crustal thickness and velocity structure beneath singapore s seismic network abstract we estimated the crustal thickness and velocity structure beneath the five stations comprising the republic of singapore s seismic network our data set was composed of 697 teleseismic receiver functions and 7 months of broad band data that was cross correlated to produce inter station green s functions surface wave group velocities were extracted from the green s functions to obtain dispersion data for a path from central sumatra to singapore in order to provide a complimentary data set to the receiver functions crustal thickness was estimated via an h k stacking technique and high resolution 1d p wave velocity profiles were generated beneath each station by jointly inverting receiver function stacks and the group velocity data using a linearised time domain inversion scheme crustal thickness beneath four stations was found to be between 28 0 km and 32 0 km while one station in the northeast of singapore indicates 24 0 km thick crust this implies a significant crustal thinning beneath singapore over the lateral extent of 50 0 km inversion results exhibit several crustal features that are observable in the derived models at all five stations indicating that they exist across singapore as a whole there appears to be an upper crustal high velocity zone beneath singapore underlain by a velocity inversion station ntu shows slower near surface velocities than the other stations consistent with its situation above the sedimentary jurong formation these results expand the available global velocity data set as well as being useful for assessing the seismic hazard in singapore

crustal velocity structure of the british isles a comparison of receiver functions and wide angle seismic data summary magmatic underplating at the base of the continental crust is thought to be an important consequence of mantle plume activity geochemical evidence supports the hypothesis of underplating beneath the british tertiary igneous province during palaeocene times a process that has been invoked to explain at least part of the observed pattern of cenozoic denudation and consequent offshore deposition this study uses receiver functions to independently test the results of modelling of four wide angle seismic lines across the british isles several of which indicate the presence of a lens of high velocity material at the base of the crust this lens has been interpreted as evidence of palaeogene magmatic underplating receiver functions were calculated for three permanent and two temporary three component broad band seismometers in order to detect p to s conversions from intracrustal velocity discontinuities high frequencies were preserved in the calculation of the receiver functions receiver functions were modelled using the delay times of the p to s converted arrivals only with constraints on the vp and vp vs structure imposed from controlled source data this pragmatic method of interpreting receiver function data agrees well with the results of applying an established inversion technique resulting crustal velocity models are broadly consistent with the velocity models from the wide angle lines showing evidence for a four layer crust with laterally varying moho depths of between 33 2 5 km beneath southwest ireland 32 2 5 km beneath northern and eastern ireland 31 2 km beneath the isle of man and 35 3 km beneath northern england while these velocity models are consistent with the presence of a lower crustal layer receiver functions are insensitive to the p wave velocity structure and so unfortunately they cannot be used to independently constrain the p wave velocity of the lower crust which is an important diagnostic of the presence of magmatic underplating

stable isotope geochemistry and phase equilibria of coesite bearing whiteschists dora maira massif western alps peak metamorphic temperatures for the coesite pyrope bearing whiteschists from the dora maira massif western alps were determined with oxygen isotope thermometry the 18o smow values of the quartz after coesite 18o 8 1 to 8 6 n 6 phengite 6 2 to 6 4 n 3 kyanite 6 1 n 2 garnet 5 5 to 5 8 n 9 ellenbergerite 6 3 n 1 and rutile 3 3 to 3 6 n 3 reflect isotopic equilibrium temperature estimates based on quartz garnet rutile fractionation are 700 750 c minimum pressures are 31 32 kb based on the pressure sensitive reaction pyrope coesite kyanite enstatite in order to stabilize pyrope and coesite by the temperature sensitive dehydration reaction talc kyanite pyrope coesite h2o the a h2o must be reduced to 0 4 0 75 at 700 750 c the reduced a h2o cannot be due to dilution by co2 as pyrope is not stable at x co2 0 02 t 750 c p 30 kb in the absence of a more exotic fluid diluent e g ch4 or n2 a melt phase is required granite solidus temperatures are 680 c 30 kb at a h2o 1 0 and are calculated to be 70 c higher at a h2o 0 7 consistent with this hypothesis kyanite jadeite quartz bands may represent a relict melt phase peak p t f h2o estimates for the whiteschist are 34 2 kb 700 750 c and 0 4 0 75 the oxygen isotope fractionation between quartz 18o 11 6 and garnet 18o 8 7 in the surrounding orthognesiss is identical to that in the coesitebearing unit suggesting that the two units shared a common final metamorphic history hydrogen isotope measurements were made on primary talc and phengite d smow 27 to 32 on secondary talc and chlorite rite after pyrope d 39 to 44 and on the surrounding biotite d 64 and phengite d 44 gneiss all phases appear to be in nearequilibrium the very high d values for the primary hydrous phases is consistent with an initial oceanicderived connate fluid source the fluid source for the retrograde talc chlorite after pyrope may be fluids evolved locally during retrograde melt crystallization the similar d but dissimilar 18o values of the coesite bearing whiteschists and hosting orthogneiss suggest that the two were in hydrogen isotope equilibrium but not oxygen isotope equilibrium the unusual hydrogen and oxygen isotope compositions of the coesite bearing unit can be explained as the result of metasomatism from slab derived fluids at depth

sedimentation and basin formation related to ophiolite nappe emplacement miocene sw turkey abstract the miocene kasaba basin in southwestern turkey is a peripheral foreland basin that resulted from the thrusting and emplacement of the lycian nappes ophiolite unit onto a previously stable carbonate platform the resulting basin fill is the product of the complex interaction of tectonic and sedimentary processes and records the timing and magnitude of tectonic events in the thrust belt initial emplacement of the nappes in the late aquitanian resulted in the foundering and irregular subsidence of the carbonate platform by burdigalian times continued loading of the carbonate platform resulted in the development of a sedimentary basin ca 170 km across fan deltas shed off the leading edge of the nappe pile passed basin wards into a series of small submarine fans at the same time a peripheral bulge developed in the central part of the carbonate platform along the margin of the basin opposite the nappe pile a thick wedge of sediments derived from the carbonate platform was shed northwestwards into the basin varying sedimentation rates and migrating facies belts in the overlying middle and upper miocene basin fill sequence document both the progressive emplacement of the lycian nappes approximately 100 km from the northwest over the basin margin and overstep of the peripheral bulge

coesite and pure pyrope in high grade blueschists of the western alps a first record and some consequences a pyrope quartzite originally described by vialon 1966 from the dora maira massif was resampled and reinvestigated garnet up to 25 cm in size phengite kyanite talc and rutile are in textural equilibrium in an undeformed matrix of polygonal quartz the garnet is a pyrope almandine solid solution with 90 to 98 mol mg end member it contains inclusions of coesite which has partially inverted to quartz resulting in a typical radial cracking of the host garnet around the inclusions several lines of evidence show that coesite crystallised under nearly static pressure conditions and that the whole matrix has once been coesite

migration of fluid phases and genesis of basalt magmas in subduction zones dehydration and hydration reactions in both the downgoing lithosphere and the overlying mantle wedge have been examined in order to understand the role of h2o in the production of magmas at convergent plate boundaries the subduction of oceanic lithosphere occurring with increasing pressures and rising temperatures causes liberation of h2o from the slab amphibole which can be stable to the highest pt conditions among hydrous phases in the slab decomposes at around 90 km depth it follows that the subducted lithosphere is essentially anhydrous beneath volcanic arcs lying more than 110 km above the slab and that the supply of slab derived h2o is not a direct trigger for the production of arc magmas instead the h2o released from downgoing lithosphere reacts with the forearc mantle wedge to crystallize hydrous minerals serpentine talc amphibole chlorite and phlogopite this hydrated peridotite is dragged downward on the slab toward higher pt regions and releases h2o to shallower potential magma source regions in the mantle wedge combining experimental data on the stability of serpentine and talc with the thermal structure in the mantle wedge it is concluded that those minerals decompose beneath the forearc region on the other hand high pt experimental and thermodynamic data suggest that dehydration of amphibole and chlorite in the downdragged hydrated peridotite can take place just beneath a volcanic front phlogopite in the peridotite decomposes to release h2o at a deeper level about 200 km h2o liberated from the hydrated peridotite causes partial melting of overlying mantle wedge peridotites along with the migration of h2o through the above processes subduction components especially large ion lithophile elements can be overprinted on the magma source region which governs the geochemical characteristics of arc magmas

1d velocity structure beneath broadband seismic stations in the cretaceous gyeongsang basin of korea by receiver function analyses abstract the crustal velocity structures beneath four broadband seismic stations gkp gsu hdb and bus in the cretaceous gyeongsang basin southeastern korea are estimated by using receiver function analyses employing teleseismic waveforms the genetic algorithm is adopted to avoid the inherent non uniqueness problem of the inversion the inversion results are constrained by surface wave dispersions to complement the shortcoming of the receiver function the selected records of earthquakes distributed in three quadrants from each seismic station in the years from 2002 to 2005 are analyzed although limited quantity of data is used due to short operation periods the resolution and confidence level are expected to be better than those using less data the moho depth under gkp is estimated to be 30 km showing no distinctive indication of dipping this depth is well coincident with those in nearby velocity cross sections obtained from crustal scale seismic profiles compared to the 36 km deep moho previously reported by other independent work at gsu the moho appears at the 32 km depth and a distinct low velocity anomaly is detected at the depth of about 10 km they agree with those in the velocity tomogram of the nearby survey line an adakitic intrusion which results from the partial melting of a young and hot subducted oceanic crust in the basin during the cretaceous is suggested as a possible geologic interpretation of the low velocity zone the moho beneath hdb is 28 km deep and agrees with those in nearby velocity cross sections obtained from crustal scale seismic profiles this moho depth at hdb is rather shallower than those of other stations the significant p s phase amplitude and arrival time differences in the radial receiver functions conclude the moho to dip southwestwardly this is supported by polarities of direct p and p s in transverse receiver functions beneath bus p wave velocity increases gradually from the 32 km depth and it reaches 7 6 km s at the 36 km depth the moho discontinuity beneath bus is thought to be at an around 35 km depth

stability of anhydrous phase b experimental studies and implications for phase relations in subducting slab and the x discontinuity in the mantle 1 we have experimentally determined the equilibrium boundary of the reaction forsterite fo periclase per anhydrous phase b anh b at 900 1600 c and we used the retrieved gibbs free energy of formation of anh b to calculate the stability field of anh b stishovite sti with respect to the mg2sio4 polymorphs the results suggest the possibility of the reaction sequence wadsleytite anh b sti ringwoodite with increasing pressure at temperature below 600 c this might lead to an eye shaped splitting of the 410 km discontinuity within the interior of a sufficiently cold slab such as would prevail in a 140 myr old slab subducting at an angle of 60 with a rate of 14 cm yr e g tonga the equilibrium boundary of anh b sti with respect to the wadsleyite and ringwoodite has respectively positive and negative slope in the p t space the reaction of fo per to anh b seems to offer a viable explanation of the so called x discontinuity that has been observed at 275 345 km depth in several subcontinental and subduction zone environments it is suggested that periclase could form locally by the dissolution of silica in mantle fluid or precipitate from a hydrous melt that became enriched in mgo due to the incongruent melting of olivine at pressures of 6 8 gpa

decomposition of phase d in the lower mantle and the fate of dense hydrous silicates in subducting slabs abstracthigh pressure high temperature quench type experiments were carried out on serpentine to pressures of 53 gpa andtemperatures between 800 1800oc x ray analyses show that recovered phase assemblages varied considerably for thedifferent high pressure and high temperature studies the dense hydrous magnesium silicate phases decompose sequentiallyas the pressure increases and appear to serve as reservoirs for h 2 o in the mantle eventually releasing it at the highestpressure superhydrous phase b is stable up to pressure equivalent to the boundary between the transition zone and lowermantle phase d decomposes at pressures of 44 gpa equivalent to about 1250 km depth this may de ne the lower depthlimit for the presence of dense hydrous magnesium silicates beyond this pressure only nominally anhydrous phases havebeen recovered in high pressure experiments this may indicate a lack of stoichiometric hydrogen bearing silicate phasesat higher pressure 1998 elsevier science b v all rights reserved keywords x ray diffraction analysis lower mantle serpentine high pressure

earthquake supercycles inferred from sea level changes recorded in the corals of west sumatra records of relative sea level change extracted from corals of the mentawai islands sumatra imply that this 700 kilometer long section of the sunda megathrust has generated broadly similar sequences of great earthquakes about every two centuries for at least the past 700 years the moment magnitude 8 4 earthquake of september 2007 represents the first in a series of large partial failures of the mentawai section that will probably be completed within the next several decades

mylonitic ductile shear zones within tectonites and cumulates as evidence for an oceanic transform fault in the antalya ophiolite s w turkey summary in the coastal ophiolite belt of antalya especially in the massifs of adrasan and cirali tekirova tectonites and cumulates have preserved their primary structures tectonites display a first high temperature low deviatoric stress deformation s1 linked to the diapiric uplift of the asthenosphere below an east west orientated spreading centre a second mylonitic deformation produced under high deviatoric stress and lower temperature conditions produced shear zones of millimetric to kilometric scale throughout the tectonites and even in the cumulates their mean orientation n 150 e is near to perpendicular to the ridge axis and the associated lineation indicates horizontal essentially sinistral strike slip displacement this deformation must have taken place during the final crystallisation of the cumulates as indicated by its relationship to intrusive gabbroic dykelets representing residual liquids of the cumulates the s2 deformation is attributed to a transform fault situated sw of the coastal complexes later tectonic events include thrusting and wrench faulting again sinistral in a north south trending direction

petrology of the tekirova antalya ophiolite southern turkey evidence for diverse magma generations and their tectonic implications during neotethyan subduction the sw antalya complex is an assemblage of mesozoic carbonate platform margin and ophiolitic rocks which record the formation and tectonic emplacement of a small mesozoic ocean basin the late cretaceous ophiolitic rocks are located at two localities namely the relatively intact tekirova ophiolite to the east of kemer zone and the dismembered godene ophiolite to the west of kemer zone the tekirova antalya ophiolite comprises harzburgitic tectonites ultramafic to mafic cumulates isotropic gabbros and sheeted dikes numerous isolated dikes ranging in thickness from 5 cm to 10 m intruded the crustal rocks at different structural levels the isotropic gabbros are represented by gabbro diorite and quartz diorite rocks with granular to ophitic subophitic textures the isolated dikes are characterized by dolerite diabase and microdiorite with ophitic intersertal and microgranular textures these rocks exhibit tholeiitic to alkaline compositions new geochemical data presented in this paper from the isolated dikes and isotropic gabbros suggest that there are three main types of parental basic magmas that form the oceanic crustal rocks of the tekirova antalya ophiolite these are 1 iat series which can be referred to the group i isolated dikes and isotropic gabbros 2 low ti boninitic series characterized by the group ii isolated dike and isotropic gabbros and 3 oib type including the group iii isotropic gabbros the geochemical evidence suggests that the crustal rocks of the tekirova antalya ophiolite were generated from a progressive source depletion from island arc tholeiites iat to boninites therefore a fore arc tectonic setting seems likely for the generation of the crustal rocks from the tekirova antalya ophiolite in the southern branch of neotethys during the late cretaceous the oib type alkaline isotropic gabbros are thought to have resulted from either 1 a late stage magmatic activity fed by melts that originated within an asthenospheric window due to slab break off or 2 subduction of a ridge system which generated oib source across the asthenospheric window that has been no influence of fluids from the subducted slab into the overlying mantle wedge shortly before the emplacement of the tekirova antalya ophiolite onto the tauride platform

miocene remagnetisation of carbonate platform and antalya complex units within the isparta angle sw turkey abstract a palaeomagnetic study has been carried out within the mesozoic and tertiary units of the relatively autochthonous carbonate platforms and the allochthonous deep sea volcanics and sediments of the antalya complex exposed around the isparta angle sw turkey the antalya complex is interpreted as a mosaic of carbonate platforms basinal sediments volcanic and ophiolitic rocks which formed within a southerly strand of the neotethyan ocean adjacent to gondwana the results indicate a widespread remagnetisation event negative fold tests show that the remanence at most sites is of secondary origin e g within the cirali lavas the magnetisation is carried by magnetite of presumed authigenic origin the remagnetisation event is believed to have occurred in the early middle miocene burdigalian langhian it was possibly triggered by the migration of orogenic fluids ahead of the advancing lycian nappes during their emplacement onto the carbonate platforms subsequent to remagnetisation a large segment of the isparta angle underwent an anticlockwise rotation of 30 this rotation is attributed to the overall convergence and bending of the hellenic arc and the final stages of emplacement of the lycian nappes during the late miocene in agreement with previous studies previously southerly palaeolatitudes were inferred from late triassic extrusives of the godene zone calbali dag unit the post folding magnetisation identified here within the cirali lavas of the godene zone to the south implies that these low palaeolatitudes result from the inappropriate application of structural tilt corrections the available data cannot be used to substantiate an origin for the antalya units south of the equator in the early mesozoic instead a position close to the northern margin of gondwana is indicated

probabilistic seismic hazard analysis for sumatra indonesia and across the southern malaysian peninsula abstract the ground motion hazard for sumatra and the malaysian peninsula is calculated in a probabilistic framework using procedures developed for the us national seismic hazard maps we constructed regional earthquake source models and used standard published and modified attenuation equations to calculate peak ground acceleration at 2 and 10 probability of exceedance in 50 years for rock site conditions we developed or modified earthquake catalogs and declustered these catalogs to include only independent earthquakes the resulting catalogs were used to define four source zones that characterize earthquakes in four tectonic environments subduction zone interface earthquakes subduction zone deep intraslab earthquakes strike slip transform earthquakes and intraplate earthquakes the recurrence rates and sizes of historical earthquakes on known faults and across zones were also determined from this modified catalog in addition to the source zones our seismic source model considers two major faults that are known historically to generate large earthquakes the sumatran subduction zone and the sumatran transform fault several published studies were used to describe earthquakes along these faults during historical and pre historical time as well as to identify segmentation models of faults peak horizontal ground accelerations were calculated using ground motion prediction relations that were developed from seismic data obtained from the crustal interplate environment crustal intraplate environment along the subduction zone interface and from deep intraslab earthquakes most of these relations however have not been developed for large distances that are needed for calculating the hazard across the malaysian peninsula and none were developed for earthquake ground motions generated in an interplate tectonic environment that are propagated into an intraplate tectonic environment for the interplate and intraplate crustal earthquakes we have applied ground motion prediction relations that are consistent with california interplate and india intraplate strong motion data that we collected for distances beyond 200 km for the subduction zone equations we recognized that the published relationships at large distances were not consistent with global earthquake data that we collected and modified the relations to be compatible with the global subduction zone ground motions in this analysis we have used alternative source and attenuation models and weighted them to account for our uncertainty in which model is most appropriate for sumatra or for the malaysian peninsula the resulting peak horizontal ground accelerations for 2 probability of exceedance in 50 years range from over 100 g to about 10 g across sumatra and generally less than 20 g across most of the malaysian peninsula the ground motions at 10 probability of exceedance in 50 years are typically about 60 of the ground motions derived for a hazard level at 2 probability of exceedance in 50 years the largest contributors to hazard are from the sumatran faults

the september 2009 padang earthquake on 30 september 2009 the city of padang in indonesia was rocked by an earthquake with a moment magnitude of mw 7 6 despite its size the earthquake did not rupture the sunda megathrust and did not significantly relax the 200 years of accumulated stress on the mentawai segment the megathrust strain energy budget remains substantially unchanged and the threat of a great mw 8 5 tsunamigenic earthquake on the mentawai patch is unabated

direction of ophiolite emplacement inferred from cretaceous and tertiary sediments of an adjacent autochthon the bey daglari southwest turkey the late mesozoic to mid tertiary depositional history of an autochthonous block in southwest turkey is outlined in relation to the direction of emplacement of adjacent allochthonous units in this area a lively debate persists as to whether the antalya complex located along the mediterranean coast should be correlated with the lycian nappes sited to the northwest in central western anatolia both allochthonous bodies include mesozoic ophiolites and similar shallow to deep water sedimentary facies correlation of the antalya complex and the lycian nappes requires transport over the adjacent autochthon the bey daglari here field data from the southern part of the bey daglari are used to trace the depositional history of the autochthon from late cretaceous to late miocene time a pattern of late mesozoic pelagic carbonate deposition giving way to more heterogeneous sedimentation in the early tertiary is documented by early miocene the autochthon was blanketed by a thick sequence of miocene elastics mostly derived from an ophiolite evidence from sedimentary structures shows that transport was from the east and northeast depositional models are advanced which involve an early miocene delta submarine fan giving way in later miocene times to an alluvial fan demonstration that in this area the ophiolite material was derived from the east provides additional important evidence of the existence of a southerly mesozoic oceanic basin distinct in origin from the lycian nappes to the north

processes of clastic sedimentation associated with late cretaceous ophiolite emplacement in the sw segment of the antalya complex s turkey abstract clastic sediments provide important clues to the timing and processes of ophiolite emplacement when integrated into the regional temporal and tectonic framework four related settings of late cretaceous ophiolite related clastic sediment deposition are exposed in the sw segment of the antalya complex along the western limb of the isparta angle an orocline in sw turkey the restored pre emplacement paleogeography is indicative of a regional scale mesozoic carbonate platform bordered to the east by a late triassic volcanic rift that partially infilled with deep sea sediments passing eastwards into several mesozoic carbonate platforms floored by pre rift or syn rift crust and finally into the south neotethys first emplacement related sediments unconformably overlie exhumed ultramafic and gabbroic ophiolitic rocks and comprise locally variable mass flow deposits up to several hundred m thick that are dominated by subaqueous screes and debris flow deposits fossil evidence benthic and planktic foraminifera radiolarians and macrofossils indicates accumulation during the campanian maastrichtian much of the coarse talus was derived from weathering and erosion of intrusive ophiolitic rocks sheeted dykes gabbro petrographic xrd and whole rock geochemical analysis of sandstones and igneous clasts indicate additional derivation from basaltic rocks interpreted as the eroded extrusive layer of the ophiolite additional material was derived from late triassic cretaceous deep water volcanics and sediments and also from late cretaceous and older platform carbonates the coarse clastics relate to ophiolite emplacement onto the continental margin rather than forming in an oceanic setting e g rifted ridge or oceanic fracture zone the emplacement was associated with crustal extension that exposed ultramafic and gabbroic rocks on the seafloor where they were covered by clastic debris secondly late cretaceous calciturbidites and debris flow deposits depositionally overlie late triassic late cretaceous deep water passive margin sediments the clastic debris was derived from the emplacing ophiolite and from an adjacent mesozoic carbonate platform thirdly calciturbidites and debris flow deposits also depositionally overlie the same carbonate platform fourthly west of the same carbonate platform ophiolite derived mass flow breccias accumulated locally and were then interleaved with previously emplaced ophiolitic plutonic rocks mainly serpentinite and gabbro typically at high angles the four depositional settings relate to ongoing stages of late cretaceous ophiolite emplacement in a setting dominated by regional scale thrusting and strike slip i e transpression the latest cretaceous deformation and related clastic deposition affected part of the northern active continental margin of the southern neotethys but without reaching more inboard continental crust regional tauride platform a situation that contrasts with more orthogonally emplaced ophiolites

crustal and upper mantle structure of the southeastern tibetan plateau from joint analysis of surface wave dispersion and receiver functions abstract researches on the southeastern tibetan plateau provide important insights into the tectonic evolution of the tibetan plateau in this study we have constructed a high resolution 3d shear wave velocity model through joint inversion of receiver functions and surface wave dispersion data the crustal thickness and poisson s ratio models are first determined by h k stacking of receiver functions the crustal thickness changes from 30 km in the south to 62 km in the north presenting strong lateral variations the fundamental mode of rayleigh wave dispersion data spanning periods from 8 to 65 s were then jointly used to constraint the absolute shear wave velocity the shear wave velocity structure shows lateral variations there are low velocity zones distributed in the crust and upper mantle two continuously distributed low velocity zones are clearly presented in the middle to lower crust which extend from north toward southeast and southwest respectively joining together in southern yunnan in this study we deduced the migration model of soft materials in middle to lower crust in southeastern tibetan plateau which explains that the resistance from sichuan basin separates the flowing materials from tibetan plateau into southeast and northwest branches they flow along the west margin of sichuan basin and then extrude out from northeastern and southeastern tibetan plateau respectively the southeast branch is blocked and cannot flow in the entire crust it is limited in a certain range of depths and channels the two low velocity zones in this study possibly present two flow channels of the middle to lower crustal materials extruded from the tibetan plateau

a longitudinal carbonate fan from the jurassic of the oman mountains the guweyza limestone formation of the hamrat ad duru abstract when sedimentological stratigraphical and structural data are considered the continental rise sediments of oman neo tethys the hamrat duru group can be restored to their original basin configuration prior to their southwest directed emplacement with the semail ophiolite onto the oman continental margin during the late cretaceous the hamrat duru group sediments are preserved in well exposed imbricate fans the largest of which forms the hamrat ad duru range in the south central oman mountains in the south central hamrat ad duru middle and upper jurassic ooid rich carbonate sediment was transported from the adjacent oman carbonate platform during periods of tectonic instability into the oman neo tethys hawasina basin by high and low density turbidity currents to form sediment sheets with a margin parallel axis of deposition palaeocurrents are northwest directed parallel to the oman margin along the southwest of the hamrat ad duru and northeast directed away from the margin in structurally higher more distal imbricates of the northeastern hamrat ad duru this implies sediment input at the southern end of the hamrat ad duru these trends are reflected in the distribution of sedimentary facies with most proximal facies developed in the southern hamrat ad duru passing into progressively more distal facies to the northwest and northeast sediment thinning and fining is more accentuated away from the margin towards the northeast and sedimentation was concentrated parallel to the oman margin the hamrat ad duru represents a longitudinal fan that was at least 120 km long and extended at least 60 km away from the margin

godene zone antalya complex volcanism and sedimentation along a mesozoic continental margin s w turkey the godene zone antalya complex is an assemblage of ophiolitic and associated sedimentary rocks formed on a passive margin during and after the rifting of a mesozoic ocean basin the zone comprises late triassic alkaline mafic submarine lavas and sediments mostly pelagic which are tectonically intercalated with mafic ultramafic plutonic rocks taken to be remnants of an original ophiolitic substratum the godene zone also includes major limestone massifs and tectonised remnants of former carbonate margin facies early triassic rifting initiated a horst graben terrain with localised evaporite and clastic deposition by late triassic time continued extension allowed substantial extrusion of submarine mafic volcanics these were often erupted close to tectonically active fault scarps generating both epiclastic and pyroclastic volcanic breccias several large slivers of continental basement were rifted off to form major offshore massifs which remained as topographic highs throughout the mesozoic during late triassic time exposed parts of the continent bey daglari and the offshore massifs shed siliciclastics mostly turbidites above the mafic lavas offshore reefs also shed material ranging from substantial detached blocks to finer grainedhalobia limestone facies during jurassic to late cretaceous time the whole area underwent passive margin deposition radiolarian pelagic sediments were deposited in deep water above the ophiolitic basement and around the offshore massifs the reef complexes persisted until mid cretaceous time when calcareous pelagic deposition was initiated passive margin conditions were terminated with deposition of ophiolitic clastics and olistostrome melange in the maastrichtian followed by major tectonism

moho map of south america from receiver functions and surface waves 1 we estimate crustal structure and thickness of south america north of roughly 40 s to this end we analyzed receiver functions from 20 relatively new temporary broadband seismic stations deployed across eastern brazil in the analysis we include teleseismic and some regional events particularly for stations that recorded few suitable earthquakes we first estimate crustal thickness and average poisson s ratio using two different stacking methods we then combine the new crustal constraints with results from previous receiver function studies to interpolate the crustal thickness between the station locations we jointly invert these moho point constraints rayleigh wave group velocities and regional s and rayleigh waveforms for a continuous map of moho depth the new tomographic moho map suggests that moho depth and moho relief vary slightly with age within the precambrian crust whether or not a positive correlation between crustal thickness and geologic age is derived from the pre interpolation point constraints depends strongly on the selected subset of receiver functions this implies that using only pre interpolation point constraints receiver functions inadequately samples the spatial variation in geologic age the new moho map also reveals an anomalously deep moho beneath the oldest core of the amazonian craton

crustal modifications beneath the central sunda plate associated with the indo australian subduction and the evolution of the south china sea abstract to decipher possible crustal modifications associated with complex tectonics in se asia we have conducted a systematic receiver function investigation beneath the central sunda plate mainly including borneo the malay peninsula sumatra and part of the south china sea scs well determined observations from a total of 22 stations reveal a laterally heterogeneous crust with thickness ranging from 22 8 km to 39 1 km and vp vs values varying from 1 68 to 2 12 an increasing pattern of vp vs ratios towards the sumatra fault and the toba caldera indicates significant modifications of crustal composition possibly due to melting from the indo australian subduction crustal compositions beneath the malay peninsula are determined to be mostly felsic to intermediate rocks crustal thinning at the sibumasu terrane relative to the east malay block is revealed and may be attributed to joint effects of late paleogene rifting and a subsequent thermal anomaly the southwards subduction of the hypothetical proto scs may have contributed to the revealed magma intrusion and thinned crust beneath nw borneo and developed an accretionary setting at ne borneo the cessation of the proto scs subduction further promotes collision between ne borneo and nansha block which is supported by the observed crustal thickening thinned crust at the southern margin of the scs basin is further confirmed as continental in origin and has been altered by possible post spreading volcanisms

bilelyeri group antalya complex deposition on a mesozoic passive continental margin south west turkey the bilelyeri group comprises complexly deformed mesozoic sedimentary rocks of continental margin affinities kumluca zone these are structurally intercalated between a coeval carbonate platform to the west bey daglari zone and late triassic ophiolitic rocks and sediments interpreted as emplaced marginal oceanic crust to the east godene zone four formations erected in the bilelyeri group record the later stages of continental rifting and the progressive development of part of a mesozoic passive continental margin the two late triassic formations the telektas tepe and the hatipalani formations are dominated by terrigenous clastic and calcareous clastic sediments including large detached blocks of reef limestone these rocks were laid down by mostly mass flow and turbidity flow into steep sided rift depressions organic reefs were constructed in bordering shallow seas while terrigenous clastic sediment was shed from exposed basement horsts thick sequences of mafic lavas were extruded norian in axial parts of the rift zones followed by a regional change to deposition of pelagic halobia bearing limestone this culminated in a major hiatus involving large scale sliding of shallow water limestones into deeper water the jurassic to early cretaceous derekoy formation mostly consists of siltstones radiolarian cherts and mudstones intercalated with redeposited limestones and black shales during this time parts of the margin were bordered by major offshore carbonate complexes constructed partly on basement fragments previously rifted off the parent continental areas black shales and reduced hemipelagic sediments were deposited in an elongate trough between the main platform and an offshore complex to the east some degree of margin reactivation in the early cretaceous is indicated by renewed deposition of turbiditic sandstone and chloritic clays in some distal sequences strong relative enrichment of manganese in some horizons is attributed to offshore volcanic exhalations subsequent regional subsidence in the mid to late cretaceous is suggested by a switch to predominantly calcareous pelagic sedimentation on the adjacent platform and the offshore massifs as well as on the bilelyeri margin tectonic disruption of the platform edge during the late cretaceous is implied by major redeposition of shallow water shelf limestones in proximal bilelyeri sequences the bilelyeri margin and the adjacent godene zone were tectonically deformed in latest cretaceous to early tertiary time and were thrust over the adjacent bey daglari platform in the early miocene viewed in an east mediterranean perspective the bilelyeri sequences were part of a locally north south trending segment of a regionally east west margin to a substantial oceanic area further south this segment apparently suffered significant strike slip deformation both during its construction and its later emplacement instructive comparisons can be made with other areas of the east mediterranean especially south west cyprus

wrench and thrust tectonics along a mesozoic cenozoic continental margin antalya complex sw turkey the segment of the antalya complex w of antalya bay displays the results of latest cretaceous to miocene deformation on a previously passive mesozoic continental margin the 300 km 2 area detailed here includes parts of from w to e a mesozoic carbonate platform its bordering sediment margin and the adjacent marginal oceanic crust with sediment cover the platform is folded on n s axes and has been overthrust westward by its sediment margin this thin sediment sequence has been detached from its basement in a spectacular w verging imbricate thrust belt similar though less organized westward thrusting occurs in the thin sediment cover to the marginal oceanic crust and may also affect the igneous basement itself however this part of the margin is dominated by an array of anastomosing subvertical screens of serpentinite up to several kilometres wide these are thought to be cool upward protrusions of the hydrated ultramafic substratum to the marginal crust into a then active braided strike slip fault system the fault strands now divide the intact marginal rocks into large lozenges some of which have oblique and sigmoidal structures and steeply plunging folds the thrust and wrench tectonics may have operated in concert in a regionally transpressive regime or thrusting may have accompanied only the initiation of wrench tectonics the local interplay of transpression and transtension was partly responsible for the present complexity of the area even more important was the original mechanical inhomogeneity of the margin particularly the inclusion of rifted off continental fragments in the marginal ocean crust and the strong basement cover contrasts on the margin

experimental and theoretical studies of the stabilities of talc antigorite and phase a at high pressures with applications to subduction processes we have experimentally determined the equilibrium talc enstatite quartz coesite h2o to 40 kbar in the system mgosio2h2o msh using both synthetic and nearly pure mg end member natural talc and other synthetic starting materials for the other solid phases at 40 kbar the equilibrium dehydration boundary lies 150 c higher than that calculated using data from the existing internally consistent thermochemical data bases the reason for this discrepancy lies in the erroneous compressibility data of talc in the data bases we have retrieved the compressibility of talc from the experimental phase equilibrium data and have also calculated sereral other equilibria in the msh system involving talc antigorite and the dense hydrous magnesium silicate dhms commonly referred to as phase a comparison of these equilibria with selected thermal profiles at the leading edge of young and old subducting oceanic slabs along with the dehydration condition of basaltic amphibole and solidus of mantle peridotite provides an explanation for the observed heights of the volcanic fronts above subducting oceanic lithosphere further it is found that in cold oceanic slabs 50 ma with subduction velocity of 10 cm y antigorite will transform to the dhms phase a through a vapor conserved reaction at a depth of 200 km phase a will then serve as a carrier of water into the deeper mantle

is phase a relevant to the earth s mantle abstract dense hydrous magnesium silicates dhms such as phase a mg 7 si 2 o 8 oh 6 are potential hosts for water in the earth s mantle previous work has delineated the stability field of phase a pha coexisting with clinoenstatite cen and forsterite fo in the system mgo sio 2 h 2 o msh in this study the effects of the presence of magnesite mc diopside di and pyrope py on the stability of coexisting pha cen fo have been determined in msh the breakdown reaction pha cen fo h 2 o was bracketed between 720 and 740 c at 7 gpa between 800 and 820 c at 8 gpa and between 860 and 880 c at 9 gpa at 10 gpa pha cen transforms to a clinohumite ch bearing assemblage between 920 and 940 c which in turn dehydrates between 940 and 960 c to fo v at higher pressures pha becomes unstable relative to phase e another dhms kanzaki 1991 addition of carbonate to msh changes the breakdown reaction to pha cen mc fo v where v is an h 2 o co 2 fluid at 8 gpa this reaction occurs between 800 and 850 c indistinguishable from the position of the co 2 free reaction in msh in the presence of diopside in the cao mgo sio 2 h 2 o system the reaction pha en ss fo di ss h 2 o occurs between 700 and 730 c at 8 gpa where en ss and di ss are ca poor and ca rich pyroxene solid solutions respectively in the pyrope containing assemblage in the mgo al 2 o 3 sio 2 h 2 o system the pha bearing assemblage reacts to form ch between 740 and 760 c at 8 gpa the ch bearing assemblage dehydrates to fo py v between 800 and 830 c at 8 gpa in the system mgo feo sio 2 h 2 o with molar mg mg fe 0 90 the reaction pha cen ss ch v occurs at ss ch fo v reaction occurs between 850 and 900 c in no case did the presence of additional components such as cao feo al 2 o 3 or co 2 or the additional phases diopside magnesite or pyrope stabilize the hydrous phases pha or ch to significantly higher temperatures therefore pha will not be a stable phase in lherzolite assemblages under normal geothermal gradients in the mantle in the interior of subducting slabs temperatures may be sufficiently low that assemblages containing pha may be stable to pressures greater than 10 gpa allowing pha to transport h 2 o to the deeper mantle it is more likely that the higher pressure phase e will be stabilized instead

characteristics of residual soils in singapore as formed by weathering residual soils are weathering products of rocks that are commonly found under unsaturated conditions the properties of residual soils are a function of the degree of weathering a series of index properties engineering properties mercury porosimetry tests and scanning electron microscope sem examinations were performed on residual soils from two major geological formations in singapore the results indicate that the variation in the index and engineering properties as well as microstructural characteristics of the residual soils with depth can be related to the degree of weathering an increase in the degree of weathering results in an increase in pore volume and produces a larger range of pore size distribution the variation in the pore volume and the pore size distribution through a profile of weathered rock can be used as an indicative measure of the variation in the degree of weathering with depth

melting and seismic structure beneath the northeast japan arc transportation of h2o associated with subduction of the pacific plate beneath the northeast japan arc is modeled to predict distribution of aqueous solution and melt and the consequent p wave velocity structure the observed velocity structure coincides well with the model for equilibrium transport of h2o most of h2o subducted is brought down to 150 200 km depth along the slab then the aqueous fluid generated ascends to initiate melting which explains the low velocity regions 6 reduction observed beneath the backarc rather than beneath the volcanic front if equilibrium transport of h2o occurs initiation of melting beneath the backarc with deep subduction of h2o is likely to be the case also for other subduction zones with slabs older than several tens of m y cold enough to stabilize serpentine to a great depth

dehydration kinetics of talc and 10 a phase consequences for subduction zone seismicity abstract the process of dehydration embrittlement is usually proposed as an explanation for the presence of intermediate depth earthquakes in subduction zones it assumes that the release of water by hydrous mineral breakdown is fast enough to provoke brittle failure we performed high pressure high temperature dehydration experiments of talc and 10 a phase coupled with in situ measurement of reaction kinetics using synchrotron x ray diffraction newly developed x ray transparent pressure sealed titanium capsule ensured a closed thermochemical environment from isothermal kinetics data fitted to the avrami s equation and from the texture of reaction products we conclude that dehydration rates of these minerals are limited by diffusion predicted minimum rates of fluid release range from 10 4 to 9 10 6 m 3 fluid m 3 rock s 1 and are fast enough to provoke hydraulic rupture since maxwell relaxation rate of rocks relevant of subduction zones are slower than the rate of fluid release these rates are comparable between talc 10 a phase and antigorite also perrillat j p daniel i koga k t reynard b cardon h crichton w a 2005 kinetics of antigorite dehydration a real time x ray diffraction study earth planet sci lett 236 899 913 consequently we suggest that the dehydration of hydrous minerals may eventually be fast enough to trigger the intermediate depth earthquakes and that the deepest among intermediate depth earthquakes may actually locate the limits for dehydration of hydrous minerals in the downgoing lithosphere

the bentong raub suture zone abstract it is proposed that the bentong raub suture zone represents a segment of the main devonian to middle triassic palaeo tethys ocean and forms the boundary between the gondwana derived sibumasu and indochina terranes palaeo tethyan oceanic ribbon bedded cherts preserved in the suture zone range in age from middle devonian to middle permian and melange includes chert and limestone clasts that range in age from lower carboniferous to lower permian this indicates that the palaeo tethys opened in the devonian when indochina and other chinese blocks separated from gondwana and closed in the late triassic peninsular malaysia segment the suture zone is the result of northwards subduction of the palaeo tethys ocean beneath indochina in the late palaeozoic and the triassic collision of the sibumasu terrane with and the underthrusting of indochina tectonostratigraphic palaeobiogeographic and palaeomagnetic data indicate that the sibumasu terrane separated from gondwana in the late sakmarian and then drifted rapidly northwards during the permian triassic during the permian subduction phase the east malaya volcano plutonic arc with i type granitoids and intermediate to acidic volcanism was developed on the margin of indochina the main structural discontinuity in peninsular malaysia occurs between palaeozoic and triassic rocks and orogenic deformation appears to have been initiated in the upper permian to lower triassic when sibumasu began to collide with indochina during the early to middle triassic a type subduction and crustal thickening generated the main range syn to post orogenic granites which were emplaced in the late triassic early jurassic a foredeep basin developed on the depressed margin of sibumasu in front of the uplifted accretionary complex in which the semanggol formation rocks accumulated the suture zone is covered by a latest triassic jurassic and cretaceous mainly continental red bed overlap sequence

structure and sequence of thrusting in deep water sediments during ophiolite emplacement in the south central oman mountains abstract sedimentological and stratigraphical investigations of the deep water passive margin sediments of the oman neo tethys the hawasina ocean when allied with structural relationships between duplexes of these units emplaced on to the oman margin during late cretaceous ophiolite obduction allow the reconstruction of sediment distribution in the hawasina ocean from this starting point and the observed stacking order of duplexes the sequence of thrusting of the oceanic sediments can be deduced imbrication proceeded through foreland propagating thrusts whilst the assembled thrust stack was modified at a late stage of emplacement by out of sequence thrusting related to sequential locking of thrust planes towards the hinterland and gravity sliding off the flanks of a major anticline that developed in the underlying autochthonous shelf and basement two main factors governed duplex and imbricate fan formation and distribution firstly two contrasting sedimentary basins were present along the central oman margin the duru basin distal to the al ayn basin secondly competent sedimentary successions were bulldozed ahead of the semail ophiolite whilst less competent shale and chert units were overridden by the ophiolite or imbricated along its leading edge

accretionary processes at subduction zones in the eastern mediterranean abstract the tectonic history of the eastern mediterranean as well as the present tectonic style are affected by the collision and accretion of oceanic plateaus at subduction zones small but distinct oceanic plateaus exist today in the eastern mediterranean away from the plate boundary many other oceanic plateaus crowd the plate boundary particularly in the hellenic arc area their presence results in the unusual complexity of this subduction zone as is evidenced by the seismicity and bathymetry patterns the present two arcs system in this region the hellenic and cyprean arcs is probably the consequence of the collision of a large continental plateau with an older arc this plateau has been thrusted over the continental mass of anatolia and pieces of it are to be found in the region between the two arcs active subduction in the hellenic arc takes place in the outer trenches particularly in the ionian and strabo trenches subduction of mediterranean lithosphere in the pliny and ptolemy trenches is limited to their western parts inner segments of these trenches served as the main subduction trenches before the subduction zones migrated outward following the collision of oceanic plateaus

partial melting of subducting oceanic crust the conditions under which partial melting of subducting oceanic crust occurs can be determined by combining a partial melting model for basaltic compositions with two dimensional thermal models of subduction zones for porosities of 1 containing h20 the amount of partial melt generated at the wet basaltic solidus is limited to 100 mpa can be maintained by rocks close to or above their melting temperatures in the absence of high shear stresses substantial melting of the oceanic crust will only occur during subduction of very young 5 ma oceanic lithosphere partial melting of hydrated basalt amphibolites derived from the mid ocean ridge has been proposed e g 1 3 as being responsible for the generation of certain recent high al andesitic to dacitic volcanic rocks adakites three of these volcanic suites mount st helens southern chile and panama occur in volcanic arcs where oceanic crust 25 ma is being subducted at rates of 1 3 cm yr and the calculated thermal regime is several hundreds of degrees hotter than more typical subduction zone environments however oceanic lithosphere is not currently being subducted beneath baja and new guinea where recent adakites are also present suggesting that some adakite magmas may form by water undersaturated partial melting of underplated mafic lower crust or previously subducted oceanic crust further experimental work on compositions representative of oceanic crust is required to define the depth of possible adakite source regions more accurately

hamrat duru group revised stratigraphy of a mesozoic deep water passive margin in the oman mountains the stratigraphy of the hawasina complex is redefined and rationalized to conform with standard stratigraphical nomenclature previously proposed tectono stratigraphical units are abandoned in favour of a system that relies on the lateral correlation of lithofacies between structural units to this end the dibba dhera wahrah and al ayn formations are incorporated into an expanded hamrat duru group this group is divided into five formations the zulla guweyza sandstone guweyza limestone sid r and nayid and spans triassic to mid cretaceous cenomanian time it locally passes up into the syn orogenic sediments of the riyamah member of the muti formation the nomenclature of the deeper water chert dominated formations is left unaltered

testing of permian lower triassic stratigraphic data in a half graben tilt block system evidence for the initial rifting phase in antalya nappes testing of middle permian lower triassic stratigraphic data from the antalya nappes in a half graben tilt block system has revealed the presence of episodic rifting events separated by periods of

new evidence and interpretation of facies provenance and geochemistry of late triassic early cretaceous tethyan deep water passive margin related sedimentary rocks ayios photios group sw cyprus in the context of eastern mediterranean geodynamics abstract the late triassic early cretaceous deep sea sedimentary succession exposed in western cyprus is used here to help understand the wider context of continental break up and seafloor spreading in the easternmost mediterranean region the restored sequence begins with late triassic base of slope sandstone turbidites and mudrocks and fines upwards into mudrocks distal calciturbidites and metalliferous sediments after a hiatus late jurassic early cretaceous non calcareous mudstones and radiolarites accumulated beneath the carbonate compensation depth together with redeposited shallow water derived carbonates including calcirudites the succession culminates in late jurassic early cretaceous very thickly bedded and highly mature quartzarenites that accumulated by mass flow processes the fine grained siliciclastic sediments are terrigenous in origin as indicated by whole rock trace element and ree analysis fe mn and trace metal enrichment in the late triassic represents hydrothermal input related to submarine volcanism that was probably triggered by the nearby onset of seafloor spreading the late triassic sandstones were derived from a low to intermediate grade metamorphic source terrane the late jurassic early cretaceous sandstones reflect extreme physical and chemical maturity in the source area followed by transport and mass flow to a deep water base of slope setting regional facies variation and locally available palaeocurrent data suggest sediment supply originally from a continental block no more than tens of km to the west or north similar successions are exposed in w turkey represented by the antalya complex in the light of alternatives the sedimentary succession is restored as the base of slope apron of a rifted microcontinental block adjacent to the northern margin of the s neotethys the overall succession indicates unstable passive margin development after regional latest triassic early jurassic continental break up with implications for plate reconstructions and hydrocarbon exploration

receiver function structure beneath four seismic stations in the sumatra region abstract we estimated the velocity structure beneath four three component broad band seismic stations in the sumatra region by the joint inversion of teleseismic receiver functions and surface wave group velocities the stations part of geofon network ge are located in diverse geologic settings including backarc basins forearc basins and the forearc ridge the stations are distributed roughly trench parallel providing samples of conditions along the length of sumatra 143 receiver functions were computed by employing an iterative time domain deconvolution in order to minimize acausal noise the teleseismic observations at each station were grouped by back azimuth and ray parameter and then stacked to increase the signal to noise ratios surface wave group velocity dispersion was measured for paths across the sunda block from events to the northeast of the stations p wave velocity profiles were derived by inverting the stacks and group velocity data using a linearized time domain inversion scheme with an interpolated crust2 0 global model for input the results differ significantly from crust2 0 and reflect the diversity of geologic environments within which the stations are located crustal thicknesses beneath the stations range from 16 0 km at the forearc to 30 0 km at a backarc basin these results add to the available velocity and crustal thickness data for the sumatra region

receiver structure beneath the southern mojave block california an inversion of a receiver function recorded at lawrence livermore national laboratory nevada test site network station lac reveals a range of 1 d velocity structures that are consistent the observed waveform the shear velocity structure southeast of lac is relatively simple consisting of an approximately 30 to 34 km thick crust all models contain relatively sharp crust mantle boundaries with a change in velocity from about 3 5 km sec to approximately 4 6 km sec over a depth range of 4 to 6 kilometers the range of models can be roughly divided into two groups that differ mostly in the mid to lower crust the first model of the earth structure contains a large low velocity zone in the middle and lower crust shear wave velocities as low as 2 8 km sec the second model contains nearly constant velocities approximately 3 5 km sec through the middle to lower crust in contrast with the simplicity of the southeast receiver function the receiver functions corresponding to the northwest and southwest show the influence of lateral velocity heterogeneity and can at best be discussed qualitatively

end member modelling as an aid to diagnose remagnetization a brief review remagnetization of a palaeomagnetic signal is difficult to recognize independently of directional information the situation becomes more complex when remagnetized rocks pass palaeomagnetic field tests for example when the remagnetization of a rock sequence has occurred before folding it is evident that palaeogeographic reconstructions are seriously flawed when actu ally remagnetized rocks are not identified as such here we discuss the merits and pitfalls of so called end member modelling of acquisition curves of the isothermal remanent magnetization irm to recognize remagnetized strata the technique requires no a priori information about the irm acquisition curves the algorithm unmixes a set of irm acquisition curves into a number of invariant curves termed end members and calculates the mixing proportions of the end members for each sample since primary natural remanent magnetization nrm and remag netized nrm are acquired by different processes their signatures can be recognized from subtle differences in the magnetic properties we illustrate the potential of the approach by three case studies one from spain and two from turkey in which the magnetic properties of remagnetized and non remagnetized rocks are evaluated the natural remanent magnetization nrm of a rock is described asremagnetized when itrepresents apalaeomagnetically younger age thanthe sediment age of the rock formation under study remagneti zation interferes with palaeogeographic reconstruc tions asisincreasinglybeingappreciated the late palaeozoic remagnetization event was firmly rec ognized in the appalachians in the usa in the early 1980s e g mccabe et al 1983 see the review of van der voo torsvik 2012 while the implica tionsoflatepalaeozoicremagnetizationineuropean

tectonic reconstruction of cyprus reveals late miocene continental collision of africa and anatolia abstract the extended northern continental margin of africa is currently colliding with and under thrusting northward below cyprus the age of onset of this collision is poorly constrained but is critical if we are to quantify continental subduction and evaluate its role during spectacular recent uplift of southern turkey from 7 ma to the present here we reevaluate the evolution of northern cyprus and document the modern structure of the kyrenia fold thrust belt in a balanced cross section for the first time to determine the timing and amount of shortening the belt deformed an upper cretaceous to miocene stratigraphy which was deposited onto a metamorphic basement the fold thrust belt was previously proposed to have formed during two stages in eocene and late miocene time based on stratigraphic and limited structural evidence we revaluate evidence for an eocene phase of thrusting in kyrenia and find that 1 repetitions of eocene and older rocks are explained by miocene thrusting and newly documented olistoliths were misinterpreted as pre miocene thrust slices 2 uplift in eocene time was not isolated to kyrenia but also affected northern arabia and results from regional dynamic topography or forebulge formation based on kinematic constraints from a plate reconstruction we interpret that metamorphic rocks in kyrenia were metamorphosed by cretaceous burial below the troodos ophiolite and were subsequently exhumed by upper plate extension during latest cretaceous obduction onto the african margin the latest cretaceous miocene plate boundary between africa and the taurides was located to the north of kyrenia the kyrenia fold thrust belt accommodated a minimum of 17 5 km of shortening as a result of 9 6 ma thrusting as a result of initial africa taurides collision the northern edge of african continental crust arrived below the taurides where it has been seismologically imaged in late pleistocene time and may have caused or contributed to recently recognised major tauride uplift since 0 5 ma

temperatures heat flux and frictional stress near major thrust faults we examine the two dimensional advective and conductive transport of heat in a region of thrust faulting both simple theoretical considerations and numerical experiments show that the steady state temperatures near the fault are reduced by a divisor s 1 b z vsin below what they would be with the same heat sources but in the absence of advection in this expression z is the depth to the fault v is the slip rate is the component of the dip of the fault in the direction of underthrusting is thermal diffusivity and b is a dimensionless factor that is essentially equal to one for most forms of heating initial changes in temperatures near the fault are given by t z t t z 0 12vsin t z 0 z these simple formulae are successful because of the neglible influence of lateral conduction of heat at least for slip rates of a few mm yr or more two time constants govern the transition from the initial change in temperature to steady state t1 u v where u is the distance along the fault in the direction of underthrusting from the surface to the depth in question and t2 z 2 2 where z is the depth to the fault when elapsed times exceed the sum of these two time constants temperatures differ from their steady state values by only about 10 percent the numerical experiments indicate that the simple formulae are sufficiently accurate that sophisticiated numerical modeling of temperatures in specific regions is unwarranted putain an application of these simple formulae to measurements of conductive heat flow at island arcs implies that shear stresses at island arcs approach 100 mpa and are greater than 30 mpa calculations of temperatures appropriate for the himalaya suggest that shear stresses of 100 mpa on the main central thrust probably are required to account for the tertiary granites of the region if melting took place after slip began on the thrust similarly the cut off in seismicity at a depth of about 15 km in the himalaya if due to temperatures exceeding 350 to 450 c implies a deviatoric stress close to 100 mpa

pervasive palaeogene remagnetization of the central taurides fold and thrust belt southern turkey and implications for rotations in the isparta angle the turkish anatolide tauride block rifted away from the northern margin of gondwana in the triassic which gave way to the opening of the southern neo tethys by the late palaeocene to eocene it collided with the southern eurasian margin leading to the closure of the northern neo tethys ocean to determine the position of the anatolide tauride block with respect to the african and eurasian margin we carried out a palaeomagnetic study in the central taurides belt which constitutes the eastern limb of the isparta angle the sampled sections comprise carboniferous to palaeocene rocks mainly limestones our data suggest that all sampled rocks are remagnetized during the late palaeocene to eocene phase of folding and thrusting event related to the collision of the anatolide tauride block with eurasia to further test the possibility of remagnetization we use a novel end member modelling approach on 174 acquired isothermal remanent magnetization irm curves we argue that the preferred three end member model confirms the proposed remagnetization of the rocks comparing our data to the post eocene declination pattern in the central tauride belt we conclude that our clockwise rotations are in agreement with data from other studies after combining our results with previously published data from the isparta angle that includes our study area we have reasons to cast doubt on the spatial and temporal extent of an earlier reported early to middle miocene remagnetization event we argue that the earlier reported remagnetized directions from triassic rocks in tilt corrected coordinates from the southwestern antalya nappes western taurides are in good agreement with other studies from the area that show a primary origin of their characteristic remanent magnetization this implies that we document a clockwise rotation for the southwestern antalya nappes since the triassic that is remarkably similar to the post eocene 40 rotation of the central taurides for the previously published results that are clearly remagnetized we argue that their remagnetization has occurred in the palaeocene to eocene

analysis of the crustal velocity structure of the british isles using teleseismic receiver functions summary the onshore crustal and upper mantle velocity structure of the british isles has been investigated by teleseismic receiver function analysis the results of the study augment the dense offshore and sparse onshore models of the velocity structure beneath the area in total almost 1500 receiver functions have been analysed which have been calculated using teleseismic data from 34 broadband and short period three component seismic recording instruments the crustal structure has primarily been investigated using 1 d grid search and forward modelling techniques returning crustal thicknesses bulk crustal vp vs ratio and velocity depth models h stacking reveals crustal thicknesses between 25 and 36 km and vp vs ratios between 1 6 and 1 9 the crustal thicknesses correlate with the results of previous seismic reflection and refraction profiles to within 2 km the significant exceptions are the stations close to the iapetus suture where the receiver function crustal thicknesses are up to 5 km less than the seismic refraction moho this mismatch could be linked to the presence of underplated magmatic material at the base of the crust 1 d forward modelling has revealed subcrustal structures in northern scotland these correlate with results from other uk receiver function studies and correspond with the flannan and w reflectors the structures are truncated or pinch out before they reach the midland valley of scotland the isolated subcrustal structure at station gim on the isle of man may be related to the closure of the iapetus ocean

tectonic units of the alpine collision zone between eastern alps and western turkey abstract we present a map that correlates tectonic units between alps and western turkey accompanied by a text providing access to literature data explaining the concepts used for defining the mapped tectonic units and first order paleogeographic inferences along strike similarities and differences of the alpine eastern mediterranean orogenic system are discussed the map allows 1 for superimposing additional information such as e g post tectonic sedimentary basins manifestations of magmatic activity onto a coherent tectonic framework and 2 for outlining the major features of the alpine eastern mediterranean orogen dinarides hellenides anatolides and taurides are orogens of opposite subduction polarity and direction of major transport with respect to alps and carpathians and polarity switches across the mid hungarian fault zone the dinarides hellenides taurides and apennines consist of nappes detached from the greater adriatic continental margin during cretaceous and cenozoic orogeny internal units form composite nappes that passively carry ophiolites obducted in the latest jurassic earliest cretaceous or during the late cretaceous on top of the greater adriatic margin successions the ophiolites on top of composite nappes do not represent oceanic sutures zones but root in the suture zones of neotethys that formed after obduction suturing between greater adria and the northern and eastern neotethys margin occupied by the tisza and dacia mega units and the pontides occurred in the latest cretaceous along the sava izmir ankara erzincan suture zones the rhodopian orogen is interpreted as a deep crustal nappe stack formed in tandem with the carpatho balkanides fold thrust belt now exposed in a giant core complex exhumed in late eocene to miocene times from below the carpatho balkan orogen and the circum rhodope unit its tectonic position is similar to that of the sakarya unit of the pontides we infer that the rhodope nappe stack formed due to north directed thrusting both rhodopes and pontides are suspected to preserve the westernmost relics of the suture zone of paleotethys

surface wave velocities across arabia the group velocity distribution beneath the arabian plate is investigated using love and rayleigh waves we obtained a balanced path coverage using seismograms generated by earthquakes located along the plate boundaries we measured love and rayleigh wave group velocity dispersion using multiple filter analysis and then performed a tomographic inversion using these observations to estimate lateral group velocity variations in the period range of 5 60 s the love and rayleigh wave results are consistent and show that the average group velocity across arabia increases with increasing period the tomographic results also delineate first order regional structure heterogeneity as well as the sharp transition between the arabian shield and the arabian platform systematic differences are observed in the distribution of the short period group velocities across the two provinces which are consistent with surface geology the slower velocities in the platform reveal the imprint of its thick sedimentary section while faster velocities correlate well with the exposed volcanic flows in the shield shear wave velocity models for the two regions obtained from the inversion of the group velocities confirm results from previous studies of higher s wave velocity in the upper crust beneath the shield this may be due to the present remnants of the oceanic crust ophiolite belts associated with the island arcs evolutionary model of the arabian shield

alakir cay group antalya complex sw turkey a deformed mesozoic carbonate margin abstract the alakir cay group comprises complexly deformed mesozoic sedimentary rocks originally deposited along a passive carbonate margin the sediments now form a tectonically imbricated stack of thrust sheets kumluca zone emplaced westwards over a relatively autochthonous carbonate platform bey daglari zone the kumluca zone is bounded tectonically to the east by mafic and ultramafic rocks with related sediments godene zone representing oceanic crust produced during early stages of continental separation and originally forming the more distal part of the margin detailed mapping and structural analysis allow the thrust sheets to be pulled back to reconstruct a stretch of the carbonate margin about 10 km wide by 25 km long within the thrust sheets fragmentary basal sequences of quartzose sandstones hatip formation derived from the north were laid down during late triassic continental rifting subsequent late triassic halobia and radiolarian bearing calcilutites bozyer foramtion are comparable with peri platform deep water oozes found for example in the bahamas an end triassic hiatus involved substantial down margin sediment redeposition jurassic to early cretaceous sediments include both non calcareous and calcareous silts laid down together with radiolarites in deep water below the carbonate compensation depth karabuk formation an upward transition to cretaceous planktonic foraminiferal chalks is seen in some more proximal sequences tectonic disruption of the margin began in latest cretaceous time and ended with westward thrusting over the carbonate platform in the miocene small scale facies variation of the margin is illustrated by unstretching the thrust sheets and correlation of 33 measured logs particularly the sediments become more distal across the margin away from the carbonate platform along margin variation is especially evident in the thickness and composition of redeposited carbonates in the late triassic hemipelagic rocks comparison with other carbonate margin sequences in the antalya complex and elsewher implies that the alakir cay sediments represent deep water outer margin facies which lapped over adjacent oceanic crust more proximal redeposited carbonates are not seen perhaps due to overthrusting

crustal motion in indonesia from global positioning system measurements terrestrial reference frame 2000 we compute poles of rotation for the australia eurasia and pacific plates based on our analysis of the global gps data we find that regional tectonics is dominated by the interaction of four discrete rotating blocks spanning significant areas of the sunda shelf the south banda arc the bird s head region of new guinea and east sulawesi the largest the sunda shelf block ssh is estimated to be moving 6 3 mm yr se relative to eurasia the south banda block sbb rotates clockwise relative to both the ssh and australia plate resulting in 15 8 mm yr of motion across the timor trough and 60 3 mm yr of shortening across the flores sea southern new guinea forms part of the australia plate from which the bird s head block bhb moves rapidly wsw subducting beneath the seram trough the east sulawesi block rotates clockwise about a nearby axis with respect to the sunda shelf thereby transferring east west shortening between the pacific and eurasia plates into north south shortening across the north sulawesi trench except for the sunda shelf the crustal blocks are all experiencing significant internal deformation in this respect crustal motion in those regions does not fit the microplate tectonics model index terms 1206 geodesy and gravity crustal movements interplate 8155 1243 geodesy and gravity space geodetic surveys 8150 tectonophysics plate boundary general 3040 8158 tectonophysics plate motions present and recent 3040 9320 information related to geographic region asia keywords crustal motion indonesia tectonics gps current plate motions southeast asia

crustal thickness and velocity structure of malay peninsula inferred from joint inversion of receiver functions and surface waves dispersion abstract the malay peninsula is located within the sunda shelf that is subdivided geologically into three distinctive tectonic belts western central and eastern belts the north south orientation of these belts was formed during the paleo tethys subduction process in the late paleozoic bentong raub suture zone separates the central and western belts while extensive studies have been conducted at the surface and near surface scale the subsurface model of the earth s crust and upper mantle layers within this region are relatively few crustal structure model is crucial in investigating the cause of local earthquakes which shocked peninsular malaysia between 2007 and 2009 the present study is conducted adopting the joint inversion of the p wave receiver functions and surface wave dispersions techniques using the data collected from eight seismological stations in the malay peninsula the receiver function for each station was computed using over a thousand tele seismic earthquake waveforms recorded by the three component broadband seismometers for each station the h k was used to determine the vp vs ratio and the depth to the moho this step was conducted to have an initial constraint for the crustal thickness for the surface wave dispersion calculations on the other hand two hundred local and regional earthquakes with focal depth less than 30 km and with magnitudes mb 6 0 and above that occurred along south east asia s ring of fire were analyzed the analyses obtained from these two techniques were jointly inverted through a two phases of velocity inversion to determine the 1 d velocity profile for each station the results of inversion indicate that the moho boundary is getting shallower towards the north of malay peninsula as a 26 km depth of crust mantle boundary were determined in station sklt south thailand furthermore the subsurface profile of the western belt of malay peninsula was also found to be highly complicated with complex receiver function responses being computed beneath the ipm and kum stations where slow velocity zones are identified within the 10 20 km crustal depth the region in southern thailand might also have originated from indochina east malaya block due to similar crustal velocity characteristics found beneath the region compared to the area beneath kom jrm and btdf stations in the southern part of malay peninsula and singapore the vp vs ratios for the crust indicate that the crust is generally undisturbed except for station sklt south thailand this may indicate that the occurrence of a large earthquake in the region is not likely

velocity structure beneath college station alaska from receiver functions abstract time domain inversions of radial receiver functions and forward modeling of radial and tangential receiver functions were used to determine the velocity structure beneath dwwssn station col fairbanks alaska intermediate period waveforms from 57 events recorded between february 1982 and november 1985 were used in the final analysis receiver functions from similar backazimuths and distances are very uniform and were stacked to increase the signal to noise ratio at some azimuths particularly from the west significant energy is observed in the tangential component indicating the existence of heterogeneous structure the calculated velocity profiles are complicated and contain several distinct features that are consistent between the different stacks the most obvious features are two strong velocity increases or boundaries in the lower crust the first of these velocity gradients is between 27 and 32 km a depth that is often associated with the crust mantle transition in this region forward modeling of the receiver function arrivals associated with this boundary indicates that it has a strike of 280 and a dip of at least 10 to the northeast the velocity profiles and forward modeling also indicate a low velocity layer between depths of about 15 and 28 km this layer is consistent with tact results that show a layer at approximately this depth with high electrical conductivity and a lower than expected seismic velocity interpreted to be mesozoic flysch

cao mgo al 2 o 3 sio 2 h 2 o to 35 kb amphibole talc and zoisite dehydration and melting reactions in the silica excess part of the system and their possible significance in subduction zones amphibolite melting and magma fractionation

mesozoic early tertiary passive margin evolution of the pindos ocean nw peloponnese greece abstract sediment starved deep water slope basin facies of passive margins are of particular interest as they record an interplay of processes including plate tectonic evolution elastic sediment input pelagic deposition and relative sea level change in the past insights have come from deep sea drilling of non emplaced passive margins e g eastern u s a and from preserved sequences within sutured units e g the tethyan and iapetus orogenic belts deep water passive margin successions discussed here represent an excellent example of a relatively sediment starved slope basin setting related to the margin of a microcontinent within the neotethyan ocean in the eastern mediterranean region lithologies are preserved as a series of thrust sheets formed during suturing of the neotethys ocean thrusting resulted in regular in sequence thrusting such that the original slope margin setting can be restored with confidence compared to other tethyan passive continental margin abyssal successions e g oman these sedimentary rocks retain remarkable structural coherence allowing exceptionally detailed three dimensional reconstructions of facies patterns and palaeoceanographic conditions the sedimentary successions belong to the pindos zone of western greece pindos group and comprise deep water carbonate siliciclastic and siliceous rocks ranging in age from late triassic to eocene these rocks accumulated along the western margin of a small neotethyan oceanic basin i e pindos ocean separating the continental blocks of adria apulia and pelagonia the oldest sediments comprise disrupted siliciclastic turbidites largely derived from a metamorphic source to the west and deposited on young oceanic basement from the late triassic to latest maastrichtian variable thicknesses of hemipelagic carbonate and proximal carbonate debris flows accumulated in westerly areas while mainly hemipelagic carbonate and more distal calciturbidite were deposited further east this pattern was interrupted by an extended period of siliceous radiolarian dominated sedimentation during the aalenian to tithonian jurassic from latest maastrichtian onwards progressive closure of the pindos oceanic basin is recorded by a gradual change in sediment composition from dominantly carbonate deposition supplied from the gavrovo tripolitza carbonate platform to the west to siliciclastic sediment derived from the north and east during the eocene oligocene eastward subduction of the pindos ocean resulted in deep sea sedimentary lithologies being detached from their oceanic igneous basement as an accretionary prism and emplaced westwards onto the adjacent carbonate platform ending up as a series of thin skinned thrust sheets

plume or no plume emeishan large igneous province in southwest china revisited from receiver function analysis the late permian emeishan large igneous province at the western margin of the yangtze craton and eastern tibet is popularly regarded as the signature of mantle plume impingement onto the lithosphere in this study we investigate the crustal structure and upper mantle discontinuities of this region by employing h k stacking of receiver function and depth domain receiver function our results image the mantle transition zone however no vestiges of any mantle plume upwelling in this area are recorded in our results and the region is characterized by a largely cold domain in contrast our data reveal a region of lower crustal delamination that coincides with the cold mantle transition zone we therefore suggest that the delaminated lower crustal material was recycled into the upper mantle or the mantle transition zone turning the latter into a cold domain the delamination of the lower crust might have also led to asthenospheric upwelling and plume like upwelling from the mantle transition zone that generated the basalts in the emeishan large igneous province

regional seismic hazard posed by the mentawai segment of the sumatran megathrust several lines of evidence have indicated that the mentawai segment of the sumatran megathrust is very likely to rupture within the next few decades the present study is to investigate seismic hazard and risk levels at major cities in sumatra java singapore and the malay peninsula caused by the potential giant earthquakes three scenarios are considered the first one is an mw 8 6 earthquake rupturing the 280 km segment that has been locked since 1797 in the second scenario rupture oc curs along a 600 km segment covering the combined rupture areas of the 1797 and 1833 historical events producing an mw 9 0 earthquake and the third scenario has the same rupture area as the second scenario but with doubled slip amplitude resulting in an mw 9 2 earthquake simulation results indicate that ground motions produced by the hypothetical scenarios are strong enough to cause yielding to medium and high rise buildings in many major cities in sumatra it is vital to ensure that the overall strength stiffness and integrity of the structures are maintained throughout the entire duration of shaking however the ductile detailing in current practice is formulated based on an assumption that ground motions would last from 20 to 40 sec this has not been tested for longer durations of 3 5 min expected from giant earthquakes in singapore and kuala lumpur only medium and high rise buildings especially those located on soft soil sites are at risk given that seismic design has not been required in either city and thus the resulting structures are relatively brittle it is crucial to inves tigate their performance under moderate amplitude long duration ground motions the present study also points out that shifting the response spectrum toward a longer period range becomes significant for sites located far from potential seismic sources which should be carefully considered in formulation of future seismic codes