chemical influence on α recoil damage annealing in apatite implications for u th he dating article apatite u th he ahe ages reflect the influence of several parameters such as grain size thermal history and diffusion kinetics previous work has suggested that recoil damage produced by the u th decay chains can have a significant effect on he diffusion kinetics models taking into account damage production and annealing via a parameterization similar to that for apatite fission tracks aft have been proposed comple mentary to these models in this work we demonstrate that grain chemistry influences the annealing rate of diffusivity altering damage in the same manner as for aft and thus is not constant across all apatites the key parameter of the annealing law rmr0 is examined and its theoretical impact on ahe age is tested in cer tain situations the ahe age can be significantly affected by changes in the damage annealing rate for sam ples having undergone a long stay in the ahe partial retention zone 50 80 c ahe ages can diverge by more than 15 over a reasonable range of annealing rates in addition this hypothesis is tested on a geolog ical case well samples of triassic sandstones at 67 5 1 5 c at depth in the paris basin france aft data and ahe ages have been measured on detrital apatite in addition to chemical analysis of the grains dated for aft ages for both thermochronometers present similar histogram distributions with younger ages for ahe aft 14 208 ma n 117 ahe 4 76 ma and one grain at 120 ma n 36 the apatite grains are character ized by dpar values from 1 2 m to 2 9 m and cl content ranging from 0 05 to 0 9 wt using a thermal his tory reconstruction based on aft data and geological evidence it is shown that the non correlation observed between ahe age and eu content can be simply explained by changing the rmr0 value we conclude that to fully access the ahe age meaning in terms of temperature sensitivity the parameters of the annealing law stemming from the grain chemistry need to be considered

upper cretaceous exhumation of the western rhodope metamorphic province chalkidiki peninsula northern greece the vertiskos unit of northern greece is an elongated basement belt with a complex poly metamorphic history it extends from greece chalkidiki peninsula to the south up to serbia in the north and arguably represents the westernmost part of the rhodope metamorphic province northern greece to southern bulgaria the vertiskos unit experienced a medium pressure lower amphibolite facies metamorphic overprint during the alpine orogeny the available medium temperature geochronology implies that it remained at temperature of approximately 300 c or slightly higher during lower cretaceous in order to constrain its post lower cretaceous thermal history until near surface exposure we applied apatite fission track analysis the central ages obtained range from 68 5 3 8 to 46 6 3 6 ma uppermost cretaceous to middle eocene and mean track lengths between 13 and 13 5 m we applied two inverse thermal modeling approaches using either each sample independently high degree of freedomin the thermal history better data fit or all samples together interpreting them as a vertical profile simpler thermal history worse data fit irrespective of the modeling approach we conclude that the bulk thermal history of the vertiskos unit crosses the high temperature limit of the apatite partial annealing zone by the uppermost cretaceous and reaches near surface conditions as early as lower middle eocene these results contrast with the thermal history of the other domains of the rhodope metamorphic province further east namely the southern rhodope core complex and the northern rhodope complex and establish the vertiskos basement complex as the oldest exhumed coherent basement fragment of the rhodope metamorphic province and greece

the summit erosion surfaces of the inner betic cordillera their value as tools for reconstructing the chronology of topographic growth in southern spain erosion surfaces at the top of mountain ranges have suggested to geomorphologists that the earth s crust can undergo rapid pulses of uplift during which rates of denudation fail to balance with rates of crustal uplift thereby preserving much of the initial plateau topography as it rises to greater elevations here we analyze a regionally extensive population of mappable planar surfaces which crown several major tectonically active sierras of the inner south eastern betic cordillera se spain based on a synthesis of long term landscape evolution involving landform reconnaissance dem based morphometric analysis structural geology sediment provenance analysis and field stratigraphy we conclude that the summit surfaces are a mosaic of discrete post orogenic erosion surfaces that each developed in relation to mediterranean marine base levels at a time when the sierras formed a series of low elevation islands they are not therefore fragments of a once regionally continuous paleoplain the summit surfaces were partly the result of shallow angle detachment faulting during the middle miocene in response to lithospheric slab detachment where evidence exists that the resulting low relief topography was reworked by marine abrasion during the tortonian sea level rise the terminal age of the surfaces is latest miocene age bracketing based on stratigraphic correlations among the many depocentres of the region and on published thermochronological data indicates that some erosion surfaces locally formed in less than 3 million years 8 ma 5 7 ma they were subsequently uplifted to their current elevations 1 7 to 2 km by pliocene to quaternary neotectonics in at least two major pulses

the thrace basin in the rhodope province of ne greece a tertiary supradetachment basin and its geodynamic implications abstract detailed tectonic analysis and geological mapping on the tertiary molassic and volcanosedimentary rocks of the thrace basin in northeastern greece allowed us to reconstruct the structural evolution of the basin and its geotectonic setting as well as the orientation of the regional paleostress field sedimentation was linked with a calc alkaline and locally shoshonitic magmatism associated with the tertiary syn to late orogenic extension in the rhodope province we interpret the molassic tertiary greek part of the thrace basin as a supradetachment basin associated with sedimentary and volcanic infilling five 5 deformational events t1 to t5 have been distinguished during basin evolution from eocene to quaternary time t1 is related to a low angle normal detachment fault zone with a top to the sw to ssw sense of movement and initial basin subsidence during middle late eocene to oligocene time simultaneously with uplift and exhumation of the footwall rhodope metamorphic rocks stacking and crustal thickening in the more external parts of the hellenic orogenic belt have taken place during the same time t2 evolved during oligocene miocene time it was characterized by transpressional tectonics and formation of large strike slip faults and extensional fractures as well as conjugate thrust faults and folds with n nw or s se sense of movement during miocene pliocene time the third t3 event took place it was responsible for the high angle normal faults dismembering the eocene oligocene molassic basin into neogene grabens the t4 event affected the neogene sediments of the basin with minor reverse strike slip faults as well as normal faults the following t5 event is related to large normal active faults they coincided with the active tectonics of the study area defined by the earthquake focal mechanisms

neotectonics of the central parts of the balkan peninsula basic features and concepts the neotectonic movements on the balkan peninsula occurred after the last intense thrusting early miocene and after the early middle miocene planation they were controlled by extensional collapse of the late alpine orogen and by extension behind the aegean arc and were influenced by the complicated vertical and horizontal movements in the pannonian region the stara planina and dinarian hellenic linear neotectonic morphostructures inherited the alpine orogenic zones balkanides and dinarides hellenides and bounded the central balkan neotectonic region the linear morphostructures were tilted towards the pannonian and euxinian basins and the north aegean trough the central balkan neotectonic region has a complicated block structure horst and graben pattern dominated by the nnw sse struma and vardar lineaments the wnw ese sava and marica lineaments and the middle mesta and north anatolian fault zones the dominating serbo macedonian neotectonic swell was rifted and subsided along the struma and vardar lineaments the range of the vertical neotectonic displacements reached a maximum of 3 4 km and even up to 6 km at the edges of the pannonian and aegean basins the general doming of the region was controlled by the isostatic uplift of a thickened crustal lens rhodope massif in the southern margin of the eurasian plate the collapse of the complicated domal structure began along the main struma vardar and marica lineaments in the central parts of the dome and continued in the pliocene and quaternary along a more external contour bounded by the stara planina and dinarian hellenic linear morphostructures

mesozoic tertiary structural evolution of an extensional gneiss dome the kesebir kardamos dome eastern rhodope bulgaria greece the tectonic evolution of the rhodope massif involves mid cretaceous contractional deformation and protracted oligocene and miocene extension we present structural kinematic and strain data on the kesebir kardamos dome in eastern rhodope which document early tertiary extension the dome consists of three superposed crustal units bounded by a low angle nne dipping detachment on its northern flank in bulgaria the detachment separates footwall gneiss and migmatite in a lower unit from intermediate metamorphic and overlying upper sedimentary units in the hanging wall the high grade metamorphic rocks of the footwall have recorded isothermal decompression direct juxtaposition of the sedimentary unit onto footwall rocks is due to local extensional omission of the intermediate unit structural analysis and deformational metamorphic relationships give evidence for several events the earliest event corresponds to top to the sse ductile shearing within the intermediate unit interpreted as reflecting mid late cretaceous crustal thickening and nappe stacking late cretaceous palaeocene eocene late tectonic to post tectonic granitoids that intruded into the intermediate unit between 70 and 53 ma constrain at least pre latest late cretaceous age for the crustal stacking event subsequent extension related deformation caused pervasive mylonitisation of the footwall with top to the nne ductile then brittle shear ductile flow was dominated by non coaxial deformation indicated by quartz c axis fabrics but was nearly coaxial in the dome core latest events relate to brittle faulting that accommodated extension at shallow crustal levels on high angle normal faults and additional movement along strike slip faults radiometric and stratigraphic constraints bracket the ductile then brittle extensional events at the kesebir kardamos dome between 55 and 35 ma extension began in paleocene early eocene time and displacement on the detachment led to unroofing of the intermediate unit which supplied material for the syn detachment deposits in supra detachment basin subsequent cooling and exhumation of the footwall unit from beneath the detachment occurred between 42 and 37 ma as indicated by mica cooling ages in footwall rocks and extension proceeded at brittle levels with high angle faulting constrained at 35 ma by the age of hydrothermal adularia crystallized in open spaces created along the faults this was followed by late eocene oligocene post detachment overlap successions and volcanic activity crustal extension described herein is contemporaneous with the closure of the vardar ocean to the southwest it has accommodated an earlier hinterland directed unroofing of the rhodope nappe complex and may be pre cursor of and or make a transition to the aegean back arc extension that further contributed to its exhumation during the late miocene this study underlines the importance of crustal extension at the scale of the rhodope massif in particular in the eastern rhodope region as it recognizes an early tertiary extension that should be considered in future tectonic models of the rhodope and north aegean regions

paleostress analysis of cenozoic faulting in the kraishte area sw bulgaria abstract paleostress calculations from fault planes in paleogene sediments and in the underlying basement were used to determine the orientation and the chronology of the principal stresses during the cenozoic tectonic evolution of the kraishte area southwest bulgaria the results show that middle eocene early oligocene wsw ene extension led to the formation of grabens and half grabens filled with thick continental to marine deposits in the hanging wall of extensional detachments the paleogene sediments and their basement were then intruded by subvolcanic bodies and dykes during sw ne extension between 32 and 29 ma these wsw ene and sw ne extensional stages are related to the general rollback of the hellenic slab from the late oligocene to the earliest miocene sse nnw transtension generated coal bearing sedimentary basins the anticlockwise rotation of the main tensile axis by almost 50 with respect to the previous tectonic stage was probably related to a switch from the aegean back arc extension to crustal stretching and extrusion of continental fragments around the moesian platform since the middle miocene extension in the kraishte area accommodated by faults with relatively small displacement led to the formation of restricted basins filled with alluvial to lacustrine deposits

cenozoic landforms and post orogenic landscape evolution of the balkanide orogen evidence for alternatives to the tectonic denudation narrative in southern bulgaria continental denudation is the mass transfer of rock fromsource areas to sedimentary depocentres and is typically the result of earth surface processes however a process known as tectonic denudation is also understood to expose deep seated rocks in short periods of geological timeby displacing largemasses of continental crust along shallow angle faults and without requiring major contributions from surface erosion some parts of the world such as the basin and range in theusa or the aegean province in europe have been showcased for their cenozoic tectonic denudation features commonly described as metamorphic core complexes or as supradetachment faults based on 22 new apatite fission track aft and 21 helium ahe cooling ages among rock samples collectedwidely from plateau summits and their adjacent valley floors and elaborating on inconsistencies between the regional stratigraphic topographic and denudational records this study frames a revised perspective on the prevailing tectonic denudation narrative for southern bulgaria we conclude that conspicuous landforms in this region such as erosion surfaces on basement cored mountain ranges are not primarily the result of paleogene to neogene core complex formation they result instead from ordinary erosion driven subaerial denudation rock cooling each time suggesting at least 2 km of crustal denudation has exposed shallow paleogene granitic plutons and documents a 3 stage wave of erosional denudation which progressed from north to south during themiddle eocene oligocene early tomiddlemiocene and late miocene denudation initially prevailed during the paleogene under a syn orogenic compressional regime involving piggyback extensional basins phase 1 but subsequently migrated southward in response to post orogenic upper plate extension driven by trench rollback of the hellenic subduction slab phase 2 rare insight given by the denudation pattern indicates that trench rollback progressed at amean velocity of 3 to 4 km ma the neogene horst and grabenmosaic that defines the modern landscape phase 3 has completely overprinted the earlier fabrics of phases 1 and 2 and has been the prime focus of tectonic geomorphologists working in the region the new narrative proposed here for linking the geodynamic evolution of se europe with surface landform assemblages raises issues in favour of better documenting the regional sedimentary record of existing paleogene basins which constitute a poorly documented missing link to the thermochronological evidence presented here

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

apatite fission track analysis apatite fission track aft analysis has been widely used during the past 30 years to constrain the low temperature thermal histories of many igneous metamorphic and sedimentary rocks in a wide range of geological settings applicable geological settings include orogenic belts rifted margins faults sedimentary basins cratons and mineral deposits the types of geologic problems that can be addressed include the timing and rates of tectonic events sedimentary basin evolution the timing of hydrocarbon generation and ore mineralization the absolute age of volcanic deposits the effects of major climatic changes on the near surface geothermal gradient and long term landscape evolution early work by naeser 1967 and wagner 1968 1969 first established the basic procedures that enabled the fission track dating method to be applied routinely to these geologic problems fleischer et al 1975 summarized the early studies of the broader discipline of nuclear track detection in different solid state materials more recent comprehensive overviews of fission track applications have been provided by naeser and mcculloh 1989 wagner and van den haute 1992 gallagher et al 1998 van den haute and de corte 1998 dumitru 2000 and gleadow et al 2002 etched natural fission tracks in several apatite grains are shown in figure 1 successful aft analysis is limited by the following 1 the availability of apatite from which useful aft data can be obtained often due to a lack of apatite of sufficient grain size and quality within available rock types or alternatively the lack of available rock samples due to minimal outcrop exposure or other reasons 2 economic considerations in terms of the time and money required to obtain sufficient aft data 3 the inherent limitations of aft data to resolve geological thermal history information often related to limited numbers of accumulated spontaneous fission tracks due to

late cenozoic development of the strouma and mesta fluviolacustrine systems sw bulgaria and northern greece abstract the strouma and mesta are two of the largest rivers that drain across sw bulgaria and northern greece into the northern aegean sea their modern valleys flanked by quaternary river terraces are incised into a diverse landscape which records the region s complex tectonic history a network of lacustrine basins existed in the region in the late oligocene to earliest miocene but was disrupted by thrusting and folding related to early miocene transpression this deformation was followed by a period of erosion covering most of the early and middle miocene which probably marked the initiation of the strouma and mesta fluviolacustrine system with geometries unrelated to the older systems the first clear evidence of these river systems dates from the middle miocene late badenian to sarmatian the systems evolved in the late miocene maeotian to early pontian when lakes existed characterized by diatomaceous algae and by occasional burial of abundant plant fragments and coal formation areas in the south south of the kerkini fault were intermittently submerged beneath the aegean sea at this time intense localized uplift of horst blocks in late pontian and pliocene associated with crustal extension resulted in deposition of thick alluvial fans with tilting of sedimentary successions in adjacent grabens evident by the end of the pliocene the highest horsts osogovo rila pirin and belasitsa experienced additional uplift in the pleistocene in part as a result of regional uplift and in part through continued normal faulting pleistocene climate change also resulted in influxes of glacial and fluvioglacial systems the present form of the strouma and mesta fluviolacustrine systems is thus the result of interplay between crustal extension regional uplift and global climate change

is apatite u th zonation information necessary for accurate interpretation of apatite u th he thermochronometry data abstract new u th and ce concentration maps were acquired by la icpms for 70 apatites from 18 cratonic basement samples from the canadian shield to characterize the nature and variability in apatite u th zonation all apatites are zoned in effective u concentration eu with 80 exhibiting modest zoning that varies from a factor of 1 2 to 2 4 zonation patterns include those with a general eu decrease from core to rim 25 a core to rim eu increase 35 and patchy or irregularly shaped eu distributions 40 most samples consist of individual apatites with markedly different and opposing eu profiles cathodoluminescence cl images were obtained for 258 apatites in 25 samples comparison of eu and cl patterns reveals no consistent relationships suggesting that cl is not a reliable proxy for apatite eu zonation we explore the implications of eu zonation for the interpretation of apatite u th he ahe data by comparing the age predictions for representative and endmember apatite eu profiles with those for unzoned apatites we focus on thermal histories that should magnify eu zonation effects including slow monotonic cooling extended he partial retention zone heprz residence and protracted reheating and cooling application of incorrect ejection correction f t factors different he concentration gradients and variable intracrystalline retentivity due to heterogeneous radiation damage may cause the ahe dates for zoned and unzoned apatites to differ in our dataset the magnitude of the f t effect is by simulating zoned apatite suites from representative and endmember samples we find that eu zoning adds modest age dispersion to most samples the commonly opposing eu profiles for individual apatites in most samples have different effects on the predicted age and partially cancel each other out to reduce the predicted age difference at the sample level higher predicted age differences between zoned and unzoned samples generally correlate with greater sample scatter the age deviations generally fall within the 15 uncertainty range that we commonly apply for sample ahe dates except in unusual circumstances it appears unlikely that the unzoned apatite assumption will lead to misinterpretation of ahe datasets thus precluding the need to routinely acquire apatite eu zonation information as part of ahe dating studies

separate eocene early oligocene and miocene stages of extension and core complex formation in the western rhodopes mesta basin and pirin mountains bulgaria abstract the rhodope metamorphic province in bulgaria and northern greece has been affected by significant extensional tectonics since the middle to late eocene an important fault system active in the eocene and early oligocene includes the ribnovo fault on the eastern side of the mesta basin in bulgaria and the vertiskos kerdilion fault in greece together with several minor normal fault relicts identified during this study these represent an originally west southwest dipping low angle at least at the end of faulting normal fault with greenschist facies mylonites in the footwall and cataclasites along the fault plane the mesta kerdilion detachment exposed over ca 150 km along strike and about 50 km parallel to the slip direction during the intrusion of several plutons in the pirin mountains at ca 32 ma the footwall of the fault was uplifted to form a large anticline parallel to fault strike and the fault was offset by a system of antithetic northeast dipping normal faults along the northeastern flank of this anticline dobrotino and breznitsa faults the mesta kerdilion detachment was later in the miocene again crosscut and offset by the southwest dipping strimon valley detachment which accommodated important core complex like exhumation to the south strongly diminishing and finally ceasing towards north this rotational activity of the strimon valley detachment represents the onset of the extension that led to opening of the aegean basin the mesta kerdilion detachment can be viewed as a precursor of this but with slightly different kinematics i e not involving significant vertical axis rotation and separated in time from the following events by a phase of relative tectonic quiescence in the late oligocene

calcareous nannofossil biostratigraphy and magnetostratigraphy of the upper miocene and lower pliocene of the northern aegean orphanic gulf strimon basin areas greece abstract the transitional position of the northern aegean makes it an important area for studying the relation between the mediterranean and the eastern paratethys a chronostratigraphic framework has been obtained for the late neogene deposits along the orphanic gulf and in the strimon basin of northern greece by analysing calcareous nannofossil data and paleomagnetic results from eight sections the local formations and major lithological units have been correlated with the upper miocene and lower pliocene stages furthermore the obtained framework has facilitated a more detailed reconstruction of the effects of the messinian salinity crisis on the sedimentary record magnetostratigraphic data from the strimon basin result in an age estimate of 6 3 ma for the dafni choumnikon formation transition between normal polarity subchrons c3an 2n and c3an 1n since this late miocene age estimate corresponds closely to estimates of the maeotian pontian boundary in the eastern paratethys dacic basin we believe this transition from marine to brackish conditions corresponds to this latter boundary the gypsiferous unit in the basal part of the choumnikon equivalent beds along the orphanic gulf can then be correlated with the evaporites in the northern aegean and the lower evaporites of the mediterranean basin consequently we assume that these northern aegean evaporites have been deposited between 5 96 and 5 59 ma freshwater deposits above the evaporites are easily traceable across the orphanic gulf area as a gravel or sandstone unit topped by a travertine marker bed and have a wide lateral continuation since their position is intermediate between the shallow marine gypsum anhydrite and the more open marine clastics of the pliocene we argue that these beds correlate with the desiccation phase of the mediterranean and black sea basins this intra messinian event probably occurred between 5 59 and 5 50 ma thus predating the upper evaporites or lago mare of the mediterranean a clear recognition of the miocene pliocene boundary remains problematic in the orphanic gulf area nannofossil assemblages in the sections suggest a higher position of the local base of the pliocene than indicated by the level with the first appearance of planktonic and benthic foraminifera discontinuous occurrences of levels containing nannofossil assemblages of zone mnn11b c are found between the travertine unit and the lowermost pliocene beds representing brief marine ingressions the latter show that in the latest messinian presumably temporary connections of atlantic mediterranean waters with the northern aegean basin existed these marine ingressions likely extended further into the eastern paratethys as demonstrated by the presence of nannofossil assemblages in the middle and upper pontian of the dacic and euxinic basins the events around the miocene pliocene transition resulted in a fairly abrupt change from brackish to open marine conditions in a relative deep basin which was subject to increased rates of subsidence from the onset of evaporite deposition in the late messinian onward

late proterozoic and silurian basement units within the serbo macedonian massif northern greece the significance of terrane accretion in the hellenides

brittle deformation palaeostress field reconstruction and tectonic evolution of the eastern balkanides bulgaria during mesozoic and cenozoic times

bridging onshore and offshore present day kinematics of central and eastern mediterranean implications for crustal dynamics and mantle flow we present a new kinematic and strain model of an area encompassing the calabrian and hellenic subduction zones western anatolia and the balkans using haines and holt s 1993 method we derive continuous velocity and strain rate fields by interpolating geodetic velocities including recent gps data in the balkans relative motion between stable eurasia and the western aegean sea is gradually accommodated by distributed n s extension from southern balkans to the eastern corinth gulf so that the westward propagation of the north anatolian fault naf throughout continental greece or peloponnesus is not required we thus propose that the naf terminates in north aegean and that n s extension localized in the corinth gulf and distributed in southern balkans is due to the retreat of the hellenic slab the motion of the hyblean plateau apulia peninsula south adriatic sea ionian basin and sirte plain can be minimized by a single rigid rotation around a pole located in the sirte plain compatible with the opening the pelagian rifts 2 2 5 mm yr and seismotectonics in libya we interpret the trenchward ultraslow motion of the calabrian arc 2 2 5 mm yr as pure collapse the calabrian subduction being now inactive in the absolute plate motion reference frame our modeled velocity field depicts two toroidal crustal patterns located at both ends of the hellenic subduction zone clockwise in nw greece and counter clockwise in western anatolia we suggest the nw greece toroidal pattern is the surface expression of a slab tear and consequent toroidal asthenospheric flow

trace fossils and the aftermath of the permo triassic mass extinction evidence from northern italy abstract the duration of early triassic anoxia in the carbonate ramp settings of the werfen formation dolomites northern italy has been constrained using ichnofabric and sedimentological data this includes fine lamination and abundant pyrite framboids commonly reworked into lags by storm events the anoxic event spanned the entire griesbachian stage and extended from deep waters into extraordinarily shallow water settings evidence for oxygen deficiency can be found in mid and inner ramp facies the extent and duration of this event may at least partially explain the magnitude of the permo triassic mass extinction normal benthic conditions returned rapidly in the dienerian stage and pervasively bioturbated distal ramp facies testify to the ventilation of the deeper water areas of the region in post griesbachian times a post mass extinction radiation is not particularly well displayed in either trace fossil or body fossil diversity compilations from the dolomites moderate low levels of trace fossil diversity are maintained throughout the post griesbachian werfen formation whilst the body fossil data shows a moderate increase from the mid smithian stage there is thus a curious lag period spanning the dienerian to mid smithian when environmental conditions were apparently normal but the marine fauna failed to show any recovery

accounting for long alpha particle stopping distances in u th sm he geochronology 3d modeling of diffusion zoning implantation and abrasion in apatite u th he thermochronology the helium distribution in a crystal is a function of the simultaneous processes of radiogenic production thermally activated volume diffusion and the ejection of he caused by long alpha stopping distances these processes are further complicated by zonation of u th and sm within the grain and implantation of 4he from neighboring u th sm bearing minerals we use a refined version of the 3d monte carlo diffusion code of gautheron and tassan got 2010 to simulate the interplay between ejection and diffusion with or without zonation ejection and abrasion for a suite of thermal histories we examine the phenomenon of over correction produced by the alpha ejection correction parameter ft or fzac for homogeneous or heterogeneous eu repartition by comparing the raw measured and ft or fzac corrected ages for a number of scenarios to the ejection free age aef which we define as the age that would be obtained if alpha ejection had not occurred or equivalently if the stopping distance was zero we show that the use of ft or fzac corrected ages generally reproduces the ejection free age to within typical u th he uncertainties 8 even for zoned apatites we then quantify the effect of alpha implantation on u th he ages showing that implantation from a single external source with modest relative u or th enrichment can generate as much as 50 excess he for more extreme cases where an apatite is surrounded by multiple external sources the measured age can be 300 of that determined from an isolated crystal while abrasion of the outer 20 25 m can significantly reduce the age dispersion for rapidly cooled samples slowly cooled samples can still retain 10 30 excess he the removal of the rim of the crystal reduces the thermal information from very low temperatures 40 c and introduces additional technical complications and biases and should therefore be used with caution overall we demonstrate that although zonation and implantation may not be routinely determined we now have the 3d modeling capability to fully investigate and constrain the causes of age dispersion within a sample leading to significant improvement in our ability to interpret u th he data

westward propagation of the north anatolian fault into the northern aegean timing and kinematics we present new evidence for the propagation processes of the north anatolian fault folding in the dardanelles straits region allows us to document the timing of the deformation preceding and the finite displacement after the passage of the propagating tip of the fault the accuracy of the observations is due to interplay between deformation and the sea level changes in the mediterranean the well known messinian regression followed by the pliocene transgression the long term kinematics around the sea of marmara pull apart total displacement of about 85 km over the past 5 m y is similar to the present day kinematics deduced from space geodesy at a larger scale westward propagation of the north anatolian fault over nearly 2000 km in the past 10 m y appears to be associated with strain recovery suggesting that the continental lithosphere retains long term elasticity

geochronological and structural constraints on the cretaceous thermotectonic evolution of the kraishte zone western bulgaria 1 in the kraishte region near the junction of the balkanides and dinarides late early cretaceous compression led to the thrusting of the morava unit over the struma unit structural investigations combined with zircon fission track and 40ar 39ar analyses have been used to reconstruct the geological history of the area and to clarify the original tectonic position of the main units before cenozoic extension the results show that early cretaceous lower amphibolite facies metamorphism and deformation in the osogovo lisets metamorphic complex were related to top to the ne directed nappe stacking whereas the deeper parts of the allochthonous morava unit experienced low grade metamorphic overprint at temperatures 260 c the structurally intermediate struma diorites and their mesozoic cover experienced temperatures between 170 c and 300 c thrusting of the morava onto the struma unit started probably in valanginian times 140 136 ma soon after the cessation of preorogenic to synorogenic turbidite sedimentation on struma the metamorphic peak was reached before 112 ma subsequent extension related cooling of both units was probably accompanied by the formation of low angle normal faults

evidence from the mesta half graben sw bulgaria for the late eocene beginning of aegean extension in the central balkan peninsula abstract the ene tilted mesta half graben contains a 3 km thick section of priabonian late eocene to oligocene sedimentary and volcanic rocks that rest unconformably on basement metamorphic rocks along its west side basal strata dip 50 60 e and dip at progressively lower angles upward indicating synrotational deposition the southern part of the half graben contains nested volcanic caldera complexes formed during the deposition of the middle part of the sedimentary sequence which have been rotated by about half the total rotation of the sedimentary succession the half graben is bounded on the east by a fault that steepens from more deeply exposed structural levels in the south 8 18 w to shallower exposed structural levels in the north 70 w and together with the rotation of paleogene strata during deposition indicate the mesta half graben is underlain by a listric detachment fault the mesta detachment subhorizontal middle miocene strata that unconformably overlie tilted paleogene strata yield an upper age limit to the extension west and northwest of the mesta half graben are many other nnw trending ne tilted paleogene half grabens which we suggest are part of an important extended area in sw bulgaria and eastern macedonia that lies above one or more west dipping detachment faults and date the beginning of aegean extension in the southern balkan region as at least as old as priabonian the mesta detachment is oblique to the trend of a contemporaneous paleogene magmatic arc in the southern balkans and the origin of the detachment is probably related to gravitationally induced spreading of thickened hot arc crust and hellenic trench roll back

asymmetric slip partitioning in the sea of marmara pull apart a clue to propagation processes of the north anatolian fault between 1939 and 1999 the north anatolian fault naf experienced a westward progression of eight large earthquakes over 800 km of its morphological trace the 2000 km long north anatolian transform fault has also grown by westward propagation through continental lithosphere over a much longer timescale 10 myr the sea of marmara is a large pull apart that appears to have been a geometrical mechanical obstacle encountered by the naf during its propagation the present paper focuses on new high resolution data on the submarine fault system that forms a smaller pull apart beneath the northern sea of marmara between two well known strike slip faults on land izmit and ganos faults the outstandingly clear submarine morphology reveals a segmented fault system including pull apart features at a range of scales which indicate a dominant transtensional tectonic regime there is no evidence for a single continuous purely strike slip fault this result is critical to understanding of the seismic behaviour of this region of the naf close to istanbul additionally morphological and geological evidence is found for a stable kinematics consistent both with the long term displacement field determined for the past 5 myr and with present day anatolia eurasia motion determined with gps however within the sea of marmara region the fault kinematics involves asymmetric slip partitioning that appears to have extended throughout the evolution of the pull apart the loading associated with the westward propagation process of the naf may have provided a favourable initial geometry for such a slip separation

cooling history of the nw himalaya pakistan fission track and 40ar 39ar cooling ages indicate that the late tertiary cooling history of the himalayan ranges of northern pakistan is largely a function of uplift and erosion interpretation of cooling ages which range from under 0 5 ma to over 80 ma suggests that during the late tertiary long term uplift rates at least doubled from under 0 2 mm yr to in some cases well over 0 5 mm yr uplift rates show strong and systematic regional variations as well which reflect the greater uplift of eastern and northern regions the association of very rapid uplift and erosion with the nanga parbat haramosh massif can be explained by a locally vigorous collision of india with eurasia near a promontory of indian crust the resultant rapid uplift of the nanga parbat haramosh massif reactivated the main mantle thrust melange zone with a reversed sense of motion discontinuities in the coolingage distribution along the main mantle thrust in the southern swat hazara region may be the result of the thermal effects of overthrusting

natural age dispersion arising from the analysis of broken crystals part i theoretical basis and implications for the apatite u th he thermochronometer abstract over the last decade major progress has been made in developing both the theoretical and practical aspects of apatite u th he thermochronometry and it is now standard practice and generally seen as best practice to analyse single grain aliquots these individual prismatic crystals are often broken and are fragments of larger crystals that have broken during mineral separation along the weak basal cleavage in apatite this is clearly indicated by the common occurrence of only 1 or no clear crystal terminations present on separated apatite grains and evidence of freshly broken ends when grains are viewed using a scanning electron microscope this matters because if the 4 he distribution within the whole grain is not homogeneous because of partial loss due to thermal diffusion for example then the fragments will all yield ages different from each other and from the whole grain age here we use a numerical model with a finite cylinder geometry to approximate 4 he ingrowth and thermal diffusion within hexagonal prismatic apatite crystals this is used to quantify the amount and patterns of inherent natural age dispersion that arises from analysing broken crystals a series of systematic numerical experiments were conducted to explore and quantify the pattern and behaviour of this source of dispersion using a set of 5 simple thermal histories that represent a range of plausible geological scenarios in addition some more complex numerical experiments were run to investigate the pattern and behaviour of grain dispersion seen in several real data sets the results indicate that natural dispersion of a set of single fragment ages defined as the range divided by the mean arising from fragmentation alone varies from c 7 even for rapid c 10 c ma monotonic cooling to over 50 for protracted complex histories that cause significant diffusional loss of 4 he the magnitude of dispersion arising from fragmentation scales with the grain cylindrical radius and is of a similar magnitude to dispersion expected from differences in absolute grain size alone spherical equivalent radii of 40 150 m this source of dispersion is significant compared with typical analytical uncertainties on individual grain analyses c 6 and standard deviations on multiple grain analyses from a single sample c 10 20 where there is a significant difference in the u and th concentration of individual grains eu the effect of radiation damage accumulation on 4 he diffusivity assessed using the rdaam model of flowers et al 2009 is the primary cause of dispersion for samples that have experienced a protracted thermal history and can cause dispersion in excess of 100 for realistic ranges of eu concentration i e 5 100 ppm expected natural dispersion arising from the combined effects of reasonable variations in grain size radii 40 125 m eu concentration 5 150 ppm and fragmentation would typically exceed 100 for complex thermal histories in addition to adding a significant component of natural dispersion to analyses the effect of fragmentation also acts to decouple and corrupt expected correlations between grain ages and absolute grain size and to a lesser extent between grain age and effective uranium concentration eu considering fragmentation explicitly as a source of dispersion and analysing how the different sources of natural dispersion all interact with each other provides a quantitative framework for understanding patterns of dispersion that otherwise appear chaotic an important outcome of these numerical experiments is that they demonstrate that the pattern of age dispersion arising from fragmentation mimics the pattern of 4 he distribution within the whole grains thus providing an important source of information about the thermal history of the sample we suggest that if the primary focus of a study is to extract the thermal history information from u th he analyses then sampling and analytical strategies should aim to maximise the natural dispersion of grain ages not minimise it and should aim to analyse circa 20 30 grains from each sample the key observations and conclusions drawn here are directly applicable to other thermochronometers such as the apatite rutile and titanite u pb systems where the diffusion domain is approximated by the physical grain size

rare destructive earthquakes in europe the 1904 bulgaria event case abstract seismic hazard is difficult to assess in regions of low strain rates a major limitation often relates to the absence of large instrumentally recorded events precluding any comparison between seismological data and paleoseismic or morphotectonic informations we take advantage of the 1904 m s 7 1 earthquake that struck the southern edge of stable eurasia and investigate if morphotectonic and paleoseismic observations can provide a reliable estimate of the seismic potential of slow slipping faults we have conducted a paleoseismic study of the krupnik normal fault thought to be responsible for the event a section of the fault bearing remnants of a 2 m high scarp has been selected at the base of triangular facets the trenching site locates where the scarp cuts across colluviums washed from the bedrock facetted slopes we excavated two neighbouring trenches one across a well preserved portion of the scarp and one across a portion degraded by a landslide the excavations reveal a set of coarse colluvial units faulted against bedrock and affected by secondary fissures faulting appears to have resulted from a single event with normal throw greater than 1 3 m that occurred before the emplacement of the landslide accelerator mass spectrometry ams radiocarbon dates of charcoal samples are consistent with the interpretation that the krupnik fault slipped recently most probably in 1904 after a long lasting 10 ka period of quiescence the morphotectonic and paleoseismic observations yield seismic moment estimates compatible with the instrumental magnitude of the event and indicate that destructive and infrequent earthquakes typify the regional seismic behaviour

transtensional origin of the ne sw simitli basin along the strouma strymon lineament sw bulgaria several depocentres have developed along the nnw sse striking strouma strymon lineament since the miocene forming the strouma strymon graben system some of these basins including the dzherman and simitli strike at high angles to the lineament the rhomboid shaped simitli basin is limited in the south by the ne sw striking seismically active kroupnik fault and contains terrestrial clastic sediments which have been deposited since the sarmatian its formation is attributed to wrench dominated transtension d b event which activated the basin9s ne sw striking boundary faults as left lateral strike slip structures during the early middle miocene this deformation was associated with nne ssw contraction and wnw ese extension and succeeded the nne ssw contraction caused by pure shear dominated transpression d a event which governed the region in late oligocene early miocene times during the middle late miocene the d b event was followed by wnw ese pure shear dominated extension d 1 event which caused further widening of the basin the transtensional origin of the simitli basin is explained by lateral extrusion of the crustal mass squeezed between the apulian adriatic microplate and the european foreland towards the north aegean sea the subduction retreat of the hellenic orogen possibly enhanced this lateral extrusion and from the late miocene onwards the ne sw oriented back arc extension balanced the continuing retreat

formation of south facing bald mudstone slopes in southwestern taiwan abstract in the southwestern part of taiwan most foothills are covered by mudstones the mudstone formed during miocene to pliocene and pleistocene is a young and weak sedimentary rock when subjected to water slaking of the mudstone can easily take place and in dry seasons severe shrinkage can occur thus erosion of mudstone slopes is easily induced by rainfalls heavily eroded natural mudstone slopes in southwestern taiwan frequently become bald i e not covered by any plants or bushes and are very susceptible to geologic damages such as mudflow and slope failure one interesting observation of the mudstone slopes in southwestern taiwan is that most of the bald slopes are south facing the causes of this directional variation are thoroughly examined in this paper it is concluded that solar radiation rather than the direction of typhoons is the main reason for forming bald slopes in the south facing direction

marine gateway vs fluvial stream within the balkans from 6 to 5 ma since the discovery of calcareous nannofossils dinoflagellate cysts and planktonic foraminifers in deposits from the dacic basin intensive research has been performed in order to evidence which gateway this microplankton used to connect paratethys and the mediterranean prior and after the messinian salinity crisis msc such a gateway is also to be regarded at the origin of successive influxes of paratethyan organisms molluscs ostracods dinoflagellates into the mediterranean basin lago mare events observing that the i stanbul area usually proposed for this purpose was inefficient we examine the succession of marine well dated pre msc and post msc deltaic deposits through the balkans from northern greece to southern romania that constitutes a reliable candidate for such a marine corridor the origin of which was caused by the regional tectonic extension the reconstructed palaeogeography for high sea level episodes that encompassed the msc clarifies the context of the so called north aegean lake this marine gateway probably evolved as a powerful river during the peak of the msc contributing to the deposition of clastics in the hydrocarbon prinos field a tectonically controlled subsidence to the north and south of the skopje region caused the closure of such a gateway

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

no significant post eocene rotation of the moesian platform and rhodope bulgaria implications for the kinematic evolution of the carpathian and aegean arcs abstract the region located between the carpathian balkan and aegean arcs the moesian platform and bulgarian rhodope is generally assumed to have been stably attached to the east european craton during the cenozoic evolution of these arcs the kinematic evolution of this region is however poorly constrained by paleomagnetic analysis in this paper we provide new paleomagnetic data 800 volcanic and sedimentary samples from 12 localities showing no significant post eocene rotation of the moesian platform and rhodope with respect to eurasia therefore confirming the stability of this region we compare this result to a provided review of paleomagnetic data from the south carpathians tisza block and the aegean region the tisza block underwent 68 4 16 7 of middle miocene 15 10 ma clockwise rotation with respect to the moesian platform in line with previous rotation estimates based on structural geology the stability of the moesian platform during middle miocene eastward emplacement of the tisza block into the carpathian back arc supports dextral shear along the southern carpathians recorded by 13 6 ma clockwise strike slip related rotations in foreland deposits the new reference direction for the moesian platform and rhodope allows accurate quantification of the rotation difference with the west aegean domain at 38 0 7 2 occurring between 15 and 8 ma to accommodate this rotation we propose that the pivot point of the west aegean rotation was located approximately in the middle of the rotating domain rather than at the northern tip as previously proposed this new scenario predicts less extension southeast of the pivot point in good agreement with estimates from aegean structural geology northwest of the pivot point the model requires contraction or extrusion that can be accommodated by the coeval motion of the tisza block around the northwestern edge of the moesian platform

glaciation in the rila mountains bulgaria during the last glacial maximum abstract relict glacial landform complexes have been studied in the mountains of the central balkan peninsula since the end of the 19th century since their existence was proved for the first time by cvijic various authors have debated the number of glacial phases as well as their age at present the problem of age determination is being solved by the application of the new methods for numerical dating this paper is a detailed study of the maximum glaciation in the rila massif which is the highest mountain in bulgaria and in the whole balkan peninsula the application of cosmogenic nuclide dating 10be on moraine samples confirmed that the largest extent of former glaciers that left moraine deposits was around the time of the last glacial maximum most probably the maximum extent occurred in two phases the first around the beginning and the second around the end of the lgm 24 23 ka bp and 18 16 ka bp respectively separated by a retreat phase during the coldest but also driest phase of the glacial stage the gis processed calculations on the basis of field evidence of the former glacier extent and the preliminary calculations of the equilibrium line altitude ela through the accumulation ablation ratio aar method show that the ela during the lgm had quite small differences throughout the rila massif from about 2150 to 2200 m a s l in the nw to about 2250 2290 m in the se despite the considerable differences in terminal moraine depositional altitudes from 1150 to 2000 m a s l this is due to both the complicated pattern in the directions of moisture supply and to the influences of local topography

apatite u th sm he thermochronology of rapidly cooled samples the effect of he implantation apatite u th sm he ahe thermochronology is increasingly used for reconstructing geodynamic processes of the upper crust and the surface results of ahe thermochronology however are often in conflict with apatite fission track aft thermochronology yielding an inverted age relationship with ahe dates older than aft dates of the same samples this effect is mainly explained by radiation damage of apatite either impeding he diffusion or causing non thermal annealing of fission tracks so far systematic age inversions have only been described for old and slowly cooled terranes whereas for young and rapidly cooled samples too old ahe dates are usually explained by the presence of undetected u and or th rich micro inclusions we report apatite u th sm he results for rapidly cooled volcanogenic samples deposited in a deep ocean environment with a relatively simple post depositional thermal history robust age constraints are provided independently through sample biostratigraphy all studied apatites have low u contents 5 ppm on average while aft dates are largely in agreement with deposition ages most ahe dates are too old for leg 43 where deposition age of sampled sediment is 26 5 29 5 ma alpha corrected average ahe dates are up to 45 ma indicating overestimations of ahe dates up to 50 this is explained by he implantation from surrounding host u th rich sedimentary components and it is shown that ahe dates can be corrected by mechanically abrading the outer part of grains we recommend that particularly for low u th apatites the possibility of he implantation should be carefully checked before considering the degree to which the alpha ejection correction should be applied

timing rate and magnitude of slip on the buckskin rawhide detachment fault west central arizona we present thermochronologic and geochronologic data that constrain the slip history of the buckskin rawhide detachment fault in west central arizona one of the largest extensional fault systems in the north american cordillera u th he zircon and apatite thermochronology integrated with 40ar 39ar geochronology of postdetachment volcanic rocks indicate that large magnitude extension associated with the detachment fault initiated at 21 20 ma and continued until 12 11 ma in the southwestern portion of the buckskin rawhide metamorphic core complex u th he footwall cooling ages from the breakaway zone in the western bouse hills to upper greenschist facies mylonites in the southern buckskin mountains indicate that the slip rate on the detachment fault was 3 1 5 1 km myr during the early miocene space time patterns of hanging wall tilting suggest that at 17 16 ma a secondary detachment fault breakaway developed 12 km northeast of the primary detachment fault breakaway proximal conglomerates deposited in a supradetachment basin adjacent to the secondary breakaway scarp were displaced 6 11 km northeast in the middle miocene by the buckskin rawhide detachment fault at a slip rate of 1 2 2 7 km myr the total displacement across the detachment fault in the southwestern portion of the core complex is 24 10 km well short of the previous estimate of 66 8 km across the entire core complex based on these data and new observations we propose that total displacement on the buckskin rawhide detachment fault system increases in the slip direction to 40 50 km at the northeastern end of the exposed footwall corresponding to time averaged slip rates that ranged from 2 km myr to 6 km myr across the entire core complex

thermal constraints on the tectonic evolution of a metamorphic core complex santa catalina mountains arizona abstract we present an analysis of the thermal evolution of the metamorphic core complex of the santa catalina rincon and tortolita mountains in south arizona the structural and kinematic data are briefly reviewed granite mylonites result from three successive shearing events respectively compressional top west during paleocene and top ne during mid eocene and extensional top sw after eocene in a preliminary part of the paper available radiometric data are reviewed in detail for both deformed and undeformed granites with closing temperatures from 565 to 105 c these data are then used to constrain the temperature history for three intrusions which were emplaced respectively during paleocene eocene and miocene times the general temperature time curve shows 1 rapid cooling for the three intrusions just after emplacement and 2 a large and rapid cooling of the entire complex between 35 and 22 ma from 530 to 100 c in the final part this thermal history is used to constrain the tectonic history of the metamorphic core complex the thermal effects of erosion tectonic denudation homogeneous and heterogeneous thinning are computed using a finite difference scheme in one dimension an analysis of the parameters involved in the models shows that the crust of the santa catalina metamorphic core complex has undergone mainly a thinning of its upper part of at least 15 km and more reasonably 20 25 km in less than 10 ma this estimation is discussed considering thermal effects of magmatism

low temperature thermochronology in the peruvian central andes implications for long term continental denudation timing of plateau uplift canyon incision and lithosphere dynamics abstract in peru the western edge of the 4 5 km high western cordillera is cut by a 3 km deep canyon to understand incision by the cotahuasi ocona river and the regional uplift history of this orogenic plateau capped by volcanic rocks 26 crystalline rock samples were collected for low temperature thermochronology from vertical profiles parallel and perpendicular to the canyon rock cooling histories confirm that most plateau denudation had occurred prior to 24 ma but plateau incision peaked after c 14 9 ma in response to rapid surface uplift the abrupt occurrence of a rock heating event is also detected during middle miocene time this was either a response to the emplacement of low conductivity regionally extensive ignimbritic caprock or a response to crustal scale fluid circulation caused by wet melting of the overriding plate when magmatism resumed c 24 ma the potential for thermochronology to provide information on past geothermal gradients is discussed showing how it can be used as a proxy for understanding change in subducting slab dynamics with oscillations in subduction angle having perhaps been the main on off switch for magmatism in this cordilleran setting supplementary material fission track and apatite u th he results and apatite chemistry indicators are available at http www geolsoc org uk sup18405