late cretaceous to late eocene hekimhan basin central eastern turkey as a supra ophiolite sedimentary magmatic basin related to the later stages of closure of neotethys abstract the hekimhan basin is here put forward as a type example of a globally important class of basin known as a supra ophiolite basin such basins form after the emplacement of ophiolitic i e oceanic rocks onto a passive continental margin but long prior to continental collision the hekimhan basin developed as part of the northern margin of the tauride microcontinent during the collision and suturing of two neotethyan oceans to the north namely the inner tauride ocean and the izmir ankara erzincan ocean the basin records two main stages of tectonic development during latest cretaceous to late eocene time the first phase of basin development during the late cretaceous maastrichtian began with the erosion of emplaced ophiolitic rocks resulting in non marine clastic sedimentation subsequently the basin rapidly subsided in response to inferred regional crustal extension resulting in the deposition of hemipelagic marls and local sapropelic mudstones the axial parts of the basin experienced alkaline within plate type basaltic volcanism the late maastrichtian culminated in deposition of shallow marine carbonates overlying paleocene sediments are restricted to thin localised marine evaporates associated with a low angle unconformity the second stage of basin development began during the early eocene with deposition of shallow marine carbonates coupled with localised basaltic volcanism again of extensional type the basin emerged during the mid late eocene in a late stage collisional to post collisional setting compressional deformation largely reflects post suture tightening a short lived marine transgression occurred during the mid miocene the basin was later deformed by both left lateral and right lateral strike slip several different tectonic models are considered notably extension related to the northward pull of a still subducting oceanic slab and back arc extension related to northward subduction of neotethys to the south the first alternative is consistent with the development of adjacent supra ophiolite basins e g ulukisla and darende basins and also with supra ophiolite basins elsewhere e g se turkey balkans oman

refrigeration of the western cordilleran lithosphere during laramide shallow angle subduction the laramide orogeny has generally been attributed to a shift from normal angle to shallow angle subduction beneath the western margin of the north american plate in addition to important mechanical effects this shift may have had important thermal effects on the lithosphere in the western cordillera before the laramide geothermal gradients in the western cordillera were probably normal to high because of the presence below of a hot asthenospheric wedge with the shift to shallow subduction the wedge was probably expelled and replaced by a cold subducting slab that extended just below the cordilleran lithosphere this would shift the western cordillera into a cold forearc like thermal setting dominated by the refrigeration effects of the subducting slab thermochronologic data from the sierra nevada great basin mojave desert western arizona and perhaps the colorado plateau record latest cretaceous early tertiary cooling that may be evidence of such refrigeration if regional refrigeration occurred it would have several important implications 1 metamorphism in the western cordillera would have waned with the start of the laramide orogeny 2 the crust in the western cordillera would have strengthened and become much more resistant to deformation e g gravitational collapse and extension of thickened crust in the sevier hinterland would have been impeded and 3 latest cretaceous early tertiary isotopic cooling ages may not be valid indicators of a period of major regional uplift and unroofng

structural styles of mountain building controls of lithospheric rheologic stratification and extensional inheritance 1 the strength of the crust and the mantle lithosphere are strongly influenced by the temperature the thickness and the composition of the crust and mantle lithosphere and by inherited weaknesses it consequently strongly depends on the geodynamic setting and is then expected to be different from one orogen to another which might explain the diversity of deformation styles here we use 2d thermomechanical models at lithospheric scale to study the effect of the strength of the upper and middle crust on the geometry of contractional systems the role of extensional inheritance is included by forward modeling the formation of rift basin or passive margin and using the resulting extensional structure as initial condition for lithospheric scale inversion our results demonstrate that 1 crustal strength strongly controls the width and the elevation of orogenic wedge 2 relative weak crust facilitates efficient propagating of thick skinned crustal scale thrusts 3 contraction of a strong crust leads to the formation of long thrust sheets and an anti formal stack in the core of the orogen or the accretion of upper crust depending on the depth of the decoupling zone in the mid crust 4 erosion processes favor the localization of shortening in a narrow crustal orogen 5 rifting inheritance can explain the presence at shallower depth of lower crustal or mantle material previously upwelled and facilitates the propagation of the deformation in the external part of the chain the range of predicted behaviors is compared to first order with the zagros the alps and the pyrenees three natural examples for which the crustal structure is well constrained by geophysical data

evolution of retreating subduction boundaries formed during continental collision retreating subduction boundaries formed where the rate of subduction exceeds the rate of overall plate convergence appear to be commonly developed features within regions of early or incomplete continent continent collision they are characterized by regional extension within the overriding plate and at their leading edge by thin skinned arcuate thrust belts that are concave towards the overriding plate as is illustrated by examples from the mediterranean region the formation of retreating subduction boundaries is intimately related to the process of continental collision during the early stages of collision retreating subduction boundaries are commonly formed by lateral ejection from zones of crustal shortening along the main collision boundary retreating plate boundaries can also form before the main collision and the associated thrust belts emplaced as precollisional accretionary assemblages because the driving mechanism for retreating subduction boundaries appears to be gravity acting on a dense subducted slab slab pull subduction usually ceases when and only when thick buoyant continental crust enters the subduction zone thus differences in the evolution and duration of retreating subduction systems can be largely attributed to the size and configuration of the deep water regions available to be subducted in some cases retreating subduction boundaries may escape into the open ocean where they form nearly isolated local tectonic systems in these systems the rate of subduction is approximately compensated by the rate of upper plate extension and migration of the system across the oceanic region may be very rapid for example the horseshoe seamounts located about 800 km offshore in the eastern north atlantic may be the active expression of an east dipping westwardly migrating retreating subduction boundary that has evolved from the betic cordillera rif system active in miocene time and may now be progressing across the atlantic at approximately 50 mm yr an analogous situation may be represented by the scotia arc system a westward dipping retreating subduction system located between the south american and antarctic plates which may have escaped into the south atlantic ocean from a zone of crustal shortening in the andes and is now progressing across the atlantic at a rate of about 80 mm yr

generation of the early cenozoic adakitic volcanism by partial melting of mafic lower crust eastern turkey implications for crustal thickening to delamination abstract early cenozoic 48 50 ma adakitic volcanic rocks from the eastern pontides ne turkey consist of calc alkaline and high k calc alkaline andesite and dacite with sio2 contents ranging from 56 01 to 65 44 wt this is the first time that early eocene volcanism and adakites have been reported from the region the rocks are composed of plagioclase amphibole quartz and mg rich biotite they have high and low mg values ranging from 55 to 62 and 13 to 42 respectively high mg rocks have higher ni and co contents than low mg samples the rocks exhibit enrichments in large ion lithophile elements including the light rare earth elements depletions in nb ta and ti and have high la yb and sr y ratios their relative high isr 0 70474 0 70640 and low end 50 ma values 2 3 to 0 8 are inconsistent with an origin as partial melts of a subducted oceanic slab combined major and trace element and sr nd isotope data suggest that the adakitic magmas are related to the unique tectonic setting of this region where a transition from a collision to an extension stage has created thickening and delamination of the pontide mafic lower crust at 50 ma the high mg adakitic magmas resulted from partial melting of the delaminated eclogitic mafic lower crust that sank into the relatively hot subcrustal mantle and its subsequent interaction with the mantle peridotite during upward transport leaving garnet as the residual phase elevates the mgo content and mg of the magmas whereas low mg magmas formed by the melting of newly exposed lower crustal rocks caused by asthenospheric upwelling which supplies heat flux to the lower crust the data also suggest that the mafic lower continental crust beneath the region was thickened between the late cretaceous and the late paleocene and delaminated during late paleocene to early eocene time which coincides with the initial stage of crustal thinning caused by crustal extensional events in the eastern pontides and rules out the possibility of an extensional regime before 50 ma in the region during the late mesozoic to early cenozoic

tertiary evolution of the sivas basin central turkey abstract the sivas basin is one of several basins in turkey formed during closure of the northern branch of neotethys in early tertiary times cretaceous ophiolitic fragments and eocene platform carbonates and volcaniclastics transported northwards into the basin as olistoliths and grain flow aprons were incorporated into autochthonous eocene turbidites and bioclastic limestones the sequence as a whole was thrust northwards in late eocene times a southward sloping terrestial foreland basin related to northward directed thrusting developed during oligocene times a piggy back basin developed on top of this thrust system during the late oligocene the eocene thrusts were reactivated probably resulting in northward propagation of thrusts in the subsurface in early and mid miocene times the basin was floored by a thrust sheet which had been cut by n s trending tear faults or oblique culminations as a result of non uniform thrust advance in pre miocene times these n s faults were subsequently reactivated as extensional faults radial to the thrust front during early to mid miocene alluvial and shallow marine sedimentation later strike slip displacement along the n s faults was associated with the development of the northern boundary fault of the sivas basin in late miocene times which is regarded as a left lateral transpressive fault related to the north anatolian fault zone

dynamics of continental accretion three dimensional dynamic computer models show how accretionary tectonic margins evolve from the initial plate collision state through a period of plate margin instability and then re establish a stable convergent margin the models illustrate how significant curvature of the orogenic system develops as well as the mechanism for tectonic escape of the back arc region subduction zones where one plate dives under another become congested when they try to accommodate buoyant exotic crust louis moresi et al describe new numerical models of continental accretion that follow the entire process from the initial collision state through a period of plate margin instability to the re establishment of a stable convergent margin the models illustrate how significant curvature of the orogenic system develops as well as the mechanism for tectonic escape of the back arc region subduction zones become congested when they try to consume buoyant exotic crust the accretionary mountain belts orogens that form at these convergent plate margins have been the principal sites of lateral continental growth through earth s history modern examples of accretionary margins are the north american cordilleras and southwest pacific subduction zones the geologic record contains abundant accretionary orogens such as the tasmanides1 along the eastern margin of the supercontinent gondwana and the altaides which formed on the southern margin of laurasia2 in modern and ancient examples of long lived accretionary orogens the overriding plate is subjected to episodes of crustal extension and back arc basin development often related to subduction rollback3 and transient episodes of orogenesis and crustal shortening4 5 6 7 coincident with accretion of exotic crust here we present three dimensional dynamic models that show how accretionary margins evolve from the initial collision through a period of plate margin instability to re establishment of a stable convergent margin the models illustrate how significant curvature of the orogenic system develops as well as the mechanism for tectonic escape of the back arc region the complexity of the morphology and the evolution of the system are caused by lateral rollback of a tightly arcuate trench migrating parallel to the plate boundary and orthogonally to the convergence direction we find geological and geophysical evidence for this process in the tasmanides of eastern australia and infer that this is a recurrent and global phenomenon

rapid pliocene exhumation of the central greater caucasus constrained by low temperature thermochronometry 1 constraining the timing of onset and rates of deformation within the greater caucasus mountains is key to understanding their role in accommodating deformation across the arabia eurasia orogen we present new low temperature thermochronometric constraints on the cenozoic thermal evolution of the central greater caucasus that elucidate a three phase cooling history between 50 and 30 ma cooling within the range was negligible in oligocene time cooling rates throughout the range increased to 4 c myr these rates remained constant until the early pliocene time when they increased again reaching 25 c myr along the axial part of the range rates and timing of oligocene exhumation are consistent with previous results from the western greater caucasus and are proposed to result from onset of subduction of the greater caucasus back arc basin rapid exhumation of the greater caucasus beginning in pliocene time contrasts with previously reported thermal histories for other portions of the range pliocene exhumation of the central greater caucasus appears to be tectonically driven and coincides with widespread evidence for a major reorganization of the arabia eurasia plate boundary we hypothesize that this exhumation and regionally observed plate reorganization results from the collision of the lesser caucasus with eurasia completing the subduction of oceanic lithosphere across this segment of the arabia eurasia plate boundary

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 southernmost margin of the tethys realm during the mesozoic and cenozoic initial geometry and timing of the inversion processes 1 along the northern border of africa pangea breakup has been diachronic during the jurassic the alpine tethys propagated northeastward from the atlantic to the alps during the permian the neo tethys propagated westward from oman to northwestern arabia then a secondary and late branch of neo tethys gave birth to the east mediterranean basin finally the two oceans connected at end of jurassic times achieving the development of africa northern plate boundary by the late cretaceous convergence between africa and eurasia led to the progressive closure of the tethys realm the continental collision is not completely achieved and the different segments of the confrontation zone maghreb central and east mediterranean zagros and oman expose different stages of the process however we emphasize the existence of synchronous geodynamic events from one end of the system to the other although they do not have the same meaning two of them are particularly important the campanian santonian c s event corresponds to 1 obduction and exhumation of high pressure low temperature metamorphic rocks around the arabian promontory 2 inversion along the margins of the east mediterranean basins and 3 lithosphere buckling in the atlas system maghreb and adjacent sahara platform the middle late eocene mle event corresponds to 1 the onset of collision at the northern corner of arabia 2 the onset of slab retreat in the mediterranean and 3 inversion along the margin of the east mediterranean as well as in the atlas the c s event coincides with a change in plate kinematics resulting in an abrupt increase of convergence velocity the mle event coincides with a period of strong coupling between the africa and eurasia plates and an abrupt decrease of convergence velocity in the middle of the system the central mediterranean seems to escape to the effects of convergence and is the site of quite permanent extensional movements since the triassic

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

slow senonian and fast palaeocene early eocene uplift of the granitoids in the central eastern pontides turkey apatite fission track results abstract dating and forward modelling of the fission track data of apatite samples from the dereli ebinkarahisar region south of giresun in the eastern turkish pontides provides quantitative data on the regional tectonics resulting from the closure of neo thetys and the collision of eurasia and gondwana the age vs elevation profiles identified senonian 80 7 3 2 to 62 4 2 5 ma slow uplift and denudation interpreted as the result of the diapiric ascent of subduction related plutons above the neo tethyan subduction zone beneath the eurasian continent this was followed by rapid differential uplift during the palaeocene early eocene 57 4 2 4 to 47 8 2 4 ma which juxtaposed granitoid units of different ages compositions and emplacement levels in the crust and is thought to be related to the collision between the pontide eurasian and anatolide gondwana basements the modelling results must be interpreted with caution but appear to indicate a period of mio pliocene ca 5 ma reheating related to volcanism associated with the westward escape of the anatolian plate and uplift from the pliocene ca 3 5 ma up to the present

record of cenozoic sedimentation from the amanos mountains southern turkey implications for the inception and evolution of the arabia eurasia continental collision abstract the sedimentary succession of the southern amanos mountains bordering the eastern margin of the karasu rift in south central turkey provides a record of environmental change from the eocene lutetian to the upper miocene tortonian that charts the final evolution of the northern margin of the arabian plate prior to and during continental collision eocene shallow marine carbonates hacidagi formation are interpreted as the youngest unit of the arabian passive margin succession deposited on a northwards facing carbonate ramp subsequent deformation and uplift took place during the oligocene represented by folding of the eocene and older strata this is interpreted to be the result of initial continental collision between arabia and eurasia unconformably overlying the eocene limestone are lower miocene conglomerates sandstones and palaeosols up to 150 m thick kici formation these were deposited in a range of marginal marine settings consisting of alluvial fan fan delta facies flood plain as well as basinal facies subsequently during the middle miocene local patch reefs developed in restricted areas kepez formation followed by upper miocene sediments gokdere formation composed of relatively deep water hemipelagic marl with clastic interbeds which represent a transgression during this period the upper miocene becomes sandier upwards this records the regression from the relatively deep water facies to coastal sediments water depth gradually became shallower until during pliocene time the area became continental in nature by the quaternary rifting had resulted in the development of the karasu rift with active alluvial fans along the margins and braided rivers depositing coarse conglomerates in the axial zone these conglomerates are interbedded with basaltic lava flows that resulted from the region extension across the area this research shows that initial continental collision occurred in this area after the lutetian 40 4 ma and before the aquitanian 23 03 ma supporting the hypothesis that the southern neotethys ocean closed during the late eocene to oligocene this was a time of climatic change including the onset of southern hemisphere glaciation in which the closure of the southern neotethys may have had played an important role

late palaeozoic early cenozoic tectonic development of southern turkey and the easternmost mediterranean region evidence from the inter relations of continental and oceanic units

interactions between bubbles in magmas and lavas effects of bubble deformation the interactions between two deformable bubbles are studied in order to determine the effects of deformation on bubble dynamics and to determine the limits in which the effects of deformation can be ignored deformation due to hydrodynamic interactions with other bubbles leads to alignment of horizontally offset bubbles and thus an enhanced rate of coalescence bubble alignment may produce spatial inhomogeneities in bubble concentrations in magmas which implies temporal variations in the concentration and size of bubbles in erupting magmas and spatial variations in solidified lavas an approximate quantitative model for the rate of coalescence of deformable bubbles is developed based on a series of experiments the effects of deformation can be ignored if the largest bubbles have radii less than about 5 mm in silicate magmas

passive margin subduction and the dynamics of collisional orogenesis continental passive margins are characterized by a wide variety of geometries and widths whether these variations have an influence on subsequent dynamics of orogenesis is unresolved to investigate a series of upper mantle numerical experiments were performed with systematically varied continental margin widths and geometries results show that the vertical geometry of subducting continental margin crust controls both crustal and mantle lithosphere deformation on both scales end members can be identified namely break off versus delamination of continental mantle lithosphere and double vergence versus single vergence of crustal thrust fronts form as a direct result of passive margin geometry we find that the subduction of upper crust to depths 100 km promotes lithospheric delamination and is facilitated by an extended passive margin modeled orogens show decreasing upper plate deformation with increasing margin width these results suggest that along strike deformational variation within orogens may develop due to precollision passive margin geometry

post collisional adakite like magmatism in the agvanis massif and implications for the evolution of the eocene magmatism in the eastern pontides ne turkey abstract in the anatolia the caucasus and northwest iran the eocene epoch is characterized by widespread basic to acidic magmatism whose temporal and spatial evolutions and origin are poorly understood in this paper we provide geochronological and geochemical data on a suite of early eocene intrusions from northeast turkey and discuss their origin within a regional tectonic framework post to late collisional moderate to small bodies of quartz diorite and leucogranodiorite as well as later dacite porphyries intrude permo triassic low grade metamorphic rocks in the southern part of the eastern pontides very close to the neo tethyan izmir ankara erzincan suture in places the intrusives display well developed subsolidus foliations indicating on going penetrative deformation during and shortly after emplacement different emplacement depths were inferred based on the contact metamorphic mineral assemblages al in hornblende barometry and igneous textures quartz diorite 14 16 km vs dacitic porphyries 7 km biotite and hornblende ar ar and zircon u pb data indicate that the compositionally and texturally different intrusives were emplaced at 51 ma ypresian three lines of evidence indicate that the early eocene represents a tectonically active time with high exhumation rates 0 6 cm a 1 i the quartz diorite and dacitic porphyries were emplaced at different crustal depths ii the emplacement ages of these texturally distinct intrusive rocks are geochronologically undistinguishable and iii intrusive rocks locally show a well developed foliation the intrusive rocks display high abundances of al 2 o 3 sr ba lrees and low abundances of y sc and hrees and are similar to high silica adakites from supra subduction zone settings the geochemical features imply a residual and or fractionating assemblage rich in hornblende garnet pyroxene and poor in plagioclase all rock types display similar sr nd isotopic characteristics with initial e nd and 87 sr 86 sr values ranging from 1 0 to 1 1 and from 0 70421 to 0 70494 respectively these three coeval rock groups quartz diorite leucogranodiorite and dacite porphyries were generated from a similar source by variable degrees of partial melting and fractionation these data together with those from the literature clearly reveal that the adakitic signature is common in paleocene to early eocene igneous rocks in northern turkey on both sides of the izmir ankara erzincan suture but disappears towards the middle eocene regional geological constraints indicate that the continental collision between the pontides and the anatolide tauride block occurred in the paleocene and that the middle eocene represents a period of major extension characterized by a marine transgression we therefore suggest that the early eocene adakitic magmatism in northern turkey resulted from the presence of a thickened continental crust following the continental collision along the neo tethyan izmir ankara erzincan suture whereas the voluminous middle eocene magmatism was related to extensional collapse of a thickened orogen

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

a new intracontinental transcurrent structure the central anatolian fault zone turkey abstract recent neotectonic studies including remote sensing aerial photographs geological field mapping on various scales and measured stratigraphic section substantiate the existence of a large sinistral intracontinental transcurrent structure which we call the central anatolian fault zone cafz this is an approximately 730 km long 2 km to 80 km wide ne trending active sinistral strike slip fault zone that cuts across the anatolian plateau between duzyayla in the northeast and anamur county in the southwest it continues onward beneath the eastern mediterranean sea and determines the boundary of the antalya and adana basins as far as to the west of cyprus the cafz is a very young neotectonic structure it resulted from the reactivation and propagation of an older paleotectonic structure the so called ecemi s corridor in both nne and sw directions across the inner tauride suture in the plio quaternary times based on geometric discontinuities the cafz is divided into 24 segments each of them is characterized by a number of strike slip morphotectonic features reflecting recent motions the easternmost part of the anatolian platelet is being deformed internally by several dextral to sinistral intraplate strike slip faults these are the lake salt fault zone lsfz the salanda fault sf the cafz the goksu yazyurdu fault zone gyfz and the malatya ovacik fault zone mofz they take up lesser motion and are younger than boundary faults of the anatolian platelet the gyfz and mofz splay from the natf cut across the anatolian platelet and then meet to the eatf whereas other faults are confined into the anatolian platelet and seem to be independent structures however present day structural pattern of all these intraplate faults and boundary faults of the anatolian platelet indicates a regional strain pattern of nnw sse directed shortening and ene wsw directed extension and they seem to have developed to accommodate northward motion of the arabian plate since late early pliocene times

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

the relative density to shear velocity scaling in the uppermost mantle we perform inversions of gravity data geopotential model egm96 and seismic tomography model s16rlbm for the scaling factor which relates relative density anomalies to relative s wave velocity anomalies the gravity data and tomographic model are anti correlated below continents down to a depth of z 200 km this anti correlation is not present below oceans except for smoothness which is controlled by a damping factor no a priori information is added to the inversion data are filtered between degrees 11 and 16 of the spherical harmonic expansion this spectral window is well suited for the study of intermediate size 2000 4000 km anomalies in the uppermost mantle calculations are made separately for sub continental and sub oceanic mantle the sub continental and sub oceanic scaling factors are significantly different at depths shallower than 260 km in both cases the magnitude of is around 0 05 the sub continental scaling factor has a positive root down to z 220 km whereas the sub oceanic scaling factor yields positive values down to z 140 km only at depth shallower than 350 km models of do not depend on the damping factor or the viscosity model at depths greater than 350 km the resolution of z decreases significantly and low degrees 2 4 add information from large scale anomalies and from the lower mantle as a result the shape and values of for 2 16 and 11 16 are significantly different at depths greater than 350 km a possible explanation of the discrepancies between the sub continental and sub oceanic scaling factor is that intermediate scale anomalies are more important in the continental uppermost mantle than in the oceanic uppermost mantle 2001 elsevier science b v all rights reserved

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

the caucasus an actual example of the initial stages of continental collision abstract a field study of the neotectonics of the georgian caucasus is combined with geophysical geodetic and geological information in order to obtain a mechanical model of actual deformation the analysis of satellite photos together with topographical and geological maps shows that the great caucasus is bisected by a nne trending sinistral strike slip fault zone the western great caucasus is thrusted to the south over the rioni basin while on the other hand its northern flank is a monocline that descends gently into the russian platform active volcanism is present from elbruz to kazbeg the eastern great caucasus is limited by thrusts to the north and to the south and intermediate structures are disposed in a fan like shape no recent volcanism is observed the eastern limit of the chain is a nnw trending dextral strike slip fault zone seismicity from a local network illustrates the activity of the thrusts and gives evidence for the strike slip faults microtectonic data confirm the recent activity and the sinistral character of the borjomi kazbeg strike slip fault the strike slip faults bordering the eastern caucasus may be seen as the limits of a plastic wedge in front of the arabian plate at an early stage of continental collision

retrodeforming the arabia eurasia collision zone age of collision versus magnitude of continental subduction the arabia eurasia collision has been linked to global cooling the slowing of africa mediterranean extension the rifting of the red sea an increase in exhumation and sedimentation on the eurasian plate and the slowing and deformation of the arabian plate collision age estimates range from the late cretaceous to pliocene with most estimates between 35 and 20 ma we assess the consequences of these collision ages on the magnitude and location of continental consumption by compiling all documented shortening within the region and integrating this with plate kinematic reconstructions shortening estimates across the orogen allow for 350 km of neogene upper crustal contraction necessitating collision by 20 ma a 35 ma collision requires additional subduction of 400 600 km of arabian continental crust using the oman ophiolite as an analogue ophiolitic fragments preserved along the zagros suture zone permit 180 km of subduction of the arabian continental margin plus overlying ophiolites wholesale subduction of this more dense continental margin plus ophiolites would reconstruct 400 500 km of postcollisional arabia eurasia convergence consistent with a ca 27 ma initial collision age this younger arabia eurasia collision suggests a noncollisional mechanism for the slowing of africa and associated extension

zircon u pb age constraints from iran on the magmatic evolution related to neotethyan subduction and zagros orogeny abstract this study reports zircon la icpms u pb ages of 50 igneous rock samples from the urumieh dokhtar magmatic arc udma and sanandaj sirjan structural zone ssz in iran these results together with literatures and our unpublished age data better delineate the magmatic evolution related to the neotethyan subduction and subsequent zagros orogeny that resulted from the arabia eurasia collision subduction related magmatism was active during jurassic time as evidenced by the presence of widespread i type granitoids from the middle to late jurassic 176 144 ma in the ssz after a protracted magmatic quiescence in the early cretaceous igneous activity renewed inland in the udma from which we identify late cretaceous granitoids 81 72 ma in jiroft and bazman areas the southeastern segment of the udma the udma volcanism was most active and widespread during the eocene and oligocene 55 25 ma much longer lasting than previously thought as just an eocene pulse such a prolonged igneous flare up event in the udma can be correlated to armenia where coeval calc alkaline rocks are common the udma magmatism ceased progressively from northwest to southeast with magmatic activities ending the early miocene ca 22 ma in meghri the middle miocene ca 16 ma in kashan and the late miocene ca 10 6 ma in anar respectively the southeastward magmatic cessation is consistent with the notion of oblique and diachronous collision between arabia and eurasia post collisional volcanism started ca 11 ma in saray east off the urumieh lake which along with later eruptions in sahand 6 5 4 2 ma and sabalan 0 4 ma volcanoes forms a compositionally unique component of the vast volcanic field covering much of the lesser caucasus nw iran and eastern anatolia regions

paleocene carbonate turbidites of the şarkisla region turkey their significance in an orogenic basin abstract a paleocene carbonate sequence occurs in the southwestern part of the sivas refahiye basin arkisla province sivas turkey and is located in the northeast of central anatolia conclusions concerning the late mesozoic to early cenozoic sedimentary evolution have been derived mainly from the carbonate turbidites the vertical and lateral relationships of these rocks suggest deposition in a submarine fan complex three major megacycles characterized by a thickening and coarsening upward trend are seen in the upper cretaceous lower paleocene succession they are considered to represent basin facies in the lower levels passing upward into sediment attributed to distal fan facies on the basis of bed thickness distributions and bioclastic hemipelagic ratios agglomerates occur as laterally discontinuous mass flow deposits which formed on the slopes of local volcanoes located in the deeper part of the basin thin lava sheets are the products of stratovolcanoes which result from regional tectonic subsidence olistoliths occurring at several stratigraphic levels probably are the result of seismic events related to contemporaneous volcano tectonic activity two major turbiditic megacycles occur also in the middle and upper parts of the succession middle and upper paleocene the lower megacycle of this sequence conforms to the distal division of a suprafan lobe while the upper part is marked by a conspicuous thickening and coarsening upward character indicating a suprafan lobe environment this evidence is consistent with an overall progradation of the fan complex during the paleocene paleocurrent features and slump structures indicate that the marginal slopes of the basin extended in a northeast southwest direction and were inclined to the north sedimentologic stratigraphic tectonic and volcanic data from this sequence suggest that during the paleocene this area formed as an arc related basin

jurassic arc volcanism on crimea ukraine implications for the paleo subduction zone configuration of the black sea region article i nfo the early cretaceous and younger opening of the black sea has obliterated much of the older record of tethyan subduction below southeastern europe the earlier mesozoic evolution was dominated by opening and closure of tethyan oceans between gondwana and laurasia with their consumption at least in part accommodated along the southern eurasian margin crimea ukraine a peninsula in the northern black sea represents the northernmost region of southeastern europe that exposes a record of a pre cretaceous tethyan active margin to shed new light on the paleosubduction zone configuration of the southeastern european margin in the jurassic we report 40

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

a palaeomagnetic study of the sivas basin central turkey crustal deformation during lateral extrusion of the anatolian block abstract the sivas basin is a complex collage of eocene and younger rocks located within the wedge shaped eastern margin of the anatolian block between the dextral north anatolian fault zone and the sinistral eastern anatolian fault zone it has been subject to ongoing deformation by movement of the arabian block into eurasia and concomittant sideways expulsion of the anatolian block post collisional deformation since mid miocene times has been dominated by n s to nw se compression expressed by thrusting and strike slip faulting cretaceous and eocene rocks were magnetically overprinted to variable degrees during the collisional phase although these overprints have since been rotated mostly anticlockwise rocks emplaced during the neotectonic history are high fidelity palaeomagnetic recorders of subsequent block movements regional anticlockwise rotation is recognised across the basin with differential rotation of fault and thrust bounded blocks an absence of perceptible differences between group mean rotations identified from miocene pliocene and quaternary units shows that most regional rotation has been concentrated within the latest phase of the neotectonic history during quaternary times at an average rate of 10 ma commencement of this rotation postdates initiation of the north anatolian fault zone implying that compression following collision was accomodated initially by crustal thickening during late miocene and pliocene times subsequent anticlockwise rotations have resulted from sideways expulsion of blocks to the south of the central anatolian thrust along major ne sw sinistral faults to achieve the crustal shortening resulting from n s compression these fault orientations and their sense of motion are explained by a prandtl model involving deformation of a triangular plastic terrane the anatolian block between two rigid plates eurasia and afro arabia the variations in regional rotation identified by palaeomagnetism show that average contemporary anticlockwise rotation of anatolia revealed by gps data 1 2 ma is achieved by variable and locally large block rotations between major thrusts and strike slip faults

late cretaceous to middle eocene magmatism and metallogeny of a portion of the southeastern anatolian orogenic belt east central turkey rapidly changing ore deposit types in the late cretaceous and early tertiary in the southeastern anatolian orogenic belt in east central turkey from baskil on the south to divrigi on the north broadly reflect shifting tectonic environments in an evolving collisional orogen a part of the extensive tethyan orogen late cretaceous 83 79 ma subduction related arc magmatism in the baskil arc was followed by extension that exhumed the metamorphic basement unroofed the obducted ophiolites and filled basins with maastrichtian to paleocene subaerial and submarine sedimentary rocks calc alkaline divrigi pluton 76 73 ma and alkaline igneous rocks hasancelebi and keban districts 76 74 ma accompanied post baskil arc extension in the early to middle eocene shallow and locally voluminous intrusions of intermediate composition copler kabatas bizmisen calti dedeyazi polat karamadazi and horoz localized mainly along major strike slip faults formed during closure of the neotethyan ocean these intrusions are dated between 50 and 44 ma peaking at 48 ma geochemical data from a suite of igneous rock samples across the transect reflect temporally based changes from arc type to late orogenic environments as demonstrated by late cretaceous rocks in the baskil area on the south and the more deeply eroded late cretaceous plutons in the divrigi area on the north divrigi these magmatic products were followed in the eocene by calc alkaline magmatism related to either incipient slab rupture or crustal scale faults that cut from northeast copler kabatas bizmisen calti and polat cavuslu to southwest karamadazi and horoz obliquely across the transect the multielement patterns for the late cretaceous magmatic rocks resemble the patterns for magmas generated in enriched source regions compared to primitive mantle and mid oceanic ridge basalt locally at divrigi hasancelebi and keban the geochemical characteristics are suggestive of the influx of low field strength elements into the mantle source regions from a subducted slab and an arc to postcollisional to late orogenic setting for their generation eocene magmatic rocks display similar geochemical characteristics regardless of the geographic setting and associated hydrothermal system their characteristics favor a subduction zone enrichment that was inherited either from an older event or from an older slab or from a mantle wedge contaminated by a contemporaneous subduction component 40ar 39ar and u pb geochronology on biotite zircon k feldspar hornblende and sericite from a suite of magmatic rocks and alteration zones defines three magmatic related metallogenic events in the southeastern anatolian orogenic belt between 78 and 44 ma the oldest metallogenic event between 78 to 74 ma is related to arc type calc alkaline magmatic rocks 83 79 ma intruded into the bitlis poturge and malatya keban metamorphics and overlying komurhan ispendere ophiolites of tauride platform uneconomic porphyry type cu au systems formed at topalkem baskil elazig and ispendere sisman malatya a second metallogenic event between 74 and 69 ma is contemporaneous with postcollisional exhumation and extension related magmatism during this event calc alkaline followed by alkaline magmatism 76 73 ma was accompanied by formation of iron oxide copper gold iocg systems at 74 to 73 ma at divrigi sivas alkaline magmatism at 76 to 74 ma is associated with iocg systems at hasancelebi malatya and porphyry cu mo and pb zn veins at keban elazig the youngest metallogenic event between 50 and 40 ma is represented by porphyry cu au deposits associated with calc alkaline intrusive complexes at copler and kabatas and fe skarns at karamadazi horoz dedeyazi and bizmisen calti

apatite fission track data from central anatolian granitoids turkey constraints on neo tethyan closure 1 apatite fission track age versus elevation profiles and temperature time path modeling indicate an early to middle paleocene 57 62 ma rapid exhumation of the middle to late cretaceous granitoids in central anatolia and an oligocene 28 30 ma rapid exhumation of the eocene kosedag batholith in the ne sivas region part of eastern central pontides the early to middle paleocene rapid exhumation is thought to result from a regional compressional regime following the collision of the eurasian plate and the tauride anatolide platform at the closure of the izmir ankara erzincan branch of the northern neo tethys the oligocene accelerated exhumation of the kosedag batholith is contemporaneous with the oligo miocene closure of the southern neo tethys which juxtaposed the amalgamated eurasian and tauride anatolide platform and the african arabian plate along the bitlis zagros suture in southeast anatolia the compressional regime due to this collision affected a large area between the greater caucasus in the north and northern african arabian plate in the south

jurassic accretionary complex and ophiolite from northeast turkey no evidence for the cimmerian continental ribbon permian triassic and late cretaceous accretionary complexes ascribed to the consumption of two distinct oceans the paleo and neo tethys are exposed over extensive areas in the eastern mediterranean region however a separating continental ribbon the so called cimmeride continent between the paleo and neo tethys during early mesozoic time cannot be defined here we report a previously unknown early jurassic metamorphic oceanic accretionary complex and ophiolite from northeast turkey bounded by oceanic accretionary complexes of permian triassic and late cretaceous age to the north and the south respectively without a continental domain in between this special tectonic position and widespread coexistence of permian triassic and late cretaceous accretionary complexes alongside the izmir ankara erzincan suture imply that 1 the southern margin of laurasia in the eastern mediterranean region grew by episodic accretionary processes from late paleozoic to end mesozoic time without involvement of a cimmerian continental ribbon and 2 the paleo tethys and northern branch of the neo tethys were not distinct oceans in the eastern mediterranean region

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

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

effects of plate convergence obliquity on timing and mechanisms of exhumation of a mid crustal terrain the central anatolian crystalline complex abstract apatite fission track ft ages from the central anatolian crystalline complex cacc a microcontinent within the turkish segment of the alpine himalayan orogen vary dramatically from north to south this variation correlates with differences in the obliquity of convergence of the continental fragment relative to the pontide belt for the northern cacc and the tauride belt for the southern cacc the northern cacc was deformed and metamorphosed during late cretaceous orogen normal collision and was exhumed from the mid crust to shallow crustal levels 50 ma to the present in contrast the southern cacc nigde massif was initially deformed and metamorphosed during late cretaceous contraction but subsequently developed as a metamorphic core complex in a wrench dominated regime and was exhumed to

from submarine continental accretion to arc continent orogenic evolution the thermal record in southern taiwan constraining the timing of initial collision is critical for understanding how long term plate convergence is accommodated at collisional plate boundaries reevaluation of the age of collision from orogenic thermal evolution requires distinguishing the onset of submarine continental accretion from earlier oceanic subduction and subsequent subaerial orogenic evolution we present new thermochronological constraints from the first age elevation relationship transect in taiwan and zircon and apatite fission track ages from sediments in the western foreland our data reveal the onset of cooling from at least 7 1 1 3 ma at a minimum rate of 21 c m y in the submarine sedimentary wedge followed by a marked acceleration of subaerial exhumation after ca 3 2 0 6 ma at an average rate of 1 7 km m y our data reflect the effect of margin architecture as taiwan evolved from submarine accretion of the distal extremely thinned continental margin to crustal thickening of the proximal margin and orogenic development

driving the upper plate surface deformation by slab rollback and mantle flow the relative contribution of crustal and mantle processes to surface deformation at convergent plate margins is still controversial conflicting models involving either extrusion mechanisms or slab rollback in particular were proposed to explain the surface strain and kinematics across the tethyan convergent domain here we present new high resolution 3d thermo mechanical numerical joint models of continental collision oceanic subduction and slab tearing which for the first time allow self consistent reproduction of first order tethyan tectonic structures such as back arc rifting and large scale strike slip faults accommodating continental escape these models suggest that mantle flow due to slab rollback and tearing can modulate the surface strain and kinematics by locally enhancing trench retreat and dragging the upper plate from below these results highlight the active role of the asthenospheric flow in driving the surface strain not only by modulating the vertical stresses and producing dynamic topography but also through sub horizontal motion we discuss the implications of these findings based on observations across the aegean anatolian and eastern indian eurasian domains though similar considerations may as well apply to other settings

structure and deformation history of the bitlis suture near lake hazar southeastern turkey detailed mapping of the bitlis suture zone near lake hazar shows that it is composed of three tectonostratigraphic units which crop out as distinct north dipping thrust slices from south to north these are the puturge metamorphic complex the maden melange and the elazig igneous complex the puturge metamorphic complex consists of pre tertiary continental margin sediments metamorphosed to the greenschist facies during the campanian maastrichtian and deformed by four generations of structures these are in sequence 1 isoclinal folds and a transposition foliation 2 open folds crenulation cleavage and north dipping thrust faults 3 kink bands and 4 small displacement faults the maden melange represents middle eocene back arc basin sediments and volcanics metamorphosed to the greenschist facies and deformed by three generations of structures 1 a north dipping cleavage 2 kink bands and 3 small displacement faults the elazig igneous complex comprises an imbricated maastrichtian early eocene island arc and young marginal basin terrain thrust faults between units are north dipping listric and form a thin skinned system these features suggest the following deformational and tectonic history the puturge metamorphic complex was generated by isoclinal folding and metamorphism of sediments composing the arabian continental margin during campanian maastrichtian ophiolite obduction to the south the elazig arc developed on the deformed margin because of subsequent southward subduction of oceanic lithosphere the arc migrated to the north opening a back arc basin by the early eocene the back arc basin was filling with volcaniclastics of the maden melange and the elazig arc collided with a continent to the north during middle to late eocene convergence caused thrust stacking of the elazig maden and puturge complexes second generation deformation in the puturge complex and first generation deformation in the maden melange continued convergence with the arabian plate in the late miocene caused kink banding in the puturge and maden complexes since the late miocene this convergence has been accommodated by shortening and thickening along numerous internal faults

nw iran eastern turkey present day kinematics results from the iranian permanent gps network abstract a network of continuous gps stations has been installed in nw iran since 2005 to complement the survey gps network already existing in the region we present the 1999 2009 gps derived velocity field for this region based on the continuous and survey mode observations the results confirm a right lateral slip of 7 1 mm yr for the north tabriz fault in agreement with previous studies this rate is consistent with earthquakes of magnitude 7 7 3 and recurrence times of 250 300 yr the higher spatial coverage of the new network shows that deformation is localized in the vicinity of the chalderan south gailatu siah cheshmeh khoy fault and the north tabriz fault however the eastern end of the north tabriz fault appears to cross mount bozgush rather than following its southern foothills this new velocity field does not indicate the 8 mm yr of nne ssw extension suggested earlier for the region but rather shows lower extension of 1 2 1 mm yr across the eastern segment of the north tabriz fault and the talesh to the west the chalderan and the western north tabriz fault segment act like pure strike slip faults without significant extension or compression the denser network in the rudbar earthquake region ms 7 3 1992 shows no significant motion across the fault suggesting that the recurrence time of earthquakes like the rudbar event must be very long the lack of substantial compressive strain and the sharp azimuth change of the velocity vectors in the transition zone from arabia to lesser caucasus motion imply that processes other than extrusion possibly related to old subduction or delamination contribute to active deformation

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

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

characteristic features and structural evolution of a post collisional basin the sivas basin central anatolia turkey abstract the ene ssw trending sivas basin is located at the easternmost wedge like tip of the central anatolian block and exhibits characteristics of two other basins one in west central anatolia and the other in eastern anatolia the sivas basin started to form within a collisional mosaic during maastrichtian time with the pre maastrichtian basement the latter composed of continental metamorphic rocks jurassic lower cretaceous platform carbonates of the tauride belt and ophiolites and ophiolitic melange derived from closure of the northern branch of neo tethys similar tertiary basins were developed on comparable collisional mosaics in other parts of anatolia the sivas basin is asymmetrical in both the longitudinal and transversal directions its infill is dominated by a thick maastrichtian tertiary shallow marine continental succession resting unconformably on pre maastrichtian basement rocks and dissected into several subbasins this infill consists of post collisional deposits which overlie paleotectonic units unconformably and each subbasin is bounded by northeast southwest trending oblique slip faults exhibiting dominant strike slip the subbasins are characterized by contrasting stratigraphic successions although all are composed of interstratified continental and shallow marine facies both the northern and southern margins of the subbasins include upper eocene olistostromes containing mega blocks of varied origin the latter are sourced in paleotectonic units and were reworked in a shallow marine depositional setting the fill of the middle subbasins exhibits strong vertical and lateral facies changes characterized by local and regional unconformities and includes continental to shallow marine volcanic rocks this basin was deformed under north south directed compression during late pliocene quaternary times during the neotectonic phase of deformation this deformation divided the basin into new small scale mainly pull apart subbasins including those at imranli ishani altinyayla and arkisla from stratigraphic and structural correlations a post collisional intra continental basin model for the sivas basin is preferred

late cretaceous early eocene tectonic development of the tethyan suture zone in the erzincan area eastern pontides turkey six individual tectonostratigraphic units are identified within the izmir ankara erzincan suture zone in the critical erzincan area of the eastern pontides the ayikayasi formation of campanian maastrichtian age is composed of bedded pelagic limestones intercalated with polymict massive conglomerates the ayikayasi formation conformably overlies the tauride passive margin sequence in the munzur mountains to the south and is interpreted as an underfilled foredeep basin the refahiye complex of possible late cretaceous age is a partial ophiolite composed of 75 by volume serpentinized peridotite mainly harzburgite 20 diabase and minor amounts of gabbro and plagiogranite the complex is interpreted as oceanic lithosphere that formed by spreading above a subduction zone unusual screens of metamorphic rocks e g marble and schist locally occur between sheeted diabase dykes the upper cretaceous karayaprak melange exhibits two lithological associations 1 the basalt radiolarite serpentinite association including depleted arc type basalts 2 the massive neritic limestone lava volcaniclastic association that includes fractionated intermediate composition lavas and is interpreted as accreted neotethyan seamount s the several kilometre thick karadag formation of campanian maastrichtian age is composed of greenschist facies volcanogenic rocks of mainly basaltic to andesitic composition and is interpreted as an emplaced upper cretaceous volcanic arc the campanian early eocene sutpinar formation 1500 m thick is a coarsening upward succession of turbiditic calcarenite sandstone laminated mudrock volcaniclastic sedimentary rocks that includes rare andesitic lava and is interpreted as a regressive forearc basin the late paleocene eocene sipikor formation is a laterally varied succession of shallow marine carbonate and siliciclastic lithofacies that overlies deformed upper cretaceous units with an angular unconformity structural study indicates that the assembled accretionary prism supra subduction zone type oceanic lithosphere and volcanic arc units were emplaced northwards onto the eurasian margin and also southwards onto the tauride gondwana related margin during campanian maastrichtian time further mainly southward thrusting took place during the eocene in this area related to final closure of tethys our preferred tectonic model involves northward subduction supra subduction zone ophiolite genesis and arc magmatism near the northerly eurasian margin of the mesozoic tethys

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

formation of the rocky mountains western united states a continuum computer model one hypothesis for the information of the rocky mountain structures in late cretaceous through eocene time is that plate of oceanic lithosphere was underthrust horizontally along the base of the north american lithosphere the horizontal components of the motion of this plate are known from paleomagnetism and the edge of the region of flat slab can estimated from reconstructed patterns of volcanism new techniques of finite element modeling allow prediction of the thermal and mechanical effects of horizontal subduction on the north american plate a model that has a realistic temperature dependent rheology and a simple plane layered initial condition is used to compute the consequences of horizontal underthrusting in the time interval 75 million to 30 million years before present successful prediction of this model include i the location amount and direction of horizontal shortening that has been inferred from laramide structures ii massive transport of lower crust from southwest to northeast iii the location and timing of the subsequent extension in metamorphic core complexes and the rio grande rift and iv the total area eventually involved in basin and range style extension in a broad sense this model has predicted the belt of laramide structures the transport of crust from the coastal region to the continental interior the subsequent extension in metamorphic core complexes and the rio grande rift and the geographic region of late tertiary basin and range extension its principal defects are that i many events are predicted about 5 million to 10 million years too late and ii the wave of crustal thickening does not travel far enough to the east reasonable modifications to the oceanic plate kinematics and rheologies that were assumed may correct these defects the correspondence of model predictions to actual geology is already sufficiently close to show that the hypothesis that horizontal subduction caused the laramide orogeny is probably correct the rocky mountain thrust and reverse faults formed in an environment of east west to northeast southwest compressive stress that was caused by the viscous coupling between the oceanic plate and the base of the north american crust nonuniform crustal thickening by simple shear transport also caused relative uplifts therefore this model is consistent with both of the range forming mechanisms that have been inferred 1 a new proposal that arises from this simulation is that horizontal subduction also caused the subsequent extensional basin and range taphrogeny by stripping away the mantle lithosphere so that the crust was exposed to hot asthenosphere after the oceanic slab dropped away

k ar age whole rock and isotope geochemistry of a type granitoids in the divrigi sivas region eastern central anatolia turkey abstract the bimodal a type dumluca and murmana granitoids consist of felsic monzonitic syenitic and mafic gabbroic dioritic and monzogabbroic monzodioritic rocks which were intruded into the cenomanian turonian supra subduction zone type divrigi ophiolitic melange new hornblende and biotite k ar dates yield cooling ages ranging from 72 to 77 ma and from 68 to 77 ma for the felsic and mafic rocks respectively in the dumluca and murmana granitoids felsic and mafic rocks of these intrusions have a metaluminous high k alkaline composition however highly evolved members of the felsic rocks are peraluminous in character trace element geochemistry data indicate that mafic and felsic rocks have their own geochemical characteristics which show different sources the combined evidence of the trace element radiogenic and stable isotope geochemistry from the dumluca and murmana granitoids suggest that the mafic rocks were derived exclusively from an enriched mantle mafic magma em ii but the felsic rocks were derived from a hybrid felsic magma the hybrid felsic magma was generated by the mixing of the mantle derived mafic with another crustal derived silicic melt the composition of some mafic rocks from murmana granitoid suite is thought to be derived from an enriched mantle source that may have been metasomatized by earlier subduction derived fluids thus carrying the subduction signature in the source material the local and regional geology suggest an early late cretaceous post collisional extension related geodynamic setting following the collision between the tauride anatolide platform and an oceanic island arc comprising the supra subduction zone type central anatolian ophiolite

petrogenesis of the post collisional volcanic rocks from the borcka artvin area implications for the evolution of the eocene magmatism in the eastern pontides ne turkey abstract whole rock geochemistry 40 ar 39 ar data and sr nd isotopes are presented for the eocene borcka volcanic rocks on the eastern corner of the eastern pontide orogenic belt ne turkey borcka artvin volcanic rocks are divided into three suites basic dyke borcka basalt and civankoy suite these rocks contain plagioclase an 49 88 clinopyroxene wo 38 49 en 38 54 fs 8 25 hornblende mg 0 57 0 74 phenocrysts and magnetite titanomagnetite and apatite microphenocrysts 40 ar 39 ar ages on hornblendes ranging from 46 9 0 1 to 39 9 0 5 ma within the middle eocene the volcanic rocks show tholeiitic calc alkaline affinities and have low to medium k contents they are enriched in large ion lithophile lile and light rare earth elements lree with pronounced depleted high field strength elements hfse the chondrite normalized ree patterns la cn lu cn 1 19 show low to medium enrichment indicating similar sources for the rock suite initial 87 sr 86 sr values 87 sr 86 sr 46 ma vary between 0 70423 and 0 70495 while initial 143 nd 144 nd values 143 nd 144 nd 46 ma lie between 0 51263 and 0 51285 the main solidification processes involved in the evolution of the volcanics consist of fractional crystallization with minor amounts of crustal contamination all our evidences support the conclusion that the parental magma of the rocks probably derived from an enriched mantle previously metasomatized by fluids derived from subducted slab in a post collisional extension related geodynamic setting