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

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

coexisting andalusite kyanite and sillimanite sequential formation of three al2sio5 polymorphs during progressive metamorphism near the triple point sivrihisar turkey regionally metamorphosed muscovite bearing quartzites from sivrihisar turkey contain coexisting andalusite kyanite and sillimanite kyanite is the most abundant polymorph and defines a lineation along with prismatic sillimanite andalusite staurolite and elongate quartz andalusite is the most fe rich of the polymorphs 0 9 1 6 wt fe 2 o 3 compared with 0 6 0 9 wt for kyanite and sillimanite and was ductilely deformed staurolite has partially pseudomorphed kyanite and occurs intergrown with sillimanite garnet occurs in some metaquartzites and interlayered mica schists mica schists lack al 2 sio 5 polymorphs porphyroblasts in mica schists are chloritoid chloritoid staurolite garnet or staurolite garnet with inclusions of chloritoid and staurolite textural relations and relative deformation features among the three polymorphs suggest the crystallization sequence andalusite kyanite sillimanite with growth of staurolite primarily in the sillimanite stability field results of garnet biotite thermometry and estimates of peak p t conditions from petrogenetic grids are 540 560 c maximum pressure is not known but there is no evidence for the high pressure low temperature conditions that affected similar rocks to the northwest in the sivrihisar massif the stable coexistence of staurolite sillimanite at peak metamorphic conditions suggests a maximum pressure of 5 5 kbar the three polymorphs grew sequentially along a clockwise p t path that looped around the al 2 sio 5 triple point during incipient subduction of a continental margin sequence burial andalusite kyanite followed by collision heating and or decompression kyanite sillimanite

sedimentologic to metamorphic processes recorded in the high pressure low temperature mesozoic rosetta marble of anatolia anatolia s high pressure metamorphic belts are characterized in part by a neotethyan stratigraphic succession that includes a mid cretaceous hemi pelagic marble sequence this unit contains towards its stratigraphic top dm to m long radiating calcitic rods forming rosette like textures here we refer to these features as rosetta marble the remarkable textural similarity of non metamorphic selenite crystals and radiating calcite rods in the rosetta marble strongly suggests that these textures represent pseudomorphs after selenites metamorphosed hemi pelagic limestones dominated by rosetta selenite pseudomorphs are alternating with siliceous meta sediments containing relictic radiolaria tests this stratigraphic pattern is indicative of transient phases characterized by evaporites precipitated from basinal brines alternating with non evaporative hemi pelagic deposition from normal marine seawater the regional distribution of rosetta marble exposures over 600 km is indicative of basin scale evaporitic intervals high pressure low temperature metamorphism of these rocks is witnessed by sr rich up to 3500 ppm fibrous calcite pseudomorphs after aragonite and isolated aragonite inclusions in quartz peak metamorphic conditions of 1 2 gpa and 300 350 c are attested by high si white mica thermobarometry the rosetta marble case example examines the potential to unravel the complete history from deposition to diagenesis and metamorphism of meta sedimentary rocks

deep crustal structure of northwestern part of turkey abstract the deep crustal structure of the polatli nallihan karasu nw turkey area was investigated by magnetotelluric and transient electromagnetic measurements all measurements were acquired as part of a national project called crustal structures of turkey undertaken by the general directorate of mineral research and exploration of turkey mta magnetotelluric data were collected from 44 stations located along a 250 km northwest to southeast profile crossing in succession the istanbul zone intra pontid suture sakarya continent izmir ankara suture tavsanli zone the tauride anatolide belt intra pontid suture and sakarya continent after decompositional analysis and strike direction estimation static shift is corrected by using transient electromagnetic data from mt apparent resistivity data the processed mt data were inverted to derive a two dimensional geoelectrical model the estimated model is interpreted with the help of gravity data observed along the mt lines and using earthquake epicenter which occurred around mt measurement lines four layers with distinctive resistivity values dominate the geoelectrical section the uppermost layer having resistivity values of 5 35 ohm m can be interpreted as the sedimentary fill this layer reaches down to about 10 km depth in haymana basin the second layer has resistivity values higher than 110 ohm m and reaches 27 km depth the first and second layers can be inferred as constituting the upper crust in the general model of the earth s lithosphere the third layer underlying the upper crust has resistivity values of 10 30 ohm m corresponding to the lower crust the fourth layer having high resistivity values 225 ohm m can be considered as the upper mantle the depth of the boundary separating the crust from the upper mantle moho varies between 20 and 40 km high conductive zones between the istanbul zone and sakarya continent sakarya continent and tavsanli zone coincide with high bouguer gravity anomaly values it can be inferred from these properties that these zones correspond to the intra pontide suture and the izmir ankara suture noticeable differences in tectonic characteristics are observed between the southern and northern part of sakarya continent in the geoelectrical section the northern part of the continent is separated by high dip slip faults while the faults in the southern part do not affect the high resistive zone in the deeper part of the section these faults controlled the development of the haymana basin but they do not alter the high resistive zone to form separate blocks the majority of these faults which are clearly seen in the geoelectrical section are not evident in the sedimentary fill these buried faults have not been studied in detail prior to the present study

persistent upwelling and front over the sulu ridge and their variations the persistent upwelling and front isolated over the sulu ridge are newly detected by a suite of satellite measurements and confirmed by historical cruise observations a three dimensional tide circulation coupled model is employed to investigate the dynamic mechanisms the intense vertical velocity shear induced by the vigorous internal tidal mixing is identified as the vital dynamic factor to trigger the upwelling and nutrient pumping through the strong tide topography interactions satellite observations indicate that the pronounced surface cooling and phytoplankton bloom are isolated over the sulu ridge throughout the year the steady front characterizes 10 20 km width and strength over 0 3 degrees c km near the southern edge the feature is further confirmed by the numerical simulation and in situ hydrological observation modeling experiment suggests that a quasi symmetrical vertical circulation bifurcation across the sulu ridge due to the asymmetry of tidal currents is the main mechanism to maintain the persistent upwelling and front moreover the local wind forcing plays an important regulating role in the seasonal and interannual variations the surface cooling and thermal front intensity reach the maximum in winter under the forcing of strong northeasterly monsoons due to prolonged el nino southern oscillation enso effects the surface cooling was significantly weakened during 1998 and 2010 summer further analysis indicates the fact that the southwesterly monsoon is weakened dramatically as part of the anticyclonic atmospheric circulation anomalies over the northwest pacific the latter results from the significant influence of tropical indian ocean capacitor effect associated with el nino southern oscillation

coupled isotopic systematics of surface cerium and neodymium in the pacific ocean trace metals are known to be essential elements in marine ecosystems radiogenic isotopes of neodymium nd have been used as tracers in many recent oceanic trace metal studies although among rare earth elements cerium ce isotopes might be an interesting complementary tracer for particle reactive and lithogenic metals such as manganese this study determined the 138ce 142ce ratios in surface waters of the pacific ocean and its surrounding marginal seas the sulu sea the south china sea the east china sea and the south australian basin the 138ce 142ce and 143nd 144nd data are discussed in terms of the sources of rare earth elements and elemental fractionation between ce and nd in the marine environment in the western north pacific central water east china sea and south china sea isotopic compositions of ce ce 0 7 to 1 4 are most affected by radiogenic ce of continental origin in contrast less radiogenic isotopic compositions of ce ce 0 4 to 0 3 in the pacific equatorial water were observed locally near volcanic islands such as new guinea island suggesting the influence of mantle derived ce compared with nd the isotopic composition of ce showed a heterogeneous distribution in a given surface water mass reflecting the importance of local sources variations of isotopic compositions and concentrations of ce in the western equatorial pacific and the east china sea suggest that lithogenic ce is supplied and scavenged by particle dissolved interaction near the margins radiogenic ce in the western north pacific central water which is more continental like than nd isotopes suggests direct input by atmospheric dust into the north pacific ocean the isotopic distribution of ce is sensitive to aeolian supply to the surface waters of the open ocean this unique feature indicates that the 138ce 142ce ratio can be a useful chemical tracer for lithogenic trace elements such as iron and manganese which have short oceanic residence time

nonlinear internal wave evolution in the sulu sea abstract this paper presents an analytical investigation of nonlinear internal wave evolution in the sulu sea a solitary wave theory that describes tie evolution of internal solitons has been developed and expanded to include effects of vertical shear variable bottom topography radial spreading and dissipation a numerical parametric study has been performed in order to understand the relative importance of radial spreading and dissipation effects on soliton decay across the sulu sea using sulu sea environmental and initial data the numerical simulations reproduce reasonably well the measurements at the downstream mooring from the sulu sea internal soliton experiment comparison of simulations with data on the evolution of lead wave amplitude across the sulu sea indicates that the variable depth effect is appreciable and the radial spreading and dissipation effects are very significant the effects of the earth s rotation vertical shear variable bottom topography radial spreading and dissipation

a lost tethyan evaporitic basin evidence from a cretaceous hemipelagic meta selenite red chert association in the eastern mediterranean realm

interpretation of three dimensional seismic refraction data from western hecate strait british columbia structure of the queen charlotte basin the queen charlotte basin consists of up to 6 km of tertiary clastic sediments in a complex sequence of fault bounded subbasins the tectonic evolution of the basin in still being debated with recent interpretations including distributed strike slip extension oblique or en echelon rifting simple extension orthogonal to the plate margin and block faulting and vertical tectonics a combined seismic reflection and refraction survey was carried out in 1988 to investigate the structure and tectonic evolution of the basin and underlying crust while the marine multichannel reflection data were being collected refracted and wide angle reflected energy from the large air gun array was recorded at surrounding land sites in both two dimensional in line and three dimensional broadside geometries the broadside refraction data recorded on the queen charlotte islands provide good three dimensional coverage of western hecate strait these data are modelled to determine the three dimensional structure of the qu

triassic to neogene geologic evolution of the queen charlotte region a wealth of new geological and geophysical data from recent studies of the queen charlotte region are integrated into a coherent model in this paper we summarize these new studies and discuss possible correlations with other areas four tectonostratigraphic divisions are distinguished by stratigraphic structural and magmatic character and each is separated by a major unconformity the oldest division comprises widely distributed upper paleozoic through middle jurassic strata of wrangellia that accumulated in volcanic arc and stable shelf and basinal settings no significant deformation occurred in the queen charlotte islands region during the accumulation of these rocks a middle and upper jurassic assemblage comprises two plutonic suites and volcanic and epiclastic rocks the unconformity below the middle and upper jurassic assemblage marks a regional southwest vergent contractional deformation that is the most significant mesozoic or cenozoic deformation in the region jurassic plutons in the que

petrofabrics of high pressure rocks exhumed at the slab mantle interface from the point of no return in a subduction zone sivrihisar turkey the highest pressure recorded by metamorphic rocks exhumed from oceanic subduction zones is 2 5 gpa corresponding to the maximum decoupling depth mdd 80 10 km identified in active subduction zones beyond the mdd the point of no return exhumation is unlikely the sivrihisar massif turkey is a coherent terrane of lawsonite eclogite and blueschist facies rocks in which assemblages and fabrics record p t fluid deformation conditions during exhumation from 80 to 45 km crystallographic fabrics and other features of high pressure metasedimentary and metabasaltic rocks record transitions during exhumation in quartzite microstructures and crystallographic fabrics record deformation in the dislocation creep regime including dynamic recrystallization during decompression and a transition from prism slip to activation of rhomb and basal slip that may be related to a decrease in water fugacity during decompression 2 5 to 1 5 gpa phengite lawsonite and omphacite or glaucophane in quartzite and metabasalt remained stable during deformation and omphacite developed an l type crystallographic fabric in marble aragonite developed columnar textures with strong crystallographic fabrics that persisted during partial to complete dynamic recrystallization that was likely achieved in the stability field of aragonite p 1 2 gpa results of kinematic vorticity analysis based on lawsonite shape fabrics are consistent with shear criteria in quartzite and metabasalt and indicate a large component of coaxial deformation in the exhuming channel beneath a simple shear dominated interface this large coaxial component may have multiplied the exhuming power of the subduction channel and forced deeply subducted rocks to flow back from the point of no return

aragonite pseudomorphs in high pressure marbles of syros greece numerous rod shaped calcite crystals occur in the blueschist to eclogite facies marbles of syros greece the rods show a shape preferred orientation and the long axes of the rods are oriented at a large angle to foliation the crystals also have a crystallographic preferred orientation calcite c axes are oriented parallel to the long axes of the rods based on their chemical composition shape and occurrence in high pressure marbles these calcite crystals are interpreted as topotactic pseudomorphs after aragonite that developed a crystallographic preferred orientation during peak metamorphism this interpretation is consistent with deformation of aragonite by dislocation creep which has been observed in laboratory experiments but has not been previously reported on the basis of field evidence subsequent to the high pressure deformation of the aragonite marbles the aragonite recrystallized statically into coarse rod shaped crystals maintaining the crystallographic orientation developed during deformation during later exhumation aragonite reverted to calcite and the marbles experienced little further deformation at least in the pseudomorph rich layers some shearing of pseudomorph bearing marble layers did occur and is indicated by twinning of calcite and by a variable inclination of the pseudomorphs relative to foliation

finite difference calculation of traveltimes in three dimensions the traveltimes of first arriving seismic rays through most velocity structures can be computed rapidly on a three dimensional numerical grid by finite difference extrapolation head waves are properly treated and shadow zones are filled by the appropriate diffractions differences of less than 0 11 percent are found between the results of this technique and ray tracing for a complex but smooth model this scheme has proven useful for earthquake location and shows promise as an inexpensive well behaved substitute for ray tracing in forward modeling and kirchhoff inversion applications

crustal thickness beneath the queen charlotte basin canada results of a seismically constrained gravity inversion a gravity inversion routine was used to calculate crustal thickness variations in the queen charlotte basin western canada first a crustal bouguer anomaly was derived using a digital well constrained depth to basement map and densities determined from well logs and rock samples this anomaly was subsequently inverted for crustal thickness assuming a single density contrast at depth and an average crustal thickness provided by seismic refraction data the results restricted to that portion of the basin for which there are good quality data show crustal thickness variations of the order of 12 km regions of thin crust are located off northern vancouver island 20 km along the axis of hecate strait and in northern queen charlotte sound 24 km thicker crust is associated with central queen charlotte ridge and northeastern hecate strait tests show these trends in crustal thickness prevail for all reasonable ranges of input parameters calculated residual gravity anomalies contain information useful for mapping the distribution of volcanics interbedded with sediments in subbasins and for refining estimates of depth to basement derived from seismic data alone our results are for the most part in excellent agreement with seismically derived estimates of moho depth they show minimum crustal thickness beneath regions of maximum sediment accumulation supporting an extensional origin for the basin they indicate that this extension was quite heterogeneous and yield minimum estimates which vary from 13 in some parts of the basin to as much as 65 in others the results can be used to discriminate between models on the tertiary evolution of the basin the observed trends are not predicted by the lithospheric flexure or simple margin perpendicular extension models but are consistent with a model of crustal thinning by distributed shear in a transtensional regime

western equatorial pacific planktic foraminiferal fluxes and assemblages during a la nina year 1999 abstract a correlation between foraminiferal community dynamics and environmental conditions may provide a basis for establishing paleoclimatic proxies we studied planktic foraminiferal shell fluxes and assemblages in samples collected in three time series sediment trap deployments in the western equatorial pacific under la nina conditions from january to november 1999 eleven species contributed about 90 of the total flux in all traps two sites mt1 mt3 in the western pacific warm pool region wpwp were characterized by common occurrences of the species globigerinoides ruber globigerinoides sacculifer globigerinoides tenellus and neogloboquadrina dutertrei site mt5 farther to the east in the equatorial upwelling region had common occurrences of globigerina bulloides globigerinita glutinata and pulleniatina obliquiloculata very high abundances of g bulloides and g glutinata at mt5 indicate that equatorial upwelling eu occurred during the 1999 la nina the two western sites have similar assemblage compositions but mt1 135 e has the highest fluxes up to 3800 tests m 2 day 1 whereas mt3 145 e has fluxes below 2200 tests m 2 day 1 relatively high fluxes up to 3000 tests m 2 day 1 occur at site mt5 176 e where upwelling occurred the differences in faunal composition in the wpwp and eu might be attributable to differences in the way in which nutrients are supplied to the phytoplankton large amounts of suspended material are supplied to the wpwp by advection of waters passing through the coastal region of an archipelago whereas upwelling of nutrient rich waters enhances primary production in the eu at the westernmost site in the wpwp a peak in the g bulloides flux coincided with southward flow of the new guinea coastal current ngcc in late february but the highest g ruber flux coincided with northward flow of this current in late may thus the differences in species dominance at this location may be caused by monsoon driven variability in the flow direction of the nggc

crustal and upper mantle velocity structure of the salton trough southeast california this paper presents data and modelling results from a crustal and upper mantle wide angle seismic transect across the salton trough region in southeast california the salton trough is a unique part of the basin and range province where mid ocean ridge transform spreading in the gulf of california has evolved northward into the continent in 1992 the u s geological survey usgs conducted the final leg of the pacific to arizona crustal experiment pace two perpendicular models of the crust and upper mantle were fit to wide angle reflection and refraction travel times seismic amplitudes and bouguer gravity anomalies the first profile crossed the salton trough from the southwest to the northeast and the second was a strike line that paralleled the salton sea along its western edge we found thin crust 21 22 km thick beneath the axis of the salton trough imperial valley and locally thicker crust 27 km beneath the chocolate mountains to the northeast we modelled a slight thinning of the crust further to the northeast beneath the colorado river 24 km and subsequent thickening beneath the metamorphic core complex belt northeast of the colorado river there is a deep apparently young basin 5 6 km unmetamorphosed sediments beneath the imperial valley and a shallower 2 3 km basin beneath the colorado river a regional 6 9 km s layer between 15 km depth and the moho underlies the salton trough as well as the chocolate mountains where it pinches out at the moho this lower crustal layer is spatially associated with a low velocity 7 6 7 7 km s upper mantle we found that our crustal model is locally compatible with the previously suggested notion that the crust of the salton trough has formed almost entirely from magmatism in the lower crust and sedimentation in the upper crust however we observe an apparently magmatically emplaced lower crust to the northeast outside of the salton trough and propose that this layer in part predates salton trough rifting it may also in part result from migration of magmatic spreading centers associated with the southern san andreas fault system these spreading centers may have existed east of their current loca tions in the past and may have influenced the lower crust and upper mantle to the east of the current salton trough

tracing high pressure metamorphism in marbles phase relations in high grade aluminous calcite dolomite marbles from the greek rhodope massif in the system cao mgo al2o3 sio2 co2 and indications of prior aragonite abstract four different types of parageneses of the minerals calcite dolomite diopside forsterite spinel amphibole pargasite ti clinohumite and phlogopite were observed in calcite dolomite marbles collected in the kimi complex of the rhodope metamorphic province rmp the presence of former aragonite can be inferred from carbonate inclusions which in combination with an analysis of phase relations in the simplified system cao mgo al 2 o 3 sio 2 co 2 cmas co 2 show that the mineral assemblages preserved in these marbles most likely equilibrated at the aragonite calcite transition slightly below the coesite stability field at ca 720 c 25 kbar and a co 2 0 01 the thermodynamic model predicts that no matter what activity of co 2 garnet has to be present in aluminous calcite dolomite marble at uhp conditions

rheological and microstructural evolution of carrara marble with high shear strain results from high temperature torsion experiments abstract this study investigated the rheological and microstructural evolution of carrara marble deformed to large shear strain to understand how dynamic recrystallization and lattice preferred orientation lpo are related to strain softening processes solid cylinders of carrara marble were deformed in torsion up to a shear strain of 11 at constant twist rates which correspond to a shear strain rate of 3 10 4 s 1 at the outer surface and at temperatures of 1000 and 1200 k 727 and 927 c respectively for the initial grain size of 150 m these conditions are within the dislocation creep regime substantial changes in both rheology and microstructure were observed as the marble deformed to high shear strain at 1000 k 1200 k a peak stress was reached at about 1 0 5 followed by moderate strain weakening an apparent steady state flow stress was obtained at high shear strain of 5 2 the stress exponent n decreased slowly with strain from 10 1 to 6 9 at 1000 k but it remained approximately constant at 1200 k n around 10 at the maximum reached shear strain of 11 8 5 the marble had almost completely recrystallized to a fine grain size of about 10 m 20 m a secondary foliation developed in the recrystallized matrix which is at a large oblique angle to the shear zone boundary szb lpo was measured by electron backscatter diffraction ebsd for both temperatures the lpo evolved from an oblique deformation texture to a very sharp and symmetric single orientation component with r 1014 parallel to the shear plane and a 1210 parallel to the shear direction it is concluded that strain weakening was associated with the development of a strong lpo during dynamic recrystallization to a finer grain size mechanical and microstructural steady state is only reached at large shear strain the steady state lattice and grain shape fabrics can hardly be used as shear sense indicators in such recrystallized calcite mylonites

transpression between two warm mafic plates the queen charlotte fault revisited the queen charlotte fault is a transpressive transform plate boundary between the pacific and north american plates offshore western canada previous models for the accommodation of transpression include internal deformation of both plates adjacent to the plate boundary or oblique subduction of the oceanic plate the latter has been the preferred model both plates are warm and mafic and have similar mechanical structures new multichannel seismic reflection data show a near vertical queen charlotte fault down to the first water bottom multiple significant subsidence east of the queen charlotte fault a large melange where the fault is in a compressive left step and faulting which involves oceanic basement gravity modeling of profiles indicates that moho varies fairly smoothly across the plate boundary isostatic anomalies indicate that the pacific plate is flexed downward adjacent to the queen charlotte fault upward flexure of north america along with crust thickened relative to crust in the adjacent basin creates topography known as the queen charlotte islands combined with other regional studies these observations suggest that the plate boundary is a vertical strike slip fault and that transpression is taken up within each plate

exhumation with a twist paleomagnetic constraints on the evolution of the menderes metamorphic core complex western turkey 1 much remains to be understood about the links between regional vertical axis rotations continental extension and shortening in western turkey miocene vertical axis rotations have been reported that occur simultaneously with the extensional exhumation of the menderes metamorphic core complex which has been related to back arc extension in the eastern part of the aegean back arc in this paper we explore the spatial and temporal relationships between vertical axis rotations in southwestern turkey and extensional unroofing of the menderes massif to this end we provide a large set of new paleomagnetic data from western turkey and integrate these with the regional structural evolution to test the causes and consequences of oroclinal bending in the aegean region the lycian nappes and bey daglari are shown to rotate 20 between 16 and 5 ma defining the eastern limb of the aegean orocline this occurred contemporaneously with the exhumation of the central menderes massif along extensional detachments and after the latest oligocene to early miocene exhumation of the northern and southern menderes massifs exhumation of the latter two was not associated with vertical axis rotations the lower miocene volcanics in the region from lesbos to usak to the north of the central menderes massif underwent a small clockwise rotation insignificant with respect to eurasia this shows that exhumation of the central menderes massif was associated with a vertical axis rotation difference between the northern and southern menderes massifs of 25 30 this result is in excellent agreement with the angle defined by the trends of buyuk menderes and alasehir detachments as well as the angle defined by the regionally curving stretching lineation pattern across the central menderes massif these structures define a pivot point rotation pole for the west anatolian rotations the rotation of the southern domain including the southern menderes massif the lycian nappes and bey daglari must have led to n s contraction east of this pole the eastern limit of the rotating domain is formed by the transpressional couple of the aksu thrust and kirkkavak fault in the center of the isparta angle previously reported clockwise rotations in the volcanic fields near afyon may be the result of distributed n s shortening east of the pivot point the precise accommodation of this shortening history remains open for investigation late oligocene to early miocene extension in the eastern part of the aegean back arc was ne sw oriented and likely bounded by a discrete transform this transform may be associated with an early evolution of the eastern aegean subduction transform edge propagator fault oroclinal bending in the west anatolian region is likely related to a reconnection of the eastern part of the aegean orocline with the african northward moving plate in tandem with roll back in the aegean back arc comparable to a recently postulated scenario for western greece

texture development of calcite by deformation and dynamic recrystallization at 1000 k during torsion experiments of marble to large strains abstract torsion deformation experiments were performed on solid cylinders of carrara marble at high temperature 1000 k and constant twist rate about 4 10 4 rad s 1 to large twist angles between 80 and 840 these conditions correspond to simple shear deformation at constant shear strain rate 3 10 4 s 1 and variable amounts of shear strain of 1 2 5 and 11 at the outer mantle of the sample cylinders lattice preferred orientations lpo were measured on polished thin sections using automated electron backscatter diffraction ebsd to analyze the microtextures in orientation imaging micrographs oim shear deformation produced first a microstructure of elongated grains with shape and orientation close to the finite strain ellipse of the imposed shear strain 1 and 2 a deformation texture developed with monoclinic sample symmetry and an oblique c axis distribution relative to the shear plane with increasing shear the marble recrystallized by subgrain rotation and nucleation of small grains starting along grain boundaries which ultimately replaced the whole deformation microstructure a steady state recrystallization microstructure evolved with nearly equant grains of about 10 m in size 5 and 11 the lpo changed completely from the monoclinic deformation texture into a distribution with a sharp single orientation component with r 10 1 4 parallel to the shear plane and a 1 2 1 0 parallel to the shear direction this recrystallization texture has orthorhombic symmetry with respect to shear plane and shear direction during the transition the applied flow stress decreased simple shear deformation of calcite was modeled with the self consistent polycrystal plasticity theory it included a model for dynamic recrystallization based on a balance between growth and nucleation model results agree with experimental data if slip on r 10 1 4 a 1 2 1 0 is introduced as a potential slip system for calcite in that case the steady state recrystallization texture has an easy slip preferred orientation the hypothesis remains speculative until this slip system is actually confirmed by direct observation

el nino related offshore phytoplankton bloom events around the spratley islands in the south china sea 1 satellite chlorophyll a chl a observations reveal offshore phytoplankton bloom events with high chl a 1 mg m 3 spreading over 300 km off the coasts around the spratley islands in the south china sea scs during the spring of 1998 the bloom entails anomalous wind jet and sea surface temperature sst cooling suggesting that the wind jet induced mixing and or offshore upwelling bring about the cooling and the bloom through the supply of nutrient rich waters into the euphotic zone the strong wind jet is orographically formed responding to shifts in wind direction over the eastern scs the wind shift is connected with the philippine sea anomalous anticyclone that is established during el nino indicating the el nino related offshore bloom the long term reanalysis winds over the eastern scs demonstrates that wind jet formation and associated offshore cooling bloom are expected to occur in most cases of the subsequent el nino years

partial high pressure aragonitization of micritic limestones in an accretionary complex tavsanli zone nw turkey pelagic micritic limestones within an upper cretaceous accretionary complex in the tavsanli zone nw turkey preserve textures indicating incomplete prograde transformation of micritic calcite to aragonite representing the only known example of this type aragonitization starts at the central parts of the micritic limestone beds and advances towards the lower and upper parts of the layers at the expense of micrite micrite is very fine grained 0 003 mm and contains radiolaria foraminifera and thin shell fragments aragonite forms large crystals up to 3 cm across with straight grain boundaries and c axis mostly subparallel to the carbonate beds relict micritic portions are devoid of any aragonite grain stylolites characterized by the accumulation of clay minerals fe mn hydroxides and quartz are concentrated in the upper and lower parts of the beds stylolite formation precedes aragonitization conditions of aragonitization are estimated as 200 50 c and 0 45 0 65 gpa based on metamorphic mineral assemblages observed in associated basalts several features such as i constant composition of micritic calcite 98 99 mol caco3 throughout individual beds ii enormous grain size difference between micritic calcite and aragonite up to 1200 times and iii absence of any aragonite grains within the relict micritic portions suggest that kinetic rather than thermodynamic factors controlled selective aragonite formation in the central portions of carbonate layers

the role of recrystallisation on the deformation behaviour of calcite rocks large strain torsion experiments on carrara marble abstract the rheological microstructural and textural evolution of carrara marble was studied during experimental deformation in torsion up to very large shear strains 0 4 50 experiments were performed at constant angular displacement rates corresponding to shear strain rates of 6 10 5 3 10 3 s 1 a confining pressure of 300 mpa and temperatures of 500 600 and 727 c microstructures and crystallographic preferred orientations cpo were analysed using light microscopy and electron backscatter diffraction ebsd at all conditions deformation occurred dominantly by dislocation creep even up to very large shear strains after peak stresses 2 recrystallisation mostly by subgrain rotation caused weakening 5 20 grain size reduction and a change in the cpo a monoclinic cpo that formed at small strains at all temperatures evolved into two different large strain cpos at different temperatures at large strains even after complete recrystallisation the cpo continued to strengthen and a secondary foliation was formed at a steep angle to the shear zone boundary this secondary foliation was continuously reset by both subgrain rotation and grain boundary migration recrystallisation and eventually overprinted the primary foliation misidentifying the primary and secondary foliations could result in misinterpretation of the applied strain field more generally information about the amount of strain is lacking for microstructures and cpos of highly deformed ultramylonites

lawsonite composition and zoning as tracers of subduction processes a global review abstract lawsonite is an abundant hydrous mineral in oceanic crust sediments and metasomatic rocks at depths of 45 to 300 km in most subduction zones but it is rarely preserved in the geologic record because it commonly transforms to epidote and other minerals during prograde or retrograde metamorphism owing to the significance of lawsonite for water and element cycling in subduction zones occurrences of fresh lawsonite in blueschist and more rarely eclogite provide important opportunities to determine lawsonite composition zoning and inclusion suites and to use this information to reconstruct reaction history during subduction and exhumation in this review we use new and published data to document lawsonite composition in eight of the nine known lawsonite eclogite localities in which fresh lawsonite coexists with garnet omphacite in the rock matrix as well as the composition of lawsonite inclusions in six of seven known sites in which lawsonite occurs only as inclusions in garnet in eclogite facies rocks that lack matrix lawsonite as lawsonite blueschist is much more common than lawsonite eclogite we survey the composition of lawsonite in representative localities of blueschist including blueschist associated with eclogite lawsonite bearing epidote bearing and blueschist not associated with eclogite at current exposure levels included in this review are metabasaltic rocks silica and carbonate rich metasedimentary rocks metasomatic rocks and lawsonite rich veins this dataset demonstrates that lawsonite composition is a sensitive indicator of reaction history during subduction and exhumation and specifically of fluid rock interaction with implications for element cycling in subduction zones furthermore most exhumed lawsonite eclogite records slab surface conditions that correspond to the location where the slab mantle interface transitions from decoupled to coupled and therefore provides key insights into the thermal history and dynamics of subduction zones

lawsonite zone blueschists and a sodic amphibole producing reaction in the tavsanli region northwest turkey the petrology and mineralogy of lawsonite zone metabasites have been studied northeast of town of tavsanli nw turkey in the field the metabasites are characteristically green and lack foliation the essential mineral assemblage being sodic pyroxene lawsonite chlorite quartz sodic amphibole sodic pyroxene of aegirine jadeite composition occurs as pseudomorphs after magmatic augite lawsonite and chlorite are the other two dominant minerals sodic amphibole forms progressively from a reaction between sodic pyroxene chlorite and quartz and an isograd representing the first abundant occurrence of sodic amphibole in basic rocks has been mapped the widespread occurrence of sodic pyroxene pseudomorphs in other blueschist terrains indicates that the inferred sodic amphibole producing reaction is of general significance for blueschist metabasites

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

seismic properties of subducting oceanic crust constraints from natural lawsonite bearing blueschist and eclogite in sivrihisar massif turkey abstract investigating the seismic properties of natural lawsonite lws bearing blueschist and eclogite is particularly important for constraining the seismic interpretation of subducting oceanic crust based on seismological observations to achieve this end we analyzed in detail the mineral fabrics and seismic properties of foliated lws blueschist and lws eclogites from sivrihisar massif in turkey in both blueschists and eclogites the lawsonite fabric is characterized by three different patterns 0 0 1 axes aligning sub normal to foliation and 0 1 0 axes aligning sub parallel to lineation normal type 0 0 1 axes aligning sub parallel to lineation and 1 0 0 axes aligning sub normal to foliation with a girdle sub normal to lineation abnormal type and 0 0 1 axes aligning both sub normal to foliation and sub parallel to lineation 0 1 0 axes aligning sub parallel to lineation and 1 0 0 axes aligning sub normal to foliation transitional pattern in contrast glaucophane and omphacite mostly present consistent axial fabrics with the 0 0 1 axes aligning to lineation these mineral fabrics produce whole rock seismic anisotropies with similar patterns however the variations in seismic anisotropies are mainly controlled by the rock type to a lesser extent are determined by the lawsonite fabric type and to only a small extent are affected by mineral fabric strength despite the constructive abnormal type lawsonite fabric on whole rock seismic anisotropies because of their weaker mineral fabric strength or deformation degree the abnormal type lws blueschist still exhibit comparatively lower seismic anisotropies than those normal type lws blueschist from other localities based on the calculated seismic anisotropies and velocities we estimated that when oceanic crust transforms from lws blueschist to lws eclogite with increasing subduction depth 1 p wave and max s wave polarization anisotropies reduce about 70 and 40 respectively and 2 variations of vp and vs contrasts relative to mantle peridotites are about 7 to 3 and 8 to 6 respectively these results corroborate the important roles of lws bearing blueschist and eclogite in interpreting the existence and gradual weakening of low velocity layers in subducting oceanic crust during the subduction process

blueschist metamorphism in an active subduction zone the high pressure low temperature metamorphic rocks known as blueschists have long been considered to form in subduction zones where the descent of a relatively cold slab leads to the occurrence of unusually low temperatures at mantle pressures until now however the link between blueschist facies rocks and subduction zones has been indirect relying on a spatial association of blueschists with old subduction complexes and estimates of the geothermal gradients likely to exist in subduction zones here we strengthen this link by reporting the discovery of blueschist facies minerals lawsonite aragonite sodic pyroxene and blue amphibole in clasts from a serpentinite seamount in the forearc of the active mariana subduction zone the metamorphic conditions estimated from the mineral compositions are 150 250 c and 5 6 kbar 16 20 km depth the rocks must have been entrained in rising serpentine mud diapirs and extruded from mud volcanoes onto the sea floor further study of these rocks may provide new insight into the tectonics of trench forearc systems and in particular the processes by which blueschist facies clasts come to be associated with forearc sediments in ancient subduction complexes

40ar 39ar and rb sr geochronology of high pressure metamorphism and exhumation history of the tavsanli zone nw turkey geochronological investigations in high and ultra high pressure metamorphic rocks are problematic since firstly the low temperatures lead to fine grain size and disequilibrium assemblages and secondly the problem of excess argon affects 40ar 39ar systematics the most commonly used isotopic system the tavsanli zone is a belt of high pressure low temperature hp lt rocks spanning nw turkey and is one such region where previous geochronological studies have produced a range of estimates for the age of hp lt metamorphism raising the question of whether they are geologically significant this study presents new data from the tavsanli zone 40ar 39ar ages are in the range 60 ma to 175 ma whilst rb sr ages are restricted to 79 7 ma to 82 8 ma confirming the presence of excess argon detailed ultra violet laser ablation microprobe uvlamp studies have revealed younger 40ar 39ar ages in the cores of coarser white micas which in conjunction with 40ar 39ar ages from the finest grained lithologies and the rb sr white mica crystallisation ages constrain the post hp lt metamorphism exhumation rates of these rocks petrological and regional constraints suggest that syn subduction exhumation and cooling took place initially by synchronous subduction and exhumation by underplating this is followed by a phase of syn continent continent collision at a rate of approximately 1 5 mma 1 and exhumation to the surface via thrusting the 40ar 39ar hornblende data from a granodiorite intruding the hp lt rocks constrain the later parts of exhumation path this study highlights the importance of a multi system geochronological approach when attempting to determine the history of hp lt rocks

biological and chemical characteristics of high chlorophyll low temperature water observed near the sulu archipelago abstract according to ocean color remote sensing data a low phytoplankton biomass exists in the central parts of the sulu and celebes seas whereas higher concentrations of chlorophyll a are observed in the waters near the sulu archipelago which separates these water bodies these high chlorophyll a waters have lower temperatures than those of surrounding waters indicating vertical mixing of nutrient rich subsurface water that is attributable to the topographical features of the sulu ridge differences in photosynthetic parameters primary productivity and the phytoplankton community structure between the high chlorophyll area near the sulu archipelago and the oligotrophic basin area in the philippine sulu and celebes seas were investigated in november 2002 during the r v hakuho maru kh 02 4 cruise entrainment of subsurface water and vertical mixing by intense tidal flow from the sulu archipelago to the celebes sea created a low temperature high nutrient condition at the southeastern edge of the sulu ridge chlorophyll a concentrations greater than 2 g l 1 were observed at stations 5 15 km offshore at the edge of the sulu ridge this high chlorophyll tongue in the celebes sea showed high primary productivity it was 1 6 18 times higher than those measured in oligotrophic central basin regions of the philippine sulu and celebes seas microscopic observation of these high chlorophyll waters showed the dominance of chain forming large centric diatoms extension of high chlorophyll waters was not observed at the sulu sea side where the surface water salinity was lower than in the celebes sea and consequently prevented intrusion of the celebes sea water into the surface layer occasional extensions of productive chlorophyll rich surface water from the archipelagic zone to the surrounding basin area seems to be an important factor causing spatiotemporal variability in the phytoplankton biomass in the southern sulu sea and the western celebes sea

queen charlotte area cenozoic tectonics and volcanism and their association with relative plate motions along the northeastern pacific margin cenozoic relative plate interactions along the queen charlotte margin based on published models for the north america and northeast pacific plates are related to the tectonic and igneous history of the region plate motion models indicate convergence and subduction prior to the eocene since that time there has been transcurrent motion with varying small amounts of oblique extension or compression assuming that the pacific america farallon triple junction was to the south of the region a late miocene or early pliocene about 4 ma to present period of oblique convergence is well resolved the present queen charlotte fault zone along the west coast of the islands may have initiated more recently within the cenozoic transcurrent regime a period of oblique extension in the mid tertiary 36 20 ma in one model is supported by a variety of volcanic and tectonic evidence a small plate motion change at about 20 ma may have resulted in the transfer of the yakutat terrane from the north america plate to the pacific plate and the resulting motion of the terrane northwestward to its present position along the margin of alaska the onset of tertiary masset volcanism that is extensive on the queen charlotte islands corresponds within a few million years to the time of major plate reorganization at 43 ma that has tectonic expression around the entire pacific basin the period of most extensive masset volcanism and plutonism appears to correlate with the model oblique extension in the mid tertiary for one model the geochemistry and physical volcanology of the masset volcanic s are indicative of an extension regime the main syntectonic deposition in the queen charlotte basin skonun formation as inferred from seismic reflection and well data also appears temporally correlated with this time interval of oblique extension a variety of data including plate models dikes normal faults basin subsidence crustal thickness from seismic refraction and present and paleo heat flow indicate mid tertiary crustal extension of at least 20 in the queen charlotte region with up to 150 up to 2 5 in the main queen charlotte basin posttectonic basin subsidence and deposition may correlate with the model time interval of general transcurrent or oblique convergence motion from 20 to 4 ma more recent shortening deformation observed in outcrop and seismic sections of the northern parts of the basin may correlate with plate model oblique convergence from 4 ma to the present the latter convergence is associated with underthrusting that formed a trough or trench and an accretionary sedimentary prism off the west coast of the queen charlotte islands and with inferred uplift and erosion of the western part of the islands

interface inversion using broadside seismic refraction data and three dimensional travel time calculations a procedure has been developed to interpret densely sampled broadside seismic refraction data recorded from a large air gun array first arrival travel times are inverted to find the structure on an interface beneath the shot line travel times are calculated for three dimensional velocity models using a rapid finite difference algorithm adapted to allow variable sampling of the model and the determination of rays a simple inversion parameterization eliminates the need for matrix inversion the complete inversion procedure is computationally rapid yet allows the determination of detailed three dimensional structure broadside refraction data recorded in the queen charlotte basin offshore western canada during a multichannel reflection experiment are used to demonstrate the procedure the data are inverted for the basement interface beneath the shot line defining a rapidly varying thickness of sedimentary basin fill the results of the inversion stimulate a reinterpretation of the reflection data and identify a new major basement fault structure out of the plane of the reflection section is determined including the strike of the fault and other nearby features

metamorphic petrology of a high pressure low temperature subduction complex in west central baja california mexico the western baja terrane wbt of west central baja california is an uplifted subduction complex that is divided into smaller subterranes on the basis of bounding faults and petrological differences each subterrane contains coherent early jurassic to early cretaceous sedimentary and mafic volcanic rocks not melange that have been metamorphosed under blueschist facies conditions key phases in metabasites and metaturbidites include jadeitic to acmitic clinopyroxene sodic amphibole lawsonite aragonite chlorite titanite and white mica pressure indicators include the jadeite content of clinopyroxene and the presence of aragonite temperature indicators include the presence of lawsonite the absence of greenschist facies minerals and results from vitrinite reflectance studies conditions at the peak of metamorphism were 8 kbar 225 325 c for subterrane 1 7 8 kbar 170 220 c for subterrane 2 and 5 6 kbar 175 200 c for subterrane 3 these correspond to cold geothermal gradients 6 9 km vein assemblages that include aegerine jadeite and aegerine albite aragonite lawsonite and sodic amphibole indicate uplift during continued cold conditions probably during steady state subduction

tectonic setting petrology and geochronology of jadeite glaucophane and chloritoid glaucophane schists from north west turkey the north west turkish blueschists represent a subducted passive continental margin sequence dominated by metaclastic rocks and marble the depositional age of the blueschist protoliths are probably palaeozoic to mesozoic while the age of the high pressure low temperature metamorphism is late cretaceous blueschists are tectonically overlain by a volcanosedimentary sequence made up of accreted oceanic crustal material that locally shows incipient blueschist metamorphism and by spinel peridotite slices the metaclastic rocks with regional jadeite and glaucophane which comprise the lower part of the blueschist unit make up an over 1000 m thick coherent sequence in the kocasu region of north west turkey rare metabasic horizons in the upper parts of the metaclastic sequence with sodic amphibole iawsonite but no garnet indicate lawsonite blueschist facies metamorphism the blueschist metaclastics in the kocasu region are practically free of calcium and ferric iron and closely approximate the nfmash system in bulk composition two low variance mineral assemblages with quartz and phengite are jadeite glaucophane chlorite paragonite and chloritoid glaucophane paragonite the metaclastics comprise up to several metres thick layers of jadeite schist with quartz phengite and nearly 100 mol jadeite phase relations in the metaclastics show that the chloritoid glaucophane assemblage even in fe2 rich compositions is stable in the jadeite stability field in the nfash system the above assemblage without the accompanying garnet has a narrow thermal stability field mineral equilibria in the metaclastics involving chloritoid glaucophane jadeite paragonite and chlorite indicate metamorphic p t conditions of 20 2 kbar and 430 30 d c yielding geothermal gradients close to 5d c km 1 one of the lowest geotherms recorded blueschists in the kocasu region which have been buried to 70 km depth are tectonically overlain by the volcanosedimentary sequence and by peridotite buried not deeper than 30 km phengites from two jadeite schists were dated by ar ar laser probe they give an age of 88 5 0 5 ma interpreted as the age of metamorphism blueschists and the overlying peridotite bodies are intruded by 48 53 ma old granodiorite bodies that were emplaced at 10 km depth this suggests that the exhumation of blueschists by underplating of cold continental crust and normal faulting at the blueschist peridotite interface occurred during the late cretaceous to palaeocene 88 53 ma

the blueschists along the indus suture zone in ladakh nw himalaya abstract blueschists occur along the indus suture zone in ladakh as tectonic thrust slices as isolated blocks within melange units and as pebbles within continental detrital series in the shergol baltikar section high pressure rocks within the melange unit lie between the dras naktul nindam nappes in the north and the lamayuru units in the south the blueschists are imbricated with melange formation of probably upper cretaceous age they are overlain discordantly by the shergol conglomerate of post eocene oligo miocene age blueschist lithologies are dominated by volcanoclastic rock sequences of basic material with subordinate interbedding of cherts and minor carbonates mineral assemblages in metabasic rocks are characterized by lawsonite glaucophane crossite na pyroxene chlorite phengite titanite albite stilpnomelane in the quartz bearing assemblages garnet is present but omphacite absent p t estimates indicate temperatures of 350 to 420 c and pressures around 9 11 kbar geochemical investigations show the primary alkaline character of the blueschist which suggests an oceanic island or a transitional morb type primary geotectonic setting k ar isotopic investigations yield middle cretaceous ages for both whole rocks and minerals subduction related hp metamorphism affecting the mesozoic tethyan oceanic crust developed contemporaneously with magmatism in the dras volcanic are and the ladakh batholith subsequent collision of india with asia obducted relics of subduction zone material which later became involved in nappe emplacement during the himalayan mountain building

observations of exchange between the south china sea and the sulu sea 1 the velocity and transport with thermohaline properties are determined from simultaneous moored time series within mindoro tablas and panay straits that connect the south china sea scs and sibuyan sea to the sulu sea these passages provide the only pathway for the scs throughflow below thermocline depths and play a critical role in regulating the heat and freshwater balance within the philippine archipelago the upper layer in mindoro strait has a distinctly seasonal cycle with northward flow during the boreal summer southwest monsoon and southward flow during the winter northeast monsoon in contrast upper layer flow in panay and tablas straits is intraseasonal extraordinarily strong pulses that begin at intermediate depth in the fall transition and shoal toward the sub thermocline during the northeast monsoon are found in mindoro and panay straits these southward flows are strongly correlated to the scs large scale circulation and remote wind forcing off vietnam temperature and salinity in mindoro support the scs source of this subtropical water southward benthic flow in mindoro and panay act to ventilate the deeper sulu sea bottom temperatures suggest the cooler mindoro overflow mixes with the warmer benthic waters from tablas before exiting panay strait into the sulu sea the 2008 mean annual total depth transports were very small o 0 1 sv although individual transport estimates of 1 2 sv were observed in all depth layers over the year the mooring deployment coincided with a strong la nina when the pacific inflow into the scs is expected to be weaker and subsequently transports are lower

incipient blueschist metamorphism and metasomatism in the tavsanli region northwest turkey volcano sedimentary rocks in an imbricate tectonic zone around a peridotite massif have been studied northeast of the town of tavsanli in northwest turkey basic volcanic rocks which are the dominant rock type in this zone show incipient blueschist metamorphism and associated metasomatism while the igneous textures of the volcanic rocks are retained augites are partially to completely replaced by sodic pyroxene and plagioclase is albitised resulting in rocks with 6 8 wt na2o the volcanic rocks are cross cut by numerous veins of calcite aragonite quartz pumpellyite albite lawsonite and sodic pyroxene pelagic limestones which are interbedded with the basic volcanic rocks consist of coarse aragonite grains showing partial replacement by calcite the occurrence of aragonite lawsonite and albite indicates conditions of metamorphism for the whole zone in the range of 5 8 kb and 150 200 c metasomatism probably related to high pressure serpentinization has occurred contemporaneously with the incipient high pressure metamorphism

strain dependent variation of microstructure and texture in naturally deformed carrara marble this study investigates the microstructure and texture variations across a mm scale shear zone in carrara marble of the alpi apuane italy the microstructures have been investigated for grain size texture and shape fabrics textures have been measured with computer integrated polarization microscopy cip and electron back scattered diffraction ebsd separating porphyroclast and recrystallized grains the deformation which post dates an earlier deformation phase and subsequent annealing is strongly localized the microstructures and textures change across the shear strain gradient and are interpreted to preserve a time sequence of progressive stages of deformation the bulk shear strain rate is estimated to be about 10 11 sec 1 at deformation temperatures of approximately 325 c 30 c the protomylonite is characterized by a core mantle structure with a bimodal grain size distribution which changes gradually to a completely dynamically recrystallized microstructure with a unimodal grain size distribution in the mylonitic center of the shear zone core mantlestructures are produced by dominant rotation recrystallization accompanied by some grain boundary migration the microstructural transition from protomylonite to mylonite coincides with a change in texture with increasing strain the single c axis maximum of an earlier inherited texture in the protomylonite is replaced by a similar texture in a different orientation maximum normal to the shear plane which is consistent with dominant basal hai and r h 2201i slip the microstructural and textural variations depend on the proportion of recrystallized grains as dynamic recrystallization progresses with finite strain the texture development is finite strain dependent the comparison of the microstructures and textures to other natural and to experimental examples explains the progressive change of the texture and demonstrates the texture evolution produced by dynamic recrystallization 2006 elsevier ltd all rights reserved

reaction pathways during the progressive deformation of a blueschist metabasite the role of chemical disequilibrium and restricted range equilibrium there are discrete masses of un deformed metabasite within the blueschist series of the island of syros greece around the margins of these masses are zonal sequences through rocks showing intracrystalline deformation but without a geometric fabric to rocks with discrete and anastomosing shear zones and finally to penetratively foliated rocks with isolated relics of the original undeformed texture textural relics suggest that this spatial sequence is at least qualitatively also a temporal sequence this progressive shear zone deformation took place concurrently with a glaucophane epidote to eclogite reaction the reaction pathways in the rocks that underwent the shear zone deformation can be compared with those in rocks of a similar composition that suffered a longer deformation history and show no relics of an undeformed parent although the final assemblages are in both cases the same the pathways are different these differences are in part related to reactions promoted by the change from local to bulk equilibrium on the onset of deformation in the rocks they are also related to the crystallization and later breakdown during the sequence of progressive equilibration of a metastable phase in this case an impure glaucophane

texture of solnhofen limestone deformed to high strains in torsion solnhofen limestone was deformed in torsion to shear strains ranging from 1 to 12 at a temperature of 750 c 300 mpa confining pressure and a maximum strain rate of 10 3 s 1 these deformation conditions correspond to the intracrystalline power law dislocation creep field close to the boundary to the grain size sensitive superplastic creep field the grain shape microstructure was observed using orientation contrast by backscattered electrons in the sem the grains remain sub equant with an average grain size of around 4 m even to the highest strains lattice preferred orientation was determined using both x ray texture goniometry and automated electron back scatter diffraction the c axis preferred orientation develops from two main maxima with a weak sub maximum through two maxima to a single maximum perpendicular to the shear plane the rate of increase of the intensity of the single maximum with increasing strain diminishes and it appears that there is a tendency to a steady state texture the final single c axis maximum is displaced slightly towards the shortening direction of the applied simple shear the a axes tend to a girdle perpendicular to the c axis maximum it is proposed that the partitioning of deformation between intra and inter crystalline mechanisms results in a pulsating strain state in the grains contributing to the maintenance of sub equant grains it is argued that the lattices of constituent grains rotate continuously with no stable end orientation and that this can lead to a steady state texture the experimental preferred orientation compares well with that of natural calcite mylonites in the position of the c axis maximum and the a axis girdle

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

pressure temperature evolution of lawsonite eclogite in sivrihisar tavsanli zone turkey abstract the cretaceous blueschist belt tavsanli zone representing the subducted and exhumed northern continental margin of the anatolide tauride platform is exposed in western anatolia the sivrihisar area east of tavsanli is made up of tectonic units consisting of i metaclastics and conformably overlying massive marbles coherent blueschist unit ii blueschist eclogite unit iii marble calcschist intercalation and iv metaperidotite slab the metaclastics are composed of jadeite lawsonite glaucophane and jadeite glaucophane chloritoid schists phengite phyllites and calcschists with glaucophane lawsonite metabasite layers the blueschist eclogite unit representing strongly sheared deeply buried and imbricated tectonic slices of accreted uppermost levels of the oceanic crust with minor metamorphosed serpentinite bodies consists of lawsonite bearing eclogitic metabasites approximately 90 of the field lawsonite eclogites metagabbros serpentinites pelagic marbles omphacite glaucophane lawsonite metapelites and metacherts the mineral assemblage of the lawsonite eclogite garnet omphacite 70 is omphacite garnet lawsonite glaucophane phengite and rutile lawsonite eclogite lenses are enclosed by garnet lawsonite blueschist envelopes textural evidence from lawsonite eclogites and country rocks reveals that they did not leave the stability field of lawsonite during subduction and exhumation the widespread preservation of lawsonite in eclogitic metabasites and eclogites can be attributed to rapid subduction and subsequent exhumation in a low geothermal gradient of the oceanic crust material without experiencing a thermal relaxation peak p t conditions of lawsonite eclogites are estimated at 24 1 kbar and 460 25 c these p t conditions indicate a remarkably low geotherm of 6 2 c km corresponding to a burial depth of 74 km

post deformational annealing of calcite rocks abstract the evolution of microstructure and crystallographic preferred orientation cpo during post deformational annealing was studied on three calcite rock types differing in purity and grain size carrara marble 98 calcite mean grain size of 115 m solnhofen limestone 96 5 m and synthetic calcite aggregates 99 7 m samples were first deformed in torsion at 727 c at a shear strain rate of 3 10 4 s 1 to a shear strain of 5 and subsequently heat treated at 727 c for various durations between 0 and 24 h microstructures and cpos were analysed by optical microscopy image analysis and electron backscatter diffraction ebsd all rock types deformed in the dislocation creep field at the same applied conditions but their microstructures and cpos after deformation and after annealing differed depending on starting grain size and material composition in carrara marble and in the synthetic calcite aggregate a strong cpo developed during deformation accompanied by dynamic recrystallisation with significant changes in grain size during annealing widespread grain growth and subtle changes of cpo occurred and equilibrated foam microstructures were approached after long annealing times the cpo is the only feature in annealed samples indicating an earlier deformation phase although it is not always identical to the cpo formed during deformation in the more impure solnhofen limestone secondary phases on grain boundaries suppressed grain boundary mobility and prevented both the formation of a recrystallisation cpo during deformation and grain size modification during deformation and annealing

factors influencing the island mass effect of the galapagos archipelago 1 enhanced phytoplankton biomass in the wake of the galapagos islands is thought to result from an island mass effect ime fueled by upwelling of the equatorial undercurrent euc and by natural iron enrichment from the island platform annual means of five variables describing the thermocline the pycnocline and the availability of nitrate at the surface were derived from the world ocean atlas 1998 woa98 the first principal component of these variables explained 55 8 of the variance corroborating that the galapagos ime is associated with features of the euc mainly a shallow thermocline pycnocline and its vertical spreading in the vicinity of the galapagos regression analysis of seawifs derived chlorophyll a chl on the woa98 variables indicated that the depth of the thermocline and nitrate availability explain 91 9 of the chl variance a secondary ime of enhanced chl levels associated with the wind sheltered area north of isabela island was evident in the residual variability

late pleistocene to holocene productivity changes in the western equatorial pacific sulu sea philippines from calcareous nannofossils abstract we present a new calcareous nannofossil paleoproductivity reconstruction of the southeastern margin of the sulu sea to understand how marine productivity varied through time in one of the major fishing grounds of the philippine archipelago the study is based on two sediment cores obtained from two different hydrographic locations in the western equatorial pacific region an upwelling region off zamboanga peninsula u gc12 and a non upwelling area off panay island nu gc14 covering the past 18 000 years before present b p calcareous nannofossil assemblages in the investigated areas were of low diversity and largely dominated by gephyrocapsa oceanica and florisphaera profunda followed by small placolith bearing taxa emiliania huxleyi small gephyrocapsa and reticulofenestra minuta upwelling episodes off the zamboanga peninsula were recorded several times in the past as shown by an increase in the abundance of high productivity indicator species g oceanica small gephyrocapsa e huxleyi and of bulk sediment caco3 and a concomitant decline in the total organic carbon toc the high abundance of low surface water productivity species f profunda and umbellosphaera irregularis indicates a stratified water column with a deeper nutricline probably caused by the reduced upwelling intensity this condition was corroborated by the decrease in caco3 and an increase in toc we propose that the modern day high productivity conditions off zamboanga peninsula started at 2500 years b p whereas the low productivity off panay island was recorded from 4000 years b p and persists to the present day evidence of the younger dryas yd event was recorded from 11 100 to 10 400 years b p in u gc12 synchronous to the yd event reported from other areas in the northern hemisphere and in accordance with the timing in the sulu sea as reported from previous studies in this region this event in the sulu sea is characterized by a decrease in total nannofossil abundance and estimated primary productivity together with an increase in caco3 and a decrease in toc we interpreted that dilution caused by the increase in precipitation experienced in the southeast asian region during the yd event could have led to the decline of the total calcareous nannofossils whereas the recorded increase in caco3 is attributed to the high abundance of planktonic foraminifera during this interval

sedimentary records of bulk organic matter and lipid biomarkers in the bering sea a centennial perspective of sea ice variability and phytoplankton community abstract in this study organic geochemical analyses of two sediment cores bl16 and lv63 23 recovered from the western bering sea were carried out to examine the sea ice variability and its relationship to phytoplankton community evolution over the past century bulk stable organic carbon isotopic composition 13ctoc showed pronounced depletion on the northern shelf since the late 1970s indicating greater terrigenous organic matter om under warming during recent decades variation in sedimentary om in the southward core was closely associated with marine primary productivity and regional deposition processes arctic sea ice proxy ip25 throughout the two cores with different temporal profile patterns demonstrated sea ice presence with the spatio temporal variability across the study area over the past century the phytoplankton marker ip25 index pip25 a proxy for estimating semi quantitatively sea ice concentrations reflected a decreased sea ice cover with more distinct interannual fluctuations between 0 7 and 0 2 especially in core bl16 after the late 1970s coinciding with the recent warming scenario increased concentrations of phytoplankton biomarkers brassicasterol and dinosterol and their ratios as well as the pip25 record in core bl16 indicated a synchronous variability of reduced sea ice cover with the enhancement of phytoplankton productivity since the late 1970s these results suggested a coupled interaction of the sea ice condition and planktonic ecosystem in the north bering shelf our results also revealed recent since the 2000s spatial heterogeneity in sea ice coverage between the northern and southern parts of the bering sea

post collision magmatism and tectonics in northwest anatolia a suite of biotite hornblende granodiorite intrusions has been emplaced into blueschist facies metasediments in northwest anatolia following collision between two continental margins now represented by the tavsanli and sakarya zones the 40ar 39ar ages of phengites and glaucophanes from the blueschists metamorphosed under unusually high p low t conditions p 20 2 kbar t 430 30 c suggest that metamorphism apparently occurred over a period spanning at least 20 ma from 108 to 88 ma post tectonic granodiorites were emplaced during the eocene 53 to 48 ma resulting in a cordierite and andalusite bearing thermal aureole indicative of pressures of 3 kbar trace element systematics of the granodiorites are consistent with a derivation either from mantle derived magmas by fractional crystallisation in shallow magma chambers or from anatexis of crustal lithologies of internediate composition at pressures 10 kbar the preservation of high p low t assemblages in the blueschists together with the range of ages determined for blueschist facies metamorphism are indicative of rapid exhumation of delaminated fragments from a subducted continental margin however decompression melting of the crust is unlikely to have been a significant cause of magmatism both because exhumation of the blueschists from deep crustal levels predated magmatism by at least 25 ma and because of the small melt fraction 0 1 that may be generated in crustal lithologies by this process melting in the mantle wedge is required either to generate a primary melt for the derivation of magmas of intermediate composition or to provide an advective heat source for crustal melting the cause of melt formation in the upper mantle may be related to the termination of subduction following collision during the mid eocene

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

manganese cerium and iron in the sulu celebes and philippine seas this study was undertaken to investigate trace metals in southeast asian seas that have different hydrographic settings the philippine the celebes and the sulu seas results reveal characteristics of dissolved and leachable manganese dissolved cerium and leachable iron in the water column remarkable increases of mn ce and fe exist at the bottom layer of the water column in the celebes sea the ce mn molar ratios in the bottom waters of the celebes sea are identical to those in the porewaters of the underlying sediment both ce and mn show similar geochemical cycles in these deep waters of the celebes sea in the sulu sea s deep waters the leachable particulate fractions are dominant for fe and mn the residence time of fe in the sulu sea is estimated as 12 years this residence time estimate is very similar to the particle residence time in the water column implying that resuspension of sediment derived particles affects leachable fe distributions in the sulu sea

uplift related retrogression history of aragonite marbles in western crete greece in the low grade high pressure 400 c 10 kbar metamorphic phyllite quartzite unit of western crete widespread occurrences of aragonite marbles have been discovered recently a sedimentary precursor is proved by relic structures bedding fossils partial or complete transformation of aragonite into calcite is ubiquitous compositional and microstructural features reflect the metamorphic history 1 the high pressure stage is documented by aragonite that is chemically characterized by incorporation of variable amounts of sr and the lack of mg the most sr rich aragonite has about 9 wt sro xsrarag 0 09 a compositional zoning observed in some aragonite crystals may be due to the prograde divariant calcite aragonite transformation in the system caco3 srco3 because the parent rocks probably were sr poor calcite limestones one can speculate that strontium has been supplied from an external source under high pressure conditions 2 during uplift calcite replacing aragonite did not equilibrate with unreplaced aragonite disequilibrium is indicated by highly variable compositions of calcite crystals that show topotactic relations to the host aragonite the calcite compositions range from that of the host aragonite sr rich and mg free to mg bearing and sr poor 3 calcite that recrystallized during retrogression is generally sr poor mean value ofxsr 0 005 mg bearing xmg 0 010 and chemically homogeneous because practically no sr remains in the calcite an interaction with a fluid phase is indicated in fine grained calcite marbles rich in solid organic matter microstructural features indicative of former aragonite may be present 4 the last stage of retrogression is documented by the appearance of radiating aragonite in veins and nodules this aragonite which shows neither deformation nor retrogression was probably formed metastably in a near surface environment

a core top screen for trace element proxies of environmental conditions and growth rates in the calcite skeletons of bamboo corals isididae abstract we test for trace element proxies in the high magnesium calcite fraction of bamboo coral internodes by comparing environmental conditions and growth rates to the specimen mean compositions of 73 corals that were live caught at depths ranging from 3 to 3950 m and collected from habitats ranging from tropical coral reefs to the antarctic slope comparisons were done at a large geographic scale lgs and for a well sampled area south of australia across depths at a single site in order to help separate the effects of environmental variables that co vary at one spatial scale but not the other thirty seven trace elements were measured using solution based sector field icp ms of which seventeen were significantly detected in more than a third of the specimens only eight element calcium ratios correlated significantly with any environmental variable at the large geographic scale and only four did so at the local level at the lgs the highest correlation was between ambient temperature and mg ca which accounted for 89 of the variance across specimens spanned all four isidid sub families and was independently significant in the two best sampled sub families the predictive geometric mean relationship is t c 23 9 2 46 0 34 0 25 mg ca mmol mol spanning a temperature range of 1 9 to 26 8 c mg ca ratios from 58 6 to 155 1 mmol mol and an uncertainty rms of 2 78 c the numbers in parentheses are 95 cis the slope of the regression does not differ significantly from that of abiotic high mg calcites which suggests that the temperature dependent incorporation of mg into the carbonate results from kinetic reactions at the crystal surface analysis at the sh scale for the sub set of specimens for which we had data suggests is also affected by growth rates there were no obvious trace element correlates at either spatial scale of salinity or oxygen levels that could not be accounted for by covariance between these environmental parameters and in most cases temperature single and multiple correlation analyses also confirm previous suggestions that ba ca in bamboo coral calcite is a proxy for seawater barium and hence refractory nutrients suggest that sr ca is influenced by specimen mean mg ca ratios and water temperature as well as possibly seawater sr ca and falsify for bamboo corals p ca as well as p cd and cd ca as a proxy for seawater phosphate levels the predictive relationship between isidid skeletal mean ba ca and seawater silicate concentrations appears to be linear and is given by silicate mol kg 1 56 7 20 8 9217 1632 ba ca mmol mol spanning a silicate range of 0 5 to 120 mol kg 1 a ba ca range of 0 0042 to 0 0195 mmol mol and with an uncertainty rms of 33 1 mol kg 1 mn ca differences among specimens and sites are highly significant and appear to reflect seawater mn suggesting a proxy for this micronutrient the compilation of growth rate data across 34 specimens indicates a wide range of growth rates even among con familial specimens from within a single habitat and suggests both ambient temperature and food availability underlie at least part of this variability

neotethyan ophiolitic rocks of the anatolides of nw turkey and comparison with tauride ophiolites the i2zmir ankara erzincan zone in turkey is part of the anatolide belt in nw anatolia near kutahya the ophiolitic rocks within the i2zmir ankara erzincan suture zone have a tholeiitic character and oceanic back arc chemistry amphibolites form a metamorphic sole to part of the ophiolite in the kutahya region and yield an 40 ar 39 ar age of 93 2 ma interpreted to record high grade metamorphism and intra oceanic thrusting of pre existing ocean crust gabbros and dykes yield 40 ar 39 ar ages of 94 13 ma and 48 12 ma the first is suggested to be the ophiolite formation age and the second a regional metamorphic event the ophiolitic rocks of the kutahya region are composite and record several events in the evolution of a neotethyan seaway situated in north central anatolia and farther east they are interpreted to have formed in a small ocean basin marginal to the subducting i2zmir ankara erzincan ocean the kutahya ophiolites of the anatolide belt are similar in age to the tauride ophiolites and the sub ophiolite metamorphic rocks and dykes in the ultramafic parts of the ophiolites in the anatolide tauride block formed at the same intraoceanic subduction zone within the same neotethyan ocean

interpretation in statu nascendi of seismic wide angle reflections based on eugeno s data abstract in a new interpretation approach seismic wide angle data are analysed in statu nascendi i e in the state where the interpretational characteristics of the signals are born the approach is complementary to other interpretation methods such as kinematic interpretation of velocity models seismogram sections are qualitatively compared and classified in order to perform the analysis as close as possible to the seismic wavefield correlation of seismic phases and selection of representative reflection characteristics of the phases are required for the analysis the approach has been tested on the methodologically homogeneous eugeno s data set from the danish and surrounding areas together with other data the classifications of intra crustal and pmp reflections show clear regionalizations which correlate with the main geological tectonic and orogenic units the reflection characteristics of the thin crust below the deep basins in denmark the tornquist fan are different from the thick crust of the baltic shield and the ringkobing fyn high the character of moho reflections is ringing in the basin area as opposed to sharp in the latter areas and intra crustal reflections are stronger and more consistent in the basin area than in the latter areas

interpretation of three dimensional seismic refraction data from western hecate strait british columbia structure of the crust as part of a multidisciplinary investigation of the structure and tectonics of the queen charlotte basin and underlying crust deep multichannel seismic reflection and coincident crustal refraction data were collected in 1988 energy from the reflection air gun array source was recorded at land sites at offsets appropriate to record crustal refraction and wide angle reflection data refraction data recorded in a broadside geometry provide good three dimensional coverage of western hecate strait these data are modelled using tomographic inversion techniques to determine the three dimensional velocity structure of the crust in this region the one dimensional average velocity increases rapidly with depth to 6 5 km s at 7 km depth velocities from 7 to at least 12 km depth remain approximately constant and are associated with rocks of the wrangellia terrane significant lateral velocity variations including large differences in near surface velocities attributable to surface features relatively low veloci

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

calcite twin morphology a low temperature deformation geothermometer abstract twinning of the e plane is the dominant crystal plastic deformation mechanism in calcite deformed below about 400 c calcite in a twin domain has a different crystallographic orientation from the host calcite grain so called thin twins appear as thin black lines when viewed parallel to the twin plane at 200 320 magnification under a petrographic microscope thick twins viewed in the same way have a microscopically visible width of twinned material between black lines calcite e twin width and morphology has been correlated with temperature of deformation in naturally deformed coarse grained calcite in this paper we present a compilation and analysis of data from limestones of the frontal alps france and switzerland and the appalachian valley and ridge and plateau provinces eastern united states to document this temperature dependence mean calcite twin width correlates directly with temperature of deformation such that thin twins dominate below 170 c and thick twins dominate above 200 c above 250 c dynamic recrystallization is an important deformation mechanism in calcite mean twin intensity twin planes mm correlates negatively with temperature and a cross plot of twin intensity with twin width can yield information about both strain and temperature of deformation these relationships provide a deformation geothermometer for rocks that might otherwise yield little or no paleotemperature data

seismic velocity structure of the queen charlotte basin beneath hecate strait seismic refraction data across hecate strait in the northern queen charlotte basin were collected in a coincident reflection and refraction survey crustal velocity models provide a framework to help understand the formation of the sedimentary basin and the processes occurring near the queen charlotte fault a major ocean continent transform fault beneath the sediments which have a maximum thickness of 6 km a velocity gradient extends from about 5 to 8 km depth within which velocities increase typically from 6 3 to 6 4 km s 1 a thick constant velocity region was found down to a depth varying from 14 to 22 km with the smallest depths located beneath the central basin the base of the constant velocity layer was marked by a distinct mid crustal interface across which velocities increased from 6 4 6 5 km s 1 to approximately 6 8 6 9 km s 1 moho was interpreted to be at a near uniform depth of 26 28 km beneath hecate strait and the eastern queen charlotte islands the associated variation in crustal t

lawsonite vorticity and subduction kinematics the exceptional preservation of lawsonite in eclogite and blueschist in a subduction complex sivrihisar turkey allows evaluation of high pressure h p deformation and exhumation using vorticity analysis of a h p index mineral the sivrihisar h p rocks were deformed during h p metamorphism and initial decompression by oblique normal and or dextral shearing beneath serpentinized peridotite we evaluated kinematic vorticity w m pure shear 0 w m simple shear 1 using the shape fabric of lawsonite crystals in blueschist layers and meter scale eclogite pods pods record dominant simple shear w m 0 8 in their eclogitic core and at pod margins partially transformed to blueschist map scale blueschist layers record a large component of pure shear w m 0 4 0 6 consistent with oblique extrusion at depth in the subduction zone and local simple shear w m 0 8 at the fault contact with serpentinite a combination of oblique unroofing from beneath a weak serpentinized hanging wall and pure shear extrusion in the subduction channel accounts for rapid exhumation along a low geothermal gradient and the rare preservation of lawsonite eclogite during exhumation to the earth9s surface

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

spatial distribution and controlling factors of planktonic foraminifera in the modern western pacific abstract studies of the spatial distribution of living planktonic foraminifera in modern water columns are still lacking in the western pacific in this study 40 plankton tows at 8 stations were conducted focusing on the terminus of the north equatorial current nec and its two bifurcated branches in the western pacific the results show that planktonic foraminifera were in high abundance around the kuroshio current kc source region and the mindanao current mc system but in low abundance in the nec the planktonic foraminiferal assemblage was dominated by g sacculifer and g ruber with relative abundances of 44 0 and 27 3 respectively according to a cluster analysis of the results of seven stations the stations can be divided into three groups namely group nec group kc and group mc which displayed different features of planktonic foraminiferal assemblages the low abundance of planktonic foraminifera that characterized the nec stations may be induced by the thick mixed layer and deep thermocline nutricline in this region however stations in the kc region which also had thick mixed layers and deep thermoclines showed higher abundances of planktonic foraminifera than the nec stations this result was probably caused by the higher terrigenous input the planktonic foraminifera show the highest abundance at the mc stations which may be the result of existing upwelling conditions

structure beneath queen charlotte sound from seismic refraction and gravity interpretations a combined multichannel seismic reflection and refraction survey was carried out in july 1988 to study the tertiary sedimentary basin architecture and formation and to define the crustal structure and associated plate interactions in the queen charlotte islands region simultaneously with the collection of the multichannel reflection data refractions and wide angle reflections from the airgun array shots were recorded on single channel seismographs distributed on land around hecate strait and queen charlotte sound for this paper a subset of the resulting data set was chosen to study the crustal structure in queen charlotte sound and the nearby subduction zone two dimensional ray tracing and synthetic seismogram modelling produced a velocity structure model in queen charlotte sound on a margin parallel line moho depth was modelled at 27 km off southern moresby island but only 23 km north of vancouver island excluding the approximately 5 km of the tertiary sediments the crust in the latter area is onl

evolution of a calcite marble shear zone complex on thassos island greece microstructural and textural fabrics and their kinematic significance abstract the deformation history of a monophase calcite marble shear zone complex on thassos island northern greece is reconstructed by detailed geometric studies of the textural and microstructural patterns relative to a fixed reference system shear zone boundary szb strain localization within the massive marble complex is linked to decreasing p t conditions during the exhumation process of the metamorphic core complex solvus thermometry indicates that temperatures of 300 350 c prevailed during part of the shear zone deformation history the coarse grained marble protolith outside the shear zone is characterized by symmetrically oriented twin sets due to early coaxial deformation a component of heterogeneous non coaxial deformation is first recorded within the adjacent protomylonite enhanced strain weakening by dynamic recrystallization promoted strong localization of plastic deformation in the ultramylonite of the calcite shear zone where high strain was accommodated by non coaxial flow this study demonstrates that both a pure shear and a simple shear strain path can result in similar crystallographic preferred orientations single c axis maximum perpendicular to the szb by different dominant deformation mechanisms separated a axis pole figures a and a axis show different density distributions with orthorhombic texture symmetry in the protolith marble and monoclinic symmetry in the ultramylonite marble consistently with the observed grain fabric symmetry

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

evidence of paleogene sedimentation on graham island queen charlotte islands west coast canada the palynomorph taxa ctenosporites eskerensis pesavis tagluensis and tilia spp demonstrate that an unnamed sedimentary unit in the union port louis well and float from mud bay creek skidegate i

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

exhumation of blueschists along a tethyan suture in northwest turkey a blueschist belt formed during the mid cretaceous 88 ma high pressure metamorphism of a passive continental margin sequence of shale siltstone quartzite and limestone occurs immediately south of the tethyan suture in northwest turkey a transect across the tethyan suture was mapped to constrain the exhumation of blueschist facies assemblages the presence of jadeite glaucophane and lawsonite in the blueschists indicates p t conditions of 20 kbar and 430 c the blueschists are tectonically overlain by a cretaceous oceanic accretionary complex showing an incipient blueschist metamorphism a peridotite slab with subvertical layering lies along a low angle fault contact over the blueschists and the accretionary complex isolated slices of early cretaceous 101 4 ma garnet amphibolites occur at the base of the peridotite the garnet amphibolites which show an incipient blueschist facies overprint have probably formed during the oceanic subduction in the foot wall of the subduction zone and later underplated the hanging wall blueschists and peridotites are abruptly truncated in the north by the steeply dipping suture fault that juxtaposes unmetamorphosed and slightly deformed triassic to jurassic sediments of the northern continent against the peridotite and the accretionary complex tectonic juxtaposition of the lower pressure accretionary complex and peridotites over the higher pressure blueschists implies the removal of a 45 km thick oceanic mantle sequence above the blueschists regional geological and geometric constraints suggest that the exhumation of the blueschists was achieved by a combination of two simultaneously acting mechanisms the first was the detachment of the upper crustal blueschist sequence from its basement in the subduction zone and its incorporation to the hanging wall followed by buoyant ascent the second mechanism is the progressive shallowing of the subducted continental lithosphere resulting in the thinning of the mantle wedge above the subducted slab the blueschists were partly exposed prior to the paleocene continent continent collision post collisional eocene 52 48 ma calc alkaline plutons that were emplaced in the blueschists and the overlying peridotite at 10 km depth are interpreted to have formed by crustal anatexis from advective heating by mantle melts these have probably been generated during the upwelling of the asthenosphere under the shallowing continental lithosphere

relationships between very high pressure subduction complex assemblages and intrusive granitoids in the tavsanli zone sivrihisar massif central anatolia abstract the sivrihisar massif of central anatolia exposes blueschist and eclogite facies metasedimentary and metabasaltic rocks in close association with granitoid plutons the massif is located within the tavsanli zone the subducted and exhumed northern continental margin of the anatolide tauride block the relationship of the very high pressure assemblages to co existing granitoid plutonic bodies kaymaz and sivrihisar is unclear as the region can be considered the type locality for the entrainment of excess argon in k bearing minerals samples from its granitoids and a subduction complex assemblage were collected imaged with cathodoluminescence cl and dated using zircon u pb in situ in thin section ion microprobe methods the granitoids are heterogeneous as evidenced by cl images and geochemical variations finer grained sivrihisar samples are syenite and show plagioclase replacing k feldspar whereas coarser grained rocks are monzonite and show the opposite reaction our samples of the kaymaz granitoids are extremely si rich 82 97 wt sio 2 and have experienced sericitization cl images of both granitoids show evidence for fluid interactions at both the subsolidus and lower temperature stages in their tectonic history subduction along the tavsanli zone was ongoing during the early to late cretaceous and entrained zircons with igneous zonation in cl that crystallized as early as the paleoproterozoic sivrihisar massif granitoids record zircon crystallization from the late cretaceous to early oligocene here we present a model in which the sivrihisar and kaymaz melts source from a subducting slab along the afyon zone further to the south and mix with an igneous component generated during decompression due to break off of the tavsanli slab the model speculates that the tavsanli zone is the northernmost segment of an amalgamation of stacked subduction zones that transition in activity from north to south over time

recrystallization of high pressure marble sivrihisar turkey abstract in the sivrihisar massif turkey the southern margin of a blueschist facies terrane was affected by heating and deformation associated with later regional barrovian metamorphism creating a recrystallization front that can be observed in calcite microstructures calcite marble records a progression from high pressure h p textures in a northern domain to completely recrystallized greenschist to amphibolite facies textures in a southern domain with intermediate stages of partial recrystallization of the h p textures h p marble is characterized by rod shaped calcite aragonite pseudomorphs arranged in series with the long axis of each grain oblique to compositional layering obliquity varies from 50 to nearly parallel but high angles are most common in a narrow 200 m thick transition zone that contains partially retrogressed blueschist and eclogite the h p texture is partially overprinted by chains of small equant recrystallized grains that preserve the crystallographic orientation of the pre existing rod shaped calcite as revealed by electron backscatter diffraction analysis rod shaped crystals occur locally in a 100 m thick zone south of the transition zone all calcite grains are equant but have a crystallographic preferred orientation further south in the barrovian sequence recrystallized marble contains equant calcite that is randomly oriented the similarity in fabric elements foliation lineation of the two domains further shows the effect of barrovian related processes on the h p domain including the rotation of the calcite rods during shearing along foliation planes white mica 40 ar 39 ar ages for phengite in h p marble are 88 ma and for muscovite in barrovian marble are 59 ma indicating 30 ma time interval between initial exhumation and cooling of the h p rocks and final cooling of the rocks that were deformed and heated during the later metamorphic event

petrotectonics of lawsonite eclogite exhumation insights from the sivrihisar massif turkey 1 the sivrihisar massif of the tavsanli zone of turkey is 1 of less than 10 known lawsonite eclogite localities worldwide rocks of the sivrihisar massif consist of eclogite and blueschist in contact with metasedimentary host rocks and record decreasing maximum pressure conditions across three wnw ese striking belts from 16 24 kbar in the northern halilbagi belt to 14 16 kbar in the karacaoren belt and 8 10 kbar in the kertek belt where present sodic amphibole phengite chlorite and quartz define a pervasive s0 s1 foliation garnet omphacite and lawsonite define stretching lineations and kinematic indicators d1 and d2 structures are similar in the halilbagi and karacaoren belts but differ to those in the kertek belt d3 structures are uniform across the massif including fibrous calcite that occurs parallel to f3 fold axes shear sense indicators from field observations and asymmetric type i cross girdle of quartz c axes obtained from electron backscatter diffraction ebsd show top to the south thrusting throughout much of the massif d1 and d2 structures are interpreted to have formed during exhumation by extrusion along a 5 c km gradient the halilbagi and karacaoren belts were juxtaposed possibly as deep as 45 km within the subduction channel and exhumed by the arrival of the anatolide microcontinent at approximately 70 ma homogeneity of f3 axes and calcite fibers across the massif suggests that assembly occurred at blueschist conditions before exhumation through the aragonite calcite transition 350 c above 8 kbar

tectono metamorphic evolution of the siliciclastic units in the middle tuscan range inner northern apennines mg carpholite bearing quartz veins related to syn metamorphic syn orogenic foliation abstract this paper accounts for a new finding of high pressure low temperature hp lt metamorphism documented in continental derived rocks exposed in the central part of the middle tuscan range representing the easternmost location in the tyrrhenian region where blueschist facies metamorphism has been documented it describes the development mechanism of mg carpholite bearing quartz veins in the framework of the deformational events described for the inner northern apennines the hp lt peak metamorphism can be estimated in p 1 1 gpa and t 370 420 c as supported by the mineralogical assemblage consisting of quartz muscovite chloritoid pyrophylite hematite chlorite paragonite ti oxides documented in the aluminous metasediments pelites and quartzose sandstones of the triassic verrucano succession this paragenesis defines the s 1 schistosity an axial planar tectonic foliation associated to map and mesoscale isoclinals folds f 1 s 1 schistosity is a composite foliation resulted from a non coaxial progressive deformation associated to the de 1 collisional event late oligocene early miocene mg carpholite bearing quartz veins developed as tension gashes in en echelon arrays within brittle ductile shear zones the development of quartz veins was guaranteed by the high volumes of si rich fluids produced by the dynamic recrystallization process on the siliciclastic rocks

the sulu sea internal soliton experiment abstract we present the results of a comprehensive study of large amplitude internal solitons generated in the sulu sea in the philippines by intense tidal flow over a sharp bathymetric feature surface signatures of these waves have been observed in images from the dmsp landsat and nimbus 7 satellites and the space shuttle sir a synthetic aperture radar a two week experiment was conducted in the sulu sea in may 1980 from r v oceanograher during which a three mooring phased array of current meters and thermistors was implanted near the wave source and at 82 km and 200 km from the source seventeen soliton packets were observed whose properties underwent significant change as they propagated across the sea vertical profiles of density temperature and acoustic backscatter as well as radar and photographic surface signatures were obtained from the ship data from satellites moorings and the ship give unprecedented information on the spatial and temporal characteristics of solitary waves which ha

tectonic evolution and paleogeography of the kirsehir block and the central anatolian ophiolites turkey in central and western anatolia two continent derived massifs simultaneously underthrusted an oceanic lithosphere in the cretaceous and ended up with very contrasting metamorphic grades high pressure low temperature in the tavsanli zone and the low pressure high temperature in the kirsehir block to assess why we reconstruct the cretaceous paleogeography and plate configuration of central anatolia using structural metamorphic and geochronological constraints and africa europe plate reconstructions we review and provide new 40ar 39ar and u pb ages from central anatolian metamorphic and magmatic rocks and ophiolites and show new paleomagnetic data on the paleo ridge orientation in a central anatolian ophiolite intraoceanic subduction that formed within the neotethys around 100 90 ma along connected n s and e w striking segments was followed by overriding oceanic plate extension already during suprasubduction zone ocean spreading continental subduction started we show that the complex geology of central and southern turkey can at first order be explained by a foreland propagating thrusting of upper crustal nappes derived from a downgoing dominantly continental lithosphere the kirsehir block and tavsanli zone accreted around 85 ma the afyon zone around 65 ma and taurides accretion continued until after the middle eocene we find no argument for late cretaceous subduction initiation within a conceptual inner tauride ocean between the kirsehir block and the afyon zone as widely inferred we propose that the major contrast in metamorphic grade between the kirsehir block and the tavsanli zone primarily results from a major contrast in subduction obliquity and the associated burial rates higher temperature being reached upon higher subduction obliquity

late cretaceous blueschist facies metamorphism in southern thrace turkey and its geodynamic implications a blueschist facies tectonic sliver 9 km long and 1 km wide crops out within the miocene clastic rocks bounded by the strands of the north anatolian fault zone in southern thrace nw turkey two types of blueschist facies rock assemblages occur in the sliver i a serpentinite body with numerous dykes of incipient blueschist facies metadiabase ii a well foliated and thoroughly recrystallized rock assemblage consisting of blueschist marble and metachert both are partially enveloped by an upper eocene wildflysch which includes olistoliths of serpentinite metadiabase upper cretaceous and palaeogene pelagic limestone upper eocene reefal limestone radiolarian chert quartzite and minor greenschist field relations in combination with the bore core data suggest that the tectonic sliver forms a positive flower structure within the miocene clastic rocks in a transpressional strike slip setting and represents an uplifted part of the pre eocene basement the blueschists are represented by lawsonite glaucophane bearing assemblages equilibrated at 270 310 c and 0 8 gpa the metadiabase dykes in the serpentinite on the other hand are represented by pumpellyite glaucophane lawsonite assemblages that most probably equilibrated below 290 c and at 0 75 gpa one metadiabase olistolith in the upper eocene flysch sequence contains the mineral assemblage epidote pumpellyite glaucophane recording p t conditions of 290 350 c and 0 65 0 78 gpa indicative of slightly lower depths and different thermal setting timing of the blueschist facies metamorphism is constrained to c 86 ma coniacian santonian by rb sr phengite whole rock and incremental 40 ar 39 ar phengite dating on blueschists the activity of the strike slip fault post dates the blueschist facies metamorphism and exhumation and is only responsible for the present outcrop pattern and post miocene exhumation 2 km the high p t metamorphic rocks of southern thrace and the biga peninsula are located to the southeast of the circum rhodope belt and indicate late cretaceous subduction and accretion under the northern continent i e the rhodope massif enveloped by the circum rhodope belt the late cretaceous is therefore a time of continued accretionary growth of this continental domain