kinematic reconstructions and magmatic evolution illuminating crustal and mantle dynamics of the eastern mediterranean region since the late cretaceous the relationship between subduction dynamics and crustal deformation in the mediterranean region has been recently studied using three dimensional 3d numerical models such models require however a detailed information concerning the past geological evolution we use stratigraphic petrologic metamorphic structural paleomagnetic and magmatic data to build new kinematic reconstructions of the eastern mediterranean region since the late cretaceous using the principle of non rigid domains the motions of the 56 deforming domains defined in this work are calculated based on published paleomagnetic rotations the directions and amounts of displacement on crustal scale shear zones and the burial and exhumation histories of the main metamorphic units extracted from these reconstructions paleotectonic maps and lithospheric scale cross sections illustrate that the present day subduction zone has been continuously retreating southward since the late cretaceous and has accreted several small continental domains in the process we find evidence for two back arc related extensional events 1 slow extension along the balkans and the pontides in the late cretaceous while the trench was long and linear and 2 faster extension in the rhodope aegean west anatolian region since the eocene oligocene rapid rotation of the hellenides between 15 and 8 ma probably indicates a slab tearing event below western anatolia that could have further accelerated this extensional kinematics spatial distribution and the geochemical signature of magmatic centers integrated in these reconstructions allow us to trace mantle related processes revealing the deep dynamics that controls both the magma genesis and the crustal deformation

40ar 39ar and oxygen isotope studies of polymetamorphism from tinos island cycladic blueschist belt greece petrological oxygen isotope and 40ar 39ar studies were used to constrain the tertiary metamorphic evolution of the lower tectonic unit of the cyclades on tinos polyphase high pressure metamorphism reached pressures in excess of 15 kbar based on measurements of the si content in potassic white mica temperatures of 450 500 c at the thermal peak of high pressure metamorphism were estimated from critical metamorphic assemblages the validity of which is confirmed by a quartz magnetite oxygen isotope temperature of 470 c some 40ar 39ar spectra of white mica give plateau ages of 44 40 ma that are considered to represent dynamic recrystallization under peak or slightly post peak high pressure metamorphic conditions early stages in the prograde high pressure evolution may be documented by older apparent ages in the high temperature steps of some spectra eclogite to epidote blueschist facies mineralogies were partially or totally replaced by retrograde greenschist facies assemblages during exhumation oxygen isotope thermometry of four quartz magnetite pairs from greenschist samples gives temperatures of 440 470 c which cannot be distinguished from those deduced for the high pressure event the exhumation and overprint is documented by decreasing ages of 32 28 ma in some greenschists and late stage blueschist rocks and ages of 30 20 ma in the lower temperature steps of the ar release patterns of blueschist micas almost flat parts of ar ar release spectra of some greenschist micas gave ages of 23 21 ma which are assumed to represent incomplete resetting caused by a renewed prograde phase of greenschist metamorphism oxygen isotope compositions of blueschist and greenschist facies minerals show no evidence for the infiltration of a 18o enriched fluid rather the compositions indicate that fluid to rock ratios were very low the isotopic compositions being primarily controlled by those of the protolith rocks we assume that the fundamental control catalysing the transformation of blueschists into greenschists and the associated resetting of their isotopic systems was the selective infiltration of metamorphic fluid a quartz magnetite sample from a contact metamorphic skarn taken near the miocene monzogranite of tinos gave an oxygen isotope temperature of 555 c and calculated water composition of 9 1 the value of 18o obtained from this water is consistent with a primary magmatic fluid but is lower than that of fluids associated with the greenschist overprint which indicates that the latter event cannot be directly related to the monozogranite intrusion

palaeomagnetic evidence for block rotations in the western greek rhodope summary the rhodope massif has been traditionally considered to be a pre mesozoic element that remained stable during the tertiary this idea has been partly supported by previous palaeomagnetic results on plutonic and volcanic rocks ranging in age from palaeocene to oligo miocene however new palaeomagnetic data from additional sites on tertiary magmatic rocks of the western greek rhodope show declination values indicating in most cases a clockwise rotation whereas inclinations are systematically lower than those corresponding to the actual latitudinal position of the rhodope our results together with previously published ones are discussed in the light of recent ideas proposed for the rhodope and the north aegean region we suggest that at least the western part of the greek rhodope has been clockwise rotated after the oligocene north south to ne sw extension tilted the formations towards the north or north east producing apparently high inclinations if the alternative pole position for eurasia proposed by westphal 1990 is adopted

palaeomagnetic and geochronological evidence for a major middle miocene unconformity in soke basin western anatolia and its tectonic implications for the aegean region cenozoic convergence between the eurasian and african plates and concurrent slab roll back processes have produced a progressive extension in back arc areas such as the aegean region and western anatolia there is still a long standing controversy as to whether this was a continuous or stepwise process to shed light on this controversy and on the driving mechanism of regional extension we present palaeomagnetic and geochronological results from the soke basin located at the southeastern rim of the izmir balikesir transfer zone our improved geochronology shows that volcanic activity in the region occurred between 11 66 and 12 85 ma middle to late miocene palaeomagnetic data for the soke basin show a c 23 clockwise rotation whereas early miocene data show a c 28 counterclockwise rotation the primary nature of the magnetization is indicated by a positive tilt test the resulting c 51 counterclockwise rotations during the middle miocene signify a major tectonic reorganization during a period when an interruption of exhumation of metamorphic massifs has been reported we suggest that the izmir balikesir transfer zone is the main driver of the reorganization in the region the regional fingerprint of this tectonic reorganization coincides with the acceleration of trench retreat and illustrates the surface impact of tearing of the hellenic slab supplementary material details of 40 ar 39 ar analysis including heating steps and the output pmag file including details of paleomagnetic analysis performed in this study are available at https doi org 10 6084 m9 figshare c 3690871

first palaeomagnetic results from the cycladic massif greece and their implications for miocene extension directions and tectonic models in the aegean abstract the aegean region is characterised by major fault bound blocks with markedly contrasting structural trends recent models account for these variations either through differential block rotation or through a process of radial extension the cycladic massif in the back arc region to the hellenic trench represents a critical area where apparently divergent extension directions are observed this contribution provides the first palaeomagnetic results from this area magnetic remanence and ams data are presented for middle miocene granodiorites on the islands of mykonos and naxos these rocks are exposed in the footwalls of major extensional detachments within the metamorphic core complexes that characterise the cycladic massif a clear correlation between the orientation of an l s fabric developed within the intrusions and the magnetic fabric data is observed demonstrating the presence of a normal magnetic fabric of extensional origin the mean extension directions inferred from the orientations of the maximum axes of the magnetic susceptibility ellipsoids are markedly divergent at 064 mykonos and 351 naxos northeasterly in situ magnetic remanences are observed on mykonos whereas those on naxos are directed to the nnw neither direction corresponds to the appropriate palaeomagnetic reference direction for the miocene standard palaeomagnetic tilt corrections cannot be applied at these sites because of the lack of palaeohorizontal markers deviations of in situ remanences away from the reference direction are potentially due to rotation around any one of an infinite number of net tectonic rotation axes each of these may be arbitrarily decomposed into components of tilting and vertical axis rotation geologically realistic solutions which restore the in situ magnetisations back to the reference direction may be found by consideration of regional structural trends assuming that tilting is controlled by the major block bounding faults these solutions indicate significant components of differential vertical axis rotations across the cyclades mykonos is bound by nw se trending regional faults and is shown to have rotated clockwise by ca 22 in contrast naxos is bound by ene wsw trending structures and has rotated anticlockwise by ca 33 the apparent divergence of extension directions inferred from both the magnetic anisotropy and structural data is resolved by correcting the mean ams data for subsequent rotation using the rotation solutions derived from the magnetic remanence data the data imply that the primary middle miocene extension direction in the cycladic massif was nearly uniform along a nne ssw azimuth we consider that the uniform extension direction and opposing senses of block rotation determined for this portion of the cycladic massif are most consistent with a recent model describing deformation within the aegean in terms of a system of broken fault bounded slats within this scenario mykonos occupies a position on a clockwise rotating slat which continues northwest at least as far as evvia a major ene wsw trending fault between the islands previously identified on shallow seismic sections separates this domain from an anticlockwise rotating slat which includes naxos

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

the north cycladic detachment system and associated mineralization mykonos greece insights on the evolution of the aegean domain 1 in the aegean back arc domain some 30 35 ma ago an increase of the rate of slab retreat led to the initiation of post orogenic extension largely accommodated by large scale structures such as the north cycladic detachment system ncds although this extension is still active nowadays an e w compressional regime developed in the late miocene with the propagation of the north anatolian fault on mykonos island cyclades the ne sw back arc extension is particularly well expressed with the livada and mykonos detachments that belong to the ncds and that are associated with nw se barite veins emplaced during the synkinematic cooling of the mykonos intrusion this study shows that the formation of the mineralization occurred when the pluton crossed the ductile to brittle transition during its exhumation below the ncds at 11 10 ma in addition the kinematics of mineralized structures evolved with time 1 most of the displacement was accommodated by the top to the ne livada and mykonos detachments accompanied by the formation of mineralized normal faults that were 2 reworked in a strike slip regime with an e w direction of shortening and a persistent ne sw stretching and 3 a late post mineralization e w compressional stage with a minor reworking of shallow dipping faults locally including the detachments themselves we interpret this increase of the e w shortening component recorded during the mineral deposition as a consequence of the initiation of the westward motion of anatolia from 10 ma thus 4 ma before the propagation of the north anatolian fault in the dardanelles strait and the localization of the strain on the aegean sea margins

constraints on the kinematics of post orogenic extension imposed by stretching lineations in the aegean region abstract new kinematic data from shear zones of tertiary age in the metamorphosed basement of the aegean region in combination with published kinematic lithological and palaeomagnetic data have enabled us to determine a detailed kinematic evolution of the region during post orogenic extension in the aegean three distinct stages are recognised firstly extension of both the western and eastern aegean started in the late oligocene early miocene 36 25 ma ago initially in an 023 direction stage two started shortly after this with the division of the aegean crust into the west aegean block a coupled assemblage of small blocks bound on its northwestern and southeastern margins by the scutari pec line and mid cycladic lineament fracture zones respectively between 25 ma and 3 ma the west aegean block underwent 30 clockwise rotation whilst the eastern aegean underwent on average 19 anticlockwise rotation rotation of the west aegean block as a semi coherent block was aided by the relative coolness of the block compared to the warmer eastern aegean region as the crust thinned and rotated the nw se trending faults which characterise the west aegean block were cross cut by e w trending faults in the latest miocene pliocene the thermal front migrated westwards into the west aegean block and the mid cycladic lineament ceased activity the final kinematic stage marked the start of the subdivision of the west aegean block into two portions in the pliocene the southeastern portion nw cycladic area coupled with the sw cycladic area to form a central aegean block that started to translate southwest the northern and western portion rotated a further 10 15 clockwise whilst the southeastern rim rotated anticlockwise these data demonstrate that aegean post orogenic extension is not dominated by a single block rotation or radial spreading event but is characterised by the sequential formation and reformation of lithospheric scale blocks that have developed in response to large scale partitioning of rotational strain

paleomagnetic evidence for rotation in opposite senses of adjacent blocks in northeastern aegea and western anatolia paleomagnetic data from western anatolia and from the island of lesbos demonstrate significant counterclockwise clockwise or null rotations of coherent blocks which occurred during the neotectonic period these results suggest that the brittle carapace of the lithosphere may not everywhere follow the motion of the ductile lower part but that its movement arises from adjustment to the extensional tectonic regime

u pb and 40ar 39ar geochronology of the symvolon granodiorite implications for the thermal and structural evolution of the rhodope metamorphic core complex northeastern greece north aegean continental lithosphere was thickened by southwest vergent thrusting and continental subduction within the alpine collisional orogen but has subsequently been greatly extended on a northeast southwest axis in the back arc of the hellenic subduction zone crosscutting relationships with two granodiorite bodies emplaced at 31 33 ma the xanthi and eastern vrondou plutons constrain a pre mid oligocene origin of alpine convergent structures in northeastern greece post alpine thinning of the north aegean nappe pile began in earliest miocene time and has been accommodated by a succession of distinct structural systems the earliest of these the symvolon shear zone appears to represent a midcrustal coaxial rupture of the falakron marble series a carbonate platform 5000 m thick that was subducted northeastward beneath high grade rocks of the rhodope metamorphic province in late alpine time zircon and titanite u pb dates and hornblende 40ar 39ar dates obtained in this study constrain the intrusion and incipient mylonitization of the symvolon or kavala granodiorite within the symvolon shear zone at 21 22 ma following its emplacement the symvolon body resided at temperatures between 300 c and 500 c for 5 7 m y during which coaxial deformation may have continued within a widening symvolon rupture the strymon valley detachment a regionally south west dipping low angle normal fault succeeded the symvolon shear zone in middle miocene time southwestward displacement of the serbo macedonian gneiss complex by as much as 80 km in the hanging wall of this detachment facilitated the unroofing of the rhodope metamorphic core complex including the falakron marble series and several tertiary plutons in its footwall biotite and k feldspar 40ar 39ar dates from 11 1 0 2 ma to 15 5 0 3 ma yielded by symvolon granodiorite samples document the cooling of the rhodope core complex below 150 c 300 c during its southwestward progressive exhumation in the footwall of the strymon valley detachment

new paleomagnetic data from oligocene formations of northern aegea new paleomagnetic data obtained from volcanic and plutonic formations in thrace northern aegea show that this region has not undergone any significant rotation since the lower oligocene the mean value of the inclination is shallower than expected on the basis of a geocentered dipole field implying a large northward drift of about 1000 km although a comparison with published data from bulgaria leads to a puzzling large shortening between these two regions the measured shallow inclinations are coherent with most of other paleomagnetic studies from oligocene formations throughout the entire mediterranean area together with published results from chalkidiki peninsula our data suggest that the circum rhodopean belt was almost rectilinear and trending e w in lower oligocene time

syn metamorphic nappe complex in the rhodope massif structure and kinematics mylonitic gneisses of the bulgarian and greek rhodope were deformed under medium pressure type metamorphism the kinematic information contained in these gneisses shows that shear deformation occurred during development of a nappe complex lithologies and metamorphic histories allow a lower footwall and an upper hanging wall terrane to be distinguished that define a crustal scale duplex as oceanic crust is involved collision between two continental units with subsequent crustal thickening is inferred the blocks would be moesia to the north and the lower rhodope promontory to the south which collided in the mesozoic to early cenozoic the nappe complex is characterized by south to southwestward foreland directed piling up and is associated with both coeval and subsequent extension the late extension is associated with the establishment of a high temperature low pressure metamorphic gradient and plutonism that predates but makes a transition to the lithospheric extension of the aegean arc

structural architecture of the rhodes basin a deep depocentre that evolved since the pliocene at the junction of hellenic and cyprus arcs eastern mediterranean abstract interpretation of 1500 km of multi channel seismic reflection profiles shows that the rhodes basin evolved in two distinct tectonic stages a protracted miocene convergence episode p1 resulted in the development of a mainly sse verging fold thrust belt this period corresponds with the emplacement of the lycian nappes to the northeast and fold thrust complexes on the island of rhodes to the west this phase of deformation ceased in the late miocene the absence of evaporites in the rhodes basin suggests that this region must have remained above the depositional base of marine evaporite environment during the messinian the morphology of the m reflector and the architecture of the lowermost pliocene growth strata in the central portion of the rhodes basin demonstrate the existence of rugged paleo relief over the pre existing miocene fold thrust belt in early pliocene the middle pliocene quaternary phase of deformation is characterised by ne sw sinistral transpression p2 and rapid regional subsidence the p2 deformation occurred in response to an actively curving hellenic arc and the increasing obliquity of its eastern limb the pliny strabo trenches or fault zones to the convergence vector of the african plate during this time the p1 structures became re activated as transpressional faults further facilitating the rapid subsidence we envisage the evolution of the rhodes basin as the result of subsidence associated with loading of the large imbricate thrust panels that carry the western tauride mountains in the north at present the pliny strabo fault zones are delineated as a ne sw trending 30 50 km wide zone that continue into the western segment of the rhodes basin this fault zone is further correlated with the similar trending 50 km wide burdur fethiye fault zone in southwestern turkey

the two stage aegean extension from localized to distributed a result of slab rollback acceleration back arc extension in the aegean which was driven by slab rollback since 45 ma is described here for the first time in two stages from middle eocene to middle miocene deformation was localized leading to i the exhumation of high pressure metamorphic rocks to crustal depths ii the exhumation of high temperature metamorphic rocks in core complexes and iii the deposition of sedimentary basins since middle miocene extension distributed over the whole aegean domain controlled the deposition of onshore and offshore neogene sedimentary basins we reconstructed this two stage evolution in 3d and four steps at aegean scale by using available ages of metamorphic and sedimentary processes geometry and kinematics of ductile deformation paleomagnetic data and available tomographic models the restoration model shows that the rate of trench retreat was around 0 6 cm year during the first 30 my and then accelerated up to 3 2 cm year during the last 15 my the sharp transition observed in the mode of ex

paleomagnetism of external southern and central dinarides and northern albanides implications for the cenozoic activity of the scutari pec transverse zone paleomagnetic investigations have been conducted on 43 cretaceous to miocene sites 500 oriented cores from the southern and central external dinarides and from the northern external albanides the 24 reliable sites out of 33 from the dinarides do not document any significant rotation with respect to africa since at least early eocene this result contrasts with the very coherent post eocene 45 clockwise rotation previously observed in the external albano hellenides from peloponesus to the tirana basin these new results suggest that the scutari pec line located between the two orogens and considered as a mesozoic transform fault on the basis of geological observations is the place where the torsion between the dinarides and the albanides recently occurred on a local scale four sites out of 10 from two ridges located in northern albania south of the scutari pec line but with a dinaric trend show that these two structures have undergone a 30 post eocene clockwise rotation this intermediate value of rotation between the north and the south suggests that the scutari pec line is in fact a rather wide transversal zone in which the two ridges are located it acted as a decoupling zone between the dinarides and the albano hellenides during the cenozoic and probably until the pleistocene time the strong seismic activity recorded in this region and the anomalously high positive heat flow documented by other authors are also evidence for the recent activity of the scutari pec transverse zone

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

active tectonics of the north and central aegean sea summary in this paper we examine the connection between the westward motion of turkey relative to europe and the extension in and around the aegean sea the principal new data available since the last attempt to synthesize the tectonics of this region by mckenzie 1978 are much improved focal mechanisms of earthquakes constrained by p and sh body wave modelling as well as by first motions these mechanisms show that the faulting in the western part of the aegean region is mostly extensional in nature on normal faults with a nw to wnw strike and with slip vectors directed nnw to nne there is evidence from palaeomagnetism that this western region rotates clockwise relative to stable europe in the central and eastern aegean and in nw turkey distributed right lateral strike slip is more prevalent on faults trending ne to ene and with slip vectors directed ne palaeomagnetic data in this eastern region is more ambiguous but consistent with very small or no rotations in the northern part and possibly anticlockwise rotations relative to europe in the south the strike slip faulting that enters the central aegean from the east appears to end abruptly in the sw against the nw trending normal faults of greece the kinematics of the deformation is controlled by three factors the westward motion of turkey relative to europe the continental collision between nw greece albania and the apulia adriatic platform in the west and the presence of the hellenic subduction zone to the south as the right lateral slip on the north anatolian fault enters the aegean region it splays out becoming distributed on several parallel faults the continental shortening in nw greece and albania does not allow the rotation of the western margin of the region to be rapid enough to accommodate this distributed e w right lateral shear and thus leads to e w shortening in the northern aegean which is compensated by n s extension as the southern aegean margin can move easily over the hellenic subduction zone the dynamics of the system once initiated is self sustaining being driven by the high topography in eastern turkey and by the roll back of the subducted slab beneath the southern aegean the geometry of the deformation resembles the behaviour of a system of broken slats attached to margins that rotate in spite of its extreme simplicity a simple model of such broken slats is able to reproduce quantitatively most of the features of the instantaneous velocity field in the aegean region including the slip vectors and nature of the faulting in the eastern and western parts the senses and approximate rates of rotation the overall extensional velocity across the aegean and the distribution of strain rates as seen in the seismicity and topography or bathymetry and using geodetic measurements as part of this study we re examined the relation between the surface faulting and the focal parameters determined seismologically for the three large 1981 gulf of corinth earthquakes and reassessed the evidence for associating particular earthquakes in the sequence with observed surface faulting an important result is that in one of the events there is a resolvable discrepancy between the slip vector measured at the surface and that determined from the seismic body waves

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

signature of slab fragmentation beneath anatolia from full waveform tomography when oceanic basins close after a long period of convergence and subduction continental collision and mountain building is a common consequence slab segmentation is expected to have been relatively common just prior to closure of other oceans in the geological past and may explain some of the complexity that geologists have documented in the tibetan plateau also we focus on the eastern mediterranean basin which is the last remainder of a once hemispherical neo tethys ocean that has nearly disappeared due to convergence of the india and africa arabia plates with the eurasia plate we present new results of full waveform tomography that allow us to image both the crust and upper mantle in great detail we show that a major discontinuity exists between western anatolia lithosphere and the region to the east of it also the correlation of geological features and the crustal velocities is substantially stronger in the west than in the east we interpret these observations as the imprint in the overriding plate of fragmentation of the neo tethys slab below it this north dipping slab may have fragmented following the eocene about 35 million years ago arrival of a continental promontory central anatolian core complex at the subduction contact from the eocene through the miocene slab roll back ensued in the aegean and west anatolia while the cyprus bitlis slab subducted horizontally beneath central and east anatolia following collision of arabia about 16 million years ago the cyprus bitlis slab steepened exposing the crust of central and east anatolia to high temperature and resulting in the velocity structure that we image today slab fragmentation thus was a major driver of the evolution of the overriding plate as collision unfolded

geodetic determination of the kinematics of central greece with respect to europe implications for eastern mediterranean tectonics we use a new satellite laser ranging global positioning system slr gps solution at seven sites in anatolia and aegea to obtain a better definition of the extrusion motion of the anatolian aegean block with respect to europe we show that this motion can be described in a first approximation by a counterclockwise rotation which transfers most of the motion of arabia to anatolia we combine 78 displacement vectors obtained at common points of two triangulation nets measured in central greece in 1895 and 1975 with the slr gps measurements to compute the velocity field over greece with respect to europe these measurements indicate that central greece is a zone of extension between the anatolian aegean counterclockwise rotation to the south and the northern greece clockwise rotation to the north this extension is principally localized within the gulf of corinth to the east but is distributed to the west we then extrapolate this velocity field to the whole aegea and western anatolia using recently published gps results as well as the slr results the narrow dextral north anatolian fault which limits the velocity field to the north progressively gives way to a much wider boundary zone where extension becomes dominant we show that the collision between the mediterranean ridge and africa began 3 6 ma and we describe the modifications that this collision has produced on the kinematic pattern both in aegea and on the mediterranean ridge

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

post early messinian counterclockwise rotations on crete implications for late miocene to recent kinematics of the southern hellenic arc most geodynamical models for the kinematics of the central mediterranean recognise that major tectonic rotations must have played an important role during the neogene the hellenic arc is believed to have been subjected to clockwise rotations in the west and counterclockwise rotations in the east while the southern part crete shows no rotations kissel and laj 1988 many qualitative and quantitative models are based on the idea that crete did not rotate we present new palaeomagnetic data which show that post early messinian counterclockwise rotations have occurred on crete the amount of counterclockwise rotation generally varies between 10o and 20o but in central crete much larger rotations up to40o counterclockwise were found only a few sections did not show any rotation the anisotropy of magnetic susceptibility ams shows lineations which are consistently wnw ese throughout crete indicating post rotational wnw ese extension or nne sse compression the observed counterclockwise rotations are consistent with the results of tectonic modelling by ten veen and meijer 1998 the latter study compares the late middle miocene to recent kinematics with modelled intra plate stresses for various possible distributions of plate boundary forces observations reveal that motion along left lateral and right lateral faults occurred during the pliocene the model analysis shows these motions to be consistent with transform resistance along the eastern segment of the overriding margin the counterclockwise block rotations observed by us are probably a consequence of displacements along the left lateral and right lateral faults and could reflect a similar tectonic regime that involved transform resistance 1998 elsevier science b v all rights reserved

kinematic interpretation of the 3d shapes of metamorphic core complexes 1 metamorphic core complexes form dome shaped structures in which the ductile crust is exhumed beneath a detachment fault the 3d dome geometry inferred by mapping the schistosity in the exhumed crust can be either elongated normal to the stretching direction or along it in the first case the domes are interpreted as having formed during extension however in the second case they are interpreted either as strike slip transpressive or constrictive extensional structures depending on the geodynamic context numerical models of metamorphic core complexes published to date are all two dimensional and therefore theoretically only apply to domes which are elongated normal to the stretching direction here we explore by means of 3d thermomechanical modeling the impact of 3d kinematic extensional boundary conditions on the shape of metamorphic core complexes we examine the impact of a transtensional step over and of horsetail splay fault kinematics on the dynamics of exhumation finite strain and p t paths and compare them to cylindrical 3d models we show for the first time that domes formed in transtensional step over or at the tip of propagating strike slip faults display a finite strain field which can be interpreted as characteristic of a transpressive domes although no shortening was applied in the far field applying our models to the cyclades we propose that the coeval formation of domes elongated normal and parallel to the stretching during the miocene can be the result of horsetail splay fault kinematics which could correspond to the formation of a tear in the aegean slab

regional implications of geochemistry and style of emplacement of miocene i type diorite and granite delos cyclades greece abstract the miocene plutons of the cyclades were emplaced in a subduction setting during regional back arc extension of continental crust that led to flat lying mid crustal detachment faulting mapping of the island of delos shows that quartz diorite and tonalite were emplaced as dykes in country rock of schist and marble within shear zones parallel to the extension direction mafic magmas were followed by numerous small batches of felsic magma with magmatic and ductile deformation synchronous with magma emplacement late granite dykes occupy brittle fractures in the more deformed rocks mafic and intermediate rocks show a bimodal distribution of incompatible trace elements with one group of broadly tholeiitic character and the other with substantial enrichment in sr nb and hfse but low th and ba these differences appear to be inherited from two distinct mafic sources that are different from the mafic source for the plutons of the eastern cyclades voluminous granodiorite results from these mafic magmas fractionating and or mixing with felsic crustal material some of which was derived by anatexis of a sedimentary protolith indicated by high b and mn some late granites appear derived from partial melting of hercynian paragneiss regionally the shear zones appear to be feeders to more extensive granitic plutons located at space produced at ramps in detachment fault zones the shear zones parallel the mid cycladic lineament a broad zone of displacement between two crustal blocks rotating in opposing directions as rollback took place at the hellenic subduction zone distinctive geochemical features in miocene igneous rocks suggests that these two blocks had quite different geological histories the localisation of plutonism and core complexes near the mid cycladic lineament suggests that this crustal scale shear played a role in bringing subduction derived magmas to mid crustal levels the heat supplied by the mafic magmas promoted ductile deformation high in the crust where extension was concentrated leading to the formation of core complexes the regional extension resulted in progressive shallowing of the position of the granite solidus within the crust leading to welding of the mid cycladic lineament which is no longer seismically active

coeval plutonism and metamorphism in a latest oligocene metamorphic core complex in northwest turkey a metamorphic core complex of latest oligocene age crops out in the kazdag mountain range in northwest turkey the footwall of the core complex consists of gneiss amphibolite and marble metamorphosed at 5 1 kbar and 640 50 c the average muscovite and biotite rb sr ages from the gneisses are 19 ma and 22 ma respectively and imply high temperature metamorphism during latest oligocene times the hangingwall is made up of an unmetamorphosed lower tertiary oceanic accretionary melange with upper cretaceous eclogite lenses the hangingwall and footwall are separated by an extensional ductile shear zone two kilometres thick mylonites and underlying high grade metamorphic rocks show a n trending mineral lineation with the structural fabrics indicat ing down dip top to the north shear sense the shear zone the accretionary melange and the high grade metamorphic rocks are cut by an undeformed granitoid with a 21 ma rb sr biotite age analytically indistinguishable from the rb sr biotite ages in the surrounding footwall gneisses the estimated pressure of the metamorphism and that of the granitoid emplacement indicate that the high grade metamorphic rocks were rapidly exhumed at 24 ma from a depth of 14 km to 7 km by activity along the shear zone the subsequent exhumation of the metamorphic rocks to the surface occurred during pliocene quaternary times in a transpressive ridge between two overstepping fault segments of the north anatolian fault zone the high grade metamorphic rocks of the kazdag range are surrounded by voluminous calc alkaline volcanic and plutonic rocks of late oligocene early miocene age which formed above the northward dipping hellenic subduction zone the magmatic arc setting of the core complex and stratigraphic evidence for subdued topography in northwest turkey prior to the onset of extension suggest that the latest oligocene regional extension was primarily related to the roll back of the subduction zone rather than to the gravitational collapse

geochemistry and tectonic significance of augen gneisses from the southern menderes massif west turkey the protoliths of mylonitized augen gneisses exposed in the southern sector of the menderes massif west turkey are calc alkaline peraluminous s type late to post tectonic tourmaline and garnet bearing two mica leucogranites they cut and post date the fabrics of the main menderes metamorphism which took place between the early eocene and early oligocene and intrude metamorphic basement rocks comprising the so called palaeozoic schist envelope of the massif they are themselves cut by an extensive network of tourmaline rich dykes chemical mineralogical isotopic and field relations suggest that the granitic protolith crystallized from a boron rich water saturated melt derived from partial melting of metagreywacke in the lower crust during peak barrovian type metamorphism the protolith was probably emplaced during lateorogenic extensional collapse of the thickened crust in west turkey during late oligocene time

a comparison of geodetic and finite strain pattern in the aegean geodynamic implications abstract a comparison of the active strain pattern of the aegean constrained by global positioning system measurements and the oligo miocene finite strain field shows some striking similarities in terms of direction and rates of extension the geometry of extension at crustal scale is also very similar with north dipping normal faults connecting near the brittle ductile transition to shallow north dipping shear zones this pattern of extension is not significantly modified by the recent extrusion of the motion of anatolia and aegea the persistence over more than 25 myr of the same pattern of extension suggests that the cause for extension resides within the aegean lithosphere gravitational collapse allowed by extensional boundary conditions after 30 ma slab retreat is the primary cause for post orogenic extension in the aegean and western anatolia

spatial and temporal variation in late cenozoic back arc volcanic rocks aegean sea region abstract the aegean sea and adjacent areas comprise thinned continental crust forming an extensional back arc basin behind the south aegean arc in this back arc region are many small volcanic centres with a wide range of volcanic products this late miocene to quaternary volcanism is volumetrically minor in contrast to the voluminous igneous activity of the south aegean arc the age and major and trace element geochemistry of these back arc volcanic rocks are reviewed from the literature where necessary new geochemical analysis have been made five magma types are recognised continental alkaline basalts sodic basalts with incompatible element enrichment and nb depletion trachytes shoshonites and calc alkaline andesites all but the continental alkaline basalts appear geochemically related to subduction processes there is a regular distribution of rock types in time and space the subduction related rocks occur in a broad arc between the modern south aegean arc and the early to middle miocene volcanicity of the central aegean region sodic basalts occur in the most inboard regions and are later than the trachytes shoshonites and calc alkaline magmas occur in the most outboard regions this back arc volcanism occurs only in areas of abundant shallow seismicity however areas of extension and seismicity in the northeast aegean distant from the subducting slab lack volcanoes with the exception of the continental alkaline basalts the magmas are derived only from mantle influenced by the aseismic part of the hellenic subduction slab between 200 and 400 km depth back arc extension associated with rotation of the aegean microplate and strike slip motion on the north anatolian fault system has created a fault system allowing these magmas to reach the surface analogous processes may be common in the final stages of closure of ancient orogens

postnappe stacking extension and exhumation of high pressure low temperature rocks in the island of crete greece the island of crete consists largely of nappes of contrasting lithologies and metamorphism that were stacked southward during an oligocene early miocene n s compression with the lower nappes undergoing a high pressure low temperature hp lt metamorphism this was followed by a n s miocene crustal extension that caused thinning of the nappes and uplift of the hp lt metamorphic rocks ductile conditions took place in the lower nappes associated with a retrograde greenschist metamorphism while semiductile to brittle conditions took place in the upper nappes a major normal detachment fault separates the lower and the upper nappes the quartz texture analyses and the symmetry of structures indicate bulk coaxial deformation while the results of strain analysis suggest both constrictional and flattening strains a younger ne sw compression affected both the thinned nappe pile and the late miocene pliocene sedimentary basins finally a pliocene ne sw extension led to further uplift and exhumation of the hp lt metamorphic rocks this cyclic tectonometamorphic process of alternate compression and extension took place during the migration of the hellenic orogenic belt toward the most external units including successive tectonic events

seismicity of the hellenic subduction zone in the area of western and central crete observed by temporary local seismic networks temporary local seismic networks were installed in western crete in central crete and on the island gavdos south of western crete respectively in order to image shallow seismically active zones of the hellenic subduction zone more than 4000 events in the magnitude range between 0 5 and 4 8 were detected and localized the resulting three dimensional hypocenter distribution allows the localization of seismically active zones in the area of western and central crete from the mediterranean ridge to the cretan sea furthermore a three dimensional structural model of the studied region was compiled based on results of wide angle seismics surface wave analysis and receiver function studies the comparison of the hypocenter distribution and the structure has allowed intraplate and interplate seismicity to be distinguished high interplate seismicity along the interface between the subducting african lithosphere and the aegean lithosphere was found south of western crete where the interface is located at about 20 to 40 km depth an offset between the southern border of the aegean lithosphere and the southern border of active interplate seismicity is observed in the area of crete the offset varies laterally along the hellenic arc between about 50 and 70 km a southwards dipping zone of high seismicity within the aegean lithosphere is found south of central crete in the region of the ptolemy trench it reaches from the interface between the plates at about 30 km depth towards the surface in comparison the aegean lithosphere south of western crete is seismically much less active including the region of the ionian trench intraplate seismicity within the aegean plate beneath crete and north of crete is confined to the upper about 20 km between 20 and 40 km depth beneath crete the aegean lithosphere appears to be seismically inactive in western crete the southern and western borders of this aseismic zone correlate strongly with the coastline of crete

the lateral boundary of a metamorphic core complex the moutsounas shear zone on naxos cyclades greece we describe the structure microstructures texture and paleopiezometry of quartz rich phyllites and marbles along n trending moutsounas shear zone at the eastern margin of the naxos metamorphic core complex mcc fabrics consistently indicate a top to the nne non coaxial shear and formed during the main stage of updoming and exhumation between ca 14 and 11 ma of the naxos mcc the main stage of exhumation postdates the deposition of overlying miocene sedimentary successions and predates the overlying upper miocene pliocene conglomerates detailed microstructural and textural analysis reveals that the movement along the moutsounas shear zone is associated with a retrograde greenschist to subgreenschist facies overprint of the early higher temperature rocks paleopiezometry on recrystallized quartz and calcite yields differential stresses of 20 77 mpa and a strain rate of 10 15 10 13 s 1 at 350 c for quartz and ca 300 c for calcite chlorite geothermometry of the shear zone yields two temperature regimes 300 360 c and 200 250 c the lower temperature group is interpreted to result from late stage hydrothermal overprint

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

geochronology of clasts in allochthonous miocene sedimentary sequences on mykonos and paros islands implications for back arc extension in the aegean sea in the cyclades low angle normal faults juxtaposed miocene sedimentary rock units lying over alpine blueschist and greenschist facies metamorphic rocks and miocene granites the sedimentary units in the hanging wall were deposited in fault bounded basins while their footwalls progressively emerged through the ductile and brittle crust the sedimentation in the basins evolved from marine turbidites in the early miocene to shallow continental conglomerates during the late miocene the transition from marine to fan delta sedimentation was coeval with widespread magmatism and possibly reflects true crustal uplift it is inferred that the sequence is no younger than 8 ma k ar and 40 ar 39 ar geochronology petrology and petrography of the clasts deposited on the hanging wall provide proof of progressive exhumation of the footwall and reveal the nature of the overburden that covered the cycladic blueschist belt during alpine orogeny in the tertiary abundant metamorphic clasts yielding mica cooling ages between 80 and 100 ma occur throughout the sedimentary section and probably pertain to a vast pelagonian type rock mass that covered the internal hellenides from the olympos to the central cyclades in addition volcanic clasts dated at 10 ma reveal the existence of a hitherto unknown volcanic province of that age in the central aegean miocene crustal extension and exhumation of granitic plutons is recorded in the detrital sequence in a concentration of 10 ma granitic clasts restricted to the top of the conglomerate sequence a group of metamorphic clasts that yielded ages of 13 16 ma possibly represents exhumation of mid crustal levels clasts similar to the currently exposed cycladic blueschist unit such as 40 ma old blueschists eclogites and marble were not found thus indicating the very late exposure of these footwall rocks

constraints on the evolution and vertical coherency of deformation in the northern aegean from a comparison of geodetic geologic and seismologic data abstract we study the 3 d strain evolution of the northern aegean and the vertical coherency of deformation we observe that finite strain orientations in the mantle inferred from published shear wave sks fast polarization orientations mid to upper crustal stretching lineations in metamorphic core complexes of mainly miocene age and the gradient in regional crustal thickness variations are subparallel to one another this correlation suggests that the miocene phase of extension is imprinted in the anisotropic fabric i e lattice preferred orientation lpo of the lithospheric mantle and that the orientation of finite strain due to extension is nearly constant with depth the lateral variation of published seismic delay times shows a correlation with laterally varying finite strain in the crust inferred from topography and crustal thickness estimates this correlation suggests that lateral variations in finite crustal and mantle strain are correlated and may point at a pure shear extension mechanism involving the entire lithosphere we also present a new strain rate model for the northern aegean based on global positioning system gps velocities and additional geological constraints no length change orientations calculated from the model near the north anatolian fault naf and north aegean trough are not consistent with anisotropy orientations at depth present day extension orientations are systematically and significantly more n s oriented than the stretching lineations and sks splitting orientations we conclude that the current shear dominated surface deformation pattern is not yet reflected by significant anisotropy in the lithosphere based on some simple calculations we postulate that the present day deformation pattern cannot be older than 4 ma which is consistent with independent arguments on the timing of the propagation of the north anatolian fault into the aegean domain

rapid early middle miocene exhumation of the kazdag massif western anatolia apatite fission track analyses indicate that the kazdag massif in northwestern anatolia was exhumed above the apatite partial annealing zone between 20 and 10 ma i e early middle miocene with a cluster of ages at 17 14 ma the structural analysis of low angle shear zones high angle normal faults and strike slip faults as well as stratigraphic analysis of upper plate sedimentary successions and previous radiometric ages point to a two stage structural evolution of the massif the first stage encompassing much of the rapid thermal evolution of the massif comprised late oligocene early miocene low angle detachment faulting and the associated development of small supradetachment grabens filled with a mixture of epiclastic volcaniclastic and volcanic rocks kucukkuyu fm the second stage plio quaternary has been dominated by i strike slip faulting related to the westward propagation of the north anatolian fault system and ii normal faulting associated with present day extension this later stage affected the distribution of fission track ages but did not have a component of vertical normal movement large enough to exhume a new partial annealing zone the thermochronological data presented here support the notion that neogene extensional tectonism in the northern aegean region has been episodic with accelerated pulses in the early middle miocene and plio quaternary

the geometrical evolution of normal fault systems abstract the purpose of this paper is to examine the kinematic behaviour of normal fault systems and see what general conditions govern their geometrical evolution we pay particular attention to seismological and surface data from regions of present day active normal faulting as the instantaneous three dimensional geometry at the time of fault movement is better known in active regions than in areas where the faults are now static most normal faults are concave upward or listric this shape can be produced by geometric constraints either because the faults reactivate curved thrusts or because they must be curved to accommodate rotations another effect which will produce curved faults is the variation of rheology with depth brittle failure at shallow depths produces less fault rotation than does distributed creep in the lower part of the crust an important geometric feature of normal faulting is the uplift of the footwall the amount of such uplift is related not only to the elastic properties of the lithosphere but also to the throw and dip of the fault a striking feature of active normal faults is that they occur in groups in which all the faults dip in the same direction this behaviour arises because the faults cannot intersect if they do one must cease to be active the rotation which such fault systems produce reduces the dip of the faults until a new steeply dipping fault is formed once a new fault cuts pre existing faults the earlier faults become locked and a new set of faults must propagate rapidly across the whole region involved many of these geometric constraints also apply to thrust faulting

granite intrusion in a metamorphic core complex the example of the mykonos laccolith cyclades greece abstract the aegean domain is a well suited place to study the formation of metamorphic core complex mcc and to investigate the role of syn tectonic granites on their development in the northern cyclades the mykonos delos rhenia mcc is characterized by the intrusion of a kilometer scale late miocene pluton of i type granitoids within a migmatitic gneiss dome new combined ams anisotropy of magnetic susceptibility and microstructural studies on the mykonos granitoids together with recently published thermochronological data allow us to use the granitoids as strain markers the mykonos granitoids form a laccolith like intrusion with a n70 e long axis the laccolith is strongly asymmetric with an outlying root zone to the sw and a major body mainly developed to the ne the laccolith construction is due to successive pulses of more or less differentiated magma that intruded the cycladic blueschist unit the attitude of stretching markers suggests an important about 60 vertical axis local rotation phenomenon in the cycladic upper crust during the exhumation of the mykonos mcc structural data suggest a four stage evolution of the mykonos mcc i a first stage characterized by flat shearing toward the n ne and by the formation of a domal structure in migmatitic paragneisses with multi scale generation of folds with axes either perpendicular or parallel to the regional stretching as a result of the interplay between regional n20 e directed extension and ew shortening ii a second stage marked by the emplacement of the mykonos laccolith at 13 5 0 3 ma at the top of the migmatitic paragneisses iii the third stage corresponding to the development of protomylonitic foliations and lineations in the whole laccolith in high to medium temperature conditions and iv the late stage marked by an acceleration of the exhumation of the mykonos mcc this exhumation was accommodated by important rotations of upper crustal blocks during the end of the exhumation processes around 10 ma deformation localized at the top of the laccolith in semi ductile conditions and then in brittle conditions in the major detachment plane our study shows that the cycladic plutonism event had no role on the initiation of the mcc however the geometry of the mykonos intrusion supports that the magmas are sucked into the direction of regional extension and that the intrusion of magmas has caused an acceleration of the last stages of the mcc development this acceleration was marked by a very fast exhumation of the laccolith after its emplacement

rapid exhumation of high pressure metamorphic rocks in kythera peloponnese greece revealed by apatite u th he thermochronology abstractapatite u th he and apatite fission track cooling ages from high pressure hp metamorphic rocks in the south aegean forearc along the kythera strait kythera and southeastern peloponnese suggest rapid exhumation during middle to late miocene times hp rocks from the kythera strait exhibit two perpendicular extensional structures samples with arc normal or arc parallel extensional fabrics yielded apatite u th he cooling ages of 8 10 ma the more precise u th he ages are consistent with previously reported apatite and zircon fission track ages obtained from the same rock units the less precise but still accurate fission track data provided a reference for u th he dating on relatively young uranium poor apatites the combined data therefore precisely and accurately constrain the exhumation history of hp rocks and indicate that localized arc parallel extension in the kythera strait was active for an 5 m yr interval during the regional arc expansion

rotational deformation during palaeogene thrusting and basin closure in eastern central greece palaeomagnetic evidence from mesozoic carbonates summary palaeomagnetic studies in greece have concentrated upon neogene sequences with mesozoic rocks of mainland greece receiving little attention the neogene data base is now sufficiently extensive however to allow meaningful interpretation of older units this paper presents new palaeomagnetic data from mesozoic and tertiary sequences of eastern central greece which document a pre neogene phase cf rotational deformation mesozoic carbonates have been sampled within the classic pelagonian zone in the argolis peninsula beotia and evvia pelagonian sequences record the development drowning and subsequent re establishment of a carbonate platform separating two strands of the neotethys ocean the pindos and vardar basins most platformal facies are tdo weakly magnetized for palaeomagnetic analysis however pelagic horizons consisting of pink condensed limestones have been deposited periodically in response to platform subsidence these middle late triassic jurassic and upper cretaceous sequences yield high quality palaeomagnetic data which reveal a consistent clockwise rotation of about 94 the constancy of rotation angle deduced from the mesozoic rocks suggests that the total tertiary rotation is uniform throughout the area studied this implies that observed variations in declination within the neogene sequences result from sampling of rocks of different ages deposited during a period of rapid overall rotation removal of the largest neogene rotation 45 from the mesozoic data set reveals a pre middle miocene post late cretaceous clockwise rotation of the southern pelagonian zone of 50 the major tectonic event during this time period was the closure of the pindos ocean during the eocene a large carbonate platform within the pindos basin now preserved in the parnassos zone presented a major obstacle to the advancing pelagonian nappes during sw directed thrusting present coordinates impingement of the nappes on to the parnassos platform resulted in pinning and subsequent clockwise rotation of thrust units around the south eastern margin of the platform the southernmost tip of the pelagonian zone southern argolis was detached along a pre existing line of weakness along the present migdhalitsa graben and experienced a different rotation history additional palaeomagnetic data from the pindos nappes in the eastern peloponnesos also provide evidence for significant rotation of thrust sheets during eocene basin closure the pindos sequences formed by pelagic sedimentation within the pindos ocean an overall anti clockwise rotation with respect to the underlying gavrovo tripolitza autochthon is implied by the data this probably reflects oblique emplacement of the pindos thrust sheets on to the adjacent platform variations in rotation angle probably result from variations in footwall topography

texture microstructure and strength of hematite ores experimentally deformed in the temperature range 600 1100 c and at strain rates between 10 4 and 10 6 s 1 abstract polycrystalline hematite samples cored perpendicular and parallel to the foliation i e perpendicular and parallel to a weak c axis maximum respectively were deformed in triaxial compression experiments at confining pressures of 300 and 400 mpa temperatures t between 600 and 1100 c and strain rates between 10 4 and 10 6 s 1 the measured strength of hematite ranges from 890 to 67 mpa the grain size of the main starting material is up to 175 m grain boundaries are intensely serrated at t 800 c the grain boundaries become increasingly lobate and the number of r twins decreases dynamic recrystallization starts above 800 c and a foam structure with grain sizes up to 150 m develops at t 900 c neutron diffraction measurements show a distinct change of the preferred orientation texture in compression parallel to the foliation below 800 c a 300 maximum developed due to a m slip at 800 and 900 c a c axis maximum evolved probably due to c a slip the original texture is preferentially preserved but with lower densities at t 1000 c presumably caused by increasing diffusional flow processes perpendicular to the foliation only minor changes of the texture occurred the experimentally determined textures allow a better understanding of the natural preferred orientation of hematite ores the extrapolation of experimental strength data of hematite quartz and carbonates to geological conditions are compatible with field observations

late miocene to recent tectonic evolution of crete greece geological observations and model analysis abstract using a numerical model we focus on the late middle miocene to recent kinematic evolution of the cretan segment of the hellenic arc geological observations of crete are given a quantitative interpretation in terms of tectonic mechanisms controlling the evolution of the active arc boundary this was achieved by calculating intra plate stress fields for various possible distributions of forces and comparing the models with observations the models address specific questions concerning important changes in the observed horizontal stress patterns we deal with the question of what caused extension to initiate modelling results of the collapse of an earlier formed topography and extensional forces acting on the plate boundary are compared with a newly reconstructed tectonostratigraphy of crete our results suggest that arc normal pull is the dominant force that generates the late miocene extension in the cretan segment of the overriding plate although arc normal pull in combination with intra plate spreading forces cannot be excluded the observed transform motions in the pliny and strabo trenches led us to incorporate experiments with additional resistance on the eastern levantine segment of the hellenic arc the models performed with a transform resistance along the trenches are in agreement with the cretan deformation for the pliocene to recent period the stress fields for the short duration compressional periods around the middle late miocene and the miocene pliocene boundary are modelled by assuming resistive instead of tensional forces acting at the overriding margin

extension and exhumation of the hp lt rocks in the hellenic forearc ridge localized intensive ductile and ductile brittle extension of along the arc orientation is prominent in phyllite quartzite unit pqu rocks in kythera and the adjacent southeastern peloponnese but declines in prominence to the north and to the south along the cretan peloponnese ridge using zircon and apatite fission track dating we find that this structural characteristic is correlated with the youngest zircon fission track cooling ages of 14 to 9 ma and with the highest pressure temperature condition recorded in the metamorphic rocks below the structural detachment the cooling ages of the high pressure phyllite quartzite unit pqu rocks along the hellenic forearc ridge show that exhumation migrated from both crete and from the peloponnese to the area with the youngest ages in kythera and the southeastern peloponnese starting in the early miocene and continuing to the present trench rollback and slab retreat expanded the hellenic arc and this bending of the arc from an initial more rectilinear geometry increased areas of oblique convergence and we suggest this localized the subsequent arc parallel extension and local enhanced exhumation of hp rocks the zircon fit exhumation ages from the arc parallel stretching episode restrict the ductile part of this episode in exposed rocks to between about 14 and 9 ma apatite ft ages suggest brittle along arc extension continued to about 7 ma this episode is proposed to be the result of a temporary higher rate of rollback and slab retreat younger normal faults including those which define the margins of the present hellenic arc show return to arc normal extension

quaternary evolution of the corinth rift and its implications for the late cenozoic evolution of the aegean summary we present geological and morphological observations at different scales to constrain rates of faulting and the distribution of deformation in the seismically active aegean region we focus first on the 130 km long corinth rift an asymmetric graben where a flight of terraces of marine origin are uplifted we show that the edges of the terraces lie in the footwall of the normal fault bounding the corinth rift and correspond to sea level highstands of laic pleistocene age using a detailed analysis of aerial and spot imagery supported by field observations we have mapped 10 terrace platforms and strandlines ranging in elevation from 10 to 400 m over distances of 2 to 20 km from the fault the elevation of the terraces inner edges was estimated at 172 sites with an error of 5m this data set contains a precise description of the uplift and flexure of 10 different palaeohorizontal lines with respect to the present sea level to date the deformation we correlate the corinth terraces with late pleistocene oxygen isotope stages of high sea level stands and with global sea level fluctuations using a thick elastic plate model consistent with our current understanding of the earthquake cycle and a boundary element technique we reproduce the geometry of the shorelines to constrain both mechanical parameters and the slip on the fault we show that the seismogenic layer behaves over the long term as if its elastic modulus were reduced by a factor of about 1000 all the terraces are fitted for fault slip increasing in proportion to terrace age and the component of regional uplift is found to be less than 0 3 mm yr 1 the best fits give a slip rate of 11 3 mm yr 1 on the main rift bounding fault over the last 350 kyr other geological and morphologic information allows us to estimate the total age of the main fault 1 ma and to examine the mechanical evolution of the corinth rift the minimum observed sediment thickness in the gulf places an extreme check on the results of the modelling and a lower bound on slip rate of 6 7 mm yr 1 40 per cent less than estimated with modelling even this slip rate is nearly 10 times higher than for comparable features in most of the aegean and elsewhere in the world at a larger scale the spacing and asymmetry of the rift systems in the aegean suggest strain localization in the upper mantle with slow extension starting 15 myr ago or earlier the more recent 1 myr rapid phase of rifting in corinth partly reactivated this earlier phase of extension the younger faulting in corinth appears to result from its present location in the inhomogeneous stress field process zone of the south westward propagating tip of the southern branch of the north anatolian fault we extend these relations to propose a mechanical model for the late cenozoic evolution of the aegean as the arabia europe collision progressed in eastern turkey it caused anatolia to move to the west and the north anatolian fault to propagate into the aegean where the early slow extension started to be modified about 5 ma ago the process of propagation dramatically increased the activity of some but not all of the earlier rifts the model we present is compatible with tectonic observations as well as with the seismicity the palaeomagnetic rotations and the displacement field now observed with gps and slr

study of the crustal thickness and the subducting lithosphere in greece from gravity data the area of greece has experienced a complex tectonic history dominated by the subduction of the african plate beneath eurasia in this study the variations of the crustal thickness in the area of greece were obtained by means of the multiple source werner deconvolution mswd method applied to gravity data thicknesses of 40 49 km are estimated beneath the hellenides mountain belt to the west eastward thinning of the crust to thicknesses ranging from 25 km in the north to 30 km in the south is seen in the aegean region these results are in good agreement with recent seismological results demonstrating that the mswd method successfully treated the problem using the crustal model we derived we computed the gravity effect of the crust and extracted it from the bouguer anomaly we also extracted the gravity effect of the subducting lithosphere from the bouguer anomaly producing a residual map where most of the original gravity variation has been successfully removed the remaining anomalies appear related to near surface features and an area of low velocity mantle in the central aegean sea

revision of the timing magnitude and distribution of neogene rotations in the western aegean region to evaluate the dimension and the timing of the clockwise rotating domain and the nature of the structures that accommodate the rotating domain in the western aegean region paleomagnetic analyses were carried out in northern western and southwestern greece the results show that the rotating domain covers an area including the external albanides western mainland greece including evia and probably at least partly the peloponnesos smaller clockwise rotations on the order of 30 408 were reported previously from the chalkidiki peninsula and the islands of skyros and limnos previously two phases of approximately 258 of rotation were suggested the last one during the plio pleistocene our analysis shows that the western aegean domain rotated approximately 408 clockwise between 15 13 and 8 ma followed by an additional 108 after 4 ma the rotating domain is accommodated in the north by deformation associated with the scutari pec fault zone and in the west by the ionian thrust and the hellenic subduction zone to the south no rocks older than 10 ma are available so no conclusive data are obtained to the east of the rotating domain extensional detachment systems of the cyclades and rhodope areas were active during the rotation phase and may explain at least part of the differences in finite amounts of rotation between nonrotation or counterclockwise rotations observed in northern and eastern greece and the large clockwise rotations in western greece d 2004 elsevier b v all rights reserved

petrology mineral chemistry and sr nd pb isotopic compositions of granitoids in the central menderes metamorphic core complex constraints on the evolution of aegean lithosphere slab abstract plutonic associations in the central menderes metamorphic core complex are suitable rocks in order to understand the magma forming processes in extended terrains syn extensional salihli and turgutlu granitoids have granodioritic composition and contain monzonitic and monzodioritic microgranular enclaves they are transitional metaluminous peraluminous and high k calc alkaline in character and are located on i and s type transition salihli and turgutlu granodiorites are geochemically similar to each other while their microgranular enclave chemistry is in contrast with low sio2 and high mg values mineral chemistry data from granodiorites and mafic microgranular enclaves confirm their shallow emplacement at about 7 km geochemical modelling suggests that syn extensional granitoids were derived from the mixing of mantle and lower crustal components which were finally modified by a significant amount of upper crustal contamination and fractional crystallization processes at shallow crustal levels early middle miocene syn extensional granitoids across the aegean region form a magmatic belt associated with roll back of the aegean lithosphere slab roll back induced magmatism together with ductile deformation in western turkey ceased after cooling of the salihli granodiorites at 12 2 ma but core complex related magmatism was continuous in the cycladic metamorphic core complex during late miocene and was followed by an active arc volcanism in the southern aegean such abrupt change from ductile to brittle mode of extension in western turkey can be explained by opening of a slab window on the aegean lithosphere slab which would lead to upwelling of fertile subslab asthenospheric mantle forming transitional and finally oib type basalts

s velocity structure and radial anisotropy in the aegean region from surface wave dispersion summary the lithospheric structure of the aegean region is investigated by analysis of rayleigh wave fundamental mode dispersion measurements isotropic 1 d models for almost 100 two station ray paths across the region display distinct variations in the moho depth and crustal s wave velocities the descending slab of the subducting african plate can be resolved down to 120 km depth beneath the volcanic arc three different regions are distinguished in terms of moho depth 1 the forearc with large crustal thicknesses between 38 and 48 km and an average of 43 km 2 the northern aegean with an average moho depth of 28 km and 3 the southern aegean central volcanic arc i e cyclades and sea of crete with an even thinner crust of around 25 km lateral variations in structure between 25 and 55 km depth indicate a marked difference between the western and eastern forearc collocated with pronounced changes in trench and slab geometry as well as published deformation rates s velocities between 25 and 55 km depth are low everywhere beneath the forearc but increase from the peleponnesus to crete an abrupt change occurs between western and central crete in terms of the visibility of the aegean moho and the seismic structure of the lithospheric mantle wedge an aegean mantle wedge with s velocities above 4 4 km s 1 is only observed to the east of central crete whereas to the west velocities of less than 4 0 km s 1 occur down to the plate contact these low velocities above the slab may indicate the presence of a melange of metamorphic rocks at the depths a low velocity asthenospheric layer is observed beneath the sea of crete and the cyclades below 40 km depth between the thinned lithosphere above and the slab below the observed radial anisotropy in the northern part of the aegean is likely to be due to preferred orientation of anisotropic minerals within the lower crust possibly caused by lateral ductile flow associated with recent lithospheric extension

i and s type plutonism on serifos w cyclades greece abstract tertiary i and s type plutonism is widespread in the aegean region and frequently associated with extensional tectonic structures this investigation presents the first evidence of protracted magmatism on the island of serifos in the western cyclades and at least two discrete generations of plutonism and coeval dyke generations can be distinguished 1 an older granitoid with s type characteristics intruded the attic cycladic crystalline rocks the granitoid and its host rocks were mylonitized by an earlier phase of deformation at temperature conditions 450 c and wsw directed shear this crustal scale ductile shear zone has been reactivated during the initial stage of a metamorphic core complex formation recording top ssw sense of shear rb sr muscovite data from the orthogneiss yield cooling respectively deformation ages of 15 11 3 ma 2 an i type hornblende biotite granodiorite pluton with dacitic to andesitic dyke generations intruded syn to post kinematically during ongoing extensional deformation at shallow crustal levels single grain zircon tims u pb ages of the main granodiorite body and its associated dykes are 11 6 9 5 ma cooling ages of these samples scatter between 8 5 and 7 7 ma rb sr on biotite

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

deciphering subduction from exhumation in the segmented cycladic blueschist unit central aegean greece the cycladic blueschist unit cbu represents the northern passive margin of the adria continental block and ophiolites that are the remnants of the pindos ocean which were affected by high pressure low temperature metamorphism in the blueschist and eclogite facies during the eocene prior to the lutetian the ophiolitic and margin units were thrust towards the sw inside a ne dipping subduction zone two subsequent exhumation stages are characterized by top to the ne senses of shear i from mantle depths to lower crustal levels before 37 ma which was accommodated by an extensional inversion of the vardar suture zone and ii from deep crustal levels to the near surface between 30 and 20 ma which was accommodated by the north cycladic detachment it is during this late stage of ductile exhumation that the central cyclades core complex was exhumed segmentation of the cbu by normal faults started at 12 ma as recorded by the low temperature thermochronometers and was coeval with block rotation and folding with ns trending axes which were predominantly controlled by the myrthes ikaria strike slip fault in the centre of the cyclades a map restoration of the cbu geometry prior to segmentation has been carried out using available structural and paleomagnetic data the restoration shows that following the cbu exhumation from mantle depths to crustal levels a single core complex was exhumed along a single ne dipping detachment

paleomagnetic evidence for an inverse rotation history of western anatolia during the exhumation of menderes core complex abstract within the aegean extensional system the izmir balikesir transfer zone ibtz is a crucial element in the late cenozoic evolution of western anatolia since it accommodates the differential deformation between the cycladic and the menderes metamorphic core complexes here we determine the rotational history of western anatolia using new paleomagnetic data from 87 sites in miocene volcano sedimentary rocks to better understand the role of the ibtz our results reveal two discrete and opposite major rotational phases during the miocene the first phase is derived from early miocene volcanic sedimentary and granitic rocks and is controlled by detachment and strike slip faults it is characterized by an average net 23 6 clockwise cw rotation within the ibtz since the early miocene our new data from the menderes part on the other hand show an average 23 10 counter clockwise ccw rotation the data from the cycladic part show no significant net rotation since the early miocene the second phase is derived from middle late miocene volcanic and sedimentary rocks and is controlled by high angle normal and strike slip faults the rotations from this phase show a very consistent pattern of 22 11 ccw within the ibtz while now the menderes part shows an average cw rotation of 25 14 our paleomagnetic results hence document a major change and inversion of rotation between the early and late miocene the ibtz region experienced a large 45 cw rotation while during the same time interval the menderes part outside the zone experienced a similar 48 ccw rotation after that the ibtz became narrower and the sense of rotation inverted to ccw 23 10 since the late miocene while in the menderes part it inverted to cw 25 14 since the late miocene our new results do therefore fit the hypotheses of two stage extension scenario rather than a one single phase of extension we also conclude that the observed rotations are not directly related to major detachment faulting but to the change in extensional regime of western anatolia the focal mechanism solutions of recent seismic events corroborate that the ibtz is still active and transfers west anatolian extensional strain into the south aegean sea

tectono stratigraphy of the neogene basins in western turkey implications for tectonic evolution of the aegean extended region abstract the western part of the aegean region includes several neogene basins containing volcano sedimentary successions the neogene basins located along the northern menderes extensional metamorphic complex memc were developed during the miocene as supra detachment basins they contain two distinct volcano sedimentary successions separated by a regional unconformity the basins located to the west of the memc were developed as strike slip basins and contain volcanic and sedimentary units getting younger from ne to sw with no remarkable unconformity available paleomagnetic studies in the aegean region suggest to us that the basins to the west of the memc were developed in response to southward clockwise rotational roll back of the aegean subduction zone the eastern margin of this rotational deformation is characterized on the surface by a large strike slip zone which is known as izmir balikesir transfer zone ibtz the sedimentary successions in the basins along the northern memc do not show southward younging and are interpreted to be developed in response to exhumation of the memc during the pliocene to quaternary e w trending grabens such as the gediz alasehir buyuk and kucuk menderes grabens were developed in response to tectonic escape accompanying the slab roll back process these grabens truncate the memc basins during this time strike slip deformation and associated sedimentation continued along the ibtz

ductile nappe stacking and refolding in the cycladic blueschist unit insights from sifnos island south aegean sea new geological and structural mapping combined with kinematic and amphibole chemistry analyses is used to investigate the deformation history of the cycladic blueschist unit cbu on sifnos island cyclades aegean sea we concentrate on north sifnos an area characterized by exceptionally well preserved eclogites and blueschists our data show that the early main phase d2 of ductile deformation in the cbu occurred synchronous with the transition from prograde to close to peak retrograde conditions this deformation phase took place at middle eocene and is related to ese directed thrusting that emplaced the metavolcano sedimentary subunit over the marble subunit the subsequent exhumation related d3 deformation is characterized by gently ne plunging folds and ne directed contractional shear zones that formed parallel to the axial planes of folds ne directed shearing occurred under blueschist and transitional blueschist greenschist facies conditions during late eocene oligocene and caused the restacking of the early nappe pile we suggest that a mechanism of ductile extrusion of the cbu in a tectonic setting of net compression could explain better the recorded exhumation related deformation than a mechanism of syn and post orogenic extension our new kinematic results in combination with previous works in the cyclades area reveal a regional scale change in tectonic transport direction from w nw e se at late cretaceous middle eocene to e ne w sw at late eocene oligocene times the observed change in transport direction may be governed by the relative motion of africa with respect to europe during alpine orogeny

map view restoration of aegean west anatolian accretion and extension since the eocene 1 the aegean region greece western turkey is one of the best studied continental extensional provinces here we provide the first detailed kinematic restoration of the aegean region since 35 ma the region consists of stacked upper crustal slices nappes that reflect a complex paleogeography these were decoupled from the subducting african adriatic lithospheric slab especially since 25 ma extensional detachments cut the nappe stack and exhumed its metamorphosed portions in metamorphic core complexes we reconstruct up to 400 km of trench perpendicular ne sw extension in two stages from 25 to 15 ma the aegean forearc rotated clockwise relative to the moesian platform around euler poles in northern greece accommodated by extensional detachments in the north and an inferred transfer fault se of the menderes massif the majority of extension occurred after 15 ma up to 290 km by opposite rotations of the western and eastern parts of the region simultaneously the aegean region underwent up to 650 km of post 25 ma trench parallel extension leading to dramatic crustal thinning on crete we restore a detachment configuration with the mid cycladic lineament representing a detachment that accommodated trench parallel extension in the central aegean region finally we demonstrate that the sakarya zone and cretaceous ophiolites of turkey cannot be traced far into the aegean region and are likely bounded by a pre 35 ma n s fault zone this fault became reactivated since 25 ma as an extensional detachment located west of lesbos island the paleogeographic units south of the izmir ankara sava suture however can be correlated from greece to turkey

the geological signature of a slab tear below the aegean in this paper we explore the geology of the aegean region in the miocene to identify the geological signature of a first order slab tear observed in all tomographic models from 15 to 8 ma the tear is associated spatially and timely with a fast clockwise rotation of the external hellenides alkaline volcanism high temperature metamorphic domes with a predominance of north dipping detachments and south westward migration of granitoid intrusions these features suggest a warmer geodynamic environment during the rotation and the impact of a hot mantle flow associated with the tear the 8 ma duration between the first high temperature metamorphic domes in the centre of the archipelago and the beginning of the fast rotation may correspond to the time needed for the slab to bend stretch and finally tear

complex layered deformation within the aegean crust and mantle revealed by seismic anisotropy continental lithosphere can undergo pervasive internal deformation often distributed over broad zones near plate boundaries however because of the paucity of observational constraints on three dimensional movement at depth patterns of flow within the lithosphere remain uncertain endmember models for lithospheric flow invoke deformation localized on faults or deep shear zones or alternatively diffuse viscous fluid like flow here we determine seismic rayleigh wave anisotropy in the crust and mantle of the aegean region an archetypal example of continental deformation our data reveal a complex depth dependent flow pattern within the extending lithosphere beneath the northern aegean sea fast shear wave propagation is in a north south direction within the mantle lithosphere parallel to the extensional component of the current strain rate field in the south central aegean where deformation is weak at present anisotropic fabric in the lower crust runs parallel to the direction of palaeo extension in the miocene the close match of orientations of regional scale anisotropic fabric and the directions of extension during the last significant episodes of deformation implies that at least a large part of the extension in the aegean has been taken up by distributed viscous flow in the lower crust and lithospheric mantle

late cainozoic geodynamic evolution of thessaly and surroundings central northern greece abstract in the framework of the late alpide deformation of greece and of the recent and active extensional tectonism of the aegean region the geotectonic evolution of the thessaly region central northern greece has been examined using a quantitative and qualitative structural analysis stratigraphie sedimentological morphotectonic and seismological data the geometry of the faults their architecture and the knowledge of the stress pattern are used to explain some aspects of the tectonics and crustal dynamics of thessaly and the surrounding area the oldest compressional phases taken into account show a mean ene wsw trending direction of shortening and have been defined as late alpide early aquitanian and langhian a later late miocene pliocene ne sw oriented extensional phase has been related to the hellenic post orogenic collapse which developed behind the collisional front between the aegean eurasia and african plates this phenomenon diachronically migrated from the east central macedonia thermaikos basin towards the west epirus albania where it is still active as a consequence of this second phase the area forms a basin and range like structure the third and last phase middle pleistocene present is characterized by a n s direction of extension and affects the entire aegean region it generated new e w trending basins superimposed on the inherited ones this gave as a final result the complex block pattern we can see today the recent and active right lateral strike slip movements along the north aegean trough seem to stop in the sporades basin and do not affect the uppermost crust of mainland greece a further wnw ese directed extension observed occasionally in central and northern greece could be explained by local events or as block related deformation

coupled crust mantle response to slab tearing bending and rollback along the dinaride hellenide orogen we integrate structural geophysical and geodetic studies showing that the dinarides hellenides orogen along the adria europe plate boundary in the western balkan peninsula has experienced clockwise oroclinal bending since eocene oligocene time rotation of the hellenic segment of this orogen has accelerated since the middle miocene and is associated with a north to south increase in shortening along the orogenic front within the paleogene nappe pile bending was accommodated by orogen parallel extension clockwise block rotation and thrusting in the hanging wall of the skhoder peja normal fault spnf the spnf and related faults cut the older skhoder peja transfer zone with its pre neogene dextral offset of the west vardar ophiolite nappe rotation of the spnf hanging wall involved miocene to recent out of sequence thrusting that was transferred to the hellenic orogenic front via lateral ramps on dextral transfer zones along strike of the dinarides hellenides and coincident with the southward increase in neogene shortening the depth of the adriatic slab increases from 160 km north of the spnf to 200 km just to the south thereof to several hundreds of kilometers to the south of the kefalonia transfer zone the geodynamic driver of tectonics since the early miocene has been enhanced rollback of the hellenic segment of the adriatic slab in the aftermath of eocene oligocene slab tearing and breakoff beneath the dinarides which focused slab pull in the south the sw retreating hellenic slab segment induced clockwise bending of the southern dinarides and northern hellenides including their adriatic foreland about a rotation pole in the vicinity of the mid adriatic ridge

magma interaction processes in syn extensional granitoids the tertiary menderes metamorphic core complex western turkey abstract western turkey which forms the eastern part of the aegean region was subjected to continental extension that led to formation of metamorphic core complexes and associated syn extensional granitoids this study deals with petrogenesis of the syn extensional early miocene alacamdag ag and middle miocene salihli sg granitoids and associated mafic microgranular enclaves mme in order to better understand the time progressive evolution of the mantle sources beneath the extended continental crust in western turkey ag and sg granitoids consist of undeformed and ductility deformed granitoids together with abundant mmes they are calc alkaline to high k calc alkaline rocks that are metaluminous to slightly peraluminous mg of ag host rocks is slightly lower than that of sg host rocks ag host rocks have higher na 2 o ba rb rb la and lower al 2 o 3 cao mgo tio 2 zr y values than those of the sg host rocks ag and sg host rocks differ from those of mmes with their lower al 2 o 3 cao mgo fe 2 o 3 tio 2 sr v mg and higher sio 2 values mmes are intermediate corresponding to monzonite monzodiorite in ag and diorite in sg compositions and are more mafic with respect to their host rocks in the primitive mantle pm normalized trace element patterns host rock and mme samples have similar trace element patterns all of these rocks are enriched in large ion lithophile elements liles cs rb ba th k and sr and strongly depleted high field strength elements hfses ta nb p ti compared to the primitive mantle the isotope ratios of the syn extensional ag and sg rocks display increasing radiogenic strontium and decreasing radiogenic neodymium isotopic values for the ag and sg host rocks and mme samples are 87 sr 86 sr ag host 0 708835 0 710206 and e nd t ag host 5 36 to 7 36 87 sr 86 sr ag mme 0 709107 0 709801 and e nd t ag mme 5 36 to 7 36 87 sr 86 sr ag mme 0 709107 0 709801 and e nd t ag mme 5 55 to 6 51 87 sr 86 sr sg host 0 712200 0 712408 and e nd t sg host 8 03 to 8 61 87 sr 86 sr sg mme 0 712028 0 712351 and e nd t sg mme 7 57 to 8 48 syn extensional granitoids in western turkey were mainly affected by crustal contamination fractional crystallization and magma mixing mingling mm processes magma mixing mingling partial mixing appear to have larger affects on the compositional range of the magmas than those generated by partial melting crustal contamination and fractional crystallization mafic and felsic magmas forming syn extensional granitoids have also undergone metasomatism chemical equilibrium and diffusional exchange processes during cooling syn extensional granitoids have been derived from a hybrid magma that originated from mixing of coeval lower crustal derived felsic magma and lithospheric mantle derived mafic magmas during extensional processes

microstructural compositional and petrophysical properties of mylonitic granodiorites from an extensional shear zone rhodope core complex greece at the southern boundary of the rhodope massif ne greece the kavala shear zone ksz represents an example of the eastern mediterranean deep seated extensional tectonic setting during miocene time extensional deformation favoured syntectonic emplacement and subsequent exhumation of plutonic bodies this paper deals with the strain related changes in macroscopic geochemical and microstructural properties of the lithotypes collected along the ksz comprising granitoids from the pluton aplitic dykes and host rock gneisses moreover we investigated the evolution of seismic anisotropy on a suite of granitoid mylonites as a result of progressive strain isotropic compressional and shear wave velocities v p v s and densities calculated from modal proportions and single crystal elastic properties at given pressure temperature p t conditions are compared to respective experimental data including the directional dependence anisotropy of wave velocities compared to the calculated isotropic velocities which are similar for all of the investigated mylonites average values v p 5 87 km s 1 v s 3 4 km s 1 v p v s 1 73 and density 2 65 g cm 3 the seismic measurements give evidence for marked p wave velocity anisotropy up to 6 92 at 400 mpa in the most deformed rock due to marked microstructural changes with progressive strain as highlighted by the alignment of mica chlorite minerals and quartz ribbons the highest p and s wave velocities are parallel to the foliation plane and lowest normal to the foliation plane importantly v p remains constant within the foliation with progressive strain but decreases normal to foliation the potential of the observed seismic anisotropy of the ksz mylonites with respect to detectable seismic reflections is briefly discussed

lower crustal involvement in upper crustal thrusting summary basement structures mapped in the devonian adavale basin eastern australia indicate two styles of lower crustal involvement in the formation of upper crustal structures the first style is typified by thrust features in the upper crustal sedimentary section and basement a response to lower crustal shortening over a wide area the second style includes lower crustal thrusting and thickening in a limited region with associated uplift of the upper crust these two styles suggest that the upper and lower crust were mechanically decoupled during palaeozoic compressive episodes 1 tectonic structures in the upper crust basement involved thrust faults have been mapped in the southern adavale basin australia using both bureau of mineral resources and industry seismic data finlayson et al in press these faults were grouped into two sets those striking predominantly north south gumbardo and corona and those striking predominantly east west como paradise and grenfield and form an orthogonal network of faults in this region fig 1 mechanical considerations dictate that these orthogonal thrust sets did not form synchronously relative thinning of stratigraphic units over basement faults has been used to date uplift movement on these faults retrodeformed sections produced by restoring the mid devonian cooladdi dolomite unit or its lateral equivalent were used to date initiation of thrusting the sections show that the east west striking thrusts developed first during the lower devonian in response to north south crustal shortening the thrust faults were separated by tear faults which transferred the relative strain between the fault blocks dalhstrom 1970 the second phase of tectonic activity commenced in the late devonian and continued into the carboniferous this phase is interpreted to be due to east west crustal shortening and reversed the roles of the thrust and tear faults developed during the previous episode leven et al in press the north south striking gumbardo and corona faults were reactivated as thrusts while previous thrusts acted as transfer faults for this deformation during the latter portion of this second tectonic episode sediments of the adavale basin were deformed into large scale predominantly north south trending folds the folding style of this later deformation contrasts with the faulting associated with the earlier episode carboniferous erosion which veevers et al 1984 suggest was caused by an extensive ice sheet effectively removed most of the sediment of the newly formed adavale basin leaving only the remnant synclinal cores these are represented in the southern adavale basin region by the cooladdi quilpie and blackwater troughs the wavelength of this basin wide folding is about 100 km and the amplitude in the case of the cooladdi trough exceeds 8 km but diminishes towards the west the warrabin trough to

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

paleomagnetic evidence for cenozoic clockwise rotation of the external albanides abstract a paleomagnetic study of 750 samples obtained from 55 late eocene to middle pliocene sedimentary sites demonstrates a clockwise rotation of about 45 of the external zones of albania this rotation occurred either in two phases of roughly equal amplitude during the early middle miocene and plio pleistocene or in a single phase with a clear acceleration of the movement during the plio pleistocene the good agreement of these results with those from southern albania and northwestern greece indicates that a large geographical area is involved in the rotation the active aegean compressive front thus extends much farther north than hitherto believed and the rotational pattern is not significantly distorted by the tectonic discontinuities recorded by geological studies the external zones of the albano hellenic belt appear to have rotated virtually as a single entity from the peloponnesos to northern albania over a deep decollement level probably involving the basement itself

quaternary neotectonics of the south aegean arc abstract the sedimentary and tectonic quaternary evolution of the south aegean arc has been interpreted from 8000 line km of sparker seismic reflection profiles the older parts of basins formed by e w trending faults and accumulated hemipelagic sediment younger active faulting trends nnw in the western part of the arc and ene in the eastern arc the ene trending faults record sinistral strike slip motion broadly parallel to the convergence direction of the aegean anatolian and african plates the north south faults in the western arc are similar to those on land in the south peloponnese chronology is estimated from sedimentation rates in cores and from stacked progradational units on basin margins controlled by eustatic changes in sea level the younger fault pattern developed at 0 6 0 8 ma in the western and central arc but progressively younger in the southeastern part of the arc the older basin fill with e w faults is of early quaternary and pliocene age an older regional unconformity corresponds to an early pleistocene unconformity in the cretan basin particularly in the area east of santorini faulting has resulted in startling changes in palaeogeography such that some areas were late pliocene basins positive features during the pleistocene and then subsided 600 m in the last 0 2 ma such rapid basin inversion resulted in uplift of stratified hemipelagic muds which were deformed by creep or failure so that debris flow deposits accumulated in valleys and ponded basins these fundamental tectonic changes in the past two million years indicate that much of the deformation resulting from the interaction of the eurasian african and anatolian aegean plates is taken up at the southern margin of the aegean microplate probably because subduction of the african plate has slowed as a result of collision of continental crust regional fault patterns are a consequence of spatially varying effects of subduction roll back

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

active tectonics of the aegean region the aegean sea and its surrounding regions comprise one of the most rapidly deforming parts of the alpine himalayan mountain belt though the deformation of the belt as a whole is related to thc northward move ment of africa arabia and india relative to eurasia the tectonics of the aegean region itself is dominated by strike slip and extensional motions the actively deforming part of the aegean region is not large about 700 x 700 km2 compared with that in asia yet it has had an influence on our views of continental tectonics disproportionate to its size and comparable perhaps only to tibet fundamental contributions from the aegean have been made to many topics including