style and timing of salt movement in the persian gulf basin offshore iran insights from halokinetic sequences adjacent to the tonb e bozorg salt diapir abstract the variations in the rate of salt rise is reflected in the sedimentary sequences adjacent to salt diapirs and provides insights into the style of salt movement sedimentation interaction and the timing of halokinetic phases episodic movement of salt diapir is defined by wedge and tabular shaped salt related sedimentary strata halokinetic sequences adjacent to the diapir detailed mapping of depositional strata on 2d seismic sections adjacent to salt diapirs on the tonb e bozorg island persian gulf sw iran reveals the presence of a series of sedimentary sequences related to the halokinetic activity of two salt source layers the hormuz and fars salts respectively the hormuz salt deposited in the uppermost proterozoic mobilized in the lower paleozoic and then continued to move periodically to present and to create the deep salt structures in the tonb e bozorg region the fars salt deposited in the lower miocene and then started rising and created the central salt structure the tonb e bozorg island and several peripheral ring like salt structures around the island our results reveal that both the salt layers within the tonb e bozorg region grew by downbuilding and continued to move periodically by passive and active diapirism to the present salt movement sedimentation interaction during salt diapirism influences petroleum play and therefore is of interest in petroleum geoscience

latest pleistocene and holocene glacier fluctuations in the himalaya and tibet abstract the timing and extent of latest pleistocene and holocene alpine glacier fluctuations in the himalaya and tibet are poorly defined due to the logistical and political inaccessibility of the region and the general lack of modern studies of the glacial successions nevertheless renewed interest in the region and the aid of newly developing numerical dating techniques have provided new insights into the nature of latest pleistocene and holocene glacier oscillations these studies provide abundant evidence for significant glacial advances throughout the last glacial cycle in most high himalayan and tibetan regions glaciers reached their maximum extent early in the last glacial cycle however true last glacial maximum glacier advances were significantly less extensive notable glacier advances occurred during the lateglacial and the early holocene with minor advances in some regions during the mid holocene there is abundant evidence for multiple glacial advances throughout the latter part of the holocene although these are generally very poorly defined and were less extensive than the early holocene glacier advances the poor chronological control on latest pleistocene and holocene glacial successions makes it difficult to construct correlations across the region and with other glaciated regions in the world which in turn makes it hard to assess the relative importance of the different climatic mechanisms that force glaciation in this region the lateglacial and holocene glacial record however is particularly well preserved in several regions notably in muztag ata and kongur and the khumbu himal these successions have the potential to be examined in detail using newly developing numerical dating methods to derive a high resolution record of glaciation to help in paleoclimatic reconstruction and understanding the dynamics of climate and glaciation in the himalaya and tibet

tertiary of the arabian gulf sedimentology and hydrocarbon potential abstract the paleogene neogene paleogeography of the arabian basin shows a change from the basic continuation of the mesozoic pattern during the paleogene to a new pattern of sedimentation established during the neogene and resulting from movements in the zagros the paleogene shallow water carbonate dominated lithologies in eastern arabia were replaced by deep water neogene carbonates near the zagros and mixed carbonate and clastics in the northern arabian gulf the hydrocarbon potential of these rocks except locally is low and the decreasing amplitude and frequency of faulted and folded structures away from the zagros front suggests that the discovery of fields in structures such as those in iraq iran is low this poverty may however suggest that the untapped potential of the mesozoic rocks may still be high

evolution of the stress fields in the zagros foreland folded belt using focal mechanisms and kinematic analyses the case of the fars salient iran the nw se trending zagros orogenic belt was initiated during the convergence of the afro arabian continent and the iranian microcontinent in the late cretaceous ongoing convergence is confirmed by intense seismicity related to compressional stresses collision related in the zagros orogenic belt by reactivation of an early extensional faulting to latter compressional segmented strike slip and dip slip faulting these activities are strongly related either to the deep seated basement fault activities deep seated earthquakes underlies the sedimentary cover or gently dipping shallow seated decollement horizon of the rheological weak rocks of the infra cambrian hormuz salt the compressional stress regimes in the different units play an important role in controlling the stress conditions between the different units within the sedimentary cover and basement a significant set of nearly n s trending right lateral strike slip faults exists throughout the study area in the fars area in the zagros foreland folded belt fault slip and focal mechanism data were analyzed using the stress inversion method to reconstruct the paleo and recent stress conditions the results suggest that the current direction of maximum principal stress averages n19 e with n38 e that for the past from cretaceous to tertiary although a few sites on the kar e bass fault yield a different direction the results are consistent with the collision of the afro arabian continent and the iranian microcontinent the difference between the current and paleo stress directions indicates an anticlockwise rotation in the maximum principle stress direction over time this difference resulted from changes in the continental convergence path but was also influenced by the local structural evolution including the lateral propagation of folds and the presence of several local decollement horizons that facilitated decoupling of the deformation between the basement and the sedimentary cover the obliquity of the maximum compressional stress into the fault trends reveals a typical stress partitioning of thrust and strike slip motion in the kazerun kar e bass sabz pushan and sarvestan fault zones that caused these fault zones behave as segmented strike slip and dip slip faults

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

cretaceous sequence of deformation in the se zagros fold thrust belt several major zones across the zagros fold thrust belt have been interpreted as indicating that orogeny took place progressively from ne to sw through discrete orogenic episodes during tertiary time this paper uses field evidence of growth onlaps and angular unconformities within the cretaceous stratigraphic column as well as existing geological maps and cross sections to indicate that deformation started as early as the late aptian and folded the whole width of the zagros belt simultaneously later events are indicated by folding at the end of the cenomanian and in the late turonian and santonian following the late cretaceous deformation phases the se zagros basin was divided into several longitudinal intra shelf basins which were separated by nw se trending cretaceous anticlines however with reference to our previous work it can be suggested that each of the sub basins was folded serially from ne to sw through a series of tectonic phases during the next episode of zagros orogeny in tertiary time the change of deformation style from concomitant to serial folding during the cretaceous and tertiary respectively is attributed to the existence of the hormuz salt and shearing at the base of the former basin and its absence at the base of the tertiary intra shelf basins

late pleistocene holocene hydrologic changes in the interfluve areas of the central ganga plain india abstract abandoned channel belts ponds and point bar deposits of palaeochannels in the interfluve regions of the central ganga plain suggest changes in the morphohydrologic conditions during the latest pleistocene holocene stratigraphy of these ponds comprises channel sand at the base overlain by shell bearing clayey silt the contact of the two facies marks the phase when channels converted into standing water bodies point bar deposits of some palaeochannels are overlain by oxidised aeolian sand indicating that the channel abandonment possibly occurred due to the desiccation and aridity in the region optically stimulated luminescence osl chronometry of the pond sediments suggests that the deposition of the basal channel sand started before 13 ka and continued up to 8 ka the ponds formed around 8 6 ka when the channel activity ceased evidence from the point bar deposits also indicates that the fluvial activity in the region ended sometime during 7 5 ka this was followed by aeolian aggradation the present study thus suggests that the hydrologic conditions in the gangetic plains i e initiation of channels and their abandonment formation of microgeomorphologic features such as ponds and their eventual siltation were controlled largely by climatic changes i e monsoon changes supported by tectonic activity for the past 2 ka increasing human and related agricultural activity has substantially accentuated the natural siltation rate of ponds

evolution and timing of salt diapirism in the iranian sector of the persian gulf abstract the iranian sector of the persian gulf is affected by more than 30 large diapiric structures triggered by the mobilization of the infracambrian hormuz complex an evaporite rich unit that overlies precambrian basement at the base of the sedimentary succession nineteen non piercing diapirs without any appreciable salt intrusion into the upper succession were studied in detail and retro deformed by the decompaction and unfolding of 13 seismic horizons that were identified by the interpretation of a dense grid of 2d seismic lines and calibrated by well data salt uplift had begun by the early palaeozoic and persists to the present day with major pulses of intensity during the middle triassic cenomanian late oligocene and post middle miocene the structural reconstructions and the analysis of the progressive deformation of the study diapirs do not show any link between diapiric uplift and local tectonic structures and no clear correlation with the regional geodynamic events acting at the boundary of the arabian plate on the contrary the salt uplift seems strongly influenced by the differential rate of sedimentation that affected the whole study basin more than 40 000 km 2 with a coefficient of correlation between the salt uplift rate and the differential rate of sedimentation expressed by the standard deviation of the sedimentation rate calculated over the entire basin of 0 95 this downbuilding mechanism of diapiric growth is apparently induced by differential sedimentation over long distances several tens of kilometers showing that the flow of salt affected the whole basin and not just the areas around the single diapiric structures

late cretaceous miocene sedimentary development of the arabian continental margin in se turkey adiyaman region implications for regional palaeogeography and the closure history of southern neotethys abstract the middle cretaceous late miocene sedimentary successions that are exposed on the arabian continental margin near adiyaman provide valuable insights into sedimentary tectonic and climatic processes that affected the southern neotethys and its continental margins deposition in the region began with aptian early campanian shelf carbonates followed by deepening during the mid campanian lithoclastic bioclastic turbidites accumulated along the downfaulted northern margin of the arabian platform during the campanian a flexurally controlled foredeep developed in advance of the emplacement of mesozoic allochthonous continental margin and oceanic rocks during the latest campanian early maastrichtian e g supra subduction zone kocali ophiolite alluvial detritus was shed from the emplaced allochthon in non marine to shallow marine deltaic settings during latest campanian early maastrichtian a marine transgression resulted in the establishment of a shallow marine shelf during the mid maastrichtian during the latest maastrichtian the platform submerged initiating deeper water hemipelagic sedimentation uplift took place during the palaeocene resulting in sediment instability slumping and formation of high density subaqueous gravity flows in response to regional faulting and tilting some areas in the north and the southwest emerged during the early middle eocene generating alluvial fans in a warm humid climate that favoured oxidation and reddening the likely control of the tectonic instability was far field compression related to the latest stages of subduction of the southern neotethys or the initial stages of collision of the arabian and tauride continents an oligocene hiatus is likely to reflect the formation of a collision related forebulge followed by flexural subsidence to form an early miocene foreland basin this was finally over ridden by the northerly active continental margin of the southern neotethys during early mid miocene regional suture tightening mid late miocene and related non marine coarse clastic sedimentation was followed by westward tectonic escape of the anatolian microplate towards the aegean region during plio quaternary time

on the problem of quaternary glaciations and the extent and patterns of pleistocene ice cover in the qinghai xizang tibet plateau abstract data accumulated during investigations since the 1960s indicate that up to four pleistocene glaciations can be recognized in the qinghai xizang tibet plateau and the adjacent himalaya mountains in order of decreasing age these are the xixabangma nyanyaxungla guxiang and baiyu glacial episodes the history of pleistocene glacial evolution in various areas throughout the plateau differs and the pattern is very complex throughout the early pleistocene the elevation of the qinghai xizang plateau was approximately 2000 m above sea level during the xixabangma glacial episode recorded at higher elevations the climate and topographical conditions on the plateau were largely unfavourable for the development of glaciers present investigations have revealed that the oldest till is only found at isolated localities on the plateau glaciofluvial or alluvial deposits such as the gongba conglomerate dating from 2 4 to 0 73 ma bp and the fluvial lacustrine deposits of the qiantang group dating from 2 4 to 1 7 ma bp are present rather than glacial till therefore the postulate of a large early pleistocene ice sheet proposed previously has been disproves during the most recent glaciation uplift of the plateau and the himalayas continued the majority of the qinghai xizang plateau reached 4000 m a s l and the great himalaya were approximately 6000 m a s l the mountains formed a barrier against the incursion of the indian monsoon so that precipitation decreased sharply on the northern flank of the himalayas and the climate to the north became cold and dry all of the glaciers on the qinghai xizang plateau underwent extensive retreat thus during the pleistocene no unified glacial cover existed over the qinghai xizang plateau similarly the source area of the hwang he yellow river did not support a local ice sheet

late pleistocene holocene vegetation and indian summer monsoon record from the lahaul northwest himalaya india abstract the high resolution holocene paleomonsoon records from northwest nw himalaya are limited the carbon isotope 13 c total organic carbon toc and pollen analysis were therefore carried out from a peat lake sediment sequence developed in alpine meadows of the chandra valley lahaul nw himalaya in order to reconstruct centennial to millennial scale vegetational changes and indian summer monsoon ism variability during the holocene the chronology of peat lake sediments is constrained with 9 ams 14 c dates the recovered non arboreal pollen nap suggested that during holocene alpine desert steppe meadows and shrubs growing along the stream had developed in the lahaul valley whereas arboreal pollens ap e g pinus quercus cedrus and ulmus presently growing in the southern hill slopes of pir panjal range indicated moisture carrying monsoonal air flow from the south the increased 13 c and low toc values between 12 880 and 11 640 calibrated years before present cal yr bp suggested weakening of ism and low organic carbon production corresponding to the younger dryas yd cold event the gradual depletion in carbon isotope ratio from 11 640 to 8810 cal yr bp indicated enhanced precipitation in the chandra valley in response of increased ism strength in early holocene the short spell of cold and dry climate with gradual decrease in ism intensity between ca 10 398 and 9778 cal yr bp is closely linked with bond event 7 the other prominent cold dry events recorded in present study are i 8810 to 8117 cal yr bp roughly corresponding to global 8 2 ka cold event ii 4808 to 4327 cal yr bp closely preceding the global 4 2 ka cold arid period and iii 1303 to 1609 cal ad corresponding to little ice age lia event the expansion of thermophillous broad leaved taxa viz betula utilis alnus nepalensis quercus semicarpifolia and juglans regia and effective growth of meadow vegetation such as grasses caryophyllaceae and artemisia along with marshy elements i e polygonum and liliaceae between 6732 and 3337 cal yr bp marked warm and wet holocene climate optimum hco period the warm and moist climate from 1158 647 cal yr bp corresponded with global medieval warm period mwp

a reappraisal of earthquake focal mechanisms and active shortening in the zagros mountains of iran summary the zagros mountains of sw iran are one of the most seismically active intra continental fold and thrust belts on earth and an important element in the active tectonics of the middle east surface faulting associated with earthquakes is extremely rare and so most information about the active faulting comes from earthquakes we use long period teleseismic p and sh body waves to determine the orientation and depth of faulting in 16 new earthquakes and then evaluate and synthesize all the available teleseismic data on earthquake source parameters in the zagros we use this information to investigate the style and distribution of active faulting in the zagros and how it contributes to the n s shortening of the arabia eurasia collision when the data are ranked in quality and carefully evaluated simple patterns are seen that are not apparent when routine catalogue data are taken at face value an important change in the fault configuration occurs along strike of the belt in the nw overall convergence is oblique to the trend of the belt and the surface anticlines and is achieved by a spatial separation partitioning of the orthogonal strike slip and shortening components on separate parallel fault systems by contrast in the se overall convergence is orthogonal to the regional strike and achieved purely by thrusting in the central zagros between these two structural regimes deformation involves parallel strike slip faults that rotate about vertical axes allowing extension along the strike of the belt the overall configuration is similar to that seen in other curved shortening belts such as the himalaya and the java sumatra trench all the zagros earthquakes we have been able to check have centroids shallower than 20 km and are confined to the upper crust many of the larger earthquakes are likely to occur in the basement beneath the sedimentary cover which is active even beneath areas of known shallow structural decollement such as the dezful embayment the dominant style of shortening is high angle reverse faulting with dips 30 though some lower angle thrusting occurs in places active thrust and reverse faulting is relatively confined to the lower topography on the sw edge of the belt today and only strike slip faulting affects the higher topography profound vertical changes in structural and stratigraphic level indicate that a similar style of deformation was once active across the width of the simple folded belt but has progressively migrated sw over the last 5 ma there is no evidence for a seismically active structural decollement such as a low angle thrust beneath the zagros nor is there any seismic evidence for active subduction either beneath the zagros or beneath central iran instead the arabian margin seems to have shortened by distributed thickening of the basement only in the syntaxis of the oman line at the se end of the zagros is there any evidence for a low angle thrust of regional extent here earthquakes continue 50 km north of the zagros thrust line the geological suture between the arabian margin and central iran reaching depths of 30 km and may represent thrusting of arabian basement beneath central iran to this extent

using multi attribute neural networks classification for seismic carbonate fades mapping a workflow example from mid cretaceous persian gulf deposits abstract seismic facies mapping in large seismic surveys can be time consuming even if only a basic overview of the facies distribution is needed therefore this study outlines an approach for the use of volume based seismic attributes from 2d surveys for automated seismic facies mapping within carbonate settings the study area is located in the central persian gulf offshore iran the interval of interest is the mid cretaceous sarvak formation which is part of the extensive cretaceous shallow water carbonate platform of the eastern arabian plate a set of nine volume based seismic attributes calculated from time amplitude and frequency information of post stacked 2d seismic data was chosen to characterize geological information within the interval of interest the volume based attributes were supplemented by two grid based attributes to highlight structural elements the geological significance of each attribute was evaluated by comparing it with results of seismic sedimentological geomorphological studies furthermore statistical methods were applied to highlight direct relationships amongst the attributes the results of these tests were then used to choose a limited set of attributes for neural network based multi attribute classifications the results show that seismic attributes derived from 2d surveys can be used to map basic seismic facies types in carbonate settings and that the outlined general approach might be applied in other studies

late cretaceous to recent deformation related to inherited structures and subsequent compression within the persian gulf a 2d seismic case study abstract the persian gulf is part of an asymmetric foreland basin related to the zagros orogen few published studies of this basin and associated onshore areas include seismic reflection data we present a seismic stratigraphic interpretation based on marine 2d seismic data which reveals the presence of two types of compressional structures within the basin 1 faulted domes related to salt movement and the offshore trace of a nne ssw trending dextral basement fault the kazerun fault 2 long wavelength 16 km low amplitude 60 ms two way travel time folds relating to the advancing deformation front associated with the orogen thinning of age constrained stratal units across structures related to the offshore trace of the kazerun fault implies a distinct pulse of uplift on this fault during the maastrichtian the geometry of growth strata across other intra basin structures suggests a second later stage of deformation which began in the middle miocene thickening and folding of post middle miocene stratal units towards the ne i e towards the zagros orogen is interpreted to reflect rapid loading subsidence and compression related to southwestwards advance of the orogen the results of this study have implications for the interaction between pre existing structures and later compressional events both within the persian gulf and elsewhere

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

precipitation variability in the indian central himalaya during last ca 4 000 years inferred from a speleothem record impact of indian summer monsoon ism and westerlies abstract we report the first high resolution stalagmite record from indian central himalaya by using a combined oxygen and carbon isotopic study spanning the last 4000 years in addition to the multi decadal events the stalagmite data also provide information on the variability in the intensity of precipitation indian summer monsoon ism and westerlies in north indian hills during the late holocene the 18o values show strong variability between 2 1 and 8 9 the extremely high variability points to the monsoon from two different sources compared to other similar aged caves which are primarily controlled by one monsoon such as the east asian summer monsoon easm although ism has penetrated into some parts in the areas of easm in the past or the westerlies therefore we suggest that the westerlies played an important role in the late holocene climate of the indian himalaya as the source of the westerlies is mediterranean atlantic the north atlantic oscillation nao which was responsible for comparatively stronger westerlies in southern europe may have brought higher precipitation to the north indian hills the stronger westerlies may also have resulted in the highest precipitation between 0 5 and 0 25 ka bp 1450 1700 ad a part of the lia in contrast to the weakening of the indian summer monsoon ism in peninsular india the stalagmite has also recorded the driest period peaking at 3 2 ka bp which may be nearly synchronous with the final collapse of the harappan culture in northwest india

timing of late quaternary glaciations south of mount everest in the khumbu himal nepal moraines south of mount everest in the khumbu himal were dated using optically stimulated luminescence clustering of ages and morphostratigraphy allowed three advances to be dated 1 the periche glacial stage ca 18 25 ka 2 the chhukung glacial stage ca 10 ka and 3 the lobuche stage ca 1 2 ka the periche stage is coincident with oxygen isotope stage 2 the chhukung stage represents a late glacial or early holocene glacial advance and the lobuche stage is a late holocene glacial advance that predates the little ice age

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

forced folds and fractures this volume is concerned with defining the major similarities and difference between forced folds and buckle folds in order that these differences can be used to recognize the type of folding and therefore the expected fracture pattern present in regions of poor exposure or where the geologist has to rely on seismic images an understanding of the differences between the two fold types their 3d geometry spatial organization fracture patterns etc provides an invaluable tool for earth scientists concerned with assessing the possible role of folds and their associated fracture patterns in controlling fluid migration and concentration within the crust the papers presented here are grouped into 4 sections contributions in the first section describe the use of numerical analyses to investigate the formation of fractures in forced folds including compaction folds and the section contains a description of large scale compaction folding in which the associated fracturing has given rise to the development of large sandstone dykes the papers in the second section deal with the formation of forced folds as a result of normal faulting in various geological environments including along a classical graben margin and around a resurgent caldera the third section contains papers relating to forced folding in compressional and strike slip regimes the final section considers the temporal and spatial relationships between forced folds and buckle folds the formation of crustal scale folds and a method of determining the distribution of strain on any folded surface a key parameter controlling the distribution of fractures

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

gas venting and late quaternary sedimentation in the persian arabian gulf abstract high resolution 3 5 khz echo sounding profiles and piston cores were used to reconstruct the microtopography and late quaternary depositional history of the persian gulf perversive throughout the seafloor of the gulf is an extensive network of pockmarks formed by seepages of thermogenic gas these gas seeps and bottom water exiting the gulf via the strait of hormuz are the most significant processes controlling present day sedimentation in the region erosion by these seeps has been so intense in the baiban shelf in the strait of hormuz as to create a hoodoo like terrain on the outer shelf the surfical geology of the gulf documents a short lived transgression 29 400 to 22 800 years ago during the wisconsin regression which began 125 000 years ago the wisconsin regressive maxima when sea level dropped to 120 130 m about 21 000 20 000 years ago and the climate was dry and eolian and paralic sedimentation characterized the gulf the holocene transgression 18 000 to 12 000 years ago when the climate was more humid than during the climax of the wisconsin regression a dry phase 12 000 to 9000 years ago when the persian gulf was a site of eolian and carbonate deposition and the present sediment cycle during the last 9000 years under a more humid regime it was during the present cycle that southeast trending marl lobes were deposited off iran arabia acquired its hyper arid climate about 3000 years ago and the gulf attained its present configuration about 1000 years ago as a result of the construction of the tigris euphrates delta at its head and tectonism and aggradation along its arabian and iranian flanks

timing and extent of late quaternary glaciation in the western himalaya constrained by 10be moraine dating in garhwal india glacial chronologies from the himalayan region indicate various degrees of asynchronous glacial behavior part of this has been related to different sensitivities of glaciers situated in contrasting climatic compartments of the orogen but so far field data in support for this hypothesis is lacking here we present a new 10 be derived glacial chronology for the upper tons valley in western garhwal india and initial results for the pin and thangi valleys in eastern himachal pradesh these areas cover a steep gradient in orographic precipitation and allow testing for different climatic sensitivities our data provide a record of five glacial episodes at w16 ka w11 12 ka w8 9 ka w5 ka and 1 ka in the thangi valley our results indicate a glacial episode at w19 ka but no data are available for younger glacial deposits in this valley at their largest mapped extent w16 ka the two main glaciers in the upper tons valley joined and descended down to w2500 m asl which represents a drop of w1400 m compared to the present day glacial extent during the holocene the two largest glaciers produced distinct glacial landforms that allowed us to reconstruct changes in the equilibrium line altitude ela over w20 km north south distance that is presently associated with a steep gradient in rainfall we observe that ela changes have been consistently w2 times higher for the glacier located in a presently wetter climate pointing at different climate sensitivities related to the amount of precipitation that they receive at regional scale our data is in reasonable agreement with other published glacial chronologies from the western himalaya and suggest that glacial advances during the holocene have been largely synchronous in this region comparison of glacial chronologies from the western himalaya with other palaeoclimatic proxy data suggests that long term changes in glacial extents are controlled by glacial interglacial temperature oscillations related to the waxing and waning of the large northern hemisphere ice sheets while the timing of millennial scale advance and retreat cycles are more directly related to monsoon strength

seismic reflection imaging of karst in the persian gulf implications for the characterization of carbonate reservoirs karstification positively and negatively affects the quality of carbonate reservoirs for example dissolution and brecciation can increase porosity and permeability whereas cavern collapse or cementation driven by postkarstification fluid flow may occlude porosity and reduce permeability karst may also pose challenges to drilling because of the unpredictable and highly variable porosity and permeability structure of the rock and the corresponding difficulty in predicting drilling mud weight when combined outcrop petrographic and geochemical data can constrain the style distribution and origin of seismic scale karst which may provide an improved understanding of carbonate reservoir architecture and allow development of safer drilling programs however relatively few studies have used seismic reflection data to characterize the regional development of seismic scale karst features in this study we use time migrated two dimensional seismic reflection data to determine the distribution scale and genesis of karst in a 3 km thick 9800 ft thick jurassic miocene carbonate dominated succession in the persian gulf we map 43 seismic scale karst features which are expressed as vertical pipe columns of chaotic reflections capped by downward deflected depressions that are onlapped by overlying strata the columns are up to 2 km 6500 ft tall spanning the upper jurassic to upper cretaceous succession and are up to 5 5 km 18 000 ft in diameter we interpret these pipes to have formed in response to hypogene karstification by fluids focused along preexisting faults with hypogene generated depressions enhanced by epigene processes during key intervals of exposure our study indicates that seismic reflection data can and should be used in conjunction with petrographic and geochemical techniques to determine the presence of hypogene karst plays and to help improve the characterization of carbonate reservoirs and associated drilling hazards

late quaternary fluvial aggradation and incision in the monsoon dominated alaknanda valley central himalaya uttrakhand india the present study aims to explain the spatial and temporal variability in phases of aggradation incision in response to changes in climate and seismicity during the late quaternary in the alaknanda river valley a major tributary of the river ganges or ganga geomorphology stratigraphy and optical dating of the fluvial sediment reveal that the oldest fluvial landforms preserved in the south of the main central thrust are debris flow terraces developed during the early part of pluvial marine isotopic stage 3 following this a period of accelerated incision erosion owing to an increase in uplift rate and more intense rainfall occurred in the lesser himalaya three phases of valley fill aggradation around 26 3 ka 18 2 ka and 15 1 ka and 8 1 ka occurred in response to changes in monsoon intensity and sediment flux the last phase was regionally extensive and corresponds to a strengthening of the early holocene indian summer monsoon a gradual decline in the monsoon strength after 8 1 ka resulted in reduced fluvial discharge and lower sediment transport capacity of the alaknanda river leading to valley fill incision and the development of terraces the study suggests that fluvial dynamics in the alaknanda valley were modulated by monsoon variability and the role of tectonics was subordinate limited to providing accommodation space and post deposition modification of the fluvial landforms copyright 2010 john wiley sons ltd

source rock characterization of the cretaceous sarvak formation in the eastern part of the iranian sector of persian gulf cenomanian middle sarvak rock samples were collected from various parts of the eastern iranian sector of the persian gulf and analyzed for quantity quality maturity and depositional environment of the organic matter by rock eval pyrolysis gas chromatography gc gas chromatography mass spectrometry gc ms pyrolysis gas chromatography mass spectrometry py gc ms kerogen stable carbon isotopic signatures elemental composition and petrography the results indicate that the organic matter has mainly good to very good hydrocarbon generation potential corresponding to kerogen types i ii and ii s the maturity increases from immature in the western section to early mature in the eastern section of the study area in addition biomarker parameters indicate a marine carbonate depositional environment for the middle sarvak formation and deposition under anoxic condition according to hydrocarbon potential maturity and oil source rock correlation the middle sarvak is the main source rock charging the late cretaceous upper sarvak ilam reservoirs of south eastern part of the persian gulf

a note on the extent of glaciation throughout the himalaya during the global last glacial maximum abstract quantitative chronologies for the impressive glacial successions that occur throughout the himalaya have until recently been almost totally lacking within the last decade two new techniques have promised to remedy this situation these techniques optically stimulated luminescence and cosmogenic nuclide surface exposure dating enable the age of many glacial features to be determined and have allowed us to study the extent and timing of himalayan glaciation in the late quaternary new data show that the local last glacial maximum lgm occurred during the early part of the last glacial cycle in most areas during marine isotope stage 3 mis 3 mis 3 was a time of increased insolation when the south asian summer monsoon strengthened and penetrated further north into the himalaya the concomitant increased precipitation occurring as snow at high altitudes produced positive glacier mass balances thereby allowing glaciers to advance on the other hand during the global lgm 18 24 ka himalayan glaciation was very restricted in extent generally extending

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

asynchronous maximum advances of mountain and continental glaciers the last maximum glacier advance in many mountain ranges appears to have predated the last maximum advance of the wisconsinan continental ice sheets 20 000 years b p published evidence from widely spaced localities in north and south america europe asia and hawai i suggests that some mountain glaciers extended farther during one or more stades early in the last glaciation roughly 115 000 30 000 years b p than at its end when low global temperature and high precipitation presumably were most favorable for the growth of glaciers variations in the timing of glacier advances in different mountain ranges suggest that alpine glaciers are dependent on regional climate as well as global conditions their study might provide sensitive tests for theories of global climate change glacial deposits are often used as time markers in neotectonic and geomorphic studies and their ages sometimes are inferred from distant measurements or from proxy histories of global climate change undated geomorphic features such as moraines sharply incised streams and river terraces which commonly have been associated with the last maximum glacier advance 20 000 years b p or last deglaciation 13 000 years b p may actually be older by a factor of 2 to 4 or more conversely deposits assigned to the maximum advances of the penultimate global glaciation 130 000 years b p may actually date from early in the most recent glacial cycle and be younger by a comparable factor rates of faulting or folding estimated from displacements or deformation and the assumed ages of such geomorphic features might be too great or too small by corresponding factors

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

changes of the equilibrium line altitude since the little ice age in the nepalese himalaya changes of the equilibrium line altitude ela since the end of the little ice age lia in eastern nepal have been studied using glacier inventory data the toe to headwall altitude ratios thars for individual glaciers were calculated for 1992 and used to estimate the ela in 1959 and at the end of the lia thar for debris free glaciers is found to be smaller than for debris covered glaciers the elas for debris covered glaciers are higher than those for debris free glaciers in eastern nepal there is considerable variation in the reconstructed change in ela ela between glaciers within specific regions and between regions this is not related to climate gradients but results from differences in glacier aspect southeast and south facing glaciers show larger elas in eastern nepal than north or west facing glaciers the data suggest that the rate of ela rise may have accelerated in the last few decades the limited number of climate records from nepal and analyses using a simple ela climate model suggest that the higher rate of the ela between 1959 and 1992 is a result of increased warming that occurred after the 1970s at higher altitudes in nepal

himalayan glacial sedimentary environments a framework for reconstructing and dating the former extent of glaciers in high mountains abstract reconstructing paleoenvironmental change from glacial geologic evidence in the himalayas has been difficult because of the lack of organic material for radiocarbon dating and the problems of correctly identifying the origin of highly dissected landforms studies of the contemporary glacial depositional environments and ancient landforms and sediments in the hunza valley karakoram mountains the lahul and garhwal himalaya and the khumbu himalaya illustrate the variability in processes landforms and sediment types these studies can be used to interpret ancient landforms and sediments for paleoenvironmental reconstructions and aid in forming strategies for sampling sediments and rocks for the developing techniques of cosmogenic radionuclide crn surface exposure and optically stimulated luminescence osl dating many himalayan glaciers have thick covers of supraglacial debris derived from valley sides and such debris mantled glaciers exhibit important differences from clean glaciers both in terms of debris transport processes and the depositional landforms that they produce analysis of sediment landform associations can be used to reconstruct processes of sediment transport and deposition and the relationship between moraines and other landforms and climatic forcing cycles such analysis is of fundamental importance in guiding sampling and interpretation in crn and osl dating work

a holocene pollen record from the northwestern himalayan lake tso moriri implications for palaeoclimatic and archaeological research this paper presents a new fossil pollen record from tso moriri 32 54 n 78 19 e 4512 m a s l and seeks to reconstruct changes in mean annual precipitation map during the last 12 000 years this high alpine lake occupies an area of 140 km2 in a glacial tectonic valley in the northwestern himalaya the region has a cold climate with a map 300 mm and open vegetation the hydrology is controlled by the indian summer monsoon ism but winter westerly associated precipitation also affects the regional water balance results indicate that precipitation levels varied significantly during the holocene after a rapid increase in map a phase of maximum humidity was reached between ca 11 and 9 6 cal ka bp followed by a gradual decline in map this trend parallels the reduction in the northern hemisphere summer insolation comparison of different palaeoclimate proxy records reveal evidence for a stronger holocene decrease in precipitation in the northern versus the southern parts of the ism domain the long term trend of ism weakening is overlaid with several short periods of greater dryness which are broadly synchronous with the north atlantic cold spells suggesting reduced amounts of westerly associated winter precipitation compared to the mid and late holocene it appears that westerlies had a greater influence on the western parts of the ism domain during the early holocene during this period the westerly associated summer precipitation belt was positioned at mediterranean latitudes and amplified the ism derived precipitation the tso moriri pollen record and moisture reconstructions also suggest that changes in climatic conditions affected the ancient harappan civilisation which flourished in the greater indus valley from approximately 5 2 to 3 cal ka bp the prolonged holocene trend towards aridity punctuated by an interval of increased dryness between ca 4 5 and 4 3 cal ka bp may have pushed the mature harappan urban settlements between ca 4 5 and 3 9 cal ka bp to develop more efficient agricultural practices to deal with the increasingly acute water shortages the amplified aridity associated with north atlantic cooling between ca 4 and 3 6 and around 3 2 cal ka bp further hindered local agriculture possibly causing the deurbanisation that occurred from ca 3 9 cal ka bp and eventual collapse of the harappan civilisation between ca 3 5 and 3 cal ka bp

evolution of the nourooz anticline nw persian gulf deciphered using growth strata structural inferences to constrain hydrocarbon exploration in persian offshore anticlines abstract the structural features and kinematic evolution of the nourooz anticline an oil producing structure located in the nw persian gulf are unravelled based on the interpretation of a seismic profile grid and well data construction of a 3d depth model and sequential restoration of a 2d geological section the nourooz anticline is a kilometre scale slightly asymmetrical fold that comprises pre growth and growth strata the main stratigraphic feature is an upper cretaceous unconformity the amplification of the nourooz anticline from upper cretaceous to present day probably took place by hinge migration with minor contribution of limb rotation assuming that the structure resulted from horizontal compression and maintained constant bed length the estimated average fold shortening rate is 0 002 mm a assuming that the structure resulted from horizontal shortening and the average fold uplift rate calculated is 0 019 mm a although the fold amplification rates decreased with time the anticline does not seem to be related to a detachment at depth and its growth may have been caused by motion along a basement fault that favoured movement of deep evaporite bodies underneath the anticline and buckling caused by propagation of the zagros belt deformation into the foreland basin the processes involved in the formation of this anticline coincide with those documented for an adjacent structure and seem to be the main processes that controlled the structural style in the persian gulf basin

tectonic evolution of the zagros foreland basin since early cretaceous sw iran regional tectonic implications from subsidence analysis abstract subsidence analysis of 42 exploration wells in the zagros foreland basin indicates the tectonic evolution of the basin since early cretaceous the impact of inherited basement structures on the basin evolution is documented in this study subsidence maps show that the architecture of the basin dramatically changed during the cretaceous in the central zagros the hercynian palaeo high i e wadi al batin palaeo high which affected sedimentation until the early cretaceous time gradually disappeared and the south pars palaeo high within the central persian gulf started to show more impact on sedimentation the palaeo highs in the zagros basement have different geometrical characteristics and origin the hercynian and south pars are wide wavelength palaeo highs with a regional scale impact on subsidence in contrast the hendijan kharg mish and kazerun palaeo highs with different orientations and quite smaller wavelengths show different impact on the subsidence pattern these kinds of palaeo highs could be related to re activation of pre existing basement faults whereas south pars and hercynian paleo highs are possibly related to thermal expansion or contraction of the crust the hendijan and kharg mish palaeo highs with the ne sw orientation were intensively re activated during turonian time on the contrary the kazerun fault with the n s orientation became more active and considerably influenced sedimentation during the last 20 ma selective re activation of deep seated faults might have taken place as a result of changes in the orientation of the far field stress in the region understanding the complexities of inherited structures and their impact on reservoir characteristics can support future exploration activities in the zagros foreland basin

late quaternary climatic changes in the eastern kumaun himalaya india as deduced from multi proxy studies abstract an event of neotectonic activity on an ne sw trending subsidiary fault in the zone of e w running intracrustal boundary thrust south almora thrust in the champawat district of eastern kumaun himalaya resulted in creation of a lake at ca 21 5 bp the lake drained in the late holocene leaving behind a 5 0 m thick sedimentary sequence of mostly black and carbonaceous mud with a minor magnetic reversal between 20 5 and 19 7 ka bp at the base the profile studied by using multi proxies e g carbon isotopes pollen analysis palaeo and mineral magnetism and clay minerals has recorded globally well established abrupt climatic events in the last 20 000 years such as the lgm older dryas od younger dryas yd holocene warming 8 2 ka and 4 2 ka events most events estimated assuming a constant rate of sediment accumulation for similar lithologies may be related to the rapid changes in the local climate and albedo structure the itcz may have played a key role in controlling the behavior of the southwest monsoon from the lgm

active couple indentation in geodynamics of nnw iran evidence from synchronous left and right lateral co linear seismogenic faults in western alborz and iranian azerbaijan domains abstract situated within the central portion of the arabia eurasia collision zone nnw iran exhibits an interesting active tectonic context characterized by synchronous left and right lateral co linear seismogenic faults along the adjacent wnw striking west central alborz e g the rudbar earthquake fault and iranian azerbaijan e g the north tabriz seismogenic fault these structural domains are deforming as a single deformable geomechanical territory between the nearly rigid central iran and south caspian domains to the ssw and nne respectively in this paper we analyze tectonic interactions of these active structural domains and their influence on the geodynamics of nnw iran based on morphotectonic and seismological investigations indentation tectonics is suggested to play an important role in the geodynamics of this territory at a plate tectonic scale the rigid arabian plate acts as the main indenter which bulldozes the less rigid crustal domains ahead into folded belts within zagros and caucasus to the north and pushes other blocks aside in this deformation system the south caspian domain acts as a backstop against southern and western deformation zones the structural domains of alborz to the east and iranian azerbaijan caucasus to the west are separated by the nnw striking astara talesh dextral transpressional zone analysis of morphotectonic features and focal mechanisms conducted in this central portion of nnw iran confirms dextral faulting localized along the nnw striking deformation zone which is in agreement with the observed reverse earthquake faulting on west dipping planes we also discuss the contraction trajectories derived from kinematics and geometry of active folding and faulting features observed within nnw iran our study highlights two prominent sets of fan shaped trajectories dominating in the west and east sides of the n s zone in the astara zanjan direction we propose a couple indentation geodynamic model to explain the fan shaped pattern of these two laterally convergent sets of trajectories within the talesh azerbaijan and alborz domains

climatic fluctuations during the lia and post lia in the kumaun lesser himalaya india evidence from a 400 y old stalagmite record this paper presents the first stable isotope delta o 18 and delta c 13 data of a similar to 400 years 1590 2006 ad long annual to decadal resolution speleothem record collected from the indian lesser himalaya the data show a variation from 2 7 to 5 9 parts per thousand in delta o 18 and 5 3 to 8 8 parts per thousand in delta c 13 the isotopic analyses indicate that the climate during this period can be divided into two stages a wet phase during the little ice age lia 1590 1850 ad and comparatively dry phase during the post lia after 1850 ad however the record also documents the minor dry events during the lia and a wet episode after the lia within the age uncertainty the dry spells during the lia are linked with the historical drought events in the indian subcontinent and similar latitudes the isotopic record is consistent with a number of previous studies in the areas influenced by the westerlies but appears to be conflicting to the regions dominated by the indian summer monsoon ism this may be due to the possible changes in the strength of westerlies in the study area and added by negative anomaly of north atlantic oscillation nao during the lia c 2012 elsevier ltd and inqua all rights reserved

the geology of the persian gulf gulf of oman region a synthesis during the mesozoic most of the arabian peninsula persian gulf south western iran and eastern iraq constituted the arabian platform deformation of the musandam peninsula in the late cretaceous and mid tertiary by compression subduction from the east and southwest collision of the arabian platform and eurasian plate along the zagros crush zone during the oligocene or early miocene and emplacement of the zagros mountains by gravitational sliding during the neogene and pleistocene have reduced the platform area to the persian gulf other factors that contributed to the reduction of the arabian platform include the uplift of the arabian peninsula during the opening of the red sea in the tertiary tectonism of the infracambrian hormuz salt upwarp of the platform sediment cover by basement uplift and or salt tectonics and a 600 to 400 m drop in sea level since the cretaceous at present tectonism in the region is restricted to the northern edge of the gulf of oman where the arabian plate is subducting the eurasian plate from the south and to the zagros crush zone where the arabian and eurasian plates are colliding with one another

timing and nature of late quaternary mountain glaciation compilations of regional to subcontinental scale mountain glacier chronologies from five continents plus hawaii examine the temporal and spatial patterns of mountain glaciation the compilations yield key insights into the nature of past fluctuations in temperature and precipitation in mountains and adjacent regions and provide baseline data for examining the dynamics of glacier responses to climate change key insights from these compilations include the wide variability of glacier responses to fluctuations in insolation temperature and precipitation and the regionally specific variations in climatic variables through late quaternary time the compilations highlight the need to improve the density and quality of geochronological data and to enhance the understanding of the links between climate and glaciation copyright 2008 john wiley sons ltd

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

a train of kink folds in the surficial salt of qom kuh central iran abstract the many subaerial extrusions of salt current in iran are smaller and faster versions of steady state extrusions of metamorphic rocks from crustal channels in mountain chains the extruded salt develops a variety of internal folds as the salt accumulates ductile displacements that can reach metres a year weather induced elastic strains de stress the outer layers of salt extrusions to a brittle carapace of broken dilated salt qom kuh situated in central iran is a comparatively small and slow example of a viscous salt fountain and as a result its brittle elastic carapace may be thicker than most this may account for qom kuh being the only salt fountain known to have a train of 10 m scale kink folds in its surficial salt we attribute these folds to lateral shortening and back shear of a surface parallel planar mechanical anisotropy in the surficial salt induced by gravitationally driven ductile flow of the underlying salt when it is dry the elastic carapace is relatively strong and acts as a stiff corset impeding gravity spreading of the underlying confined salt however the carapace weakens and kinks on wetting allowing the underlying salt to gravity spread these folds illustrate how the weather can affect gravity spreading of surficial salt masses and how complex the interplay of tectonic and climatic signals can be in steady state mountains

stratigraphy and sedimentology of devensian dimlington stadial glacial deposits east yorkshire england the stratigraphy and sedimentology of the glacial deposits exposed along the coast of east yorkshire are reviewed critical sections at filey brigg barmston and skipsea are examined to reassess the stratigraphy of devensian dimlington stadial glacial deposits in the light of recent developments in glacial sedimentology sedimentary and glaciotectonic structures studied in the field and by using scanning electron microscopy are emphasised two hypotheses are considered for the genesis of the interbedded diamictons and stratified sediments the first involves the deposition of lodgement till and or deformation till followed by meltout till which was overridden to produce more deformation till reflecting periods of ice stagnation punctuated by glacier thickening the second hypothesis which is favoured on the basis of field evidence and micromorphology involves the vertical accretion of a deforming till layer associated with cavity channel or tunnel valley fills beneath active ice at barmston the upper part of the diamicton contains elongate pendant structures containing gravels indicating that the diamicton was saturated and able to flow the diamictons therefore represent a complex sequence of tills deposited and deformed by active ice during the dimlington stadial previously published stratigraphical schemes involving classifications of multiple tills in east yorkshire should be simplified and it is more appropriate to assign these to a single formation the skipsea till formation rhythmic glaciolacustrine and proglacial glaciofluvial sediments overlie the tills at barmston and skipsea these were deposited in sag basins during deglaciation as the tills settled and deformed under thickening sediment and as buried ice melted out extensive sands and gravels cap the succession and were deposited on a sandur during the later stages of deglaciation

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

style and timing of glacial and paraglacial sedimentation in a monsoon influenced high himalayan environment the upper bhagirathi valley garhwal himalaya abstract the gangotri glacier at the source of the ganges river has fluctuated greatly throughout the late quaternary in response to climatic oscillations this has resulted in impressive moraines paraglacial debris flow fans and terraces along the upper stretches of the bhagirathi valley cosmogenic radionuclide crn dating of glacial and paraglacial landforms shows that fans terraces and associated moraines formed approximately synchronously as the landscape readjusted to changing environmental conditions this synchronicity suggests that fan and terrace formation is intimately related to glaciation and that fluctuations in glacial and associated environments during times of climatic instability cause rapid sediment transfer and resedimentation of glacial landforms the crn dates show that all existing glacial and paraglacial landforms in the upper bhagirathi valley formed during the late pleistocene and holocene this demonstrates that in this high mountain environment paraglacial and glacial landforms are eroded and resedimented within about 20 000 years furthermore this testifies to the dynamic nature of glacial environments in monsoon influenced high mountain regions

a remote sensing study of active folding and faulting in southern kerman province s e iran geomorphological observations reveal a major oblique fold and thrust belt in kerman province s e iran the active faults appear to link the sabzevaran right lateral strike slip fault in southeast iran to other strike slip faults within the interior of the country and may provide the means of distributing right lateral shear between the zagros and makran mountains over a wider region of central iran the rafsanjan fault is manifest at the earth s surface as right lateral strike slip fault scarps and folding in alluvial sediments height changes across the anticlines and widespread incision of rivers are likely to result from hanging wall uplift above thrust faults at depth scarps in recent alluvium along the northern margins of the folds suggest that the thrusts reach the surface and are active at the present day the observations from rafsanjan are used to identify similar late quaternary faulting elsewhere in kerman province near the towns of mahan and rayen no instrumentally recorded destructive earthquakes have occurred in the study region and only one historical earthquake lalehzar 1923 is recorded in addition gps studies show that present day rates of deformation are low however fault structures in southern kerman province do appear to be active in the late quaternary and may be capable of producing destructive earthquakes in the future this study shows how widely available remote sensing data can be used to provide information on the distribution of active faulting across large areas of deformation

quaternary glacial history of nw garhwal central himalayas a first account of the quaternary glacial history is presented for northwest garhwal central himalaya on the basis of sediments and landforms one glacial stage has been recognised this is called the bhagirathi glacial stage when extensive valley glaciers advanced down the bhagirathi valley to jhala 40 5 km from the snout of gangotri glacier the ela depression during this stage was ca 640 m the bhagirathi glacial stage is constrained by optically stimulated luminescence dates of ca 63 ka and 5 ka bp and this glaciation is considered equivalent to the last glaciation elsewhere in the world the maximum extent of ice occurred ca 63 ka bp this however does not correlate with the last glacial maximum for the northern hemisphere ice sheets 20 18 ka bp a series of sharp crested moraines are present between 1 to 3 km beyond the snouts of most of the present glaciers these moraines formed during the mid holocene 5 ka bp termed here the shivling glacial advance small moraines are inset into these and are dated at about 200 to 300 bp the bhujbas glacial advance ca 300 to 200 bp and considered equivalent to the little ice age in other parts of the world ela depressions of between 40 100 m and 20 60 m occurred during the shivling and bhujbas glacial advances respectively since the bhujbas glacial advance there has been progressive retreat of glaciers initially by downwasting and retreat and then by simple retreat this retreat has accelerated during the last few decades impressive paraglacial fans are associated with deglaciation representing very rapid resedimentation during and soon after ice retreat

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

monsoon variability and major climatic events between 25 and 0 05 ka bp using sedimentary parameters in the gangotri glacier region garhwal himalaya india abstract gangotri glacier has attracted international attention for its rapid rate of retreat it is one of the best studied himalayan glaciers however there are no unanimous views about the history of climate change for the gangotri glacier we prepared the lithologs textural logs by making two trenches in the kame terraces and analysed it in detail for sediment grain parameters and 14c ams dates to infer the depositional sedimentary environments monsoon variability and major climatic events in the gangotri glacier region the sedimentary parameters and geomorphic analysis revealed that the sediments of the kame terraces are consolidated to semi consolidated stratified very coarse to fine grained layers of sand silt and clay with few gravels and sedimentary structures the sediment size indicating energy of the depositional environment varies from medium to fine sand 1 02 2 26 the standard deviation is poorly sorted 0 89 1 46 which describes that the energy of the depositional environment is continuously fluctuating the positive skewness 0 32 0 98 indicates the excess of finer sediments and dominance of low energy whereas very leptokurtic kurtosis 2 28 4 47 describes the fluctuating energy conditions the present study explains the glacial stages and weak indian summer monsoon ism around 19 5 14 5 13 1 10 1 8 6 7 5 2 2 0 54 0 08 ka bp and warm and intense ism during 23 9 22 7 19 4 1 15 0 05 ka bp the higher percentage of clay in both the trenches around 0 65 0 2 ka bp 1300 1750 ad and higher percentage of silt and low clay content around 1 15 0 55 ka bp 800 1400 ad validates the little ice age lia and medieval warm period mwp respectively

progressive unconformities within an evolving foreland fold thrust belt zagros mountains a major angular unconformity between the bakhtyari conglomerates and the underlying agha jari formation has long been interpreted as indicating that orogeny in the zagros simply folded zone took place in plio pleistocene times this study uses field evidence of unconformities between older units in conjunction with geological maps and cross sections to argue that the front of the zagros simply folded zone has propagated in time and space these unconformities indicate that deformation started as early as end eocene in the northeast of the simply folded zone and propagated progressively to the southwest where unconformable contacts are only seen between younger units as shortening continued the southwest migration of the deformation front drove the foreland basin in front of it to its present position along the persian gulf and mesopotamia the climax of orogeny took place at end pliocene time when the most extensive unconformity in the zagros simply folded zone developed between the upper bakhtyari formation and older units active seismicity and documented present uplift imply that the simply folded zone is still propagating southwestward

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

the geology of the kuh e dalneshin area of southern iran and its bearing on the evolution of southern tethys the kuh e dalneshin area lay close to the northern margin of the arabian continent during mesozoic and palaeogene times recent mapping has shown that except perhaps in the late cretaceous it was inactive until it collided with central iran in the miocene the collision represented by a neogene melange zone in the ne resulted in the zagros orogeny and is expressed in the shelf sediments by folding parallel faulting and a possible arcuate sinistral shear in the late cretaceous a localized deepening of the shelf dates from the cenomanian a narrow trough in the w subsided to abyssal depths in the turonian following a period of faulting a more wide spread subsidence affected the shelf in the coniacian and santonian autochthonous cherts and associated sediments accumulated basaltic volcanics were erupted in the ne part of this basin and permian to cenomanian neritic exotic blocks were derived presumably from an uplift at the shelf edge the rocks from the outer edge of this basin slid westwards over their autochthonous counterparts probably in the campanian accompanied by further gliding of masses of earlier mesozoic cherts which had previously been emplaced on the continental margin a sheet of mantle peridotite partly serpentinized and enclosing neritic and metamorphic exotics in turn slid into the basin shelf sedimentation was renewed in the late campanian or maestrichtian but the transgression did not reach the area until the eocene the derivation and emplacement of the allochthonous rocks in the late cretaceous are still imperfectly understood alternative models are discussed one involving gliding from an aborted spreading ridge along the continental margin the other more conventionally based on subduction processes a preference is expressed for the former

multiproxy record of monsoon variability from the ganga plain during 400 1200 a d abstract understanding on the indian summer monsoon ism variability is chiefly based upon the marine proxies and a few continental records the ganga plain one of the most densely populated regions of the world marked by intensive cultivation of monsoon dependent crops and a rich cultural history is not yet well understood in the context of monsoon variability we present here a 400 1200 a d ams radiocarbon dated record of ropan chhapra tal in the central ganga plain using sedimentology environmental magnetism and stable isotope of oxygen for ism variability the environmental magnetic parameters lf arm sirm lf s ratio b 0 cr and hirm inferred antiferromagnetic mineralogy hematite and or goethite independent of grain size variation during 400 900 a d depicting climate variability within warm humid to warm arid conditions favouring stronger ism seasonality prevalence of ferrimagnetic mineralogy under less oxygenated conditions intermittently demonstrates an altered catchment regime or possibly in response to stronger winter monsoon the higher 18 o values around 500 580 and 740 a d indicate warm and arid conditions under weak ism the lower 18 o values around 480 540 and 700 a d and from 900 to 1200 a d occur during warm and humid conditions indicating maximum intensity of the ism increased silt content from 800 a d onwards is due to increased surface runoff in response to enhanced precipitation and the higher clay percentage around 500 580 and 740 indicates low energy ponding conditions under weak ism the well sorted nature of sediment indicates consistency of the lacustrine environments under fairly uniform energy and constant bottom water conditions under varied monsoonal intensity combinations of sediment textures and stable isotope indicate intense ism at 480 and 540 a d with flooding around 700 a d and a weak monsoon at 580 and 740 a d with drought at 500 a d during 900 1200 a d the multiproxy record suggests strong summer monsoon synchronous with medieval warm period mwp whereas after 1200 a d the weak monsoon phase coincides with the onset of the little ice age lia

sedimentation in proglacial sunwapta lake alberta the hydrologic and limnologic conditions of sunwapta lake a small proglacial lake in the canadian rocky mountains were investigated with special reference to the sedimentology of this lake discharge and suspended sediment concentrations of the inflowing streams were measured to give estimates of sediment input distribution of large loads of fine glacial sediment is largely by an inflow and wind controlled circulation which commonly fluctuates diurnally the spatial distribution of sedimentation was determined by use of sediment collecting pans placed on the lake bed turbidity currents are rare with only one event monitored in 2 years this event was caused by a burst of highly sediment charged inflow water the rarity of turbidity currents is attributed to the high sediment concentration in the lake water which results from the small size of the lake in relation to the inflow wind generated water movement at the lake floor ranges from 0 0 0 03 m s while the maximum recorded velocity of the turbid

a study of fold characteristics and deformation style using the evolution of the land surface zagros simply folded belt iran abstract deformation styles within a fold thrust belt can be understood in terms of the spatial organization and geometry of the fold structures in young fold thrust belts such as the zagros this geometry is reflected topographically by concordant landform morphology thus the distribution of deformation structures can be characterized using satellite image analysis digital ele vation models the drainage network and geomorphological indicators the two distinct fold types considered in this study fault bend folds and detachment folds both trending nw se interact with streams flowing ne sw from the high zagros mountains into the persian gulf multiple abandoned stream channels cross fault bend folds related to deep seated thrust faults in contrast detachment folds which propagate laterally relatively rapidly are characterized by diverted major stream channels and dendritic minor channels at the fold tips thus these two fold types can be differentiated on the basis of their ge ometry fault bend folds being long linear and asymmetrical can be distinguished from detachment folds which tend to be shorter and symmetrical and on their associated geomorphological structures the spatial organization of these structures in the zagros simply folded belt indicates that deformation is the result of the interaction of footwall collapse and the associ ated formation of long linear fault bend folds and serial folding characterized by relatively short periclinal folds footwall collapse occurs first followed by serial folding to the ne i e in the hanging wall of the fault bend folds often on higher de tachments within the sediment pile 139

neotectonics at the arabian plate margins abstract opening of the red sea is accompanied by convergence between the arabian plate and eurasia regional topography and structure favour gravity glide as the main driving force of plate translation at the leading edge of the plate the zagros mountains undergo coseismic serial folding which is equivalent to holocene shortening by 20 mm year and which has led to major episodes of coastal uplift of which the last was 1700 years bp at the jordan rift transform which bounds the arabian plate on the west a recurrence interval of 1600 years is reported for events of m l 5 5 the palaeomagnetic record for the last 3 2 ma indicates an average spreading rate for the red sea of 20 mm year there is some evidence that hydrothermal activity in the red sea is pulsatory with a period of 2000 year and that it reflects discontinuous spreading the holocene neotectonic records of the zagros the jordan rift and the red sea are the product of complex plate interactions and of the accumulation and release of strain in the crust along the plate margins but they also reflect elastic strain energy storage and release within the arabian plate whence parallels in the period of major deformation episodes in the three deforming zones and the apparent discrepancy between the seismic moment predicted by plate kinematics and that recorded in the zagros any associated intraplate deformation if detected geodetically would thus help the assessment of seismic hazard

sedimentology and origin of deposits from a small ice dammed lake leirbreen norway this paper describes recent proglacial lacustrine sediments exposed by the drainage of a small probably never more than 0 03 km2 ice dammed lake basin at leirbreen central jotunheimen norway the dominant facies include ripple laminated massive and horizontally stratified sands massive and horizontally laminated silts and irregularly laminated fine sands and silts the major control on lake circulation and the nature and distribution of these facies was an underflow driven by a subglacial meltwater stream which formed the major lake input although much of the sedimentary sequence indicates a pulsatory input the proximal character of this small lake prevented the development of classic varved silts compressional deformation of shoreline sediments was due to winter lake ice push other deformational processes included the grounding of icebergs water escape and syn sedimentary downslope collapse observations from an adjacent small ice marginal lake at leirbreen provide support for several of the inferences drawn from the sediments of the former ice dammed lake

gas prospective areas in the zagros domain of iran and in the gulf iranian waters in the province of fars and in its offshore gas reserves in excess of 600tcf discovered in permo triassic carbonates well sealed by the anhydrite of the dashtak fm were originated from early llandoverian highly organic and radioactive shales the current distribution of this source rock was influenced by the pre permian erosion on a system of n s tilted blocks extensive geochemical modeling has shown that oil generation began in the middle jurassic in some areas while the onset of gas window was reached locally as early as middle cretaceous a suite of cumulative isopachs shows the evolution of the source rocks maturity through time it also provides a reliable image of the geometry of the reservoirs the long range migrations and the location of large size oil and gas accumulations on a few continuous regional highs prior to the zagros orogeny huge amounts of gas and limited amounts of light oil later re accumulated in the zagros folds formed during the late miocene and pliocene the characteristics of the dalan and kangan reservoirs and the areal extent of the dashtak fm which seals the system could be deduced from paleogeographic reconstruction distribution of facies and isopachs the distribution of the reservoirs seals surface oil and gas seepages and hydrocarbon related indications together with the location of the gas fields makes possible to select among the numerous permotriassic prospects those which are the most attractive some prospects may also contain light oil rings below gas the silurian source rocks in the zagros foothills of iran a variety of proterozoic rocks were uplifted by proterozoic salt diapirs hormuz fm but no source rocks were found in the few hormuz samples we analyzed no source rocks were found either in the cambro

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