological maps seismic data and well information a new structural classification for part of the zagros sedimentary cover is presented to highlight the different mechanical behavior of the formations in the stratigraphic column it shows the existence of several local decollement levels activated during folding these decollement levels separate lithotectonic units which accommodate shortening in different ways the lower paleozoic is the basal decollement level throughout the studied area triassic evaporites albian shales eocene marls and miocene evaporites can act as intermediate decollement levels and present variable facies in the central zagros lateral facies and thickness variations the sedimentary overburden and the close relationship with inherited fault patterns influenced the wavelength amplitude and style of folding in the study area furthermore surface structures do not necessarily coincide with deeper objectives where these disharmonic levels are involved in folding the evolution of sedimentary depocenters from the late cretaceous obduction episode until early miocene collision is described based on updated isopach maps and tectonic subsidence curves this analysis shows continuous compression and movements along n s and nw se trending faults in the zagros basement which predate the neogene zagros folding and influence sedimentation history it also indicates a southwestward migration of the depocenters through time in addition to the basement involvement below some folds during the zagros orogeny

tectonics of the zagros orogenic belt of iran new data and interpretations abstract the zagros orogenic belt of iran is the result of the opening and closure of the neo tethys oceanic realm and consists from northeast to southwest of three parallel tectonic subdivisions 1 1 the urumieh dokhtar magmatic assemblage 2 2 the sanandaj sirjan zone and 3 3 the zagros simply folded belt recent detailed and reconnaissance mapping and stratigraphie structural analyses in various parts of the belt indicate that the tectonics of the sanandaj sirjan zone is dominated by either large scale composite duplex structures or low and high angle ne dipping imbricate systems these thrust systems have transported numerous horses and sheets nappes of metamorphosed and non metamorphosed phanerozoic rocks for tens or possibly hundreds of kilometers stratigraphic evidence and synorogenic conglomerates indicate that thrusting was initiated in the late cretaceous and has continued episodically since that time shear sense indicators in various parts of the zone reveal a ne sw direction of transport thrust systems generated in each episode are superimposed upon the previous structures cutting across and displacing them and producing complicated stacks of thrust sheets southwestward transport and stacking of the thrust sheets has resulted in an increase of about 10 15 km in the thickness of the continental crust in the southwestern part of this zone the so called z main zagros thrust which has been traditionally considered as the boundary between the sanandaj sirjan zone and the zagros simply folded belt is by no means a single high angle reverse fault nor is it a narrow zone of crushed rocks but a series of low angle thrusts locally cut by normal faults these thrusts are indistinguishable from those mapped in the sanandaj sirjan zone and are geometrically part of the sanandaj sirjan zone structures there is no single thrust among them that can be singled out and referred to as the main one the boundary of the sanandaj sirjan zone with the urumieh dokhtar magmatic assemblage to the northeast is characterized by a series of structural depressions formed by compression rock sequences including ophiolite complexes exposed along this boundary are strongly dismembered sheared and mylonitized shearing planes and foliations are either subvertical or dipping at high angles to the northeast this zone is suggested to be the suture between the afro arabian and the iranian plates overall the intensity of deformation increases northeastward from the persian gulf mesopotamian basin where strata are undeformed and horizontal through the zagros simply folded belt which is characterized by en echelon doubly plunging flexural slip folds gentle to open in the southwest and close to locally sw overturned in the northeast the intensity of deformation continues to increase further northeastward through the sanandaj sirjan zone where thrust faulting is dominant this pattern suggests that the deformational front has migrated through time from the northeastern part of the sanandaj sirjan zone i e the suture zone to its present position in the central portion of the persian gulf mesopotamian foreland basin

focused pliocene quaternary exhumation of the eastern pamir domes western china abstract the kongur shan and muztagata domes are the most prominent topographic features in the eastern pamir indenter corner in spite of several previous bedrock thermochronology studies the extent processes and mechanisms of dome exhumation remain unclear we present 1158 detrital zircon fission track dzft ages from modern glacier and river sediments along the domes to better constrain the spatial distribution of exhumation our thermochronologic dataset from the chakragil massif shows a sharp increase in the proportion of dzft ages 10 ma from basins that drain the peak region to those further to the north which suggests that the kalagile fault forms the northern boundary of the rapidly exhuming dome structure a cluster of middle miocene dzft ages in these samples documents pre doming cooling possibly associated with motion on the main pamir thrust and or oytag fault large fractions of dzft grain ages

quaternary structural partitioning within the rigid tarim plate inferred from magnetostratigraphy and sedimentation rate in the eastern tarim basin in china abstract it has been proposed that within the tarim basin tectonic activity has been limited since triassic time however on the basis of magnetostratigraphy from the eastern tarim basin which defines the chronology of sedimentation and structural evolution of the basin we show that the basin interior has been uplifted and partitioned during quaternary the magnetostratigraphy was constructed from 2228 samples that yielded acceptable inclination values characteristic remnant magnetization chrm with both normal n1 n11 and reversed r1 r11 polarity was isolated by thermal demagnetization the data correlate best with polarity chrons c3r to c1n which range from 5 39 ma to recent on the geological time scale 2004 gts2004 an abrupt decrease in the sedimentation rate is observed at 1 77 ma in the ls1 core this change does not overlap with known pleistocene climate change events we attribute this sedimentation rate decrease to a structurally controlled local decrease in accommodation space where basin basement uplifts occur this period of sedimentary environmental change reveals that structural partitioning in the basement of the tarim basin occurred since 1 77 ma and we speculate that tilting of the southeast uplift a sub basin unit within the tarim basin began in early pleistocene time

structural styles in the zagros simple folded zone iran arabia eurasia convergence is achieved in the nw zagros by a combination of shortening on nw se trending folds and thrusts mainly in the simple folded zone and by right lateral strike slip on the nw se trending main recent fault a balanced and restored cross section across this part of the range indicates c 49 km of shortening this probably occurred since c 5 ma providing an estimate of the long term shortening rate across the simple folded zone of c 10 mm a 1 the geometries of exposed structures suggest both basement thrusts and thin skinned decollement levels with major folds possibly nucleated above basement faults fold geometries indicate several decollement horizons shale units are candidates as well as evaporites in the neogene mesozoic lower palaeozoic and upper proterozoic successions the se part of the simple folded zone deforms by north south shortening on broadly east west trending folds and thrusts the link between these regions occurs via a set of fault blocks c 400 km wide in total each bounded by north south right lateral faults incremental changes in the strike of some of the folds occur across these right lateral faults with more east west orientations to the east

apatite fission track evidence for neogene uplift in the eastern kunlun mountains northern qinghai tibet plateau china abstract forty one apatite fission track ages aft were determined on samples collected along a n s section of the eastern kunlun mountains across the middle and south kunlun faults between buqingshan and dulan measured aft ages lie between 25 2 and 130 10 ma and all are significantly younger than their host rock formation or sediment deposition ages modelling the aft data identifies a two stage regional cooling history that spans the last 100 myrs the earliest cooling phase occurred between the late jurassic and early tertiary and involved a moderate level of cooling between 20 and 40 c equivalent to average exhumation rates of 15 m myr the second phase of cooling took place from 20 ma with cooling rates increasing tenfold average exhumation rates for this period are estimated to be in the range of 100 150 m myr the first stage of protracted cooling is consistent with regional evidence from the qiantang and lhasa terrans where previous studies have noted low rates of denudation in relation to a back arc extensional setting the more recent acceleration in cooling seen in the kunlun data coincides with an increase in sedimentation rates in the adjacent qaidam basin this points to a phase of neogene uplift and increased erosion of the kunlun range although contemporaneous monsoon strengthening may also have had a role

from folding to transpressional faulting the cenozoic fusha structural belt in front of the western kunlun orogen northwestern tibetan plateau fusha structural belt fsb is one of the most important tectonic units in front of the western kunlun orogen northwestern tibetan plateau nw china in which the kekeya oil field was discovered in 1971 however there is no new oil field discovered since then due to the unclarity of the intense and complex cenozoic deformation in this area based on field investigation seismic interpretation and continuous electromagnetic profile data we analyze in detail the cenozoic deformation history emphasizing on the spatial and temporal variation of the deformation of the fsb in this paper the result suggests that the fsb was dominated by two deformation events 1 early miocene early pliocene folding event expressed by anticline with the western segment e w orienting while the eastern segment nww see orienting and 2 later since late pliocene transpressional faulting event that destroyed and divided the earlier anticline into a number of fault blocks the transpressional faulting caused dextral strike slip reverse fault with the dip angles decreasing eastward from 90 to 45 the dextral strike slip reverse fault developed in the core of the anticline in the western part which caused the anticline into several fault blocks while in the eastern part the fault developed in the north limb of the anticline with the core of the anticline reserved based on the spatial variation of structural characteristics we propose that the fault block traps and anticline traps in the eastern segment and fault block traps in western segment are favorable for hydrocarbon accumulation

cenozoic evolution of the pamir plateau based on stratigraphy zircon provenance and stable isotopes of foreland basin sediments at oytag wuyitake in the tarim basin west china abstract the pamir salient is the western expression of mountain growth related to indo eurasian convergence though a rough framework has emerged describing the tectonic evolution of the pamir detailed knowledge of the spatial and temporal evolution of cenozoic deformation is necessary to determine how strain progressed through the orogenic belt here we present new stratigraphic zircon provenance and stable isotope data from jurassic to miocene strata along the pamir s northeastern margin near the town of oytag wuyitake in the tarim basin west china prominent 40 ma peaks in oligocene to early miocene detrital zircon grains record the erosion of an eocene belt of shoshonitic rocks in the central to southeastern pamir this is roughly coincident with an 4 shift in the oxygen isotopic composition 18o of carbonates during the eocene and or oligocene from an average of 8 7 to 12 6 suggesting a reorganization of atmospheric circulation during that time this could have been caused by uplift of tarim basin bounding ranges and or retreat of the paratethys sea a subsequent change from eocene to jurassic aged detrital zircon grains in the early to middle miocene indicates provenance shifted from source rocks in the central and or se pamir to the hanging wall of the main pamir thrust mpt coincident with prograding facies at that time this suggests deformation progressed outward toward the northeast margin of the pamir plateau in the early to middle miocene our results corroborate outward advancement of himalayan deformation affecting all margins of the tarim basin by the middle miocene

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

modeling of thrust fronts above ductile and frictional detachments application to structures in the salt range and potwar plateau pakistan series of scaled sandbox models are used to simulate the development of thin skinned simultaneous shortening above adjacent ductile and frictional substrates these models simulate the evolution of the potwar plateau and salt range in pakistan where pale

salt flow and diapirism related to extension at crustal scale abstract the analysis of the structure and history of salt diapirs in large ancient evaporitic basins such as the southeastern north sea basin suggests that diapirism is controlled by crustal scale extension laboratory experiments on small scale models designed to simulate configurations comparable to the southeastern north sea basin show that diapirs which grow in a sedimentary cover during basement extension can develop close to basement normal faults or at a significant distance from them if the displacement on the basement faults is transfered horizontally along the salt layer for given values of salt viscosity strain rate and friction coefficient in brittle rocks the pattern of salt diapirism in a particular area depends on the ratio of cover thickness to salt thickness as well as the absolute thicknesses of cover and salt layers the experiments give criteria for identifying different types of diapirs and provide models of horizontal flow in a salt layer undergoing extension and diapir development some dynamic implications of the experiments are applied to the southeastern north sea basin

convergence history across zagros iran constraints from collisional and earlier deformation the zagros orogen provides a unique opportunity within the alpine system to evaluate the interplay between a young tertiary collision and earlier subduction obduction processes within the crush zone and the sanandaj sirjan internal zone separating the zagros fold belt from central iran we document several major tectonic events taking place at the end of the cretaceous of the eocene and from the mio pliocene onwards ca 20 15 ma contrary to recent interpretations our data cross sections and description of the overall deformation style strongly suggest that the main zagros thrust mzt is deeply rooted possibly to moho depths and that the suture zone effectively runs along the mzt field observations show that the final resorption of the oceanic domain took place slightly after 35 ma and that collision must have started before ca 23 25 ma in northern zagros the shortening rate across the crush zone since the mid miocene 20 15 ma is estimated at a minimum 3 4 mm year shear movements in the crush zone during the eocene oligocene period and extensional strike slip movements in the internal zones during the late cretaceous point to an oblique setting early in the convergence history a geotectonic scenario for convergence from the time of obduction to the present is finally proposed

cenozoic depositional sequences in the piedmont of the west kunlun and their paleogeographic and tectonic implications abstract the west kunlun forms the northwestern margin of the qinghai tibet plateau well developed cenozoic depositional sequences in the piedmont along the margins of the tarim basin record changes in sedimentary environment and the uplift of the west kunlun during the cenozoic during latest cretaceous to oligocene deposition in the west kunlun occurred in a marine environment the tarim bay during the paleogene gypsum beds bivalve shell limestones and variegated clastics were deposited rapid sedimentation during the late miocene resulted in the deposition of molasse sediments 2000 3000 m thick indicating a relatively high depositional rate the upper miocene sequences show a coarsening up tendency indicating a rapid and accelerated uplift of the west kunlun from late miocene to early pleistocene times molasse deposition was interrupted in the early pleistocene by a tectonic pulse which resulted in tilting of the molasse and underlying sediments at high angle towards the tarim basin undeformed middle to late pleistocene coarse fluvial and pluvial deposits overlie the steeply dipping molasse and older rocks unconformably and represent the resumption of rapid deposition a continual high rate of uplift during the holocene is presumed on the basis of an incised drainage system that flows from west kunlun into the tarim basin and cuts middle to late pleistocene gravels and older sediments to a depth from 50 m to more than 100 m although climatic changes may also have played a part

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

experimental modeling of role of gravity and lateral shortening in zagros mountain belt dynamically scaled analogs of the geologic structures of the zagros mountain belt are used to argue that different parts of the zagros mountains of iran record different combinations of the effects of a gravity driven overturn and a southwest northeast lateral shortening superimposed on the zagros overturn partially scaled material models have been used to simulate the zagros geodynamics which involve layer parallel compression of a 6 to 7 km thick phanerozoic carbonate cover containing a pattern of preshortening diapirs the folds in the zagros form rapidly 1 5 mm yr in a 20 to 30 km wide zone reactive some of the preshortening diapirs and generate new synshortening listric diapirs a third set of postshortening diapirs rises from the hormuz decollement behind the fold thrust front model buckle folds superimposed on diapirs or pillows tend to avoid and curve around preshortening diapirs which flatten in the synclines model profiles show that lateral shortening induces residual salt at depth to flow toward and rise through the anticlinal cores as synshortening or postshortening diapirs i suggest that any salt pillows in currently diapir free zones of the zagros fold thrust belt may surface as diapirs through the anticlines in the future in the absence of well data seismic and field observations i have used only three map pattern criteria to recognize the timing of diapirs these are locally obscured by extrusive salt sheets preshortening diapirs are generally small and elongate parallel to fold axes and are restricted to synclines synshortening diapirs are elongate perpendicular to the fold axes and are restricted to anticlines postshortening diapirs can be the same size as synshortening diapirs or larger and can be circular they are more common in the anticlines

magnetostratigraphic record of the early evolution of the southwestern tian shan foreland basin ulugqat area interactions with pamir indentation and india asia collision the tian shan range is an inherited intracontinental structure reactivated by the far field effects of the india asia collision a growing body of thermochronology and magnetostratigraphy datasets shows that the range grew through several tectonic pulses since 25 ma however the early cenozoic history remains poorly constrained the time lag between the eocene india asia collision and the miocene onset of tian shan exhumation is particularly enigmatic this peculiar period is potentially recorded along the southwestern tian shan piedmont there late eocene marine deposits of the proto paratethys epicontinental sea transition to continental foreland basin sediments of unknown age were recently dated we provide magnetostratigraphic dating of these continental sediments from the 1700 m thick mine section integrated with previously published detrital apatite fission track and u pb zircon ages the most likely correlation to the geomagnetic polarity time scale indicates an age span from 20 8 to 13 3 ma with a marked increase in accumulation rates at 19 18 ma this implies that the entire oligocene period is missing between the last marine and first continental sediments as suggested by previous southwestern tian shan results this differs from the southwestern tarim basin where eocene marine deposits are continuously overlain by late eocene oligocene continental sediments this supports a simple evolution model of the western tarim basin with eocene oligocene foreland basin activation to the south related to northward thrusting of the kunlun shan followed by early miocene activation of northern foreland basin related to overthrusting of the south tian shan our data also support southward propagation of the tian shan piedmont from 20 to 18 ma that may relate to motion on the talas fergana fault the coeval activation of a major right lateral strike slip system allowing indentation of the pamir salient into the tarim basin suggests far field deformation from the india asia collision zone affected the tian shan and the talas fergana fault by early miocene

detachment folding in the central and eastern zagros fold belt iran salt mobility multiple detachments and late basement control abstract detachment folding has been studied on the basis of field and subsurface examples from the central and eastern zagros iran we discuss different aspects of detachment folding well illustrated in the studied area in particular we focus on salt mobility multiple decollements and late basement control salt mobility concerns the hormuz basal detachment and the gachsaran upper detachment for the latter it is shown that mobility results not only from folding related diapirism but also from early gravity driven migration from growing anticlines towards intervening synclines concentric folding between two detachment levels is directly observed in the izeh zone central zagros where it is shown that the wave length depends on the distance between the two active decollements and that the fold shape is a function of the level of erosion throughout the zagros detachment folds mainly developed during an initial thin skinned phase of deformation which was followed by the current thick skinned stage this succession is particularly well expressed in the eastern zagros where basement faults cut early detachment folds obliquely

tertiary evolution of the western tarim basin northwest china a tectono sedimentary response to northward indentation of the pamir salient 1 this paper deals with the tertiary tectonic and sedimentary evolution of the western tarim basin based on an integrated stratigraphic sedimentary structural and tectonic analyses basin evolution is divided into three stages paleogene miocene and pliocene the western tarim basin was the easternmost part of the tethyan realm from late cretaceous to paleogene and marine sedimentation continued into the early miocene miocene development of the western tarim basin was chiefly governed by west kunlun right slip faulting and the simultaneous northward thrusting of the pamir salient and tianshuihai terrane yecheng subbasin developed as a pull apart basin owing to synchronous activity of the west kunlun and the shache yangdaman right slip faults hotan foreland basin formed in response to northward displacement of the tianshuihai terrane and another might have developed in front of the advancing pamir salient in the miocene basinward thrusting became predominant in the orogenic belts adjacent to the western tarim basin in the pliocene north directed displacement and uplift of the tiklik thrust terrane fragmented the preexisting hotan foreland basin and collision of the pamir with the southern tian shan deformational fronts caused complete destruction of the miocene pamir foreland basin eastward displacement of the qimugen fold thrust system led to flexural subsidence of the yecheng subbasin in the pliocene kashi subbasin developed as part of the southern tian shan foreland basin and was controlled by the eastern pamir as well a tectonic scenario is proposed to illustrate complicated interplay of the western tarim basin with its peripheral orogens in the tertiary

the structure and kinematics of the southeastern zagros fold thrust belt iran from thin skinned to thick skinned tectonics 1 we present the first complete balanced cross section across the southeastern zagros fold thrust belt zftb the following main structural features emerge from this section 1 in the south of the zftb the proterozoic to recent sedimentary sequence has been decoupled from its panafrican basement along the ductile basal evaporites and folded into a series of large detachment anticlines ongoing shortening of these structures has resulted in migration of the basal salt layers into the cores of the anticlines and propagation of forelimb thrusts 2 in the north of the zftb deep seated ramps have folded the hanging wall rocks and produced imbrications and duplex structures within the higher levels of the sedimentary sequence 3 out of sequence thrusts linked to major seismogenic basement faults have cut through the structures in the cover of the zftb a three step incremental restoration of the section shows that two main phases of deformation can be separated in the tectonic evolution of the zftb a mio pliocene thin skinned phase in the course of which most of the structures in the cover were generated followed by a pliocene to recent thick skinned phase expressed as out of sequence faulting in the cover which is currently underlined by the seismicity within the basement in plan view the initial structures of the southeastern zftb developed with a curved shape essentially controlled by the shape and thickness of the underlying proterozoic salt basin i e the jura style in the following basement involved phase out of sequence thrusts cut at oblique angles through the preexisting structures of the cover the total shortening absorbed in the cover amounts to at least 45 km corresponding to a ratio of 22

diachronous seawater retreat from the southwestern margin of the tarim basin in the late eocene in contrast to the present hyper arid inland basin surrounded by the high mountains of central asia the western tarim basin was once connected with the tajik basin at least in the late eocene when an epicontinental sea extended from the western tarim basin to europe western tarim is a key site for studying the retreat of seawater which was likely caused by the northward indentation of the pamir arc and facilitated by the climatic cooling and eustatic sea level change in the cenozoic here we present a new magnetostratigraphic record from the tarim basin that provides evidence of diachronous seawater retreat from its southwestern margin we studied about 1360 m of well exposed eocene oligocene strata at keliyang in the folded foreland of the west kunlun orogen until now the age of the strata has only been minimally constrained by the presence of late mid eocene marine fossils our biostratigraphic and magnetostratigraphic results demonstrate that the age of the sedimentary sequence ranges from 46 ma to 26 ma mid eocene to late oligocene and the seawater retreat at keliyang took place at 40 ma considering the stepwise northward indentation and uplift of the pamir orogen together with the other previous results we propose that seawater retreat from the southwestern margin of the tarim basin was diachronous in the late eocene ranging from 47 ma to 40 ma the regional indentation uplift and erosion of the pamir orogen played the dominant and important role in controlling the seawater retreat from the southwestern margin of the tarim basin

pre existing salt structures and the folding of the zagros mountains four dimensional analogue x ray tomography imagery is used to investigate the role played by pre existing salt structures during compressive deformation initially linear salt structures evolve towards more axisymmetric diapirs depending on the diapir geometry and on its thickness relative to the sedimentary column thickness the diapirs are either 1 shortened and localize sharp overturned folds for vertical pipe like diapirs or else 2 act as preferentially oriented ramps the diapir being incorporated in the fold for pillow like diapirs the ridges have a strong effect on the lateral extent and orientation of folds they disconnect the folds formed on either side of the salt wall compressional relays between ridges allow for a folded connection between both sides the zagros mountains in southern iran offer a large variety of comparable structures associated with the hormuz salt level which acts as the regional decollement most of the salt structures have been active from the early palaeozoic until the present day the firstorder critical taper is controlled by the distribution of hormuz decollement level and by its thickness at a smaller scale the fold geometry and size are locally controlled by the pre existing salt structures which are the main source of heterogeneity in the deformation

role of the kazerun fault zone in the formation and deformation of the zagros fold thrust belt iran 1 the kazerun fault is a n s trending fault zone which obliquely truncates the nw se trending zagros fold thrust belt this active fault zone is an ancient structural lineament which has controlled the structure sedimentation and subsidence of the central part of the zagros since the early cambrian and has had an influence on the formation of the hydrocarbon system of the belt the kazerun fault limited the distribution of the cambrian hormuz salt the major decollement horizon that separates the precambrian basement from the thick sedimentary cover to the west its later reactivation with other n s trending fault zones e g the izeh fault zone during the cretaceous resulted in major sedimentary thickness and facies variations along the belt this study presents a new interpretation for the evolution of the kazerun fault zone based on field evidence and a review of various published and unpublished data it is argued that at the surface the fault zone is delineated by four north south trending segments and that marked differences occur in the distribution of deformation on either side of the fault segments in the late tertiary during this time these segments acted as transfer faults lateral ramps linking different segments of the zagros deformation fronts