structural evolution of the central part of the krusne hory erzgebirge mountains in the czech republic evidence for changing stress regime during variscan compression abstract in the central part of the krusne hory erzgebirge mountains the parautochthonous metasedimentary basement has been overthrust by a crustal nappe of fine and coarse grained orthogneisses the thrust boundary is defined by the presence of mafic eclogites with preserved subduction related fabric westward thrusting of an allochthonous unit is associated with the development of the main metamorphic foliation and lineation in non eclogitic lithologies buttressing of the allochthonous body from the west is responsible for the development of late large scale folds with n s trending hinges and vertical axial planes subsequent n s compression leads to large scale folding of both the parautochthonous and allochthonous units this deformation produces km scale antiforms with hinges plunging to the west and is associated with the development of the e w stretching lineation as a result of complete reworking of earlier fabric in the limb zones n s shortening is also associated with the development of small scale folds and brittle ductile kink bands suggesting a decrease in temperature and thus uplift of the whole studied area during this event the last stage of deformation is characterised by the development of kink band folds and a crenulation cleavage these structures suggest a sub vertical direction of principal compression developed exclusively in those parts of the area in which the n s compression produced steep planar fabric

stable isotopic and biomarker evidence of terrigenous organic matter export to the deep sea during tropical storms abstract the global export of organic carbon oc is intimately linked to the total flux of terrestrial sediment to the ocean with the continental margins receiving 90 of the sediment generated by erosion on land recent studies suggest that a substantial amount of particulate oc poc might escape from the shelf and be exported to the continental slope deep sea sector although the mechanisms and magnitude of such deep sea poc transfer remain unknown here we investigate hyperpycnal flow associated total suspended matter tsm collected from water depths of 3000 m near the bottom of sea floor in the gaoping submarine canyon gsc off southwestern taiwan elemental c n isotopic 13 c 15 n and biomarker compositions of tsm were investigated to understand its biogeochemical characteristics a two end member 13 c mixing model indicates that deep sea tsm contains 90 terrigenous oc while a similar mixing model using 15 n reveals a lower proportion 58 organic biomarkers of tsm suggest contributions from a mixture of resuspended continental margin derived marine organic matter om mar and terrigenous sources revealing that terrestrial oc likely mixes with nitrogen rich marine material during rapid transport this study documents that rapid transfer of terrigenous organic matter om terr into the deeper regions of gsc occurred within a week of typhoon morakot likely through hyperpycnal injection of sediment laden warm freshwater from southern taiwan evidence from this typhoon morakot induced hyperpycnal plume event in taiwan demonstrates that extreme storm events provide an efficient way to export terrigenous oc without oxidation to hitherto unknown water depths of deep sea in the oceania region

finite difference modelling of s wave splitting in anisotropic media we have implemented a 3d finite difference scheme to simulate wave propagation in arbitrary anisotropic media the anisotropic media up to orthorhombic symmetry were modelled using a standard staggered grid scheme and beyond monoclinic and triclinic using a rotated staggered grid scheme the rationale of not using rotated staggered grid for all types of anisotropic media is that the rotated staggered grid schemes are more expensive than standard staggered grid schemes for a 1d azimuthally anistropic medium we show a comparison between the seismic data generated by our finite difference code and by the reflectivity algorithm they are in excellent agreement we conducted a study on zero offset shear wave splitting using the finite difference modelling algorithm using the rotated staggered grid scheme our s wave splitting study is mainly focused on fractured media on the scale of seismic wavelenghts small aligned fractures behave as an equivalent anisotropic medium we computed the equivalent elastic properties of the fractures and the background in which the fractures were embedded using low frequency equivalent media theories wave propagation was simulated for both rotationally invariant and corrugated fractures embedded in an isotropic background for one or more than one set of fluid filled and dry fractures s wave splitting was studied for dipping fractures two vertical non orthogonal fractures and corrugated fractures our modelling results confirm that s wave splitting can reveal the fracture infill in the case of dipping fractures s wave splitting has the potential to reveal the angle between the two vertical fractures we also notice that in the case of vertical corrugated fractures s wave splitting is sensitive to the fracture infill

variscan tectonics of central europe postaccretionary intraplate deformation of weak continental lithosphere the area occupied by the variscan belt of central europe forms part of gondwana derived microplates essentially avalonia and armorica that according to paleomagnetic data juxtaposed baltica and laurentia from the upper ordovician to the lower devonian the actual structure of this area is a puzzle of rather small fault bounded crustal blocks different in p t t histories which was created by later tectonic processes at around 360 to 320 ma according to a common view and by contrast to paleomagnetic data the structural record of fault bounded blocks is interpreted in terms of mid devonian to lower carboniferous amalgamation of narrow continental plates represented by the fault bounded blocks themselves however this is not supported in this article instead it will be shown that fault systems and fault bounded blocks were created by intraplate deformation of a weak domain of gondwana derived continental lithosphere significantly after its accretion deformation was partitioned into newly formed deep seated strike slip and kinematically connected reverse or normal detachment systems large translation magnitudes caused juxtaposition of crustal areas of variable thickness until they were emplaced along the fault systems the various categories of fault bounded complexes record different tectonic events category 1 metamorphic complexes represent deep seated parts of thickened crust some time before unroofing on the detachment systems between about 340 360 and 320 ma however the record of subduction and extreme crustal thickening during earlier stages of the collision history was erased to a high degree and is only preserved by mineral and structural relics strike slip and detachment systems propagated across and dismembered tectonic boundaries formed during these early events category 2 metamorphic complexes and the barrandian basin recording predominant pre late devonian metamorphic or stratigraphic events represent the brittle upper crustal parts during continuing metamorphism in the category 1 complexes weakly or unmetamorphosed lower paleozoic category 3 basins represent areas of thinned continental crust and record subsidence before and to some degree during activity of detachment systems the complex overall kinematic pattern of block bounding strike slip and detachment systems indicates compression and extension acting simultaneously this probably reflects the effects of continuing oblique plate convergence rotation and wsw extrusion of fault bounded blocks in addition to heating and extensional flow of previously thickened crustal areas

u pb shrimp and nd isotopic data from the western bohemian massif bayerischer wald germany implications for upper vendian and lower ordovician magmatism u pb shrimp dating of zircons of metamagmatites from the bayerischer wald germany reveals a complex evolution of this section of the moldanubian zone exposed in the western bohemian massif of the central european variscan belt in the south western part of the bayerischer wald upper vendian magmatism is constrained by pooled 206pb 238u mean ages of 555 12 549 7 and 549 6 ma from metarhyolites and a metabasite inherited zircon cores were not observed zircon overgrowths yielding pooled 206pb 238u ages of 316 10 and 319 5 ma provide evidence for variscan metamorphic zircon growth cathodoluminescence imaging reveals a two stage metamorphic overprint

nepheloid layer dynamics in the northern portuguese shelf abstract a general hydrographic and nephelometric survey of the nw portuguese continental shelf and upper slope was undertaken under winter and spring conditions the nepheloid layer dynamics along the shelf during three cruises were controlled principally by the following factors a the hydrography of the shelf slope waters i e the nepheloid layers followed isopycnals and water masses b prevalence of upwelling or downwelling circulation over the shelf c dispersion of material by river discharge mainly the douro river d resuspension of mid shelf fine deposits induced by swell e peculiar morphology with the presence of porto canyon and outer shelf rock outcrops the general circulation controls the seaward extension of the nepheloid layers in winter under dominant downwelling conditions an intense bottom nepheloid layer bnl was observed on the shelf due to river borne particle supply and remobilization of mid shelf muddy sediments depth 100 m in this period the bnl increased in thickness to the top of the slope following the isopycnals near the shelf break the bnl detached to form intermediate nepheloid layers inl small inls appear deeper in some areas of the slope a surface nepheloid layer snl appears in the surface water over the shelf and slope in spring biological particles mainly contribute to the snl which is separated from the bnl by a zone of clear water in winter the snl is restricted to the inner shelf where there are high inputs of fluvial particles downwelling circulation probably induces transport of shelf particles to deeper waters in the bnl in spring the predominant circulation was southward upwelling the water column was highly stratified and dispersion of particles in the snl was offshore

rectification of the heading and tilting of sediment trap arrays due to strong tidal currents in a submarine canyon 1 two taut line sediment trap moorings deployed in kao ping submarine canyon were subjected to tidal flows resulting in significant vertical movements and tilt of the mounted instruments based on simple trigonometric relations the true heading and tilt angles were derived from the raw readings of heading pitch and roll of the two nortek aquadopp doppler current meters nadcm the true tilt and heading angles of the nadcms were highly correlated with depth and reflected the orientation of the axis of the canyon respectively the precluded data points of tilt and heading angles therefore can be reconstructed our study suggests a systematic way to rectify the heading and tilting of a sediment trap array of the mounted nadcm from raw readings of the heading pitch and roll meters

bulk particulate organic carbon in the east china sea tidal influence and bottom transport abstract five oceanographic surveys were carried out in the east china sea ecs and yellow sea from 1999 to 2003 in all seven different sections were surveyed but one section the pn section was observed on every cruise two time series stations were also surveyed one located at the changjiang river mouth the other over the continental shelf in the pn section we identified biogeochemical characteristics for waters close to the changjiang estuary and in the kuroshio waters kw respectively resuspension is a strong feature near bottom over the ecs continental shelf with suspended matter values 13 times higher than that for the surface a model of particulate organic carbon poc dynamics based on a rectangle equation reveals that poc concentration close to the changjiang estuary varies with a semidiurnal period of 13 h coinciding with the tidal period the upper limit for poc residence times in the seasons we covered over the shelf are estimated to be on the order of weeks and generally increase seaward from near the changjiang estuary to the kw short poc residence times suggest that poc in the ecs is rapidly exported from euphotic waters a nepheloid layer observed as elevated suspended matter in near the bottom of the water column is important in particle transfer over the shelf especially in winter when the residual current flows mainly eastward cross shelf transport of poc via the nepheloid layer is estimated to be 0 22 1012 g yr 1 comparison with other work indicates that poc transport is 2 of the changjiang poc input

sea level and climatic controls on turbidite occurrence for the past 26 kyr on the flank of the gaoping canyon off sw taiwan submarine canyons are major conduits for delivery of sediments originating from the continental margin into the deep sea here we analyze the effects of changing sea levels and climate e g sediment supply on the frequency of turbidites over the last 26 kyr our study is based on high resolution age controls for turbidites in core md178 10 3291 from a water depth of 2070 m on the flank of the gaoping canyon offshore in sw taiwan unlike most other submarine canyons worldwide the head of the gaoping canyon has remained connected to the river mouth during the recent flooding of the continental shelf our results reveal that turbidity currents are less frequent during periods of sea level lowstand in contrast turbidity currents have been more frequent since 12 kyr bp during the final stage of rising sea level and sea level highstands this may be the result of increased terrestrial sediment delivery due to enhanced rainfall intensity moreover comparing to other source to sink systems the turbidite occurrence in the flank of gaoping canyon through the last glacial cycle might have been more strongly influenced by climatic changes due to short sediment storage response time

misalignment of the orientation of fractures and the principal axes for p and s waves in rocks containing multiple non orthogonal fracture sets summary azimuthal anisotropy in rocks can result from the presence of one or more sets of partially aligned fractures with orientations determined by the stress history of the rock a shear wave propagating in an azimuthally anisotropic medium splits into two components with diverent polarizations if the source polarization is not aligned with the principal axes of the medium in the presence of two or more non orthogonal sets of vertical fractures the symmetry of the medium may be approximated as monoclinic with a horizontal plane of mirror symmetry if in the absence of fractures the rock is transversely isotropic ti with the symmetry axis perpendicular to the bedding plane for such a medium the fast and slow polarization directions for vertically propagating shear waves are not parallel or perpendicular to any of the fracture planes but lie in directions given by the principal axes of a second rank fracture compliance tensor this tensor is independent of the normal compliance of the fractures it follows that for vertical propagation of shear waves in a vertically fractured ti medium any number of arbitrarily oriented vertical fracture sets is equivalent to two mutually perpendicular fracture sets provided that the seismic wavelength is large compared to the size of the fractures for ovsets typical of surface seismic acquisition the p wave velocity at fixed ovset varies with azimuth as cos 2 w w 0 where w is the azimuth measured with respect to the fast polarization direction for a vertically polarized shear wave w 0 depends on both the normal and the shear compliance of the fractures and may diver from zero if the ratio of the normal to shear compliance of the fractures varies significantly between fracture sets if this ratio is similar for all fractures w 0 0 and the principal axes of the variation in p wave velocity with azimuth for fixed ovset are determined by the principal axes of the second rank fracture compliance tensor

turbidity of waters over the northwest iberian continental margin in omex ii ii 9 cruises gathered optical data principally by transmissometer the distribution of optical turbidity caused by concentration of particulate matter pmc in the water column over the northern iberianmargin shows several features related to hydrography it is concluded that a signal of pmc seen in mediterranean water mw found north of 42 n is not carried from its source at the gibraltar sill and gulf of cadiz because it is shown using intermediate stations that this turbid plume decays mainly by fall out but also partly by mixing to very low levels around southern portugal pmc maxima sometimes seen in mw on the northern iberianmargin are thus most likely to result from intermittent local resuspension by mw interacting with slope sediments the highest turbidity is found over the upper slope and is the result of i shelf edge resuspension and off shelf flow of turbid plumes mainly between 100 and 300 m depth and ii resuspension under the slope current aided by internal waves in the depth range 500 800 m where the density gradient between enacw and mw is maximal below the mw flows are generally slow and turbidity is low the bottom nepheloid layer in deep water is also weak with pmc values 100 mg m 3 the focus of resuspension activity on the upper slope means that the region is an efficient exporter to the ocean of sediment that either escapes from the shelf or sinks to the bed from surface production this accounts for upper slope sediments recorded in other studies as sandy or in places as rocky bottom

suspended particulate matter and nepheloid layers over the southern margin of the cretan sea n e mediterranean seasonal distribution and dynamics seawater along the southern margin of the cretan sea may 1994 september 1995 has been found to have light transmission values ranging from 79 to 94 corresponding to spm values ranging from 1 5 mg l 1 to 0 2 mg l 1 the highest spm concentrations mostly of terrigenous origin were found close to the sea bed over the shelf break and upper slope the origins of spm in the surface waters 150 m is principally biogenic the occurrence of nepheloid layers at intermediate depths within the upper water column is mostly a result of density stratification the dynamics of spm distributions are governed by the 2 gyre system which induces a general onslope flow and so inhibits the seaward dispersion of the relatively more turbid coastal shelf waters this is in agreement with the virtual absence of suspensates of terrigenous origin offshore of the shelf break near bottom nepheloid layers bnl and detached intermediate nepheloid layers occur in the vicinity of the shelf break and over upper slope region these may be explained by resuspension induced by near bed current activity and breaking of internal waves high concentrations of spm near the seabed may be caused by anthropogenic trawling activity occasionally the formation of bnl may result from local seismic activity resulting in gravity driven mass movements

extending a thickened crustal bulge toward a new geodynamic evolution model of the paleozoic nw bohemian massif german continental deep drilling site se germany abstract fault bounded tectonic metamorphic complexes assembling the nw bohemian massif around the german continental deep drilling ktb site are seen to be extremely heterogeneous in tectonic and metamorphic histories in current models the different complexes were supposed to reflect a puzzle of small pre devonian microplates and the related collision events supposedly lasted until the carboniferous opposed to these models it will be shown that all the boundaries among the complexes were formed by detachment late in a prolonged overall geodynamic history of a thickened crustal bulge during extensional tectonics and associated thermal events that outlasted the onset of collision in the silurian lower devonian by about 70 80 ma micro structures petrological and geochronological data of individual complexes predominantly preserve the late stages rather than the unbroken record of their tectonometamorphic histories such partial histories strongly different among individual complexes depict diverse snapshots taken at different places in the evolving thickened crustal bulge and at different instants in its overall evolution and do not define different precollisional microplates predominantly p t and deformation episodes after terrane juxtaposition are preserved this article presents an integrated view of the structural geology microscopic fabrics p t data and geochronology of such diverse metamorphic complexes this integrated view provides a new understanding of 1 the tectonic evolution during upper silurian devonian collision of the gondwana derived central european lithosphere with laurussia 2 the postaccretionary events that lasted through the upper carboniferous and 3 the earlier lower ordovician metamorphic and magmatic history which is only locally recorded metamorphic complexes occupying the structurally highest position upper tectonic complexes record devonian and earlier tectonometamorphic and magmatic events after the mid devonian such complexes did not experience any metamorphism the recorded devonian events consist of subduction and exhumation of hp rocks and their exhumation involved thrusting and extensional tectonics upper tectonic complexes comprise fragments of both the plate that was subducted in this period and the overriding plate in the footwall carboniferous extension has brought upper tectonic complexes against metamorphic complexes that essentially record lower and upper carboniferous tectonometamorphic and magmatic events lower tectonic complexes in the lower tectonic complexes such events are 1 consecutive extensional stages that created at least three sets of ductile normal detachment systems intersecting each other and various associated thermal pulses as well as 2 predetachment events that are only recorded as petrologic and structural relics transposed during extension inferred as predetachment events are crustal subduction as well as stacking that outlasted thrusting and exhumation of the upper tectonic complexes in the deeper portion of the thickened crustal bulge represented by the lower tectonic complexes spatial variations of p t t d histories during decompression occurred as a result of continued differential exhumation on the three sets of detachment systems and also from various thermal pulses that have affected different parts of this section during progressive shearing and exhumation to various degrees whereas the lower tectonic complexes of the erzgebirge gneiss dome preserve the record of a lower carboniferous history of hp metamorphism and crustal thickening followed by extension in those of the oberpfalz region ktb site a major upper carboniferous thermal pulse mostly erased the pre upper carboniferous strain fabrics and metamorphic record in the oberpfalz region ongoing extension emplaced mid crustal rocks that pervasively equilibrated in the upper carboniferous at high temperatures and low pressures low p t ratio against rocks not exposed to high temperatures at that time in summary a prolonged postaccretionary history concealed large scale structural relationships linked to crustal subduction and thickening associated with former juxtaposition of gondwana lithosphere to laurussia polyphase crustal extension and strike slip created the variety of different metamorphic tectonic complexes observed in the nw bohemian massif

late collisional granites in the variscan erzgebirge germany the late collisional erzgebirge granites 325 318 ma were introduction emplaced at shallow crustal levels in the variscan metamorphic the erzgebirge is a ne sw trending antiformal structure basement shortly after large scale extension caused by orogenic exposing variscan crystalline basement rocks at the northcollapse these granites comprise mildly peraluminous transitional ern margin of the bohemian massif the region is famous i s types and strongly peraluminous s type rocks which can be among economic geologists for its extensive and highly subdivided into three major groups low f biotite granites low f variable metallic ore deposits which have been mined two mica granites and high f high p2o5 li mica granites the since the middle ages e g stemprok seltmann 1994 highest degree of differentiation is reached in the li mica granites tischendorf forster 1994 and for the classic studies which exhibit strongly elevated concentrations of p f li rb cs in the fields of economic geology mining and metallurgy ta sn w and u but very low ti mg co ni sr ba y zr chemistry and mineralogy e g werner 1791 breithaupt hf th and rare earth elements crystal melt fractionation is the 1849 agricola 1974 dominant process controlling the bulk composition of all groups of as in many of the other variscan provinces in central granites however metasomatic processes involving late stage residual europe granitic rocks make up a large proportion of the melts and high t orthomagmatic fluids became increasingly more exposed rocks in the erzgebirge and a great variety of important in highly evolved units and have modified the abundances compositional and textural types occur fig 1 knowof mobile elements p f li rb cs ba sr in the li mica ledge of the processes involved in the generation and granites particularly isotopic and geochemical characteristics suggest evolution of these silicic magmas is essential for underthat the three granite groups cannot be derived from a common standing heat and mass transport during the variscan precursor magma their discrete compositions are source related orogeny and also for the formation of metallic ore and are attributed to melting of quartzo feldspathic and pelitic deposits several lines of evidence indicate that early crustal lithologies in different proportions granites are common in high temperature sn w deposits are associated with the the central european variscides but the erzgebirge is unusual for emplacement of highly evolved volatile rich granitic the predominance of evolved li mica granites associated with melts tischendorf 1986 forster tischendorf 1992 economically important sn w and u deposits the abundance of stemprok 1993 the role of the granites in formation of li mica granites is attributed to a combination of favourable factors later permian u pb zn and younger ore mineralization 1 low degrees of anatectic melting of crustal protoliths 2 wide f ba is controversial but good evidence exists that the distribution of fertile lithologies rich in large ion lithophile elements vein type u deposits owe their uranium to leaching from and ore elements 3 extended magmatic differentiation by crystal the uraninite rich granites e g tischendorf forster melt fractionation and subsequent autometasomatism 1994

reflection transmission coefficients and azimuthal anisotropy in marine seismic studies summary introduce two methods for inferring the direction of vertical fractures from marine seismic data first we derive the necessary reflection and transmission coefficients for an interface between a liquid and an azimuthally anisotropic solid next we show that multicomponent ocean bottom seismometer data from surface airgun sources along two perpendicular shot lines can be rotated into the principal directions of azimuthal anisotropy to determine the orientation of vertical fractures finally we show that p wave amplitude versus offset avo depends on the orientation of the shot line with respect to the vertical fractures thus p wave avo can also be used to determine fracture orientation

trench parallel flow beneath the nazca plate from seismic anisotropy shear wave splitting of s and sks phases reveals the anisotropy and strain field of the mantle beneath the subducting nazca plate cocos plate and the caribbean region these observations can be used to test models of mantle flow two dimensional entrained mantle flow beneath the subducting nazca slab is not consistent with the data rather there is evidence for horizontal trench parallel flow in the mantle beneath the nazca plate along much of the andean subduction zone trench parallel flow is attributale utable to retrograde motion of the slab the decoupling of the slab and underlying mantle and a partial barrier to flow at depth resulting in lateral mantle flow beneath the slab such flow facilitates the transfer of material from the shrinking mantle reservoir beneath the pacific basin to the growing mantle reservoir beneath the atlantic basin trenchparallel flow may explain the eastward motions of the caribbean and scotia sea plates the anomalously shallow bathymetry of the eastern nazca plate the long wavelength geoid high over western south america and it may contribute to the high elevation and intense deformation of the central andes

discussion on structural evolution of the central part of the krusne hory erzgebirge mountains in the czech republic evidence for changing stress regime during the variscan by j konopasek k schulmann and o lexa

in situ estimations of the density and porosity of flocs of varying sizes in a submarine canyon abstract this paper introduces a new method to estimate in situ floc density and porosity of three particle size classes 0 45 10 10 63 and 63 250 m lisst 100 and catnet a novel on board filtration system of nested filters were used to measure suspended particle volume and mass concentrations of 32 and 3 size classes respectively two field experiments were conducted in 2004 and 2006 in the head region of gaoping submarine canyon gpsc to test this method in each experiment ctd and lisst 100 profiling and simultaneous water sampling were carried out on board r v ocean research iii in 2004 the water samples were filtered in the laboratory after the cruise using traditional methods catnet was used in 2006 and the seawater filtration was done on board assuming the observed suspended particles were all flocs composed of primary particles with assumed density of 2 65 g cm 3 and interstitial water with assumed density of 1 025 g cm 3 we estimated the volume of primary particles the volume difference between flocs measured from lisst 100 and primary particles is the interstitial pore space in flocs subsequently the porosity of a floc particle is the ratio of the volume of the interstitial pore space to that of the floc particle results for 2004 show erroneous values of estimated floc porosities which do not appear in 2006 the major difference is that the seawater was filtered immediately on board using catnet in 2006 after removing erroneous data related to after cruise filtering the averaged floc porosity and density in the three grain size classes were 47 0 64 0 85 9 and 1 89 1 61 1 25 g cm 3 respectively there is a trend that larger particles have lower density which is supported by literature the temporal variations of floc density and porosity of all three particle size groups were larger in the surface than near the bottom of the submarine canyon this vertical variability resulted from flocculation and biogenic processes in the surface of the coastal ocean and the terrestrial source of the gaoping river floc density is an important physical parameter to evaluate the settling flux of suspended sediments in estuarine and marine environments this approach provides direct in situ floc bulk densities of different grain size classes which has advantages over conventional methods

reconstruction of silicate weathering intensity and paleoenvironmental change during the late quaternary in the zhuoshui river catchment in taiwan taiwan island is one of the best places in the world for the study of earth surface processes during the late quaternary because of its unique geological geographic and climatic settings in this study we present sedimentary and element geochemical data of core jrd s drilled on the zhuoshui river delta aiming to examine the changes of sediment provenance and silicate weathering intensity in response to monsoon climate variability since the last glacial period similar rare earth element ree compositions between the core sediments and modern zhuoshui river samples suggest the zhuoshui watershed was the dominant sediment provenance for the late quaternary deposition in the river mouth while the mainland rivers in southeast china including the changjiang yangtze river could not be the major sediment suppliers due to the stable sediment provenance the geochemical proxy of the core sediments reveals the change of silicate weathering intensity during the late quaternary in the zhuoshui watershed was primarily driven by monsoon climate under an active tectonic setting the weaker monsoonal precipitation in the last glaciation caused weaker erosion thus less sediment supply in the mountainous watershed and thus increased the sediment residence time and silicate weathering intensity in contrast the enhanced holocene monsoonal precipitation might greatly increase the physical erosion and sediment transfer rate from land to sea which consequently produced more less weathered sediments this study provides in depth insights into sedimentary response to tectonic and monsoon climatic changes during the quaternary on a tectonically active high standing island which increases our better understanding of earth surface processes in the unique continental margin

3 d viscoelastic anisotropic modeling of data from a multicomponent multiazimuth seismic experiment in northeast texas three component seismic data were acquired along six azimuths at a site in northeast texas sources were inclined impacts combined to produce equivalent vertical and crossline horizontal components the data were analyzed by iterative modeling using a new 3 d staggered grid finite differencing scheme the 3 d model is defined in terms of spatially variable anisotropic viscoelastic parameters p velocity s velocity density qp and qs and converted to elastic tensor components and relaxation times for computation simultaneous fitting of amplitudes of near surface reverberations surface waves converted waves and deeper reflections gives an anisotropic viscoelastic model that provides constraints on earth properties the assumption of transverse isotropy in previous experiments is supported by the results of this experiment the final model consists of a stack of flat layers each of which has isotropic p velocity qp and qs the wills point and kincaid shales are strongly transversely isotropic

using avo for fracture detection analytic basis and practical solutions tight low porosity reservoirs can produce significant amounts of hydrocarbons if fracture networks provide the necessary permeability characterization of naturally fractured reservoirs using surface seismic data is an important exploration problem that has attracted much attention in the literature tle for example had an entire issue august 1996 on this subject while the data and modeling in existing publications demonstrate that fracturing causes significant azimuthal variation in recorded seismic signatures the problem is how to infer fracture parameters from these data

particle dynamics of the surface intermediate and benthic nepheloid layers under contrasting conditions of summer monsoon and typhoon winds on the boundary between the taiwan strait and east china sea abstract two shipboard surveys of hydrographics and sediment dynamics were conducted off the mouth of minjiang the min river in july 2012 under contrasting summer monsoon and typhoon wind conditions observations included profiles of conductivity temperature depth fluorescence and suspended particle volume concentration and current velocity in addition water samples were taken for the analyses of mass concentration poc and chlorophyll of suspended sediment seafloor sediment samples were also taken for grain size analysis nepheloid layers nls were observed at surface intermediate and benthic depths snl inl bnl respectively the nl dynamics under the two wind conditions were mainly controlled by 1 the presence of the minjiang river plume and terrigenous material it carries 2 water column stability affected by wind current and waves 3 current induced resuspension of seafloor sediment and 4 physically coupled biological activities the wind field was the major forcing controlling the observed flow field and the upper water column stability in the typical summer condition southerly winds induced offshore directed currents enhancing the seaward dispersal of the minjiang river plume facilitating water column stratification thereby forming 3 nls in the water column phytoplankton growth was enhanced by terrigenous material and sunlight the suspension of the seafloor sediment was the one of the major sources for suspended particles in these nls furthermore the c n ratio of poc in the three nls is 5 72 almost identical to the redfield ratio indicating their predominant marine origin conversely under typhoon related northerly winds the offshore spread of the river plume was restricted the reduced riverine input and enhanced mixing resulted in the disappearance of the snl elevated turbidity in the inl was largely due to the presence of phytoplankton while the bnl was comprised of sediment resuspended off the seafloor and from horizontal advection our results suggest that the presence of the river plume from the minjiang at the study site sets the condition for the snl dynamics the dynamics of inl and bnl were dominated by the wind field and to a lesser degree the wave field and tidal current

palaeozoic terrane amalgamation in central europe a ree and sm nd isotope study of the pre variscan basement ne bohemian massif

inferring protoliths of high grade metamorphic gneisses of the erzgebirge using zirconology geochemistry and comparison with lower grade rocks from lusatia saxothuringia germany protoliths of highly metamorphosed gneisses from the erzgebirge are deduced from the morphology age and chemistry of zircons as well as from whole rock geochemistry and are compared with lower grade rocks of lusatia gneisses with similar structural appearance and or geochemical pattern may have quite different protoliths the oldest rocks in the erzgebirge are paragneisses representing meta greywackes and meta conglomerates the youngest group of zircon of meta greywackes that did not undergo pb loss represents the youngest igneous component for source rocks about 575 ma similar ages and zircon morphology reflect the subordinate formation of new zircon grains or only zircon rims in the augengneiss from barenstein and wolkenstein which probably represent metamorphic equivalents to lower cambrian two mica granodiorites from lusatia bulk rock chemistry intense fracturing and high u and th concentrations of zircons suggest deformation induced and fluid enhanced recrystallisation of zircon grains temperatures during tectonic overprinting too low to reset zircon ages indicate mid or upper crustal levels for shearing recorded in these augengneisses lower cambrian 540 ma granodiorites are widespread in lusatia but are exclusively represented by the freiberg gneiss dome in the eastern erzgebirge ordovician protolith ages were recorded by zircons from the augengneisses of the reitzenhain catherine dome and the schwarzenberg dome western erzgebirge documenting significant regional differences between the eastern and the western erzgebirge 540 vs 490 ma in the western erzgebirge most meta volcanic rocks muscovite gneisses and meta granites mainly red augengneisses yield ordovician zircon ages whereas in the eastern part similar rocks mainly recorded lower cambrian protolith ages zircon overprinting was highest within discrete tectonic zones where the combination of fluid infiltration and deformation induced variable degrees of recrystallisation and formation of a new augengneiss structure variable degrees of pb loss caused age shifts that do not correspond to changes in zircon morphology but may be associated with u and th enrichments major changes in bulk rock composition appear to be restricted to discrete zones and to u hp nappes whereas gneisses with a mp mt metamorphic overprint basically show no geochemical modifications

cyclone induced hyperpycnal turbidity currents in a submarine canyon 1 density currents such as turbidity currents are major transport agents in various terrestrial lacustrine and marine environments worldwide however a gap exists between those who study the deposits by turbidity currents turbidite on a field scale and those who study turbidity currents using small scale laboratory experiments and theoretical numerical models we report two typhoon triggered hyperpycnal turbidity current events observed in a submarine canyon our findings verify turbidite sequences with the characteristics of suspended sediment carried by passing turbidity currents that displayed distinct waxing and waning phases our study also confirms the direct link between typhoon triggered hyperpycnal flows in a small mountainous river and turbidity currents in a nearby submarine canyon that transport sediment to the deep sea efficiently

fast tectonometamorphism and exhumation in the type area of the barrovian and buchan zones the beginning of the grampian episode of tectonometamorphism in scotland is dated by collision and obduction of the ballantrae ophiolite complex at 478 8 ma for the first time we have used zircon and garnet to radiometrically date the peak of the caledonian buchan and barrovian tectonometamorphism in their type areas as contemporaneous at 467 2 5 ma detrital garnet from the neighboring southern uplands flysch terrane has the same radiometric age and occurs in 465 2 5 ma molasse in the midland valley we show that the entire grampian episode lasted 15 2 5 m y and that it took fewer than 7 6 m y to expose high grade rocks following the peak of metamorphism those who study precambrian orogeny should note the brevity of this scottish tectonometamorphic episode and the speed of exhumation

shear wave anisotropy in the mariana subduction zone to determine the location strength and orientation of seismic anisotropy in the mariana subduction zone beneath guam we evaluated shear wave splitting in local s regional s and scs and teleseismic core phases such as sks recorded at station gumo fast directions from the local s phases have an average azimuth of 45 and splitting times range from 0 1 s to 0 4 s for local s phases from events within the southeastern half of the subducting slab splitting parameters manifest minimal frequency dependence in both fast direction and splitting time however for the remaining local s phases in the data set fast directions vary with frequency content no well constrained splitting parameters were obtained for the regional and teleseismic phases but the particle motions of these unsplit phases are consistent with an average anisotropic fast direction of 45 anisotropy due solely to olivine oriented by slab entrained flow in the mantle wedge would produce local s fast directions at 66 and anisotropy due solely to fossil seafloor spreading in the subducting slab would yield fast directions at 20 to 30 neither of these predictions is consistent with the observed fast directions however the observed splitting including the frequency dependent fast directions can be explained by models containing anisotropy in both the slab and wedge and possibly although not necessarily anisotropy due to recent extension in the overriding philippine sea plate

quantifying tidal signatures of the benthic nepheloid layer in gaoping submarine canyon in southern taiwan abstract the benthic nepheloid layer bnl has been observed in the head region of the gaoping kaoping submarine canyon kpsc throughout a year the top of the bnl could be as high as 100 m above the canyon floor in which the suspended sediment concentration ssc could be as high as 30 mg l in the bnl sand sized particles comprise the largest size class in the suspended sediment population based on three one month time series observations near the canyon floor of along canyon velocity water temperature and the volume concentration vc of clay very fine to medium silt coarse silt and sand size classes in 2000 2002 and 2004 the bnl is strongly modulated by the tides at semidiurnal diurnal quarter and sixth diurnal and spring neap frequencies in the course of a semidiurnal tidal cycle the flood up canyon current brings colder water from the seaward part of the canyon causing the ssc and the thickness of the bnl to increase the ssc immediately near the canyon floor also increases in response to the maximum flood and ebb currents of the m 2 tide the tidal to total energy ratio er of the along canyon flow is between 70 80 and between 50 80 among the suspended sediment of clay very fine to medium silt coarse silt and sand size classes the m 2 is the most important tidal constituent in the temporal variations of along canyon flow water temperature and the vc of the four size classes the local phase differences between the forcing velocity and the responses temperature and vc at the m 2 frequency show distinct phase lock that suggests patterns of standing and progressive internal tides suspended sediments in the bnl also respond to the m 2 forcing in a coherent fashion suspended sediment movements are strongly affected by nonlinear processes as indicated by the elevated values of the amplitude ratio of m 4 m 2 of the suspended sediment size classes comparing to that of the flow the cross canyon geometry and the slope of the submarine canyon floor affect the propagation of the barotropic and internal tides which in turn affect the nonlinearity generation in the bnl

resorption growth solid state recrystallisation and annealing of granulite facies zircon a case study from the central erzgebirge bohemian massif zircon crystals have been investigated from a gneiss area in the central erzgebirge bohemian massif where small occurrences lenses of granulites and sometimes eclogites are located within amphibolite facies gneisses geological relationships indicate that leucocratic quartzofeldspathic rocks within the granulite boudins represent melts whereas garnet rich melanocratic rocks are considered restites derived through multiple extraction of the leucocratic melts the morphology of zircon crystals is quite different in these two types of granulites with rounding pointing to higher zircon resorption in garnet rich rocks due to multiple interaction with melts extensive new zircon growth can be demonstrated within granulitic boudins on the basis of zircon morphology internal zircon textures and age data the newly formed zircon grains and rims are non cathodoluminescent and yield an age of about 340 ma secondary ionisation mass spectrometry sims and zircon evaporation raman microprobe investigations revealed heterogeneous metamictisation within zircon grains and pronounced damage of the zircon structure in u rich non cathodoluminescent zircon rims the common reverse discordance of such non cathodoluminescent zircon rims may be explained as a result of preferential pb sputtering during sims analysis leading to apparent pb excess which seems to occur principally in the most damaged zircon domains it is proposed from field relationships that surrounding gneisses although equilibrated under amphibolite facies conditions experienced the same metamorphic pt history as the granulites these amphibolite facies rocks contain zircon distinct from the granulite zircon populations with morphologies and internal textures typical for their protolith rocks implying only slight zircon changes due to hp overprint new zircon growth is here mostly limited to the appearance of very rare new grains or more commonly to formation of thin overgrowths the internal texture of these zircon crystals shows clear signs of solid state recrystallisation leading in most cases to a partial resetting of their u pb ages mainly due to pb loss in addition u contents are slightly higher in cl dark rims that we interpret to have formed mainly due to solid state recrystallisation most evaporation and sims ages vary between protolith rock age and 340 ma so that the interpretation of the 340 ma age is not unambiguous it could be explained as the age of zircon crystallisation from a u rich and th depleted melt or alternatively as a resetting age due to solid state recrystallisation resulting from melt or fluid interaction with old zircon it is difficult to determine at which stage of metamorphic evolution new zircon growth occurred in the granulitic boudins and remains unclear that zircon growth occurred at peak metamorphic conditions

sediment dynamics in a submarine canyon a case of river sea interaction this paper presents findings from a 1 month field experiment conducted during the flood season of 2000 on the southern coast of taiwan to examine the delivery of lithogenic siliciclastic sediment to kao ping submarine canyon from the nearby kao ping river and shelf sources and the transport of suspended lithogenic and nonlithogenic particles near the canyon floor collected time series data included simultaneous measurements of coastal winds salinity temperature flow field suspended sediment concentration ssc and size composition of suspended particles at the river mouth and inside the submarine canyon as well as results from seawater and sediment trap data other collected data included river discharge and sediment load and hydrographic measurements along and across the axis of the canyon during the experiment two significant episodic river sediment discharge events occurred relating to a typhoon and extreme precipitation conditions the findings show that theoretically the time difference between sand and clay siliciclastic grains to settle from the sea surface to the canyon floor is on the order of hours to months analogous to a sorting process river plume dynamics and the coastal wind field largely control the delivery of terrigenous fine grained sediment to the canyon inside the canyon the behavior of suspended lithogenic and nonlithogenic particles of different sizes can be differentiated into a coarse grained group sand which forms the drop in population and a fine grained group mud which forms the standing population each group has distinct spectral characteristics the coarse grained group is delivered directly to the canyon by the river effluent and by wave resuspension of the shelf substrate during the study period the net transport of suspended particles near the canyon floor was landward mostly by tidal currents whose direction was also modulated by spring neap tide both lithogenic and nonlithogenic particles contribute to high mass fluxes exceeding 700 g m 2 day 1 in the lower part of the canyon this river sea system represents a type of systems that consist of three geographically separated dynamic entities the river plume the shelf and the canyon under fair weather conditions the river plume and shelf processes are coupled through the tide and wind field the river and canyon form a direct source to sink link via coarse grained siliciclastic sediment during the flood season in both continuous and pulsed fashion in the typhoon season the shelf becomes a pulsed source region for coarse grained sediment

elastic wave propagation in media with parallel fractures and aligned cracks a model of parallel slip interfaces simulates the behaviour of a fracture system composed of large closely spaced aligned joints the model admits any fracture system anisotropy triclinic the most general monoclinic orthorhombic or transversely isotropic and this is specified by the form of the 3 3 fracture system compliance matrix the fracture system may be embedded in an anisotropic elastic background with no restrictions on the type of anisotropy to compute the long wavelength equivalent moduli of the fractured medium requires at most the inversion of two 3 3 matrices when the fractures are assumed on average to have rotational symmetry transversely isotropic fracture system behaviour and the background is assumed isotropic the resulting equivalent medium is transversely isotropic and the effect of the additional compliance of the fracture system may be specified by two parameters in addition to the two isotropic parameters of the isotropic background dilute systems of flat aligned microcracks in an isotropic background yield an equivalent medium of the same form as that of the isotropic medium with large joints i e there are two additional parameters due to the presence of the microcracks which play roles in the stress strain relations of the equivalent medium identical to those played by the parameters due to the presence of large joints thus knowledge of the total of four parameters describing the anisotropy of such a fractured medium tells nothing of the size or concentration of the aligned fractures but does contain information as to the overall excess compliance due to the fracture system and its orientation as the aligned microcracks which were assumed to be ellipsoidal with very small aspect ratio are allowed to become non fiat i e have a growing aspect ratio the moduli of the equivalent medium begin to diverge from the standard form of the moduli for flat cracks the divergence is faster for higher crack densities but only becomes significant for microcracks of aspect ratios approaching 0 3

shear wave polarization anisotropy in the upper mantle beneath honshu japan shear wave polarization anisotropy in the wedge portion of the upper mantle between a subducting plate and the earth s surface is investigated using three component seismograms of intermediate depth and deep earthquakes recorded at 14 local stations in honshu japan eighty nine high quality seismograms were selected from a period of 3 years the data used in this study are restricted such that incidence angles are smaller than the critical angle of 30 to the earth s surface in order to avoid phase shifts in the shear wave train to find directions of the maximum and minimum velocities in split shear waves where shear waves are resolved into two phases with the maximum time separation each set of the two horizontal component seismograms is rotated in the horizontal plane the split shear waves thus obtained are again recombined after the correction of anisotropy and the anisotropy corrected particle motion is compared with the focal mechanism for a cross check of the observed anisotropy directions of the maximum axes are plotted on azimuthincidence angle stereograms at each station the stereograms and the cross sections of seismic ray paths show that 1 the anisotropic material is distributed at intermediate location between earthquake sources and receiving stations and 2 the anisotropic region is separated into two parts one in the north of the present study area with the polarization of the maximum velocity shear wave trending 0 to 30 from the north north anisotropy and the other in the south with it trending 90 to 120 south anisotropy the maximum time delays between the two shear waves along a vertical seismic ray is about l s for both the anisotropic regions the horizontal extent of the anisotropic area in the north is 50 km at depths of 50 to 150 km perhaps prevalent in west honshu however the depth of anisotropic material is not well constrained because of insufficient coverage of seismic ray paths and angles if we assume the vertical extent of the anisotropic material to be 100 km the maximum velocity contrast would be 4 if we adopt a crack alignment model for the observed anisotropy cracks are inferred to be distributed vertically trending 0 to 30 in the north and 90 to 120 in the south if we assume an olivine alignment model olivine crystals are inferred to be aligned in the north with the a axis of the slip direction trending 0 to 30 and the slip plane normal to the b axis being vertical and in the south anisotropy with the axis trending 90 to 120 and the slip plane being horizontal

benthic foraminifera from capbreton canyon revisited faunal evolution after repetitive sediment disturbance abstract at a 650 m deep site in the axis of capbreton canyon an 18 cm thick turbidite was deposited in december 1999 during subsequent campaigns an almost monospecific fauna of the benthic foraminifer technitella melo considered as a pioneer species was found in may 2000 in 2001 this fauna had disappeared and was replaced by an exceptionally rich fauna strongly dominated by the opportunistic species bolivina subaenariensis we present sedimentological radionuclide and foraminiferal data of new cores sampled in 2005 and 2011 taken with the aim to study the further evolution of the benthic ecosystem cores sampled in 2005 show that in the canyon axis a new ca 5 cm thick turbidite has been deposited the live benthic foraminiferal faunas were much poorer than in 2001 but still had a high dominance and low diversity although less extreme than in 2001 we conclude that in the canyon axis benthic foraminiferal faunas remain in an early stage of ecosystem colonization it appears that the very thick 1999 turbidite marks an exceptional event the uncommonly rich faunas observed in 2001 could be a response to the concentration of organic rich material in the fine grained top of this deposit in 2011 cores were sampled at a slightly different site on the lower canyon flank the sedimentary sequence here is marked by the absence of coarse turbidite layers although some levels show slightly increased grain size and lower 210 pb xs activities indicative of an admixture with advected older sediments live foraminiferal faunas are much more equilibrated as shown by their higher diversity lower dominance and deeper penetration into the sediment all these characteristics are indicative of a much more stable ecosystem dead faunas are present throughout the core indicating that the levels with slightly elevated grain size are not typical turbidites resulting from hyperpycnal currents which are characterized by levels barren of foraminifera but denote other more long term sedimentary processes leading to the advection of older material such as bottom nepheloid layers or repetitive fine grained turbidite deposits due to small scale slumping the comparison of live and dead fauna shows that at both sites the foraminiferal turnover rates are fairly low at the lower canyon flank site sampled in 2011 the foraminiferal faunas are renewed every 1 5 2 years such a fairly long foraminiferal lifespan corresponds to earlier estimates but is surprisingly high for the opportunistic taxa that dominate the faunal assemblages in these unstable and food enriched submarine canyon settings

role of internal waves in the generation of nepheloid layers on the northwestern alboran slope implications for continental margin shaping 1 the role of internal waves in the sediment dynamics of the northwestern alboran continental slope was investigated in a selected area around the guadiaro submarine canyon nepheloid layer distribution was identified using closely spaced ctd transmissometer profiles collected during two hydrographic surveys a well defined pattern of suspended sediment distribution consisting of surface intermediate and near bottom nepheloid layers was found intermediate and bottom nepheloid layers were always observed within the canyon and on the adjacent continental slope spanning mainly from 200 to 500 m depth in addition a current meter with a turbidimeter was deployed in the lower section of the guadiaro canyon at 600 m depth 25 meters above the seafloor time series analysis indicated that the currents temperature and turbidity within the canyon fluctuate mainly at semidiurnal tidal frequencies suggesting the presence of semidiurnal internal tides affecting the near bottom suspended sediment concentration along the canyon axis high resolution bathymetry from the study area was used to evaluate the internal wave reflection conditions at semidiurnal tidal frequency for the entire continental slope region critical slope conditions were reached on the upper continental slope and along the canyon axis coinciding with the region in which nepheloid layers were observed this region also coincides with a zone of erosion on the upper continental slope of the study area previously identified by hernandez molina 1993 these results indicate that the generation of intermediate and bottom nepheloid layers as well as the erosion and shaping of the northwestern alboran continental slope may result from the interaction of internal waves and the seafloor morphology

observation of internal tidal currents in the kaoping canyon off southwestern taiwan abstract internal tidal currents and associated water mass displacements were investigated during multiple cruises in the kaoping submarine canyon off southwestern taiwan observations from both moored and shipboard acoustic doppler current profilers and hydrographic casts were conducted along the canyon the velocity data showed that in the lower layer the major axis of the tidal currents aligned with the orientation of the canyon and currents moved up canyon during flood and down canyon during ebb the vertical phase shift and amplitude of the currents indicated that the semidiurnal internal tide dominated with intensity increasing with depth toward the canyon head tidal energy was channeled from the shelf landward with a beamlike internal wave guided by bottom topography the estimated phase velocity was 1 4 1 7 m s 1 based on normal mode analysis and the phase lag between sampling stations empirical orthogonal function analysis of hydrographic profiles confirmed that the first mode m 2 internal tide explained 70 of the total variance the strong convergence of internal tidal currents near the canyon head during flood may play an important role in the daily migration of cherry shrimps which burrow along the canyon wall

accumulation rates of major constituents of hemipelagic sediments in the deep alboran sea a centennial perspective of sedimentary dynamics the accumulation rates of sediment and major constituents in three different geographic areas of the alboran sea have been assessed by means of 210pb and 137cs concentration profiles mixing is present in the top layer of the sedimentary column with mixing coefficients estimated to range from 0 2 to 15 cm2 yr 1 overall apparent sedimentation rates for the last 100 years range from 0 014 to 0 182 g cm 2 yr 1 and show a tendency to decrease with distance to the coast and water column depth however specific characteristics of the sea floor for each physiographic environment govern the actual patterns of sediment accumulation particularly noticeable are the feeding role of submarine canyons the trapping effect of slope terraces and the isolation caused by ridges sediment accumulation induced by turbiditic flows is also observed north of the almeria oran area excess 210pb inventories and surface concentrations reveal a net effect of sediment focussing and point to the role of bottom nepheloid layers in supplying a significant fraction of sediments to the deep areas this is also evidenced by comparison of bottom sediment with the sediment trap data available from the malaga area we estimate that the particle advective input below 30 m above the bottom accounts for as much as 50 70 of the material that is ultimately deposited onto the sea floor the greater abundance of lithogenic material in the malaga zone 80 reflects its larger input in the western alboran sea conversely carbonate contents increase from less than 20 in this area to about 30 in the almeria oran zone reflecting the lesser importance of the dilution by lithogenic components biogenic silica was only detected in some surface samples and no significant preservation was observed below the eh boundary abundance and accumulation rates of organic matter are in accordance with the spatial patterns of primary production in the alboran sea higher in the western part due to the presence of the western alboran gyre however near bottom redistribution leads to the homogenisation of organic matter concentrations in bottom sediments of any given area finally from comparisons with sediment trap data the degradation of organic matter has been estimated to be approximately 30 40 of what reaches the bottom

the effect of a submarine canyon on the river sediment dispersal and inner shelf sediment movements in southern taiwan abstract this study examines the influence of a submarine canyon on the dispersal of sediments discharged by a nearby river and on the sediment movement on the inner shelf the study area includes the head region of the kao ping submarine canyon whose landward terminus is located approximately 1 km seaward from the mouth of the kao ping river in southern taiwan within the study area 143 surficial sediment samples were taken from the seafloor six hydrographic surveys along the axis of the submarine canyon were also conducted over the span of 1 yr three different approaches were used in the analysis of grain size distribution pattern they include 1 a combination of filtering and the empirical orthogonal eigen function eof analysis technique 2 the mclaren model and 3 the transport vector technique the results of the three methods not only agree with one another they also complement one another this study reveals that the kao ping submarine canyon is relatively a stratified and statically stable environment the hydrographic characteristics of the canyon display seasonal variability controlled primarily by the temperature field and the effluent of the kao ping river the hydrographic condition and the bottom topography in the canyon suggest the propagation of internal tides during the flood season summer of the kao ping river the submarine canyon acts as a trap and conduit for mud exchange between the kao ping river and offshore near the head of the canyon there is a region of sediment transport convergence this region is also characterized by high mud abundance on the seafloor that coincides with the presence of high suspended sediment concentration ssc spots in the bottom nepheloid layer outside the submarine canyon on the shelf where the evidence of wave reworking is strong the northwestward alongshore transport dominates over the southeastward transport which is a common theme on the west coast in southern taiwan

finite difference modeling of faults and fractures for the purposes of seismic propagation a slip fault may be regarded as a surface across which the displacement caused by a seismic wave is discontinuous while the stress traction remains continuous the simplest assumption is that this slip and the stress traction are linearly related such a linear slip interface condition is easily modeled when the fault is parallel to the finite difference grid but is more difficult to do for arbitrary nonplanar fault surfaces to handle such situations we introduce equivalent medium theory to model material behavior in the cells of the finite difference grid intersected by the fault virtually identical results were obtained from modeling the fault by 1 an explicit slip interface condition fault parallel to the grid and 2 using the equivalent medium theory when the finite difference grid was rotated relative to the fault and receiver array no additional computation time is needed except for the preprocessing required to find the relevant cells and their associated moduli the formulation is sufficiently general to include faults in and between arbitrary anisotropic materials with slip properties that vary as a function of position

tidal influence on suspended sediment distribution and dispersal in the northern andaman sea and gulf of martaban abstract surface and water column profiles of suspended matter collected during april may 2002 and satellite images were used to study factors influencing suspended sediment concentrations sscs and dispersal in the northern andaman sea and gulf of martaban one of the largest highly turbid areas of the world s oceans perennial high ssc in the gulf of martaban is due to a combination of factors including resuspension of sediments by strong tidal currents shallow bathymetry and seasonal sediment influx from rivers from satellite images it was observed that in the central portion of the gulf of martaban the turbidity front oscillates about 150 km in phase with spring neap tidal cycles and the area covered by the turbid zone ssc 15 mg l 1 increases from less than 15 000 km2 during neap tide to more than 45 000 km2 during spring tide the sediment discharged by the ayeyarwady river is transported mainly eastward along the coast into the gulf of martaban occasionally during the winter monsoon period sediment plumes are seen heading westward into the bay of bengal turbidity profiles show that bottom nepheloid layers are actively transporting some of the sediments into the deep andaman sea via the martaban canyon

neoproterozoic to early cambrian history of an active plate margin in the tepla barrandian unit a correlation of u pb isotopic dilution tims ages bohemia czech republic abstract the tepla barrandian unit tbu of the bohemian massif shared a common geological history throughout the neoproterozoic and cambrian with the avalonian cadomian terranes the neoproterozoic evolution of an active plate margin in the tepla barrandian is similar to avalonian rocks in newfoundland whereas the cambrian transtension and related calc alkaline plutons are reminiscent of the cadomian ossa morena zone and the armorican massif in western europe the neoproterozoic evolution of the tepla barrandian unit fits well with that of the lausitz area saxothuringian unit but is significantly distinct from the history of the moravo silesian unit the oldest volcanic activity in the bohemian massif is dated at 609 17 19 ma u pb upper intercept subduction related volcanic rocks have been dated from 585 7 to 568 3 ma lower intercept rhyolite boulders which pre dates the age of sedimentation of the cadomian flysch st chovice group accretion uplift and erosion of the volcanic arc is documented by the neoproterozoic dob is conglomerate of the upper part of the flysch the intrusion age of 541 7 8 ma from the zgorzelec granodiorite is interpreted as a minimum age of the neoproterozoic sequence the neoproterozoic crust was tilted and subsequently early cambrian intrusions dated at 522 2 ma t sovice granite 524 3 ma vsepadly granodiorite 523 3 ma smr ovice tonalite 523 1 ma smr ovice gabbro and 524 0 8 ma orlovice gabbro were emplaced into transtensive shear zones

early palaeozoic acid magmatism in the saxothuringian belt new insights from a geochemical and isotopic study of orthogneisses and metavolcanic rocks from the fichtelgebirge se germany rocks range from 316 to 298 ma for muscovites and from 306 to orthogneisses and acid metavolcanic rocks from the fichtelgebirge 280 ma for biotites demonstrating thermal influences from late ne bavaria germany are predominantly chemically evolved monvisean to late stephanian 325 290 ma granite intrusions the zo granites and rhyodacites dacites respectively the metavolcanic involvement of dominantly crustal derived melts is considered to rocks are variably tectonized and include samples with anomalously account for the peraluminous character a cnk 1 08 high low cao na2o and mno 80 initial sr sr 0 709 and negative end 500 ma 2 9 to 6 4 wt and k2o 6 wt concentrations implying selective of the intrusive and volcanic rocks the generation of the melts is element mobility during post eruptive events sm nd isotope data assumed to have taken place within an overall extensional geodynamic for samples from three main orthogneiss units wunsiedel selb setting the wider range in end 500 ma for the metavolcanic rocks waldershof yield a composite sm nd whole rock isochron cor 3 8 to 6 4 orthogneisses 2 9 to 4 0 suggests that differential responding to an age of 560 45 ma this age estimate is admixture of a pelagic sedimentary component during emplacement constrained however to be less than 560 ma by the presence of may have occurred nd model ages range from 1 5 to 1 7 ga and detrital cadomian zircons in the country rocks fifteen specimens are consistent with those of granitoids from the erzgebirge and the from the wunsiedel orthogneiss give an rb sr whole rock isochron lausitz but completely different from those of metavolcanic rocks of 480 4 ma with an initial sr sr ratio of 0 7095 from the thuringer wald in addition nd model ages of the early 0 0007 mswd 2 7 rb sr isotope data from the walpalaeozoic granitoids in the fichtelgebirge are consistent with those dershof orthogneiss and the metavolcanic rocks suggest however of the late carboniferous granitoids from the same area this that in general sr isotopic equilibrium if ever reached was suggests similar source material for the pre variscan and the late significantly modified during later events taking recent geovariscan fichtelgebirge granitoids chronological literature data into account it now appears that early palaeozoic acid magmatism in the fichtelgebirge commenced with the intrusion of the orthogneiss precursors during the early and mid ordovician and ended with the eruption of the volcanic

near bottom suspended sediment variability caused by storms and near inertial internal waves on the ebro mid continental shelf nw mediterranean abstract near bottom currents and suspended sediment concentrations ssc recorded on the ebro continental shelf at 60 m depth during the transition between fair and stormy weather have revealed some of the major processes controlling the sediment re suspension and transport at mid shelf depths in this nw mediterranean area storm waves were the main contributor to the transport of sediment although they only resuspended surface sediments during extreme wave conditions h s 4 5 m and t s 11 s during the recording period the net suspended sediment flux along the shelf was one order of magnitude higher than the net suspended sediment flux across the shelf and the resultant transport was towards the sw and seaward fluctuations of the near bottom ssc during fair weather showed a periodicity around 17 h and were related to the occurrence of near inertial internal waves caused by wind pulses during storm events the energy propagation of these internal waves reached critical angles at the mid and outer shelf which could favor the development and maintenance of the bottom nepheloid layer on the ebro continental shelf as well as on other mediterranean continental shelves

internal tides in monterey submarine canyon abstract the m2 internal tide in monterey submarine canyon is simulated using a modified version of the princeton ocean model most of the internal tide energy entering the canyon is generated to the south on sur slope and at the head of carmel canyon the internal tide is topographically steered around the large canyon meanders depth integrated baroclinic energy fluxes are up canyon and largest near the canyon axis up to 1 5 kw m 1 at the mouth of the upper canyon and increasing to over 4 kw m 1 around monterey and san gregorio meanders the up canyon energy flux is bottom intensified suggesting that topographic focusing occurs net along canyon energy flux decreases almost monotonically from 9 mw at the canyon mouth to 1 mw at gooseneck meander implying that high levels of internal tide dissipation occur the depth integrated energy flux across the 200 m isobath is order 10 w m 1 along the majority of the canyon rim but increases by over an order of magnitude near the canyon head where internal ti

ammonium concentration and nitrogen isotope composition in metasedimentary rocks from different tectonometamorphic units of the european variscan belt the content and isotopic composition of ammonium nh4 were measured by using kjeldahl distillation for 63 samples of predominantly metasedimentary rocks from two different geological settings of the european variscides i e the erzgebirge and the zone of erbendorf vohenstrauss in germany the studied erzgebirge schists represent an early paleozoic passive margin sequence that reappears in different deep subducted metamorphic units this allows an efficient examination of nitrogen loss and isotope fractionation during prograde metamorphism ammonium is found to be progressively depleted accompanied by a shift in 15n from the low grade units 2 kbar 300 c with 638 124 ppm and 15n 2 2 0 6 to the garnet phyllite unit 9 kbar 470 c with 621 190 ppm and 15n 3 5 0 9 the mica schist eclogite unit 12 kbar 550 c with 394 113 ppm and 15n 3 9 0 8 and to the gneiss eclogite unit 12 kbar 730 c with 99 32 ppm and 15n 7 7 2 0 using equilibrium models for rayleigh distillation and batch volatilization suggest that the nitrogen depletion took place by ammonia release only for the mica schists this isotope fractionation can be explained by the loss of molecular nitrogen in comparison with the early paleozoic schists the proterozoic ortho and paragneisses of the erzgebirge gneiss unit 6 8 kbar 650 c contain significantly lower amounts of ammonium 70 ppm and reach relatively low 15n values 2 5 to 3 6 the paragneisses from the zone of erbendorf vohenstrauss zev sampled from the ktb pilot hole represents a separate tectonometamorphic unit that has undergone polyphase metamorphic conditions with the major imprint being amphibolite facies 7 kbar 650 700 c the metagraywackes have nh4 contents of 80 ppm and 15n of approximately 6 gneisses in the vicinity of a late cataclastic shear zone at 2000 m depth are characterized by a shift in nh4 250 ppm and 15n up to 12 which suggest late fluid rock interactions with a nitrogen and 15n enriched fluid

from the highest to the deepest the gaoping river gaoping submarine canyon dispersal system abstract there are many different source to sink dispersal systems around the world and the gaoping river gpr gaoping submarine canyon gpsc provides an example especially as a canyon captured system the gpr a small mountainous river having an average gradient of 1 150 and the gpsc which links the river catchment to the deep sea basin represent two major topographic features around sw taiwan together they constitute a terrestrial to marine dispersal system that has an overriding impact on the source to sink transport of sediment in this region the gpsc extents from the mouth of the gpr through the shelf and slope and into the northeastern manila trench a distance of about 260 km it is a major conduit for the transport of terrestrial sediment and carbon to the south china sea and the landward transport of particles of marine and biological origin in the gpsc the dominant mode of suspended sediment transport is tidal oscillations and the net direction is up canyon in contrast sediment transport associated with episodic gravity driven events is down canyon the steady sedimentation of the tidal regime results in hemipelagic mud across the canyon floor whereas the gravity driven hyperpycnal regime causes turbidite erosion and deposition along the canyon thalweg typhoon induced river floods often lead to hyperpycnal plumes at the river mouth which directly and indirectly ignite hyperpycnal turbidity currents in the canyon forming an effective agent for transporting large amounts of terrestrial organic material modern and fossil carbon to the south china sea basin therefore the gpr gpsc represents a source to sink system in which terrestrial sediment in a mountainous catchment is promptly removed and transported to the deep sea by episodic gravity flows this is also a pathway by which modern terrestrial organic carbon is quickly and effectively delivered to the deep sea

review of nd isotopic data and xenocrystic and detrital zircon ages from the pre variscan basement in the eastern bohemian massif speculations on palinspastic reconstructions

the hammerlein skarn hosted polymetallic deposit and the eibenstock granite associated greisen western erzgebirge germany two phases of mineralization two sn sources the hammerlein polymetallic deposit is hosted in skarn schists and gneisses that reached their metamorphic peak at 340 ma during the variscan orogeny the deposit is spatially closely associated with one of the most voluminous granites of the erzgebirge the eibenstock granite which intruded the metamorphic units at 320 ma and locally also developed greisen mineralization cassiterite is the main ore mineral in the hammerlein skarn and in greisen mineralizations associated with the eibenstock granite the age of skarn formation is bracketed by multi mineral rb sr isochron ages of the gneisses 340 ma and the end of ductile deformation 330 ma the dated calc silicate minerals of the skarn have elevated sn contents which implies that some sn was present in the system during regional metamorphism i e well before the emplacement of the eibenstock granite tin in the 330 ma old skarn silicates possibly was mobilized from the metamorphic wall rocks retrogression of the skarn mineral assemblage may have released some sn that formed cassiterite in an assemblage with chlorite and fluorite the sr isotope signatures of fluorite indicate that this late assemblage is not related to cooling of the metamorphic rocks but to the emplacement of the eibenstock granite which introduced additional sn into the skarn thus mineralization in the hammerlein deposit includes sn that was introduced during two different events from different sources

pressure temperature and fluid evolution of quartzo feldspathic metamorphic rocks with a relic high pressure granulite facies history from the central erzgebirge saxony germany by 1 high pressure hp equilibration followed by near isothermal the gneiss eclogite unit is a composite tectonometamorphic unit decompression at high temperatures during which rocks from different within the variscan erzgebirge mega antiform it comprises migdepths were amalgamated and 2 extensive hydration and rematitic paraand orthogneisses high temperature ht mylonites equilibration at medium pressures followed by rapid cooling during kyanite bearing granulites eclogites and garnet peridotites four continued uplift when the entire unit came into contact with cooler different quartzo feldspathic assemblages are recognized in which now overand underlying units this scenario is attributed to maximum conditions of up to 830 c and 21 kbar were determined continent collision orogenic collapse and disintegration of the hp the assemblages are characterized by the nearly complete prograde unit during continuing collision crustal stacking and uplift controlled breakdown of biotite by high grossular content 23 47 mol by extension of garnet in the presence of albite and high si contents of phengite 3 3 3 4 per formula unit p f u water activities at this stage are variable and range from 0 4 the maximum pressures indicated for individual rock volumes may vary considerably between 12 and 24 kbar at 700 800 c so that non coherency

on the links between a river s hyperpycnal plume and marine benthic nepheloid layer in the wake of a typhoon abstract in 2010 two moorings each configured with a ctd and an adcp one with an additional non sequential sediment trap nsst were deployed in the head region of the gaoping submarine canyon 3 days after the typhoon induced peaks of the runoff and suspended sediment concentration ssc of the gaoping river in southern taiwan our data show a demarcation between tidal and hyperpycnal regimes in the temperature salinity and flow fields the latter existed in the first 5 days out of the 18 day deployment as defined by higher water density due to high ssc several lines of evidence indicate the presence of the tail end of a hyperpycnal turbidity current htc including the retention of warm water near the canyon floor high ssc down canyon directed residual flow and its vertical structure and high terrestrial fraction larger than 70 of the organic particles carried by the flow the decreasing mass flux during the deployment is also an indication of a waning htc our findings also show that the vertical flow structure and the direction of the gravity driven down canyon htc were retarded by the instantaneous up canyon directed tidal oscillations in the submarine canyon

shear wave splitting beneath western united states in relation to plate tectonics we have examined shear wave splitting in teleseismic shear waves from 26 broadband stations in the western united states fast polarization directions and delay times t show spatial variations that are coherent within geologic provinces stations located near the san andreas fault show clear evidence for fault parallel anisotropy in the crust and upper mantle 115 125 km thickness this can be explained by the finite strain associated with the relative plate motion between the north american and pacific plates the lateral extent of this strain field is probably narrow to the west because stations 55 km west of the san andreas fault do not show fault parallel anisotropy in southern california station lac located 80 km east of the san andreas fault shows large fault parallel anisotropy this suggests that the pacific north american plate boundary in the mantle might be displaced to the east in southern california a deeper e w oriented fast direction of anisotropy underlies the fault parallel anisotropic layer in the vicinity of the san andreas fault an e w fast feature is also present beneath the western basin and range and the foothills of the sierra nevada although local variations are present the magnitude of delay times suggests that this feature resides in the asthenosphere we interpret this feature as the asthenospheric flow in the slabless window left behind the farallon plate the flow induced anisotropy may partially be frozen in at shallow depths station orv is located near the southern edge of the gorda slab where no anisotropy is detected the absence of anisotropy at this location could therefore mark a boundary between farallon associated flow and regions where e w oriented asthenospheric flow did not occur the lack of evidence for ne sw fast orientation within the walker lane shear belt of western nevada suggests that this crustal feature does not extend into the mantle or that is not as well developed as that beneath the san andreas fault stations located over the young subducting gorda plate mark a change in the fast direction to nearly ne sw this direction aligns well with the maximum compressive stress direction in the overlying north american plate and the ne sw directed internal shearing of the gorda plate the anisotropic thicknesses calculated from delay times suggest roughly double that expected for purely lithospheric contributions this implies that the anisotropic thickness may include some of the asthenosphere alternatively using a higher anisotropy of 8 can bring thicknesses in line with other measures of lithospheric thicknesses the correspondence between the fast directions and the present plate tectonic deformations suggest that mapping upper mantle deformation through seismic anisotropy is a viable method and that asthenospheric flow may be a significant contributor to seismic anisotropy

discrimination of protolithic versus metamorphic zircon ages in eclogites constraints from the erzgebirge metamorphic core complex germany abstract protolithic ages of meta basites are crucial for tectonic reconstructions as they constrain the lifetime of oceans however in high grade metamorphic regions most isotope systems record metamorphic ages due to the metamorphic overprint the mineral zircon is the most suitable geochronometer for the determination of protolithic ages in such rocks due to its high closure temperature zircon from eclogites from the eastern erzgebirge metamorphic complex yielded both protolithic 540 ma 5 samples and metamorphic 340 ma 4 samples 207 pb 206 pb ages detailed investigations of zircon grains within thin rock sections show that the metamorphic ages are related to new zircon growth caused by water infiltration that triggered decomposition of omphacite into an amphibole plagioclase symplectite rutile and apatite frequently grew together with metamorphic zircons indicating local mobilization of zr nb lree and p eclogites with omphacite breakdown are very dark in colour in difference lighter coloured eclogites contain k feldspar and quartz indicating minor melt infiltration that caused breakdown of garnet and transformation of amphibole into biotite this supports additional new growth of zircon grains in some samples idiomorphic zircon grains with a lot of micro inclusions indicate a coupled dissolution reprecipitation process additional rounded resorbed and highly fractured zircon grains together with internal zircon textures imply multiple melt infiltration triggering multiple phases of zircon growth therefore scattering zircon ages may reflect multiple growth stages or inheritance rather than prolonged periods of metamorphic growth in contrast protolithic zircon ages were found in eclogites where no water or melt infiltration occurred this emphasizes the importance of water and or melt infiltration for the new growth of zircon grains in eclogites as was already shown for granulites in various studies in the eastern erzgebirge most eclogites and amphibolites were derived from morb type or arc related basalts while the plagioclase rich amphibolites formed mainly from crustal sources the protolith ages of meta basites from the eastern erzgebirge 540 ma document a bimodal magmatic activity in a cadomian back arc basin

winter dynamics on the northern portuguese shelf part 2 bottom boundary layers and sediment dispersal abstract the northern portuguese shelf between 41 n and 42 n is characterised by the presence of a mid shelf mud deposit the douro mud patch dmp observations conducted between july 1996 and june 1999 under the framework of project omex ii ii are used to examine the impact of the dynamic processes in the lower water column particularly on the dmp the typical wave conditions observed during the winter maintain a highly energetic environment capable of promoting the erosion of fine sediments at mid shelf depths however the bottom nepheloid layers generated beneath these waves only extend a few meters above the bottom and are contained within rocky outcrops with similar heights that fringe the outer shelf each year there are about ten storms mostly associated with southerly winds that create downwelling conditions over the shelf the waves associated with these storms produce shear velocities over 3 cm s at mid shelf and bottom nepheloid layers which extend a few tens of meters above the bottom and spread offshore over the outer shelf and upper slope a rough estimate suggests that these events account for an offshore export of about 20 10 6 kg of fine sediments each year equivalent to 1 2 of sediments trapped at dmp

eclogites from the czech part of the erzgebirge multi stage metamorphic and structural evolution a structural and petrological study of saxothuringian eclogites in the central erzgebirge czech republic revealed their polyphase thermal and tectonic evolution the first stage of deformation is related to eclogite facies metamorphism of mafic rocks at pressures of 26 kbar and temperatures of 650 700 c the clinopyroxene crystallographic preferred orientation is consistent with high temperature flow the second stage of deformation is characterized by transport of eclogitic rocks at the base of a crustal nappe and their large scale folding during this stage hp ht metamorphic assemblages developed in the surrounding metapelites 14 5 kbar 600 c while eclogite assemblages were preserved in passively transported eclogitic boudins heat advection and similar p t conditions in the surrounding crustal material are responsible for the stability of mineral assemblages and preclude closure of isotopic systems in the eclogites therefore the published isotopic ages of the eclogites do not reflect the subduction stage but the age of cooling under crustal conditions subsequent large scale d3 folding is responsible for reorientation of previously flat lying earlier fabrics d1 d2 the final stage of deformation is marked by the development of a heterogeneous network of ductile retrograde shear zones the thermometry and geochemical study of amphibolitized eclogites in the cores of shear zones indicates thermal conditions not exceeding those in surrounding metapelites and fluid influx the fluid influx is interpreted to be the result of water producing prograde reactions in the footwall metasediments and fluid chanelling into the base of the nappe during brittle deformation of the eclogites