tomographic imaging of the seismic structure beneath the east anatolian plateau eastern turkey the high level of seismic activity in eastern turkey is thought to be mainly associated with the continuing collision of the arabian and eurasian tectonic plates the determination of a detailed three dimensional 3d structure is crucial for a better understanding of this on going collision or subduction process therefore a body wave tomographic inversion technique was performed on the region the tomographic inversion used high quality arrival times from earthquakes occurring in the region from 1999 to 2001 recorded by a temporary 29 station broadband iris passcal array operated by research groups from the universities of bogazici turkey and cornell usa the data was inverted and consisted of 3 114 p and 2 298 s wave arrival times from 252 local events with magnitudes md ranging from 2 5 to 4 8 the stability and resolution of the results were qualitatively assessed by two synthetic tests a spike test and checkerboard resolution test and it was found that the models were well resolved for most parts of the imaged domain the tomographic inversion results reveal significant lateral heterogeneities in the study area to a depth of 20 km the p and s wave velocity models are consistent with each other and provide evidence for marked heterogeneities in the upper crustal structure beneath eastern turkey one of the most important features in the acquired tomographic images is the high velocity anomalies which are generally parallel to the main tectonic units in the region existing at shallow depths this may relate to the existence of ophiolitic units at shallow depths the other feature is that low velocities are widely dispersed through the 3d structure beneath the region at deeper crustal depths this feature can be an indicator of the mantle upwelling or support the hypothesis that the anatolian plateau is underlain by a partially molten uppermost mantle

evidence of late cretaceous oroclinal bending in north central anatolia palaeomagnetic results from mesozoic and cenozoic rocks along the izmir ankara erzincan suture zone

segmented african lithosphere beneath the anatolian region inferred from teleseismic p wave tomography summary lithospheric deformation throughout anatolia a part of the alpine himalayan orogenic belt is controlled mainly by collision related tectonic escape of the anatolian plate and subduction roll back along the aegean subduction zone we study the deeper lithosphere and mantle structure of anatolia using teleseismic finite frequency p wave traveltime tomography we use data from several temporary and permanent seismic networks deployed in the region approximately 34 000 p wave relative traveltime residuals measured in multiple frequency bands are inverted using approximate finite frequency sensitivity kernels our tomograms reveal segmented fast seismic anomalies beneath anatolia that corresponds to the subducted portion of the african lithosphere along the cyprean and the aegean trenches we identify these anomalies as the subducted aegean and the cyprus slabs that are separated from each other by a gap as wide as 300 km beneath western anatolia this gap is occupied by slow velocity perturbations that we interpret as hot upwelling asthenosphere the eastern termination of the subducting african lithosphere is located near the transition from central anatolia to the eastern anatolian plateau or arabian eurasian collision front that is underlain by large volumes of hot underplating asthenosphere marked by slow velocity perturbations our tomograms also show fast velocity perturbations at shallow depths beneath northwestern anatolia that sharply terminates towards the south at the north anatolian fault zone nafz the associated velocity contrast across the nafz persists down to a depth of 100 150 km hence our study is the first to investigate and interpret the vertical extent of deformation along this nascent transform plate boundary overall the resolved upper mantle structure of anatolia is directly related with the geology and tectonic features observed at the surface of the anatolian plate and suggest that the segmented nature of the subducted african lithosphere plays an important role in the evolution of anatolia and distribution of its tectonic provinces

evolution of the triassic continental margin northwest anatolia abstract the northwest anatolian basement consists of two distinctly different metamorphic assemblages which were juxtaposed prior to the deposition of liassic cover sediments these include the lower and the upper associations the lower association is mainly represented by triassic metavolcanic and associated metasedimentary units together with a slice of ophiolite the upper association rests on the lower association with a low angle thrust fault and is composed of paleozoic or older schists gneisses and phyllites a transgressive succession begins above the basement with permo carboniferous neritic limestones these platform type carbonates were disrupted by rifting during the early triassic at the initial phase of rifting coarse clastics and associated rift type lavas were formed the rift then evolved into an ocean basin which closed at the end of the triassic the continental margin of the triassic basin underwent regional metamorphism initially high t low p it was followed later by a high p low t metamorphic phase during the metamorphism the continental margin units were multiply deformed by north directed compressive stress later on unmetamorphosed triassic successions of the continental margin were thrust northward onto the metamorphosed part of the same continental margin thus the triassic assemblages of northwest anatolia collectively display the dynamics and various structural affects of the deformation recorded in the continental margin and adjacent oceanic unit

flow mechanism of the des moines lobe of the laurentide ice sheet rapid flow of the des moines lobe of the laurentide ice sheet may have been related to its unlithified substrate new reconstructions of the lobe based on moraine elevations sediment subsidence during moraine deposition and flow direction indicators indicate that the lobe may have been 3 times thicker than in previous reconstructions nevertheless implied basal shear stresses are 15 kpa so internal ice deformation was not significant instead the lobe likely moved by a combination of sliding plowing of particles through the bed surface and bed shear consolidation tests on basal till yield preconsolidation stresses of 125 300 kpa so effective normal stresses on the bed were small a model of sliding and plowing indicates that at such stresses most particles gripped by the ice may have plowed easily through the till bed resulting in too small a shear traction on the bed to shear it at depth consistent with this prediction measurements of orientations of clasts in basal till yield a weak fabric implying pervasive bed shear strain less than 2 although some stronger fabrics have been reported by others we infer tentatively that movement was principally at the bed surface by plowing

crustal disequilibrium of the central pontides northern turkey due to oroclinal bending revealed by gravity modelling abstract the turkish pontide orogenic belt belongs to the former eurasian margin which is the result of two major successive processes of the closure of the tethyan oceans subduction followed by collision this almost e w trending large mountain range shows an arc shaped geometric structure in the northern turkey according to previous studies based on geological and paleomagnetic data oroclinal deformation was proposed as a result of the geodynamic evolution due to the africa eurasia convergence in the region the aim of study is to determine how this important evolution is expressed in the lithosphere beneath the region by gravity modelling a bouguer gravity anomaly map was constructed and from this a gravity model is presented that reveals the general crustal structure underneath the northern turkey the results present a significant crustal thickness change that occurs in the n s and as well as in the e w directions from s to n a significant sharp crustal thickness decrease 20 km was found while from e to w the crustal thickness beneath the pontides increases by approximately 7 km while an average thickness of 37 km was calculated in the east it reached a maximum value of 44 km in the west although the reason for the increase in crustal thickness from north to south is logical in terms of the geodynamic evolution the increase from east to west is probably caused by the nature of the continental collision the most plausible explanation is an oblique nw indentation of the kirsehir block into the pontides

tracking basement cross strike discontinuities in the indian crust beneath the himalayan orogen using gravity data relationship to upper crustal faults the himalaya is the result of the on going convergence and collision of india and asia two plates with complex and protracted geological evolutions the internal configuration and processes that govern the rise of the himalaya and tibetan plateau are crucial to understand continental collision zones however knowledge of the prior configuration of the colliding plates is equally important since inherited preorogenic basement structures can undeniably influence the development of the orogenic architecture throughout the orogen s cycle of collision and eventual collapse three northeast trending palaeotopographic ridges of faulted precambrian indian basement underlie the ganga basin south of the himalaya oil and natural gas commission 1968 valdiya 1976 gahalaut kundu 2012 our study godin harris 2014 illustrates a crustal scale fault origin for these ridges and succeeds in determining how far north beneath the himalayan system they extend and how they ultimately govern the location of upper crustal faults in southern tibet spectrally filtered egm2008 bouguer gravity data and edges in its horizontal gradient at different source depths gravity worms over northern peninsular india the himalaya and southern tibet reveal several continuous himalayan cross strike discontinuities interpreted to represent crustal faults fig 1 gravity lineaments in peninsular india coincide with edges of the precambrian basement ridges and megakinks up to 100 km wide develop in foreland cover sequences between the interpreted basement faults the interpreted basement faults project northward beneath the himalayan system and southern tibet our results suggest that several active himalayan cross strike faults such as the ones related to many graben in southern tibet are rooted in the underplated indian lower crust or step en echelon along interpreted basement faults our interpretation thus suggests that south tibet graben are spatially related to deepseated crustal scale faults rooted in the underplated indian crust these major discontinuities partition the himalayan range into distinct zones and could ultimately contribute to lateral variability in tectonic evolution along the orogen s strike

aegean tectonics strain localisation slab tearing and trench retreat abstract we review the geodynamic evolution of the aegean anatolia region and discuss strain localisation there over geological times from late eocene to present crustal deformation in the aegean backarc has localised progressively during slab retreat extension started with the formation of the rhodope metamorphic core complex eocene and migrated to the cyclades and the northern menderes massif oligocene and miocene accommodated by crustal scale detachments and a first series of core complexes mccs extension then localised in western turkey the corinth rift and the external hellenic arc after messinian times while the north anatolian fault penetrated the aegean sea through time the direction and style of extension have not changed significantly except in terms of localisation the contributions of progressive slab retreat and tearing basal drag extrusion tectonics and tectonic inheritance are discussed and we favour a model 1 where slab retreat is the main driving engine 2 successive slab tearing episodes are the main causes of this stepwise strain localisation and 3 the inherited heterogeneity of the crust is a major factor for localising detachments the continental crust has an inherited strong heterogeneity and crustal scale contacts such as major thrust planes act as weak zones or as zones of contrast of resistance and viscosity that can localise later deformation the dynamics of slabs at depth and the asthenospheric flow due to slab retreat also have influence strain localisation in the upper plate successive slab ruptures from the middle miocene to the late miocene have isolated a narrow strip of lithosphere still attached to the african lithosphere below crete the formation of the north anatolian fault is partly a consequence of this evolution the extrusion of anatolia and the aegean extension are partly driven from below asthenospheric flow and from above extrusion of a lid of rigid crust

the arkot dag melange in arac area central turkey evidence of its origin within the geodynamic evolution of the intra pontide suture zone abstract in northern turkey the intra pontide suture zone is represented by an east west trending belt of deformed and or metamorphic units located at the boundary between the istanbul zonguldak terrane to the north and the sakarya terrane to the south these units can be regarded as issued from the intra pontide domain whose geodynamic history is still a matter of debate along the akpinar arac bayramoren geotraverse located in central turkey an ophiolite bearing melange known as the arkot dag melange is well exposed along the intra pontide suture zone the arkot dag melange plays a key role in the interpretation of the geodynamic history of the intra pontide domain and can be described as a late santonian chaotic sedimentary deposit consisting of an up to 1000 m thick succession of slide blocks of different sizes and lithologies enclosed in a sedimentary matrix consisting of shales coarse grained arenites pebbly mudstones and pebbly sandstones the slide blocks from a few meters to hectometers in size are represented by metamorphic rocks mainly micaschists and gneisses by ophiolites peridotites gabbros iat and babb basalts and cherts and by sedimentary rocks cherts neritic and pelagic limestone marly limestone and ophiolite bearing turbidites the youngest age among the slide blocks has been provided by the ophiolite bearing turbidites where a late coniacian nannofossil assemblage has been found the cherts have provided a wide range of ages from the middle triassic to late cretaceous whereas the fossils found in the limestone indicate late jurassic to early cretaceous ages the matrix of the arkot dag melange even if unaffected by metamorphism shows deformations represented by multiple meters thick cataclastic shear zones at the boundaries of the melange slices or inside of them according to its features the source area of the arkot dag melange was most likely a continental and oceanic thrust sheet emplaced in the late cretaceous onto a continental margin the data collected from the different slide blocks suggest that the intra pontide domain was characterised by an oceanic basin opened at the latest in the early jurassic the opening of the intra pontide oceanic basin was followed by the development of a subduction zone with a subsequent opening of suprasubduction oceanic basin in the middle jurassic early cretaceous the convergence in this suprasubduction oceanic basin started at the early late cretaceous boundary by an obduction process whereas its final closure can be regarded as late paleocene in age

slab detachment beneath eastern anatolia a possible cause for the formation of the north anatolian fault in this paper we discuss the possibility that the north anatolian fault naf results from the deep deformation of the slab beneath the bitlis hellenic subduction zone we described the tectonic evolution of the anatolia aegean area in three main steps before during and after the formation of the naf we remark that the tectonic conditions that are assumed to have triggered the formation of the naf i e collision to the east and extension to the west was already achieved before the onset of that strike slip fault system we also highlight that the formation of the naf was accompanied by the uplift of the turkish iranian plateau and by a surge of volcanism in the eastern anatolia collisional area and probably by the acceleration of the aegean trench retreat we show tomographic images from global p wave model of piromallo and morelli c piromallo a morelli p wave tomography of the mantle under the alpine mediterranean area j geophys res 108 2003 doi 10 1029 2002jb001757 showing that the slab beneath the bitlis collisional belt is not continuous and that its possible rupture pursues to the west at least up to cyprus and possibly up to the eastern end of the hellenic trench all these observations suggest that the plate tectonic re organization occurred in the late miocene early pliocene in the region results from slab break off in the bitlis area and from its lateral propagation to the west this idea is tested in analogue laboratory experiments which confirm that the break of the slab under the collisional belt may trigger 1 the acceleration of slab retreat to the west due to the increase in slab pull force 2 the indentation of the continent in the collisional area and 3 produce the conditions that permit the lateral escape of material towards the west and the formation of the naf

dating of the black sea basin new nannoplankton ages from its inverted margin in the central pontides turkey the eocene uplift and inversion of a part of the black sea margin in the central pontides allows to study the stratigraphic sequence of the western black sea basin the revision of this sequence with 164 nannoplankton ages indicates that subsidence and rifting started in the upper barremian and accelerated during the aptian the rifting of the western black sea basin lasted about 40 myr from late barremian to coniacian in the inner inverted black sea margin the syn rift sequence ends up with shallow marine sands the uppermost albian to turonian was a period of erosion or non deposition this regional mid cretaceous stratigraphical gap might result from rift flank uplift as expected in the case of a thick and cold pre rift lithosphere however coeval collision of the kargi block along the north tethyan subduction zone at the southern margin of the pontides might also have contributed to this uplift a rapid thermal post rift subsidence of the margin occurred during the coniacian santonian collision of the kirsehir continental block commenced in early eocene time zone np12 giving rise to compressional deformation and sedimentation in piggyback basins in the central pontides whereas the eastern black sea was still opening

shear wave splitting in a young continent continent collision an example from eastern turkey 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 2003gl017390 shtml http atlas geo cornell edu turkey publications sandvol et al 2003b htm

late cretaceous to paleocene oroclinal bending in the central pontides turkey 1 the turkish pontide fold and thrust belt formed since the paleozoic and is an important element in the africa eurasia convergence and the resulting closure of the neo tethys ocean it has a peculiar arc shaped geometry in its central part along the black sea coast which may have resulted from oroclinal bending we have determined the vertical axis rotation history of this area using paleomagnetism on cretaceous to eocene rocks from 47 sites and critically analyzed previously published data we applied the same reliability criteria to all data our results show that late cretaceous sites have clockwise and counterclockwise rotations perpendicular to the structural trend in the central pontides in the eastern pontides they show only local rotations paleocene to eocene rocks in the central and eastern pontides show no rotation we conclude that the central pontide northward arc shaped geometry results from oroclinal bending in latest cretaceous to earliest paleocene times the timing and scale of geological processes that occurred in the region make it likely that orocline formation resulted from neo tethys closure between the pontides and the metamorphic promontory of the anatolide tauride block earlier studies on the southerly located cankiri basin reveal that clockwise and counterclockwise rotations occurred in eocene oligocene times this implies that the entire region underwent continuous deformation from late cretaceous to eocene caused by convergence of the pontides and the anatolide tauride block with a southward moving deformation front deformation was first localized in the northern part of the central pontides until the paleocene resulting in oroclinal bending and from at least eocene times it shifted toward the cankiri basin region

magnetotelluric images of the crust and mantle in the southwestern taurides turkey inversion of the magnetotelluric data across the southwestern taurides reveals two subzones of crust with varying thicknesses conductive lower crust b75 v m overlain by resistive n350 v m upper crust with four resistive cores n2000 v m separated by three relatively conductive vertical zones the first and second vertical zones coincide with surface faults interpreted in anatolia suchasfethiyeburdurfaultzone thethirdoneisthemostconductiveandliesin continuitywiththestrabofaultzone in the mediterranean sea a hypocentral cross section of earthquakes along the profile shows more dense seismic activity in the second resistive core where the conductive crust is not present beneath it the depth of the crust upper mantle boundary varies between 30 and 50 km and has an undulating character the resistivity of the upper mantle reaches 500 1000 v m d 2004 elsevier b v all rights reserved

palaeomagnetic evolution of the cankiri basin central anatolia turkey implications for oroclinal bending due to indentation p alaeomagnetic data in combination with palaeostress data and anisotropy of magnetic susceptibility orientations are utilized to develop a tectonic evolutionary model for the early tertiary part of the omega shaped ca nkiri basin turkey the results reveal clockwise rotations in the northeast and anticlockwise rotations in the west and southeastern corner of the basin the magnetic inclinations indicate a northward drift of the ca nkiri basin and support an indentation model for the kirsehir block it is proposed that the shape of the cankiri basin was the result of indentation of the kirsehir block into the sakarya continent during northwards migration accompanying closure of neotethys it appears that the indentation started prior to eocene and ended before middle miocene times

detecting the limit of slab break off in central turkey new high resolution pn tomography results summary inversion of pn traveltime residuals from a 39 station broad band array provides a highresolution image of the velocity structure in the uppermost mantle beneath central turkey individually picked pn phase arrivals from events recorded by the north anatolian fault passive seismic experiment and the kandilli observatory were combined with additional events associated with the eastern turkey seismic experiment tomography results show no change in pn velocity across the north anatolian fault although longitudinal variations are evident a region of very low pn velocities 8 1 km s 1 w est of the fault the sharp transition along the cafz which follows the palaeotectonic inner tauride suture may represent the location of the edge of the slab window created when the oceanic slab broke off along the bitlis zagros suture around 11 ma as the arabian plate collided with the eurasian plate

reconciling the geological history of western turkey with plate circuits and mantle tomography abstract we place the geological history since cretaceous times in western turkey in a context of convergence subduction collision and slab break off to this end we compare the west anatolian geological history with amounts of africa europe convergence calculated from the atlantic plate circuit and the seismic tomography images of the west anatolian mantle structure western turkish geology reflects the convergence between the sakarya continent here treated as eurasia in the north and africa in the south with the anatolide tauride block atb between two strands of the neotethyan ocean convergence between the sakarya and the atb started at least 95 90 myr ago marked by ages of metamorphic soles of ophiolites that form the highest structural unit below sakarya these are underlain by high pressure low temperature metamorphic rocks of the tavsanli and afyon zones and the oren unit which in turn are underlain by the menderes massif derived from the atb underthrusting of the atb below sakarya was since 50 ma associated with high temperature metamorphism and widespread granitic magmatism thrusting in the menderes massif continued until 35 ma after which there is no record of accretion in western turkey plate circuits show that since 90 ma 1400 km of africa europe convergence occurred of which 700 km since 50 ma and 450 km since 35 ma seismic tomography shows that the african slab under western turkey is decoupled from the african plate this detached slab is a single coherent body representing the lithosphere consumed since 90 ma there was no subduction re initiation after slab break off atb collision with europe therefore did not immediately lead to slab break off but instead to delamination of subducting lithospheric mantle from accreting atb crust while staying attached to the african plate this led to asthenospheric inflow below the atb crust high temperature metamorphism and felsic magmatism slab break off in western turkey probably occurred 15 myr ago after which overriding plate compression and rotation accommodated ongoing africa europe convergence slab break off was accommodated along a vertical ne trending subduction transform edge propagator step fault zone accelerating southwestward slab retreat of the aegean slab the se aegean slab edge may have existed already since early miocene times or before but started to rapidly roll back along the southeastern aegean step in middle miocene times penetrating the aegean region in the pliocene

oroclinal bending in the alborz mountains northern iran new constraints on the age of south caspian subduction and extrusion tectonics abstract in this study we report an extensive paleomagnetic study 76 sites carried out in the alborz mts northern iran with the aim of reconstructing the rotation history and the origin of curvature of this orogenic chain the analyzed deposits are the sedimentary successions of the upper red formation miocene lower red formation oligocene and eocene clastic units paleomagnetic results indicate that the alborz mts can be considered a secondary arc that originated as a linear mountain belt that progressively acquired its present day curvature through opposite vertical axis rotations along its strike the curvature of the arc was entirely acquired after the middle late miocene which is the age of the youngest investigated sediments upper red formation overall our paleomagnetic data indicate that the alborz mts can be considered an orocline our results define for the first time the rotational history of the entire alborz curved mountain belt and enable us to reconstruct the paleogeographic and tectonic evolution of northern iran in the framework of arabia eurasia continental deformation the kinematics inferred by the pattern of paleomagnetic rotations is at odds with the present day kinematics of northern iran characterized by the westward extrusion of the south caspian block and by a left lateral shear between central iran and the central and western sectors of the alborz mts by integrating paleomagnetic data with stratigraphic thermochronological structural and gps information we propose that the initiation of south caspian subduction and the activation of westward extrusion of south caspian block occurred diachronously and that the initiation of the present day kinematics of northern iran was quite recent lower pleistocene

geodynamics of collision and collapse at the africa arabia eurasia subduction zone an introduction douwe j j van hinsbergen1 michael a edwards2 rob govers3 paleomagnetic laboratory fort hoofddijk faculty of geosciences utrecht university budapestlaan 17 3584 cd utrecht the netherlands structural processes group department of geological sciences university of vienna althanstrasse 14 vienna a 1090 austria tectonophysics group faculty of geosciences utrecht university budapestlaan 4 3584 cd utrecht the netherlands

cross sectional anatomy and geodynamic evolution of the central pontide orogenic belt northern turkey geophysical data allowed the construction of a 250 km long lithospheric scale balanced cross section of the southern black sea margin espurt et al in lithosphere 6 26 34 2014 in this paper we combine structural field data stratigraphic data and fault kinematics analyses with the 70 km long onshore part of the section to reconstruct the geodynamic evolution of the central pontide orogen these data reveal new aspects of the structural evolution of the pontides since the early cretaceous the central pontides is a doubly vergent orogenic wedge that results from the inversion of normal faults extensional subsidence occurred with an ene trend from aptian to paleocene we infer that the black sea back arc basin also opened during this period which was also the period of subduction of the tethys ocean below the pontides as in the western pontides the cretaceous paleocene subsidence was interrupted from latest albian to coniacian time by uplift and erosion that was probably related to a block collision and accretion in the subduction zone the restoration of the section to its pre shortening state paleocene shows that fault related subsidence locally reached 3600 m within the forearc basin structural inversion occurred from early eocene to mid miocene as a result of collision and indentation of the pontides by the kirsehir continental block to the south with 27 5 km 28 shortening along the section studied the inversion was characterized by nne trending shortening that predated the late neogene dextral escape of anatolia along the north anatolian fault and the modern stress field characterized by nw trending compression within the eocene boyabat basin

geometry kinematics and tectonic models of the kazakhstan orocline central asian orogenic belt abstract the central asian orogenic belt caob is one of the largest accretionary orogens on earth and is characterized by the occurrence of tight oroclines kazakhstan and tuva mongolian oroclines the origin of these large scale orogenic curvatures is not quite understood but is fundamentally important for understanding crustal growth and tectonic evolution of the caob here we provide an outline of available geological and paleomagnetic data around the kazakhstan orocline with an aim of clarifying the geometry kinematics and geodynamic origin of the orocline the kazakhstan orocline is evident in a total magmatic image and can be traced by the continuation of high magnetic anomalies associated with the devonian volcanic belt and the late devonian to carboniferous balkhash yili arc paleomagnetic data show 112 126 clockwise rotation of the northern limb relative to the southern limb in the late devonian to early carboniferous as well as 15 28 clockwise rotation of the northern limb and 39 40 anticlockwise rotation of the southern limb relative to the hinge of the orocline during the late carboniferous to permian we argue that the kazakhstan orocline experienced two stage bending with the early stage of bending late devonian to early carboniferous 112 126 driven by slab rollback and the later stage late carboniferous to permian 54 68 possibly associated with the amalgamation of the siberian tarim and baltic cratons this new tectonic model is compatible with the occurrence of rift basins the spatial migration of magmatic arc and the development of large scale strike slip fault systems during oroclinal bending

the kapanbogazi formation a key unit for understanding late cretaceous evolution of the pontides n turkey abstract the pontides forming the south western continental margin of the black sea consist of two tectonic units the istanbul zone in the west and the sakarya zone in the central and eastern parts the sinop basin in the sakarya zone is filled from base to top by hauterivian to albian turbidites cenomanian turonian red pelagic sediments turonian campanian magmatic arc and related deposits and by the uppermost campanian to middle eocene post magmatic units developed on the southern passive margin of the black sea based on nannofossil dinoflagellate foraminifera and radiolaria data we describe the kapanbogazi formation a cenomanian turonian unit in the sinop basin represented by red calcareous siliceous pelagic shales limestones and cherts passing gradually from the albian black shales these sediments possibly represent deepest depositional conditions of the basin during the cenomanian turonian interval and also reflect the transition from an anoxic to an oxic palaeoenvironmental setting the istanbul zone to the west was emerged during the deposition of the kapanbogazi formation in the sakarya zone in the pontides red pelagic sediments were deposited at different times during the cenomanian maastrichtian interval because the kapanbogazi formation was deposited only in the sakarya zone and because it is present in limited outcrops due to structural reorganization and thick overlying volcanoclastic pile most previous authors assumed cenomanian turonian hiatus herein we describe detailed palaeontological data from this unit and discuss their importance to the interpretation of depositional history and tectonics of the black sea region as well as climatic and eustatic implications

the crustal structure of the east anatolian plateau turkey from receiver functions 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 2003gl018192 shtml http atlas geo cornell edu turkey publications zor et al 2003 htm

determination of tectonic and crustal structure of the eastern pontide orogenic belt ne turkey using gravity and magnetic data the eastern pontide orogenic belt is one of the most complex geodynamic settings within the alpine belt subduction polarity which is responsible for the formation of the eastern pontide magmatic arc is still under debate because of limited geological geophysical and geochemical data this orogenic belt is mainly divided into three subzones depending on lithological characteristics and facies changes as in northern southern and axial zones from north to south these zones are separated from each other by near vertical faults that display the block faulting tectonic style of this belt in this study the tectonic and crustal structure of the eastern pontides which as yet have not been prospected by using geophysical data has been investigated with potential field data the horizontal gradient map obtained from gravity data shows a number of steep and gentle lineaments it seems that these lineaments e w ne and nw trending correspond to major structural zones of continental crust additionally the moho depth and curie point depth variation maps of the eastern pontide orogenic belt have been computed with the power spectral method of the radial wavenumber carried out by using the fast fourier transform method as a result of this method we estimated that the depths of the moho and curie point varied between 29 0 1 2 47 2 1 9 km and 14 3 0 7 27 9 1 4 km respectively our findings indicate that the moho depth generally increases from north to south in the region however the curie point depth level within the crust has an undulating surface not a horizontal one

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

measurements of the cooling at the base of pahoehoe flows temperature measurements were made in august and october of 1994 at the base of small active pahoehoe flow lobes on kilauea volcano hawai i surprisingly after about 2 minutes of initial rapid cooling the basal temperatures increased significantly before resuming a slower cooling trend the recorded temperatures are also warmer than those predicted by simple conductive cooling models preliminary calculations suggest that these observations can be explained by the insulating effect of microfractures in the underlying flow and the kinetics of crystallization the initial cooling may be rapid enough to super cool the lava such that the onset of crystallization is delayed when crystallization does begin it is initially rapid releasing sufficient latent heat to re heat the lava as the system equilibrates the flow resumes a slow cooling

high pressure metasediments in central turkey constraints on the neotethyan closure history 1 the distribution of oceanic domains and continental blocks in central anatolia remains a challenge in understanding the alpine geodynamic evolution of the tethys realm the consumption of a neotethys oceanic branch at the mesozoic cenozoic boundary welded the central anatolian crystalline complex in central turkey and the anatolide tauride block in western turkey with the northerly eurasian margin whether those two regions constituted a single or two distinct continental masses is still matter of debate high pressure metamorphism has been locally evidenced in the afyon zone which was however defined as a greenschist facies metamorphic zone of the anatolide tauride block since the afyon zone composes a metamorphic equivalent of a continental margin exposed far south of the izmir ankara suture zone this encouraged us to reevaluate its metamorphic evolution in order to better understand the relation between western and central turkey our investigations reveal that the high pressure minerals fe mg carpholite and glaucophane are present in the entire afyon zone which we reconsider as a blueschist facies zone we additionally present a tectonic reconstruction stripping off the postcollisional tectonics it reveals that today s bending of the high pressure belt is consistent with an eocene collision of the anatolide tauride block around the southern edge of the central anatolian crystalline complex we argue that the central anatolian crystalline complex and the anatolide tauride block were two distinct continental masses separated by a neotethyan oceanic stripe the closure of which engendered subduction related metamorphism in the latter and arc volcanism and high grade metamorphism in the former by late cretaceous to early cenozoic

bouguer anomalies and crustal structure in the eastern mediterranean abstract riad s refai e and ghalib m 1981 bouguer anomalies and crustal structure in the eastern mediterranean in p vyskocil r green and h malzer editors recent crustal movements 1979 tectonophysics 71 253 266 the bouguer anomaly map of the eastern mediterranean was used for studying the structure of the earth s crust as well as for determining its thickness correlation study of different empirical formulae relating average gravity and elevation with the thickness of the crust is carried out two new formulae are deduced h 29 98 0 075 g h 29 96 3 9 h where g and h are the bouguer anomaly and bathymetry values averaged over 10 grid according to these relations a map for the moho surface is constructed the thickness of the crust is found to range from 14 km below cyprus to about 36 km in the northern part of the area southern turkey it is possible that the crust below cyprus is under compensated the behaviour of the moho surface suggests the presence of a subduction zone in the form of an arc to the south of cyprus the rate of subduction decreases eastward probably the subduction process started in the western part of the traced area and is progressively developing towards the east

late neogene oroclinal bending in the central taurides a record of terminal eastward subduction in southern turkey abstract the tauride fold thrusts belt formed during s n convergence between africa and eurasia since cretaceous time the western end of the central taurides strike nw se highly obliquely to the overall convergence direction and connect to the ne sw beydaglari lycian nappe flank of the western taurides forming the so called isparta angle in neogene time the western and central taurides and the inner part of the isparta angle became overlain by neogene sedimentary basins including manavgat koprucay and aksu characterized by marine clastics and carbonates the eastern limb of the isparta angle experienced multidirectional miocene to present extension whereas e w shortening affected the marine sedimentary basins in the heart of the isparta angle to quantitatively reconstruct the neogene kinematic evolution of the taurides towards restoring the subduction system accommodating africa eurasia convergence we paleomagnetically assess if and when vertical axis rotations affected the manavgat koprucay and aksu basins in early miocene to pliocene times we show that the northern koprucay basin rotated 20 30 clockwise the manavgat basin underwent 25 35 counterclockwise rotation and the aksu basin underwent no rotation since the early middle miocene it was previously shown that the beydaglari region underwent a post middle miocene 20 counterclockwise rotation these results show that the prominent oroclinal salient geometry of the western taurides thus acquired at least in part since miocene times that the koprucay basin rotated relative to the aksu basin along the aksu thrust and that the beydaglari platform rotated relative to the aksu basin along the bucak thrust which must have both been active until late neogene time this synchronous e w shortening in the heart of the isparta angle and multidirectional extension in its eastern limb may be explained by relative westward retreat of an eastward dipping subducting antalya slab that has previously been imaged by seismic tomography and a benioff zone the neogene bucak thrust west of the aksu basin may represent the most recent surface expression of the antalya subduction zone

crustal thickness of turkey determined by receiver function abstract two hundred and sixty seven teleseismic events with a moment magnitude greater than 5 5 which occurred between january 2005 and october 2010 were analyzed to determine the moho depth variation beneath turkey by using the receiver function rf technique the rf technique was applied to 120 broadband seismic stations which were already deployed in the area permanently by the kandilli observatory and earthquake research institute koeri and the disaster and emergency management presidency afad the rfs were stacked considering back azimuth slowness and waveform similarities to enhance the signal noise ratio the genetic algorithm ga was used to obtain both 1 d shear wave speed model and the moho depth beneath each seismic station a data set consisting of 112 shear speed models derived from rfs revealed the crustal structure of turkey for imaging several 2 d profiles of depth migrated rfs were constructed to delineate the fine crustal structure the moho discontinuity is clearly seen on all profiles and the mid crustal velocity discontinuity within the crust is observed in some profiles the depth of the moho varies between 24 and 48 km the thinnest crustal thickness is located on the coast of western turkey and the deepest moho boundary is observed in eastern turkey the shear wave velocities vary between 4 0 km s and 4 5 km s in the uppermost mantle beneath turkey

late jurassic amphibolite facies metamorphism in the intra pontide suture zone turkey an eastward extension of the vardar ocean from the balkans into anatolia the palaeogeography of neotethys during its closure is still a matter of debate this study provides new insights into the neotethys closure by the discovery in the intra pontide suture zone turkey of an accretionary complex that recorded a late jurassic c 163 ma amphibolite facies metamorphism results are discussed in the framework of the accretionary events that occurred at the southern margin of laurasia the resulting picture supports a new model in which the vardar suture zone in the balkans and the intra pontide suture zone in anatolia represent remnants of the same elongate oceanic basin supplementary material analytical procedures representative mineral compositions geothermobarometric estimates step heating and in situ 40 ar 39 ar data and backscattered electron photomicrographs showing the distribution of laser spot ages on rock chips are available at www geolsoc org uk sup18759

stratigraphic comparisons along the pontides turkey based on new nannoplankton age determinations in the eastern pontides geodynamic implications we compared the stratigraphic formations along the southern margin of the black sea using 196 nannoplankton ages determined in the western and central pontides and 112 new samples from the eastern pontides we inferred that the istanbul and sakarya zones were amalgamated prior to the early cretaceous extensional subsidence migrated eastwards along the pontides from the barremian to the palaeocene an eastwards younging of the cretaceous magmatism suggested that the eastern black sea basin is younger locally angular unconformities and a stratigraphic gap testify to the late albian uplift of the central pontides as the consequence of the collision of an oceanic edifice cretaceous oceanic red beds are marker beds of santonian age along the much of the pontides and are of mainly campanian age within the eastern pontides the middle campanian paleocene was a non volcanic period characterized by extensional subsidence mainly along the eastern black sea basin the end of cretaceous volcanism can be correlated with a southwards subduction jump syn compressional basins show that contraction started during the ypresian along the entire pontide belt eocene volcanism started earlier in the north lutetian than in the south bartonian of the eastern pontides this propagation of syn collisional volcanism could have resulted from slab steepening under the eastern pontides

palaeomagnetically defined rotations of fault bounded continental blocks in the north anatolian shear zone north central anatolia abstract the 1200 km long north anatolian transform fault connects the east anatolian post collisional compressional regime in the east with the aegean back arc extensional regime to the west this active dextral fault system lies within a shear zone reaching up to 100 km in width and consists of southward splining branches these branches which have less frequent and smaller magnitude earthquake activity compare to the major transform cut and divide the shear zone into fault delimited blocks comparison of palaeomagnetic data from 46 sites in the eocene volcanics from different blocks indicate that each fault bounded block has been affected by vertical block rotations although clockwise rotations are dominant as expected from dextral fault bounded blocks anticlockwise rotations have also been documented these anticlockwise rotations are interpreted as due to anticlockwise rotation of the anatolian block as indicated by gps measurements and the effects of unmapped faults or pre north anatolian fault tectonic events

upper mantle discontinuity structure beneath east anatolian plateau turkey from receiver functions abstract imaging of seismic velocity discontinuities with receiver functions suggests a complex mantle structure beneath the east anatolian plateau by stacking all the receiver functions as a function of ray parameter we examined the moveout characteristics of the data set and tested different velocity models to fit the arrival times of converted phases from the moho and the lithosphere asthenosphere boundary and their multiples the best fitting model shows anomalously thin crust 40 km and lithosphere 65 km and low uppermost mantle velocities causing systematic delays on later discontinuity arrivals these findings are consistent with the high plateau supported by partially molten and buoyant asthenosphere the upper mantle discontinuities are all visible in different frequencies 0 15 and 0 4 hz especially the 410 km discontinuity does not show frequency dependence in amplitude and suggests a sharpness of 10 km or less spatial variations of the 410 and 660 km discontinuities reveal anticorrelated topography and distinct zones of diminished amplitude associated with a detached slab and delaminated fragments of lithospheric mantle in the south the slab becomes deeper and horizontally deflected towards the east suggesting westward migration of slab detachment and resistance to slab penetration at the 660 km discontinuity in the north the mantle transition zone is characterized by two spatially limited lithospheric fragments with complex geometry at the center of the study area the transition zone is thin 230 km suggesting excess temperature of 120 c this warm mantle anomaly most likely is due to hot material trapped within the upper mantle between slab in the south and delaminated fragments in the north

reconstructing the geometry of central anatolia during the late cretaceous large scale cenozoic rotations and deformation between the pontides and taurides the central anatolian crystalline complex cacc exposes metamorphic ophiolitic and igneous rocks that were formed and deformed during closure of the neotethyan ocean the cacc is located in central turkey between the pontides in the north and the taurides in the south separated by major fault zones composite plutons intruded the meta sedimentary and ophiolitic units between 95 and 75 ma and form linear magmatic belts 100 km long along the western and northern margins of the cacc exhumation of the metamorphic and igneous complex was finalized by the paleocene time in this study we paleomagnetically study fifteen plutons spanning the entire non deformed upper cretaceous granitoid belt to test whether the initial configuration of the cacc was modified by vertical axis rotations after its exhumation our results show three internally coherent domains with significantly different vertical axis rotations 1 in the north east the akda block ayb records 151

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

tectonic evolution and paleogeography of the kirsehir block and the central anatolian ophiolites turkey in central and western anatolia two continent derived massifs simultaneously underthrusted an oceanic lithosphere in the cretaceous and ended up with very contrasting metamorphic grades high pressure low temperature in the tavsanli zone and the low pressure high temperature in the kirsehir block to assess why we reconstruct the cretaceous paleogeography and plate configuration of central anatolia using structural metamorphic and geochronological constraints and africa europe plate reconstructions we review and provide new 40ar 39ar and u pb ages from central anatolian metamorphic and magmatic rocks and ophiolites and show new paleomagnetic data on the paleo ridge orientation in a central anatolian ophiolite intraoceanic subduction that formed within the neotethys around 100 90 ma along connected n s and e w striking segments was followed by overriding oceanic plate extension already during suprasubduction zone ocean spreading continental subduction started we show that the complex geology of central and southern turkey can at first order be explained by a foreland propagating thrusting of upper crustal nappes derived from a downgoing dominantly continental lithosphere the kirsehir block and tavsanli zone accreted around 85 ma the afyon zone around 65 ma and taurides accretion continued until after the middle eocene we find no argument for late cretaceous subduction initiation within a conceptual inner tauride ocean between the kirsehir block and the afyon zone as widely inferred we propose that the major contrast in metamorphic grade between the kirsehir block and the tavsanli zone primarily results from a major contrast in subduction obliquity and the associated burial rates higher temperature being reached upon higher subduction obliquity