conditions and timing of incorporation of ophiolite into orogenic crust during oblique convergence central anatolia ophiolitic fragments scattered over a wide area of central anatolia exhibit varying degrees of metamorphism from unmetamorphosed to upper amphibolite facies although geochemical similarities suggest they are all part of the central anatolian ophiolite cao magmatic crystallization of oceanic crust in the cao at 91 ma coincided with high grade metamorphism of rocks that underlie the southern highest grade part of the cao raising questions about the tectonic relationship of the ophiolite to underlying metasedimentary and plutonic rocks new geochronology results show that the 40ar 39ar hornblende age of amphibolite facies metagabbro in the high grade metamorphic part of the cao is 87 ma similar to hornblende ages from amphibolite in the underlying nigde metamorphic plutonic massif biotite in a deformed quartzofeldspathic rock associated with high grade meta ophiolitic rocks yielded an 40ar 39ar age of 78 ma similar to biotite ages from the nigde massif hornblende in gabbro from unmetamorphosed cao yielded an older 40ar 39ar age of 90 ma similar to the previously determined crystallization age of the ophiolite these data indicate that the southern part of the ophiolite was incorporated into and therefore metamorphosed and deformed with the orogenic mid crust now exposed in the nigde metamorphic plutonic complex whereas the northern unmetamorphosed part of the ophiolite was obducted onto the continent this distinct difference in different parts of the ophiolite may indicate oblique collision or irregularities in the continental margin resulting in part of the ophiolite being incorporated into the orogenic crust and subsequently exhumed and cooled with it and another part being obducted

u pb dating of monazite and its application to geological problems monazite is an underutilized mineral in u pb geochronological studies of crustal rocks it occurs as an accessory mineral in a wide variety of rocks including granite pegmatite felsic volcanic a

kinematics of a former oceanic plate of the neotethys revealed by deformation in the ulukisla basin turkey kinematic reconstruction of modern ocean basins shows that since pangea breakup a vast area in the neotethyan realm was lost to subduction here we develop a first order methodology to reconstruct the kinematic history of the lost plates of the neotethys using records of subducted plates accreted to former overriding plates combined with the kinematic analysis of overriding plate extension and shortening in cretaceous paleogene times most of anatolia formed a separate tectonic plate here termed anadolu plate that floored part of the neotethyan oceanic realm separated from eurasia and africa by subduction zones we study the sedimentary and structural history of the ulukisla basin turkey overlying relics of this plate to reconstruct the tectonic history of the oceanic plate and its surrounding trenches relative to africa and eurasia our results show that upper cretaceous oligocene sediments were deposited on the newly dated suprasubduction zone ophiolites 92 ma which are underlain by melanges metamorphosed and nonmetamorphosed oceanic and continental rocks derived from the african plate the ulukisla basin underwent latest cretaceous paleocene n s and e w extension until 56 ma following a short period of tectonic quiescence eo oligocene n s contraction formed the folded structure of the bolkar mountains as well as subordinate contractional structures within the basin we conceptually explain the transition from extension to quiescence to shortening as slowdown of the anadolu plate relative to the northward advancing africa anadolu trench resulting from collision of continental rocks accreted to anadolu with eurasia until the gradual demise of the anadolu eurasia subduction zone

structural geological problems in gumusler archeological site and monastery there are many underground settlings opened in historical times in cappadocia region and the gumusler monastery is one of these the monastery is a rock monastery church located in approximately 8 km northeast of nigde the most important characteristics of the monastery dated in 11th century ac are that it is an important settlement and touristic area that contains the most preserved frescoes in cappadocia region for this purpose were determined the geological features of the observed units in the areas where the monastery is located and the surroundings were determined engineering geological problems are mentioned for the negative effects of the discontinuities especially in the monastery part during field studies stones with different color and textural characteristics were taken into account and sampling was carried out from four different levels on representative samples laboratory studies were conducted for determining the mineralogical chemical and petrographic and geomechanical properties underground cavities in the region were opened in the lower part of the kizilkaya ignimbrite which has relatively more rock fragments higher amount of rock fragments in the lower part makes this level easier to cave in low welding rate of the rock is believed to be the cause of having relatively low values of engineering properties of the lower levels of examined ignimbrites ignimbrites in these levels are more sensitive against atmospheric conditions than those in the upper levels this study is the first study to determine engineering geology problems in the gumusler archeological area and provide data to planned conservation measures

miocene nne directed extensional unroofing in the menderes massif southwestern turkey structural investigations in the central part of the menderes massif odemio kiraz submas sif reveal the presence of a large scale low angle extensional shear zone with a top to the n ne shear sense regional ductile deformation was accompanied by the intrusion of two syntectonic granodiorites that have been dated with the 40 ar 39 ar method one hornblende isochron age of 19 5 1 4 ma and two biotite plateau ages of 13 1 0 2 and 12 2 0 4 ma respectively constrain that extension was already active in the early miocene successive tectonic denudation of the odemio kiraz submassif resulted in the formation of a n dipping detachment fault in which ductile fabrics were severely reworked by cataclasis under decreasing temperature syntectonic neogene sediments currently exposed along the southern margin of the gediz graben were deposited in the hanging wall of the extensional fault system and were tectonically emplaced onto the cataclasites during progressive exhumation minor rotation c 15 caused southward tilting of the sediments ongoing nne directed extension created a steep normal fault that truncates the detachment fault and constitutes the southern boundary fault of the gediz graben

metamorphism during alpine crustal thickening and extension in central anatolia turkey the nigde metamorphic core complex the nig de massif a metamorphic core complex in central anatolia high temperature reactions can obliterate assemblages turkey contains petrologic evidence for the transition from alpine formed during earlier lower temperature phases of meta crustal thickening to extension and exhumation of high grade mid morphism this can hinder use of petrologic information crustal rocks sillimanite potassium feldspar gneiss formed and to interpret tectonic processes if reaction textures are partially melted during barrovian metamorphism and records max preserved however rocks may record a range of pres imum conditions of 5 6 kbar 700 c the two mica uckapili sure temperature conditions from their prograde and granite and a related dike suite intruded the migmatitic metapelitic or retrograde paths and a more complete picture of the rocks forming a contact aureole that contains andalusite and tectonic evolution of a terrane can be reconstructed of cordierite these low pressure minerals indicate that crustal thick particular interest are the mechanisms and timing of ening was followed by exhumation of mid crustal rocks to relatively transition from contraction to extension and the ac shallow depths 10 km at lower temperatures before the em companying exhumation of middle to lower crustal placement of granitic magma formation of andalusite was followed rocks the present study describes a medium pressure by a second prograde episode of sillimanite growth during low high temperature terrane the nig de massif fig 1 in pressure high temperature metamorphism in the central part of the central anatolia turkey that developed as a meta massif where magmatism was most extensive a generalized p t morphic core complex in response to alpine crustal path for the highest grade rocks therefore consists of an initial thickening metamorphic rocks in the central high grade clockwise path with a late thermal spike and characterizes burial part of the massif record in their mineral assemblages and subsequent exhumation accompanied by magmatism reaction textures and structures the processes of burial exhumation and accompanying magmatism

the tectonic history of the nigde kirsehir massif and the taurides since the late mesozoic paleomagnetic evidence for two phase orogenic curvature in central anatolia the nigde kirsehir massif known also as the central anatolian block is bordered by the sutures of the neotethys ocean the massif suffered several deformation phases during and after the consumption of the surrounding oceans and the post collisional events of the continental pieces of anatolia in latest cretaceous to miocene previous paleomagnetic studies on the nigde kirsehir massif and its surroundings displayed either insufficient data or have claimed large rotations and or remagnetization in order to understand the tectonic history of the nigde kirsehir massif and its adjacent blocks we have sampled 147 different sites in the age range of upper jurassic to miocene from the nigde kirsehir massif throughout its w sw and e se boundaries and the central southeastern taurides the results display that except the limestones in central taurides all rocks examined carry a primary magnetization among these an important finding is that rotations between the massif and the central eastern taurides indicate an oroclinal bending with counterclockwise rotation of r 41 1 7 6 in the se and clockwise rotation of r 45 9 9 3 in the central taurides from upper cretaceous rocks with respect to the african reference direction paleomagnetic rotations in the se taurides are compatible with the vergent direction of the thrusts generated from consumption of the intra tauride ocean prior to post collisional convergence between taurides and the massif in the central taurides it has been shown that the clockwise rotation of 45 9 9 3 started in middle eocene because of a remagnetization in upper creataceous limestones the deformation was linked to the final closure of the southern neotethys and the collision between the african and eurasian plates in the nigde kirsehir massif counterclockwise rotation up to 25 5 7 3 is recognised during middle eocene and interpreted in terms of block rotation together with the taurides after the miocene a counterclockwise rotation of 16 8 3 9 along the eastern taurides shows that this area was mostly affected by the westward movement of anatolia despite the nigde kirsehir massif and its sw w area the central taurides which is recognised as stable with counterclockwise rotation less than 10

seismic structure crustal architecture and tectonic evolution of the anatolian african plate boundary and the cenozoic orogenic belts in the eastern mediterranean region the modern anatolian african plate boundary is represented by a north dipping subduction zone that has been part of a broad domain of regional convergence between eurasia and afro arabia since the latest mesozoic a series of collisions between gondwana derived ribbon continents and trench roll back systems in the tethyan realm produced nearly east west trending subparallel mountain belts with high elevation and thick orogenic crust in this region ophiolite emplacement terrane stacking high p and barrovian metamorphism and crustal thickening occurred during the accretion of these microcontinents into the upper plates of tethyan subduction roll back systems during the late cretaceous early eocene continued convergence and oceanic lithospheric subduction within the tethyan realm were punctuated by slab breakoff events following the microcontinental accretion episodes slab breakoff resulted in asthenospheric upwelling and partial melting which facilitated post collisional magmatism along and across the suture zones resumed subduction and slab roll back induced upper plate extension triggered a tectonic collapse of the thermally weakened orogenic crust in anatolia in the late oligocene miocene this extensional phase resulted in exhumation of high p rocks and mediumto lower crustal material leading to the formation of metamorphic core complexes in the hinterland of the young collision zones the geochemical character of the attendant magmatism has progressed from initial shoshonitic and high k calc alkaline to calc alkaline and alkaline affinities through time as more asthenosphere derived melts found their way to the surface with insignificant degrees of crustal contamination the occurrence of discrete high velocity bodies in the mantle beneath anatolia as deduced from lithospheric seismic velocity data supports our tethyan slab breakoff interpretations pn velocity and sn attenuation tomography models indicate that the uppermost mantle is anomalously hot and thin consistent with the existence of a shallow asthenosphere beneath the collapsing anatolian orogenic belts and widespread volcanism in this region the sharp north pointing cusp isparta angle between the hellenic and cyprus trenches along the modern anatolian african plate boundary corresponds to a subductiontransform edge propagator step fault which is an artifact of a slab tear within the downgoing african lithosphere

late miocene surface uplift of the southern margin of the central anatolian plateau central taurides turkey the timing and pattern of surface uplift of miocene marine sediments capping the southern margin of the central anatolian plateau in southern turkey provide a first order constraint on possible mechanisms of regional uplift nannofossil ostracod and planktic foraminifera biostratigraphy of the basyayla section mut ermenek basin within the mut and koselerli formations suggests a tortonian age for marine sediments unconformably capping basement rocks at 2 km elevation the identification of biozone mmi 12a 7 81 8 35 ma from planktic foraminifera in the upper part of the section provides the tightest constraint on the age which is further limited to 8 35 8 108 ma as a result of the reverse polarity of the collected samples chron 4r 1r or 4r 2r this provides a limiting age for the onset of surface uplift at the margin of one of the world s major orogenic plateaus from which an average uplift rate of 0 24 0 25 mm yr can be calculated subhorizontal beds of the uppermost marine sediments exposed throughout the mut ermenek basin suggest minimal localized deformation with just minor faulting at the basin margin and broad antiformal deformation across the basin this implies that the post 8 ma uplift mechanism must be rooted deep within the crust or in the upper mantle published pn wave velocity data for the region are compatible with topography compensated by asthenosphere across the southern margin of the plateau showing a close match to the highest topography when elevations are filtered with a 100 km wide smoothing window uplift along the southern margin of the central anatolian plateau is also reflected by the pattern of miocene marine sediments capping the margin which form an asymmetric drape fold over the topography these observations together with tomographic evidence for slab steepening and break off beneath the eastern anatolian plateau suggest that at least some of the 2 km of post 8 ma uplift of the southern central anatolian plateau margin is compensated by low density asthenospheric mantle that upwelled following slab break off

the misis andirin complex a mid tertiary melange related to late stage subduction of the southern neotethys in s turkey abstract the mid tertiary mid eocene to earliest miocene misis andirin complex documents tectonic sedimentary processes affecting the northerly active margin of the south tethys neotethys in the easternmost mediterranean region each of three orogenic segments misis in the sw andirin central and engizek in the ne represent parts of an originally continuous active continental margin a structurally lower volcanic sedimentary unit includes late cretaceous arc related extrusives and their lower tertiary pelagic cover this unit is interpreted as an early tertiary remnant of the mesozoic south tethys the overlying melange unit is dominated by tectonically brecciated blocks 100 m across of mesozoic neritic limestone that were derived from the tauride carbonate platform to the north together with accreted ophiolitic material the melange matrix comprises polymict debris flows high to low density turbidites and minor hemipelagic sediments the misis andirin complex is interpreted as an accretionary prism related to the latest stages of northward subduction of the south tethys and diachronous continental collision of the tauride eurasian and arabian african plates during mid eocene to earliest miocene time slivers of upper cretaceous oceanic crust and its early tertiary pelagic cover were accreted while blocks of mesozoic platform carbonates slid from the overriding plate tectonic mixing and sedimentary recycling took place within a trench subduction culminated in large scale collapse of the overriding northern margin and foundering of vast blocks of neritic carbonate into the trench a possible cause was rapid roll back of dense downgoing mesozoic oceanic crust such that the accretionary wedge taper was extended leading to gravity collapse melange formation was terminated by underthrusting of the arabian plate from the south during earliest miocene time collision was diachronous in the east engizek range and se anatolia collision generated a lower miocene flexural basin infilled with turbidites and a flexural bulge to the south miocene turbiditic sediments also covered the former accretionary prism further west misis range the easternmost mediterranean remained in a pre collisional setting with northward underthrusting incipient subduction along the cyprus arc the lower miocene basins to the north misis and adana indicate an extensional to transtensional setting the ne sw linking segment andirin probably originated as a mesozoic palaeogeographic offset of the tauride margin this was reactivated by strike slip and transtension during later tertiary diachronous collision related to on going plate convergence the former accretionary wedge upper plate was thrust over the lower miocene turbiditic basins in mid late miocene time the plio quaternary was dominated by left lateral strike slip along the east anatolian transform fault and also along fault strands cutting the misis andirin complex

late cenozoic extension in northeastern greece strymon valley detachment system and rhodope metamorphic core complex the strymon valley detachment system accommodated at least 25 km of extension at the northern margin of the aegean extensional province from middle miocene through early pliocene time the primary detachment surface is exposed as a gently southwest dipping low angle normal fault similar to those widely known in core complex settings of the u s basin and range province for more than 150 km along strike from the aegean sea coast in northeastern greece northward into the struma valley of southern bulgaria hanging wall rocks in the strymon valley detachment system moved in a s53 w direction relative to the footwall resulting ultimately in the tectonic unroofing of the rhodope metamorphic core complex several segments of the strymon valley detachment have previously been interpreted as thrust faults formed during a miocene compressional event our results negate the principal evidence for this event and imply instead that extensional deformation has characterized the northern aegean region since at least middle miocene time displacement ceased on the strymon valley detachment with the late pliocene development of the strymon and drama basins we propose that those basins together with the other principal basins of the northern aegean region are subsiding above an active northeast dipping extensional detachment zone that forms a unified kinematic system with the western offshore continuation of the dextral north anatolian strike slip fault the north aegean trough if this hypothesis is correct then the north aegean trough the western strands of the north anatolian fault and the principal modern depocenters of the northern aegean region may all have originated no earlier than late pliocene time

dating the exhumation of a metamorphic dome geological evidence for pre eocene unroofing of the nigde massif central anatolia turkey the timing of exhumation of metamorphic rocks and granitoids of the nigde metamorphic dome at the southern tip of the central anatolian crystalline complex is a matter of debate according to some authors the metamorphic rocks are overlain nonconformably by a sedimentary sequence of late maastrichtian to late palaeocene age in contrast other authors recently argued that the nigde dome represents an extensional core complex of oligocene early miocene age finally unroofed during late miocene times on the one hand the results of our study contradict the latter interpretation a sedimentary sequence of earliest eocene to early middle eocene age nonconformably overlies the high grade rocks of the nigde dome on its southeastern flank pebbles from the metamorphic rocks are ubiquitous in the conglomerates of this sequence as a result the nigde metamorphic rocks must have reached the surface before eocene times or at the very beginning of the eocene at the latest the uckapili granite whose crystallization age has been inferred to be early miocene has intruded the metamorphic complex during exhumation the granite is also found as pebbles within the conglomerates of the eocene sedimentary sequence and thus is actually older than the eocene apatite fission track dates of 12 11 ma across the nigde dome do not indicate that the metamorphic rocks were still on their way to the surface at that time instead they must reflect a later event which is most probably heating during late neogene magmatism lastly there is no ductile then brittle extensional detachment in the two areas where it has been invoked that is on the western and southern flanks of the dome an extensional detachment nevertheless exists at the top of the nigde dome best documented in its northern part where the detachment fault superposes a superficial unit made up of massive ophiolitic rocks onto the high grade metamorphic sequence field evidence indicates that this detachment developed before eocene times on the other hand our observations do not confirm the nonconformity of the sedimentary sequence dated as late maastrichtian late palaeocene onto the nigde high grade rocks field relations show either a tectonic contact between the two or the direct nonconformity of the eocene sediments onto the metamorphic rocks the lack of coarse clasts originating from the nigde high grade rocks within the maastrichtian palaeocene sequence further suggests that the metamorphic dome did not reach the surface before late palaeocene times these results compare well with available data from the northwestern part of the central anatolian crystalline complex suggesting that exhumation has been broadly synchronous on the scale of the massif as a result of an episode of high magnitude extension that affected the region in campanian to palaeocene times

magmatism as an essential driving force for formation of active metamorphic core complexes in eastern papua new guinea the d entrecasteaux islands in eastern papua new guinea are composed of a number of active metamorphic core complexes which have been intruded by granodiorite plutons during their formation the plutons do not appear to have been intruded by diapiric processes as previously suggested late relatively undeformed plutons form flat lying bodies which crosscut structural boundaries and are strongly discordant to core complex shear zones granodiorite magmatism and the development of the metamorphic core complexes have occurred in a linear zone which coincides with a zone of thick crust and rugged topography it is proposed that plutonism facilitated deformation in ductile extensional shear zones which resulted in tectonic exhumation of deep crustal rocks and formation of the metamorphic core complexes the source of the plutons is thought to be related to a linear zone of mantle upwelling beneath the islands related to the propagation of the woodlark seafloor spreading center into continental crust it is suggested that a localized heat source of this type which can provide heat and magmatic material to the crust is essential for the development of metamorphic core complexes

timing constraints of orogeny to cratonization thermochronology of the paleoproterozoic trans hudson orogen manitoba and saskatchewan canada abstract a comprehensive thermochronometric investigation across a 600 km transect of the paleoproterozoic trans hudson orogen tho in canada has resolved two first order thermal events 1 widespread peak metamorphism at 1 82 1 79 ga associated with terrane amalgamation and 2 a late collisional metamorphic episode at ca 1 77 ga that is characterized by significant strike slip deformation and rapid cooling geophysical observations of the lithosphere beneath the tho reveal crust that is markedly different on either side of the crustal scale tabbernor sturgeon weir tsw strike slip fault system which offsets lower crustal reflectors the tho east of the fault system records u pb titanite and total pb monazite domain ages that are relatively indistinguishable from 40ar 39ar hornblende and mica cooling ages indicating rapid cooling and perhaps exhumation following 1 77 ga metamorphism seismic imaging indicates the eastern orogen is an irregular package of stacked crustal blocks and our thermochronometric data demonstrate it behaved as a single coherent element shortly 20 30 m y following cessation of convergence in contrast rocks located west of the tsw fault system cooled distinctly later preserving 40ar 39ar muscovite and biotite ages between 1 74 and 1 72 ga this crustal architecture delineated from seismic surveys illustrates a more homogeneous slightly 5 km thinner crust in the case of this orogen apparent stabilization and cratonization occurred ca 100 m y after peak terrane amalgamation and notably the orogen was likely cratonized as two blocks east and west of the tsw fault system

southern menderes massif an incipient metamorphic core complex in western anatolia turkey in the southern sector of the menderes massif north of selimiye milas augen gneisses interpreted as a deformed peraluminous granite have been dynamothermally metamorphosed and are surrounded by and intrude a regionally metamorphosed palaeozoic envelope the granitic rocks exhibit a moderately dipping mylonitic foliation and nne ssw trending mineral elongation lineation the progressive deformation of the granitic rocks produces a structural sequence typical of an extensional shear zone marked from bottom to top by a very thick extensive zone of mylonites followed in turn by brecciated mylonite and cataclasite the kinematic indicators exhibit a top to the south down dip sense of shear these structures are attributed to exhumation of the granitic rocks of the massif along a major south dipping normal sense shear zone that accommodated crustal extension during late oligocene collapse of the orogen in western turkey thus the southern menderes massif may be interpreted as the exhumed footwall of a major extensional shear zone and possibly as an incipient core complex

geology and thermochronology of tertiary cordilleran style metamorphic core complexes in the saghand region of central iran an 100 km long north south belt of metamorphic core complexes is localized along the boundary between the yazd and tabas tectonic blocks of the central iranian micro continent between the towns of saghand and posht e badam amphibolite facies mylonitic gneisses are structurally overlain by east tilted supracrustal rocks including thick 1 km steeply dipping nonmarine siliciclastic and volcanic strata near the detachment the neybaz chatak fault the gneisses are generally overprinted by chlorite brecciation crosscutting relationships along with u pb zircon and 40 ar 39 ar age data indicate that migmatization mylonitic deformation volcanism and sedimentation all occurred in the middle eocene between ca 49 and 41 ma the westernmost portion of the tabas block immediately east of the complexes is an east tilted crustal section of neoproterozoic cambrian crystalline rocks and metasedi mentary strata 10 km thick the 40 ar 39 ar biotite ages of 150 160 ma from structurally deep parts of the section contrast with ages of 218 295 ma from shallower parts and suggest late jurassic tilting of the crustal section these results define three events 1 a late jurassic period of upper crustal cooling of the western tabas block that corresponds to regional jurassic cretaceous tectonism and erosion recorded by a strong angular unconformity below mid cretaceous strata throughout central iran 2 profound approximately east west middle eocene crustal extension plutonism and volcanism ca 44 40 ma and 3 2 3 km of early miocene ca 20 ma erosional exhumation of both core complex and tabas block assemblages at uppermost crustal levels resulting from significant north south shortening the discovery of these and other complexes within the mid tertiary magmatic arcs of iran demonstrates that cordilleran style core complexes are an important tectonic element in all major segments of the alpine himalayan orogenic system

new insights from 40ar 39ar laserprobe dating of white mica fabrics from the pelion massif pelagonian zone internal hellenides greece implications for the timing of metamorphic episodes and tectonic events in the aegean region

revealing the electrical properties of a gneiss dome using three dimensional magnetotellurics burial and exhumation cycles associated with faulting in central anatolia turkey abstract the nigde massif is a small scale exhumed lithospheric entity in central anatolia formed as a result of metamorphism driven by crustal thickening and migmatization its thermal and structural history records two burial and unroofing episodes induced by oblique tectonics related to an adjacent wrench zone of the ecemis fault to show the complex tectonic history of the events of this area its electrical resistivity structure was determined using three dimensional magnetotellurics forty seven high quality soundings within a frequency range of 320 hz 5000 s were utilized for this purpose the dimensionality of the data was investigated via phase tensor analyses and induction vectors a hydrothermal system that might be related to mt hasan was delineated as a widespread conductive zone in addition interpretation of the electrical resistivity models found a rheology seismicity relationship in the study area the nigde massif was depicted as a highly resistive dome like anomaly bounded by low angle detachment faults as indicated by the resistivity contrast between the massif and the adjacent features the lower boundary of the massif is defined by a resistive to conductive transition situated at 25 30 km depth beneath this transition a widespread low resistivity zone was interpreted as a partially melting lower crust this crustal feature is connected to a shallower anomaly beneath the ecemis fault zone which may infer the ascension of fluids that may be contributing to earthquake generation seismicity along the ecemis fault is overtly heterogeneous in that it tends to form a step approaching south along the fault where the lower crustal conductor is absent relevance between the seismicity and resistivity pattern denotes the presence of a fault configuration that is necessary for the yo yo tectonics

counterclockwise p t t trajectory from the metamorphic sole of a neo tethyan ophiolite turkey abstract the kiziltepe ophiolitic thrust sheet in the bolkar mountains of turkey occurs between two subparallel ophiolite belts bounding the tauride carbonate platform and represents a remnant of the cretaceous neo tethyan oceanic lithosphere it is underlain by foliated amphibolite that represents a metamorphic sole developed at the inception of an intra oceanic subduction zone in the neo tethys 92 90 ma blueschist facies overprinting of the amphibolite indicates that the metamorphic sole was dragged deeper into the subduction zone where it experienced increasing p t with cooling regional tectonic constraints suggest a maastrichtian age for the timing of this blueschist facies metamorphism sodic amphibole rich veins and crossite mg riebeckite rims on hornblende suggest that growth of blueschist facies minerals was facilitated by infiltration of fluid along fractures and grain boundaries we infer a counterclockwise p t t trajectory during which metamorphism was accompanied succeeded by rapid uplift along the northern edge of the tauride belt in late cretaceous early tertiary time

synconvergent exhumation of metamorphic core complexes in the northern north american cordillera continental metamorphic core complexes of the northern north american cordillera were exhumed during the early paleogene while the farallon north american plate convergence rate remained high such convergent boundary conditions can excite localized mid crustal exhumation in numerical simulations of collisions of softer accreted terranes with a rigid irregular craton margin resulting simulated temperature time t t paths match t t paths interpreted from observed footwall exposures in several core complexes of the northern north american cordillera including variability of maximum temperatures duration of exhumation and exhumation velocities among individual complexes

dynamic models for metamorphic core complex formation and scaling the role of unchannelized collapse of thickened continental crust abstract metamorphic core complexes at collisions between cratons and softer terranes such as in the northern north american cordillera share a set of characteristic features including spatial and temporal association of ductile mid crustal deformation with brittle normal faulting spatial coincidence with prior crustal thickening characteristic spatial scaling and limited duration and extent of deformation these properties are reproduced in numerical solutions for gravity driven collapse of a viscous crustal region under conditions where vertical stress is continuous through thickened lithosphere rigid deformable conditions such solutions allow inversion for effective mechanical properties and crustal geometry from direct observations of aspect ratio and exhumation velocity in the northern rockies core complex geometry is consistent with a twofold decrease in viscosity of the thickened cordilleran crustal welt

accelerating exhumation in the eocene north american cordilleran hinterland implications from detrital zircon u th he pb double dating

the role of the early tertiary ulukisla basin southern turkey in suturing of the mesozoic tethys ocean the maastrichtian late eocene ulukisla basin is representative of the tectonic and sedimentary evolution of prominent early tertiary basins in central anatolia including the tuzgolu and arkisla basins the ulukisla basin overlies an ophiolitic melange of late cretaceous age between the bolkar carbonate platform to the south and the nigde kirsehir metamorphic massif to the north the basin stratigraphy records successive phases of transgression subsidence volcanism evaporite deposition deformation and uplift subsidence curves are consistent with an extensional or transtensional basin origin terminated by uplift the ulukisla basin includes a thick succession c 2 km of upper paleocene lower eocene basaltic to andesitic submarine pillow lavas lava flows volcaniclastic rocks and intercalated limestones whole rock xrf chemical analysis indicates a within plate origin with a marked subduction influence believed to be inherited rather than contemporaneous the ulukisla basin formed after late cretaceous ophiolite and melange emplacement and ended with late eocene emergence deformation and onset of oligo miocene non marine deposition we propose that late cretaceous ophiolite and melange emplacement reflect initial ocean basin closure this was followed by a long period c 30 ma of microcontinental adjustment including possible strike slip palaeorotation and suture tightening during which the early tertiary ulukisla basin developed possible driving forces were regional slab pull of a relict subduction zone or oblique diachronous convergence suture tightening was complete by late eocene time marked by collisional deformation and regional uplift

tectonomagmatic evolution of bimodal plutons in the central anatolian crystalline complex turkey abstract the nw trending agacoren intrusive suite ais on the east side of the salt lake tuz golu turkey is part of a curvilinear volcanoplutonic complex along the western edge of the central anatolian crystalline complex cacc granitoids constitute the predominant lithological group within the ais and range in composition from monzonite through granite to alkali feldspar granite gabbroic rocks occur as irregular intrusive bodies with sinusoidal irregular contacts with the granitoid plutons and vary from dioritic compositions at the contacts to cumulate amphibole gabbros in their center these gabbroid to granitoid rocks are all subalkaline and display tholeiitic to calcalkaline affinities respectively modeling of the major element and trace element chemistry of the granitoids to gabbroids together with their field relations suggest that these rocks formed synchronously from a melt source that involved both mantle and crustal components mafic magmas were likely derived from a metasomatized u

tectonic controls on metamorphism partial melting and intrusion timing and duration of regional metamorphism and magmatism in the nigde massif turkey protracted heating and melting of orogenic middle crust followed by emplacement of a syn extensional pluton during decompression and cooling are demonstrated for a metamorphic core complex in central turkey new geochronologic data for the nigde massif of the central anatolian crystalline complex document an interval of melting crystallization and pb loss at elevated ambient temperature 85 92 ma determined by u pb shrimp within a single sample of peraluminous granite crustal melting was syn to post peak metamorphism 725 c dated at 91 0 2 0 ma by shrimp analysis of zircon rims in sillimanite schist that is part of the country rock to the pluton metamorphic monazite in sillimanite schist yields a younger age of 84 7 0 7 ma for matrix grains and inclusions in garnet hornblende 40ar 39ar ages from amphibolites interlayered with the sillimanite schists coincide with the timing of emplacement of magma into metamorphic country rock that had experienced cooling and decompression to 12 km and 550 c the similarity of 40ar 39ar ages for biotite in the pluton 79 ma and hornblende 79 81 ma biotite 74 76 ma and muscovite 78 83 ma in the metamorphic country rock document rapid cooling 100 c my following intrusion the coincidence of the youngest u pb magmatic zircon ages and the oldest 40ar 39ar ages combined with structural evidence for normal sense shearing and tectonic unroofing in the late cretaceous suggests that intrusion was driven by extension we propose that crustal melting occurred in the middle crust during prograde metamorphism and or initial decompression and that ascent and emplacement of magma as a pluton were only triggered once extension occurred and removed upper crustal rocks

on the role of isostasy in the evolution of normal fault systems the footwalls of west dipping normal faults that separate the west central colorado plateau from the basin and range province record at least 5 7 km and perhaps as much as 15 20 km of west side up neogene uplift with an axis just 10 20 km west of undeformed plateau strata the uplift is expressed as folding and steep faulting in pre tertiary cratonic and disconformably overlying neogene strata forming a basement cored anticline and coincident topographic high on the western margin of the plateau the authors interpret the uplift as a nonelastic response of the crust to buoyancy forces accompanying the tectonic denudation of the plateau margin profound isostatically driven deformation of the footwalls of major normal faults may be common in extensional terrains calling into question several assumptions fundamental to existing models of the evolution of normal fault systems

bivergent extension in orogenic belts the menderes massif southwestern turkey the central menderes massif is characterized by an overall dome shaped foliation pattern and a north northeast trending stretching lineation the asymmetry of shear bands and quartz c axis fabrics on either side of the structural dome demonstrate a top to thenorth northeastshearsenseinthenorthernpartandatoptothesouth southwestshear sense in the southern part of the submassif i e a bivergent downdip movement this suggests a symmetric collapse of the alpine menderes orogenic belt along two extensional shearzones conjugateshearbandsandsymmetricquartzc axisfabricsintheeast trendingtransitionzonedemonstrateacoaxialdeformationbetweenthetwoextensiondomains bivergent extension in the menderes massif is in contrast to asymmetric extension in the aegeansea here thestill activehellenicsubductionzoneevolvedfromanadvancingplate boundary associated with crustal thickening into a retreating plate boundary in oligocene miocene time southward rollback of the subducting plate during continuous northward subduction allowed asymmetric top to the north northeast extension in the back arc region during the exhumation of the cycladic core complexes in western turkey the arrival of the thick continental crust of the menderes massif halted subduction and probably caused the symmetric collapse of the massif because the high potential energy of the thickened crust was no longer supported by subduction

core complex development in central anatolia turkey tectonic models for the central anatolian segment of the alpine himalayan orogen have not considered this region as part of the aegean extensional province we have found evidence however for oligocene miocene extension and exhumation of midcrustal rocks in a metamorphic dome nigde massif that is structurally and petrologically similar to miocene core complexes 500 km to the west strong correspondence in the timing and kinematic development of the menderes western turkey and nigde core complexes suggests that extensional tectonics and exhumation of mid to lower crustal rocks affected much of the eastern mediterranean region in the nigde massif supracrustal rocks were buried to depths of 16 20 km at high temperatures 700 c during contraction associated with closure of neo tethyan seaways in late mesozoic early cenozoic time following cooling and decompression to 600 c and 10 km metasedimentary rocks underwent a second heating event at low pressures during miocene magmatism that postdated much of the unroofing of the massif development of the nigde core complex was related to exhumation of thickened and thermally weakened continental crust in the upper plate of a north dipping subduction zone the partial subduction of the tauride carbonate platform in the eocene resulted in choking of the subduction zone followed by isostatic rebound and exhumation of the buoyant platform this in turn caused a rapid emergence of the upper plate resulting in erosion of upper crustal rocks and exhumation of midcrustal rocks along the northern edge of the inner tauride suture zone although northern regions of central anatolia contain the same protoliths as the nigde massif and underwent extensive tertiary magmatism they did not undergo similar extension suggesting that core complex development in south central turkey was controlled by the location of thickened and thermally weakened crust adjacent to a suture zone

s c mylonites two types of foliations are commonly developed in mylonites and mylonitic rocks a s surfaces related to the accumulation of finite strain and b c surfaces related to displacement discontinuities or zones of relatively high shear strain there are two types of s c mylonites type i s c mylonites described by berthe et al typically occur in deformed granitoids they involve narrow zones of intense shear strain which cut across mylonitic foliation type ii s c mylonites described here have widespread occurrence in quartz mica rocks involved in zones of intense non coaxial laminar flow the c surfaces are defined by trails of mica fish formed as the result of microscopic displacement discontinuities or zones of very high shear strain the s surfaces are defined by oblique foliations in the adjacent quartz aggregates formed as the result of dynamic recrystallization which periodically resets the finite strain clock these oblique foliations are characterized by grain elongations alignments of segments of the grain boundary enveloping surfaces and by trails of grains with similar c axis orientations examples of this aspect of foliation development in mylonitic rocks are so widespread that we suggest the creation of a broad class of s c tectonites and a deviation from the general tradition of purely geometric analysis of foliation and time relationships kinematic indicators such as those discussed here allow the recognition of kilometre scale zones of intense non coaxial laminar flow in crustal rocks and unambiguous determination of the sense of shear

the late oligocene cevizlidere cu au mo deposit tunceli province eastern turkey the cevizlidere deposit located in the tunceli province of eastern anatolia is the largest porphyry cu au mo system in turkey the deposit is spatially related to a composite stock which was emplaced into paleozoic limestones and paleogene andesitic rocks to the southeast of the munzur mountains near the southwestern margin of the ovacik pull apart basin the host plutonic rocks at cevizlidere are porphyritic medium k calc alkaline diorites and granodiorites 40ar 39ar incremental step heating analysis of two igneous biotite separates obtained from syn mineral diorite porphyry yielded late oligocene cooling ages of 25 49 0 10 and 25 10 0 14 ma whereas hydrothermal biotite yielded an age of 24 73 0 08 ma re os ages obtained from two molybdenite separates 24 90 0 10 and 24 78 0 10 ma indicate that porphyry style alteration and mineralization developed shortly after magma emplacement the whole rock geochemical composition of the cevizlidere porphyry intrusions is consistent with derivation from partial melting of the metasomatized supra subduction zone mantle however based on regional tectonic reconstructions oligocene magmatic activity in this area appears to be related to a major kinematic reorganization that took place at around 25 ma during the switch from subduction to collisional tectonics in eastern anatolia this kinematic switch may be attributed to break off of the southern neo tethys oceanic slab prior to the arabia eurasia continent continent collision 12 10 ma following widespread middle eocene 50 43 ma arc back arc magmatism in this respect the subduction related tectonic setting of the late oligocene cevizlidere porphyry deposit is similar to that of the middle eocene copler epithermal au deposit the late timing of cevizlidere with respect to the southern neo tethys subduction may be comparable to some early to late miocene porphyry epithermal systems that lie within the contiguous urumieh dokhtar belt in central iran the later timing in iran reflects the diachronous nature of the eurasia afro arabia collision

tectonic burial and exhumation cycles tracked by muscovite and k feldspar 40ar 39ar thermochronology in a strike slip fault zone central turkey abstract muscovite and k feldspar 40ar 39ar ages from the eastern margin of the nigde massif in central anatolia track the timing of initial exhumation reburial and final exhumation and cooling of metamorphic rocks deformed within a strike slip fault zone although the ages of initial and final cooling were known from previous studies our new results document the timing of the reheating reburial event muscovite from four of eight gneiss samples have late cretaceous 40ar 39ar ages that date initial cooling at 75 ma the remaining samples have perturbed spectra that climb to late cretaceous ages with increasing extraction temperatures during analysis these perturbed samples are located beneath a faulted unconformity overlain by paleogene sedimentary deposits that were derived in part from the metamorphic rocks then buried metamorphosed and deformed under greenschist facies conditions samples close to the faulted unconformity are more perturbed than structurally deeper samples the age of the thermal perturbation is determined at 30 5 ma using multi diffusion domain modeling of k feldspar 40ar 39ar data from two gneiss samples one located close to the unconformity and one at a structurally deeper level muscovite 40ar 39ar results and modeled k feldspar temperature time histories show that the eastern margin of the nigde massif experienced a reheating event that peaked at 30 ma the thermal pulse has been attributed to reburial associated with transpression in the ecemis segment of the central anatolian fault zone along the eastern margin of the nigde massif activity of this fault zone may represent a far field expression of the onset of collision of arabia with eurasia in se anatolia

variations in strength and slip rate along the san andreas fault system convergence across the san andreas fault saf system is partitioned between strike slip motion on the vertical saf and oblique slip motion on parallel dip slip faults as illustrated by the recent magnitude m s 6 0 palm springs m s 6 7 coalinga and m s 7 1 loma prieta earthquakes if the partitioning of slip minimizes the work done against friction the direction of slip during these recent earthquakes depends primarily on fault dip and indicates that the normal stress coefficient and frictional coefficient vary among the faults additionally accounting for the active dip slip faults reduces estimates of fault slip rates along the vertical trace of the saf by about 50 percent in the loma prieta and 100 percent in the north palm springs segments

crustal homogenization revealed by u pb zircon ages and hf isotope evidence from the late cretaceous granitoids of the agacoren intrusive suite central anatolia turkey geochemical and isotopic evidence from the agacoren igneous association in central anatolia turkey indicates that this suite of calc alkaline granitic rocks have undergone crustal homogenization during regional metamorphic and related magmatic events whole rock chemical and sr nd isotopic data of the granitoids reveal crustal affinity with an earlier subduction component zircons show inherited cores and subsequent magmatic overgrowths the laser ablation icp ms 206pb 238u zircon ages are determined as 84 1 1 0 ma for the biotite muscovite granite 82 3 0 8 1 1 ma for the hornblende biotite granite 79 1 2 1 1 5 ma for the granite porphyry dyke 75 0 1 0 1 0 ma for the alkali feldspar dyke and 73 6 0 4 ma for the monzonite this is interpreted as continuous magma generation possibly from heterogeneous sources from ca 84 to 74 ma during the closure of the northern branch of the neotethyan ocean the oldest granitoids 84 82 ma were probably formed due to crustal thickening after obduction of the morb type oceanic crust onto the tauride anatolide microplate the younger granitoids are interpreted to be related to the subsequent post collisional extension after lithospheric delamination combination of the laser ablation icp ms zircon lu hf isotope data with the u pb ages of inherited cores suggests that cretaceous granitoids formed by melting of heterogeneous crustal protoliths which results in significant variation in ehf t data from 12 9 to 2 2 these protoliths were probably composed of reworked early proterozoic crust minor juvenile late proterozoic magmatic components and paleozoic to pre late cretaceous recycled crustal material moreover the late cretaceous zircon domains of the different granitoids are characterized by a crustal signature with a relatively restricted zircon ehf t data ranging from 4 1 to 8 8 this variation is only about twice the reproducibility ca 1 ehf of the data but much smaller than the isotope variability of inherited zircons our preferred interpretation is effective isotopic homogenization of the heterogeneous central anatolian crust during the late cretaceous high grade metamorphic and magmatic events a process that we propose to be relevant for other active continental margins

zircon u pb ages and hf o isotopic composition of migmatites from the zanjan takab complex nw iran constraints on partial melting of metasediments abstract we study migmatites and other metamorphic rocks in the zanjan takab region of nw iran and use these results to report the first evidence of oligocene core complex formation in iran four samples of migmatites associated with paragneisses including leucosomes and associated para amphibolite melanosomes were selected for u pb dating and hf o isotopic analysis zircon cores interpreted as originally detrital zircons have variable ages that peak at ca 100 110 ma but their sedimentation age indicated by the youngest 206 pb 238 u ages is ca 35 40 ma new zircons associated with incipient melting occur as overgrowths around zircon cores and or as newly grown grains morphologies and internal structures suggest that rim growth and formation of new zircons were associated with partial melting all four samples contain zircons with rims that yield 206 pb 238 u ages of 28 25 ma indicating that partial melting occurred in late oligocene time 18 o values for zircon rims vary between 8 2 and 12 3 significantly higher than expected for mantle inputs 18 o 6 and consistent with equilibrium with surface materials zircon rims yield ehf t between 2 2 and 12 4 and two stage hf model ages of 448 562 ma indicating that the region is underlain by cadomian caledonian crust according to the hf o isotopic values the main mechanism forming zircon rims was dissolution of pre existing detrital zircons with reprecipitation of new zircon shortly thereafter oligocene ages indicate that partial melting accompanied core complex formation in the zanjan takab region extension melting and core complex formation in south central iran are eocene in age but younger ages of oligocene miocene in nw iran and turkey indicate that extension was distributed throughout the region during cenozoic time

timing of cenozoic extensional tectonics in west turkey the timing of the transition from compressional to extensional tectonics in the late cenozoic evolution of west turkey has been constrained by k ar geochronology from acidic volcanic rocks and tourmaline leucogranite dykes in the central and east margin respectively of the gordes basin dacites and rhyolites in the centre of the gordes neogene sedimentary basin cut both the basement ophiolites of the izmir ankara suture zone and the neogene sediments on the basin s eastern margin the leucogranites cut metamorphic basement along a major ne sw trending normal fault that controls the regional structure of the basin pebbles of these leucogranites occur in adjacent neogene turfites and conglomerates k ar dates on biotites from the central volcanic rocks vary from 18 4 0 8 ma to 16 3 0 5 ma early miocene whilst muscovite from a leucogranite on the eastern margin of the basin provides ages of 24 2 0 8 ma and 21 1 1 1 ma latest oligocene to early miocene geochronological data and field relationships demonstrate that the earlier compressional regime had been replaced by extensional tectonics by latest oligocene early miocene

synextensional granitoids and detachment systems within cycladic metamorphic core complexes aegean sea greece toward a regional tectonomagmatic model within deforming continental regions where metamorphic core complexes mccs and synextensional granitoids are closely associated deciphering the link between detachment faulting and magmatism often remains complex as 1 the rheological weakness of magma may stimulate mechanisms of strain localization and conversely 2 tectonic processes may open close drains where magmas can intrude here we tackle this issue by focusing on the cyclades with the comparison of five granitoid cored mccs tinos mykonos ikaria naxos and serifos and their flanking detachment systems in this region granitoids were emplaced into the middle upper crust over a relatively short time period 15 9 ma while metamorphic domes were largely exhumed after more than 10 myr of extension none of those intrusions thereby proves to be a real candidate for the genesis of mccs but would rather be a consequence of a warmer regime during lithospheric thinning however all collected structural and kinematic data converge toward a regional scheme in which magmatic activity played a more pivotal role than previously postulated indeed late evolution stages of mccs were dynamically impacted by intrusions along which local and transient heterogeneities of the mechanical strength occurred interfering with the sequential development of detachments during their tectonically controlled emplacement magmatic products intruded already formed detachments at depth locally inhibiting their activity associated with a contemporaneous upward migration of extensional deformation that tended to localize through time within intrusion roofs along rheological discontinuities the newly formed detachments are expressed within granitoids through a continuum of deformation from comagmatic to ductile conditions followed by cataclasis along detachments

metamorphism of the central anatolian crystalline complex turkey influence of orogen normal collision vs wrench dominated tectonics on p t t paths the central anatolian crystalline complex cacc is a microcontinent in the alpine himalayan belt it has previously been considered as a coherent structural entity but although the entire cacc is comprised of similar rocks primarily metasedimentary rocks and granitoids it consists of at least four tectonic blocks characterized by different p t t paths these blocks are the kirsehir north west akdag north east nigde south and aksaray west massifs the northern massifs experienced thrusting and folding during collision and were slowly exhumed by erosion metamorphic rocks are characterized by clockwise p t paths at moderate p t and local low p high t lp ht overprinting in the highest grade rocks apatite fission track ages are eocene to oligocene 47 32 ma the aksaray block represents the hot shallow mid crust of a late cretaceous early tertiary arc it is dominated by intrusions rare metapelitic rocks record low p 4 kbar regional metamorphism overprinted by lp ht contact metamorphism apatite fission track ages are 50 45 ma the nigde massif is different from the other cacc blocks because it evolved as a core complex in a wrench dominated setting it is characterized by clockwise p t paths at moderate p t followed by widespread lp ht metamorphism apatite fission track ages are miocene 12 9 ma significantly younger than those in the northern massifs nigde rocks resided in the mid crust at a time when the rest of the cacc was at or near the earth s surface variations in p t t and tectonic histories especially timing of exhumation between the northern and southern cacc reflect the difference between head on collision vs mid crustal wrenching

late cenozoic tectono sedimentary evolution of the ulukisla basin progressive basin development in south central turkey the ulukisla basin is one of the most important late cretaceous cenozoic basins in central anatolia the basin is surrounded by the bolkar mountains of tauride platform in the south the nigde massif of central anatolian crystalline complex to the north and the ecemis fault zone and aladag mountains in the east the fact that time interval proposed for the formation of ulukisla basin is quite wide and more than one tectonic regime prevailed in the region have led to various suggestions concerning the evolution of the basin while the suggestions majorly examine the character of the basin during the late cretaceous early cenozoic the number of detailed studies on the status of the basin in the late cenozoic is limited in this study we focused on the less studied late cenozoic evolution to differentiate the tectonic phases that controlled the development of ulukisla basin through structural data and elaborate the responses of sedimentation and paleogeography during this period through detailed facies analyses our findings indicate that the ulukisla basin which started to develop as a supradetachment basin in the late cretaceous has continued its extensional development progressively during its cenozoic history while the relatively well studied early cenozoic sequences represent a marine environment that was rapidly changed shallow to deep sea environment and then gained a shallow character by the middle eocene sedimentary features and fossil contents of the late cenozoic units characterize deposition started in a paralic environment changing into a terrestrial environment rapidly as a result of isolation by the uplifting of surrounding topographies while the basin continues its development under an extensional tectonic regime however the extensional basin history surceased in post middle eocene and post middle miocene probably caused by the closing processes of the different branches of neotethys ocean

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

gneiss domes metamorphic core complexes and wrench zones thermal and structural evolution of the nigde massif central anatolia 1 the nigde massif a migmatite cored structural dome in south central turkey was metamorphosed deformed intruded and exhumed in an oblique tectonic regime involving a switch from transpression prograde metamorphism to transtension exhumation an 80 ma history of transpression and transtension is recorded in metamorphic rocks of the massif and the last 50 ma are recorded in both basement and overlying basin deposits nigde metamorphic rocks record a high temperature top to north syntranspression ductile fabric that was overprinted by lower grade top to south syntranstension ductile shear zones the 40ar 39ar data for hornblende muscovite and biotite document rapid late cretaceous cooling with the oldest ar hornblende ages 88 79 ma overlapping u pb ages in monazite and zircon 92 78 ma muscovite ar ages are dominantly 81 79 ma suggesting a short time between crystallization of high temperature metamorphic rocks and their cooling biotite ar ages are 79 74 ma with the exception of disturbed samples from the eastern margin of the massif and from eocene granitic stocks in the dome core the eastern margin adjacent to the sinistral central anatolian fault zone records another cycle of burial and exhumation that overprinted earlier fabrics and disturbed isotopic systems these two cycles of burial exhumation took place repeatedly along the same zone this may be characteristic of highly oblique tectonic regimes in the nigde massif burial and exhumation became more localized and of lower amplitude over time suggesting stabilization of the crust

diapiric exhumation of earth s youngest uhp eclogites in the gneiss domes of the d entrecasteaux islands papua new guinea abstract the woodlark rift in papua new guinea hosts the world s youngest 2 8 ma eclogite facies rocks and extensional deformation has played a key role in exhuming these u hp rocks at rates of 20 mm yr during the eocene papuan arc continent collision australian plate derived continental rocks were subducted to u hp depths there they remained for up to 30 m y until the pliocene when asthenospheric circulation ahead of the west propagating woodlark spreading ridge introduced heat and fluids this caused rocks to break away from the paleosubduction channel recrystallize in the eclogite facies and rise as rayleigh taylor instabilities the diapirs ascended adiabatically undergoing partial melting which lowered their viscosity and increased buoyancy u hp crust ponded near the moho at 2 4 ma thickening the crust to 40 km 11 kb domal uplifts emerged above sea level and these are still underlain by an unusually thick crust 26 km for a rift that has stretched by factor of 3 since 6 ma after ponding they acquired a flat lying foliation during amphibolite facies retrogression vertical shortening accompanied the gravitationally driven outflow of ponded lower crust the weak material was extended parallel to the rift margin thinning ductilely by w k 0 2 and was mechanically decoupled from and orthogonal to plate motion in the rift top e shear fabrics suggest that this flow was westward perhaps driven by isostatic stresses towards a strongly thinned rift corridor ahead of the woodlark spreading ridge at 100 c per m y and were mechanically incorporated into the rift s upper crust final exposure was by normal faulting and minor erosion such exhumation may also apply to other u hp terranes where less evidence for moho ponding is preserved

coeval extension and compression in late mesozoic recent thin skinned extensional tectonics in central anatolia turkey abstract the central anatolian crust is composed of high grade metamorphic rocks covered by tertiary shallow marine to continental sedimentary rocks with a middle miocene recent volcanic activity in cappadocia after the late cretaceous closure of the tethyan ocean and following plate collision core complexes formed in nigde and kirsehir regions of central anatolia recent geophysical studies indicate the presence of low seismic velocity zones beneath central anatolia interpreted as regionally thinned and or hot mantle lithosphere or asthenospheric upwelling we present new structural data covering a 300 km wsw nne trending transect between konya and yozgat cities to suggest that central anatolian cenozoic tectonic regime is extensional and the narrow fold thrust zones once taken as evidence of crustal convergence resulted from gravitational movements curie point depths map of central anatolia shows a large scale diameter 140 km upwarping c 15 km of the regional crust we interpret as due to asthenospheric upwelling these considerations suggest that 1 the central anatolian crust deforms by extension transcurrent faults like the central anatolian fault zone accommodate the crustal stretching by transfer faulting 2 post late cretaceous crustal extension favored the placement of hot and low density asthenospheric material in cappadocia by processes that may be explained by rayleigh taylor instability phenomenon 3 in central anatolia large post eocene horizontal crustal displacements we estimate a minimum of 50 km are not achieved by crustal contraction as previously proposed but thin skin extensional tectonics and 4 tethyan suture lines need to be reviewed since their traces may be modified by later extensional displacements

the ductile shear zone in granitoid of the central anatolian crystalline complex turkey implications for the origins of the tuzgolu basin during the late cretaceous extensional deformation abstract the emizozu shear zone is the west northwest trending ductile shear zone within the agacoren granitoid in central turkey deformation that affected the granitoid along the emizozu shear zone resulted in mylonites with mylonitic foliation and stretching lineation the textural features of the deformed minerals suggest that mylonitization occurred under conditions of upper greenschist facies the shear indicators including asymmetric porphyroclasts oblique foliation and shear bands suggest a down dip top to the southwest displacement the orientation of stretching lineation as well as kinematic indicators indicates the extensional character of the emizozu shear zone although it is not precisely dated the available age constraints suggest that the zone formed at 78 71 ma according to field and micro structural data the agacoren granitoid was most likely emplaced during a regional deformation in central turkey and synchronously or shortly after was overprinted by the extensional emizozu shear zone the zone can also be correlated with the earlier stage development of the tuzgolu basin in central turkey

non marine sedimentation associated with oligocene recent exhumation and uplift of the central taurus mountains s turkey abstract three related basins in southern turkey the ecemis basin the karsanti basin and the aktoprak basin document the neogene recent regional exhumation and surface uplift history of the central taurus mountains the regional tectonic framework was established by a late eocene phase of compressional deformation that ended tethys related marine deposition during the oligocene early miocene non marine sedimentation was dominantly from braided rivers flowing from the nascent taurus mountains and from the nigde metamorphic massif further north during this period erosion more or less kept pace with exhumation and the topography remained subdued allowing a marine incursion probably eustatically controlled into the karsanti basin in the east during early oligocene time regional exhumation was possibly controlled by thermal uplift of an actively extending area located behind the subducting s neotethys in the eastern mediterranean sea during exhumation largely ophiolitic rocks were eroded revealing the deformed mesozoic tauride carbonate platform beneath the area was affected by a short lived pulse of compressional deformation transpression probably in mid miocene time but extensional exhumation then resumed as indicated by the presence of metamorphic derived clasts from the adjacent nigde massif late miocene deposition was dominated by large inward draining lakes consistent with regional evidence of a humid climate during this time strong surface uplift took place during plio quaternary time drainage to the mediterranean became established allowing river valleys to incise deeply into the flanks of the taurus mountains palaeo valleys were successively infilled with coarse alluvial sediments this deposition was influenced by ne sw trending extensional faults in addition the sedimentary evolution of the area was strongly influenced by the nne ssw trending ecemis fault zone which has experienced ca 60 km of left lateral strike slip since the late eocene an important pulse of normal faulting transtension in latest miocene early pliocene time generated large fault scarps these acted as sources for large plio quaternary alluvial fans which prograded across active strike slip faults the morphology of these fans was influenced by a combination of quaternary climatic change axial fluvial downcutting and active strike slip tectonics in general the plio quaternary regional uplift of the taurus mountains may relate to underplating of material derived from the african plate during progressive collision with the anatolian eurasian plate in the vicinity of the easternmost mediterranean sea

late cenozoic tectonics and volcanism along the north anatolian fault new structural and geochemical data abstract different types of volcanic activity have developed along the north anatolian fault zone naf in turkey detailed analysis of satellite images and digital elevation models dems and field observations have been made in order to understand the tectonics and the distribution of volcanic vents in the anatolian block some faults are oblique to the naf and delimit extensional escape wedges vents rooted on open tension fractures show that emplacement of the volcanism is related to tensional fracturing of the anatolian continental block which we attribute to the onset of free borders in the south and west along the naf earliest extension 1 is directed s to ssw and the latest 2 towards w to wsw parallel to the sinistral slip along the naf major and trace element geochemical data indicate that the dominant calc alkaline rocks are associated with various alkaline lavas k ar ages of the volcanics range from 22 to 8 5 ma in galatia massif 900 to 100 ka in niksar and 3 to 12 ka in erzincan isotopic and trace element data are interpreted as reflecting a dominantly lithospheric mantle source slightly mixed with asthenospheric liquids most magmas were fractionated and contaminated by continental crust during their ascent 1 and 2 tectono volcanic events have propagated through time and space from west to east the 1 extension is late oligocene in the galatia massif late miocene in niksar and late pliocene in erzincan the 2 extension and strike slip event along the naf began in the late miocene in the galatia massif early pliocene in niksar and quaternary in erzincan signature from an asthenospheric source in the second event in the three regions suggests that an ancient suture zone galatia massif and or the lithospheric naf transform niksar and erzincan have served to channel small quantities of asthenospheric melts existing at the base of the lithosphere

timing of post obduction granitoids from intrusion through cooling to exhumation in central anatolia turkey abstract the middle to late cretaceous central anatolian granitoids intrude the supra subduction zone type central anatolian ophiolite and medium to high grade metasediments of central anatolian crystalline complex and are overlain by late palaeocene to early middle eocene sediments their single zircon 207 pb 206 pb evaporation ages define three clusters 1 cenomanian turonian weighted mean age 94 9 3 4 ma 2 turonian santonian 85 5 5 5 ma and 3 campanian 74 9 3 8 ma their hornblende and biotite 40 ar 39 ar and k ar cooling ages cluster around 80 65 ma the close hornblende and biotite ages reflect rapid exhumation of a mid crustal section during the campanian maastrichtian early to middle palaeocene 57 62 ma apatite fission track age clusters date the tail end of this exhumation episode it is proposed that the central anatolian granitoid melts were generated in a post collisional extensional setting following the docking of an oceanic island arc onto the tauride anatolide platform campanian maastrichtian to early middle palaeocene rapid exhumation event is considered to result from continent continent collisions between eurasian plate and the tauride anatolide platform along the izmir ankara erzincan suture zone

geomagnetic field behavior during the iceland basin and laschamp geomagnetic excursions a simple transitional field geometry we present four new records of the iceland basin excursion ibe and five new records of the laschamp excursion le obtained from rapidly deposited marine sediments in the north atlantic ocean the nordic seas the gulf of mexico the south china sea and the southern indian ocean marked minima in relative paleointensity correspond with the paleomagnetic directional changes associated with all of the excursion records the virtual geomagnetic pole vgp paths of the four ibe records are all similar the vgps move southward over europe and africa reaching the southern hemisphere three reach antarctica and then move to more eastern longitudes before returning northward over australia and east asia describing a large counterclockwise loop the same vgp pattern is observed in other published records the vgp paths observed for the le are similar to those of the ibe however they loop clockwise instead of counterclockwise despite the different sense of looping the marked similarity among the paths for the two excursions suggests that a similar relatively simple geometry dominated the transitional field during both the ibe and the le similar dynamo mechanisms must therefore have been active in the earth s core for both excursions the duration of the excursions is estimated at 2 000 years which supports the suggestion that a difference exists between the mechanisms for excursions and reversals however the coincidence of the longitudinal bands for vgps associated with excursions compared to some reversal paths could also indicate an inherent link between the mechanisms for reversals and excursions

the origin and evolution of the menderes massif w turkey a rubidium strontium and oxygen isotope study the menderes massif located in the alpine orogen of western turkey has three litho structural units a basal gneiss core a schist mantle covering the gneiss core and an overlying marble mantle this study reports isotopic data from samples of metasediments and migmatites from the southern type a and of tonalitic to granitic metaigneous rocks from the northern menderes massif type b type a rocks define a rb sr whole rock isochron age of 502 10 ma and an initial87sr 86sr ratio of 0 71174 73 this is interpreted as the age of migmatization type b rocks give a rb sr whole rock isochron age of 471 9 ma with an initial87sr 86sr ratio of 0 70684 25 which we interpret as the intrusion age k white micas from rock type a give an average rb sr mineral age of 56 1 ma which can be interpreted as the formation age of the alpine mineral paragenesis k white micas from rock type b give rb sr mixed ages of 120 230 ma between alpine and pan african orogenies biotites from both rock types yield an average rb sr age of 37 1 ma which is interpreted as an alpine cooling age the oxygen isotope ratios of type a rocks range from 10 4 to 14 6 and of type b from 8 9 to 11 8 the oxygen and strontium isotopic compositions together clearly distinguish rocks of types a and b compositions of type a rocks suggest a crustal origin type b rocks have compositions transitional between those of crustal and mantle derived materials

geometry and kinematics of continental basement deformation during the alpine orogeny mt olympos region greece abstract in the hellenic alps continental crust of the leading edge of the apulian plate was subducted beneath the european plate during late cretaceous early tertiary closure of tethyan ocean basin s carbonate rocks of the external hellenides are exposed in the mt olympos tectonic window overthrust by several thin 0 2 4 km thick thrust sheets of granitic basement derived from the internal hellenides field mapping and structural data from the mt olympos region reported here establish the geometry kinematics and strain history of the continental basement before during and after continental collision and subduction seven deformational events document the change from ductile conditions obtained at depth in the early stages of deformation to lower temperature ductile and semi ductile shortening related fabrics to brittle extensional features related to exhumation of the metamorphic rocks d 1 d 4 occurred during subduction of basement nappes and are marked by thrust faulting and folding under blueschist facies conditions d 5 d 7 are related to unroofing of blueschist facies metamorphic rocks and are associated with extension each of the major shortening phases d 1 d 3 verges toward the foreland southwest oppositely directed d 5 d 7 extension occurred behind the active thrust belt during continued regional shortening normal faults have strongly modified the original thrust related geometry in the mt olympos region and elsewhere in the internal hellenides

the aegean sea we summarize briefly the main features of a kinematic model of evolution of the aegean area since 13 ma the formation of the aegean sea by extensional tectonics is related to the subduction of the mediterranean floor below the hellenic arc we then make a quantitative estimate of vertical movements in the aegean area on the basis of geological data and demonstrate that the outer arc was built since the beginning of this episode of subduction by vertical uplift the easiest way to explain the uplift is by underplating finally we discuss briefly the dynamics of the subduction marginal sea formation processes in this continental collision framework

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

39ar 40ar ages from the yozgat batholith preliminary data on the timing of late cretaceous extension in the central anatolian crystalline complex turkey abstract isotopic dating of sheared and unsheared rocks can be important in understanding deformational processes in orogenic belts this study examines 40ar 39ar dating of granitoids and mylonitic rocks to constrain intrusive and deformational events within the northern part of the central anatolian crystalline complex cacc the kerkenez granitoid within this complex comprising primarily quartz monzonite and hornblende granite contains discrete ductile shear zones these zones are characterized by protomylonite and mylonite formations with metamorphism conditions that reach lower amphibolite facies mylonitic foliations and lineations and asymmetric kinematic indicators e g asymmetric porphyroclasts composite shear bands with top to the northwest shear senses considering the high closure temperatures 500 c for hornblende and 350 c for k feldspar both hornblende quartz monzonite and hornblende granite in the kerkenez granitoid may have cooled rapidly suggesting that hornblende quartz monz

late miocene ductile extension and detachment faulting mykonos greece the geometry and style of structural relations at map to microscopic scale on mykonos cyclades aegean sea greece suggests ductile extension and detachment faulting during the late miocene this island is dominated by granitic rocks that have a well developed shallowly dipping mylonitic foliation and a northeast southwest trending mineral elongation lineation kinematic indicators in these rocks exhibit a top to the northeast down dip sense of shear textural relations suggest that conditions during mylonitic deformation were greenschist to amphibolite facies and published k ar geochronology suggests a late miocene age for this deformation event mylonitic rocks lie in the footwall of a low angle fault and fault striae parallel to the elongation lineation suggest kinematic coordination between mylonitic deformation and movement along the fault translation along the fault juxtaposes younger tilted sedimentary rocks of low metamorphic grade upon the once deeper mylonitic rocks the style and geometry of deformational fabrics and map relations on this island are strikingly similar to those observed in metamorphic core complexes of the western united states

coeval extensional shearing and lateral underflow during late cretaceous core complex development in the nigde massif central anatolia turkey 1 the nigde massif at the southern tip of the central anatolian crystalline complex consists of two structural units foliations in the lower unit define a dome cored by migmatites the contact between the two units bears all the elements of a ductile to brittle extensional detachment hence the nigde massif represents an extensional metamorphic core complex top to ne ene shearing at higher levels of the lower unit relates to displacement along the detachment deeper levels of the lower unit display high temperature top to ssw ductile shearing the two shearing deformations show a difference in the mean trend of stretching lineations of up to 58 new 40ar 39ar ages combined with previously published data enable us to infer that the two shears were contemporaneous in our favored interpretation oblique shearing in the core of the dome reflects lateral underflow i e horizontal flowing of the lower crust in a direction highly oblique to the direction of extension as a result of the interaction between lateral underflow and downdip shearing along the overlying detachment distinct structural domains are expected to exist within the migmatitic part of the core complex with observed counterparts in the nigde dome lateral underflow may reflect inward flow on the scale of the core complex regional scale channel flow is an alternative that would better account for the record of non coaxial deformation in the core of the dome more generally we suspect that the development of lateral underflow in a metamorphic core complex more likely reflects regional channel flow rather than local inward flow

mio pliocene basin development in the eastern part of the cappadocian volcanic province central anatolia turkey and its implications for regional tectonics the cappadocian volcanic province cvp comprises predominantly of a thick succession of volcanogenic rocks and interbedded siliciclastic sediments of middle miocene to recent age in central anatolia turkey the conditions of basin development in the eastern part of the cvp have been elucidated by using sedimentological and geomorphological approaches the prevailing tectonic regime its extent and causes are also discussed sedimentological analysis supported by geomorphological observations revealed a major ne trending probably normal border fault and its several synthetics this tectonic element constitutes the se margin of the basin and divided the cvp from the tauride range during middle miocene to pliocene the basin fill in the study area comprises gravelly alluvial fans near the border fault while fluvial clastics and lacustrine carbonates dominate towards the centre some pyroclastic rocks and lava flows are also made part of the fill the southeastern basin margin is characterized morphologically by a number of uplifted basement blocks probably associated with synthetic faults and some deeply incised canyons in the footwall these canyons were subsequently filled with a mid pliocene ignimbrite sheet and represent the sediment supply conduits to the basin the cessation of filling in the basin was determined by strike slip faults that uplifted and detached the basin about 2 6 ma this date also marks the onset of the neotectonic period in the region the overall extensional tectonic regime inferred for the eastern cvp appears coeval with events recognised in the southern basins i e adana and mut basins and the eastern mediterranean some physical connections between these basins also have been demonstrated it is suggested that the cvp and the southern basins were all created during a phase of extension resulting from continued northward subduction of the african plate beneath the eurasia during the late cenozoic

metamorphic core complexes of cordilleran type in the cyclades aegean sea greece the islands of ios and naxos in the cycladic archipelago greece contain elongate domes over which a pervasive north to north northeast stretching lineation is warped these islands may be metamorphic core complexes of cordilleran type involving middle crustal rocks drawn upward and outward from underneath the sedimentary basins now 100 km to the south from ca 25 ma onward during uplift the crystalline rocks now exposed on the islands were deformed noncoaxially in the deeper levels of a major shallow dipping ductile shear zone this shear zone may have connected with low angle normal faults in its upper levels because it is probable that its later history involved the metamorphic complexes being dragged out from under a stretching and fracturing upper plate composed mainly of unmetamorphosed sedimentary and ophiolite suite rocks this model can be extended to explain the exhumation of the high pressure low temperature metamorphic rocks on crete which with the cyclades forms a distended paired metamorphic belt separated by an active sedimentary basin