evolution of a tertiary volcanogenic trough in sw turkey the alakaya basins of the lycien belt field study of several stratigraphic sections from allochthonous thrust fault slices of sw turkey reveal that a deeply subsiding volcanogenic trough the alakaya basin existed during paleocene middle eocene times along the lycian belt the alakaya basin was located along a tectonically active zone of weakness between two relatively stable tectonic terrains the menderes massif to the northwest and the beydaglari continental platform to the southeast the basin was underlain by continental substratum all known outcrops of the alakaya sediments overlie platform carbonates of cretaceous age that correlate with the beydaglari shelf sediments the generation of the volcanogenic alakaya basin reflects a tensional period that culminated in middle eocene when basic volcanic activity took place the tensional stage was replaced by a compressional regime in late eocene and large scale overthrust faulting took place the alakaya basin was closed when the tefenni nappe from the north was emplaced on its sediments in late eocene the alakaya sediments overlying the tefenni nappe and underlying the cretaceous platform carbonates moved southeastward over a hundred kilometers onto the autochthonous sediments of the beydaglari terrain in miocene time the alakaya basin is analogous to the maden basin of se turkey thrust fault belt both basins were located along tectonically active belts the main stage of basin subsidence and volcanism was in middle eocene closure of both basins by large scale thrust faulting was in late eocene the creation and destruction of the volcanogenic alakaya basin may be related to the regional adjustments in plate motions in paleocene eocene times

mud volcano growth by radial expansion examples from onshore azerbaijan abstract we investigated the mode of growth of flat topped mud volcanoes through the study of three active edifices onshore azerbaijan they are the bozdag guzdek the ayazakhtarma and the akhtarma pashaly mud volcanoes the three edifices are up to 80 m high and 3 km wide and have eruptions with recurrent times from a few months to a few years surface changes during and between eruptions were documented by a combination of mapping from satellite pictures repeated direct observation over five years and structural analysis in addition resistivity profiles and microgravity measurements were used to decipher their subsurface geometries we interpret the flat topped character of the mud volcanoes as the result of rapid isostatic readjustment of a brittle surface crust

flexural plate subsidence sedimentation rates and structural development of the super deep south caspian basin abstract on a 270 km long seismic line across the west central and central parts of the south caspian basin an inverse flexural plate method is used to recover original uploaded plate parameters the original plate shows remarkable consistency of parameters determined from the 12 second deep seismic line with average rigidity d 1023 6nm bending moment m 1016n dip angle 0 14 and in line compressive stress of 1012 3n m 1 by sequentially adding the sedimentary units to the average bare basement it is shown that the geometry of the basin at jurassic time had a major downward warp and high sedimentary fill to the west leaving the eastern section open to possible erosion during early and middle cretaceous time the deep western part of the basin was then filled by sediments during late tertiary quaternary time and a new depocenter created across the central and western parts of the basin this newer depocenter was then filled during pliocene quaternary time the combined flexure of the basement plate and corresponding sediment fill behaviors with time are indicative of corresponding lithologic variations across the basin and with suspected organic rich sediments the integrated description of basement sediments and depocenter behavior points to the utility of the inverse procedure for improving our understanding of basinal evolution the value of rigidity is comparable to estimated oceanic crust values in line with the suspected tethys oceanic fragment of an island arc below the sediments the shift in depositional behavior with time from west to more northerly across the line of section is tied to the orogenic rise of the caucasus mountains to the north of the section and to the continued subduction of the talysh vandam plate fragment northward today the transpressional nature of the basin and the resolution of the in line compressive stress into components perpendicular to the great caucasus 70 and also perpendicular to the west caspian deep laid fault 25 30 are both in accord with the 25 30 km of present day sedimentary cover including the variations of thicknesses of seismic stratigraphic units along the section from azerbaijan in the west to nearly the turkmenian border in the east

imaging capability of cross hole seismic reflection surveys1 in seismic migration it is important to sample a range of dips around the local structural dip at each image point meaningful images are obtained only where this condition holds for cross hole seismic reflection surveys the distribution of dips sampled at each image point is controlled principally by the survey geometry including source and receiver array lengths and their element spacings using a real data set as an example the authors show how survey geometry can limit imaging capability close to the boreholes and even in the middle of the section between the boreholes at the processing stage effective removal of direct waves and accurate estimation of the velocity field are essential for optimizing image quality for migration they propose a generalized berryhill gb scheme which is based on the kirchhoff integral and takes into account both the near field and far field terms this should improve the ability to image close to source and receiver arrays provided that the element spacing in the nearby array is small enough

seismic observations from a yakutat eddy in the northern gulf of alaska recent works show that the seismic oceanography technique allows us to relate water column seismic reflections to oceanic finescale structures in this study finescale structures of a surface anticyclonic eddy have been unveiled by reprocessing two seismic transects acquired in the northern gulf of alaska using an 8 km hydrophone streamer and 6600 cu in linear airgun array in september 2008 the eddy was a typical bowl like structure with around 55 km width and 700 m depth it has two fringes around the eddy base and a spiral arm at the ne edge the in situ sea surface temperature and salinity data from a shipboard thermosalinograph help to confirm our interpretations of a spiral arm shed from the warm eddy and the entrained cold water from elsewhere nearby the eddy and offshore the shelf break there is a strong frontal feature probably the alaska current the eddy likely formed offshore yakutat shelf and transported along the offshore shelf break by tracking the sea level anomalies its equivalent diameter of 65 km was measured using the along track altimeter and the seismic constraints it was comparable with results from the representative conventional algorithms of eddy detection geostrophic velocities of the eddy were estimated from the dipping seismic reflections under the assumptions of approximate isopycnals and geostrophic balance measured water properties including sea surface temperature salinity and chlorophyll revealed that eddy translation transports coastal water to the pelagic regions structures synthesized from ctd profiles that sampled an earlier eddy suggest that thin striae around the base might be a common feature in gulf of alaska eddies

new insights into the structure of the south caspian basin from seismic reflection data gorgan plain iran this research presents an integrated study of 2d seismic reflections and calibrated well data to outline the structural development of the gorgan plain on the border of the south caspian hydrocarbon basin in the alborz and kopeh dagh ranges of northeast iran eight seismic horizons including two unconformities have been identified ranging in age from early jurassic to quaternary analysis and interpretation of geophysical data provide an understanding of the structural geology of the gorgan plain crucial for investigation of structural traps seismic interpretation indicates structural features such as deep reverse listric faults inverted normal faults for older formations strike slip and normal faults in younger sequences dome and basin interference patterns of folding for all the top formations well data demonstrate the occurrence of a disconformity at the base of upper cretaceous beds and an angular unconformity at the base of paleogene evidence identified in well and seismic reflection data proves a complex pattern of tectonic phases since the early jurassic it seems reasonable to suppose that these structural patterns are related to a change in direction of tectonic compression which in turn has produced structural hydrocarbon traps in crests of domes in the gorgan area

cenozoic evolution of neotethys and implications for the causes of plate motions africa north america eurasia plate circuit rotations combined with red sea rotations and new estimates of crustal shortening in iran define the cenozoic history of the neotethyan ocean between arabia and eurasia the new constraints indicate that arabia eurasia convergence has been fairly constant at 2 to 3 cm yr since 56 ma with slowing of africa eurasia motion to 1 cm yr near 25 ma coeval with the opening of the red sea ocean closure occurred no later than 10 ma and could have occurred prior to this time only if a large amount of continental lithosphere was subducted suggesting that slowing of africa significantly predated the arabia eurasia collision these kinematics imply that africa s disconnection with the negative buoyancy of the downgoing slab of lithosphere beneath southern eurasia slowed its motion the slow steady rate of northward subduction since 56 ma contrasts with strongly variable rates of magma production in the urumieh dokhtar arc implying magma production rate in continental arcs is not linked to subduction rate

the tertiary geodynamical evolution of the aegean arc a paleomagnetic reconstruction abstract the paleomagnetic results obtained in the last 5 6 years from tertiary formations in the aegean domain indicate that the lower miocene arc was almost rectilinear with an e w trend and that its curvature has been acquired tectonically in two major phases during the middle miocene a first phase of deformation is characterized by rotations occurring at the two terminations of the arc clockwise in the west epirus anticlockwise in the east southeastern anatolia a second phase of rotation occurring in the last 5 ma about a pole situated in the southern adriatic sea has affected only the northwestern part the data also indicate that the antalya basin has not been involved in the geodynamical evolution of the arc so that the bey daglari represent its easternmost unit a more complex rotational pattern is observed in the internal zones the large rotations measured in evia 48 and skyros 26 probably occurred in the last 5 ma and result from rotation of fault bounded blocks in a shear zone connecting the north aegean trough to the external arc in the izmir region in the karaburun peninsula of western anatolia and in the island of lesbos significant counterclockwise clockwise or null rotations of coherent blocks have taken place during the neotectonic extensional regime furthermore the values of the inclination obtained from both sedimentary and volcanic oligo miocene formations are systematically shallower than expected on the basis of a geocentered dipole field this suggests that the entire studied area has undergone a northward drift of over 1000 km since the middle miocene

cenozoic evolution of the eastern black sea a test of depth dependent stretching models abstract subsidence analysis of the eastern black sea basin suggests that the stratigraphy of this deep extensional basin can be explained by a predominantly pure shear stretching history a strain rate inversion method that assumes pure shear extension obtains good fits between observed and predicted stratigraphy a relatively pure shear strain distribution is also obtained when a strain rate inversion algorithm is applied that allows extension to vary with depth without assuming its existence or form the timing of opening of the eastern black sea which occupied a back arc position during the closure of the tethys ocean has also been a subject of intense debate competing theories called for basin opening during the jurassic cretaceous or paleocene eocene our work suggests that extension likely continued into the early cenozoic in agreement with stratigraphic relationships onshore and with estimates for the timing of arc magmatism further basin deepening also appears to have occurred in the last 20 myr this anomalous subsidence event is focused in the northern part of the basin and reaches its peak at 15 10 ma we suggest that this comparatively localized shortening is associated with the northward movement of the arabian plate we also explore the effects of paleowater depth and elastic thickness on the results these parameters are controversial particularly for deep water basins and margins but their estimation is a necessary step in any analysis of the tectonic subsidence record stored in stratigraphy

onset of subduction as the cause of rapid pliocene quaternary subsidence in the south caspian basin backstripping a representative stratigraphic column from the northwest of the south caspian basin shows that 2 4 km of tectonic subsidence has occurred since ca 5 5 ma at 1 5 10 times the rate recorded in typical foreland basins roughly half the basin s sedimentary thickness of 20 km has accumulated in this time while the upper part of the succession has begun to deform by buckle folding the south caspian basement appears to be either thick oceanic crust or thinned high velocity continental crust seismicity and gravity data indicate that the basement is in the initial stages of subduction under the middle caspian region to the north we propose that basement subduction began ca 5 5 ma to create the major pliocene quaternary subsidence subduction may have been triggered by a regional reorganization in the arabia eurasia collision at that time possibly following the construction of the turkish iranian plateau

crosswell seismic waveguide phenomenology of reservoir sands shales at offsets 600 m liaohe oil field ne china summary crosswell seismic data recorded at 620 650 m offsets in an oil bearing sand shale reservoir formation at the liaohe oil field northeast china provide robust evidence for waveguide action by low velocity reservoir layers crosswell section velocity models derived from survey well sonic logs and further constrained by observed waveguide seismic wavegroup amplitudes and phases yield plausible evidence for interwell reservoir sand continuity and discontinuity a pair of back to back liaohe crosswell vector seismic surveys were conducted using a source well between two sensor wells at 650 and 620 m offsets along a 200 m thick reservoir formation dipping 7 down to east between depths of 2 5 and 3 km a downhole orbital vibrator generated seismic correlation wavelets with frequency range 50 350 hz and signal noise ratio up to 5 1 over local downhole ambient noise the sensor wells were instrumented with a mobile 12 to 16 level string of clamped vector motion sensor modules at 5 m intervals using 5 m source depth increments crosswell surveys 1 and 2 cover source sensor well intervals above and through the reservoir of respectively 600 m 600 m 13 000 vector traces in 9 common sensor fans and 300 m 560 m 7000 vector traces in 7 common sensor fans survey 1 common sensor gathers show clear consistent high amplitude 20 ms waveletgroup lags behind the first arrival traveltime envelope such arrivals are diagnostic of seismic low velocity waveguides connecting the source and sensor wells observed survey 1 retarded wavegroup depths tally with source and sensor depths in low velocity layers identified in sonic well logs finite difference acoustic model wavefields computed for waveguide acoustic layers constrained by well log sonic velocity data match the observed waveguide traveltime and amplitude systematics model waveforms duplicate the observed m scale and ms scale sensitivity of waveguide spatio temporal energy localization survey 2 crosswell data in contrast provide no comparable evidence for waveguide action despite a sensor well sonic well log similar to that of survey 1 instead acoustic wavefield modelling of survey 2 data clearly favours an interpreted waveguide model with 10 downdip interrupted by a 75 100 m throw down fault near the sensor well the absence of clear waveguide arrivals is adequately explained by dispersal of waveguide energy at the fault discontinuity auxiliary well sonic velocity and lithologic logs confirm the model implied 75 100 m of down throw faulting near the sensor well

oblique reflection of turbidity currents turbidity currents meeting obstacles for example the margins of a confined basin are subject to reflection the consequent change in flow direction is expressed in the sequence of depositional structures of the resulting bed of sediment putative examples of orthogonal reflection have been described based on 180 opposed current directions we present field evidence for the more general case of oblique reflection of turbidites and we report the results of flume experiments indicating a mechanism involving generation of internal solitary waves at an oblique ramp these propagate normal to the ramp regardless of the angle of incidence flow directions in reflected turbidites may indicate the orientation of reflecting surfaces such as basin margin slopes and thus may be of considerable help in paleogeographic and tectonic reconstructions

quaternary syn collision magmatism from the iran turkey borderlands quaternary basaltic and andesitic lavas from the nw iran eastern turkey border area are related to the active arabia eurasia collision the lavas occur within the turkish iranian plateau which ceased crustal thickening before the establishment of a number of volcanic centres within iran and eastern turkey beginning at 10 ma models for generating syn collision magmatism in eastern anatolia have invoked slab break off beneath the thick crust and thin mantle lithosphere of the cenozoic east anatolia accretionary complex and or partial loss of the lower lithosphere here we report geochemical and sm nd rb sr data from a 200 km long n s traverse that samples volcanic flows in nw iran many of which originate from centres in turkey such as ararat and tendurek samples are transitional alkali tholeiitic basalts and andesites ararat samples have lower nb lower large ion lithophile element lile concentrations with 143nd 144nd 0 51290 other volumetrically smaller centres have higher nb higher lile with 143nd 144nd 0 51265 abundances of lile and nb increase from north to south the presumed degree of partial melting increases in the opposite direction away from the arabia eurasia suture melting is inferred to have taken place in the spinel lherzolite field largely from a continental lithosphere source influenced by mesozoic and early cenozoic neo tethyan subduction but a separate source with long term enrichment is needed to explain the high nb lower 143nd 144nd compositions

crustal scale structure of the south caspian basin revealed by deep seismic reflection profiling abstract two deep seismic reflection profiles from the south caspian basin provide the first normal incidence image of possibly the thickest sedimentary basin in the world significant features imaged with these seismic data are 1 a series of high amplitude folds developed within a thick 10 km neogene sedimentary section bounded discordantly below by 2 a gently n dipping intermittent reflection at 14 20 km 8 0 s 3 a prominent deep reflector at 26 28 km depth 12 8 13 0 s with a gentle northward dip 4 an underlying layered interval with discernibly lower frequency reflections down to 36 40 km 16 0 16 5 s and 5 a noticeable decrease in reflectivity below 36 40 km based on the downward termination of fault cored folds and their discordance with subhorizontal underlying reflections the reflection at 14 20 km is interpreted to be the basal detachment for structures associated with the absheron ridge the bright reflection at 26 28 km depth is interpreted as the basement cover contact and the underlying 10 km portion of the section is interpreted as crystalline basement downward diminution of reflectivity at 36 40 km is thought to represent the moho despite the absence of a clearly reflective horizon these interpretations are consistent with previous velocity models from both seismic refraction and teleseismic studies in the south caspian region that suggested a minimum sedimentary thickness of 20 km and a crustal thickness of 35 40 km both the apparent lack of local structural relief on the basement reflector and seismic velocities vp 6 8 km s obtained from earlier studies suggest this crust is not thinned continental material although thicker than typical oceanic crust 6 8 km the apparent 10 km thickness of the south caspian crystalline crust is interpreted to be of oceanic affinity for this part of the basin active seismicity down to mantle depths 80 km and gentle deepening of the crust from south to north suggest northward subduction of the south caspian oceanic lithosphere beneath the continental lithosphere of the central caspian basin

geodynamics seismicity and seismic hazards of the caucasus abstract being a part of ongoing continental collision between the arabian and eurasian plates the caucasus region is a remarkable site of moderate to strong seismicity where devastating earthquakes caused significant losses of lives and livelihood in this article we survey geology and geodynamics of the caucasus and its surroundings magmatism and heat flow active tectonics and tectonic stresses caused by the collision and shortening gravity and density models and overview recent geodetic studies related to regional movements the tectonic development of the caucasus region in the mesozoic cenozoic times as well as the underlying dynamics controlling its development are complicated processes it is clear that the collision is responsible for a topographic uplift inversion and for the formation of the fold and thrust belts of the greater and lesser caucasus tectonic deformations in the region is influenced by the wedge shaped rigid arabian block indenting into the relatively mobile region and producing near n s compressional stress and seismicity in the caucasus regional seismicity is analysed with an attention to sub crustal seismicity under the northern foothills of the greater caucasus which origin is unclear whether the seismicity associated with a descending oceanic crust or thinned continental crust recent seismic tomography studies are in favour of the detachment of a lithospheric root beneath the lesser and greater caucasus the knowledge of geodynamics seismicity and stress regime in the caucasus region assists in an assessment of seismic hazard and risk we look finally at existing gaps in the current knowledge and identify the problems which may improve our understanding of the regional evolution active tectonics geodynamics shallow and deeper seismicity and surface manifestations of the lithosphere dynamics among the gaps are those related to uncertainties in regional geodynamic and tectonic evolution e g continental collision and associated shortening and exhumation lithosphere structure deformation and strain stress partitioning and to the lack of comprehensive datasets e g regional seismic catalogues seismic gravity and geodetic surveys

deflection versus reflection of sediment gravity flows in the late llandovery rhuddnant grits turbidite system welsh basin the rhuddnant grits turbidite system was deposited in an elongate fault bounded trough an apparently ideal locality for the reflection of sediment gravity flows as solitons however 280 palaeocurrent readings from turbidite sandstones do not show the expected high angle discrepancies between palaeocurrent directions from sole structures and those from cross lamination palaeocurrents orthogonal to the bounding lineament are not generally observed instead there is a gradual progressive anticlockwise deflection of the currents with distance from source this may be explained by banking of the currents against an intrabasinal slope by the coriolis effect or by a combination of the two processes

volcanic belts as markers of the mesozoic cenozoic active margin of eurasia abstract from the triassic to the present linear belts of calc alkaline volcanism developed along the southern margin of eurasia in the triassic the calc alkaline belt can be traced in turan fore caucasus crimea and dobrogea its development is related to the closure of the paleo tethys when fragments of gondwana iran afghanistan etc were approaching eurasia since the early jurassic calc alkaline volcanism has been related to subduction of the oceanic crust of the mesozoic tethys five stages of calc alkaline volcanic activity can be distinguished early jurassic middle jurassic early cretaceous late cretaceous paleogene and late miocene quaternary the configuration of the volcanic belts the intensity of the volcanism and the chemistry of the erupted products change considerably from stage to stage mesozoic belts were most pronounced in the pontian transcaucasian segment of the margin starting from the late cretaceous and especially in the cenozoic the volcanic belts can be continuously traced from the balkans to afghanistan most of the belts were actually island arcs formed on the fragments of the hercynian of baikalian basement and in this respect similar to the island arc of japan only the incipient island arcs of senonian age formed close to the passive margin of gondwana are the exceptions they were built on oceanic crust and are geochemically close to the mariana arc at certain times early jurassic eocene parallel chains of island arcs existed in general the situation resembled the present day convergent boundary in the western pacific as closure of the tethys proceeded island arcs gave way to marginal continental volcanic belts with wide spread development of high potassium particularly shoshonitic series peaks of volcanic activity in the bajocian late cretaceous eocene and late miocene present alternated with quiet periods and corresponded to the times when the convergence rate between africa and eurasia increased the opening of the back arc basins is reflected in outbursts of basaltic rift type volcanism these outbursts occurred in the toarcian aalenian bathonian late jurassic aptian turonian and early middle eocene

new evidence and model on the evolution of the southeast anatolian orogen this paper describes the orogenic evolution of the southeast anatolian orogenic belt based mostly on new geologic data collected from its constituent tectonic units in the course of new mapping programs of the past decade the southeast anatolian orogenic segment of the alpides may be divided into three approximately east west trending zones from south to north they are the arabian platform followed by a zone of imbrication and then a zone of nappes the arabian platform includes a mostly marine sedimentary succession deposited from early cambrian to middle miocene time the zone of imbrication is a narrow belt sandwiched between the arabian platform and the zone of nappes it consists of imbricated thrust slices emplaced onto a late cretaceous to early miocene sequence the zone of nappes is the highest tectonic unit consisting of two stacks of nappes simply designated the lower and upper nappes the lower nappe is represented by the slices of a polyphase metamorpbic ophiolitic assemblage and the maden group the upper nappe rests on the lower nappe and is represented by the bitlis and poturge metamorphic massifs southeastern anatolia underwent two major episodes of alpide deformation the first occurred during the late cretaceous period when ophiolite was emplaced on the arabian platform this event was not the consequence of a continental collision the ophiolite obduction onto the arabian platform was followed by a regionwide extension and a new marine transgression over the platform immediately after the ophiolite obduction the second episode of deformation occurred during middle eocene miocene time in two distinct stages as a result of the progressive elimination and complete closure of the ocean s which led to the collision between the zone of nappes located to the north being a part of eurasia and the arabian plate the maden marginal basin formed north of the subduction zone that eliminated the ocean between eurasia and arabia along the southern margin of the taurus belt and abutted the arabian plate much later during the final collision the second episode of deformation formed the present orogenic segment leading to the amalgamation of different tectonic units these amalgamated nappes collided with the arabian plate and welded onto it at the latest stage of the orogenic evolution during the miocene epoch

late cenozoic deformation in the south caspian region effects of a rigid basement block within a collision zone abstract active deformation in the south caspian region demonstrates the enormous variation in kinematics and structural style generated where a rigid basement block lies within a collision zone rigid basement to the south caspian basin moves with a westward component relative both to stable eurasia and iran and is beginning to subduct at its northern and western margins this motion is oblique to the approximately north south arabia eurasia convergence and causes oblique shortening to the south and northeast of the south caspian basin thrusting in the alborz and kopet dagh is accompanied by range parallel strike slip faults which are respectively left and right lateral there are also arcuate fold and thrust belts in the region for two principal reasons firstly weaker regions deform and wrap around the rigid block this occurs at the curved transition zone between the alborz and talysh ranges where thrust traces are concave towards the foreland secondly a curved fold and thrust belt can link a deformation zone created by movement of the basement block to one created by the regional convergence west to east thrusts in the eastern talysh represent underthrusting of the south caspian basement but pass via an arcuate fan of fold trains into ssw directed thrusts in the eastern greater caucasus which accommodates part of the arabia eurasia convergence each part of the south caspian region contains one or more detachment levels which vary dependent on the pre pliocene geology buckle folds in the south caspian basin are detached from older rocks on thick mid tertiary mudrocks whereas thrust sheets in the eastern greater caucasus detach on mesozoic horizons in the future the south caspian basement may be largely eliminated by subduction leading to a situation similar to archaean greenstone belts of interthrust mafic and sedimentary slices surrounded by the roots of mountain ranges constructed from continental crust

the bouma sequence and the turbidite mind set abstract conventionally the bouma sequence bouma a h 1962 sedimentology of some flysch deposits a graphic approach to facies interpretation elsevier amsterdam 168 pp composed of ta tb tc td and te divisions is interpreted to be the product of a turbidity current however recent core and outcrop studies show that the complete and partial bouma sequences can also be interpreted to be deposits formed by processes other than turbidity currents such as sandy debris flows and bottom current reworking many published examples of turbidites most of them hydrocarbon bearing sands in the north sea the norwegian sea offshore nigeria offshore gabon gulf of mexico and the ouachita mountains are being reinterpreted by the present author as dominantly deposits of sandy debris flows and bottom current reworking with only a minor percentage of true turbidites i e deposits of turbidity currents with fluidal or newtonian rheology in which sediment is suspended by fluid turbulence this reinterpretation is based on detailed description of 21 000 ft 6402 m of conventional cores and 1200 ft 365 m of outcrop sections the predominance of interpreted turbidites in these areas by other workers can be attributed to the following 1 loose applications of turbidity current concepts without regard for fluid rheology flow state and sediment support mechanism that result in a category of turbidity currents that includes debris flows and bottom currents 2 field description of deep water sands using the bouma sequence an interpretive model that invariably leads to a model driven turbidite interpretation 3 the prevailing turbidite mind set that subconsciously forces one to routinely interpret most deep water sands as some kind of turbidites 4 the use of our inability to interpret transport mechanism from the depositional record as an excuse for assuming deep water sands as deposits of turbidity currents 5 the flawed concept of high density turbidity currents that allows room for interpreting debris flow deposits as turbidites 6 the flawed comparison of subaerial river currents fluid gravity flows dominated by bed load transport with subaqueous turbidity currents sediment gravity flows dominated by suspended load transport that results in misinterpreting ungraded or parallel stratified deep sea deposits as turbidites and 7 the attraction to use obsolete submarine fan models with channels and lobes that require a turbidite interpretation although the turbidite paradigm is alive and well for now the turbidites themselves are becoming an endangered facies

plate tectonic evolution of the southern margin of eurasia in the mesozoic and cenozoic abstract thirteen time interval maps were constructed which depict the triassic to neogene plate tectonic configuration paleogeography and general lithofacies of the southern margin of eurasia the aim of this paper is to provide an outline of the geodynamic evolution and position of the major tectonic elements of the area within a global framework the hercynian orogeny was completed by the collision of gondwana and laurussia whereas the tethys ocean formed the embayment between the eurasian and gondwanian branches of pangea during late triassic early jurassic times several microplates were sutured to the eurasian margin closing the paleotethys ocean a jurassic cretaceous north dipping subduction boundary was developed along this new continental margin south of the pontides transcaucasus and iranian plates the subduction zone trench pulling effect caused rifting creating the back arc basin of the greater caucasus proto south caspian sea which achieved its maximum width during the late cretaceous in the western tethys separation of eurasia from gondwana resulted in the formation of the ligurian penninic pieniny magura ocean alpine tethys as an extension of middle atlantic system and a part of the pangean breakup tectonic system during late jurassic early cretaceous times the outer carpathian rift developed the opening of the western black sea occurred by rifting and drifting of the western central pontides away from the moesian and scythian platforms of eurasia during the early cretaceous cenomanian the latest cretaceous paleogene was the time of the closure of the ligurian pieniny ocean adria alcapa terranes continued their northward movement during eocene early miocene times their oblique collision with the north european plate led to the development of the accretionary wedge of the outer carpathians and its foreland basin the formation of the west carpathian thrusts was completed by the miocene the thrust front was still propagating eastwards in the eastern carpathians during the late cretaceous the lesser caucasus sanandaj sirjan and makran plates were sutured to the iranian afghanistan plates in the caucasus caspian sea area a north dipping subduction zone jumped during paleogene to the scythian turan platform the shatski terrane moved northward closing the greater caucasus basin and opening the eastern black sea the south caspian underwent reorganization during oligocene neogene times the southwestern part of the south caspian basin was reopened while the northwestern part was gradually reduced in size the collision of india and the lut plate with eurasia caused the deformation of central asia and created a system of nw se wrench faults the remnants of jurassic cretaceous back arc systems oceanic and attenuated crust as well as tertiary oceanic and attenuated crust were locked between adjacent continental plates and orogenic systems

timing cause and impact of the late eocene stepwise sea retreat from the tarim basin west china abstract a vast shallow epicontinental sea extended across eurasia and was well connected to the western tethys before it retreated westward and became isolated as the paratethys sea however the palaeogeography and the timing of this westward retreat are too poorly constrained to determine potential wider environmental impacts let alone understanding underlying mechanisms of the retreat such as global eustasy and tectonism associated with the indo asia collision here an improved chronostratigraphic and palaeogeographic framework is provided for the onset of the proto paratethys sea retreat at its easternmost extent in the tarim basin in western china is provided five different third order sea level cycles can be recognised from the cretaceous palaeogene sedimentary record in the tarim basin of which the last two stepped successively westwards as the sea retreated after the maximum third incursion new biostratigraphic data from the fourth and fifth incursions at the westernmost margin of the tarim basin are compared to our recent integrated bio magneto stratigraphic results on the fourth incursion near the palaeodepocentre in the south western part of the basin while the fourth incursion extended throughout the basin and retreated at 41 ma base c18r the last and fifth incursion is restricted to the westernmost margin and its marine deposits are assigned a latest bartonian early priabonian age from 38 0 to 36 7 ma near top c17n 2n to base c16n 2n similar to the fourth the fossil assemblages of the fifth incursion are indicative of shallow marine near shore conditions and their widespread distribution across eurasia suggests that the marine connection to the western tethys was maintained the lack of diachronicity of the fourth incursion between the studied sections across the southwest tarim basin suggests that the sea entered and withdrew relatively rapidly as can be expected in the case of eustatic control on a shallow epicontinental basin however the westward palaeogeographic step between the fourth and fifth incursions separated by several millions of years rather suggests the combined long term effect of tectonism possibly associated with early uplift of the pamir kunlun shan thrust belt the fourth and fifth regressions are time equivalent with significant aridification steps recorded in the asian interior thus supporting climate modelling results showing that the stepwise sea retreat from central asia amplified the aridification of the asian interior

eocene paleomagnetism of the caucasus southwest georgia oroclinal bending in the arabian syntaxis abstract the caucasus is very important for our understanding of tectonic evolution of the alpine belt but only a few reliable paleomagnetic results were reported from this region so far we studied a collection of more than 300 samples of middle eocene volcanics and volcano sedimentary rocks from 10 localities in the adjaro trialet tectonic zone atz in the western part of the caucasus stepwise thermal demagnetization isolates a characteristic remanent magnetization chrm in 19 sites out of 31 studied chrm reversed directions prevail and a few vectors of normal polarity are antipodal to the reversed ones after tilt correction the fold test is positive too and we consider the chrm primary analysis of tertiary declinations and strikes of alpine folds in the adjaro trialet zone and the pontides in northern turkey shows a large data scatter late cretaceous data from the same region however reveal good correlation between paleomagnetic and structural data combining late cretaceous and tertiary data indicates oroclinal bending of the alpine structures which are locally complicated with different deformation the overall mean tertiary inclination is slightly shallower than the reference eurasian inclination recalculated from one apparent polar wander path apwp but agrees with other this finding is in accord with geological evidence on moderate post eocene shortening across the caucasus we did not find any indication of long lived paleomagnetic anomalies such as to cenozoic anomalously shallow inclinations further to the east in central asia

synchronous deformation on orogenic plateau margins insights from the arabia eurasia collision abstract the temporal and spatial distribution of deformation during the early phases of plateau formation is poorly known the iranian plateau is developing in response to arabia eurasia convergence and is a potential analog to the early phases of tibetan plateau deformation previous studies document the onset of the iranian plateau growth based on the kinematic history of the zagros to the south and the alborz mountains to the north here we present new detrital apatite fission track aft data from 13 modern rivers of the talesh mountains northwestern iranian plateau these mountains lie immediately south west of the rigid south caspian block a total of 1233 single grain cooling ages were measured and range between 185 and 4 ma deconvolution of grain age data documents three main phases of exhumation including the oligocene 30 23 ma early to middle miocene 18 12 ma and early pliocene 5 ma comparison between cooling ages from the talesh mountains and elsewhere across the iranian plateau indicates widespread plateau formation in the oligocene earlier than previously suggested for the northwestern plateau margin these results highlight deformation on both the northern and southern margins of the plateau over almost the entire history of iranian plateau formation a similar pattern of synchronous deformation on the north northeastern and southern margins of the tibetan plateau has recently been documented and highlights the significance of rigid basement blocks focusing far field deformation for both plateaus

palaeomagnetic constraints on the geodynamic evolution of the gibraltar arc subduction zone roll back was recently put forward as a convincing model to explain the geometry and evolution of the gibraltar arc for other subduction related arc systems of the mediterranean such as the calabrian arc and the hellenic arc palaeomagnetic rotation data from neogene extensional basins provided important constraints on geodynamic evolution models here we present the results of a palaeomagnetic study of 13 continuous sections that are located in e w transects across the neogene sedimentary basins of morocco and spain they provide evidence that no significant rotation about vertical axes has occurred in the gibraltar arc since the late tortonian comparison with other mediterranean arc systems shows strong similarities as regards geodynamic evolution the timing of rotation in the gibraltar arc is markedly older than in the calabrian and hellenic arcs and suggests that it is related to the first neogene extensional phase of the western mediterra

insights from petrography mineralogy and u pb zircon geochronology into the provenance and reservoir potential of cenozoic siliciclastic depositional systems supplying the northern margin of the eastern black sea the eastern black sea is one of the few remaining underexplored hydrocarbon basins in europe reservoir quality is a key risk factor in the basin the analysis of up dip portions of oligocene to pliocene depositional systems exposed around its northern and eastern margins enable the composition and provenance of sandstones within the basin to be predicted two major sources of quartz rich sandstone are present the russian western greater caucasus which became a subaerial sediment source in the oligocene and the east european craton scythian platform these are predicted to form better quality reservoirs at shallow and moderate burial depths than their rock fragment rich counterparts due to lesser amounts of compactional porosity loss oligo miocene sandstones from the russian western greater caucasus were deposited as turbidites in the tuapse trough sandstones from the east european craton scythian platform were largely trapped within the indolo kuban basin north of the greater caucasus they only entered the eastern black sea in large volumes from latest miocene or pliocene time in the region of the kerch taman shelf at the western tip of the greater caucasus however it is possible that a precursor to this system supplied the oligocene to early miocene reservoir sandstones within the subbotina field the dziruli massif in western georgia also generated quartz rich sandstones but these are not thought to have entered the black sea

oroclinal bending distributed thrust and strike slip faulting and the accommodation of arabia eurasia convergence in ne iran since the oligocene regional shortening is accommodated across ne iran in response to the collision of arabia with eurasia we examine how n s shortening is achieved on major thrust systems bounding the eastern branch of the alborz east of 57 e sabzevar and kuh e sorkh mountain ranges which lie south of the kopeh dagh mountains in ne iran although these ranges have experienced relatively few large earthquakes over the last 50 yr they have been subject to a number of devastating historical events at neyshabur esfarayen and sabzevar a significant change in the tectonics of the eastern alborz occurs directly south of the central kopeh dagh near 57 e to the east shortening occurs on major thrust faults which bound the southern margin of the range resulting in significant crustal thickening and forming peaks up to 3000 m high active shortening dies out eastward into afghanistan which is thought to belong to stable eurasia the rate of shortening across thrust faults bounding the south side of the eastern alborz north of neyshabur is determined using optically stimulated luminescence dating of displaced river deposits and is likely to be 0 4 1 7 mm yr 1 shortening across the sabzevar range 150 km west of neyshabur has previously been determined at 0 4 0 6 mm yr 1 although reassessment of the rate here suggests it may be as high as 1 mm yr 1 migration of thrust faulting into foreland basins is common across ne iran especially in the esfarayen region near 57 e where the northward deflection of the east alborz range reaches a maximum of 200 20 km from its presumed linear e w strike at the beginning of the oligocene west of 57 e the tectonics of the alborz are affected by the westward motion of the south caspian region which results in the partitioning of shortening onto separate thrust and left lateral strike slip faults north and south of the range at the longitude of 59 e published gps velocities indicate that 50 per cent of the overall shortening across ne iran is accommodated in the kopeh dagh the remaining 50 per cent regional shortening must therefore be accommodated south of the kopeh dagh in the eastern alborz and kuh e sorkh ranges assuming present day rates of slip and the fault kinematics are representative of the late cenozoic deformation in ne iran the total 200 20 km n s shortening across the eastern alborz and kopeh dagh mountains since the beginning of uplift of the kopeh dagh basin would be accommodated in 30 8 ma although this extrapolation may be inappropriate over such a long timescale the age is nevertheless consistent with geological estimates of post early to middle oligocene 30 ma for the onset of kopeh dagh uplift

the crustal structure of the southern caspian region the south caspian basin appears to behave as a relatively rigid aseismic block within the otherwise deforming alpine himalayan orogenic belt this anomalous character suggests that there is a fundamental compositional difference between the crust of the south caspian basin and that of the surrounding region five new estimates of crustal velocity structure beneath the southern caspian region are determined by the teleseismic receiver function method these models show that the crust in turkmenia along the trend of the apshceron balkhan sill kopet dag mountains is 50 km thick in the southwestern part of the caspian basin the crust is 33 km thick and consists of a 13 km thick sedimentary section lying on a high velocity vp 7 1 km s 1 lower crustal section in the southeastern part of the basin the crust is 30 km thick and consists of a 10 km thick sedimentary section overlying a 20 km thick low velocity vp 5 8 km s 1 crystalline crust the receiver function models are combined with velocity models from previous russian deep seismic sounding studies into a 1800 km long ese wnw trending crustal cross section across the kura depression the south caspian basin and the kopet dag mountains the most significant features of this crustal model are the 20 km variation in thickness of cenozoic sedimentary basin deposits the absence of a granitic vp 5 8 6 5 km s 1 crustal layer in the central part of the south caspian basin and 20 km of crustal thinning beneath the central part of the basin the moho beneath the south caspian basin has a broad arch like structure whose western boundary is a relatively narrow zone across which the crust thins rapidly 20 km thinning over a 100 km zone and whose eastern boundary has a more gradual change in crustal thickness 20 km thinning over a 400 km zone the velocity depth profiles derived from the receiver functions are compared to laboratory velocity estimates made at pressures and temperatures appropriate for the lower crust in turkmenia but the seismic p wave data alone do not permit differentiation between the various possible rock types the crustal model developed for the south caspian basin is consistent with the hypothesis that the crystalline crust of the basin is a section of oceanic crust that is being overthrust by the continental crust around much of its margins however we cannot rule out the possibility that the crystalline crust beneath the basin is a section of lower continental crust whose upper crustal section has been removed by erosion or faulting

east anatolian high plateau as a mantle supported north south shortened domal structure an edited version of this paper was published by the american geophysical union agu copyright 2003 agu see also http www agu org pubs crossref 2003 2003gl017858 shtml http atlas geo cornell edu turkey publications sengor et al 2003 htm

petrology and geochemistry of post collisional middle eocene volcanic units in north central turkey evidence for magma generation by slab breakoff following the closure of the northern neotethys ocean the eocene volcano sedimentary units of northern anatolia are confined into a narrow zone trending parallel to the intra pontide and izmir ankara erzincan sutures along which the northern branch of the neotethys ocean was closed during a period between late maastrichtian and paleocene the middle eocene formations overlie both the imbricated and highly deformed units of the suture zone which are paleocene or older in age as well as the formations of adjacent continental blocks with a regional disconformity therefore they can be regarded to be post collisional these units are composed of subaerial to shallow marine sedimentary beds i e the orencik formation at the base and a subaerial volcanic unit i e the hamamozu formation in the middle and at the top this sudden facies change from marine to subaerial environment in the middle eocene is a common phenomenon across northern turkey implying that a regional uplift event occurred possibly across the suture zone before the initiation of the volcanism during lutetian the middle eocene lavas span the whole compositional range from basalts to rhyolites and display a calc alkaline character except for alkaline to mildly alkaline lavas from the top of the sequence all lavas display a distinct subduction signature our geochemical data indicate that calc alkaline lavas were derived from a subduction modified source whereas alkaline to mildly alkaline lavas of the late stage were possibly sourced by an enriched mantle domain magmas evolved in magma chambers emplaced possibly at two different crustal levels magmas in deeper 13 km and possibly larger chambers fractionated hydrous mafic minerals e g amphibole and biotite two pyroxenes and plagioclase and assimilated a significant amount of crustal material intermediate to acid calc alkaline lavas and pyroclastics were derived from these chambers magmas in the shallower chambers on the other hand 12 km crystallized anhydrous mineral assemblages assimilated little or no crustal material and fed basic to intermediate lavas in the region both deep and shallow chambers were periodically replenished by mafic magmas we argue that a slab breakoff model explains better than any alternative model i why the volcanism during the middle eocene was confined into a rather narrow belt along the suture zone ii why it initiated almost contemporaneous with a regional uplift after the continental collision event iii why it postdated arc volcanism along the pontides in the north by 15 20 my iv why it assimilated significant amount of crustal material and v why alkalinity of lavas increased in time

practical aspects of an elastic migration inversion of crosshole data for reservoir characterization a paris basin example the main obstacle for a detailed study of a reservoir is the lack of geophysical and petrophysical information between producing wells crosshole seismic data can aid reservoir geologists and engineers in 1 estimating the volume of oil in place 2 mapping permeability porosity barriers and ultimately 3 monitoring and designing enhanced oil recovery experiments due to their high frequency content crosshole seismic data offer an ideal information link between conventional seismic data surface reflection vsps etc and full waveform sonic acoustic logs using a weightdrop downhole source located at one depth level acoustic and multicomponent data at two different wells were collected in the paris basin with interwell distances of about 100 m the target zone includes three sand reservoir levels between depths of 575 and 600 m a 2 d elastic migration inversion m i of the scattered s s and s p crosshole field data produced high resolution s wave velocity and density depth images of the subsurface extending information away from wells and identifying reservoirs the residual energy reduction between synthetic seismograms derived from m i images and field data is 18 percent confirming that images contain elastic information structural dips obtained are very reasonable the observed vertical spatial resolution being of the order of 3 m we believe that this is the first time that such techniques have been applied to crosshole data elastic m i images are generally better than elastic vsp cdp and migration images and have the advantage of producing global quality measures of images such a technique uses as input a background velocity e g a tomogram obtained by traveltime tomography and complements the background by recovering subsurface discontinuities and changes in elastic parameters within the signal bandwidth

building the zagros collisional orogen timing strain distribution and the dynamics of arabia eurasia plate convergence he zagros mountains are the result of the arabia eurasia collision initiated at 35 ma as the rifted arabian lithosphere was underthrusted beneath the iranian plate due to its negative buoyancy the onset of crustal thickening started at 25 ma as recorded by the hinterland exhumation and foreland clastic deposition deformation throughout the arabia eurasia collision zone and the uplift of the iranian plateau occurred after 15 12 ma as a result of shortening thickening of the thin iranian crust we emphasize that only 42 of the post 35 ma convergence is partitioned by shortening within central iran tomographic constraints show ongoing slab steepening or breakoff in the nw zagros whereas underthrusting of the arabian plate is observed beneath central zagros the current subduction dynamics can be explained by the original lateral difference in the buoyancy of the distal margin that promoted slab sinking in nw zagros and underthrusting in central zagros critical wedge approach applied to the zagros favors the hypothesis of strong brittle crust detached above a viscous lower crust in contrast the weak sedimentary cover deforms by buckling of a thick multilayered cover thrust faulting associated with folding occurs in the competent layers and is responsible for most of the earthquakes there is evidence that the role of the slab pull force in driving the arabian plate motion was reduced after 12 ma large scale mantle flow induced by mantle upwelling at the afar plume appears to be the main driver of the arabia plate motion we stress that the main kinematic change in the zagros region occurred at 15 12 ma as the zagros uplifted before the arabian slab detached the zagros appears key to investigate coupling between continental rheology plate driving forces and mountain building in which the role of rift inheritance appears to be central

obduction subduction and collision as reflected in the upper cretaceous lower eocene sedimentary record of western turkey late cretaceous early eocene tethyan evolution of western turkey is characterized by ophiolite obduction high pressure low temperature metamorphism subduction arc magmatism and continent continent collision the imprints of these events in the upper cretaceous lower eocene sedimentary record of western anatolia are studied in thirty eight well described stratigraphic sections during the late cretaceous period western turkey consisted of two continents the pontides in the north and the anatolide taurides in the south these continental masses were separated by the izmir ankara neo tethyan ocean during the convergence the pontides formed the upper plate the anatolide taurides the lower plate the arc magmatism in the pontides along the black sea coast is biostratigraphically tightly constrained in time between the late turonian and latest campanian ophiolite obduction over the passive margin of the anatolide tauride block started in the santonian soon after the inception of subduction in the turonian as a result large areas of the anatolide tauride block subsided and became a region of pelagic carbonate sedimentation during the campanian the leading margin of the anatolide tauride block was buried deeply and was deformed and metamorphosed to blueschist facies during campanian times the campanian arc volcanic rocks in the pontides are conformably overlain by shaley limestone of maastrichtian palaeocene age however maastrichtian sedimentary sequences north of the tethyan suture are of fore arc type suggesting that although arc magmatism ceased by the end of the campanian age continent continent collision was delayed until palaeocene time when there was a change from marine to continental sedimentation in the fore arc basins the interval between the end of the arc magmatism and continent continent collision may have been related to a northward jump of the subduction zone at the end of campanian time or to continued obduction during the maastrichtian

age and tectonomagmatic setting of the eocene copler kabatas magmatic complex and porphyry epithermal au deposit east central anatolia turkey the copler epithermal au deposit and related subeconomic porphyry cu au deposit is hosted by the middle eocene copler kabatas magmatic complex in central eastern anatolia the intrusive rocks of the complex were emplaced into late paleozoic mesozoic metamorphosed sedimentary basement rocks near the northeastern margin of the tauride anatolide block igneous biotite from two samples of the magmatic complex yielded 40ar 39ar plateau ages of 43 75 0 26 ma and 44 19 0 23 whereas igneous hornblende from a third sample yielded a plateau age of 44 13 0 38 these ages closely overlap with 40ar 39ar ages of hydrothermal sericite 44 44 0 28 ma and biotite 43 84 0 26 ma and re os ages from two molybdenite samples 44 6 0 2 and 43 9 0 2 ma suggesting a short lived 1 my magmatic and hydrothermal history at copler no suitable minerals were found that could be used to date the epithermal system but it is inferred to be close in age to the precursor porphyry system the copler kabatas intrusive rocks show i type calc alkaline affinities their normalized trace element patterns show enrichments in large ion lithophile and light rare earth elements and relative depletions in middle and heavy rare earth elements resembling magmas generated in convergent margins however given its distance from the coeval eocene maden helete volcanic arc the complex is interpreted to be formed in a back arc setting in response to paleocene slab roll back and upper plate extension the tectonomagmatic environment of porphyry epithermal mineralization at copler is comparable to some other isolated back arc porphyry systems such as bajo de la alumbrera argentina or bingham canyon usa

constraints on arabian plate motion and extensional history of the red sea analysis of the geologic and geophysical data from the western and northern margin of the arabian plate combined with data from the red sea gulf of aden leads to an interpretation of arabian plate motion that supports an episodic extensional history in the red sea and gulf of aden phase 1 extension began in medial to late eocene and was caused by the nw propagation of the reoriented central indian ridge spreading center it stretched and thinned continental crust along numerous wrench and normal faults that reactivated preexisting structures first phase extension stopped when the arabian plate terminally sutured to eurasia in the medial miocene and halted northward movement of arabia relative to africa the combined african arabian plates moved north more slowly constricting and thickening continental crust in the bitlis zagros sutures while the red sea remained technically quiescent and accumulated salt by the early pliocene continued northward movement was accommodated by lateral extrusion of large continental wedges north of the bitlis zagros sutures this allowed arabia to move northward faster than africa and reopen the red sea where phase 2 extension was expressed by seafloor spreading extension within the red sea gulf of aden rift system has been controlled by the interactions and effects of two factors 1 convergent processes between the north margin of the arabian plate and the eurasian plate to the north and 2 northwest propagation of extension associated with the medial eocene reorganization of the central indian spreading center

middle eocene paleomagnetic data from the eastern sakarya zone and the central pontides implications for the tectonic evolution of north central anatolia 1 a paleomagnetic investigation has been carried out on middle eocene volcanic rocks at 23 sites in the eastern sakarya zone and the central pontides of north central anatolia in order to better understand the regional tectonic evolution of the main zones of northeastern anatolia in the middle eocene the results constrain the tectonic evolution of the area when evaluated in conjunction with earlier published paleomagnetic directions from 92 localities small counterclockwise rotations in the range of r r 1 3 1 4 to r r 17 2 16 8 with respect to eurasia are observed in the central pontides on the northern side of the north anatolian fault naf clockwise rotations ranging between r r 8 5 15 1 and r r 29 7 12 0 are observed between the naf and the sungurlu fault sf in the eastern sakarya zone counterclockwise rotations of r r 18 9 12 4 to r r 42 2 6 9 are observed to the south of the sf our findings combined with previous data support the indentation model of kaymakci et al 2000 2003a 2003b which postulates the collision and northeast directed indentation of the kirsehir block into the sakarya zone this model which was developed to explain the evolution of the cankiri basin can also explain the variable magnitudes of paleomagnetically determined rotations thrust directions and the curvature of the north anatolian ophiolite belt

tectonic control on sedimentary facies pattern and sediment accumulation rates in the miocene foreland basin of the southern alborz mountains northern iran 1 the southern alborz mountains of northern iran are an integral part of the arabia eurasia collision zone a magnetostratigraphic and rock magnetic investigation of the eyvanekey stratigraphic section in the southern alborz mountains reveals the spatiotemporal character of sedimentary facies migration in the alborz foreland basin the section constitutes three coarsening upward units units 1 2 and 3 comprising the upper red and hezardarreh formations our data reveal that the upper red formation was deposited between 17 5 and 7 5 ma while the depositional age of the top of the hezardarreh formation can be extrapolated to 6 2 ma slow sediment accumulation rates correlate with sedimentary facies comprising prograding coarsening upward units this is likely the result of intraforeland uplift units 1 and 2 and basin inversion probably associated with a growth syncline located in the proximal foreland unit 3 in contrast fine grained strata at the bottom of each cycle are associated with faster sediment accumulation rates testifying to enhanced flexural basin subsidence in the course of thrust loading progradation of coarse grained facies also occurred during relatively fast sediment accumulation top of unit 2 suggesting that the influx of coarse grained sediment outpaced the storage capacity of the proximal foreland thus despite an overall southward propagation of deformation into the southern alborz foreland the locus of active deformation must have migrated back and forth on a time scale of circa 0 7 to 2 ma

combining wave equation imaging with traveltime tomography to form high resolution images from crosshole data traveltime tomography is an appropriate method for estimating seismic velocity structure from arrival times however tomography fails to resolve discontinuities in the velocities wave equation techniques provide images using the full wave field that complement the results of traveltime tomography we use the velocity estimates from tomography as a reference model for a numerical propagation of the time reversed data these backpropagated wave fields are used to provide images of the discontinuities in the velocity field the combined use of traveltime tomography and wave equation imaging is particularly suitable for forming high resolution geologic images from multiple source multiple receiver data acquired in borehole to borehole seismic surveying in the context of crosshole imaging an effective implementation of wave equation imaging is obtained by transforming the data and the algorithms into the frequency domain this transformation allows the use of efficient frequency domain numerical propagat

accommodation of late cenozoic oblique shortening in the alborz range northern iran abstract the alborz range northern iran deforms by strain partitioning of oblique shortening onto range parallel left lateral strike slip and thrust faults deformation is due to the north south arabia eurasia convergence and westward motion of the adjacent south caspian relative to iran roughly north south shortening occurs on thrusts that dip inwards from the range margins precambrian basement is not exposed because of detachment along upper proterozoic evaporites and the thickness of overlying strata 10 km other detachments occur within phanerozoic sediments active left lateral strike slip faults trend ene in the east of the range wnw in the west the eastern mosha fault has a left lateral offset of 30 35 km shortening across the range is 30 km 25 30 at the longitude of tehran this is hard to reconcile with the crustal thickness of 35 km which is similar to adjacent basins percentage shortening across the alborz is similar to the adjacent kopet dagh but because the latter is twice as wide finite shortening is roughly half the difference may be accommodated by subduction of the adjacent south caspian basin northwards under the middle caspian south caspian sediments began folding in the pliocene the present kinematics of the alborz may have begun at this time including a reversal from range parallel right lateral to left lateral strike slip faulting but the regional stratigraphy indicates uplift as early as the mid tertiary

wavefield separation by 3 d filtering in crosshole seismic reflection processing in processing crosshole seismic reflection data it is necessary to separate the upgoing and downgoing primary reflections from each other from the direct waves and from other wave types in the data we have implemented a 3 d f k k filter for wavefield separation that is applied in a single pass the complete data set is treated as a data volume with each sample defined by the three coordinates of source depth receiver depth and time the filter works well because upgoing primaries downgoing primaries and direct waves lie in different quadrants in f k k space the strongest multiples including mode converted multiples lie in the same quadrants in f k k space as the direct waves so they are readily rejected together tube waves and mode converted primaries are also suppressed as most of the energy in these wave types lies outside the pass volume for p wave primaries some head wave and s wave primary energy will be passed by the filter however these waves tend to have low amplitudes and late ar

quantifying arabia eurasia convergence accommodated in the greater caucasus by paleomagnetic reconstruction since the late eocene convergence and subsequent collision between arabia and eurasia was accommodated both in the overriding eurasian plate forming the greater caucasus orogen and the iranian plateau and by subduction and accretion of the neotethys and arabian margin forming the east anatolian plateau and the zagros to quantify how much arabia eurasia convergence was accommodated in the greater caucasus region we here provide new paleomagnetic results from 97 volcanic sites 500 samples in the talysh mountains of nw iran that show 15 net clockwise rotation relative to eurasia since the eocene we apply a first order kinematic restoration of the northward convex orocline that formed to the south of the greater caucasus integrating our new data with previously published constraints on rotations of the eastern pontides and lesser caucasus this suggests that north of the talysh 120 km of convergence must have been accommodated north of the eastern pontides and lesser caucasus this is significantly more 200 280 km our reconstruction independently confirms previous caucasus convergence estimates moreover we show for the first time a sharp contrast of convergence between the lesser caucasus and the talysh this implies that the ancient paleozoic mesozoic transform plate boundary preserved between the iranian and east anatolian plateaus was likely reactivated as a right lateral transform fault since late eocene time

tectonic magnetic lineation and oroclinal bending of the alborz range implications on the iran southern caspian geodynamics in this study we use the anisotropy of magnetic susceptibility ams and paleomagnetic data for deciphering the origin of magnetic lineation in weakly deformed sedimentary rocks and for evaluating oroclinal processes within the arabia eurasia collision zone in particular we have analyzed the miocene upper red formation urf from the outer curved front of the southern central alborz mountains of north iran to test for the first time with paleomagnetic data the origin primary versus secondary of this orogenic arc ams data document the existence of a magnetic lineation parallel to the orientation of the major tectonic structures which vary along strike from wnw to ene these directions are highly oblique to the paleoflow directions and hence suggest that the magnetic lineation in the urf was produced by compressional deformation during layer parallel shortening in addition our paleomagnetic data document clockwise and anticlockwise rotations along vertical axis for the western and eastern sectors of the central alborz mountains respectively combined our results suggest that the orogen represents an orocline which formed not earlier than circa 7 6 ma most likely through bending processes caused by the relative motion between the rigid crustal blocks of the collision zone moreover our study provides new insights into the iran southern caspian basin kinematic evolution suggesting that the present day sw motion of the south caspian basin with respect to central iran postdates oroclinal bending and hence cannot be as old as late miocene to early pliocene but a rather recent configuration i e 3 to 1 ma

oligocene uplift of the western greater caucasus an effect of initial arabia eurasia collision the greater caucasus is europe s largest mountain belt significant uncertainties remain over the evolution of the range largely due to a lack of primary field data this work demonstrates that depositional systems within the oligocene early miocene maykop series on either side of the western greater caucasus wgc display a similar provenance and divergent palaeocurrents away from the range constraining a minimum age for the subaerial uplift of the range as early early oligocene an eocene oligocene hiatus basal oligocene olistostromes and a marked increase in nannofossil reworking also point to initial deformation in the earliest oligocene the initial uplift of the wgc occurred during the final assembly of the tethysides to its south uplift commenced after the late eocene final suturing of northern neotethys and during the initial collision of arabia with the southern accreted margin of eurasia this suggests that compressional deformation was rapidly transferred across the collision zone from the indenting arabian plate to its northern margin

new evidence and solution to the maden complex controversy of the southeast anatolian orogenic belt turkey the volcanosedimentary units of late mesozoic tertiary age that outcrop in the southeast anatolian orogenic belt are commonly referred to as the maden complex there is a long lasting controversy over its definition age stratigraphic and structural position and the origin and thus the orogenic evolution to solve this problem large strips across the southeast anatolian orogenic belt have been studied extensively and different rock groups which were regarded previously as the maden unit have been differentiated their major characteristics and differences have been identified the maden unit sensu stricto is here redefined as a volcanosedimentary succession of middle eocene age representing a short lived back arc basin which reached the stage of an embryonic ocean presently the maden group occurs mainly within the lower nappe stack of the nappe zone of the southeast anatolian orogen it rests stratigraphically on an amalgamated nappe package consisting of the different metamorphic tectonic units and in turn is overlain tectonically by the upper nappe units

formation of intracontinental basins in the opposite corners of the tabas block as coeval structures controlled by transpressional faulting iran the interaction of strike slip faults in their restraining junctions allowed for the coeval formation of the tabas and abdoughi basins and led to their inversion during the late cenozoic the intracontinental basins filled with neogene and quaternary deposits were controlled by large scale dextral transpression along major faults that bounded the tabas block which is a part of the central iranian block the anastomosing strike slip fault pattern facilitated the development of both basins in opposite corners of the tabas block the subsided areas were formed as a result of interaction between the restraining junctions of strike slip faults and thrusts flexural loading caused by the uplifted series of thrust sheets resulted in the depression of the opposite fault slabs which permitted deposition of neogene sediments deformation according to the bookshelf mechanism can be considered as a consequence of accommodation of the shortening of the area north of the main zagros thrust and externally imposed shearing along the great kavir doruneh fault during the collision of the arabian and eurasian plates related processes of transpression and counterclockwise rotation of the tectonic blocks included in the central iranian block favored the interaction of strike slip faults the change of far field stress and continuous transpression caused inversion of the basins and formation of neogene folds in the northern and southern corners of the tabas block the geomorphic features observed along these strike slip faults and on the thrust surfaces bounding the folds display their recent activity consistent with present day seismicity and geodetic measurements within the central iranian block

petroleum geology of the black sea abstract the black sea comprises two extensional basins formed in a back arc setting above the northward subducting tethys ocean close to the southern margin of eurasia the two basins coalesced late in their post rift phases in the pliocene forming the present single depocentre the western black sea was initiated in the aptian when a part of the moesian platform now the western pontides of turkey began to rift and move away to the south east the eastern black sea probably formed by separation of the mid black sea high from the shatsky ridge during the palaeocene to eocene subsequent to rifting the basins were the sites of mainly deep water deposition only during the late miocene was there a major sea level fall leading to the development of a relatively shallow lake most of the margins of the black sea have been extensively modified by late eocene to recent compression associated with closure of the tethys ocean gas chromatography mass spectrometry and carbon isotope analysis of petroleum and rock extracts suggest that most petroleum occurrences around the black sea can be explained by generation from an oil prone source rock of most probably late eocene age although a wider age range is possible in the basin centres burial history modelling and source kitchen mapping indicate that this unit is currently generating both oil and gas in the post rift basin a palaeozoic source rock may have generated gas condensate in the gulf of odessa in bulgarian waters the main plays are associated with the development of an eocene foreland basin kamchia trough and in extensional structures related to western black sea rifting the latter continue into the romanian shelf where there is also potential in rollover anticlines due to gravity sliding of neogene sediments in the gulf of odessa gas condensate has been discovered in several compressional anticlines and there is potential in older extensional structures small gas and oil discoveries around the sea of azov point to further potential offshore around the central azov high in offshore russia and georgia there are large culminations on the shatsky ridge but these are mainly in deep water and may have poor reservoirs there are small compressional structures off the northern turkish coast related to the pontide deformation these may include eocene turbidite reservoirs the extensional fault blocks of the andrusov ridge mid black sea high are seen as having the best potential for large hydrocarbon volumes but in 2200 m of water

structural variation along the zagros and the nature of the dezful embayment structure varies along strike in the zagros fold and thrust belt of iran which is a principal element in the arabia eurasia continental collision pre collision late cretaceous ophiolite nappes kermanshah neyriz and related nappes of deep marine sediments radiolarite series were emplaced next to two regions pusht e kuh arc fars which later developed a consistent structural style across the range from the high zagros fault to the foreland limit of deformation the intervening area has a zone of highly imbricated arabian plate strata the bakhtyari culmination thrust southwest towards and over a low relief low elevation region the dezful embayment there are no ophiolite nappes northeast of the bakhtyari culmination isopachs reflect these different structural patterns from late cretaceous time but not earlier in late cretaceous time the dezful embayment recorded less deposition than adjacent areas to the northwest and southeast in the palaeogene there was little net difference between the dezful embayment and its margins the dezful embayment has been a depocentre since roughly 35 ma which is the likely time of initial collision between arabia and eurasia we propose that the syn collision structure and stratigraphy of the zagros is therefore strongly influenced by the variation in late cretaceous ophiolite emplacement but the original cause of this variation is not clear

insights from the talysh of azerbaijan into the paleogene evolution of the south caspian region the age and mode of formation of the south caspian basin are disputed an 10 km thick predominantly middle eocene clastic and volcanic succession is exposed in the talysh mountains of azerbaijan at its western margin here high k alkali basalts pass laterally to the east and southeast into volcanogenic sandstone dominated turbidity current and debris flow deposits these southeasterly directed depositional systems accumulated in water depths generally greater than 200 m and fed directly into the western south caspian basin new ar ar ages cluster around 39 ma with an upper 1400 m thick volcanic interval being deposited in 2 2 0 2 m y we interpret that this rapid deposition and magmatism records a major back arc extensional transtensional event in the talysh north of the north dipping neotethyan subduction zone this event is recognized across much of southwest asia and may indicate a period of significant basin formation within the adjacent south caspian basin a transition into upper eocene lower oligocene strata dominated by fine grained turbidity current and hemipelagic sediments with slope instability features is interpreted to mark the end of rifting and volcanism in the talysh and the start of the arabia eurasia collision overlying oligocene coarse clastic rocks are interpreted as the erosional products of localized topography created by the further propagation of compressional deformation into the talysh region