geochemical and geochronological evidence for early triassic calc alkaline magmatism in the menderes massif western turkey pan african basement rocks and a paleozoic cover series which were intruded by the protoliths of leucocratic orthogneisses have been recognized in the menderes massif located in the western part of the alpine orogenic belt of turkey this geochemical and geochronological study focuses on the evolution of the menderes massif at the end of paleozoic time geochemical data suggest that the crustally derived leucocratic orthogneisses have chemical composition typical of calc alkaline and s type granite zircon grains which are euhedral with typical igneous morphologies were dated by the 207pb 206pb evaporation method single zircon dating of three samples yielded mean 207pb 206pb ages of 246 5 241 5 and 235 6 ma these ages are interpreted as the time of protolith emplacement in triassic geological and geochronological data suggest that leucocratic granites were emplaced in a period following a metamorphic event related to the closure of the paleo tethys the leucocratic granites were metamorphosed during the alpine orogenesis and transformed into orthogneisses the similar triassic magmatic event at 233 2 ma was also occurred using single zircon evaporation method from granitic gneisses which rest upon the migmatites with tectonic contacts in naxos cycladic complex this indicates that the menderes massif and cycladic complex had a common pre early triassic magmatic evolution

first evidence of high pressure metamorphism in the cover series of the southern menderes massif tectonic and metamorphic implications for the evolution of sw turkey abstract the menderes massif occupies a large part of western turkey it is tectonically overlain by nappes of the izmir ankara suture zone including the bornova flysch zone on its northern flank the afyon zone on its eastern border and the lycian nappes on its southern flank the discovery of magnesiocarpholite kyanite assemblages in the mesozoic cover sequence of the southern menderes massif leads to the very first consideration that a major high pressure hp metamorphic event affected the massif during its alpine evolution estimations of minimum pressure temperature conditions about 10 12 kbar and 440 c suggest a minimum burial of 30 km for the metasedimentary rocks of the menderes massif similar to that for the eocene dilek blueschists which belong to the cycladic complex this finding of high pressure rocks within the menderes cover series as well as the recent description of low grade high pressure parageneses in the basal thrust sheets of the overlying lycian nappe complex has strong implications for the tectono metamorphic evolution of these units the characteristics of this high pressure metamorphism and the deformation features observed in the southern menderes massif allow consideration of a fast burial during alpine subduction and nappe stacking three high pressure units were piled up during the eocene collision of the sakarya continent and the tauride menderes block the lowermost unit consists of the imbricated core and cover of the menderes massif the intermediate unit is the cycladic blueschist complex dilek and samos regions and the uppermost unit is made of the lycian nappes the retrogression of high pressure parageneses from the menderes massif follows an isothermal decompression path and the associated deformation is characterized by a severe stretching oriented n s to ne sw during the high pressure event and its exhumation we propose a tectono metamorphic model in three main stages 1 the southward translation of the high pressure lycian nappes and the burial of the menderes and cycladic metasediments to a depth of at least 30 km to allow their eocene high pressure metamorphism 2 a northward continuum of deformation responsible for top to the north fabrics associated with the main menderes metamorphism peak paleocene eocene and its progressive cooling late eocene north verging folding thrusting imbrication of core and cover series and n s to ne sw intense stretching associated with the menderes high pressure metamorphism and its exhumation these top to the north to top to the northeast movements are probably related to the northward backthrusting of the lycian nappes reactivating the contact between the menderes massif and the lycian nappes as a top to the ne shear zone that allowed exhumation of the lycian high pressure rocks 3 oligo miocene n s extension during which the final exhumation of the metamorphic rocks along kilometre scale low angle detachments occurred

the evolution of the southern menderes massif in sw turkey as revealed by zircon dating this geochronological study concentrates on the evolution of the southern part of the menderes massif a metamorphic core complex in w turkey by dating single zircons with the pb pb evaporation and the u pb methods we have analysed zircons from granitic augen gneisses of the core as well as from quartzites of the metasedimentary envelope zircons from the granitic core gneisses are euhedral with typical igneous morphologies the single zircon ages of these gneisses indicate a time span for magmatic activity from 520 to 570 ma with a major event at about 550 ma some gneisses contain older zircons of c 660 ma which are interpreted as inherited grains zircons from the quartzites are detrital as indicated by their rounded shapes and pitted surfaces their ages vary from 526 to 2094 ma these data partially coincide with the ages of the gneisses but also indicate an older source region for the sediments neither a tertiary origin nor metamorphic overgrowth is documented in the pb ages of the zircons the results suggest that the southern part of the menderes massif developed during a major magmatic episode in latest proterozoic times thus suggesting a relation with other pan african regions in n africa

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

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

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

exhumation paths of high pressure low temperature metamorphic rocks from the lycian nappes and the menderes massif sw turkey a multi equilibrium approach the menderes massif and the overlying lycian nappes occupy an extensive area of sw turkey where high pressure low temperature metamorphic rocks occur precise retrograde p t paths reflecting the tectonic mechanisms responsible for the exhumation of these highpressure low temperature rocks can be constrained with multiequilibrium p testimatesrelyingonlocalequilibria whereasasimple isothermal decompression is documented for the exhumation of highpressure parageneses from the southern menderes massif various p t paths are observed in the overlying karaova formation of the lycian nappes in the uppermost levels of this unit far from the contact with the menderes massif all p t estimates depict cooling decompression paths these high pressure cooling paths are asso

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

garnet and associated minerals in the southern margin of the menderes massif southwest turkey assemblages with muscovite quartz show a regular increase in grade from the chlorite zone at the base of the lycian nappe complex to the garnet zone within the structurally underlying menderes massif biotite enters before garnet which precedes oligoclase garnet bearing assemblages in pelites are compared with those in re equilibrated quartzofeldspathic gneisses where garnet is unusually calcic in one case approaching gross 50 alm 50 garnet zoning with mn decreasing outwards is interpreted as growth zoning ca decreases outwards in pelite garnets but shows the reverse effect in the gneisses chloritoid is common but rarely coexists with biotite and garnet chlorite paragonite is found rather than chloritoid albite garnet biotite geothermometry corrected for the effect of ca in garnets with up to 29 mole grossular indicates temperatures of 530 or 50 degrees c near the garnet isograd muscovite paragonite geothermometry gives an anomalous result metamorphic pressure is considered in the light of i mn fe partition between garnet and biotite ii ca content of garnet coexisting with plagioclase muscovite biotite iii na in actinolite coexisting with albite chlorite magnetite and iv celadonite content of muscovite which however shows variation due to disequilibrium within a specimen and does not provide an accurate geobarometer comparisons with published studies indicate a strong similarity to the barrovian dalradian of scotland and lead to a tentative pressure estimate of approximately 5 kbar modified journal abstract

how to resist subduction evidence for large scale out of sequence thrusting during eocene collision in western turkey significant along strike variations have locked large parts of the alpine subduction complex in the eastern mediterranean in the eocene and defined the end of high pressure accretion in western turkey structural analysis reveals that the anatolide belt in western turkey formed under greenschist facies metamorphic conditions in the eocene when a high pressure metamorphic fragment of the adriatic plate the cycladic blueschist unit was thrust onto the imbricated mid crustal units of the anatolian microcontinent the menderes nappes the contact between the cycladic blueschist unit and the menderes nappes the cyclades menderes thrust represents an out of sequence ramp which cuts up section towards the south the lack of alpine high pressure fabrics below the cyclades menderes thrust implies c 35 km of exhumation of the cycladic blueschist prior to its eocene emplacement on top of the menderes nappes structure and geodynamic evolution of the anatolide belt are in striking contrast to the neighbouring aegean and contradict the model of a laterally continuous orogenic zone in which the anatolide microcontinent is interpreted as an eastern extension of the adriatic plate

geochemical evidence for the tectonic setting of the harmancik ophiolites nw turkey abstract the harmancik orhaneli and tavsanli ophiolites of nw turkey are remnants of oceanic lithosphere formed in the neo tethys during the mesozoic these ophiolites constitute part of the izmir ankara suture zone which separates the pontides to the north from the anatolides and taurides to the south the harmancik area includes a metamorphic basement ophiolitic melange peridotite dunite harzburgite serpentinized peridotite doleritic dykes and neogene cover sediments metamorphic rocks in the harmancik area are psammites pelites and marbles metamorphosed under blueschist facies conditions they are overlain tectonically by peridotites cut by basic dykes the dykes are dolerites and based on texture and mineralogy can be divided into three petrographic groups coarse medium grained and porphyritic these groups have similar chemical compositions with respect to major trace and ree elements when plotted on a basalt discrimination diagram the dykes plot in the iat island arc tholeiite field and are considered to have been intruded during subduction zone magmatism chondrite normalized ree patterns for the dykes are eu depleted similar to patterns for the mean dolerite composition of the ne anatolian ophiolites and are slightly lree enriched our results suggest that the harmancik ophiolite is a supra subduction zone ophiolite on which a volcanic arc sequence was built and that the dolerite dykes were formed by the partial melting of the underlying mantle

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

origin and evolution of the thermal waters from the pamukkale geothermal field denizli basin sw anatolia turkey insights from hydrogeochemistry and geothermometry abstract the pamukkale geothermal field pgf of the denizli basin sw turkey is one of the most distinguished active geothermal fields known in the world the thermal waters from the pgf are subdivided into two groups group 1a ca hco3 and group 1b ca so4 types the cold waters are also classified into two groups group 2a ca hco3 and group 2b mg hco3 types the hydrogeochemical properties of the pgf thermal waters suggest interactions with the basal metamorphic rocks of the menderes massif tectonically overriding by the carbonate rocks of the lycian nappes and sedimentary rocks of the neogene formations the bedrock units are stratigraphically overlain by the neogene sedimentary units of the denizli group the thermal springs of the pgf are affected by several hydrothermal processes including mixing water rock interaction and input of mantle volatiles the thermal water plots of the pgf deviate from the full equilibrium line indicating a low water maturity and or mixing processes mixing models and na k mg ternary diagram suggest mixing between meteoric and thermal waters during the uprising of the deep originated fluids the water rock interaction leads saturation of calcite and induces travertine precipitation in the discharge area low tritium this study proposes a conceptual hydrogeological hydrogeochemical tectonic model for the pgf the thermal waters are derived from the infiltration of rainwater through fractures and faults in high recharge areas to the deep hot reservoir heating produced by the high geothermal gradient is interpreted in relation with the regional crustal thinning thermal waters upwell along wnw ese trending deep faults and fractures the pamukkale fault system that act as hydrothermal pathways favouring migration of a huge amount of co2 rich gas from deep geothermal reservoir the geochemical and isotopic data of the thermal waters and gas indicate that the degassing of both metamorphic co2 and mantle derived co2 occurs in the pgf helium isotope data indicate that mantle volatiles produce possibly an upwelling into asthenosphere and ascent along these tectonic discontinuities in this context the pgf is one of the best example of geothermal fields as an interaction of active magmatism in the actively extending crustal setting

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

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

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

reversal of fe mg partitioning between garnet and staurolite in eclogite facies metapelites from the champtoceaux nappe brittany france this paper concentrates on the petrology of eclogite facies metapelites and particularly the significance of staurolite in these rocks a natural example of staurolite bearing eclogitic micaschists from the champtoceaux nappe brittany france is first described the champtoceaux metapelites present in addition to quartz phengite and rutile two successive parageneses 1 chloritoid staurolite i garnet cores and 2 garnet rims hkyanite chloritoid detailed microprobe analyses show that garnet and chloritoid evolve towards more magnesian compositions and that staurolite is more fe rich than coexisting garnet a comparison of the studied rocks with other known occurrences of eclogitic metapelites shows that whereas staurolite is always more fe rich than garnet in high pressure eclogites the reverse is true in low to medium pressure micaschists phase relations between garnet staurolite chloritoid biotite and chlorite are analysed in the kfmash system with excess quartz phengite rutile and h20 the topology of univariant reactions is depicted for a normal and a reverse fe m g partitioning between garnet and staurolite mineral compositional changes are also predicted for varying bulk rock chemistries in the studied micaschists the zonal arrangement of garnet inclusions and the progressive compositional changes of ferromagnesian phases record part of the prograde p t path before the attainment o f peak metamorphic conditions at about 650 700 c 18 20 kb the retrograde path which records the uplift of the champtoceaux nappe occurs under decreasing temperatures

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

extensional v contractional origin for the southern menderes shear zone sw turkey tectonic and metamorphic implications the southern menderes massif in southwest turkey consists mainly of orthogneisses and overlying palaeozoic middle paleocene schists and marbles the contact between the two distinct rock types is almost everywhere structural herein named the southern menderes shear zone a s facing high angle ductile shear zone that separates metamorphic rocks of differing grade although there is a consensus that the shear zone was associated with top to the s ssw shearing and is of tertiary age its origin and nature have been highly debated over the last decade some claim the contact is a thrust fault while others have argued for an extensional shear zone integration of field and microstructural data the identification of different fabrics associated kinematics and overprinting relationships with fission track thermochronology and the p t paths of the rocks above and below the shear zone supports the conclusion that the southern menderes shear zone is an extensional shear zone and not a thrust the data are consistent with a model that the exhumation and cooling of the southern menderes massif occurred after a period of extensional deformation pervasive top to the n nne high temperature medium pressure ductile shear structures d 2 deformation overprint an early hp event d 1 deformation the subsequent top to the s ssw greenschist shear band foliation d 3 deformation developed mostly around the orthogniess schist contact and forms the most characteristic features of the massif the top to the n nne structures are attributed to the main alpine constructional deformation that developed during back thrusting of the lycian nappes during the latest palaeogene collision between the sakarya continent and the anatolide tauride platform across the neotethyan ocean the top to the s ssw structures are interpreted to be the result of the exhumation of the massif during the activity of the southern menderes shear zone the presence of these two distinct fabrics with differing kinematics suggests that the southern menderes shear zone operated as a top to the n nne thrust fault during early alpine contractional deformation but was later reactivated with an opposite sense of movement top to the s ssw during subsequent oligocene miocene extensional collapse

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

lu hf geochronology on cm sized garnets using microsampling new constraints on garnet growth rates and duration of metamorphism during continental collision menderes massif turkey abstract this study shows lu hf geochronology of zoned garnet crystals contained in mica schists from the southern menderes massif turkey selected samples are four 3 5 cm large garnet megacrysts of which several consecutive garnet shells have been sampled with a micro saw and analyzed for dating the results are used to extract growth rates of garnet and also to improve the time constraint for alpine aged overprint of the pan african basement in the menderes massif lu hf ages of the sampled garnet shells are determined by two point garnet only isochrons using the garnets lu depleted rim compositions this yields a consistent decrease of age information from core to rim segments of individual garnet crystals and the calculated isochron ages propose a time frame of growth between 42 6 1 9 and 34 8 3 1 ma major element profiles in the investigated garnets characterize zoning patterns indicative of prograde conditions rayleigh fractionated bell shaped mn and decreasing fe fe mg are recorded by the garnets core to rim compositions therefore the obtained lu hf ages record timing of early prograde growth for the cores of the garnets two of the large garnet crystals also yield isochron ages of 58 83 0 69 and 50 16 0 84 ma in their innermost cores which appear to record an early nucleation event this view however is not in concordance with the observed major element profiles of these garnets and therefore is interpreted with caution termination of the garnet growth period is determined through the calculation of radial growth rates based on the size of the garnets and the lu hf ages obtained for consecutive shells extrapolation of these rates potentially constrains the total duration for garnet growth terminating at 31 6 ma comparison of the growth rates calculated for individual crystals shows a variety of slow and fast growing garnets and similar results have been previously obtained with the rb sr and sm nd isotope systems the new data provides a precise age determination for prograde barrovian metamorphism in the southern menderes massif which so far was placed between 63 and 27 ma on the basis of mica rb sr and ar ar dating this study provides new constraints crucial to the understanding of the tectonic evolution of southwest anatolia and the aegean realm as it yields a shorter outline for alpine aged continental collision

late alpine evolution of the central menderes massif western turkey the central menderes massif western turkey is characterized by an overall dome shaped alpine foliation pattern and a n nne trending stretching lineation a section through the southern flank of the central submassif along the northern margin of buyuk menderes graben has been studied there asymmetric non coaxial fabrics indicate that the submassif has experienced two distinct phases of alpine deformation a top to the n nne contractional phase and a top to the s ssw extensional event the former fabrics are coeval with a regional prograde barrovian type metamorphism at greenschist to upper amphibolite facies conditions this event known as the main menderes metamorphism is thought to be the result of internal imbrication of the menderes massif rocks along south verging thrust sheets during the collision of the sakarya continent in the north and the anatolide tauride platform in the south across the izmir ankara suture during the palaeocene eocene top to the s ssw fabrics represented by a well developed ductile shear band foliation associated with inclined and or curved foliation asymmetric boudins and cataclasites were clearly superimposed on earlier contractional fabrics these fabrics are interpreted to be related to a low grade greenschist retrogressive metamorphism and a continuum of deformation from ductile to brittle in the footwall rocks of a south dipping presently low angle normal fault that accompanied early miocene orogenic collapse and continental extension in western turkey a similar tectono metamorphic history has been documented for the northern flank of the dome along the southern margin of the gediz graben with top to the n nne extensional fabrics the exhumation of the central menderes massif can therefore be attributed to a model of symmetric gravity collapse of the previously thickened crust in the submassif area the central submassif is thus interpreted as a piece of ductile lower middle crust that was exhumed along two normal sense shear zones with opposing vergence and may be regarded as a typical symmetrical metamorphic core complex these relationships are consistent with previous models that the miocene exhumation of the menderes massif and cycladic massif in the aegean sea was a result of bivergent extension

tectonic transport directions of the lycian nappes in southwest turkey constrained by kinematic indicators abstract the orientation asymmetry and cross cutting relationships of the structures along the contact zone between the lycian nappes and the menderes massif suggest the presence of three deformation phases in the milas region of southwest turkey the first deformation phase d1 is characterized by a ductile deformation with top to the ne sense of shear structural data of the first deformation measured along the uppermost part of the menderes massif and the base of the lycian nappes suggest that the lowermost unit of the lycian nappes was emplaced initially from southwest to northeast onto the menderes massif during the early eocene the second deformation phase d2 is also ductile in nature and is characterized by an e w trending stretching lineation with a bivergent sense of shear which is probably related to the load of the overlying nappes a third deformation phase d3 is characterized by south dipping normal faults with top to the s sense of movement this third deformation phase can be related to southward movement of the lycian nappes along a low angle decollement zone the tectonic contact between the menderes massif and the lycian nappes and their strongly deformed rocks are unconformably covered by approximately flat lying coal bearing early middle miocene sedimentary rocks which constrains the upper time limit for all three deformation phases

reconciling the geological history of western turkey with plate circuits and mantle tomography abstract we place the geological history since cretaceous times in western turkey in a context of convergence subduction collision and slab break off to this end we compare the west anatolian geological history with amounts of africa europe convergence calculated from the atlantic plate circuit and the seismic tomography images of the west anatolian mantle structure western turkish geology reflects the convergence between the sakarya continent here treated as eurasia in the north and africa in the south with the anatolide tauride block atb between two strands of the neotethyan ocean convergence between the sakarya and the atb started at least 95 90 myr ago marked by ages of metamorphic soles of ophiolites that form the highest structural unit below sakarya these are underlain by high pressure low temperature metamorphic rocks of the tavsanli and afyon zones and the oren unit which in turn are underlain by the menderes massif derived from the atb underthrusting of the atb below sakarya was since 50 ma associated with high temperature metamorphism and widespread granitic magmatism thrusting in the menderes massif continued until 35 ma after which there is no record of accretion in western turkey plate circuits show that since 90 ma 1400 km of africa europe convergence occurred of which 700 km since 50 ma and 450 km since 35 ma seismic tomography shows that the african slab under western turkey is decoupled from the african plate this detached slab is a single coherent body representing the lithosphere consumed since 90 ma there was no subduction re initiation after slab break off atb collision with europe therefore did not immediately lead to slab break off but instead to delamination of subducting lithospheric mantle from accreting atb crust while staying attached to the african plate this led to asthenospheric inflow below the atb crust high temperature metamorphism and felsic magmatism slab break off in western turkey probably occurred 15 myr ago after which overriding plate compression and rotation accommodated ongoing africa europe convergence slab break off was accommodated along a vertical ne trending subduction transform edge propagator step fault zone accelerating southwestward slab retreat of the aegean slab the se aegean slab edge may have existed already since early miocene times or before but started to rapidly roll back along the southeastern aegean step in middle miocene times penetrating the aegean region in the pliocene

origin evolution and geothermometry of the thermal waters in the golemezli geothermal field denizli basin sw anatolia turkey abstract the golemezli geothermal field ggf is one of the best known geothermal fields in western anatolia turkey the exploited fluids are of meteoric origin mixed with deep magmatic fluids which interacted with the metamorphic rocks of the menderes massif the geothermal fluids are channeled along quaternary faults belonging to the main normal faults system delimiting the northern side of the denizli basin and their associated transfer zones in this study hydrochemical and isotopic analyses of the thermal and cold waters allow us to determine water rock interactions fluid paths and mixing processes two groups of thermal waters have been distinguished i group 1a comprising na so4 type and ca so4 type and ii group 1b only consisting ca hco3 type waters differently two groups were recognized in the cold waters i group 2a corresponding to ca hco3 type and ii group 2b including mg hco3 type their geochemical characteristics indicate interactions with the paleozoic metamorphic rocks of the menderes massif and with the neogene lacustrine sedimentary rocks dissolution of host rock and ion exchange reactions modify thermal water composition in the reservoir of the ggf high correlation in some ionic ratios and high concentrations of some minor elements suggest an enhanced water rock interaction none of the thermal waters has been reached a complete chemical re equilibrium possibly as a result of mixing with cold water during their pathways geothermal reservoir temperatures are calculated in the range of 130 210 c for the golemezli field very negative 18o and 2h isotopic ratios are respectively between 8 37 and 8 13 and 61 09 and 59 34 for the so4 rich thermal waters and ca 8 40 and 8 32 and 57 80 and 57 41 for the hco3 rich thermal waters low tritium

an olistostrome melange belt formed along a suture bornova flysch zone western turkey abstract the bornova flysch zone bfz in western turkey is a regional olistostrome melange belt located between the izmir ankara tethyan suture in northwest and the menderes massif in the southeast the bfz consists mostly of tectonized gravity mass flows the blocks are mesozoic limestone and ophiolite which are enclosed in cretaceous paleocene sheared sandstone and shale the limestone blocks are of two types the first type consists of late triassic to cretaceous shallow marine carbonates the second type has an upper triassic shallow marine section overlain by jurassic to cretaceous pelagic limestones a semi intact part of the platform occurs in the karaburun peninsula and on the island of chios the ophiolitic blocks in the bfz include ultramafic rock gabbro basalt and radiolarian chert of middle triassic to cretaceous in age the formation of the bfz overlaps with the cretaceous subduction and hp lt metamorphism of the northern passive continental margin of the anatolide tauride block this subduction zone was bounded in the west by a strike slip tear fault the bfz formed in a narrow basin between this tear fault and the tethyan ocean the mass flows came from the southeast from the overriding ophiolite and accretionary complex and from the northwest from the uplifted segments of the platform margin this model provides an explanation as why the bfz is unmetamorphosed whereas the equivalent strata in the menderes massif were metamorphosed at depths of over 20 km it also explains the prominence of gravity flows and the southward younging in the bfz and for the apparently anomalous observation that although the tethyan ocean lay to the northwest the ophiolitic blocks are more common on the southeastern part of the bfz regions away from the tear fault such as the karaburun peninsula were least affected by subsidence and deformation during the cretaceous and paleocene

pan african high pressure metamorphism in the precambrian basement of the menderes massif western anatolia turkey the menderes massif is made up of pan african basement and a paleozoic to early tertiary cover sequence imbricated by late alpine deformation the precambrian basement comprises primarily medium to high grade schists paragneisses migmatites orthogneisses metagranites charnockites and metagabbros high pressure relics in the pan african basement are divided into two groups eclogites and eclogitic metagabbros the mineral assemblage in the eclogites is omphacite jd 44 garnet clinozoisite rutile the eclogites occur as pods and boudinaged layers in the basement schists and paragneisses inclusions found in the cores of the garnets indicate a medium pressure protolith the eclogitic metagabbros are closely related to precambrian gabbroic stocks the igneous texture and relic magmatic phases are preserved in these high pressure rocks which are characterized by the mineral assemblage omphacite jd 25 garnet rutile kyanite the p t conditions of the pan african high pressure metamorphism in the eclogites are estimated to be 644 c with a minimum pressure of approximately 15 kbar the eclogites are partly to completely retrograded to garnet amphibolites by a barrovian type overprint which developed under isothermal decompression conditions for this post eclogitic event the p t estimates are 7 kbar and 623 c the eclogite relics provide strong support for a correlation of the menderes massif with the bitlis massif in terms of common pan african high pressure evolution

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

monazite ages and the evolution of the menderes massif western turkey the menderes massif experienced polyphase deformation but distinguishing pan african events from alpine tectono metamorphic evolution and discriminating eocene oligocene shortening from recent extension remain controversial to address this monazite in garnet bearing rocks from the massif s gordes central and cine sections were dated in thin section in situ using the th pb ion microprobe method cambro ordovician monazite inclusions in cine and central menderes massif garnets are 450 m y older than matrix grains monazites in reaction with allanite from the kuzey detachment which bounds the northern edge of the central menderes massif are 17 5 ma and 4 5 1 0 ma the pliocene result shows that dating of monazite can record the time of extension the kuzey detachment might have exhumed rocks a lateral distance of 53 km at a rapid rate of 12 mm year assuming the present 20 ramp dip pliocene monazite crystallization at 450 c and a geothermal gradient of 25 c km assuming an angle of 60 the rate decreases to 5 mm year with the detachment surface at 21 km depth in the pliocene two gordes massif monazites show a similar allanite monazite reaction relationship and are 29 6 1 1 ma and 27 9 1 0 ma suggesting that the cenozoic extension in the gordes massif and possibly the entire menderes massif might have begun in the late oligocene

the wide distribution of hp lt rocks in the lycian belt western turkey implications for accretionary wedge geometry ocean okay monie 1997 okay et al 2002 south of the izmir ankara suture fig 1a other hp lt metamorphic domains have resulted from the late cretaceous northward subduction of the neotethys ocean and subsequent early tertiary collision between the sakarya microcontinent and the anatolide tauride platform 3engor yilmaz 1981 okay et al 2001 these alpine metamorphic terranes form several tectonometamorphic units the late cretaceous blueschist belt of the tav anli zone okay kelley 1994 okay et al 1998 sherlock et al 1999 okay 2002 the recently described hp lt rocks of the afyon zone candan et al 2002 2005 the eocene cycladic blueschists and eclogites of the dilek peninsula region in the westernmost part of the menderes massif area candan et al 1997 oberhansli et al 1998 cetinkaplan 2002 and the hp lt metasediments of the lycian nappes oberhansli et al 2001 rimmele et al 2003a 2005 and the abstract in sw turkey fe mg carpholite has recently been recognized in the basal metasediments of the lycian nappes which overthrust the menderes massif on its southern flank this high pressure low temperature hp lt metamorphic index mineral was widely found in the bodrum peninsula region our new metamorphic and structural data on similar carpholite bearing rocks found farther north in several klippen of the lycian nappes located on top of the menderes massif show that hp lt rocks in sw turkey occur over a distance of 200 km in both north south and east west directions thus indicating a wide hp lt metamorphic belt the deformation pattern from the bodrum peninsula to civril all along the contact between the lycian nappes and the menderes massif reveals the role played by major top to the ne shear zones contemporaneous with exhumation of the lycian hp lt rocks this deformation shows an oblique direction of opposite shear sense relative to the earlier southward translation of the lycian nappes over the menderes massif for which top to the south displacements are preserved in the upper units of the lycian nappes on the bodrum peninsula as well as at the base of the lycian nappe klippen located farther north the widespread distribution of well preserved fe mg carpholite bearing rocks in the lycian nappes has implications for the geometry of the accretionary wedge responsible for hp lt metamorphism in sw turkey

tectonic significance of deformation patterns in granitoid rocks of the menderes nappes anatolide belt southwest turkey deformation fabrics in proterozoic cambrian granitic rocks of the cine nappe and mid triassic granites of the bozdag nappe constrain aspects of the tectonometamorphic evolution of the menderes nappes of southwest turkey based on intrusive contacts and structural criteria the proterozoic cambrian granitic rocks of the cine nappe are subdivided into older orthogneisses and younger metagranites the deformation history of the granitic rocks documents two major deformation events an early pre alpine deformation event dpa during amphibolite facies metamorphism affected only the orthogneisses and produced predominantly top to ne shear sense indicators associated with a ne trending stretching lineation the younger metagranites are deformed both by isolated shear zones and by a major shear zone along the southern boundary of the cine submassif we refer to this alpine deformation event as da3 da3 shear zones are associated with a n trending stretching lineation which formed during greenschist facies metamorphism kinematic indicators associated with this stretching lineation reveal a top to south sense of shear the greenschist facies shear zones cut the amphibolite facies structures in the orthogneisses 207pb 206pb dating of magmatic zircons from a metagranite which crosscuts orthogneiss containing amphibolite facies top to ne shear sense indicators shows that dpa occurred before 547 2 1 0 ma such an age is corroborated by the observation that mid triassic granites of the cine and bozdag nappes lack dpa structures the younger top to south fabrics formed most likely as a result of top to south alpine nappe stacking during the collision of the sakarya continent with anatolia in the eocene

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

neotethys closure history of anatolia insights from 40ar 39ar geochronology and p t estimation in high pressure metasedimentary rocks the multiple high pressure hp low temperature lt metamorphic units of western and central anatolia offer a great opportunity to investigate the subduction and continental accretion related evolution of the eastern limb of the long lived aegean subduction system recent reports of the hp lt index mineral fe mg carpholite in three metasedimentary units of the gondwana derived anatolide tauride continental block namely the afyon zone the oren unit and the southern menderes massif suggest a more complicated scenario than the single continental accretion model generally put forward in previous studies this study presents the first isotopic dates white mica 40ar 39ar geochronology and where possible are combined with p t estimates chlorite thermometry phengite barometry multi equilibrium thermobarometry on carpholite bearing rocks from these three hp lt metasedimentary units it is shown that in the afyon zone carpholite bearing assemblages were retrogressed through greenschist facies conditions at c 67 62 ma early retrograde stages in the oren unit are dated to 63 59 ma in the kurudere nebiler unit hp mesozoic cover of the southern menderes massif hp retrograde stages are dated to c 45 ma and post collisional cooling to c 26 ma these new results support that the oren unit represents the westernmost continuation of the afyon zone whereas the kurudere nebiler unit correlates with the cycladic blueschist unit of the aegean domain in western anatolia three successive hp lt metamorphic belts thus formed the northernmost tavsanli zone c 88 82 ma the oren afyon zone between 70 and 65 ma and the kurudere nebiler unit c 52 45 ma the southward younging trend of the hp lt metamorphism from the upper and internal to the deeper and more external structural units as in the aegean domain points to the persistence of subduction in western anatolia between 93 90 and c 35 ma after the accretion of the menderes tauride terrane in eocene times subduction stopped leading to continental collision and associated barrovian type metamorphism because by contrast the aegean subduction did remain active due to slab roll back and trench migration the eastern limb below southwestern anatolia of the hellenic slab was dramatically curved and consequently teared it therefore is suggested that the possibility for subduction to continue after the accretion of buoyant e g continental terranes probably depends much on palaeogeography

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

high precision lu hf geochronology of eocene eclogite facies rocks from syros cyclades greece abstract garnet bearing high pressure low temperature hp lt metamorphic rocks of the cycladic blueschist unit have been investigated by lu hf geochronology eclogites from syros island yield precise ages of 52 2 0 3 ma 51 4 0 4 ma and 50 2 ma preserved major and trace element growth zoning in garnet suggests that the closure temperature of the lu hf system in garnet was higher than the estimated peak metamorphic temperature of 500 c hence lu hf ages most likely reflect garnet growth in the studied samples our new lu hf grt ages are in excellent agreement with previously published u pb shrimp ages of metamorphic zircon and the maximum reported white mica rb sr and ar ar ages from syros garnet growth in all samples apparently took place over a narrow time interval because the lu hf ages cluster tightly even though the distribution of lu between cores and rims varies among samples we find no evidence for garnet generations that are significantly older or younger than the given isochron ages this in conjunction with the agreement among the ages of metamorphic zircon the maximum white mica ages and the lu hf ages strongly suggests that the 52 ma age dates a single hp event that affected these rocks

revision of leptite gneisses in the menderes massif a supracrustal metasedimentary origin the pan african basement of the menderes massif comprises a regular lithological succession that reaches a thickness of 8 km the oldest units of which are in ascending order so called leptite gneisses a quartzite sequence transition zone and mica schists new findings suggest that the protoliths for the leptite gneisses proposed to be of volcanic origin in previous studies were predominantly clastic sediments of litharenitic composition geochemical data indicate that the protoliths for the leptite gneisses were of cratonic provenance because they have undergone pan african polymetamorphism and are intruded by approximately 550 ma gneisses of granitic origin it is believed that the time of deposition of their protoliths was late proterozoic relict parageneses indicate that the pan african metamorphism reached granulite facies conditions in the leptite gneisses supracrustal sedimentary origin of these rocks require that these rocks formerly termed leptite and or leptite gneiss should be renamed sillimanite garnet gneiss and or paragneiss

stacking of nappes with different pressure temperature paths an example from the menderes nappes of western turkey pressure temperature p t paths have been estimated from metapelitic rocks in the lowermost cine nappe and the directly underlying bozdag nappe of the anatolide belt in western turkey peak metamorphic conditions in the lowermost cine nappe are 670 to 730 c 6 2 to 6 3 kb prograde garnet grt i growth occurred largely before and during the formation of the regional s p a foliation the suffix pa indicates a pre alpine age formation of a second garnet generation grt ii which discordantly overgrew grt i followed at 550 to 620 c 6 4 to 6 5 kb peak metamorphic conditions in the underlying bozdag nappe vary from 480 to 540 c 6 1 to 7 6 kb at the base to 610 to 660 c 8 5 to 10 8 kb at the top of the nappe and attest to an inverted metamorphic field gradient in the bozdag nappe differential thermodynamic modelling gibbs method yielded a prograde path for garnet growth during the formation of s p a because d p a structures formed during prograde metamorphism we relate them to crustal shortening which was associated with a top to the north northeast shear sense in present day coordinates this event caused deformation of the cine and bozdag nappes under different metamorphic conditions we propose that the cine nappe was heated by granitoid intrusions before being emplaced above a foreland unit we speculate that the bozdag nappe belonged to the lower parts of this foreland unit cross cutting relationships of d p a structures with dated granites indicates an age of 540 to 550 ma for this tectonometamorphic event the final juxtaposition of the cine nappe and bozdag nappes and also the inversion of the metamorphic field gradient in the bozdag nappe occurred during greenschist facies conditions during the alpine orogeny in the eocene

paleomagnetism of the miocene soma basin and its structural implications on the central sector of a crustal scale transfer zone in western anatolia turkey abstract the izmir balikesir transfer zone ibtz is a crustal scale major tectonic feature in western anatolia accommodating differential extension between the menderes mcc and cycladic ccc core complexes the kinematics and evolution of the southern part of the ibtz are well constrained but its northern continuation remains unstudied this part is crucial in understanding the complete evolution of western anatolian tectonics as well as a possible link between the ibtz and north anatolian fault zone nafz in this study new and extensive paleomagnetic structural and stratigraphic data were collected from the soma basin these results show that the basin evolved as a part of the ibtz including two separate rotational phases during the first middle miocene phase deformation was characterized by transcurrent tectonics and associated block rotations as much as 50 clockwise during which the ibtz evolved as a wide dextral shear zone during the second late miocene recent phase the mode of deformation in the aegean region switched from localized to distributed extension related to the acceleration of the tearing off of the african oceanic slab below the aegean region this led to the narrowing of the ibtz as a discrete brittle shear around the soma basin manifested by decoupling of dextral strike slip and normal faulting in this period the soma basin underwent around 21 counter clockwise rotation based on our new results the ibtz extends further to the north and possibly interacts with the southern branch of the nafz since the late miocene

geology and geochemistry of the pre early cambrian rocks in the sandikli area implications for the pan african evolution of nw gondwanaland abstract the pre early cambrian sandikli basement complex in western central anatolia comprises a low grade meta sedimentary succession guvercinoluk formation and meta rhyolites intruded by meta quartz porphyry rocks kestel cayi porphyroid suite the guvercinoluk formation consists of alternation of meta siltstones and meta sandstones with olistostromal conglomerates rare black chert and cherty meta dolomite lenses the kestel cayi porphyroid suite is a deformed highly sheared dome shaped rhyolitic body with quartz porphyry rocks quartz porphyry dykes intrude both the volcanic carapace and the meta sedimentary rocks of the guvercinoluk formation both the meta quartz porphyry rocks and meta rhyolites are typically mylonitic with relict igneous textures geochemical data indicate that the felsic rocks of the kestel cayi porphyroid suite are subalkaline and display characteristic features of post collisional i type granitoids the basement complex is unconformably overlain by variegated conglomerates mudstones and arkosic sandstones with andesitic lavas followed by siliciclastic rocks and carbonates that yielded early middle cambrian fossils based on the geochemical characteristics of the felsic rocks of kestel cayi porphyroid suite and the depositional features of the associated sediments it is suggested that the sandikli basement complex is related to a post collisional extension event in nw gondwanaland similar occurrences elsewhere have been related to a transition from continental plate convergence to continental plate divergence along the pan african belt

high pressure metasediments in central turkey constraints on the neotethyan closure history 1 the distribution of oceanic domains and continental blocks in central anatolia remains a challenge in understanding the alpine geodynamic evolution of the tethys realm the consumption of a neotethys oceanic branch at the mesozoic cenozoic boundary welded the central anatolian crystalline complex in central turkey and the anatolide tauride block in western turkey with the northerly eurasian margin whether those two regions constituted a single or two distinct continental masses is still matter of debate high pressure metamorphism has been locally evidenced in the afyon zone which was however defined as a greenschist facies metamorphic zone of the anatolide tauride block since the afyon zone composes a metamorphic equivalent of a continental margin exposed far south of the izmir ankara suture zone this encouraged us to reevaluate its metamorphic evolution in order to better understand the relation between western and central turkey our investigations reveal that the high pressure minerals fe mg carpholite and glaucophane are present in the entire afyon zone which we reconsider as a blueschist facies zone we additionally present a tectonic reconstruction stripping off the postcollisional tectonics it reveals that today s bending of the high pressure belt is consistent with an eocene collision of the anatolide tauride block around the southern edge of the central anatolian crystalline complex we argue that the central anatolian crystalline complex and the anatolide tauride block were two distinct continental masses separated by a neotethyan oceanic stripe the closure of which engendered subduction related metamorphism in the latter and arc volcanism and high grade metamorphism in the former by late cretaceous to early cenozoic

neotethyan closure history of western anatolia a geodynamic discussion this paper addresses the lithosphere scale subduction collision history of the eastern termination of the aegean retreating subduction system i e western anatolia although there is some general consensus on the protracted subduction evolution of the aegean since the early cenozoic at least correlation with western anatolia has been widely debated for more than several decades in western anatolia three main tectonic configurations have been envisaged in the past years to reconstruct slab dynamics during the closure of the neotethyan oceanic realm since the late cretaceous some authors have suggested an aegean type scenario with the continuous subduction of a single lithospheric slab punctuated by episodic slab roll back and trench retreat whereas others assumed a discontinuous subduction history marked by intermittent slab break off during either the campanian ca 75 ma or the early eocene ca 55 50 ma the third view implies three partly contemporaneous subduction zones our review of these models points to key debated aspects that can be re evaluated in the light of multidisciplinary constraints from the literature our discussion leads us to address the timing of subduction initiation the existence of hypothetical ocean basins the number of intervening subduction zones between the taurides and the pontides the palaeogeographic origin of tectonic units and the possibility for slab break off during either the campanian or the early eocene thence we put forward a favoured tectonic scenario featuring two successive phases of subduction of a single lithospheric slab and episodic accretion of two continental domains separated by a continental trough representing the eastern end of the cycladic ocean of the aegean the lack of univocal evidence for slab break off in western anatolia and southward younging hp lt metamorphism in continental tectonic units from 85 70 to 50 ma in the late cretaceous palaeogene period suggests continuous subduction since 110 ma marked by roll back episodes in the palaeocene and the oligo miocene and slab tearing below western anatolia during the miocene

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

stratigraphy of upper cretaceous palaeogene sequences in the southern and eastern menderes massif western turkey the stratigraphy of the uppermost levels of the menderes massif is controversial and within its details lie vital constraints to the tectonic evolution of south western turkey our primary study was carried out in four reference areas along the southern and eastern menderes massif these areas lie in the upper part of the menderes metamorphic cover and have a clear stratigraphic relationship and contain datable fossils the first one in the akbuk milas area is located south east of bafa lake where the milas then kizilagac and kazikli formations are well exposed there the milas formation grades upwards into the kizilagac formation the contact between the kizilagac and the overlying kazikli formation is not clearly seen but is interpreted as an unconformity the milas and kizilagac formations are also found north of mugla in the region of yatagan and kavaklidere in these areas the milas formation consists of schists and conformably overlying platform type emery and rudist bearing marbles rudists form the main palaeontological data from which a santonian campanian age is indicated the kizilagac formation is characterized by reddish greyish pelagic marbles with marly pelitic interlayers and coarsening up debris flow deposits pelagic marbles within the formation contain planktonic foraminifera and nanoplankton of late campanian to late maastrichtian age the kazikli formation is of flysch type and includes carbonate blocks planktonic foraminifera of middle palaeocene age are present in carbonate lenses within the formation in the serinhisar tavas area mesozoic platform type marbles yilanli formation belonging to the cover series of the menderes massif exhibit an imbricated internal structure two rudist levels can be distinguished in the uppermost part of the formation the first indicates a middle late cenomanian age and the upper one is santonian to campanian in age these marbles are unconformably covered by the palaeocene early eocene zeybekolentepe formation with polygenetic breccias in the cal denizli area the menderes massif succession consists of cherty marbles and clastic rocks with metavolcanic lenses the lower middle eocene alvan formation lies unconformably on this sequence and is interpreted as equivalent to the marble horizons at serinhisar but with pelagic facies the alvan formation consists of shale mafic volcanic rock lenses of limestone and blocks of recrystallized limestone the alvan formation is dated here for the first time by early middle eocene foraminifera and nanoplankton from the matrix of the formation an angular unconformity exists between the upper cretaceous and lower tertiary sequences suggesting that a phase of deformation affected the southern and eastern part of the menderes massif at this time this deformation may be caused by initial obduction of the lycian ophiolite onto the passive margin to the north of the menderes carbonate platform during the latest cretaceous drowning of the platform led to termination of carbonate deposition and deposition of deep water flysch like clastic sediments

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

structural and metamorphic evolution of the northern part of the menderes massif new data from the derbent area and their implication for the tectonics of the massif the menderes massif represents the western part of the metamorphic axis of the alpide orogen of anatolia asia minor a restricted area in its poorly known northern part around the village of derbent was studied to shed some light on its geological evolution and to compare it with that of the southern part of the massif in the derbent area three lithologic groups are recognized on the basis of their lithology and structural position namely the gneiss and the schist complexes and the marbles petrographic mineralogic and structural data indicate that the schist complex and the overlying marbles have undergone at least three phases of deformation and metamorphism the first phase probably reflects the closure of the karakaya marginal basin located to the north of the present menderes massif during the late triassic the traces of the first phase have been largely obliterated by the second phase which led to amphibolite facies metamorphism a pronounced flat lying foliation and a nne ssw trending

on diffusive climatological models abstract a simple zonally and annually averaged energy balance climatological model with diffusive heat transport and nonlinear albedo feedback is solved numerically some parameters of the model are varied one by one to find the resultant effects on the steady solution representing the climate in particular the outward radiation flux the insulation distribution and the albedo parameterization are varied we have found an accurate yet simple analytic expression for the mean annual insolation as a function of latitude and the obliquity of the earth s rotation axis this has enabled us to consider the effects of the oscillation of the obliquity we have used a continuous albedo function which fits the observed values it considerably reduces the sensitivity of the model climatic cycles calculated by solving the time dependent equation when parameters change slowly and periodically are compared qualitatively with paleoclimatic records

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

plagioclase relations in pelites central menderes massif turkey i the peristerite gap with coexisting kyanite in pelites of the central menderes massif albite and oligoclase with only slight chemical zoning coexist in apparent textural equilibrium in the garnet zone staurolite zone and staurolite kyanite transition zone the metamorphic temperature range is estimated as approximately 440 550 c from the hodges spear calibration of the garnet biotite geo thermometer or 440 500 c ganguly saxena calibration while oligoclase composition at the peristerite gap changes from an22 to an14 albite also becomes more sodic an1 5 an0 6 the slope of the albite limb is thus the reverse of that reported in other areas and may not be a true equilibrium feature occurrence of kyanite at temperatures below the crest of the gap is due to low water activity in the presence of graphite ah2o is estimated at approximately 0 1 0 2 from the na content of muscovite coexisting with albite kyanite quartz

what caused the denudation of the menderes massif review of crustal evolution lithosphere structure and dynamic topography in southwest turkey the deformation of earth s lithosphere in orogenic belts is largely forced externally by the sinking slab but can also be driven by internal delamination processes caused by mechanical instabiliti

tectonic significance of synextensional ductile shear zones within the early miocene alacamdag granites northwestern turkey synextensional granitoids may have significant structural features leading to the understanding of the evolution of extended orogenic belts one of the highly extended regions the aegean region includes a number of metamorphic core complexes and synextensional granitoids that developed following the alpine collisional events the alacamdag area in northwestern turkey is one of the key areas where miocene granites crop out along the boundary of various tectonic units structural data from the early miocene alacamdag granites demonstrated two different deformation patterns that may provide insights into the development of granitic intrusions and metamorphic core complexes 1 steeply dipping ductile shear zones caused emplacement of syn tectonic granite stocks they include kinematic indicators of a sinistral top to the sw displacement this zone has also juxtaposed the izmir ankara zone and the menderes massif in the west and east respectively 2 gently dipping ductile shear zones have developed within the granitic stocks that intruded the schists of the menderes massif on the structurally lower parts kinematic data from the foliated granites indicate a top to the ne displacement which can be correlated with the direction of the hanging wall movement documented from the simav and kazdag metamorphic core complexes the gently dipping shear zones indicate the presence of a detachment fault between the menderes massif and the structurally overlying izmir ankara zone mesoscopic to map scale folds in the shallow dipping shear zones of the alacamdag area were interpreted to have been caused by coupling between ne sw stretching and the accompanying nw se shortening of ductilely deformed crust during early miocene times one of the ne trending shear zones fed by granitic magmas was interpreted to form the northeastern part of a sinistral wrench corridor which caused differential stretching between the cycladic and the menderes massifs this crustal scale wrench corridor the izmir balikesir transfer zone may have controlled the asymmetrical and symmetrical extensions in the orogenic domains the combination of the retreat of the aegean subduction zone and the lateral slab segmentation leading to the sinistral oblique slip tearing within the eurasian upper plate appears to be a plausible mechanism for the development of such extensive ne trending shear zones in the aegean region

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

thermochronologic evaluation of postcollision extension in the anatolide orogen western turkey 1 to better understand the driving mechanisms behind the transition from collision to extension in a convergent orogen data from multiple low temperature thermochronometers were obtained from the simav detachment fault sdf the earliest developed major extensional structure recognized in the western anatolide orogen of western turkey twenty two zircon fission track ft 26 apatite ft 12 apatite u th he ages and 26 apatite ft track length analyses are presented the data establish that the sdf was a major extensional fault active between 25 and 19 ma the coincidence in timing of magmatism with cessation of sdf activity implies the detachment became locked owing to doming induced by magma emplacement zircon ft ages away from the influence of miocene magmatism record rapid footwall cooling between 25 and 21 ma at a slip rate of up to 15 km myr and demonstrate that active ductile deformation along the sdf migrated northward with time apatite ft ages from the footwall of the sdf are spatially invariant over 100 km and consistently 2 3 myr younger than the zircon fission track ages from the same samples these data are consistent with a regional but relatively rapid erosion linked cooling phase that removed 2 3 km of overburden following cessation of sdf activity but before deposition of sedimentary rocks on the detachment surface at 16 4 ma postcollision extension of the anatolide orogen with development of the sdf can be best explained as the result of postcollision magmatism and thermal weakening of the crust inducing the extensional reactivation of an earlier major out of sequence thrust

three dimensional s wave structure of the upper mantle beneath turkey from surface wave tomography summary a 3 d upper mantle structure beneath turkey is investigated using phase speeds of fundamental mode rayleigh waves employing a conventional two station method with high density seismic networks in turkey we analyse 289 seismic events with moment magnitude 5 5 and greater and with focal depth shallower than 100 km between 2006 and 2008 waveform data are derived from 164 three component broad band seismic stations operated by two national seismic networks at first rayleigh wave phase speed maps are obtained from the inversion of two station phase speeds using about 1000 3000 paths depending on the period of rayleigh waves the three dimensional s wave model is then obtained in the depth range from 40 to 180 km using the phase speed maps in the period range from 25 to 120 s our model reveals the fast anomalies in the north of cyprus associated with the subducted portion of the african oceanic lithosphere from the cyprus trench we identify a vertical discontinuity of the fast anomaly associated with the cyprus slab starting at 60 80 km depth which may represent a minor tear of the cyprus slab we observed that the western part of the cyprus slab is getting closer to the edge of the hellenic slab beneath the isparta angle ia and antalya basin our model also indicates a slow wave speed anomaly beneath the ia and antalya basin probably due to hot materials of asthenosphere rising from a tear of the subducted african oceanic lithosphere that is a slab tear between the cyprus and the hellenic subductions in the eastern part of turkey a widespread slow anomaly appears in the model that corresponds to the eastern anatolian accretionary complex eaac our model shows a fast anomaly beneath the eaac that can be interpreted as the detached portion of the subducted arabian lithosphere

presence and tectonic significance of cretaceous rudist species in the so called permo carboniferous goktepe formation central menderes metamorphic massif western turkey a schist sequence of the central menderes massif in which lenses of fossiliferous marbles are found is observed in the southern flank of the aydin mountain north of kosk aydin around egrikavak village these rocks have been considered as permo carboniferous in age and are included in the goktepe formation of earlier studies however some rudist species are described from thickly bedded gray marbles that have a concordant contact with the overlying schist sequence although the rudists have been metamorphosed it is observed that some contain fossils are well enough preserved to determine the following rudist fauna hippurites lapeirousei goldfuss hippurites nabresinensis futterer hippurites cf colliciatus woodward this rudist fauna dates the schist sequence as santonian campanian the schist sequence is overlain by a thick tectonostratigraphic pile of orthogneiss which has been interpreted as the pan african metamorphic core of the menderes massif a widespread cataclastic and mylonitic zone is present between the underlying rudist bearing marbles and the structurally overlying orthogneiss sequence the existing kinematic studies in the footwall and hangingwall of this tectonic contact reveal two different phases of deformations a contractional phase followed by an extensional phase during the contractional event which occurred at 36 ma the orthogneiss sequence was thrust faulted northwards over the schist sequence this thrust fault was later reactivated as a low angle normal fault beneath a supradetachment sedimentary basin of early middle miocene age the fossil discoveries of this study and the existing kinematic studies reveal that a new structural model for the central menderes massif in which the tectonometamorphic units form a major southward closing recumbent fold needs to be reviewed

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