weakening associated with the diaspore corundum dehydration reaction in metabauxites an example from naxos greece abstract metabauxite lenses embedded in marble on naxos consist of diasporites below the 420 c isograd and dehydrate into corundum rich rocks with increasing grades of metamorphism while the diasporites are essentially undeformed the corundum rich rocks are strongly deformed even though both diasporites and corundum rich rocks are much stronger than the surrounding intensely deformed marbles the observed structures can be explained as an effect of high fluid pressures during the prograde diaspore corundum dehydration reaction which causes dramatic temporary weakening of the metabauxites to a strength comparable to that of the surrounding deforming marbles deformation of the metabauxite is thus largely restricted to the time span the phase transformation occurred allowing the dehydrating bauxite mass to deform together with the surrounding marbles

depositional history of quaternary sediments on the continental shelf off the southeastern coast of korea korea strait abstract the depositional history of quaternary sediments on the continental shelf off the southeastern coast of korea korea strait was investigated by means of analysing high resolution seismic profiles and sediment samples quaternary sediments up to 50 m thick overlie the irregular surface of the acoustic basement in the inner shelf the sedimentary column is comprised of two main sequences separated by a mid reflector which is interpreted as the pre holocene surface the holocene sequence reaching up to 30 m in thickness with a depocenter near the present river mouth is characterized by deposition in a prodelta environment while the upper pleistocene sequence represents deposition in deltaic or shallow water environments during the late glacial period most of the shelf was subaerially eroded and deposition took place only in the trough region the present location of marine built terraces indicates that the lowest position of sea level was about 130 m below its present level the subsequent postglacial transgression reworked pleistocene sediments to form a thin veneer of transgressive facies sea level rose rapidly in the early stages of the postglacial transgression and approached the present level at approximately 7000 5000 yrs b p recent sedimentation the holocene sequence probably began at that time

metamorphic evolution of the attic cycladic metamorphic belt on naxos cyclades greece utilizing 40ar 39ar age spectrum measurements 40ar 39ar age spectrum analysis of phengite separates from naxos part of the attic cycladic metamorphic belt in greece indicates that cooling following high pressure low to medium temperature metamorphism m1 occurred about 50 ma ago phengite has 40ar gradients that suggest that part of the scatter observed in conventional k ar ages was caused by diffusion of radiogenic argon from the minerals during a younger metamorphism m2 in central naxos this metamorphism m2 has overprinted the original mineral assemblages completely and is associated with development of a thermal dome excellent 40ar 39ar plateaus at 15 0 0 1 ma 11 8 0 1 ma and 11 4 0 1 ma obtained on hornblende muscovite and biotite respectively from the migmatite zone indicate that relatively rapid cooling followed the m2 event and that no significant thermal overprinting occurred subsequent to m2 toward lower m2 metamorphic grade 40ar 39ar plateau ages of hornblendes increase to 19 8 0 1 ma concomitantly the proportion of excess 40ar in the spectra increases as well we propose that the peak of m2 metamorphism occurred beween 15 0 and 19 8 ma ago k ar ages of biotites from a granodiorite on the west coast are indistinguishable from those found in the metamorphic complex and hornblende k ar ages from the same samples are in the range 12 1 13 6 ma as the latter ages are somewhat younger than most ages obtained from the metamorphic complex intrusion of the granodiorite most likely followed the peak of the m2 metamorphism the metamorphic evolution of naxos is consistent with rapid crustal thickening during the cretaceous or early tertiary causing conditions at which supracrustal rocks experienced pressures in the range 900 1500 mpa transition to normal crustal thicknesses ended the m1 metamorphism about 50 ma ago the m2 metamorphism and granodiorite intrusion occurred during a period of heat input into the crust possibly related to the migration of the hellenic volcanic ar c in a southerly direction through the area

the interaction between aegean back arc extension and anatolia escape since middle miocene the aegean domain is a key area for understanding the processes of back arc extension observed deformation pattern and present day kinematics result from the interaction between the southward retreat of the hellenic trench and the westward escape of anatolia lithosphere scale analogue models were employed to display that the overall pattern of aegean extension requires not only the combination of trench retreat and anatolia escape since middle miocene but also the presence of an inherited lithosphere scale mechanical discontinuity the vardar suture zone vsz the reactivation in dextral shear of the eastern branch of the vsz accommodates both the trench retreat ns stretching and the westward escape of anatolia ew shortening in the cyclades area since middle miocene additionally our model shows that the north anatolian fault naf is a late structure in the evolution of the aegean initiated around 10 ma after the onset of anatolia escape the displacement field at the surface of the model allows the identification of sub domains which result from strain partitioning instead of being rigid microplates directly comparable to the present day displacement field gps of the aegean and western anatolia our model provides a simple but powerful way to look at the dynamics of aegean extension in two main stages from middle eocene to middle miocene extension was only driven by the southward retreat of the hellenic trench at a rate lower than 1 cm y 1 since middle miocene the combination of slab rollback with anatolia westward escape resulted in a southwest direction of trench retreat with an accelerating rate of up to 3 cm y 1

tectono metamorphic evolution of syros and sifnos islands cyclades greece abstract miocene exhumation of metamorphic rocks in the aegean sea is partly a consequence of post orogenic extension if the post orogenic mechanism of exhumation is rather well understood the earlier syn orogenic eocene exhumation is still largely enigmatic previous authors have argued in terms of extension or compression new structural and petrological data on sifnos and syros islands show that exhumation of high pressure low temperature hp lt rocks involves crustal scale extensional ductile shear zones during the eocene we observe a continuum of top to the ne and e ductile shear from the eocene in the blueschist facies to the miocene in the greenschist facies this deformation is distributed in the eclogites and blueschists whereas it is rather localised along ductile shear zones in the greenschists eclogites which are preserved only at the top of the structural pile are exhumed with a cold retrograde p t path in the lower part of the structural pile we observe a progressive retrogression of eclogites in blueschist then greenschist facies this lower part of pile is subsequently exhumed with p t paths showing a nearly isothermal decompression before cooling p t t deformation data suggest that the cycladic blueschists are progressively exhumed by a continuum of accretion at the base of the orogenic wedge and by a partly non coaxial extensional deformation above distributed during the syn orogenic stage then localised during the post orogenic stage we then compare the mechanism of syn orogenic exhumation of crete and the cyclades and we discuss a simple geodynamic scenario for the aegean domain and the external hellenides which accounts for 1 the southward migration of the hellenic trench and arc during the cenozoic 2 the p t t deformation data for the cycladic blueschists and the phyllite quartzite nappe and 3 the transition from syn orogenic to post orogenic in the cyclades

partitioning and budget of li be and b in high pressure metamorphic rocks abstract partitioning and budget of li be and b in high pressure metamorphic rocks from the island of syros greece were studied using secondary ion mass spectrometry inductively coupled plasma optical emission spectrometry and prompt gamma neutron activation analysis partitioning between coexisting mineral phases was found to be rather constant and independent of element concentrations for several mineral pairs apparent partition coefficients vary in a narrow range while concentrations vary by more than an order of magnitude hence it was possible to establish sets of inter mineral partition coefficients for li be and b among 15 different high pressure minerals this data set provides important information on the behaviour of the light elements in different lithologies within subducting slabs from the onset of metamorphism to the eclogite stage it is essential for modelling trace element and isotope fractionation during subduction and dehydration of oceanic crust

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

geochronological challenges posed by continuously developing tectonometamorphic systems insights from rb sr mica ages from the cycladic blueschist belt syros greece is metamorphism and its causative tectonics best viewed as a series of punctuated events or as a continuum this question is addressed through examination of the timing of exhumation of the cycladic blueschist belt the cause of scatter beyond analytical error in rb sr geochronology was investigated using a suite of 39 phengite samples rb sr ages have been measured on phengite microsamples drilled from specific microstructures in thin sections of calcschists and metabasites from the cycladic blueschist belt on syros the majority are from samples that have well preserved blueschist facies mineral assemblages with limited greenschist facies overprint the peak metamorphic temperatures involved are below the closure temperature for white mica so that crystallization ages are expected to be preserved this is supported by the coexistence of different ages in microstructures of different relative age in one sample phengite from the dominant extensional blueschist facies fabric preserves an age of 35 ma while post tectonic mica millimetres away has an age of 26 ma the results suggest that micro sampling techniques linked to detailed microstructural analysis are critical to understanding the timing and duration of deformation in tectono metamorphic systems north of the serpentinite belt in northern syros phengite rb sr ages are generally between 53 and 46 ma comparable to previous dates from this area south of the serpentinite belt phengite in blueschist facies assemblages associated with extensional fabrics linked to exhumation have ages that range from 42 ma down to c 30 ma indicating that extensional deformation while still under blueschist facies conditions continued until 30 ma no age measurements on samples with unambiguous evidence of deformation under greenschist facies conditions were made two rocks with greenschist facies assemblages gave phengite ages that overlap with the younger blueschist samples suggesting blueschist facies phengite is preserved in these rocks two samples yielded ages below 27 ma one is from a post tectonic microstructure the other from a greenschist in which the fabric developed during earlier blueschist facies conditions these ages are consistent with previous evidence of greenschist facies conditions from c 25 ma onwards the data are consistent with a model of deformation that is continuous on a regional scale this article is protected by copyright all rights reserved

tectonics of the syros blueschists cyclades greece from subduction to aegean extension 1 on syros high pressure metamorphism affects a lithological pile that is composed of from base to top 1 the komito vari granitic basement 2 a margin sedimentary sequence that is predominantly made of marbles and schists the pyrgos and kastri units and 3 the kambos metaophiolitic melange the tectonic history occurred in three main stages during the first stage in the mid eocene the kambos oceanic unit was thrust southward on top of the sedimentary pile top to the south southwest ductile senses of shear are synchronous with prograde high pressure metamorphism and associated with this thrusting event the second stage corresponds to a top to the northeast ductile shear that affects the whole metamorphic pile and is synchronous with the metamorphic retrogression from eclogite to greenschist facies however the kambos oceanic unit remained partly undeformed as shown by significant volumes containing undeformed lawsonite pseudomorphs no major extensional detachment related to this exhumation event outcrops on the island the localized semibrittle to brittle deformation of the third stage is associated with the postmetamorphic development of 1 a ramp flat extensional system at the island scale whose southward minimum displacement is estimated at approximately 7 km and 2 two sets of steeply dipping strike slip faults with a normal component trending either east west or around north south indicating that the mean stretching and shortening directions are trending nne ssw and ese wnw respectively this sequence of major tectonic events and their relationship to metamorphism are interpreted within the framework of the subduction of the pindos ocean and then of the adria continental passive margin

sediment distribution dispersal and budget in the yellow sea abstract information on the surface sediment distribution in the yellow sea is newly compiled based on all available data produced by chinese and korean workers and is used to refine the dispersal patterns and budget of sediments derived from the adjoining landmass the central yellow sea is largely covered with fine grained sediments originating from the huanghe river 2 2 10 8 t yr about 20 of the total discharge thick sediment accumulation exceeding 5 mm yr occurs in the gulf of bohai and around the shandong peninsula about two thirds of the total huanghe river discharge the old huanghe delta suffers from reworking by strong tides and waves and forms a mud patch southwest of cheju island accumulation rate 2 10 7 t yr more than half of the sediments derived from the changjiang river are deposited along the coast of the east china sea the remainder accumulate on the inner shelf off the river mouth in the southeastern yellow sea the keum river dominates sediment discharge forming a holocene mud belt along the southwestern coast of korea accumulation rate 5 10 6 t yr turbid water plumes occur nearshore throughout the year and their suspended sediments are transported along the tip of the peninsula to the western coastal embayments in the south sea the nakdong river discharge of 1 10 7 t yr is responsible for the eastern nearshore mud of the south sea relict sands occur in the northern part of the yellow sea in the northern east china sea and in the korea strait

distribution of suspended sediment in the korea strait and southeastern yellow sea onset of winter monsoons abstract high energy conditions in the yellow sea begin each year with the onset of monsoon winds in late october these transitional season surges of cold air initiate sediment resuspension vertical mixing of suspended sediments and a wind driven coastal current that flows to the south during the summer to winter transition suspended sediment concentrations in the southeastern yellow sea range from 5 100 mg l 1 at the surface and 5 500 mg l 1 at the bottom the highest concentrations occur off the southwest tip of the korean peninsula and the lowest occur in the central part of the korea strait the rate of transitional season destratification may depend on the timing and intensity of monsoonal surges whereas a late onset of monsoon winds allows waters to remain longer in their moderately stratified summer condition an early onset of monsoon winds tends to destratify the water column by mid november resulting in a nearly uniform high concentration of suspended sediments from surface to bottom the band of more turbid coastal water ends abruptly 25 50 km offshore as a turbidity front in waters 20 80 m deep a wind driven residual flow to the south appears to transport large volumes of this turbid water into the korea strait and perhaps as far as the sea of japan

m2 internal tides and their observed wavenumber spectra from satellite altimetry abstracta near global chart of surface elevations associated with the stationary m2 internal tide is empirically constructed from multimission satellite altimeter data an advantage of a strictly empirical mapping approach is that results are independent of assumptions about ocean wave dynamics and in fact can be used to test such assumptions a disadvantage is that present day altimeter coverage is only marginally adequate to support mapping such short wavelength features moreover predominantly north south ground track orientations and contamination from nontidal oceanographic variability can lead to deficiencies in mapped tides independent data from cryosphere satellite 2 cryosat 2 and other altimeters are used to test the solutions and show positive reduction in variance except in regions of large mesoscale variability the tidal fields are subjected to two dimensional wavenumber spectral analysis which allows for the construction of an empirical map of modal wavelengths mode 1 wavelengths sho

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

patterns of folding within nappes and thrust sheets examples from the variscan of southwest england folding is a common response to deformation within nappes and thrust sheets and a wide variety of attitudes of folds can result two examples of patterns of variably oriented folds from southwest england are analysed in terms of thrust tectonics in northern cornwall the millook nappe contains a downward progression from upright to recumbent folding with a zone of oblique or sheath folds at its base these changes are related to an increasing simple shear component towards the base of the nappe in southwestern cornwall d1 and d2 deformations are related to the thrust emplacement of the lizard complex f1 folds in rocks below and to the north of the lizard complex have variable axial orientations alternating zones of folds trending normal and oblique to the transport direction have been mapped the oblique folds are interpreted as initiating in zones of differential movement within thrust sheets later d2 shear zones cut up section ahead of the advancing lizard complex in which case they result in refolding of f1 folds beneath the lizard complex these d2 shear zones cut down section extending but rarely refolding the d1 structures

ductile thrusting within subduction complex rocks on signy island south orkney islands abstract a model involving repeated nnw directed ductile thrusting in subduction complex rocks on signy island south orkney islands accounts for the consistent nnw trending alignment of fold axes stretching and shearing directions in the absence of major discrete thrust planes stratigraphic control or younging criteria the evidence for consistent ductile thrusting is more cryptic and is found in folding stretching relations porphyroblast rotations and mylonite fabrics early fold axes parallel to stretching syn tectonic garnet rotations augen lineations and sheath folds all support nnw directed thrusting as do a common late shear band foliation and minor shear zones development of late open folds with axes parallel to stretching may be due to constrictional deformation a lateral ramp or differential movement during thrusting the structures described from signy island may characterize the type of deformation in deep level ductile thrust zones at the base of an accretionary wedge or in a zone of subcretion the thrusting direction on signy island is inferred to be parallel to the direction of subduction in the south orkney islands in the early jurassic plate reconstructions suggest that this direction was at a high angle to the arcuate trend of the antarctic peninsula continental margin

3d geometrical modelling of post foliation deformations in metamorphic terrains syros cyclades greece superposed to ductile syn metamorphic deformations post foliation deformations affect metamorphic units during their exhumation understanding the role of such deformations in the structuration of metamorphic units is key for understanding the tectonic evolution of convergence zones we characterize post foliations deformations using 3d modelling which is a first order tool to describe complex geological structures but a challenging task where based only on surface data we propose a modelling procedure that combines fast draft models interpolation of orientation data with more complex ones where the structural context is better understood implicit modelling allowing us to build a 3d geometrical model of syros island blueschists cyclades based on field data with our approach the 3d model is able to capture the complex present day geometry of the island mainly controlled by the su perposition of three types of post metamorphic deformations affecting the original metamorphic pile i a top to south ramp flat extensional system that dominates the overall island structure ii large scale folding of the metamorphic units associated with ramp flat extensional system and iii steeply dipping normal faults trending dominantly nnw sse and ew the 3d surfaces produced by this method match outcrop data are geologically consistent and provide reasonable estimates of geological structures in poorly constrained areas

arcuate lineation trends in a deep level ductile thrust belt syros greece abstract the metamorphic rocks of blueschist facies on the aegean island of syros show structures which indicate deformation in a ductile thrust zone at 40 50 km depth the associated dominant linear fabric shows systematic variations in orientation across the island tracing out a series of arcuate patterns on various scales differing microstructural development along these lineation arcs suggests that they are the result of localized and variable superimposed wrench shears in the overall thrust regime the angular relations of these microstructures show a close correspondence with those predicted theoretically from the superimposition of thrust and wrench shears and a possible irrotational component

transgressive sand ridges on the mid shelf of the southern sea of korea korea strait formation and development in high energy environments abstract the mid shelf of the southern sea of korea korea strait is covered by a series of shore parallel sand ridges up to 63 km long 3 9 km wide and 22 m thick the ridges are a moribund type but show well organized dipping strata indicating appreciable progradation the submerged paleo channel system the paleo seomjin river associated with the sand ridge field suggests that the ridges primarily originated from river mouth sandy shoals which subsequently developed into shore parallel linear sand bodies in high energy environments the combined effect of coastal tidal and longshore and offshore ocean currents was possibly responsible for shore parallel sediment transport and growth of the ridges 14c dates core lithology and sea level data suggest that the sand ridges mainly formed and developed during the middle period of the postglacial transgression they are postulated to have developed sequentially from offshore to onshore in response to sea level rise during that time very slow sea level rise and high sediment supply through the paleo channel system probably provided favorable conditions for forming the sand ridges the ridges became inactive during the late transgression period as a result of a substantial reduction of wave and current strength and remained on the mid shelf

subduction and exhumation related structures in the cycladic blueschists insights from south evia island aegean region greece 1 detailed geological mapping structural investigation and amphibole chemistry analyses in southern evia aegean sea greece allow us to place new constraints on the internal structural architecture and tectonic evolution of the cycladic blueschists we show that the early deformation history was related to ese directed thrusting resulting in the stacking of the styra and ochi nappes which constitute the cycladic blueschist unit in evia these early thrust movements initiated just before and proceeded at peak conditions of the eocene high pressure metamorphism subsequent constrictional deformation gave rise to e w trending upright folding accomplished at the early exhumation stage the main ductile stage exhumation occurred during a single deformation phase associated with the decompression of blueschist rocks from the stability field of crossite to that of actinolite this phase was characterized by localization of ductile deformation into a series of major tens of meters thick ene directed shear zones which cut up section in their transport direction and restack the early thrust and fold sequence locally bringing the structurally lower styra nappe over the higher ochi nappe it is suggested that these zones operated as thrusts rather than normal sense shear zones as has been previously argued and were possibly formed during the oligocene ene ward extrusion of the blueschists brittle ductile ne dipping normal faulting of post early miocene age was probably responsible for the final exhumation of rocks

surface manifestation of internal tides generated near hawaii analysis of topex poseidon satellite altimetry reveals short wavelength fluctuations in the ocean surface tide that are attributable to internal tides a significant fraction of the semidiurnal internal tide generated at the hawaiian ridge is evidently phase locked to the astronomical potential and can modulate the amplitude of the surface tide by 5 cm the internal tide is thus easily mapped along satellite groundtracks and it is found to be spatially coherent over great distances with waves propagating well over 1000 km from the hawaiian ridge before decaying below noise level both first and second baroclinic modes are observed in both the m 2 lunar and s 2 solar tides the high space time coherence is in sharp contrast to what is often inferred from current meter observations but it confirms recent speculations from an acoustic experiment north of hawaii

global observations of open ocean mode 1 m2internal tides abstracta global map of open ocean mode 1 m2 internal tides is constructed using sea surface height ssh measurements from multiple satellite altimeters during 1992 2012 representing a 20 yr coherent internal tide field a two dimensional plane wave fit method is employed to 1 suppress mesoscale contamination by extracting internal tides with both spatial and temporal coherence and 2 separately resolve multiple internal tidal waves global maps of amplitude phase energy and flux of mode 1 m2 internal tides are presented the m2 internal tides are mainly generated over topographic features including continental slopes midocean ridges and seamounts internal tidal beams of 100 300 km width are observed to propagate hundreds to thousands of kilometers multiwave interference of some degree is widespread because of the m2 internal tide s numerous generation sites and long range propagation the m2 internal tide propagates across the critical latitudes for parametric subharmonic instability 28 8 s n

complex strain patterns developed at the frontal and lateral tips to shear zones and thrust zones abstract many of the complex strain patterns seen in shear zones and thrust zones such as variable fabric orientations refolded folds and fabrics together with folds with hinges almost parallel to the main transport direction can be explained in terms of differential movement within the shear zones these strains are developed at the frontal and lateral tips of the zones as they propagate examples are taken from the moine thrust zone of scotland which show variations in strains particularly at the lateral tips the form of differential movement described here may lead to complex strain paths and non plane strain ellipsoids and the spatial variations in finite strain may be used to delineate zones of extensional and compressional flow and differential movement in the shear zones or thrusts

model estimates of m2 internal tide energetics at the hawaiian ridge 1 a primitive equation model is used to examine the structure and energetics of m 2 internal tides generated at the hawaiian ridge recent estimates based on altimeter data suggest that 20 gw of barotropic tidal dissipation occurs at the ridge with conversion to internal tides believed to be the dominant dissipation mechanism the model simulates an internal tide that accounts for 9 7 gw of radiated energy away from the ridge in the northeast and southwest directions the strongest generation occurs at three sites where enhanced barotropic currents flow across elongated topographic features the depth integrated baroclinic energy flux and energy densities at these sites are on the order of 10 4 w m 1 and 10 4 j m 2 respectively a modal decomposition indicates that 62 of the outgoing energy flux is accounted for by the first internal mode 15 is accounted for by the second mode and less than 5 is accounted for by each subsequent higher mode the tidal dissipation due to bottom friction along the ridge is estimated to be 0 1 gw the level of turbulent dissipation near the ridge owing to tidal energy conversion remains to be determined to assess fully the barotropic baroclinic energy budget

evolution of a passive crustal scale detachment syros aegean region insights from structural and petrofabric analyses in the hanging wall abstract new detailed micro structural investigations quartz petrofabric analyses and geological structural mapping in southeast syros cycladic massif aegean region allow us to place new constraints on the tectonic evolution of the uppermost unit which occupies the immediate hanging wall of the crustal scale vari detachment we show that the eocene oligocene deformation history in the hanging wall of this detachment is associated with sw directed ductile shearing this history includes an early distributed constrictional deformation expressed by transport parallel upright folds l tectonites and cleft girdles quartz c axis fabrics that were formed at temperatures 500 c ductile deformation progressively localized at the bottom of the uppermost unit leading to the formation of a greenschist facies mylonitic zone under plane strain conditions inferred from type i cross girdles quartz c axis fabrics the ongoing mylonitization was also associated with temporally increasing pure shear component of deformation coupled with cooling from 500 c to 400 c we suggest that the vari detachment represents a passive normal sense roof fault resulted from the ne directed ductile extrusion of the blueschist unit footwall at middle eocene oligocene times in the middle miocene the activation of the brittle ssw directed late vari detachment enhanced the brittle exhumation of both the blueschist unit and the vari detachment

shallow seismic stratigraphy and distribution pattern of late quaternary sediments in a macrotidal bay gunhung bay west coast of korea abstract the shallow seismic stratigraphy of late quaternary sediments in gunhung bay a macrotidal coastal embayment of western korea was investigated by means of analyzing high resolution seismic profiles and sediment samples late quaternary sediments up to 20 m thick overlie the irregular surface of the acoustic basement the sediments consist mainly of sands muddy sands and sandy muds and show a zonal facies distribution the distribution pattern appears to be largely controlled by the tidal currents in the bay the sedimentary column above the acoustic basement can be divided into two sequences by a relatively strong mid reflector which is interpreted as the erosional pre holocene surface formed during low sea level many v shaped erosional patterns in this reflector indicate the existence of old tidal channels the sediments underlying the mid reflector are interpreted to be semi consolidated pre holocene tidal deposits presumably deposited during the last interglacial period while the sediments overlying this reflector represent the late holocene tidal desposits deposition of the late holocene sediments began probably at about 5000 yrs b p when sea level approached its present level

tertiary west spitsbergen fold and thrust belt on broggerhalvoya svalbard structural evolution and kinematics the tertiary fold and thrust belt on broggerhalvoya is characterized by a ne vergent pile of nine thrust sheets the basal sole thrust of the pile is located in precambrian phyllites and climbs up section to the ne the lower thrust sheets consist predominantly of post caledonian cover sediments two thrust sheets in the central part of the pile contain a syncline and anticline on a kilometer scale the kilometer scale fold is cut by juxtaposed thrusts giving rise to the formation of four structurally higher basement dominated thrust sheets a five stage kinematic model is proposed 1 in sequence foreland propagating formation of the lower thrust sheets with ramp flat geometries in response to n s subhorizontal bedding parallel movements 2 change in tectonic transport to more east northeasterly directions and first out of sequence thrusting inversion and uplift of the basement in the hinterland formation of the kilometer scale fold structure 3 truncation of the kilometer scale fold by a thrust fault and stacking of the highest basement dominated thrust sheets by hindward propagating mode of thrust generation 4 n s extension due to extensional collaps of the stack 5 w e extension the strain of the thrust sheets is predominantly compressive with the exception of the structurally highest thrust sheet reflecting a temporal change to a more transpressive regime ramping of some thrust faults is suggested to be in part controlled by reactivated carboniferous normal faults the basal sole thrust of the thrust sheet stack also follows the trend of the kongsvegen fault which showed enhanced activity during late mesozoic early tertiary extension the curvature of the west spitsbergen fold and thrust belt on broggerhalvoya is interpreted to be controlled mainly by oblique ramping on the kongsvegen fault associated with pinning on the nordfjorden block as well as by along strike lithological and thickness variations of the post caledonian strata in addition this suggests that pre existing structures have controlled the tertiary geometry the temporal change in the kinematics during thrust tectonics can be linked with the plate tectonic framework in the arctic during tertiary times

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

deciphering subduction from exhumation in the segmented cycladic blueschist unit central aegean greece the cycladic blueschist unit cbu represents the northern passive margin of the adria continental block and ophiolites that are the remnants of the pindos ocean which were affected by high pressure low temperature metamorphism in the blueschist and eclogite facies during the eocene prior to the lutetian the ophiolitic and margin units were thrust towards the sw inside a ne dipping subduction zone two subsequent exhumation stages are characterized by top to the ne senses of shear i from mantle depths to lower crustal levels before 37 ma which was accommodated by an extensional inversion of the vardar suture zone and ii from deep crustal levels to the near surface between 30 and 20 ma which was accommodated by the north cycladic detachment it is during this late stage of ductile exhumation that the central cyclades core complex was exhumed segmentation of the cbu by normal faults started at 12 ma as recorded by the low temperature thermochronometers and was coeval with block rotation and folding with ns trending axes which were predominantly controlled by the myrthes ikaria strike slip fault in the centre of the cyclades a map restoration of the cbu geometry prior to segmentation has been carried out using available structural and paleomagnetic data the restoration shows that following the cbu exhumation from mantle depths to crustal levels a single core complex was exhumed along a single ne dipping detachment

parallel stretching lineations and fold axes oblique to a shear displacement direction a model and observations abstract spatial variations in shear strain rate are expected in ductile shear zones where the variation is a change in shear strain perpendicular to the displacement direction the effect is to rotate the shear slip planes this is a mechanism for giving a rotation of fold axes into parallelism with the slip and extension direction in a rock if such a variation in shear strain affects rocks with a strong planar anisotropy it is possible to produce a fabric with an apparent stretching lineation parallel to fold axes but both significantly oblique to the slip direction a possible example of this is seen in strongly deformed quartz mica schists from syros greece where a stretching lineation is seen parallel to fold hinges over a range of fold axes orientations of at least 40

coaxial flattening at deep levels of orogenic belts evidence from blueschists and eclogites on syros and sifnos cyclades greece this work presents new structural data from a high pressure low temperature hp lt metamorphic terrane exposed on the islands of syros and sifnos cyclades greece the structure and the metamorphism of a relatively coherent hp lt rock section were studied in order to elucidate how strain was accommodated at deep crustal levels during the formation and exhumation of hp lt rocks at least three deformation phases associated with eclogite and blueschist facies conditions p 8 15 kbar t 400 550 degreesc were recognised the earliest deformation fabric s1 preserved as inclusion trails within garnet porphyroblasts is aligned to define a sub vertical schistosity at present orientation which is frequently orthogonal to the flat matrix schistosity s2 and may indicate that deep crustal thickening involved upright folding the currently dominant fabric in the hp rock section s2 is usually moderately dipping and locally contains nw trending glaucophane lineations symmetric pressure shadows and eclogitic boudins the symmetric structures associated with this fabric seem to indicate coaxial vertical thinning although the existence of non coaxial structures out of the study area cannot be excluded glaucophane bearing shear bands s3 with top to nw sense of shearing locally crosscut the earlier structures the latest recognised fabric d4 is scarce and often absent within the hp rocks it is associated with top to ne kinematic criteria that formed at greenschist facies conditions p 4 7 kbar t 400 450 degreesc based on these observations it is suggested that partitioning of strain occurred at different crustal levels and at different times deep crustal deformation was governed by thickening via upright folding followed by coaxial vertical thinning whereas non coaxial shearing occurred when the rocks were already exhumed to relatively shallow crustal levels the earliest fabrics d1 to d3 pertain to alpine orogenesis and possibly to syn orogenic extension whereas the latest correspond to whole crust back are extension c 2002 elsevier science ltd all rights reserved

using an altimeter derived internal tide model to remove tides from in situ data internal waves at tidal frequencies i e the internal tides are a prominent source of variability in the ocean associated with significant vertical isopycnal displacements and currents because the isopycnal displacements are caused by ageostrophic dynamics they contribute uncertainty to geostrophic transport inferred from vertical profiles in the ocean here it is demonstrated that a newly developed model of the main semidiurnal m2 internal tide derived from satellite altimetry may be used to partially remove the tide from vertical profile data as measured by the reduction of steric height variance inferred from the profiles it is further demonstrated that the internal tide model can account for a component of the near surface velocity as measured by drogued drifters these comparisons represent a validation of the internal tide model using independent data and highlight its potential use in removing internal tide signals from in situ observations

significant dissipation of tidal energy in the deep ocean inferred from satellite altimeter data how and where the ocean tides dissipate their energy are long standing questions1 that have consequences ranging from the history of the moon2 to the mixing of the oceans3 historically the principal sink of tidal energy has been thought to be bottom friction in shallow seas4 5 there has long been suggestive evidence6 7 however that tidal dissipation also occurs in the open ocean through the scattering by ocean bottom topography of surface tides into internal waves but estimates of the magnitude of this possible sink have varied widely3 8 9 10 11 here we use satellite altimeter data from topex poseidon to map empirically the tidal energy dissipation we show that approximately 1012 watts that is 1 tw representing 25 30 of the total dissipation occurs in the deep ocean generally near areas of rough topography of the estimated 2 tw of mixing energy required to maintain the large scale thermohaline circulation of the ocean12 one half could therefore be provided by the tides with the other half coming from action13 on the surface of the ocean

ductile nappe stacking and refolding in the cycladic blueschist unit insights from sifnos island south aegean sea new geological and structural mapping combined with kinematic and amphibole chemistry analyses is used to investigate the deformation history of the cycladic blueschist unit cbu on sifnos island cyclades aegean sea we concentrate on north sifnos an area characterized by exceptionally well preserved eclogites and blueschists our data show that the early main phase d2 of ductile deformation in the cbu occurred synchronous with the transition from prograde to close to peak retrograde conditions this deformation phase took place at middle eocene and is related to ese directed thrusting that emplaced the metavolcano sedimentary subunit over the marble subunit the subsequent exhumation related d3 deformation is characterized by gently ne plunging folds and ne directed contractional shear zones that formed parallel to the axial planes of folds ne directed shearing occurred under blueschist and transitional blueschist greenschist facies conditions during late eocene oligocene and caused the restacking of the early nappe pile we suggest that a mechanism of ductile extrusion of the cbu in a tectonic setting of net compression could explain better the recorded exhumation related deformation than a mechanism of syn and post orogenic extension our new kinematic results in combination with previous works in the cyclades area reveal a regional scale change in tectonic transport direction from w nw e se at late cretaceous middle eocene to e ne w sw at late eocene oligocene times the observed change in transport direction may be governed by the relative motion of africa with respect to europe during alpine orogeny

propagation of low mode internal waves through the ocean abstract the baroclinic tides play a significant role in the energy budget of the abyssal ocean although the basic principles of generation and propagation are known a clear understanding of these phenomena in the complex ocean environment is only now emerging to advance this effort a ray model is developed that quantifies the effects of spatially variable topography stratification and planetary vorticity on the horizontal propagation of internal gravity modes the objective is to identify baroclinic shoals where wave energy is spatially concentrated and enhanced dissipation might be expected the model is then extended to investigate the propagation of internal waves through a barotropic mesoscale current field the refraction of tidally generated internal waves at the hawaiian ridge is examined using an ensemble of mesoscale background realizations derived from weekly ocean topography experiment topex poseidon altimetric measurements the path of mode 1 is only slightly affected by typical cur

strain models within spreading nappes abstract internal strain within nappes and thrust sheets is especially important in the understanding of emplacement mechanisms in this paper strain patterns within spreading nappes are investigated theoretically and experimentally three types of spreading nappe are distinguished using various boundary conditions spreading gliding spreading and extruding spreading nappes each type is placed in its proper natural environment strain components and strain gradients are summarized from the use of scale models performed with analogue materials mathematical computations from experimental modelling allow the calculation of 1 1 the schistosity trajectories in vertical flow planes 2 2 the relationship between stretch and transport direction and 3 3 the spatial distribution of different types of strain ellipsoid these provide some tests which make it possible to demonstrate in the field whether nappes are or are not gravity induced finally some field examples from the central alps and the pyrenees are briefly discussed they provide good support to the strain models presented in the present paper

the tectonometamorphic and magmatic evolution of the uppermost unit in central crete melambes area constraints on a late cretaceous magmatic arc in the internal hellenides greece abstract crete consists of a nappe pile that formed during alpine subduction and collision the lower nappes belong to the external hellenides whereas the uppermost nappe is ascribed to the pelagonian zone of the internal hellenides the uppermost unit consists of several subunits including the asterousia crystalline complex acc which comprises metasedimentary rocks meta granitoids and serpentinite the protolith age and the tectonometamorphic evolution of which are largely unknown in the present study we present new structural microfabric and geochronological data from the uppermost unit in the melambes area central crete 206 pb 238 u zircon ages la icp ms and id tims indicate granitic and dioritic intrusions between 71 9 0 6 and 76 9 0 3 ma identical ages have previously been obtained from comparable intrusions in eastern crete and on anafi the composition and geochemical signature suggest an extended magmatic arc along the southern active margin of the pelagonian lycian block post intrusive shearing transformed granite into orthogneiss whereas diorite remained free from foliation because of the lower amount of mechanically weak phases deformation microfabrics suggest top to the se shearing under amphibolite facies conditions of the acc and at greenschist facies conditions of rocks at the base of the acc referred to as akoumianos greenschist the akoumianos greenschist is considered as the northern part of the pindos realm that was subducted underneath the pelagonian lycian active margin based on our new and on published data the following orogenic stages are suggested to have contributed to the evolution of the hellenides during the late cretaceous to eocene 1 pre middle campanian collision and subduction of the pindos lithosphere underneath the southern margin of the pelagonian lycian terrane led to obduction and offscraping of serpentinized ocean floor and stacking of the acc during amphibolite facies top to the se thrusting 2 formation of a campanian magmatic arc along the pelagonian lycian active margin 3 maastrichtian collision and stacking of the magmatic arc during top to the se mylonitic shearing 4 palaeocene top to the se greenschist facies shearing of the acc on top of the akoumianos greenschist 5 late eocene thrusting of the uppermost unit on top of the arvi and pindos units thus top to the se was the dominant shear sense in the southern aegean from at least the mid late cretaceous until the eocene

a buried palaeosol and late pleistocene unconformity in coastal deposits of the eastern yellow sea east asia abstract deep drill core sampling with a high resolution seismic survey was carried out to identify a holocene late pleistocene boundary in the eastern coast of the yellow sea east asia analysis of core sections revealed the existence of an oxidized and desiccated sedimentary layer lying directly below a holocene horizon unit i and being developed at the top of a late pleistocene unit ii possibly last interglacial tidal deposit the buried oxidized sedimentary layer is characterized by semi consolidated yellowish sediments showing signs of desiccation and alteration such as periglacial cryogenic structures lithified trace fossils depletion of smectite and high geochemical weathering index ba sr ratio these features together with radiocarbon ages suggests that the layer defined as a palaeosol developed in marine sediments has formed as a result of prolonged subaerial exposure of unit ii sediments during the wisconsinan sea level lowstand producing a regional unconformity late pleistocene unconformity this unconformable bounding surface corresponds to a prominent near surface reflector r which is observed in seismic profiles obtained across the drilled core sections and further is traced ubiquitously across the yellow sea shelf consequently the buried palaeosol layer associated with the seismic reflector presents a key horizon for the understanding of late quaternary environmental changes and integrated stratigraphical correlation in the east asian marginal seas

spatial and temporal variability of global ocean mixing inferred from argo profiles 1 the influence of turbulent ocean mixing transcends its inherently small scales to affect large scale ocean processes including water mass transformation stratification maintenance and the overturning circulation however the distribution of ocean mixing is not well described by sparse ship based observations since this mixing is both spatially patchy and temporally intermittent we use strain information from argo float profiles in the upper 2 000 m of the ocean to generate over 400 000 estimates of the energy dissipation rate indicative of ocean mixing these estimates rely on numerous assumptions and do not take the place of direct measurement methods temporally averaged estimates reveal clear spatial patterns in the parameterized dissipation rate and diffusivity distribution across all the oceans they corroborate previous observations linking elevated dissipation rates to regions of rough topography we also observe heightened estimated dissipation rates in areas of high eddy kinetic energy as well as heightened diffusivity in high latitudes where stratification is weak the seasonal dependence of mixing is observed in the northwest pacific suggesting a wind forced response in the upper ocean

gamagyang bay southern coast of korea sedimentation on a tide dominated rocky embayment abstract layered up to 30 m thick sediment sequences overlie acoustic basement of cretaceous tuffs in the gamagyang bay a shallow post glacial embayment of approximately 150 km 2 in area on the southern coast of the korean peninsula sediments consisting mainly of terrigenous and bioturbated mud tend to accumulate at a rate of more than 134 cm 1000 yrs more in the central part of the bay than on the margins sedimentation has been influenced dominantly by strong tidal currents up to 2 5 knots resulting in numerous depressions or moats in the vicinity of islands and points the sedimentary sequences of the moats are either depositional or depositional erosional in origin acoustic basement lies deeper in the central axis of the bay following the buried paleovalleys here the thick sediments contain probable gas encountered on uniboom records characterized by the impedance of acoustic penetration the existence of mid reflectors above the acoustic basement suggests that the gamagyang bay was subaerially exposed during the last glacial period prior to about 4500 yrs b p

estimates of internal tide energy fluxes from topex poseidon altimetry central north pacific energy fluxes for first mode m2 internal tides are deduced throughout the central north pacific ocean from topex poseidon satellite altimeter data temporally coherent internal tide signals in the altimetry combined with climatological hydrographic data determine the tidal displacements pressures and currents at depth which yield power transmission rates for a variety of reasons the deduced rates should be considered lower bounds internal tides are found to emanate from several large bathymetric structures especially the hawaiian ridge where the integrated flux amounts to about 6 gigawatts internal tides are generated at the aleutian trench near 172 w and propagate southwards nearly 2000 km

evolution of late quaternary deposits on the inner shelf of the south sea of korea abstract high resolution 3 5 khz seismic profiles and sediment samples were analysed to delineate the shallow seismic stratigraphy of late quaternary deposits in the central part of the korean south sea the stratigraphy above the acoustic basement is represented by three distinct sedimentary sequences separated by erosional boundaries the upper sequence a has an acoustically semi transparent signature usually without distinct internal reflectors and overlies the flat lying mid reflector r the sediments in this sequence consist of bioturbated terrigenous mud derived mainly from the seomijin river they have developed during the last 5000 yrs and have an accumulate rate of 10 40 cm 100 yrs reflector r represents the postglacial transgressive layer formed during the last stage of the holocene sea level rise approximately between 7000 yrs b p and 5000 yrs b p the middle sedimentary sequence b below r shows parallel to subparallel internal reflectors and prograding clinoforms that have formed largely during the last glacial period the top of this sequence displays various erosional channels and transparent fills produced by subaerial and fluvial erosion of the pre existing shelf the submerged channels indicate the existence of a paleochannel system presumambly the extension of the paleo seomijin river during the sea level lowstand the lower sequence c has an irregular erosional upper surface and an acoustically transparent subbottom it is interpreted as the erosional remnants of earlier pleistocene sediments formed in shallow water environments

structural development of high pressure metamorphic rocks on syros island cyclades greece abstract new data obtained during re mapping of the northern part of syros cyclades greece allow the refinement of existing concepts about the structural evolution of this island a metabasite belt and its metasedimentary envelope near kampos and san michali were mapped at a 1 5000 scale with special emphasis on the structural inventory the hp lt rocks p 1 5 gpa t 500 c at 50 ma exposed are intensely deformed by at least two isoclinal folding events relative age relations between deformation and peak metamorphism indicate that isoclinal folding took place before or during peak metamorphism later deformation stages include miocene non penetrative upright kink folding and crenulation transpressional strike slip faulting and open upright cylindrical folding followed by the development of steep normal faults taking into account recent zircon u pb geochronological constraints lithostratigraphic observations and published data on the neogene structural evolution of the aegean we present a history for the rocks of syros beginning with the formation of the oceanic crust represented by the metabasites to the present

internal tide oceanic tomography a concept of internal tide oceanic tomography itot is proposed to monitor ocean warming on a global scale itot is similar to acoustic tomography but that work waves are internal tides itot detects ocean temperature changes by precisely measuring travel time changes of long range propagating internal tides the underlying principle is that upper ocean warming strengthens ocean stratification and thus increases the propagation speed of internal tides this concept is inspired by recent advances in observing internal tides by satellite altimetry in particular a plane wave fit method can separately resolve multiple internal tidal waves and thus accurately determines the phase of each wave two examples are presented to demonstrate the feasibility and usefulness of itot in the eastern tropical pacific the yearly time series of travel time changes of the m2 internal tide is closely correlated with the el nino southern oscillation index in the north atlantic significant interannual variations and bidecadal trends are observed and consistent with the changes in ocean heat content measured by argo floats itot offers a long term cost effective environmentally friendly technique for monitoring global ocean warming future work is needed to quantify the accuracy of this technique

structural development of an archean orogen western point lake northwest territories the point lake orogen in the central archean slave province of northwestern canada preserves more than 10 km of structural relief through an eroded antiformal thrust stack and deeper anastomosing midcrustal mylonites fault restoration along a 25 km long transect requires a minimum of 69 km slip and 53 km horizontal shortening in the western part of the orogen the basal decollement places mafic plutonic volcanic rocks over an ancient tonalitic gneiss complex ten kilometers to the east in the keskarrah bay area slices of gneiss unroofed on brittle thrusts shed molasse into several submerged basins conglomerates and associated thinly bedded sedimentary rocks are interpreted as channel levee and overbank facies of this thrust related sedimentary fan system the synorogenic erosion surface at the base of the conglomerate truncates premetamorphic or early metamorphic thrust faults formed during foreland propagation while other thrusts related to hinterland progressing imbrication displace this unconformity tightening of synorogenic depositional troughs resulted in the conglomerates present localization in synclines to the west of associated thrust faults and steepening of structural dips eastern parts of the orogen consist of isoclinally folded graywackes composed largely of mutti and ricci lucchi turbidite facies b c and d interpreted as submarine fan deposits eroded from a distant volcanic arc thrust faults in the metasedimentary terrane include highly disrupted slate horizons with meter scale duplex structures and recrystallized calcmylonites exhibiting sheath folds and boudin trains with very large interboudin distances the sequence of fabric development and the overall geometry of this metasedimentary terrane strongly resembles younger forearc accretionary prisms conditions of deformation along the thrusts parallel the regional metamorphic zonation amphibolite facies in the basal decollement through greenschist facies shear zones to cataclastic crush zones in the region of emergent thrusts in keskarrah bay depth differences can account for only half of the metamorphic gradient thermal profiles which increased downwards in obducted greenstone belts and synthrusting plutonism explains other high metamorphic gradients a tectonic model involving the collision of an accretionary prism with a continental margin best explains the structural and sedimentological evolution of the orogen