deformation history of the high pressure lycian nappes and implications for tectonic evolution of sw turkey 1 in southwestern turkey the lycian nappe complex which overlies the autochthonous menderes massif and bey dag platform consists from base to top of metasediments a melange unit and an ophiolitic sequence fresh fe mg carpholite occurrence in the metasediments attests to a high pressure low temperature metamorphic event we report the distribution of fe mg carpholite and its breakdown products e g pyrophyllite and chloritoid on the bodrum peninsula south of the menderes crystalline massif the distribution of fe mg carpholite and its relics shows that the low grade high pressure metamorphism affected a widespread area in the lower units of the lycian nappes analysis of the ductile deformation in hp lt metasediments indicates shear senses top to the northeast to top to the east most of this deformation is contemporaneous with the retrogression of high pressure low temperature parageneses and is therefore coeval with exhumation from a depth of about 30 km at the top of the menderes massif cover series close to the contact with the lycian nappes similar eastward displacements are observed and trajectories of the stretching lineations are continuous from the lycian nappes to the menderes massif across the contact these observed movements are incompatible with the southward transport of the lycian nappes over the menderes massif we discuss the regional tectonic implications and conclude that the lycian nappes and the southernmost part of the menderes massif were exhumed in two stages 1 eocene top to the ne shear syn orogenic extension 2 miocene deformation contemporaneous with the aegean extension

structural characteristic and origin of intra continental fold belt in the eastern sichuan basin south china block abstract the fold and thrust belt in the eastern sichuan basin is represented by a series of subparallel chevron anticlines under the orogenic tectonic setting within the south china block in meso cenozoic period and the influence of the multi layer detachment fault the deformation of the thrust belt exhibits remarkably layered and large scale intracontinental thrusting structural characteristics in this paper we focus on the structural geometry and deformational mechanisms using the latest two dimensional 2d and three dimensional 3d seismic reflection data in combination with well and outcrop data the multi layer detachment faults especially the upper gypsum bearing detachment in the middle triassic jialingjiang formation and lower detachment with gypsum or shale in the lower middle cambrian system directly control the deformational styles of the study area interpretation of seismic sections indicates that the fold and thrust belt has various deformational styles during folding including fault propagation fold fault bend fold and detachment fold with box fold or pop up structural geometry regional location and structural boundaries play significant roles in controlling the deformational styles and distinct differences exist among the different anticlines the huayingshan anticline located at the front of the thrust belt shows intense structural deformation with northwestward thrusting direction and a relatively weak opposite southeastward thrusting in addition the anticlines exhibit structural differences along strike and the fold and thrust belt in the northern segment is influenced by the north china block

paleomagnetic modeling of seamounts near the hawaiian emperor bend abstract the hawaiian emperor seamount chain records the motion of the pacific plate relative to the hawaiian mantle hotspot for 80 m y a notable feature of the chain is the pronounced bend at its middle this bend had been widely credited to a change in plate motion but recent research suggests a change in hotspot motion as an alternative existing paleomagnetic data from the emperor chain suggest that the hotspot moved south during the late cretaceous and early tertiary but reached its current latitude by the age of the bend thus data from area of the bend are important for understanding changes in plume latitude in this study we analyze the magnetic anomalies of five seamounts annei daikakuji w daikakuji e abbott and colahan in the region of the bend these particular seamounts were chosen because they have been recently surveyed to collect multibeam bathymetry and magnetic data positioned with gps navigation inversions of the magnetic and bathymetric data were performed to determine the mean magnetization of each seamount and from these results paleomagnetic poles and paleolatitudes were calculated three of the five seamounts have reversed magnetic polarities two are normal and four contain a small volume of magnetic polarity opposite to the main body consistent with formation during the early cenozoic a time of geomagnetic field reversals although magnetization inhomogene ties can degrade the accuracy of paleomagnetic poles calculated from such models the seamounts give results consistent with one another and with other pacific paleomagnetic data of approximately the same age seamount paleolatitudes range from 13 7 to 23 7 with an average of 19 4 7 4 2 these values are indistinguishable from the present day paleolatitude of the hawaiian hotspot together with other paleomagnetic and geologic evidence these data imply that the hawaiian hotspot has moved little in latitude during the past 45 m y

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

tectonic evolution of the gediz graben field evidence for an episodic two stage extension in western turkey western turkey is one of the most spectacular regions of widespread active continental extension in the world the most prominent structures of this region are e w trending grabens e g gediz and buyuk menderes grabens and intervening horsts exposing the menderes massif this paper documents the result of a recent field campaign field geological mapping and structural analysis along the southern margin of the modern gediz graben of pliocene 5 ma age this work provides field evidence that the presently low angle ductile brittle detachment fault is cut and displaced by the high angle graben bounding normal faults with total displacement exceeding 2 0 km the evolution of the n s extension along the gediz graben occurred during two episodes each characterized by a distinct structural styles 1 rapid exhumation of menderes massif in the footwall of low angle normal fault core complex mode during the miocene 2 late stretching of crust producing e w grabens along high angle normal faults rift mode during pliocene quaternary times separated by a short time gap the later phase is characterized by the deposition of now nearly horizontal sediments of pliocene age in the hanging walls of the high angle normal faults and present day graben floor sediments the evolution of extension is at variance with orogenic collapse and or back arc extension followed by the combined effect of tectonic escape and subduction rollback processes along the aegean cyprean subduction zone consequently it is misleading to describe the miocene sediments exhumed on shoulders of the gediz graben as simple graben fill

supradetachment basin evolution during continental extension the aegean province of western anatolia turkey we present a detailed structural and stratigraphic record of a neogene quaternary supradetachment sedimentary succession in the aegean extensional province of western anatolia and we compare its tectonic features and evolution to those of other well documented supradetachment basins around the world the sedimentary fill of the alasehir basin records the uplift and exhumation of a core complex in the footwall of a detachment fault within the central menderes massif accumulation of footwall derived clastic sediments in this basin started ca 20 ma shortly after the initiation of the approximately e w trending alasehir detachment and its shear zone and continued until ca 2 ma major sedimentary facies types include fluvial and alluvial fan deposits debris flow and mass flow deposits and locally developed lacustrine rocks these sedimentary units were accumulated largely in distal depocenters within the extending basin as the low angle 15 28 detachment faulting created little accommodation space near the basin margins while producing high back shed topography in the uplifted menderes core complex the drainage system was dominated mainly by extension parallel transverse streams during the main phases of basin evolution extension parallel scissor hinge faulting produced differential uplift and subsidence in the adjacent fault blocks changed the direction of sediment transport and drainage patterns over short distances and resulted in the local uplift of the older basin strata these processes led to the development of subbasins with lateral variations in basement topography strata thickness and sedimentary facies distribution and generated a segmented basin architecture high angle synthetic and antithetic faults that formed extensively after 3 ma caused back tilting of the sedimentary strata formation of half grabens with their own axial drainage systems and development of angular unconformities with the onset of this crustal scale block faulting the detachment fault ceased to operate and the quaternary gediz graben started to develop at the northern end of the alasehir supradetachment basin our comparative evaluation of select basins shows a maximum sediment thickness of 3 km average extension rates of 6 to 8 9 mm yr 1 and accumulation rates of 0 1 0 2 mm yr 1 uncorrected for compaction in supradetachment basins in general the rates and amounts of extension the geometry of detachment faulting the rates of footwall uplift and the kinematics and interplay of different fault systems are the most important factors controlling three dimensional structural architecture and evolution of supradetachment basins

modeling of the foca uzunada magnetic anomaly and thermal structure in the gulf of izmir western turkey abstract the gulf of izmir goi is one of the largest gulfs in the aegean sea turkey there is a large magnetic anomaly extending in the ne sw direction between foca and uzunada uzun island in the gulf previously curie point depth cpd geothermal gradient heat flow and radiogenic heat production maps of the onshore part of the aegean region were constructed from the aeromagnetic data in this study the same maps except radiogenic heat production map are presented for the offshore part and the largest magnetic anomaly in the northern part of the gulf is focused particularly as a result the thermal structure of goi is clearly defined and according to the results of this study cpd values were found from 7 km in the ne of foca to 10 km through the south of the gulf the geothermal gradient values vary between 50 and 80 c km maximum heat flow values around the anomaly are calculated as 200 and 215 mw m2 according to the thermal conductivity coefficients of 2 5 w m 1 k 1 and 2 7 w m 1 k 1 respectively although the anomaly is located in the izmir gulf cpd geothermic gradient heat flow anomalies are shifted through the north of foca and aliaga towns in the candarli bay this prominent anomaly in the gulf of izmir is associated with the magmatics that were encountered at 969 m in the foca 1 well although it was drilled about 2 km away from the outermost closed contour of the magnetic anomaly the anomaly is also modeled three dimensionally 3d in this study in the model map the top of the causative body is completely located in the outer part of the gulf and is very shallow at about 0 5 km while its bottom is inclined through the west of cigli and menemen from this viewpoint it is possible to suggest that the causative body is inclined through the foca peninsula however its closed contours are in the ne direction through the candarli bay top depth of the causative body is also calculated from the basement horizon on the seismic sections crossing this anomaly depth calculations are consistent in these sections and confirm the top depths from the modeling study the basement geometry in the seismic sections also reflects the shape of 3d model geometry and bottom depth of the magmatics is also verified by the basement depth calculations in seismic sections

an active bivergent rolling hinge detachment system central menderes metamorphic core complex in western turkey two symmetrically arranged detachment systems delimit the central menderes metamorphic core complex and define a bivergent continental breakaway zone in the anatolide belt of western turkey structural analysis and apatite fission track thermochronology show that a large east trending syncline within the alpine nappe stack in the central part of the orogen is related to late miocene early pliocene to recent core complex formation the syncline formed as a result of two opposite facing rolling hinges in the footwalls of each of the two detachments back rotation of the syncline limbs suggests that the detachments rotated from an initial dip of 408 608 to a currently shallow orientation of 08 208

the multiple inverse method a new technique to separate stresses from heterogeneous fault slip data abstract a new inverse technique is presented here to separate stresses from heterogeneous fault slip data without a priori information on the stresses or on the classification of faults according to the stresses four parameters are determined by the inversion one for the shape of the stress ellipsoid and three for the direction of the stress axes accordingly the inversion is equivalent to the projection of the fault slip data to a point in four dimensional parameter space the data are divided into k element subsets to which the inverse technique is applied where k 4 or 5 is the optimal choice for the stability of solutions and for the reduction of computation significant solutions are identified as clusters in parameter space the technique is demonstrated first by simulated fault slip data as an example field data obtained from miocene fore arc sediments in western japan were processed by the method

application of 3d magnetic amplitude inversion to iron oxide copper gold deposits at low magnetic latitudes a case study from carajas mineral province brazil abstractstrong hydrothermal alteration modifies rock physical properties in iron oxide copper gold deposits iocgs and may result in characteristic signatures detectable in geophysical surveys magnetic data are commonly used in characterizing orebodies and 3d inversions are often used to assist in interpretations in areas with strong remanence and self demagnetization the total magnetization can have directions different from the inducing field direction this deviation precludes the use of traditional inversion methods magnetic amplitude inversion offers one solution to this challenge because the amplitude data are weakly dependent on the magnetization direction in addition the low magnetic latitude also imposes difficulty in amplitude data calculation due to the instability in the component conversion in the wavenumber domain to formulate a practical approach we present a case study on applying the magnetic amplitude inversion to the furnas southeast iocg deposit at the low magnetic latitude i

isotopic evidence for a transition from subduction to slab tear related volcanism in western anatolia turkey abstract volcanic rocks in western turkey show age progressive magmatism migrating from northeast to southwest that reflects a southward shift of the aegean subduction zone during the miocene slab segmentation during this period of trench roll back is thought to have imposed source region heterogeneity trending northwest to southeast in this study we present new sr nd pb and o isotopic analyses from the miocene volcanic rocks of the usak gure basin and compare these to previously published data the data demonstrate a change from subduction related sources around the menderes core complex to more asthenospheric sources in the afyon region isotopic compositions sr nd pb of volcanic rocks from the demirci and selendi basins to the west and the afyon volcanic area to the east indicate minimal upper crustal contamination the most primitive lavas also reveal increasing k contents from west the ne sw trending basins to east afyon region it is suggested that the composition of the western anatolian volcanic rocks change from orogenic with lithospheric mantle sources associated to denudation of the menderes massif core complex mmcc to anorogenic with asthenospheric mantle sources in the vicinity of the kirka afyon isparta kai volcanic province with time from early miocene to quaternary there is no asthenospheric contribution during the late miocene onwards in the eastern margin of the mmcc while the asthenospheric upwelling occurred only in a small area beneath the exhuming core complex we interpret the usak gure basin to reflect a structural boundary showing a transition from a subduction influenced metasomatized mantle source to asthenospheric mantle source volcanism driven by slab tearing between the hellenic and cyprus slab segments the usak mugla transfer zone umtz most likely corresponds to slab tear related westernmost faults that were induced by initiation of slab segmentation processes following the late miocene circa 11 ma and possibly since the early miocene

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

linking microcracks and mineral zoning of detachment exhumed granites to their tectonomagmatic history evidence from the salihli and turgutlu plutons in western turkey menderes massif abstract the menderes massif western turkey is a metamorphic core complex that displays linked syntectonic plutonism and detachment faulting fabrics in s type peraluminous granites salihli and turgutlu in the detachment alasehir footwall change from isotropic to protomylonitic to mylonitic towards the structure samples from the isotropic and protomylonitic zones were imaged in transmitted light cathodoluminescence cl backscattered bse and secondary electrons se and show that these rocks contain abundant microcracks and that plagioclase grains have zoning consistent with magma mixing the granites contain fluid inclusion planes fips myrmekite replacing plagioclase and the removal of blue luminescence in k feldspar along microcracks and grain boundaries calcite and hydrous minerals commonly fill microcracks the samples record features that formed due to 1 magma crystallization and ductile deformation fips mineral zoning 2 changes in p and or t impingement and stress induced microcracks in protomylonitic rocks and 3 differences in intrinsic mineral properties radial cleavage blunted and deflected microcracks overprinted microcracks indicate exhumation during pulses the middle miocene ages of these granites reported elsewhere are similar to those from large scale extensional structures in greece s cycladic massif the menderes and cycladic core complexes may have developed simultaneously due to the widespread intrusion of subduction related granitoids

diachronous uplift and cooling history of the menderes core complex western anatolia turkey based on new zircon u th he ages abstract new u th he thermochronology data from the syn extensional granitoids in the central part of the menderes massif in western turkey reveal a minimum slip rate of 12 5 km myr along the alasehir detachment 14 dip angle and denudation rates between 1 75 km myr and 3 25 km myr between 4 ma and 2 ma these values suggest relatively fast exhumation of the central sub massif associated with cooling rates between 53 c myr and 128 c myr which are higher than the estimated footwall cooling rates 60 c myr to 120 c myr from the northern sub massif based on the initial crystallization ages of the syn extensional granitoid intrusions and their exhumation related cooling ages our thermochronological findings suggest that the central sub massif in menderes underwent accelerated uplift and faster exhumation in the latest cenozoic than the northern and southern sub massifs this latest doming and rapid extension of the central sub massif was associated with the asthenospheric upwelling beneath the region and the related na alkaline kula volcanism our results indicate that the menderes massif has had a diachronous uplift and cooling history during its extensional tectonic evolution in the late cenozoic thermal weakening of the young orogenic crust in western anatolia via both lithospheric and asthenospheric melting episodes and magmatism produced higher than normal geothermal gradients and played a significant role in core complex formation

the role of the flexural rotation rolling hinge model in the tectonic evolution of the alasehir graben western turkey the alasehir graben is a well defined prominent extensional structure in western turkey generally trending e w and containing four sedimentary units at the beginning of graben formation during early middle miocene times the first fault system was active and responsible for the accumulation of the first and second sedimentary units in pliocene times a second fault system developed in the hanging wall of the first system and a third sedimentary unit was deposited the recently active third fault system separates older graben fill and a fourth sedimentary unit activity on each fault system caused the rotation and uplift of previous systems similar to the flexural rotation rolling hinge model but our field observations indicate that the rotated first fault system is also active allowing exhumation of larger amounts of rock units this paper documents that graben formation in western turkey is a sequential process its different periods are represented by three fault systems and associated sedimentation consequently recent claims using age data from only the second and or third sedimentary units to determine the timing of graben formation are misleading

geochemistry geochronology and cathodoluminescence imagery of the salihli and turgutlu granites central menderes massif western turkey implications for aegean tectonics abstract the menderes massif western turkey is an important metamorphic core complex located in the aegean region geochemical and geochronological data from this extensional domain facilitates our understanding of large scale extension of the earth s lithosphere s type peraluminous granites salihli and turgutlu that intrude the alasehir detachment which bounds the northern edge of the central menderes massif may have been generated due to subduction of the eastern mediterranean floor along the hellenic trench in situ th pb ion microprobe monazite ages from the granites range from 21 7 4 5 ma to 9 6 1 6 ma 1 higher uncertainty in the ages is attributed to monazite common pb but the range is consistent with cathodoluminescence cl imagery that document complex textures within the samples salihli and turgutlu granites share many similar characteristics including multiple generations of plagioclase some with shocked cores plagioclase replacing k feldspar and the development of myrmekite evidence for fluid interaction and multiple generations of microcracks and microfaults the granites may have evolved from compositionally distinct magma sources as salihli samples in general contain allanite as the major accessory mineral whereas turgutlu granites contain monazite however the cl imagery document similar alteration textures the youngest turgutlu monazite grain 11 5 0 8 ma is located in the rim of a k feldspar grain close to myrmekite and the youngest salihli monazite grain 9 6 1 6 ma is located in the outer edge of an altered plagioclase crystal these ages likely time episodes of deformation as the granites were subjected to exhumation along the alasehir detachment ages reported here are similar to dates constraining extension reported elsewhere in the aegean but indicate a level of complexity when linking movement within the menderes massif to the large scale geodynamic processes that created other metamorphic core complexes in the region difficulties exist in linking the ages obtained from the granites to specific tectonic events due to the presence of secondary alteration textures generations of mineral growth and multiple episodes of deformation

geology of the bozdag area central menderes massif sw turkey pan african basement and alpine deformation the menderes massif consists of a precambrian core series that preserves evidence for a polymetamorphic history and a paleozoic mesozoic cover series that experienced only the alpine tectonometamorphic evolution structural petrographic and geochronologic investigations in the central menderes massif demonstrate that a part of the metamorphic and structural evolution of the precambrian basement is older than the undeformed 551 1 4 ma old birgi metagranite and b inferred alpine fabrics overprinting the cover series largely have the same attitudes as the old structures in the much older core series the inferred alpine fabrics include both contractional and extensional structures contraction under greenschist to amphibolite facies conditions resulted in the imbrication of the core and cover series and generated an inverted metamorphic sequence by north directed thrusting during alpine extension most of the south dipping thrust faults were reactivated as extensional shear zones under decreasing greenschist facies conditions

magnetic anomaly map of ori massif and its implications for oceanic plateau formation abstract many oceanic plateaus have been emplaced at or adjacent to mid ocean ridges to explain plateau volume and thickened crust compared to normal oceanic crust hotspot ridge interaction is commonly assumed but the manner of interaction remains unclear the shatsky rise oceanic plateau is a large volcanic mountain that formed at a triple junction during late jurassic and early cretaceous time recent drilling and seismic investigations suggest that the intermediate edifice in the rise ori massif is a central volcano paradoxically magnetic lineations were traced across parts of ori massif implying formation at a spreading ridge in this study we examined magnetic anomalies over and around ori massif to obtain insights about the formation of this volcanic edifice magnetic data from 21 cruises were corrected combined and gridded to construct a magnetic anomaly map forward and inverse magnetic modeling was done to investigate the magnetic structure of ori massif the results imply that this large volcanic edifice is predominantly characterized by linear magnetic anomalies resulting from alternating normal and reversed polarity magnetization blocks analogous to magnetic anomalies recorded by spreading ridges this magnetic structure is not expected for a central volcano that was built by long runout lava flows implying that ori massif eruptions must have been constrained near the ridge axis magnetic bights on the north and south boundaries of ori massif imply that it was bracketed by triple junctions indicating complex ridge tectonics during the formation of shatsky rise the surprising finding that ori massif is traversed by coherent linear magnetic anomalies indicates that oceanic plateaus can record seafloor spreading magnetic anomalies despite large crustal thickness other oceanic plateaus also record linear magnetic anomalies implying a link between divergent plate boundaries and oceanic plateau volcanism

analysis of non striated faults in a recent extensional setting the plio pleistocene concud fault jiloca graben eastern spain the integration of palaeostress results obtained from the analysis of non striated faults and joints affecting plio pleistocene deposits near the concud fault southern jiloca graben eastern spain yields a multidirectional tension stress field vertical s1 s2zs3 where the primary s3 trajectories trend ene the results also show strong deflections of stress trajectories with many local s3 axes being either orthogonal or parallel to the trace of the concud fault the stress field persisted throughout the period of activity of the fault i e late pliocene and pleistocene the agreement between the present results and the regional picture gives support to the stress inversion method and shows its usefulness in palaeostress analysis of young poorly lithified rocks

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

late cenozoic cooling history of the central menderes massif timing of the buyuk menderes detachment and the relative contribution of normal faulting and erosion to rock exhumation abstract based on new thermochronological data and 10be derived erosion rates from the southern part of the central menderes massif aydin block in western turkey we provide new insights into the tectonic evolution and landscape development of an area that undergoes active continental extension fission track and u th he data reveal that the footwall of the buyuk menderes detachment experienced two episodes of enhanced cooling and exhumation assuming an elevated geothermal gradient of 50 c km the first phase occurred with an average rate of 0 90 km myr in the middle miocene and the second one in the latest miocene and pliocene with a rate of 0 43 km myr the exhumation rates between these two phases were lower and range from 0 14 to 0 24 km myr depending on the distance to the detachment cosmogenic nuclide based erosion rates for catchments in the aydin block range from 0 1 to 0 4 km myr the similarity of the erosion rates on both sides of the aydin block northern and southern flank indicate that a rather symmetric erosion pattern has prevailed during the holocene if these millennial erosion rates are representative on a million year timescale they indicate that apart from normal faulting erosion in the hanging wall of the buyuk menderes detachment fault did also contribute to the exhumation of the metamorphic rocks

granitoid rocks of the southern menderes massif southwestern turkey field evidence for tertiary magmatism in an extensional shear zone recent field campaign in the southern menderes massif in southwestern turkey revealed that the so called core of the massif comprises two distinct types of granitoid rocks an orthogneiss traditionally known as augen gneisses and leucocratic metagranite where the latter is intrusive into the former and the structurally overlying cover schists these differ from one another in intensity of deformation degree of metamorphism and kinematics the orthogneiss display penetrative top to the n nne fabrics formed under upper amphibolite facies conditions during the eocene main menderes metamorphism mmm whereas foliation and stretching lineation exists in the leucocratic metagranites but are not strongly developed the leucocratic metagranites show evidence of syn to post emplacement deformation in a series of weakly developed top to the s ssw fabrics formed under lower greenschist facies conditions leucocratic metagranite bodies occur all along the augen gneiss schist contact in the southern menderes massif they are emplaced as sheet like bodies into country rocks previously deformed and metamorphosed during a top to the n nne alpine orogeny along a ductile extensional shear zone located between orthogneisses and metasediments which was possibly active during emplacement the data presently available indicate that emplacement and associated ductile extensional deformation occurred during late oligocene early miocene time these results confirm previous contentions that there are tertiary granites in this part of the menderes massif

an inverse problem in microtectonics for the determination of stress tensors from fault striation analysis abstract a method is proposed to compute some characteristics of a possible stress tensor related to striations measured in a given faulted area if several tectonic phases are responsible for the striations the method separates and determines the successive stress tensors the iterative algorithm consists of alternatively a sorting the data attributed to a tectonic phase and b computing the characteristics of the stress tensor of this phase the method is tested using an application to synthetic and actual data

the menderes massif of western turkey and the cycladic massif in the aegean do they really correlate based on lithostratigraphic comparisons the menderes massif has been correlated with the cycladic massif thereby implying that the eastern mediterranean consists of a narrow pre alpine basement belt which is laterally continuous over a long distance and which experienced a similar alpine orogenic history our work indicates that the architecture the age of basement and the pre alpine and alpine tectonometamorphic history of both massifs differ fundamentally from each other the menderes massif consists of remnants of the cycladic massif which overly an exotic unit the menderes nappes both massifs do not represent lateral continuations which has implications for palaeogeographic reconstructions

a critical analysis of the structure and tectonic significance of rift oblique lineaments transfer zones in the mesozoic cenozoic succession of the faroe shetland basin ne atlantic margin abstract nw se trending rift oblique lineaments transfer zones9 occur along the length of the ne atlantic margin previous workers have suggested that these lineaments played an important role in providing conduits and or barriers to sedimentation during the cretaceous and palaeocene it has also been suggested that they were active as discrete basin wide strike slip faults this study uses a well calibrated 3d seismic survey of regional extent to critically assess the structural and stratigraphic evidence for three rift oblique lineaments in the uk sector of the faroe shetland basin victory clair and judd lineaments structures previously attributed to basin wide strike slip deformation can be more simply explained as igneous intrusions hydrothermal vent complexes gas chimneys and or faults that transfer extensional strain between en echelon rift segments there is little evidence to suggest that activity along discrete basin wide lineaments controlled palaeocene sedimentation within the faroe shetland basin rather sediment transport and deposition at this time are likely to have been controlled by along and across strike variations in the magnitude of thermal subsidence which in turn reflect the 3d nature of the underlying mesozoic rift architecture

geochemical and temporal evolution of cenozoic magmatism in western turkey mantle response to collision slab break off and lithospheric tearing in an orogenic belt post collisional magmatism in western anatolia began in the eocene and has occurred in discrete pulses throughout the cenozoic as it propagated from north to south producing volcano plutonic associations with varying chemical compositions this apparent sw migration of magma tism and accompanying extension through time was a result of the thermally induced collapse of the western anatolian orogenic belt which formed during the collision of the sakarya and tauride anatolide continental blocks in the late paleocene the thermal input and melt sources for this prolonged magmatism were provided first by slab break off generated aesthenospheric flow then by lithospheric delamination related aesthenospheric flow followed by tectonic extension driven upward aesthenospheric flow the first magmatic episode is represented by eocene granitoid plutons and their extrusive carapace that are linearly distributed along the izmir ankara suture zone south of the marmara sea these suites show moderately evolved com positions enriched in incompatible elements similar to subduction zone influenced subalkaline magmas widespread oligo miocene volcanic and plutonic rocks with medium to high k calc alkaline compositions represent the next magmatic episode partial melting and assimilation fractional crystallization of enriched subcontinental lithospheric mantle derived magmas were important processes in the genesis and evolution of the parental magmas which experienced decreasing subduction influence and increasing crustal contamination during the evolution of the eocene and oligo miocene volcano plutonic rocks collision induced lithospheric slab break off provided an influx of aesthenospheric heat and melts that resulted in partial melting of the previously subduction metasomatized mantle lithosphere beneath the suture zone producing the eocene and oligo miocene igneous suites the following magmatic phase during the middle miocene 16 14 ma developed mildly alkaline bimodal volcanic rocks that show a decreasing amount of crustal contamination and subduction influence in time both melting of a subduc tion modified lithospheric mantle and aesthenospheric mantle derived melt contribution played a significant role in the generation of the magmas of these rocks this magmatic episode was attended by region wide extension that led to the formation of metamorphic core complexes and graben systems aesthenospheric upwelling caused by partial delamination of the lithospheric root beneath the western anatolian orogenic belt was likely responsible for the melt evolution of these mildly alkaline volcanics lithospheric delamination may have been caused by peeling off during slab rollback the last major phase of magmatism in the region starting c 12 ma is represented by late miocene to quaternary alkaline to super alkaline volcanic rocks that show oib like geochemical features with progressively more potassic compositions increasing toward south in time these rocks are spatially associated with major extensional fault systems that acted as natural conduits for the transport of uncontaminated alkaline magmas to the surface the melt source for this magmatic phase carried little or no subduction component and was pro duced by the decompressional melting of aesthenospheric mantle which flowed in beneath the atte nuated continental lithosphere in the aegean extensional province this time progressive evolution of cenozoic magmatism and extension in western anatolia has been strongly controlled by the interplay between regional plate tectonic events and the mantle dynamics and provides a realistic template for post collisional magmatism and crustal extension in many orogenic belts

pliocene quaternary tectonic evolution of the gulf of gokova southwest turkey abstract evolution of the east west trending gokova graben structure is related to the north south extension of the aegean segment of the aegean anatolian microplate the pliocene quaternary successions surrounding the onland portion of the gokova graben as well as coeval successions within the marine portion of the graben are cut by at least three families of faults that strike northwest southeast east west and east northeast west southwest these orientations are inconsistent with a simple north south extensional regime interpretation of seismic reflection profiles multibeam bathymetry and gps vectors indicates that the gokova graben developed as a lazy s shaped graben in the back arc setting north of the hellenic arc a counterclockwise rotation of the aegean segment of the aegean anatolian microplate is the suggested mechanism for this geometry as subduction zone rolled back occurred during the pliocene quaternary the gulf of gokova is the youngest of a series of basins that developed within this large back arc system including the nisyros karpathos and kamilonisi basins collectively named to as the gokova nisyros karpathos graben it is proposed that this graben experienced a scissor like opening initiating from the west during the pliocene and progressing eastward during the quaternary faults that are seemingly un correlated onland and in the marine areas become remarkably aligned when the marmaris rhodes block is progressively rotated by 6 counterclockwise relative to the mugla block using a pole position located within the gulf of gokova the scissor like opening of the westernmost regions of the gokova graben likely occurred during the late pliocene whereas the central and eastern portions of the graben developed during the early middle pleistocene and late pleistocene holocene respectively the onset of the opening of the westernmost segment of the gokova nisyros karpathos graben occurred at a time earlier than the late pliocene

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

menderes massif western turkey structural metamorphic and magmatic evolution a synthesis the menderes massif covers large areas in western turkey the better understanding of its tectono metamorphic history would provide insight for the alpine evolution of western turkey and the entire eastern mediterranean region this paper summarizes the available literature on the metamorphic rocks of western turkey and that of the menderes massif with special reference and emphasis to the papers presented in the special issue

extensional folding in the alasehir gediz graben western turkey the broad folds exposed in the syn extensional sedimentary rocks of the alasehir graben western turkey have been recently interpreted as contractional in origin our field mapping of these folds suggests that they are the products of extensional tectonics the field evidence includes the presence of several longitudinal extensional folds such as a rollover anticline and drag folds that are related to normal faults in the area the extensional nature of these folds negates the previous interpretation and consequently suggests extensional tectonics in the region was not interrupted by short lived contractional tectonics

three dimensional geometry and growth of conjugate normal faults abstract good quality 2 d and 3 d seismic reflection data from the timor sea are used to determine the threedimensional geometry displacement patterns and development of intersecting conjugate normal faults these data are supplemented by data from previous physical modelling studies conjugate structures which comprise two intersecting opposed dipping normal faults or fault sets form synchronously on a geological time scale and develop due to the incidental intersection of the faults factors which affect both the formation and imaging of these structures include the fault density the spatial distribution of opposed dipping faults the seismic resolution and the vertical extent of the imaged fault data large conjugate structures grow from smaller ones larger conjugates are associated with more numerous and larger faults than small structures on the scale of the seismic data fault throws range from ca 10 400 m synchronous fault movements are accommodated by a reduction of displacements on discrete fault surfaces towards the fault intersection zone and a corresponding increase in ductile strain of this region high strains in the volume proximal to the fault intersection zone are expressed as thinning of stratigraphic units between the conjugate faults and are believed to be accommodated by numerous small sub seismic faults intersection of two opposed dipping faults does not prevent their continued synchronous movement and does not result in mechanical locking of the system

syn rift sedimentation and structural development of the gediz and buyuk menderes graben western turkey the buyuk menderes and gediz graben of western turkey developed during miocene to recent extension in the aegean region new mapping of structures and sedimentary lithofacies in exhumed basin fill strata is used to reconstruct the evolution of the graben field evidence shows that extension was primarily accommodated by tilted fault blocks 0 2 0 8 km wide bounded by planar faults with some modification by antithetic faulting the basins are faulted on both margins although they are highly asymmetric with dominant 9footwall9 margins characterized by steeper topography and greater thicknesses of exhumed strata within exhumed graben fill sequences lacustrine axial fluvial and laterally derived sedimentary facies can be identified palaeocurrent orientations divergent wedge geometries and intra basin unconformities all indicate that exposed sediments are syn tectonic the present day map patterns demonstrate that the position of graben bounding faults has migrated basinward with time as a result large scale erosion and recycling of the uplifted basin fill have created extensive footwall derived alluvial fans these displace the axial drainage towards the hanging wall margins away from the locus of greatest subsidence

the 40ar 39ar age of extensional ductile deformation and granitoid intrusion in the northern menderes core complex implications for the initiation of extensional tectonics in western turkey the simav detachment fault in the northern part of menderes core complex in western turkey separates cover sequence rocks with brittle deformation from high grade metamorphic core rocks and young granitoid intrusions the timing of shear zone formation and the intrusion of syn tectonic granitoids is constrained by 40ar 39ar geochronology on muscovite from mylonitic gneiss and biotite from the egrigoz granitoid 40ar 39ar data indicate that mylonitic deformation occurred at 22 86 0 47 ma whilst the cooling age of the granitoid is 20 19 0 28 ma the intrusion and cooling of the egrigoz granitoid occurred between 23 20 ma these data demonstrate that extensional deformation in the northern menderes core complex began before early miocene times and represents an early stage in the tertiary extensional tectonics of western turkey

pattern of normal faulting in the gediz graben sw turkey hanging wall deformation of the fault systems controlling the southern margin of the gediz graben were investigated separately within the plio quaternary and neogene predominantly miocene deposits of the graben fill fault styles observed in both packages share many similarities in terms of geometry and comprise conjugate fault sets that show clustering of strike orientations predominantly around wnw ese but also sw ne and nw se directions the main difference between the two units is observable in terms of fault dips and rake of the slickenside lineations measured on the exposed fault planes both measurements show a uni modal distribution for the plio quaternary deposits but a tri modal distribution for the neogene deposits this variation is probably related to the geometrical modification of the older faults by the process of domino style back rotation in the hanging wall of higher order faults similarities among the two units are not limited to geometrical aspects of the fault systems but also counts for the orientation of the principal stress axes that controlled the deformation during the deposition of each sedimentary package inversion of the fault slip data showed that approximately n s oriented extension which varies in the range of nnw sse and nne ssw controlled the faulting during the accumulation of the entire graben fill with almost no evidence of change in the state of stress during the graben evolution however some heterogeneity in terms of stress field is observable among the fault systems formed within the same time frame this heterogeneity is probably related to poorly defined direction of extension in the graben indeed low ratio in the order of 0 25 suggests that 2 and 3 are close in magnitudes and the direction of extension is not well constraint with a potential of 2 3 axes permutations local stress field anomalies related to fault segment interaction could also contribute to the observed heterogeneity

timing of tectonic events in the menderes massif western turkey implications for tectonic evolution and evidence for pan african basement in turkey the menderes massif forms the western of the two large metamorphic culminations within the turkish alpide orogen it has three major lithologic units with a gneissic core at the base and a schist and a marble envelope overlying it successively although relations between them have been largely obscured by the polymetamorphic and structurally complex history of the massif we present a review of the available stratigraphic evidence and combine it with new isotopic ages from the central and southern parts of the massif to constrain the timing of major tectonic events that shaped the massif since the late proterozoic pt3 in the southern part of the massif sensu stricto three episodes of deformation and metamorphism are distinguished whereas in its northern part there are four the first episode occurred at 500 10 ma with intense deformation and metamorphism at high grade amphibolite facies with local anatexis in the central part of the massif the 470 9 ma old now highly deformed tonalitic and granitic intrusions mark the end of this episode on a cambrian reconstruction of continents around the eastern mediterranean the menderes massif forms the southern end of the pan african orogenic collage of northeastern africa and arabia the area of earliest palaeozoic deformation in the menderes may connect with the northwest african orogenic collage along the strike via the bozburun and saricicek diabases arkoses and schists in the center of the karacahisar dome interpreted herein as fragments of a pan african suture the earliest palaeozoic deformations to affect the rocks were probably related to the last pan african collisions and associated postcollisional convergence the southern part of the massif was undeformed from early ordovician to the early later eocene whereas the northern part was deformed metamorphosed and intruded possibly during the late triassic related to the closure of the karakaya marginal basin of palaeo tethys the next major event affecting the whole of the massif was the intense deformation and widespread metamorphism that reached high amphibolite grade in the structurally lower parts and only greenschist grade in the outermost envelope this metamorphism here called the main menderes metamorphism mmm is biostratigraphically constrained between early eocene and early oligocene time rb sr isotopic data show a spread of ages between 60 ma and 25 ma with the greatest number of determinations around 35 5 ma this number is in excellent agreement with the stratigraphic evidence and shows that mmm took place during latest eocene time or at the transition from eocene to oligocene time along the northern border of the massif deformation and metamorphism had already taken place during the late cretaceous in a high pressure low temperature hp lt metamorphic belt northernmost part of menderes massif sensu lato which was then covered by palaeocene molasse the evolution of the hp lt belt was probably related to the obduction of the bozkir ophiolites from the izmir ankara branch of the neo tethys ocean and preceded terminal collision in the evolution of the massif the mmm was a product of the latest palaeocene collision across neo tethys and the consequent internal imbrication of the menderes taurus block that resulted in the burial of the menderes massif area beneath the lycian nappe complex a low grade metamorphic event dated at 10 to 5 ma is interpreted to be related to the extensional deformation in the aegean and western turkey which has been dated stratigraphically to have begun during the tortonian 11 5 ma

a key extensional metamorphic complex reviewed and restored the menderes massif of western turkey article i nfo this paper provides a review of the structure and metamorphism of the menderes massif in western turkey and subsequently a map view restoration of its neogene unroofing history exhumation of this massif among the largest continental extensional provinces in the world is generally considered to have occurred along extensional detachments with a ne sw stretching direction restoration of the early miocene history however shows that these extensional detachments can only explain part of the exhumation history of the menderes massif and that ne sw stretching can only be held accountable for half or less of the

lacustrine oil shale basins in tertiary grabens from ne spain western european rift system abstract in the ne iberian plate the convergent motion and collision of the european iberian and african plates resulted in the development of paleogene compressional features strike slip systems thrust fold belts and late oligocene to mainly neogene extensional structures which are superimposed on the former these extensional structures are represented by horsts half grabens and tilted blocks often developed in connection with preexisting inherited faults from the late oligocene and during the neogene both strike slip and extensional regimes alternated and coexisted giving rise to a number of fault bounded basins the deposition of organic rich facies and in particular oil shales took place in the lacustrine complexes developed in some of these basins campins basin late oligocene ribesalbes and rubielos de mora basins early middle miocene libros basin late miocene and cerdanya basin late miocene deep lacustrine sequences ranging from 100 up to 250 m thick were deposited in all the above mentioned basins the organic rich sequences are characterized by thin lamination absence of bioturbation rare benthonic fauna if present it is supplied from other parts of the basin and excellent preservation of exotic fossils plant leaves insects amphibians the suitable depth conditions needed for permanent stratification in the water bodies and anoxia in the deeper parts of the lakes were due essentially to increasing subsidence outstripping deposition intense tectonic activity is recorded by the occurrence of olisthostromes and slumps affecting the lacustrine deposits as well as by the syntectonic structures recorded in the basin fill successions the late oligocene late miocene paleoclimatic regimes ranging from warm tropical to subtropical conditions were favourable for the development of permanently stratified lakes moreover chemical ectogenic meromixis may have contributed in some cases to the establishment of permanent stratification the eastern iberian rift system makes up the southernmost part of the larger western european rift system the occurrence of lacustrine sediments ranging from the late eocene to late miocene is frequent in the fault bounded basins of this complex rift system and lacustrine oil shale deposits have been recorded in several of these basins thus the western european rift system presents an interesting model of intracontinental rifting in a foreland platform setting where favourable conditions for organic rich deposits often took place the high potential of this kind of tectonic settings for lacustrine oil shale exploration must be stressed

estimating the magnetization direction of sources from southeast bulgaria through correlation between reduced to the pole and total magnitude anomalies we present a new method to estimate the direction of the magnetization vector of geological bodies based upon the correlation between the reduced to the pole field for tentative values of the magnetization direction and the total magnitude anomaly obtained by a transform of the measured magnetic field the reduced to the pole and the total magnitude anomaly are centred over the sources in the case of 2d anomalies or well centred in the case of compact 3d sources and have similar patterns for the same source the method has several important advantages over similar transform correlation methods for estimation of the magnetization direction it calculates only one transform for many tentative values of the magnetization direction the method does not use derivatives of any order and relies on confident isolation of the target anomalies based on one of the compared transforms the total magnitude anomaly we studied the performance of the method on five 2 5d and compact 3d sources we analysed possible inherent to the method errors as well as errors due to interference from neighbouring sources finally we estimated the magnetization vector direction of the main sources causing the magnetic field in the burgas region and the adjoining southeast bulgarian black sea shelf the sources in the black sea shelf show prevalently reverse magnetization while the sources on land have normal or reverse magnetization

structural lithological and geodynamic controls on geothermal activity in the menderes geothermal province western anatolia turkey western turkey belongs to the regions with the highest geothermal potential in the world resulting in significant electricity production from geothermal resources located predominantly in the menderes massif although geothermal exploitation is increasingly ongoing geological and physical processes leading to the emplacement of geothermal reservoirs are hitherto poorly understood several studies on the menderes massif led to different interpretations of structural controls on the location of hot springs and of the heat source origin this paper describes geological evidence showing how heat is transmitted from the abnormally hot mantle to the geothermal reservoirs on the basis of field studies we suggest that crustal scale low angle normal faults convey hot fluids to the surface and represent the first order control on geothermal systems at the basin scale connected on low angle normal faults kilometric high angle transfer faults are characterized by dilational jogs where fluids may be strongly focused in addition favourable lithologies in the basement e g karstic marble could play a critical role in the localization of geothermal reservoirs finally a compilation of geochemical data at the scale of the menderes massif suggests an important role of the large mantle thermal anomaly which is related to the hellenic subduction heat from shallow asthenospheric mantle is suggested to be conveyed toward the surface by fluid circulation through the low angle faults hence geothermal activity in the menderes massif is not of magmatic origin but rather associated with active extensional tectonics related to the aegean slab dynamics i e slab retreat and tearing

what controls relay ramps and transfer faults within rift zones insights from analogue models abstract structures within rift zones exhibit two main types of interaction relevant at the rift scale relay ramps and transfer faults at high angle to the rift analogue experiments have been performed to investigate whether these types of interaction may be affected by differential extension along the rift in these models sand brittle crust analogue overlies two adjacent silicone ductile crust analogue layers with different viscosity in order to simulate different percentage extension rates e along rifts the experiments show a distinct behaviour as a function of e for e e 21 3 the interaction occurs by means of transfer faults striking subparallel to the extension direction experimental data are consistent with the geometries and extension rates of rift zones relay ramps characterize narrow rifts and oceanic ridges where the mean percentage of extension is low e e 39 where the rift more likely achieves differential extension e 21

intrusion age of pan african augen gneisses in the southern menderes massif and the age of cooling after alpine ductile extensional deformation

the residual water flow through the solent south england summary a reduced equation of motion is used to compute the residual velocity and the residual transport through the west solent from the water levels recorded over an eight month period at tide gauges at either end of the channel a coefficient of bottom friction of 5 0 10 3 is assumed there was a spring neap variation and a significant correlation of fluctuations in the residual velocity with meteorological conditions westward residual velocities occurred at spring tides with low barometric pressure and south westerly winds eastward residual velocities occurred at neap tides with high pressure and north easterly winds because of the progressive nature of the tidal wave the long term residual transport appeared to be towards the west and the flushing time for the solent system was long for considerable periods the maximum velocities experienced during a tidal cycle half way along the channel are towards the west with a probability of values exceeding 160 cm s 1 for 10 min in 5 4 days

active transfer fault zone linking a segmented extensional system betics southern spain insight into heterogeneous extension driven by edge delamination pliocene and quaternary tectonic structures mainly consisting of segmented northwest southeast normal faults and associated seismicity in the central betics do not agree with the transpressive tectonic nature of the africa eurasia plate boundary in the ibero maghrebian region active extensional deformation here is heterogeneous individual segmented normal faults being linked by relay ramps and transfer faults including oblique slip and both dextral and sinistral strike slip faults normal faults extend the hanging wall of an extensional detachment that is the active segment of a complex system of successive wsw directed extensional detachments which have thinned the betic upper crust since middle miocene two areas which are connected by an active 40 km long dextral strike slip transfer fault zone concentrate present day extension both the seismicity distribution and focal mechanisms agree with the position and regime of the observed faults the activity of the transfer zone during middle miocene to present implies a mode of extension which must have remained substantially the same over the entire period thus the mechanisms driving extension should still be operating both the westward migration of the extensional loci and the high asymmetry of the extensional systems can be related to edge delamination below the south iberian margin coupled with roll back under the alboran sea involving the asymmetric westward inflow of asthenospheric material under the margins

crustal scale geometry and kinematics of late orogenic extension in the central aegean cyclades and ewia island abstract the aegean continental domain is known to be the site of widespread back arc extension since at least the middle miocene overprinting structures related to the mesozoic cenozoic hellenic orogeny features attributed to early thrusting include the overall ductile deformation within two broad belts that have suffered hp lt metamorphism across the aegean this study summarizes the results of a structural study in the central aegean area cyclades and evvia island examining in particular the relationship between ductile and brittle deformation on a regional scale extension appears to be responsible for most of the ductile deformation within hp rock units that have experienced penetrative greenschist facies and higher grade metamorphic overprinting on each island studied progressive extensional deformation has occurred through the development of a major normal sense detachment zone down to depths of about 18 25 km the geometry of the extensional system on the scale of the central aegean is described taking into account the characteristic features of the regional scale ductile strain field at least two probably three subparallel major north dipping detachment zones are identified trending nw se in the northwestern cyclades and e w in the southeastern cyclades both with initial dips estimated at around 30 45 the present geometry of the extensional system implies that these detachment zones and related metamorphic core complexes interfere with each other two main evolutionary models are considered which can account for such a kinematic link between parallel detachment zones structural data favour the sequential development of synthetic major detachments zones in a direction opposite to the sense of dip of the detachments early oligocene lower miocene detachment type extension in the area studied is related to a late orogenic post thickening back arc setting

evidence from the gediz graben for episodic two stage extension in western turkey western turkey falls within a wide belt of nne ssw directed active continental extension generally similar to the basin and range province of the usa it comprises a zone of wnw ese trending major grabens detailed study of the gediz graben reveals two contrasting infills that represent two distinct extensional stages separated by a short phase of compression the older infill consists of an 800 m thick folded and exhumed continental sedimentary sequence with intercalated calc alkaline volcanics it accumulated in a basin formed in the northern hanging wall of a detachment fault during miocene early pliocene times the younger infill rests on the older infill with angular unconformity and consists of about 170 m of undeformed terraced continental sediments and basaltic lavas it accumulated during plio quaternary times in an asymmetric graben bounded by step like normal faults this later extension was probably triggered by the commencement of sea floor spreading along the red sea in early pliocene times and has persisted to the present almost all the grabens in western turkey are best explained by this episodic two stage graben model with an intervening phase of short term compression which differs from the progressive evolution inferred for the basin and range province of the usa

behaviour of chromium and chromium isotopes during estuarine mixing in the beaulieu estuary uk abstract rivers are the principal source of chromium cr to seawater and the cr isotopic signatures of ancient marine sediments are widely considered to provide a record of the presence or absence of oxidative weathering processes on land this assumes however that the 53 cr value of river water is faithfully transferred to the oceans and is not modified in the estuarine mixing zone to test this assumption we have determined the concentration and 53 cr values of inorganic cr cr iii cr vi and also cr speciation for water samples collected within the estuarine mixing zone of the beaulieu river uk the 53 cr values of dissolved inorganic cr ranged from 0 59 to 1 68 cr vi concentrations from 0 39 to 1 83 nmol kg 1 and cr iii concentrations from 0 11 to 3 21 nmol kg 1 both cr vi concentrations and 53 cr values increased linearly as a function of salinity while cr iii concentrations decreased linearly with salinity thus 53 cr cr iii and cr vi all showed conservative behaviour in the estuarine mixing zone and the 53 cr signature of beaulieu river water was modified only by mixing between the river and seawater endmembers the calculated average 53 cr value of the river water endmember 0 39 0 08 was however lower than the range that has been observed in other rivers which we attribute to input of organically bound cr iii released by anoxic weathering processes this is supported by the fact that cr recovered by uv irradiation was found to have low 53 cr values 0 11 to 0 75 while input of cr from anoxic weathering processes is unlikely to be an important source of cr to the oceans today this suggests that processes other than oxidative weathering may have an influence on the 53 cr values of estuarine and coastal waters on the local scale the 53 cr value of the coastal seawater endmember 1 6 0 4 was also higher than the range observed in the deep open ocean due to in situ biogeochemical cycling of cr these factors need to be considered in the interpretation of marine sedimentary 53 cr records

investigation of the submarine active tectonism in the gulf of gokova southwest anatolia southeast aegean sea by multi channel seismic reflection data submarine active tectonism in the gulf of gokova located at the southwest anatolia southeast aegean sea region was investigated by means of multi channel seismic reflection data the gokova basin is filled by the latest miocene pliocene quaternary sediments with maximum thickness of about 2 5 km the lycian nappes which predominantly cover extreme southwestern anatolia constitutes the basement rocks for the gokova province the gulf was mainly opened by a buried major listric normal fault so called datca fault which has not been previously discussed in the literature the north dipping mainly e w trending datca fault is located at the southern part of the gulf whereas its associated antithetic faults are located at the north the onset time of the opening of the gulf is possibly in the latest miocene pliocene in terms of local rather than regional effects the activity of the datca fault has decelerated possibly since the pleistocene the datca fault might have gained its curved fault plane as it evolved beginning as planar and or using antecedent planes of the lycian nappes in the area as the extension progressed i e as the hanging wall block slipped further north gravity may have impeded rather than helped the faulting on the other hand continuing extension in the area may have initiated a second phase of faulting i e wnw ese oriented subgrabens in the gulf and major e w normal faulting in the northeast margin a bathymetric low in the mid gulf area and a horst graben system in the eastern part of the gulf are observable from the bathymetric data and are well correlated to the seismic data although the main orientation of the gulf is e w more recent wnw ese structures are remarkable in the mid gulf and in the eastern part of the gulf the latest wnw ese structures are also in agreement with the results of gps and slr studies as well as plate motion modelling by total moment tensor of earthquakes in the western anatolia aegean sea region particularly in southwestern anatolia the amount of total n s extension within the gulf is estimated as at least 5 5 km since the latest miocene pliocene with overall constant extension rate of at least 1 1 mm y where the estimated extension factor is about 1 3

hydrocarbon occurrences in the western anatolian aegean grabens turkey is there a working petroleum system western anatolian graben basins are filled with continental sediments and minor carbonates deposited in lacustrine alluvial and fluvial environments individual grabens are composite basins and comprise multiple depocenters or subbasins with sediment thickness rarely exceeding 3000 m 9843 ft a number of hydrocarbon occurrences are reported from the basins regional geologic framework justifies these occurrences by providing a generous heat budget good quality source rock fair reservoir seal sequences and suitable traps although no economically producible reserves have been discovered to date the rich source rock with an average total organic carbon of 2 34 and hydrogen index up to 800 mg g is oil and gas generative at maturation however the composite nature of the grabens controlled the stratigraphic variability and led to sporadic distribution of the lacustrine deposits hosting the source rock facies in the basins the depth of burial is generally insufficient 2000 m 6562 ft for the source rock to effectively generate and expel hydrocarbons this limitation was locally overcome by additional heat input into the system through deep reaching faults volcanism and or after volcanic hydrothermal circulation thermal maturity of organic matter effectively increases in the vicinity of the major border structures volcanic rocks and zones of polymetallic mineralization yet this effect is typically constrained within a narrow zone adjacent to heat source and diminishes within short distances thus the hydrocarbon system remains regionally inefficient exploration success in the region depends on the discovery of deeper neogene depocenters that could provide sufficient source rock burial depths

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

evidence for right lateral transfer faulting accommodating en echelon miocene extension mojave desert california in the southwestern united states two early miocene extensional terranes one along the colorado river trough and the other in the central mojave desert have been inferred to be part of an en echelon rift system linked by a ductile detachment at depth evidence from pre tertiary surface geology in the central and western mojave desert suggests that a zone of east to northeast trending right lateral strike slip faulting may have transferred extension between these two areas these data include the apparent offsets of the late jurassic age independence dike swarm a middle to late jurassic age deformation belt triassic jurassic volcanic rocks lower triassic sedimentary rocks and late paleozoic age stratigraphic and tectonic elements this inferred fault zone probably served as the main shallow crustal kinematic link between extension in the central mojave desert and in the colorado river trough

processes of late cretaceous to late miocene episodic thrust sheet translation in the lycian taurides sw turkey the lycian taurides of sw turkey consist of an allochthonous mesozoic passive margin succession that was episodically detached from its autochthon and translated southeastwards between latest cretaceous to late miocene times a combination of structural analysis sedimentology palaeontology and geochemistry allows subdivision of this orogenic event into 1 latest cretaceous trench passive margin collision causing ophiolite obduction and detachment of the koycegyiz thrust sheet 2 mid late eocene continent continent collision renewing southeastwards thrusting and causing detachment of the teke dere thrust sheet and yavus thrust sheets 3 miocene extensional collapse of the orogen with southeastwards translation of the allochthon coeval with rift basin formation in the hinterland

tectonic denudation of a late cretaceous tertiary collisional belt regionally symmetric cooling patterns and their relation to extensional faults in the anatolide belt of western turkey t hermochronological data reveal that the late cretaceous tertiary nappe pile of the anatolide belt of western turkey displays a two stage cooling history three crustal segments differing in structure and cooling history have been identified the central menderes metamorphic core complex represents an inner axial segment of the anatolide belt and exposes the lowest structural levels of the nappe pile whereas the two outer submassifs the g ordes submassif to the north and the ci ne submassif to the south represent higher levels of the nappe pile a regionally significant phase of cooling in the late oligocene and early miocene affected the outer two submassifs and the upper structural levels of the central menderes metamorphic core complex in the northern part of the g ordes submassif cooling was related to top to the nne movement on the simav detachment as the apatite fission track ages show a northward younging trend in the direction of movement on this detachment in the ci ne submassif relatively rapid cooling in late oligocene and early miocene times may have been related to top to the s extensional reactivation of the basal thrust of the overlying lycian nappes the second phase of cooling in the anatolide belt is related to pliocene to recent extension resulting in the formation of the central menderes metamorphic core complex in the inner part of the anatolide belt core complex development caused the formation of supra detachment graben which document the ongoing separation of the central menderes metamorphic core complex from the outer submassifs

complete tertiary exhumation history of the menderes massif western turkey an alternative working hypothesis the main exhumation of the menderes massif western turkey occurred along an originally n dipping datca kale main breakaway fault that controlled depositions in the kale and the gokova basins during the oligocene early miocene interval the isostatically controlled upward bending of the main breakaway fault brings the lower plate rocks to the surface in the early miocene e w trending n and s dipping graben bounding faults fragmented the exhumed dome shaped massif the development of half grabens by rolling master fault hinges has allowed further exhumation of the central menderes massif after the pliocene high angle normal faults cut all of the previous structures this model suggests that the menderes massif is a single large metamorphic core complex that has experienced a two stage exhumation process

tectonic evolution of the intra uplift vigodi gugriana khirasra netra fault system in the seismically active kachchh rift basin india implications for the western continental margin of the indian plate abstract the e w striking kachchh rift basin krb at the western continental margin of indian plate is located in the northern part of gujarat state india krb has undergone polyphase deformation owing to changing stress field since late triassic we establish the kinematic framework along the nw striking intra uplift vigodi gugriana khirasra netra fault system vgknfs located at the western part of the krb the vgknfs consists of 0 25 50 km long sub parallel striated reactivated dip slip faults a total of 1150 fault slip data consisting of fault planes and striations attitude were recorded from 66 sites including a single site with systematic joints slip sense of faults was determined by documenting kinematic indicators paleostress analysis was carried out using win tensor t tecto faultkin and sg2ps to compare and validate the results the chi square statistical analysis was undertaken to evaluate how relevant are paleostress analysis results to the present day compressional stress field geophysical investigations were conducted at selected sites using ground penetrating radar gpr to understand the shallow subsurface geometry and trace the continuity of faults buried below patchy alluvial cover 15 17 m long 2d gpr cross sections were recorded across faults using monostatic antenna of 200 mhz frequency two major deformation events d1 and d2 are determined in the present study the extension event d1 shows w and nw nnw extension during late triassic to late cretaceous it occurred during the rift phase of krb in response of the break up of gondwanaland the latest event d2 shows nne ne compression from late cretaceous up to the present it is interpreted to have developed during post rift inversion phase induced by collision of the indian plate with the eurasian plate at 55 ma

a stress inversion method requiring only fault slip sense in numerous cases the use of standard methods of palaeostress inversion from fault slip data is prevented by the absence of structures that indicate the direction of slip on the fault in such instances however the offset of planar markers such as beds matched in the footwall and hanging wall often allows the sense of dip separation normal or reverse to be observed where such displaced markers are horizontal or at least where their cut off lines are horizontal it can be readily demonstrated that the sense of the dip slip component of net slip is the same as the sense of dip separation ways are explored for characterizing the stress tensor from data consisting of the orientations of a collection of faults each with known dip slip sense normal or reverse on the basis of properties of the stress quadric the relationship between dip slip sense fault plane orientation and the stress tensor is discovered this relationship is used as the basis of a grid search method of stress inversion in which a large number of stress tensors differing in orientation and shape are systematically considered those tensors that successfully explain the senses of offset on the observed faults are considered potential solutions to the palaeostress problem examples of different applications of the new stress inversion method are described including the analysis of fault data from boreholes these examples illustrate the way the new method potentially broadens the scope of palaeostress analysis

stratigraphic and metamorphic inversions in the central menderes massif a new structural model the menderes massif is a large area of dominantly tertiary metamorphic rocks in western turkey it is bordered in the west by the cycladic metamorphic complex with eocene high pressure low temperature hp lt metamorphism in the central menderes the aydin mountains are made up of a thrust stack of eocene age at the base of the thrust stack greenschist facies paleozoic metasediments of the menderes massif form an inverted stratigraphic sequence the barrovian type metamorphism is also inverted with garnet bearing metapelites lying over the lower grade biotite bearing metapelites the p t conditions in the garnet zone are estimated as 530 c and 8 kbar this schist sequence of the central menderes massif is interpreted as the inverted lower limb of a major southward closing recumbent fold with the southern menderes massif representing a section from the near hinge of this fold the paleozoic metamorphic rocks of the central menderes massif are tectonically overlain by gneiss klippen possibly originating from the sheared and southward translated core of the menderes fold lying also tectonically over the paleozoic metamorphic rocks is a major thrust sheet belonging to the cycladic metamorphic complex it consists of garnet micaschist mesozoic marble serpentinite and amphibolitised eclogite although it has a highly sheared internal structure it probably represents an initially coherent sequence that has undergone hp lt metamorphism during the eocene the aydin mountains are dominated by contractional structures with subordinate extensional structures

late orogenic crustal extension in the northern menderes massif western turkey evidence for metamorphic core complex formation the simav metamorphic core complex of the northern menderes massif western turkey consists of a plutonic tertiary and metamorphic precambrian core footwall separated from an allochthonous cover sequence hanging wall by a low angle ductile to brittle extensional fault zone i e detachment fault the core rocks below the detachment fault are converted into mylonites with a thickness of a few hundred metres two main deformation events have affected the core rocks the first deformational event d1 was developed within the precambrian metamorphic rocks the second event d2 associated with the tertiary crustal extension includes two distinct stages stage one is the formation of a variably developed ductile mylonitic deformation d2d in metamorphic and granitic core rocks under greenschist facies conditions the majority of the mylonites in the study area have foliations that strike nnw to nne and dip sw to se stretched quartz and feldspar grains define the mineral lineation trending sw ne direction and plunging gently to sw the kinematic indicators indicate a top to ne sense of shear stage two formation of brittle deformation d2b that affected all core and cover rocks d2b involves the development of cataclasites and high angle normal faults an overall top towards the north sense of shear for the ductile mylonitic fabrics in the core rocks is consistent with the n s regional extension in western turkey

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

strains at the intersections of synchronous conjugate normal faults abstract processes accommodating the mutual offsetting of intersecting conjugate faults are investigated by outcrop examination of three pairs of conjugate normal faults with maximum throws from 5 mm to 10 cm in two cases resolved fault throws decrease sharply towards the intersection zones which on the scale of observation are zones of ductile thinning of inter fault layers that accommodate the throw reductions strain within the intersection zone of conjugate faults in fluvio glacial sands is accommodated by inter grain slip and layer thinning is complemented by layer parallel extension at constant volume in a second example strain within the intersection zone of conjugate faults in inter layered chalk and marl is accommodated by volume reduction without layer extension in a third example also in fluvio glacial sands strain in the intersection zone is accommodated by small faults throws 1 mm when throws on all resolvable faults are aggregated there is no decrease in throw towards the conjugate intersection the presence or absence of a decrease in resolved throw towards conjugate intersections and of a complementary ductile zone accommodating the change in throw is a function not only of the resolution limit of the observations but also of the scale of the deformation process within the conjugate zone

comprehensive approaches to 3d inversion of magnetic data affected by remanent magnetization three dimensional 3d inversion of magnetic data to recover a distribution of magnetic susceptibility has been successfullyusedformineralexplorationduringthelastdecade however the unknown direction of magnetization has limited the use of this technique when significant remanence is present we have developed a comprehensive methodology for solving this problem by examining two classes of approaches and have formulated a suite of methods of practical utility the first class focuses on estimating total magnetization direction and then incorporating the resultant direction into an inversion algorithm that assumes a known direction thesecondclassfocusesondirectinversionoftheamplitude of the magnetic anomaly vector amplitude data depend weaklyuponmagnetizationdirectionandareamenabletodirect inversion for the magnitude of magnetization vector in 3d subsurface two sets of high resolution aeromagnetic dataacquiredfordiamondexplorationinthecanadianarctic areusedtoillustratethemethods usefulness

sediment thicknesses of the western anatolia graben structures determined by 2d and 3d analysis using gravity data abstract western turkey is tectonically one of the most active and rapidly deforming regions of continental crust in the world the most pronounced structural and morphological features of this region are defined by normal faulting in an e w direction which creates the boundaries of the buyuk menderes kucuk menderes and gediz grabens the graben systems may have become active between 11 7 ma and are now deeper than the surrounding topography the gediz and buyuk menderes grabens exhibit negative bouguer gravity anomalies the bouguer gravity anomalies increase towards the center of the aegean sea in a regional sense the grabens are filled with recent sediments giving rise to relative negative gravity anomalies these anomalies were interpreted using 2d and 3d gravity inversion techniques in order to determine the depth to the metamorphic basement inversion of geophysical anomalies implies fitting the observed data to theoretical anomalies possibly produced by subsurface bodies inversion of gravity anomalies is a non linear problem in the sense that body parameters are not linearly related to the anomalies gravity anomalies caused by structures are mostly determined by a 2d model which has an n sided polygonal cross section for non linear problems theoretically it is more suitable to determine the parameters of the structure by a series of juxtaposing prisms or vertical dykes extending to infinity rather than using a single n side polygonal model the depths to the top surfaces of a rectangular prisms with infinite depth represent the relief of the basement the basement relief can be computed on the basis of density contrast if the reference depth is assessed as a result of 3d analysis of the bouguer gravity map the maximum thickness of sedimentary cover appears to be more than 2 0 and 1 5 km for the gediz and buyuk menderes grabens respectively towards the saraykoy kizildere area the sedimentary thickness cover thickens to more than 2 0 km 2d analysis of the bouguer gravity profiles indicate that the maximum thickness of the sedimentary cover is between 2 5 and 3 5 km in the buyuk menderes graben and between 0 5 and 2 0 km in the gediz graben

metamorphic history of the southern menderes massif western turkey metamorphic mineral compositions and textures are integrated with microstructures to test tectonic models for the construction and exhumation of a mid crustal terrane in western turkey the southern menderes massif part of the alpine orogen is composed of a tilted sequence of metasedimentary rocks that structurally overlies orthogneiss garnet biotite equilibria for schists collected along north south traverses consistently indicate temperatures of 430 c for the southernmost structurally highest garnet bearing rocks 500 c for structurally intermediate rocks and 550 c for the structurally deepest rocks near the contact with the orthogneiss there are no detectable discontinuities in metamorphic grade from north to south within the schist unit or between the schist and overlying lower grade and underlying higher grade rocks pressure estimates are less certain geobarometric results for the schists yield p 8 kbar but mineral assemblages and structural data are consistent with lower pressures 6 kbar metamorphic textures and garnet zoning in the menderes schists indicate metamorphism during a single thermal event accompanying development of the main penetrative foliation top to north fabrics formed during folding thrusting and were synkinematic with garnet growth top to south chloritic shear bands truncate the earlier foliation and overprint peak metamorphic assemblages and textures we propose that these metamorphic features and structures indicate synmetamorphic shortening followed by extension during alpine orogenesis

estuarine mixing of clay minerals in the solent region southern england the clay mineral composition of the fine fraction the spatial distribution of clay minerals in the region is shown to be due to estuarine mixing processes riverine input from the rivers itchen test and hamble is characterized by high smectite content and a low kaolinite chlorite to illite ratio this input is believed to contain a substantial contribution of clay minerals derived from the chalk these fluvially derived clay minerals are mixed with a second clay mineral suite of marine origin containing lower smectite and a higher kaolinite chlorite to illite ratio the clay minerals in the marine suite are believed to be derived mainly from tertiary and or recent sediments by the reworking of bed material within the estuaries or by tidal current and wave erosion of coastal outcrops mixing between these two sources occurs as a result of estuarine circulation dynamics

late cenozoic tectono sedimentary development of the selendi and usak gure basins a contribution to the discussion on the development of east west and north trending basins in western turkey

sedimentation of the neogene recent alasehir gediz continental graben system used to test alternative tectonic models for western aegean turkey abstract the alasehir gediz graben exemplifies clastic sedimentation in a long lived continental half graben in a semi arid setting developed within relatively incompetent metamorphic rocks early miocene to recent rift related sediments are exhumed on both flanks of the graben allowing detailed three dimensional study during the early miocene small fan delta lobes were shed northwards from the rugged menderes metamorphic massif into a bordering lacustrine basin during early to mid miocene time large alluvial fans prograded northwards into this basin through drainage to the aegean sea was established as the basin widened and filled discrete lobes of coarse alluvial fan sediments of latest miocene pliocene age also shedding northwards are likely to have been climatically influenced quaternary alluvium party infills the modern alasehir rift basin the sedimentary information can be used to test two alternative tectonic models for the alasehir graben in the first model an e w graben bounded by high angle faults was active during latest miocene recent time whereas earlier miocene sedimentation was controlled by n s faulting related to a n s compressional stress regime in the second hypothesis the alasehir graben was initiated much earlier in the early miocene and was then either continuously or episodically active until recent our results especially facies and palaeocurrent data from alluvial sediments indicate that clastic sedimentation was controlled by mainly e w faulting in a n s stress regime assuming the early miocene clastic sediments are correctly dated this supports the second long lived extension model however rather than steady state extension for ca 15 ma the sedimentary evidence and regional context are consistent with a pulsed extension model whereby initial early to mid miocene extension and related clastic sedimentation was followed by a second phase of extension in latest miocene pliocene time the driving force of initial early miocene extension was probably gravity spreading towards a south aegean subduction zone whereas the inferred second extension pulse is seen as being triggered by westward tectonic escape of anatolia towards the extending aegean back arc region

paleomagnetism of line islands seamounts evidence for late cretaceous and early tertiary volcanism seamount magnetic anomaly studies have been conducted on eight volcanoes in the line islands seamount chain the magnetic anomalies of these seamounts were inverted to obtain paleomagnetic information four of these gave paleomagnetic pole positions consistent with other pacific cretaceous pole positions of these three have reliable radiometric ages ranging from 72 to 85 ma the remaining four seamounts gave geomagnetic poles that agree with other eocene early oligocene pacific paleomagnetic data and one has a reliable radiometric age of 39 ma all of the apparently eocene volcanoes occur in the central line islands between 8 n and 3 s we suggest that the eocene volcanic event was approximately coincident with the profound change in pacific plate motion recorded by the bend in the hawaiian emperor seamount chain that occurred at approximately 43 ma this volcanism may have resulted from the large change in intraplate stress accompanying the change of plate motion the change in stress might have pulled apart a zone of weakness caused by the original formation of the line islands detailed paleomagnetic modeling of the line islands seamounts was necessary to obtain good results as seven of the eight seamounts appear to be inhomogeneously magnetized to some extent despite these inhomogeneities the high goodness of fit parameters and the excellent agreement of these results with other pacific paleomagnetic data suggest that the paleopoles derived from these seamounts are reliably determined

a study of fuzzy c means coupling for joint inversion using seismic tomography and gravity data test scenarios abstractjoint inversion the inversion of multiple geophysical data sets containing complementary information about the subsurface has the potential to significantly improve inversion results by reducing the nonuniqueness of the inverse problem one of the challenges of joint inversion is deciding how to couple the multiple physical property models if a coupling approach is used that is inconsistent with the physical truth then inversion artifacts can occur and may lead to incorrect interpretations in this paper we investigated the fuzzy c means fcm clustering approach to provide a lithological coupling of the seismic velocity and density models in joint 2d inversions of first arrival traveltimes and gravity data even though this coupling approach has been used in previous works recommendations for its effective use have not yet been developed we conducted a suite of joint inversion tests on synthetic data generated from a geologically realistic model based on magmatic massive sulfide deposits

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

fault kinematics in supradetachment basin formation menderes core complex of western turkey abstract the neogene alasehir supradetachment basin in western turkey occurs in the footwall of the modern alasehir gediz graben and is a major component of the aegean extensional province in anatolia that developed during the late cenozoic exhumation of the menderes core complex the size geometry accommodation space and internal structure stratigraphy of this basin were strongly controlled by the kinematics and interplay of four different fault generations throughout its early miocene pleistocene evolution the e w striking nne dipping 10 30 alasehir detachment fault separates the high grade crystalline rocks of the core complex below from the neogene deposits of the basin in the hanging wall above the basin parallel synthetic and antithetic high angle normal faults represent a block faulting stage of the continued horizontal extension that terminated the northerly slip along the detachment surface and produced horst graben structures in and across the basin these faults were also responsible for the back tilting of the basinal strata into steeper dips and the rotation of the previously formed faults into gently dipping planes the mutually crosscutting relationships between the intra basinal low angle and basement involved high angle and normal faults indicate their contemporaneous development and operation the nne striking basin perpendicular oblique slip hinge faults are reminiscent of transfer cross faults in both continental and oceanic extension and divide the supradetachment basin into a series of fault blocks with their own internal structure and stratigraphy differential uplift and exhumation of the core complex rocks along these hinge faults and the varied displacement and slip along and across them within the basinal strata caused differential extension and block uplift leading to the formation of local unconformities in the supradetachment basin significant changes in the dip directions and strike orientations of the sedimentary beds and the observed deviations from the inferred direction of maximum extension in the adjacent fault blocks resulted from rotational deformation due to hinge faulting fault segmentation of the alasehir basin as a result of extension parallel hinge faulting is a characteristic feature of its supradetachment basin evolution

precise u pb ages of syn extensional miocene intrusions in the central menderes massif western turkey western turkey is an area which has experienced large scale extension of continental crust here we report precise crystallization ages of two intrusions in the central menderes massif the turgutlu and salihli granodiorites using u pb dating both intrusions occur in the southern footwall of the seismically active alasehir graben and were emplaced syntectonically in an extensional top to the nne shear zone which was active at retrograde greenschist facies conditions the u pb ages of 16 1 0 2 ma monazite turgutlu granodiorite and 15 0 0 3 ma allanite salihli granodiorite document that tectonic exhumation of middle crustal rocks in the central menderes massif was already underway at the early to middle miocene transition combined with published geochronological structural and sedimentological data the new u pb ages point to a continued extension since at least 16 ma there is no convincing evidence for a late miocene pliocene phase of tectonic shortening

the historical development of the magnetic method in exploration the magnetic method perhaps the oldest of geophysical exploration techniques blossomed after the advent of airborne surveys in world war ii with improvements in instrumentation navigation and platform compensation it is now possible to map the entire crustal section at a variety of scales from strongly magnetic basement at regional scale to weakly magnetic sedimentary contacts at local scale methods of data filtering display and interpretation have also advanced especially with the availability of low cost high performance personal computers and color raster graphics the magnetic method is the primary exploration tool in the search for minerals in other arenas the magnetic method has evolved from its sole use for mapping basement structure to include a wide range of new applications such as locating intrasedimentary faults defining subtle lithologic contacts mapping salt domes in weakly magnetic sediments and better defining targets through 3d inversion these new applications have increased the method s utility in all realms of exploration in the search for minerals oil and gas geothermal resources and groundwater and for a variety of other purposes such as natural hazards assessment mapping impact structures and engineering and environmental studies

ductile brittle transition along the alasehir detachment fault and its structural relationship with the simav detachment fault menderes massif western turkey abstract western turkey has experienced extensional deformation since the tertiary an early phase of extensional deformation resulted in the formation of detachment faults in the northern part of the menderes massif the alasehir and simav detachment faults the footwalls of these two detachment faults are mid crustal level rocks the alasehir detachment fault developed in metamorphic rocks and in a syn extensional intrusion the salihli granodiorite the salihli granodiorite shows a gradual change from undeformed isotropic granodiorite to protomylonite mylonite and ultramylonite towards its upper structural levels the deformed granodiorite in turn grades into a cataclastic zone whose uppermost part is the alasehir detachment surface this gradual upward change from the undeformed granodiorite to a brittlely deformed detachment surface suggests that tertiary extension resulted in a ductile deformation at depth and the ductilely deformed granitoids were brought to shallower depths where they were brittlely deformed the metamorphic wall rocks of the intrusion are also mylonitized structurally upward a similar transition has also been found in the footwall of the simav detachment fault the upper part of which is also a cataclastic zone leading to the simav detachment fault separating the low grade metamorphic rocks and or non metamorphic rocks in its hanging wall from mainly high grade metamorphic rocks and syn tectonic granitoids in its footwall during ductile extension greenschist facies grade mylonitic deformation developed in the metamorphic rocks and the granitoids shear sense indicators along the two shear zones show top to n ne sense shear consistent with the regional cenozoic extension direction in western turkey available radiometric age data from the granitoids in the footwall of the two detachment faults suggest that the cenozoic extension in western turkey was initiated in oligocene to early miocene and the simav detachment fault is older than the alasehir detachment fault extensional features of these detachment faults suggest that the simav detachment fault characterise the earlier stage of the tertiary extensional tectonics of the menderes massif and later stage of this deformation resulted in the development of the alasehir detachment fault

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

multistage exhumation of the menderes massif western anatolia turkey structural analyses along selected transects across the menderes massif and incorporation of existing data have resulted in a synthetic cross section across southwestern turkey the tectonic interpretation has been combined with 40ar 39ar laser probe experiments on two syn kinematic white mica populations which respectively predate and overprint documented early miocene deformational fabrics our results indicate that the regional extension had initiated by eocene oligocene times a 36 2 ma 40ar 39ar age derived from white mica which formed during a regionally observed northward directed tectonic transport suggests that the extension was contemporaneous with the tectonic emplacement of mid crustal continental basement alternatively the age may relate to the regional cooling of the basement sequence and thus postdates the tectonic emplacement in the latter scenario the analysis fails to solve the present ambiguity on the pan african or alpine affinity of the northward directed transport further exhumation of basement rocks is characterized by a dominant displacement along the north dipping gediz detachment at the northern margin of the massif which developed under ductile conditions in the early miocene by partial exploitation of older zones of weakness which originated from an earlier phase of basement emplacement youngest semi ductile activity along the gediz detachment has been recorded as having a 7 1 ma 40ar 39ar age derived from syn kinematic white mica in the top of the detachment following the initiation of the ductile gediz detachment an antithetic semibrittle and south dipping buyuk menderes detachment had developed in the center of the massif which together with the gediz detachment accommodated further doming of the central part of the menderes massif and controlled the architecture of the surrounding supradetachment basins

the coso geothermal field a nascent metamorphic core complex investigation of the coso range using seismicity gravity and geochemistry of rocks and fluids supports the interpretation that the structure hosting the geothermal resource is a nascent metamorphic core complex the structural setting is a releasing bend in a dextral strike slip system that extends from the indian wells valley northward into the owens valley this tectonic setting results in nw directed transtension which is accommodated by normal and strike slip faulting of the brittle upper 4 6 km of the crust and shearing and ductile stretching below this depth accompanied by shallow igneous intrusions focal mechanisms of some small earthquakes that have occurred from 1996 to the present beneath the coso range exhibit depth dependent rotation of seismic p and t axes indicating that the local orientations of the principal stresses likely favor resolved shear stress on low angle faults these small earthquakes occur near the base of seismicity which we interpret as coincident with the brittle ductile transition geochemical results show a significant asthenospheric influence in the isotopic composition of rocks and fluids indicating that the crust is thinned within the coso structure thinned upper crust is underlain by a more dense mafic body at depths of 10 km or less this is consistent with observed gravity anomalies and models the mafic body may represent cumulates left over from the fractional crystallization of rhyolite which occurs as endogenous domes at coso or it could be a sheeted dike complex in the upper mid crustal area transtension began at 2 3 ma and continues today using a long term crustal deformation rate of 2 mm yr we infer that the basal detachment fault commonly observed in fully exhumed metamorphic core complexes will reach the surface in two to four million years