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

eolian dune interdune sand sheet and siliciclastic sabkha sediments of an offshore prograding sand sea dhahran area saudi arabia an offshore prograding sand sea exists along portions of the arabian gulf coastline near dhahran saudi arabia in this region sediments of eolian dune interdune sand sheet and siliciclastic sabkha intercalate with marine deposits this depositional setting is characterized by strong offshore winds which supply abundant sand to the coastline and cause at present time the outbuilding of the dune system this quartz detrital dominant setting contrasts markedly with the carbonate dominant setting resulting from onshore winds in the trucial coast area to the south the broad intercalation of eolian and marine deposits which results creates ideal potential for subregional stratigraphic petroleum traps due to pinch out of porous and permeable dune sands into impermeable m rine mudstones within the eolian system itself are potential reservoir rocks dunes sources organic rich sabkha and interdune deposits and seals zones of early cementation in all deposits early cementation is very common in all facies of the eolian sand sea the early cementation occurs owing to 1 soil formation 2 deposition of pore filling gypsiferous cements from saturated solutions near water table and 3 addition of sand size windblown evaporitic material to sands downwind of sabkhas

salt tectonics and tear faulting in the central part of the zagros fold thrust belt iran abstract the central part of the zagros fold thrust belt is characterized by a series of right lateral and left lateral transverse tear fault systems some of them being ornamented by salt diapirs of the late precambrian early cambrian hormuz evaporitic series many deep seated extensional faults mainly along n s and few along nw se and ne sw were formed or reactivated during the late precambrian early cambrian and generated horsts and grabens the extensional faults controlled deposition distribution and thickness of the hormuz series salt walls and diapirs initiated by the early paleozoic especially along the extensional faults long term halokinesis gave rise to thin sedimentary cover above the salt diapirs and aggregated considerable volume of salt into the salt stocks they created weak zones in the sedimentary cover located approximately above the former and inactive deep seated extensional faults the n s to nne ssw direction of tectonic shortening during the neogene zagros folding was sub parallel with the strikes of the salt walls and rows of diapirs variations in thickness of the hormuz series prepared differences in the basal friction on both sides of the precambrian cambrian extensional faults which facilitated the zagros deformation front to advance faster wherever the salt layer was thicker consequently a series of tear fault systems developed along the rows of salt diapirs approximately above the precambrian cambrian extensional faults therefore the present surface expressions of the tear fault systems developed within the sedimentary cover during the zagros orogeny although the direction of the zagros shortening could also potentially reactivate the basement faults as strike slip structures subsurface data and majority of the moderate large earthquakes do not support basement involvement this suggests that the tear fault systems are detached on top of the hormuz series from the deep seated precambrian cambrian extensional faults in the basement

thermal evolution of the kuh e asmari and sim anticlines in the zagros fold and thrust belt implications for hydrocarbon generation abstract mixed layer clay minerals vitrinite reflectance and geochemical data from rock eval pyrolysis were used to constrain the burial evolution of the mesozoic cenozoic successions exposed at the kuh e asmari dezful embayment and sim anticlines fars province in the zagros fold and thrust belt in both areas late cretaceous to pliocene rocks show low levels of thermal maturity in the immature stages of hydrocarbon generation and early diagenetic conditions r0 i s and ro values

age of synorogenic deposits and timing of folding in dezful embayment sw zagros fold belt abstract syntectonic deposits of the mesopotamian flexural basin have been dated in the lurestan and fars salients in the zagros foldbelt since the early 2000 s but not in the dezful embayment where most of the zagros foreland oil is trapped we use 237 samples collected for magnetostratigraphy to date shallow marine to fluvial alluvial pre growth and growth strata deposits along a 2700 m section in the ne flank of the jarik anticline in north dezful embayment the jarik anticline grew by a combination of compression and coeval diapirism like other structures in north dezful embayment the correlation of the local magnetostratigraphy with the geomagnetic polarity time scale indicates ages of 14 1 ma and 13 6 ma for the bases of the mishan and aghajari formations the bases of lahbari mb and bakhtyari fm are 9 0 ma and 7 0 ma the onset of growth strata in the ne flank of the jarik anticline is 12 8 ma with a duration of 5 8 myr for this anticline this study presents for the first time the age of syntectonic deposition and folding in the dezful embayment that is essential to determine burial and generation of hydrocarbons in this oil rich province

lithospheric structure beneath the south eastern zagros mountains iran recent slab break off integrated lithospheric modelling based on the combined interpretation of gravity geoid and topography data sets highlights a previously undocumented lithospheric thinning beneath the zagros collisional belt iran which we propose to relate to recent slab break off at the continent ocean transitional lithosphere recent published data on the distribution of seismicity at depth support this interpretation in agreement with other published models for the zagros mountains the overlying crust exhibits by contrast a noticeable thickening reaching a maximum of 52 km the consequent thermal uplift expected from slab break off is suggested to have modified the zagros wedge taper and triggered the recently documented switch from thin skinned to thick skinned deformation in the zagros fold thrust belt

active deformation within the zagros mountains deduced from gps measurements we present and interpret the results of global positioning system gps measurements at 35 stations in and beside the zagros mountain belt sw iran for three campaigns ending march 1998 december 1999 and june 2001 preliminary motion estimates show clearly the change in character along the strike of the belt stations to the se move at 13 22 3 mm a 1 towards n 7 5 e with respect to eurasia most of the shortening indicated by the gps velocities seems to occur in the se zagros along two major seismic zones and along the zagros front to the nw stations move oblique to the trend of the belt towards n 12 8 w at 14 19 3 mm a 1 most of the shortening in the nw zagros seems to occur along the mountain front fault with its major earthquakes as well as along the zagros front the change in direction and magnitude of the velocity vectors across the north south trending kazerun and karebas faults involves extension of up to 4 mm a 1 along the strike of the zagros belt

regional stratigraphy of the zagros fold thrust belt of iran and its proforeland evolution the latest neoproterozoic through phanerozoic stratigraphy of the zagros fold thrust belt of iran has been revised in the light of recent investigations the revised stratigraphy consists of four groups of rocks each composed of a number of unconformity bounded megasequences representing various tectonosedimentary settings in the lowest group ranging in age from latest precambrian to devonian the uppermost neoproterozoic to middle cambrian rocks constitute a megasequence of evaporites siliciclastic deposits and interlayered carbonates which were deposited in pull apart basins that developed by the najd strike slip fault system this megasequence is overlain by a second one middle to late cambrian in age which consists of shallow marine siliciclastic and carbonate rocks representing deposition in an epicontinental platform the overlying shales siltstones and partly volcanogenic sandstones of ordovician silurian and devonian age are local remnants of stratigraphic units that were extensively eroded during development of several major unconformities the second group consists of two megasequences one permian and the other triassic composed of widespread transgressive basal siliciclastic rocks and overlying evaporitic carbonates of an equatorial epi pangean very shallow platformal sea the third group is composed of four megasequences formed of shallow and deep water carbonates with some siliciclastic and evaporite deposits which accumulated on a neo tethyan continental shelf during earliest jurassic through late turonian time the fourth group comprises siliciclastic and carbonate deposits of a largely underfilled nw to se trending forward and backward migrating late cretaceous to recent proforeland basin which has evolved as an integral part of the zagros orogen this last group consists of three megasequences ix x and xi with distinctive lateral and vertical facies variations which reflect specific tectonic events megasequence ix comprises uppermost turonian to middle maastrichtian prograding and retrograding siliciclastic and carbonate deposits whose accumulations reflect emplacement obduction of ophiolite slivers and subsequent collisional events in the zagros orogen megasequence x consists of uppermost maastrichtian to upper eocene siliciclastic and carbonate rocks which deposited first progradationally in front of the zagros orogenic wedge with reduced contractional tectonic activity and then retrogradationally due to intensified thrust stacking in the interior parts of the orogen megasequence xi consists of oligocene and lower miocene carbonate strata deposited retrogradationally shortly after a period of intensified late eocene thrust faulting in the deformational wedge and an overlying succession of upward coarsening northeasterly derived siliciclastic deposits of lower miocene to recent age which are composed of erosional byproducts of the southwest vergent zagros thrust sheets

a warm layer in the nightside mesosphere of mars we report a new set of stellar occultation measurements for nightside temperature profiles made by the maven iuvs that provide evidence for a recurring layer of warm air between 70 90 km altitudes in the nightside mesosphere of mars during ls 0 180 in martian year 33 34 the nightside profiles reveal a recurring peak of atmospheric temperature around 80 km over the equator to the middle latitudes in the northern hemisphere the predictions of the mars climate database have a warm layer with much smaller amplitudes the observed peak amplitudes are larger than those predicted by the model by up to 90 k wavenumber 3 structures are seen in the warm layer that are potentially signatures of thermal tides or stationary planetary waves with amplitudes two times larger than predicted

the zagros folded belt fars iran constraints from topography and critical wedge modelling summary the late miocene tectonics of the zagros folded belt fars province has for long been related solely to folding of the cover controlled by a ductile decollement between basement and the sedimentary cover however geological constraints topography analysis and seismotectonic studies reveal that basement thrusting may produce locally significant deformation in the cover to determine how the deep seated deformation in the basement may contribute to the overall topography we first examine the filtered large and short wavelengths of the topography we find that the short wavelength component of the topography 20 25 km including the zagros folds is superimposed on the differential uplift at the regional scale in other words the regional base level of folded marker horizons remains parallel to the regional topography of interest modelling reveals that the salt based wedge model alone is not able to reproduce the large wavelength component of the topography of the zagros folded belt this reveals that when a thick relatively to its overburden layer of salt forms the basal decollement it is generally too weak and cannot support the growth of significant topography we then test an alternative thick skinned crustal wedge model involving the crust of the arabian margin which is decoupled above a viscous lower crust this model satisfactorily reproduces the observed topography and is consistent with present day basement thrusting topography analyses and geological constraints we conclude that basement involved thickening and shortening is mechanically required to produce the shape of the zagros folded belt since at least 10 ma finally the involvement of the basement provides mechanical and kinematic constraints that should be accounted for cross sections balancing and further assessing the evolution of zagros at crustal or lithospheric scales

magnetostratigraphy of miocene pliocene zagros foreland deposits in the front of the push e kush arc lurestan province iran abstract the timing of the deformation in the zagros simply folded belt is poorly constrained because of the lack of an accurate absolute chronology of the syntectonic sedimentary sequences the foreland basin infill at the front of the push e kush arc is composed of fine grained fluvial plain deposits agha jari fm and coarse conglomerates at the top of the section bakhtyari fm a magnetostratigraphic study was carried out in a composite section spanning about 2800 m in order to date growth strata and to constrain the timing of the deformation in the mountain front flexure mff magnetostratigraphic correlation of the base of the agha jari fm with chron c5a yields an age of 12 8 to 12 3 ma for this base the transition to the conglomerates of the bakhtyari fm correlates with the upper gauss chron c2an at approximately 3 ma the deposition age of the top of the preserved bakhtyari fm is extrapolated around the pliocene pleistocene boundary the base of the agha jari fm growth strata and thus the beginning of the deformation in the front of the push e kush arc is dated at 8 1 7 2 ma the topmost preserved bakhtyari is folded in the ne flank of the changuleh anticline and is unconformably overlying the sw flank of the anaran anticline this indicates that the tectonic deformation in the front of the push e kush arc was active at least during 5 my the mff is a relatively long lived structure active from 8 1 to 7 2 ma to about the pliocene pleistocene boundary partly synchronous with the changuleh anticline to the foreland after mff tectonic cessation only the changuleh anticline remained active

tertiary block rotations in the fars arc zagros iran summary the fars arc accommodates the oblique convergence between the arabic plate and the iran block many geological observations suggest block rotations from regional to local scales we present palaeomagnetic investigations in the fars arc and its eastern termination the zagrosmakran syntaxis sixty four sites have been sampled covering the palaeocene pabdeh fm to mio pliocene agha jhari fm the latest being the most sampled formation we document pre tilting components in all formations however coarse fractions of agha jhari clastics formation retain a post tilting remagnetization as a whole block rotations rarely exceed 20 in the western fars arc clockwise and counter clockwise rotations of small amplitudes are consistent with the torsions observed near the strike slip kazerun and mangarak faults in the zagros makran syntaxis counter clockwise and clockwise rotations are observed respectively in the western and eastern part this pattern is consistent with an amplification of the shape of the syntaxis between zagros and makran palaeomagnetic data support that the presentday arcuate shape of the arc is secondary we assume that most of the block rotations took place during the plio pleistocene during a blocking stage of the zagros makran syntaxis we emphasize the role of oman peninsula which plays as an indenter for the propagation of the fars thrust belt

source rock distribution and maturation in the zagros orogenic belt provenance of the asmari and bangestan reservoir oil accumulations abstract the zagros orogenic belt of iran is one of the most prolific petroliferous areas accounting for approx 12 of proven global reserves correlation techniques reveal that a majority of the oils variously reservoired in asmari oligo miocene and bangestan group upper cretaceous anticlinal structures share a common provenance oils of the n e khuzestan fields are an exception showing a conspicuously different origin candidate source potential for the crucial central zagros embayment and contiguous areas was assessed on field survey and from well materials collected during the decade from 1968 onwards although varying locally in vertical and lateral distribution attractive sources occur throughout the section included were silurian shales the sargelu middle jurassic garau gadvan lower cretaceous kazhdumi albian gurpi upper cretaceous and pabdeh paleogene fms maturation of these source units was essentially controlled by the foredeep subsidence related to the zagros orogeny being a neogene event hydrocarbon generation and migration are very recent and essentially synorogenic consolidation of this information with the real distribution of candidate sources application of carbon isotope based source oil assignments and biomarker results successfully differentiated the provenance of the generic oil groupings over much of khuzestan the kazhdumi was recognised as the major contributor elsewhere the pabdeh fm yields isotopically distinctive oils in n e khuzestan evaluation of this basin allowed identification of prolific source rocks in low energy euxinic argillaceous lime mudstones similarly it provided an early application of pyrolysis techniques carbon isotopic correlations and subsidence history maturation migration modelling approaches now routinely employed in basin evaluation

structural style and kinematic analysis of folding in the southern dezful embayment oilfields sw iran abstract compression of a region containing multiple detachment layers produces large scale disharmonic folding where individual competent units separated by detachment fold independently within the succession here we present a case study of the kinematic evolution of three subsurface structures the karanj paranj and parsi oilfields bounded by multiple detachments located in the southern dezful embayment a major petroleum province of the zagros fold thrust belt in sw iran interpretation of seismic sections and the construction of corresponding balanced cross sections reveals different geometries along the folds and the complete decoupling of these structures from the surface geology this is controlled by the reactivation of basement faults and flow of the gachsaran incompetent units miocene as the upper detachment and the kazhdumi upper cretaceous pabdeh gurpi and dashtak formations as the middle detachments respectively detachment folding with limb rotation started in the middle miocene and continued with the migration of the basal detachment horizon equivalent hormuz series into the core of the anticlines flow of both the basal and upper detachments continued until no more material is available whereupon the shortening is accommodated by fault development the development of a decoupled disharmonic folding style was controlled by the upper detachment surface through migration from the crests of the anticlines to the synclinal areas and by the reactivation of the basement faults from nw to se part of the area the total shortening amounts are changed between 21 and 12

not so simple simply folded zagros the role of pre collisional extensional faulting salt tectonics and multi stage thrusting in the sarvestan transfer zone fars iran abstract the sarvestan plain is bounded by highly elevated anticlines associated with thrusts or transpressional faults and hosts the nnw sse sarvestan transfer zone surface and subsurface geological data and 22 seismic lines allowed us to reconstruct the 3d geometry of the area mixed layer illite smectite and 1d burial and thermal modelling were used to constrain the complex geological evolution of the sarvestan plain where inherited structures strongly controlled the geometry of syn to post collisional contractional structures paleozoic mesozoic rifting related extension generated e w and nnw sse normal fault systems such faults were associated with changes in the thickness of the sedimentary cover lateral facies changes were later induced by the cretaceous obduction of ophiolites cropping out some tens of km north of the study area during the miocene the footwall and the hanging wall of the sarvestan fault had different thermal evolution this is tentatively explained by flow of cambrian salt from the plain area towards the hanging wall of the sarvestan fault associated with salt diapirism during lower middle miocene time salt tectonics is invoked also to explain at least in part the development of the overturned anticline in the hanging wall of the sarvestan fault an early phase of contractional deformation occurred in the middle miocene since 15 my i e after the deposition of the agha jari fm generating the e w oriented folds buried below the plain likely inverting inherited normal faults the erosion of these structures was followed by the deposition of the bakhtiari fm conglomerates in middle late miocene times a later phase of contractional tectonics generated the thrust faults and the anticlines bounding the sarvestan plain some 6 5 my ago the sarvestan dextral transpressional fault that likely acted as a strongly oblique ramp of the maharlu thrust mainly structured in this period although its activity may have continued until present

simulation of foreland basin stratigraphy using a diffusion model of mountain belt uplift and erosion an example from the central alps switzerland foreland basin stratigraphy can be considered as the result of three interacting processes thrust deformation which builds the tectonic load sedimentary and erosional processes which redistribute that load and the flexural response of the lithosphere the resultant stratigraphy of foreland basins is commonly composed of a small number of shallowing and coarsening upward cycles bounded by regional unconformities to understand the development of these unconformities we present a simple model of these three processes coupling an evolving thrust wedge on a linear elastic plate with erosion and sedimentation defined by the diffusion equation applied to topography our model demonstrates the development of regional unconformities without recourse to either eustasy or complex viscoelastic models for the continental lithosphere the model describes the thrust wedge foreland basin system in terms of four parameters 1 the effective elastic thickness of the foreland plate te 2 the sediment transport coefficient k 3 the thrust wedge advance rate 4 the surface slope of the thrust wedge the model is applied to the oligocene miocene north alpine foreland basin nafb of eastern switzerland the stratigraphy of the nafb can be simplified into two large scale shallowing upward cycles separated by an unconformity at the base of the burdigalian 22 ma geological information is taken from the nafb to estimate suitable values for the parameters listed above assuming a linear elastic lithospheric rheology the te value is estimated at 10 5 km from decompacted sediment columns data to constrain the sequential development of the thrust wedge come from structural geology the early stages 40 24 ma of compression involved a relatively low angle thrust wedge with an advance rate of approximately 2 4 mm yr at about 24 ma the wedge advance slowed down and thickened by underplating crystalline basement of the foreland plate the value for the transport coefficient has been estimated from previous studies prior to attempting to simulate the broad scale geometry of the nafb the role of each parameter was assessed individually the values for te and k are held constant throughout the simulation of the nafb at 7 5 km and 500 m yr respectively the geometry of the base burdigalian unconformity is reproduced by variations in the parameters describing the thrust wedge the surface slope angle of the wedge is increased from 2 5 to 4 over 0 2 m y and the rate of thrust advance is decreased from 2 mm yr to 0 2 mm yr during the thickening event between 24 and 23 8 ma the rejuvenation of the internal parts of the thrust load causes backtilting of the foreland basin sediments and after a time lag erosion of the distal stratigraphy over the forebulge so simulating the base burdigalian unconformity

tertiary sequence of deformation in a thin skinned thick skinned collision belt the zagros folded belt fars iran 1 we describe how thin skinned thick skinned deformation in the zagros folded belt interacted in time and space homogeneous fold wavelengths 15 8 5 3 km tectono sedimentary evidence for simultaneous fold growth in the past 5 5 2 5 ma drainage network organization and homogeneous peak differential stresses 40 15 mpa together point to buckling as the dominant process responsible for cover folding basin analysis reveals that basement inversion occurred 20 ma ago as the arabia eurasian plate convergence reduced and accumulation of neogene siliciclastics in foreland basin started by 10 ma ongoing contraction occurred by underplating of arabian crustal units beneath the iranian plate this process represents 75 of the total shortening it is not before 5 ma that the zagros foreland was incorporated into the southward propagating basement thrust wedge folds rejuvenated by 3 2 ma because of uplift driven by basement shortening and erosion since then folds grew at 0 3 0 6 mm yr and forced the rivers to flow axially a total shortening of 65 78 km 16 19 is estimated across the zagros this corresponds to shortening rates of 6 5 8 km ma consistent with current geodetic surveys we point out that although thin skinned deformation in the sedimentary cover may be important basement involved shortening should not be neglected as it requires far less shortening moreover for such foreland folded belts involving basement shortening underplating may be an efficient process accommodating a significant part of the plate convergence

accommodation of the different structural styles in the foreland fold and thrust belts northern dezful embayment in the zagros belt iran structural styles in the zagros foreland fold and thrust belt vary spatially differential lateral propagation of folds causes to create tear faults in this belt in this research tear faults are studied in northern dezful embayment tear faults have been accommodated the different structural styles in sedimentary cover during the compressional regime in the zagros fold and thrust belt different structural styles indicate a difference in intensity deformation these faults originated as the pre existing inverted reactive deep seated faults or which activate in the sedimentary strata during the compressional regime investigation of the structural style of folds in the sedimentary cover is a key point to recognize tear faults in this research the structural style of the kabood qale nar bala rud and lab e safid subsurface anticlines in the northern dezful embayment has been studied the interpretation of seismic profiles balanced cross sections restoration and 3d structural modeling is investigated to study the structural style of mentioned anticlines the area of the studied region is 92 20 km2 two tear faults with nne trending have been separated qale nar and bala rud anticlines in the central part from lab e safid and kabood anticlines in eastern and western parts respectively the intensity of deformation in the lab e safid anticline is less than the qale nar and bala rud anticlines on its western side displacement and deformation of the kabood anticline are more than the qale nar anticline in its eastern side kabood anticline is multi bend fault bend fold qale nar and bala rud are fault bend folds and lab e safid is detachment fold tear faults have been accommodated by these different structural styles in this region

arabia eurasia continental collision insights from late tertiary foreland basin evolution in the alborz mountains northern iran a poorly understood lag time of 15 20 m y exists between the initial arabia eurasia continental collision in late eocene to early oligocene time and the acceleration of tectonic and sedimentary processes across the collision zone in the early to late miocene the late eocene to miocene pliocene clastic and shallow marine sedimentary rocks of the kond eyvanekey and semnan basins in the alborz mountains northern iran offer the possibility to track the evolution of this orogen in the framework of collision processes a transition from volcaniclastic submarine deposits to shallow marine evaporites and terrestrial sediments occurred shortly after 36 ma in association with reversals in sediment provenance strata tilting and erosional unroofing these events followed the termination of subduction arc magmatism and marked a changeover from an extensional to a contractional regime in response to initiation of continental collision with the subduction of stretched arabian lithosphere this early stage of collision produced topographic relief associated with shallow foreland basins suggesting that shortening and tectonic loading occurred at low rates starting from the early miocene 17 5 ma flexural subsidence in response to foreland basin initiation occurred fast sediment accumulation rates and erosional unroofing trends point to acceleration of shortening by the early miocene we suggest that the lag time between the initiation of continental collision 36 ma and the acceleration of regional deformation 20 17 5 ma reflects a two stage collision process involving the soft collision of stretched lithosphere at first and hard collision following the arrival of unstretched arabian continental lithosphere in the subduction zone

structural framework of the zagros fold thrust belt iran abstract data gleaned from the literature on the zagros have been compiled and used in conjunction with new interpretations to provide a better picture of the structures sedimentation history and deformation of this hydrocarbon rich mountain belt the belt parallel mountain front the n s trending kazerun izeh and e w trending bala rud fault zones are defined as the master structural elements of the belt these fault zones divide the zagros basin into zones with different stratigraphic successions and different rheological profiles this resulted in different structural styles developing along the belt during the subsequent collision the kazerun and izeh fault zones acted as the depositional system transition zone between the lurestan and fars regions in jurassic cretaceous time and partly controlled the distribution of the kazhdumi formation one of the major source rocks by the end of the cretaceous the nw se trending mountain front fault divided the present folded belt of the zagros into a major foreland basin to the southwest and a piggyback basin to the northeast activity along other major transfer fault zones including the izeh kazerun and bala rud fault zones occurred at this time and controlled the sedimentation and subsidence of the dezful embayment the main target region for hydrocarbon exploration these fault zones controlled the thickness of the asmari formation one of the main reservoirs and also the considerable thickness and facies changes of the gachsaran formation the major seal to the asmari formation the present morphology of the mountain belt is interpreted as being mainly related to the pinning of the mountain front fault to the northwest of the dezful embayment and to the north of the strait of hormuz

the zagros fold and thrust belt in the fars province iran ii thermal evolution abstract temperature dependent clay minerals and vitrinite reflectance data surface and subsurface geological constraints were used to unravel the burial evolution of the ordovician quaternary sedimentary successions from the inner to the outer zones of the zagros fold and thrust belt in the fars province iran these sedimentary successions were buried to their thermal maxima during early to late diagenesis achieving temperatures corresponding to the immature to early mature stages of hydrocarbon generation they experienced low levels of thermal maturity in the interior fars corresponding to vitrinite reflectance values between 0 38 and 0 66 to mixed layers illite smectite i s with an illite content between 30 and 75 and to ki values between 0 97 and 1 18 2 in the central and coastal fars vitrinite reflectance ranges between 0 35 and 0 51 the illite content in i s displays values between 20 and 85 and ki data are between 0 71 and 1 30 2 in individual anticlines mixed layers i s show an increase of the illite content as a function of stratigraphic age depth suggesting that levels of thermal maturity are controlled by sedimentary burial one dimensional thermal history models allowed us i to estimate the maximum burial experienced by the sedimentary successions and the amount of the sedimentary pile currently removed by erosion ii to determine the thickness of the ophiolite units obducted during late cretaceous time in the high zagros and iii to define the onset of oil generation for the albian source rocks throughout the zagros belt paoleothermal data were used to constrain the geometry of eroded structures in a 253 km long cross section extending from the high zagros to the coastal fars along the cross section lithostatic load slightly decreases towards the foreland e g from 3 65 km to 3 2 km for the bangestan group and the amount of the eroded material varies between 6 km above anticlines in the central and interior fars and 200 m above synclines in the external part of the belt

sequence stratigraphy of cenomanian turonian carbonate platform margins sarvak formation in the high zagros sw iran an outcrop reference model for the arabian plate

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

on the role of incompetent strata in the structural evolution of the zagros fold thrust belt dezful embayment iran abstract the dezful embayment is the most important fertile oil province of the zagros fold thrust belt it includes several incompetent strata as basal and intermediate decollement levels that play a significant role on the structural styles and hydrocarbon preservation based on the interpretation of seismic profiles the influence of the gachsaran formation and the evaporitic kalhur member of the asmari formation on the geometry of deformation was investigated in different parts of the dezful embayment obtained results revealed that the thickness of the incompetent strata plays a crucial role in the formation and geometry of different types of fold structures e g rounded box chevron detachment fold in the dezful embayment there is a sharp difference between the geometry of surface and deep seated structures due to the existence of thick intermediate decollements e g gachsaran and kalhur in the dezful embayment therefore fault geometry and fold styles in upper and lower parts of these decollements are totally different in addition these incompetent strata act as a barrier level against the propagation of deep seated faults into the overlying layers therefore it seems that most of the faults exposed on the surface have originated from the upper decollement levels in the study area

difference in the gps deformation pattern of north and central zagros iran summary measurements on either side of the kazerun fault system in the zagros mountain belt iran show that the accommodation of the convergence of the arabian and eurasian plates differs across the region in northwest zagros the deformation is partitioned as 3 6 mm yr 1 of shortening perpendicular to the axis of the mountain belt and 4 6 mm yr 1 of dextral strikeslip motion on northwest southeast trending faults no individual strike slip fault seems to slip at a rate higher than 2m m yr 1 in southeast zagros the deformation is pure shortening of 8 2m m yr 1 occurring perpendicular to the simple folded belt and restricted to the persian gulf shore the fact that most of the deformation is located in front of the simple folded belt close to the persian gulf while seismicity is more widely spread across the mountain belt confirms the decoupling of the surface sedimentary layers from the seismogenic basement a comparison with the folding and topography corroborates a southwestward propagation of the surface deformation the difference in deformation between the two regions suggests that right lateral shear cumulates on the north south trending kazerun strike slip fault system to 6 2m m yr 1

eocene early miocene foreland basin development and the history of himalayan thrusting western and central nepal sedimentologic petrographic and u pb detrital zircon ages from middle eocene through early miocene sedimentary rocks in the lesser himalayan zone of western and central nepal indicate that a peripheral foreland basin system had developed in the eastern himalayan collision zone by middle eocene time the shallow marine eocene bhainskati formation accumulated in a back bulge depozone between a southward migrating forebulge and the indian craton migration of the forebulge through this region during eocene oligocene time produced a regional unconformity that spans 15 20 myr by early miocene time the forebulge unconformity was onlapped by the distal fringes of the southward migrating foredeep depozone represented by fluvial deposits of the dumri formation continued southward migration of the foredeep during the neogene accommodated the fluvial siwalik group light mineral provenance data and u pb detrital zircon ages suggest that the bhainskati was derived partly from tethyan sedimentary rocks of the tibetan himalayan zone during initial growth of the himalayan fold thrust belt the dumri was derived from metasedimentary and crystalline rocks of the greater himalayan zone during emplacement of the main central thrust and contemporaneous tectonic unroofing by normal faulting along the south tibetan detachment system the lesser himalayan crystalline thrust sheets were emplaced soon after deposition of the dumri formation 15 10 ma paleocurrent and lithofacies data from the dumri formation indicate deposition by west southwestward flowing rivers that drained into the indus portion of the himalayan foreland basin system during the early miocene thick channel sandstones in the lower dumri may represent the early miocene counterpart of the modern ganges river eastward diversion of the ganges drainage system to near its present location had occurred by 15 ma as the high standing aravalli range on the northern indian shield approached the front of the fold thrust belt assuming reasonable values for the flexural rigidity of indian lithosphere the time span of the forebulge unconformity yields a velocity of 14 33 mm yr for the southward migration of the fold thrust belt relative to india this range of values is consistent with neogene and present day estimates and suggests that only one third to one half of india eurasia convergence has been accommodated by shortening in the himalayan fold thrust belt since the onset of collision

a new method of seismic site classification using hvsr curves a case study of the 12 november 2017 mw 7 3 ezgeleh earthquake in iran abstract on the 12th of november 2017 a strong earthquake with a moment magnitude of 7 3 struck the west of iran causing massive damage in sarpolezahab and surrounding areas in this study the horizontal to vertical spectral ratio hvsr or h v technique of strong ground motion recorded at 60 stations is used for identifying of site response and subsequent site classification very clear amplification is observed at stiff and soft soil sites empirical equations from the literature relating frequency of hvsr peak to average shear wave velocity in the upper 30m vs30 commonly used as a proxy for site classification were found to be unreliable making site classification difficult to overcome this problem a soft computing method based on the generalized regression neural networks grnn algorithm is used this algorithm relies on hvsr curves at the recording stations and uses pattern recognition against a set of pre defined curves for different site types in this approach site characterization is based on the overall features of the hvsr curves rather than just the peak frequency the stations are classified into four different site classes and the results are consistent with local geotechnical information where available rather than relying on vs30 which has been found deficient in many studies and is known to have difficulty in reliably estimating when geotechnical data is lacking site classification proposed in this study uses the overall characteristics of hvsr curves of response spectra of recorded strong motion data this method is proposed as a more reliable and direct method for site characterization in seismically hazardous regions

the present day deformation of the central zagros from gps measurements 1 in 1997 and in 2000 we measured the distances between 14 geodetic benchmarks across the central zagros mountain belt the results show that about 10 mm yr of shortening in the central zagros is distributed across the mountain belt this shortening corresponds to roughly 50 of the total convergence between arabia and eurasia and is consistent in direction the persian gulf does not deform significantly the main zagros reverse fault is not an active kinematic boundary the internal deformation of the folded belt is rather homogeneous at the scale of our survey which does not allow us to detect any individual active blind fault however the strain pattern suggests that n s dextral strike slip faults may accommodate part of the deformation

pliocene growth of the dowlatabad syncline in frontal fars arc folding propagation across the zagros fold belt iran this research was funded by the darius programme as well as the group of dynamics of the lithosphere geosciences barcelona geo3bcnconsejo superior de investigaciones cientificas csic spain we thank the paleomagnetic laboratory universitat de barcelona scientific and technological centers geo3bcn csic where the paleomagnetic analyses were conducted and also the laboratorio de geocronologia y geoquimica isotopica of the universidad complutense de madrid spain where the sr samples were processed in addition the study of calcareous nannofossils was supported by the research group of the basque university system it 930 16 we are also grateful to the national iranian oil company for their support during fieldwork we thank darius programme and its sponsors and projects alpimed pie csic 201530e082 and subtetis pie csic 201830e039 for additional support

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

estimation of dust fallout rates in the northern arabian gulf the penetration of dust clouds over a sea surface is modelled as a sediment transport diffusion problem the model is used to determine the steady state concentration field of two dimensional dust clouds during offishore dust storms the rates of dust deposition into the sea can then be calculated from the obtained concentration fields the model was applied to offshore dust storms blowing over the arabian gulf yielding estimated dust sedimentation rates of 0 8 mm yr 1 this is substantially higher by several orders of magnitude than dust fallout estimates in most seas of the world the calculated fallout rates are in line with the results of existing field measurements

structures of the zagros fold thrust belt in iran the zagros fold thrust belt in iran forms the external part of the zagros active orogenic wedge it includes a sequence of heterogeneous latest neoproterozoic phanerozoic sedimentary cover strata 7 to 12 km thick and composed of alternating incompetent and competent layers overlying precambrian crystalline basement with a complex pre zagros structural fabric balancing structures of the cover statigraphic units in the zagros fold thrust belt requires in sequence and out of sequence involvement of the precambrian basement in the deformation six detailed balanced and retrodeformable cross sections which are constructed based on geological and geophysical data across various sectors of the belt show fault bend and fault propagation folds interpreted to have formed by slip on their subjacent thrusts out of sequence basement rooted thrusts as the interpretations in the constructed cross sections suggest have breached the cover basement interface and using incompetent cover strata for propagation cut across the cover structures and have created associated new folds superimposed upon the pre existing structures this style of deformation which has resulted in structural complexity of the belt characterizes a 200 to 300 km wide zone of distributed partly synchronous deformation with along strike and across strike variations it also implies that the zagros fold thrust belt as the external part of the orogenic wedge is still in its subcritical condition with internal deformation to achieve a critical taper in creating structural complexity in addition to out of sequence thrusting mechanically weak layers evaporites and mudstones of the cover strata have played a significant role by providing several detachment horizons shortening estimates across the belt are variable based on the constructed cross sections and their restorations minimum shortening estimates range from 16 percent to 30 percent in different sectors of the belt

tectonic controls on residual oil saturation below the present day fluid contact level in reservoirs of the persian gulf abstract the presence of residual oil below the present day free water level fwl and oil water contact owc is common in many oil fields in the middle east particularly those in the persian gulf this residual oil is seen in both clastic and carbonate reservoirs prior to the start of production the characterisation and modelling of these fields is difficult in practice also these residual oils below the fwl and owc could become classified as reserves if ways to produce them could be found however the first step is to better understand their origin therefore the goal of this study was to investigate the role of geological events on the presence of the residual oil zone roz below the fwl and owc it has been suggested that the presence of residual oil below the present day fwl and owc is related to the geotectonic history of the region from the middle miocene reverse faulting and overfolding propagated over the zagros leading to the amplification of folds and the migration of the zagros orogeny towards its foreland basin persian gulf in response to this additional massive loading on the continental margin the forebulge amplitude was increased its location migrated towards the uplifted zagros mountains and consequently the persian gulf became narrower this exerted a north to north east downward tilting of the entire basin including all the structures and reservoirs previously filled by hydrocarbons this basin tilting changed the equilibrium of the structures and their fluid contents and resulted in the hydrocarbons and water attempting to find a new equilibrium under these conditions the early migrated and accumulated oil was flushed out by water imbibition and a roz was left below the present day fwl and owcs the angle of regional basin tilt has been calculated to be 0 836 based on seismic sections

tectonics versus eustatic control on supersequences of the zagros mountains of iran abstract at least 12 km of strata ranging in age from the latest precambrian to the recent are exposed in the zagros mountains of iran this sedimentary cover is characterized by distinct stratal packages separated by major unconformities forming twelve supersequences they are informally named as 1 late precambrian cambrian hakhamanesh supersequence 2 ordovician kourosh supersequence 3 silurian camboojiyeh supersequence 4 devonian darioush supersequence 5 mississippian pennsylvanian khashayar supersequence 6 permian triassic ashk supersequence 7 jurassic farhad supersequence 8 early cretaceous mehrdad supersequence 9 late cretaceous ardavan supersequence 10 paleocene oligocene sassan supersequence 11 oligocene miocene ardeshir supersequence and 12 miocene pleistocene shapour supersequence these supersequences and their correlatives in neighboring areas have been used to infer tectonic events the dominant interpretation has been that local or regional epeirogenic movements were responsible for the formation of these supersequences unconformities are considered as indications that epeirogenic movements associated with tectonic events affected the area the present investigation provides an alternative to the established view of the phanerozoic supersequences of the zagros mountains a good correlation exists between the lithofacies of supersequences in the zagros mountains and the second order eustatic sea level changes deposition of deep water marine shales occurred during periods of eustatic sea level rise platform wide unconformities coincided with eustatic sea level lows in fact supersequences of the zagros mountains are nearly identical to those described from the north american craton and the russian platform suggesting that these stratal packages are global these observations suggest that supersequences of the zagros mountains formed by second order eustatic sea level changes and not by local or regional epeirogenic movements although tectonic events did not produce supersequences of the zagros mountains they influenced regional lithofacies patterns through the formation of intrashelf depressions such as the hormoz salt basin during the precambrian and the dezful embayment and the lorestan basin during the mesozoic tectonic events also affected sedimentation during the tertiary collision of arabia and the central iran microplate through uplift erosion and the formation of the zagros foreland basin the results of this investigation necessitate a re evaluation of the role and the significance of pre tertiary tectonic events commonly used to interpret the geological evolution of the zagros mountains

chronology of trap formation and migration of hydrocarbons in zagros sector of southwest iran sixty three orogenically controlled oil and gas fields have been discovered in the zagros sector of southwest iran since the turn of the present century most of the fields are giant multi reservoir accumulations producing from fractured carbonate pay zones ranging in age from permo triassic to oligo miocene the most prolific oil producing zones are the asmari formation oligo miocene and the bangestan group upper cretaceous the available geochemical evidence indicates that the major source of the oil is the underlying lower cretaceous albian kazhdumi formation it is argued that in the main oil producing area the kazhdumi source rock was not buried to the depth required for hydrocarbon generation until the eocene and that no significant oil expulsion took place until the miocene entry of oil into the reservoirs is geologically a recent event it postdates the late miocene holocene zagros orogeny that resulted in the formation of the present structural traps it is suggested that the development of growth structures during the late cretaceous and paleogene could have contributed to some hydrocarbon localization prior to the formation of the late tertiary traps

modeling the flexural evolution of the amiran and mesopotamian foreland basins of nw zagros iran iraq the evolution of the amiran and mesopotamian flexural basins of the zagros belt is approached by coupled 2 d forward modeling of orogenic wedge formation lithospheric flexural isostasy and stream power erosion transport sedimentation thrust geometries and sequence of emplacement derived from geometric and kinematic models presented here are the inputs to our evolutionary model constrained by basin geometry sediment volume and topography modeling results confirm that the zagros flexural basins evolution is consistent with two stages of deformation 1 the obduction stage involving the kermanshah accretionary complex and a basement unit and 2 the collision stage emplacing the gaveh rud and sanandaj sirjan domains in the hinterland and forming a basement duplex in the outer part results provide quantitative insights into processes involved in mountain and basin building the lithospheric equivalent elastic thickness te changed from 20 km during the amiran stage 90 50 ma to 55 km during the mesopotamian subsidence stage last 20 myr the amiran basin results from flexure of the arabian plate below the load of the kermanshah cover and basement thrust sheets during this stage material eroded in the inner parts was enough to fill the flexural trough the mesopotamian basin formed in front of the outermost basement units flexing the arabian plate during this latter stage material eroded from the orogenic wedge was not enough to fill the mesopotamian basin an additional longitudinal sediment supply of up to 200 m myr is required to fill the flexural basin

late cenozoic and modern stress fields in the western fars iran implications for the tectonic and kinematic evolution of central zagros 1 the zagros iran developed during mio pliocene times in response to arabia eurasia convergence the western fars highlights a major bend of the deformation front and displays a remarkable set of nearly n s right lateral strike slip faults the kazerun borazjan karebass sabz pushan sarvestan faults oblique at high angle to the belt the region likely plays a major kinematic role by accommodating the change in shortening modes from partitioned in the western central zagros to nonpartitioned in the eastern zagros the inversion of focal mechanisms from small and moderate earthquakes shows a consistent n020 030 compression with a low ratio between differential stresses this regime accounts for the combination of strike slip and thrust type mechanisms through likely 2 3 permutations fault slip analysis reveals two successive late cenozoic regional compressional trends ne sw then n020 the latter is in good agreement with the present day stress the significance of the ne sw compression is discussed alternatively in terms of stress deviations or block rotations in relation to the strike slip fault system fieldwork and satellite imagery suggest that these faults behave first as transfer faults during folding of the cover and later as strike slip faults in agreement with the succession of stress regimes and the evolution of the dominant deformation style from thin skinned to thick skinned the first order stability of the collision related state of stress since 5 ma supports that the arabia eurasia convergence did not give rise to partitioning in the western fars but rather was and is still accommodated by distributed deformation involving both shortening and strike slip motion throughout the cover and the basement

the embryonic himalayan foreland basin revealed in the eastern yarlung zangbo suture zone southeastern tibet abstract understanding of early foreland basin development is key to reconstruct the timing and nature of early collisional processes though the nature of the early himalayan foreland basin system is well established in the central himalaya range it lacks analysis in the eastern yarlung zangbo suture zone in this article we investigate the region s lithological and structural evolution and analyze the geochemistry and geochronology of detrital zircons and bulk rocks in the jiacha jindong region southeastern tibet we show that 1 the previously named cretaceous langxian melange comprises two separate stratigraphic units the newly revised early eocene 56 ma langxian unit and the triassic langjiexue group 2 the langxian unit overthrusts the oligocene to miocene dazhuka formation and is overlain and or underlain by the highly deformed langjiexue group 3 shale normalized ree y patterns of marbles with light ree depletion la enrichment and positive y anomaly plus sr isotope ratios 0 707481 0 707897 together demonstrate the langxian unit was originally deposited in a marine environment 4 1270 concordant detrital zircons from 20 rock samples indicate a bilateral provenance from both the gangdese arc and or recycled forearc strata in the north and the langjiexue group in the south the evidence illustrates that the langxian unit records the early india asia collision and its protoliths could have been deposited in a distal foredeep basin to the embryonic eastern himalaya orogeny the simplest explanation is that it reflects an underfilled marine basin with sources from the early mountain range to the north and a region of forebulge erosion to the south

introduction geodynamic evolution of the zagros this special issue of geological magazine presents a collection of 17 papers dealing with different aspects of the zagros orogen many though not all of these contributions were presented as part of a highly successful session devoted to the geodynamic evolution of the zagros belt at the european geosciences union general assembly 2010 in vienna austria the aim of this gathering was to assemble a broad group of earth scientists interested in the zagros orogen to discuss and disseminate new results and ideas efficiently this volume presents a collection of some of the diverse research that is currently being carried out in the zagros we believe that these studies contribute to the understanding of the geodynamic evolution of the zagros mountains in particular but in addition to orogenic processes in general

warm humid paleoclimate control of salinized lacustrine organic rich shale deposition in the oligocene hetaoyuan formation of the biyang depression east china abstract lacustrine organic rich shales are widely developed within the oligocene biyang depression in the nanxiang basin in east china and across southeast asia these shales have been proven as hydrocarbon source rocks of crude oil as well as sources and reservoirs of shale oil understanding the deposition of these shales is essential to reconstruct the paleoenvironment and paleoclimate during the oligocene in east china as well as target the potential shale oil resources based on x ray diffraction organic and inorganic petrologic organic and inorganic geochemical and stable isotopic analyses paleoenvironment paleoclimate and hydrocarbon potential of the lacustrine organic rich shales in the oligocene hetaoyuan formation were investigated the mineral composition of hetaoyuan formation organic rich shales is dominated by clay minerals followed by quartz plagioclase calcite dolomite pyrite and gypsum six lithotypes are identified including siltstone silty shale clay shale calcareous shale dolomite shale and massive mudstone the organic matter om of the organic rich shales is dominated by type i kerogen lamalginite maturity parameters tmax biomarker ratios and calculated vitrinite reflectance suggest that the om enters the oil window maturity high toc and generative potential together with high contents of brittle minerals including quartz plagioclase and carbonates reveal the oligocene hetaoyuan formation hold good to very good potential of shale oil exploitation six organic rich shale layers have been identified in the hetaoyuan formation shale layer 1 to 6 from top to bottom among them shale layers 5 and 3 hold the best shale oil potential and therefore be investigated in the present paper shale layer 5 was deposited in a semi deep lacustrine environment under the moderately warm humid paleoclimate further dividing into lower middle and upper units relatively low toc contents av 2 6 wt in the lower unit are probably caused by high sedimentation rate high bioproductivity under favorable preservation conditions led to relatively high toc contents av 3 6 wt in the middle unit less reducing conditions together with moderate low bioproductivity resulted in relatively low toc contents av 2 6 wt in the upper unit warm humid paleoclimate prevailed during deposition of shale layer 3 deepened water depth and formed a deep lacustrine environment the stratified water column led to stable anoxic condition and photic zone euxinia in the saline deep lacustrine environment which enabled the accumulation of high amounts of om av 4 9 wt toc under excellent preservation av hi 710 mg hc g toc the results of core scanning analysis indicate that formation of the laminated shales probably controlled by seasonal fluctuations of paleoclimate

correlating shelf carbonate evolutive phases with fluid expulsion episodes in the foredeep miocene northern apennines italy abstract in the miocene of the northern apennines of italy evolutionary phases of shallow water carbonates in wedge top basins are coeval with methane rich fluid expulsion episodes in the inner foredeep we identified four main correlative events primarily controlled by synsedimentary tectonics sediment input and climate cooling 1 a burdigalian tectonic phase determined the onset of shelfal sedimentation in wedge top areas and is correlated with an important episode of fluid expulsion in marly sediments of the inner foredeep croce di moggiona seep carbonates 2 the decrease of shelfal carbonate production and the increase of detrital input in the early langhian correspond with a second important episode of seep carbonate precipitation in the inner foredeep castagno d andrea 3 the demise of the carbonate shelf and the coeval expulsion of methane rich fluids in the inner foredeep vicchio and m citerna seep carbonates at the langhian serravallian boundary approximate the mi3b cooling event the lower temperatures associated with increased siliciclastic weathering led to the crisis of shallow water carbonate production whereas the pressure drop due to the eustatic fall may have triggered the gas charged fluid expulsion 4 the tectonic related uplift of frontal sectors of the wedge top basin led to the wide erosion of the burdigalian langhian carbonates and caused the precipitation of authigenic seep carbonates deruta seep both in the slope and the adjacent foredeep

neogene sediments and modern depositional environments of the zagros foreland basin system a sedimentological investigation of the neogene deposits of the zagros foreland basin in sw iran reveals a continuous and largely gradational passage from supratidal and sabkha sediments at the base represented by the gachsaran formation to carbonates and marine marls mishan formation with basal guri carbonate member followed by coastal plain and meandering river deposits agha jari formation and finally to braided river gravel sheets bakhtyari formation this vertical succession is interpreted to represent the southward migration of foreland basin depozones from distal foredeep and foredeep to distal wedge top and proximal wedge top respectively as the zagros fold thrust belt migrated progressively southward towards the arabian foreland this vertical succession bears a striking similarity to modern depositional environments and sedimentary deposits observed in the zagros region today where one passes from mainly braided rivers in the zagros mountains to meandering rivers close to the coast to shallow marine clastic sediments along the northern part of the persian gulf and finally to carbonate ramp and sabkha deposits along the southeastern coast of the persian gulf this link between the neogene succession and the modern day depositional environments strongly suggests that the major neogene formations of the zagros foreland basin are strongly diachronous as shown recently by others and have active modern day equivalents

post collisional deposits in the zagros foreland basin implications for diachronous underthrusting detailed sedimentology of the neogene foreland basin deposits is investigated and classified into 11 lithofacies associations with respect to their paleo sedimentary environments the foreland deposits reveal a single coarsening upward mega sequence with continuous passage from back bulge to forebulge foredeep and wedge top sedimentary environments the gachsaran deposits form the base of the foreland strata and consist mainly of three different lithofacies associations including fluvial marine and sabkha deposits in the eastern zagros in fars and are typically dominated with evaporites toward the west in the dezful and kirkuk embayments the mishan formation has three different shallow marine lithofacies associations in a vertical succession representing foredeep deposits in the eastern zagros which tapers toward the dezful embayment and disappears in iraq the agha jari distal wedge top deposits also contain three different lithofacies associations including delta deposits mostly in the fars tidal flat deposits in dezful and mesopotamia basin and continental fluvial deposits across the entire zagros the uppermost synorogenic bakhtiari formation represents proximal wedge top deposits and consists mainly of two main lithofacies associations including shallow marine and fluvial deposits within which the fluvial succession is divided into three sub lithofacies associations with respect to distance from the mountain front and hydraulic power of the river networks synthetizing sedimentary facies association with age constraints of the old foreland deposits near the zagros suture in the high zagros area suggests that a considerable part of the arabian plate has been removed at the northern edge by underthrusting and erosion moreover preservation of the young distal foreland deposits near the suture in the western zagros implies that the magnitude and rate of removal of the proximal foreland deposits have been inconstant along strike the belt and decreases toward the east

calcite twinning constraints on late neogene stress patterns and deformation mechanisms in the active zagros collision belt mechanically induced calcite twins in veins and host rocks of late cretaceous to miocene age in iran have been used to determine regional arabia eurasia collisional stresses a late folding stress regime with a compression oriented 025 15 has been identified across the zagros belt and the southern iranian plateau this late neogene stress pattern agrees with the current stress field determined from the focal mechanisms of basement earthquakes and suggests that the hormuz salt decollement poorly decouples the basement and cover stress fields our data show that the collisional state of stress has been relatively constant since ca 5 ma the magnitudes of the stresses obtained from the twinning analysis are unexpectedly low and to a first approximation they are constant across the zagros simply folded belt this result supports an overall mechanism of buckling of the detached zagros cover internal viscous plastic processes help to relieve stress within this cover thus lowering its seismogenic potential beyond these regional implications this study underlines the potential of paleostress analyses in constraining both the tectonics and the mechanics of ancient and active foreland fold belts

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

folding style of the dezful embayment of zagros belt signatures of detachment horizons deep rooted faulting and syn deformation deposition abstract defining the governing factors on the geometry of the dezful embayment folds a major oil province in the zagros fold thrust belt in sw iran reduces the risks inherent in hydrocarbon exploration the goal of the current study is to find a reasonable relationship between folding and faulting in the northern part of the dezful embayment the role of major and minor detachment horizons and deep rooted faults on structural style is also a matter of investigations to achieve these goals geological surface information and the available well and 2d and 3d seismic data were used to construct a balanced structural cross section the area is subdivided into ne and sw sectors based on dissimilar physiographic features of the surface and structural and stratigraphic characteristics in the both sectors the miocene gachsaran formation acted as the upper detachment horizon in the ne sector the role of the gachsaran formation as major detachment horizon in decoupled folding styles of overlying and underlying units is prominent the gachsaran formation becomes less effective as a detachment horizon towards the sw as its thickness decreases and its facies change the triassic dashtak formation is most probably a major detachment horizon in the study area and evidence of another deeper detachment horizon such as the pre cambrian cambrian hormuz series is not apparent based on available data the lower cretaceous garau upper cretaceous gurpi and paleocene eocene pabdeh formations and the oligocene kalhur member are subordinate detachment horizons the role of major faults in the area such as the mountain front fault in driving thick skinned deformation is taken into account along with the dominant thin skinned deformation in the study area the kuh e asmari anticline is the only emergent anticline exposing the paleocene strata due to the activity of the deep rooted lahbari thrust this study reveals the commanding role of the upper detachment gachsaran formation and the overlying syn deformation fluvial clastics of the aghajari miocene and bakhtyari pliocene formations on disharmonic folding styles

palynology and petroleum potential of the kazhdumi formation cretaceous albian cenomanian in the south pars field northern persian gulf abstract the kazhdumi formation of the bangestan group is a well known source rock that has produced abundant oil in most petroleum fields in the zagros basin which stretches from northwest to southwest iran over hundreds of kilometres the formation reaches a thickness of 230 m at the type section in northwest zagros but thins out to 40 50 m in wells studied from the south pars giant petroleum field where it comprises mainly grey shales with occasional intercalations of marls and sandstones south pars best known as the iranian part of the world s largest non associated gas field contains small quantities of oil above and below the kazhdumi formation palynology has been used to assess the age and palaeoenvironment of the kazhdumi formation and to evaluate its petroleum potential a total of 68 ditch cutting samples recovered from five wells of which four are oil prone have been analyzed an age between late albian and cenomanian is established for the formation based on dinoflagellate cyst biostratigraphy and four palynofacies types have been recognized using the relative proportions of terrestrial elements marine palynomorphs and amorphous organic matter aom the ratio of terrestrial to marine elements is high in most samples indicating a nearshore sedimentary environment twenty two samples from the four oil prone wells were also selected for geochemical analysis using rock eval pyrolysis results show that the kazhdumi formation at south pars in contrast to the zagros basin is gas prone predominantly type iii kerogen thermally immature and poor in terms of hydrocarbon generation it could not have produced the oil in those oil prone wells studied

early neogene foreland of the zagros implications for the initial closure of the neo tethys and kinematics of crustal shortening we study the transition from passive margin to foreland basin sedimentation now exposed in the high zagros belt to provide chronological constraints on the initial stage of arabia eurasia collision and closure of the neo tethys we performed magnetostratigraphy and strontium isotope stratigraphy along two sections near the zagros suture which expose the oldest preserved foreland deposits the shalamzar section in the west and the dehmoord section in the east the top of the passive margin asmari formation has an age of 28 29 ma in the high zagros and is overlain by foreland deposits with a major basal unconformity representing 7 myr of hiatus the base of the foreland deposits has an age of 21 5 ma at dehmoord and ca 26 ma at shalamzar the sedimentation rate increased from 30 m myr in the passive margin to 247 m myr in the foreland combined with available age constraints across the zagros our results show that the unconformity is diachronous and records the southwestward migration of the flexural bulge within the arabian plate at an average rate of 24 2 mm yr over the last 27 ma the time evolution of sediment accumulation in the zagros foreland follows the prediction from a flexural model as the foreland is thrust beneath the orogenic wedge and loaded by the wedge and basin fill we detect the onset of forebulge formation within the asmari formation around 25 ma we conclude that closure of the neo tethys formed the zagros collisional wedge at 27 2 ma hence the arabia eurasia collision was probably not the main driver of global cooling which started near the eocene oligocene boundary ca 33 7 ma we estimate 650 km of forebulge migration since the onset of the collision which consists of 350 km of shortening across the orogen and 300 km of widening of the wedge and increasing flexural rigidity of arabia we conclude the average rate of shortening across the zagros to be ca 13 mm yr over the last 27 myr a value comparable to the modern rate palinspastic restoration of structural cross sections and crustal volume conservation comprise only ca 200 km of shortening across the zagros and metamorphic sanandaj sirjan belt implying that at least 150 km of the arabian crust was underthrust beneath eurasia without contributing to crustal thickening possibly due to eclogitization

tectono sedimentary framework of the gachsaran formation in the zagros foreland basin abstract continental collision between iranian and arabian plates resulted in the formation of the zagros fold thrust belt and its associated foreland basin during convergence pre existing faults in the basement were reactivated and the sedimentary cover was shortened above two different types of basal decollement viscous frictional this led to heterogeneous deformation which segmented not only the zagros fold thrust belt but also its foreland basin into different compartments resulting in variation in facies thickness and age of the sediment infill based on this concept a new tectono sedimentary model is proposed for one of the most important syn tectonic sedimentary unit the gachsaran salt in the zagros foreland basin in this proposed model it is argued that differential propagation of the deformation front above decollements with different mechanical properties viscous versus frictional results in along strike irregularity of the zagros deformation front whereas movement along pre existing basement faults leads to development of barriers across the zagros basin the irregularity of the deformation front and the cross basin barriers divided the zagros foreland basin into six almost alternating sub basins where gachsaran salt and its non salt equivalents are deposited in the salt sub basins two different processes were responsible for the deposition of gachsaran salt 1 evaporation and 2 dissolution of extruding hormuz salt and its re precipitation as gachsaran salt re precipitation was probably the most significant process responsible for the huge deposit of gachsaran salt in the extreme south east part of the zagros foreland basin

basin architecture and growth folding of the nw zagros early foreland basin during the late cretaceous and early tertiary abstract we present and use the chronostratigraphy of 13 field logs and detailed mapping to constrain the evolution of the early zagros foreland basin in nw iran large foraminifera calcareous nannofossil palynological and 87 sr 86 sr analysis supplied ages indicating a campanian early eocene age of the basin infill which is characterizd by a diachronous southwestward migrating shallowing upwards mixed clastic carbonate succession growth synclines and local palaeoslope variations indicate syndepositional folding from maastrichtian to eocene time and suggest forelandward migration of the deformation front we also illustrate the basin architecture with a synthetic stratigraphic transect from internal to external areas time lines cross the formation boundaries from continental kashkan red beds to taleh zang mixed clastic carbonate platforms amiran slope deposits and basinal gurpi pabdeh shales and marls the foreland basin depocentres show a progressive migration from the campanian to eocene c 83 52 7 ma with rates of c 2 4 mm a 1 during the early middle palaeocene c 65 5 58 7 ma increasing to c 6 mm a 1 during the late palaeocene earliest eocene c 58 7 52 8 ma coeval subsidence remained at c 0 27 mm a 1 during the first 12 7 ma and decreased to c 0 16 mm a 1 during the last 4 2 ma of basin filling finally we integrate our results with published large scale maps and discuss their implications in the context of the zagros orogeny supplementary material tables with dating results are available at http www geolsoc org uk sup18439

forward propagation of the zagros simply folded belt constrained from magnetostratigraphy of growth strata the temporal evolution of the zagros simply folded belt is constrained by a magnetostratigraphic sequence containing a progressive unconformity on the southern limb of the kuh e ghol ghol anticline in the central fars the investigated similar to 1400m thick sequence exposes a regressive megacycle containing from bottom to top open and shallow marine marls and sandy limestones fine to coarse grained fluvial deposits and alluvial conglomerates correlating the magnetostratigraphic section with the geomagnetic polarity time scale constrains the transition from marine to fluvial sediment deposition at similar to 6ma this transition was accompanied by a change in the accumulation rate from similar to 15cm ka to similar to 40cm ka as measured on lithified sediments alluvial river deposits first occurred at similar to 3 2ma the kuh e ghol ghol anticline began to grow at similar to 3 8ma witnessing fastest limb rotation rates of 40 degrees ma at similar to 3 3ma reporting magnetostratigraphic sections and ages of growth strata on a map of ne fars reveal an similar to 1cm a southwestward migration rate of the deformation front during the middle and late miocene

revised age of proximal deposits in the zagros foreland basin and implications for cenozoic evolution of the high zagros the regionally extensive coarse grained bakhtiyari formation represents the youngest synorogenic fill in the zagros foreland basin of iran the bakhtiyari is present throughout the zagros fold thrust belt and consists of conglomerate with subordinate sandstone and marl the formation is up to 3000 m thick and was deposited in foredeep and wedge top depocenters flanked by fold thrust structures although the bakhtiyari concordantly overlies miocene deposits in foreland regions an angular unconformity above tilted paleozoic to miocene rocks is expressed in the hinterland high zagros the bakhtiyari formation has been widely considered to be a regional sheet of pliocene pleistocene conglomerate deposited during and after major late miocene pliocene shortening it is further believed that rapid fold growth and bakhtiyari deposition commenced simultaneously across the fold thrust belt with limited migration from hinterland ne to foreland sw thus the bakhtiyari is generally interpreted as an unmistakable time indicator for shortening and surface uplift across the zagros however new structural and stratigraphic data show that the most proximal bakhtiyari exposures in the high zagros south of shahr kord were deposited during the early miocene and probably oligocene in this locality a coarse grained bakhtiyari succession several hundred meters thick contains gray marl limestone and sandstone with diagnostic marine pelecypod gastropod coral and coralline algae fossils foraminiferal and palynological species indicate deposition during early miocene time however the lower miocene marine interval lies in angular unconformity above 150 m of bakhtiyari conglomerate that in turn unconformably caps an oligocene marine sequence these relationships attest to syndepositional deformation and suggest that the oldest bakhtiyari conglomerate could be oligocene in age the new age information constrains the timing of initial foreland basin development and proximal bakhtiyari deposition in the zagros hinterland these findings reveal that structural evolution of the high zagros was underway by early miocene and probably oligocene time earlier than commonly envisioned the age of the bakhtiyari formation in the high zagros contrasts significantly with the pliocene quaternary bakhtiyari deposits near the modern deformation front suggesting a long term 20 myr advance of deformation toward the foreland

present day crustal deformation and plate kinematics in the middle east constrained by gps measurements in iran and northern oman summary a network of 27 gps sites was implemented in iran and northern oman to measure displacements in this part of the alpine himalayan mountain belt we present and interpret the results of two surveys performed in 1999 september and 2001 october gps sites in oman show northward motion of the arabian plate relative to eurasia slower than the nuvel 1a estimates e g 22 2m m yr 1 at n8 5 e instead of 30 5 mm yr 1 at n6 e at bahrain longitude we define a gps arabia eurasia euler vector of 27 9 0 5 n 19 5 1 4 e 0 41 0 1 myr 1 the arabia eurasia convergence is accommodated differently in eastern and western iran east of 58 e most of the shortening is accommodated by the makran subduction zone 19 5 2m m yr 1 and less by the kopet dag 6 5 2m m yr 1 west of 58 e the deformation is distributed in separate fold and thrust belts at the longitude of tehran the zagros and the alborz mountain ranges accommodate 6 5 2m m yr 1 and 8 2m m yr 1 respectively the right lateral displacement along the main recent fault in the northern zagros is about 3 2m m yr 1 smaller than what was generally expected by contrast large rightlateral displacement takes place in northwestern iran up to 8 mm yr 1 the central iranian block is characterized by coherent plate motion internal deformation 2m m yr 1 sites east of 61 e show very low displacements relative to eurasia the kinematic contrast between eastern and western iran is accommodated by strike slip motions along the lut block to the south the transition zone between zagros and makran is under transpression with right lateral displacements of 11 2m m yr 1

effect of spatial distribution of hormuz salt on deformation style in the zagros fold and thrust belt an analogue modelling approach scaled analogue models of thin skinned simultaneous shortening above adjacent viscous and frictional decollements simulate the effect of hormuz salt on the shortening in the zagros fold and thrust belt the models consisted of sand layers that partly overlay a viscous layer of silicone and were shortened from one end spatial distribution of the viscous decollement varied along strike and dip as occurs in part of the zagros fold and thrust belt in this belt phanerozoic sedimentary cover was shortened partly above the hormuz salt lying on the precambrian crystalline basement behaving as a basal viscous decollement model results display how the nature of the decollement affects the evolution of an orogenic belt using model results we explain the development of deflection zones and discuss strain partitioning formation of different topographic wedges and differential sedimentation along the zagros fold and thrust belt model results suggest the formation of a gentle taper consisting of both foreward and backward thrusts above a viscous decollement and a relatively steeper taper consisting only of forward vergent imbricates above a frictional decollement however in our models the steepest wedge with the highest topography formed where the viscous substrate had a limited extent with a transitional boundary pinch out perpendicular to the shortening direction shortening of this boundary led to development of frontal ramps associated with significant uplift of the area behind the deformation front

arabia eurasia collision and the forcing of mid cenozoic global cooling the end of the eocene greenhouse world was the most dramatic phase in the long term cooling trend of the cenozoic era here we show that the arabia eurasia collision and the closure of the tethys ocean gateway began in the late eocene at 35 ma up to 25 million years earlier than in many reconstructions we suggest that global cooling was forced by processes associated with the initial collision that reduced atmospheric co2 these are 1 waning volcanism across southwest asia 2 increased organic carbon storage in paratethyan basins e g black sea and south caspian 3 increased silicate weathering in the collision zone and 4 a shift towards modern patterns of ocean currents associated with increased vigour in circulation and organic productivity

late cenozoic reorganization of the arabia eurasia collision and the comparison of short term and long term deformation rates the arabia eurasia collision deforms an area of 3 000 000 km2 of continental crust making it one of the largest regions of convergent deformation on earth there are now estimates for the active slip rates total convergence and timing of collision related deformation of regions from western turkey to eastern iran this paper shows that extrapolating the present day slip rates of many active fault systems for 3 7 million years accounts for their total displacement this result means that the present kinematics of the arabia eurasia collision are unlikely be the same as at its start which was probably in the early miocene 16 23 ma or earlier in some but not all active fault systems short term 10 year and long term 5 million year average deformation rates are consistent there is little active thickening across the turkish iranian plateau and possibly the interior of the greater caucasus these are two areas where present shortening rates would need more than 7 million years to account for the total crustal thickening and where there are structural and or stratigraphic data for pre late miocene deformation we suggest that once thick crust up to 60 km built up in the turkish iranian plateau and the greater caucasus convergence took place more easily by crustal shortening in less elevated regions such as the zagros simple folded zone the south caspian region and foothills of the greater caucasus or in other ways such as westward transport of turkey between the north and east anatolian faults the time and duration of this changeover are not known for certain and are likely be diachronous although deformation started or intensified in many of the currently active fault systems at 5 2 ma

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

orogenic plateau growth expansion of the turkish iranian plateau across the zagros fold and thrust belt 1 this paper shows how the turkish iranian plateau grows laterally by incrementally incorporating adjacent parts of the zagros fold and thrust belt the limit of significant seismogenic thrusting in the zagros mw 5 occurs close to the regional 1250 m elevation contour the seismicity cutoff is not a significant bedrock geology boundary elevations increase northward toward regional plateau elevations of 2 km implying that another process produced the extra elevation between the seismogenic limit of thrusting and the suture this process is a plausibly ductile thickening of the basement suggesting depth dependent strain during compression similar depth dependant crustal strain may explain why the tibetan plateau has regional elevations 1500 m greater than the elevation limit of seismogenic thrusting at its margins we estimate 68 km shortening across the zagros simply folded belt in the fars region and 120 km total shortening of the arabian plate the dezful embayment is a low strain zone in the western zagros deformation is more intense to its northeast in the bakhtyari culmination the orogenic taper across strike topographic gradient across the dezful embayment is 0 0004 and across the bakhtyari culmination 0 022 lateral plateau growth is more pronounced farther east fars where a more uniform structure has a taper of 0 010 up to elevations of 1750 m a 100 km wide region of the zagros further northeast has a taper of 0 002 and is effectively part of the turkish iranian plateau internal drainage enhances plateau development but is not a pre requisite aspects of the seismicity structure and geomorphology of the zagros do not support critical taper models for fold and thrust belts

analogue modeling of the role of multi level decollement layers on the geometry of orogenic wedge an application to the zagros fold thrust belt sw iran the presence of evaporate and incompetent formations i e decollement horizons within the sedimentary sequence of fold thrust belts can control their structural style and deformation evolution in the present study the influence of the decollement layers e g basal and internal decollement layers on the deformation style of several segments of the zagros fold thrust belt zftb sw iran e g fars arc dezful embayment and izeh zone was investigated using a series of analogue models of accretionary wedges the study of seismic profiles to understand the structural evolution of these segments of the belt where several decollement intervals acted as basal and internal decollements is complemented by the analogue model results the experimental results reveal that the thickness of the internal decollement layers influences the creation of fold dominated or thrust dominated deformations respectively experimental models and seismic data highlight that incompetent layers act as barrier units against fault propagation in sequence and or out of sequence faults into overlying strata towards southwest by fore deformation and control the rate of deformation propagation in the zftb the presence of both the basal and internal decollement layers located at different stratigraphic levels is required to form disharmonic decollement folds in the foreland of the zftb in addition the geometry spacing activity and propagation of faults as well as the topographic height of the critical wedges are directly controlled by low frictional decollements geophys j int 165 1 336 356 2006 geochem geophys geosyst 14 1131 1155 2013 the seismic profiles of the zftb showed that in addition to lithological contrasts the existence and activity of deep seated and basement faults had a big impact on the structural styles of the region

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

study of hydrocarbon generation and 1d 2d modeling of hydrocarbon migration at the karanj and parsi oilfields southern dezful embayment sw iran abstract this study is a 2d basin modeling to determine the petroleum system i e cretaceous neogene play of the karanj and parsi oilfields in the southern dezful embayment sw iran this system is characterized by occurrence of source rocks of middle cretaceous late cretaceous and paleocene to eocene kazhdumi pabdeh and gurpi formation reservoirs of upper cretaceous and late oligocene early miocene ilam sarvak and asmari formations and seals of paleocene and miocene pabdeh and gachsaran formation considering temperature transformation ratio and vitrinite reflectance the maturity of source rocks kazhdumi pabdeh and gurpi formation was investigated a maturity history analysis showed that the maturity of kazhdumi pabdeh and gurpi formation started during 70 60 and 4 ma respectively generation and expulsion of hydrocarbons started 16 ma in the kazhdumi formation and 3 ma in the pabdeh formation that continued up to the present the analysis of the transformation ratio indicates transformation of significant amounts of kazhdumi source rocks for generating hydrocarbons migration of hydrocarbons from the kazhdumi formation is mainly vertically upward from pabdeh formation migration is both vertically upward to the asmari reservoir and downwards to the ilam sarvak reservoir however some local traps have formed due to the hydrocarbon accumulation above the faults our results reveal that petroleum generation migration and entrapment occurred at proper timing which facilitated the migration of hydrocarbons and their accumulation in the reservoirs