short term flow and water temperature fluctuations in sagami bay japan associated with variations of the kuroshio during the non large meander path abstract short term flow and water temperature fluctuations in sagami bay were examined using mooring and hydrographic data observed during the non large meander path nlm of the kuroshio in the surface layer 1 in the central part of the bay this flow is a part of an intrusion of kuroshio water via the oshima west channel into the bay and or a cyclonic circulation in the northern part of the bay the cyclonic circulation which is approximately balanced under the geostrophic flow relationship is mainly generated or enhanced by the intrusion which is accompanied by eastward propagation of the small meander of the kuroshio south of japan during the transition from the nearshore non large meander path nnlm to the offshore non large meander path onlm regardless of season the water temperature fluctuation in the subsurface layer 150 m is caused by upwelling of cold deeper water and is closely related to the eastward flow fluctuations in the surface layer in the central part of the bay our analysis leads us the conclusion that the upwelling occurs as the response of the subsurface density field to the surface flow field under the earth s rotation additionally the intrusion of kuroshio water via the oshima west channel tends to cause not only cyclonic circulation and upwelling in the northern part of the bay but also the kyucho which is the coastal density current under the earth s rotation in the bay s coastal area during the non large meander path nlm

eulerian mean surface velocity field derived by combining drifter and satellite altimeter data 1 combining surface drifter and satellite altimeter data we estimate eulerian mean sea surface velocity with a resolution of quarter degrees in both latitude and longitude the eulerian mean velocity is calculated by subtracting the altimeter derived velocity anomaly i e deviation from the temporal mean at the time when a drifter measured the surface velocity from this drifter measured velocity the method is applied to the surface flow of the north pacific using topex poseidon and ers 1 2 altimeter data and woce toga surface drifter data obtained during october 1992 to january 2001 the estimated eulerian mean velocities for the kuroshio south of japan and the kuroshio extension region tend to be smaller than simple averages of drifter derived velocities by 20 to 50 cm sec 1 the instantaneous velocities are obtained every ten days as sums of the eulerian mean velocities and velocity anomalies they agree well with in situ surface velocities measured by acoustic doppler current profilers

tsushima warm current paths in the southwestern part of the japan sea abstract we compiled a long term record of monthly mean sea surface currents in the japan sea from satellite altimetry and satellite tracked drifter data the record covers the entire japan sea for the period from may 1995 through january 2009 using these data we examined the path of the tsushima warm current in the southwestern part of the japan sea the mean sea surface current field revealed a triple branch pattern the first branch through the eastern channel of the tsushima strait flows along the coast of japan with a mean current velocity of 20 cm s 1 the second branch flows along the continental shelf edge at around the 200 m isobath with a mean current velocity of 12 cm s 1 the third branch flows along the east coast of the korean peninsula with a mean current velocity of 25 cm s 1 we investigated seasonal variation in the path of each branch the first branch flowing along the japanese coast throughout the year is highly stable the second branch is stable throughout the year except in november the third branch flowing along the east coast of korea is highly stable until 38 n downstream of the third branch around 38 n the current bifurcates into northeastward and southeastward currents the northeastward current exhibits stable flow from june to february except in january this current joins an eastward current originating around 39 n 128 5 e the southeastward current flows stably in june september and december there were two current paths east of 131 e over the continental shelf off the san in coast of japan the nearshore current flows along the japanese coast with a mean current velocity of 23 cm s 1 and the offshore current flows around the continental shelf area with a mean current velocity of 19 cm s 1 these two currents are highly stable throughout the year a current flows to the west of oki island to around 38 5 n and is highly stable in all months except march to july these results provide a schematic view of the paths of the tsushima warm current in the southwestern part of the japan sea

formation of lateral patterns in rock properties by dolomitization evidence from a miocene reaction front bonaire netherlands antilles abstract petrophysical and geochemical properties of dolomites may exhibit a nested set of lateral patterns typically at the scales of a few meters to 20 m this study assesses whether those lateral patterns are inherited from the limestone precursor or formed during dolomitization sampling was done across a preserved limestone to dolomite reaction front in grainstones of the miocene seroe domi formation bonaire netherlands antilles post dolomitization diagenetic overprinting in the two rock types is absent or minimal two 65 m lateral transects were drilled at 30 cm spacing in two separate beds porosity permeability and geochemical 18o 13c mn sr and na analyses were performed on all 287 recovered samples and 287 thin sections were point counted for petrographic attributes variography shows that dolomite abundance and porosity contain three scales of lateral variability much of the signal is random sample to sample noise as 65 of the total spatial variance occurs at 30 cm spacing however porosity and dolomite abundance also exhibit a short scale correlation length of 3 7 m and a long range oscillatory pattern hole effect at 16 m both of which are also periodic trace elements mn sr and permeability exhibit short range correlation to 5 8 m but no long range pattern mole mg and 13c show increasing variance with distance and all other dolomite attributes exhibit no spatial patterns no limestone attributes show evidence for any short range or long range oscillatory patterns this indicates that the lateral patterns in dolomite abundance porosity permeability sr and mn contents were not inherited from the limestone precursor dolomitization is interpreted to be the cause of the observed spatial patterns as that is the only geologic process that has affected the dolomite but not the limestone on the other side of the front geochemical self organization during the dolomitization process is suggested to be the mechanism by which the spatial patterns in the dolomites emerge a model for that self organizing process is proposed that involves positive feedbacks between precipitation dissolution textural properties reaction rates carbon transport and the evolving flow field relative to mississippian permian and eocene dolomites that have been studied previously the seroe domi dolomites have similar porosity variance at 30 cm spacing and hole effects with slightly greater wavelengths and much larger magnitudes any differences are interpreted to be related to diagenetic history the older dolomites have been affected by burial diagenesis and or weathering which would likely increase sample to sample variability therefore increasing short scale randomness decreasing the magnitude of hole effects and shortening wavelengths of hole effects the lateral patterning formed by dolomitization may thus not be as strongly expressed in ancient dolomites that have complex burial histories

alterations in guano phosphates and mio pliocene carbonates of table mountain santa barbara curacao abstract the table mountain santa barbara consisting of the mio pliocene seroe domi limestone formation was probably covered with a guano layer in the pleistocene solutions carrying guano derived phosphate percolated downwards resulting in partial phosphatization of the underlying limestones only two phosphate minerals are present in the table mountain apatite and whitlockite phosphatization includes both replacement of the original carbonate or pre phosphate dolomite and cementation in primary as well as secondary porosity cryptocrystalline isotropic phosphate cement micro crystalline apatite isopachous apatite fringe cement multiple zoned apatite crusts rhombic whitlockite cements two factors controlled the final distribution of the phosphate within the table mountain firstly changing positions of the sea level and therefore of the diagenetic environments determined the overall distribution of the phosphatized interval a horizontal layer 98 128 m above sea level sandwiched between two non phosphatized limestone units original carbonate facies and mineralogy was the second controlling factor causing the final variations in degree of phosphatization the limestones comprise two lithofacies a coralliferous limestone lenses erratically distributed amidst and b micritic limestones these coralliferous limestones are phosphatized preferentially forming so called phosphate pockets sharply outlined within a non phosphatized micritic limestone host these pockets are characteristically organized into five zones which are described in detail higher original porosity permeability of the coralliferous limestone lenses as compared to the micrites additionally enhanced by a phase of pre phosphate dolomitization determined preferential phosphatization of this facies type a second controlling factor was the original carbonate mineralogy and resulting dia

far reaching effects of the hawaiian islands on the pacific ocean atmosphere system using satellite data we detected a wind wake trailing westward behind the hawaiian islands for 3000 kilometers a length many times greater than observed anywhere else on earth this wind wake drives an eastward ocean current that draws warm water from the asian coast 8000 kilometers away leaving marked changes in surface and subsurface ocean temperature standing in the path of the steady trade winds hawaii triggers an air sea interaction that provides the feedback to sustain the influence of these small islands over a long stretch of the pacific ocean

improved satellite altimetry in coastal systems case study of the corsica channel mediterranean sea 1 the fidelity of corrections and processing are critical for a realistic use of official altimetric products close to the coast a new processing strategy which starts from the topex poseidon gdrs with the addition of improved corrective terms is proposed and evaluated in the area of the corsica channel sea level anomalies agree with the coincident sea truth bottom pressure and tide gauge within 2 3 cm rms for seasonal and longer time scales analysis for almost ten years of coincident mooring and altimetric velocities shows that a substantial reduction of uncertainty to 4 cm s 1 may be possible after reasonable filtering of the noise introduced by more variable coastal sea surface states the conclusion is that the altimetry success is still limited to seasonal time scales and provided that the oceanographic signal ensures an adequate signature to be isolated from background noise

tectonic stratigraphic division and blind fold structures in nansha waters south china sea extensive multiple channel reflection seismic data have been collected in the nansha spratley islands waters the southern margin of the south china sea stratigraphic correlation is shown with focus on a comprehensive geophysixcal survey line run front offshore nw sabah to offshore se vietnam according to the varying tectono stratigraphy from southeast to northwest five tectonic belts can be determined i e the palawan borneo nappe nansha trough nanwei liyue compressive belt zheng he extensional belt and the circum southwest subbasin belt in the palawan borneo nappe neogene quaternary deposits were highly upthrust northwestwards resulting in a series of moderately to tightly folded anticlines separated by open synclines the nansha trough was a narrow deep water belt filled with thick undisturbed neogene quaternary deposits the nanwei liyue compressive bell was dominated by strongly folded paleo anticlines overlain by an undeformed sedimentary cap with a pronounced hiatus of paleogene sediments the zheng he extensional belt consisted of a rugged topography and paleogene half grabens bounded by listic faults the major extensional faults were reactivated to cut through the overlying neogene quaternary deposits over the circum southwest subbasin belt neogene quaternary deposits draped on the largely subsided fault blocks related to the late oligocene mid miocene seafloor spreading based on the regional stratigraphic correlation the prominent paleo anticlines found within the nanwei liyue compressive belt are deduced to consist of mainly mesozoic marine sediments that were compressed in the late mesozoic era therefore the nansha microcontinent block is shown to be a collision complex assembled during late mesozoic era c 2004 elsevier ltd all rights reserved

wind driven motions in the northeast pacific as measured by lagrangian drifters abstract analysis is presented of the time dependent motion of 47 surface drifters in the northeast pacific during fall 1987 and 16 drifters in fall and winter 1989 90 the drifters were designed at 15 m depth and were designed to have wind produced slips less than 2 cm s 1 for wind speeds up to 20 m s 1 the coherence of velocity and local wind is presented for motions with periods between 1 day and 40 days for periods between 5 and 20 days drogue motion at 15 m depth is found to be highly coherent with local wind with an average phase of 70 to the right of the rotating wind vector these results differ from analyses of fgge type drifters as reported by mcnally et al and niiler in the same area a model of wind produced slip as a function of drifter design is used to provide a possible explanation of the differences a linear regression which accounts for 20 40 of the current variance gives water motion al 0 5 of wind speed and 68 to the right of the wind vector assuming an ekman type balance

differential formation and circulation of north pacific central mode water abstract a repeat hydrographic section along 165 e was analyzed to verify a westward extension of the formation region of the north pacific ocean central mode water cmw suggested by previous synoptic observations and to investigate the relation between the formation region and thermohaline fronts the cmw formation region extends at least as far west as 155 e much farther than recognized in a previous study based on climatology it is located in two interfrontal regions between the kuroshio extension front and the kuroshio bifurcation front kbf and between the kbf and the subarctic front where two types of cmw namely the lighter variety with potential density of 25 8 26 2 kg m 3 and the denser one of 26 3 26 4 kg m 3 are formed how this differential formation of cmw is reflected in its gyrewide distribution was examined using one time sections of the world ocean circulation experiment woce hydrographic program in the north pacific the main circulation paths of the two types of cmw diverge eas

new mean dynamic topography of the mediterranean calculated from assimilation system diagnostics 1 the use of sea surface height ssh measurements by altimeter satellites in the mediterranean requires an accurate mean dynamic topography mdt field with a high horizontal resolution which must be added to observations this study presents a new mediterranean mdt estimate calculated from the diagnostics of an existing operational assimilation system in the mediterranean the calculation starts from the assumption that the error in the mdt field appears in the assimilation system as a temporally constant and spatially variable observational bias therefore we can reduce this error by calculating long term averages of dynamic topography departures and by subtracting them from the previous mdt field the analysis system statistics show that the assimilation of the ssh in the mediterranean is more accurate with the new mdt estimate

early diagenetic phosphate cements in the albian condensed glauconitic limestone of the tatra mountains western carpathians early diagenetic phosphate cements are described from the albian condensed glauconitic limestone of the tatra mountains western carpathians with regard to their macro and micromorphology distribution classification and genesis the cements occur within stratigraphically condensed semi pelagic foramini feral glauconitic layers and are associated with mature hardgrounds within the tatra albian limestone phosphate cement fabrics consist of crypto to microcrystalline carbonate fluorapatite and they occur as i rim envelopes ii infillings of intraparticle porosity iii rim cement iv multiple rim cement v palisade fabric and vi cluster cement micromorphological variability of the cement fabrics results from varying texture of the cemented sediment the nature of original porosity as well as from presence of associated microbial fabrics the microbial fabrics are interpreted as fossilized coccoid cyanobacteria phosphate cementation developed under peculiar early diagenetic conditions within semi closed microenvironments rich in organic matter in the marine phreatic environment the cementation contributed to the formation of phosphatic fossils and hardgrounds the accretion of the cements was due to concentration of biologically uptaken phosphorus near the sediment water interface enrichment of pore fluids with respect to phosphate and its precipitation within restricted microenvironments phosphate cementation post dated seafloor formation of pelletal glauconite but predated partial decomposition of organic matter as well as dissolution or neomorphism of aragonite and high mg calcite phosphate cementation occurred on a carbonate platform following the submersion of urgonian reefal build ups episodes of phosphate cementation were repeated during the sedimentation of the tatra albian limestone as a response to rapid relative sea level rises and increased influence of nutrient rich tethyan waters

kuroshio stream path variation and its associated velocity structures south of shikoku japan during 1993 1995 twelve repeat observations of the kuroshio south of shikoku japan were carried out for obtaining a vertical velocity section of the upper 300m using a towed type acoustic doppler current profiler adcp among the twelve observations the kuroshio took the onshore path 9 times and the offshore path 3 times the cross stream velocity distribution around the kuroshio stream axis is asymmetric steeper on the onshore side than on the offshore side for the onshore path while it is symmetric for the offshore one the core with a maximum velocity is submerged to 100 200m depths for the onshore case and located at the near surface for the offshore case in the combined analysis with the rapid bulletin of ocean conditions the kuroshio mainly took an onshore path with stream axis positions less than 80km from cape ashizuri but the distance was increased over 150km at the frequency once a year

wind induced kuroshio warm water intrusion into sagami bay 1 the mechanisms of the periodic kuroshio warm water intrusion kwwi into sagami bay through the oshima west channel owc and the fluctuation of the current field in the bay were investigated using high frequency oceanic radar observation data satellite imagery and meteorological data during the period from 15 december 2000 to 16 january 2001 the kuroshio took a nonlarge meander path looping south around the kii peninsula and then turning sharply north toward the izu peninsula ip kuroshio warm water kww then flowed into sagami bay periodically through the owc on a synoptic timescale of 8 11 days statistical analysis of the data indicated that the occurrence of the kwwi and the variability in the kuroshio front were highly coherent with wind velocity field fluctuations corresponding to the passage of cyclones across northern japan when southward to southwestward winds dominated in and around sagami bay the kuroshio front approached the southern coast of the ip and then the kww strongly intruded into the bay through the owc when eastward to northeastward winds prevailed the front moved offshore about 10 20 km ending the kwwi the distances of the kuroshio front movements were consistent with the internal radius of the deformation estimated from conductivity temperature depth data collected off the ip suggesting that the kuroshio front movement was induced by the onshore offshore surface ekman transport associated with the wind velocity field regime shift corresponding to the passage of cyclones in addition examination of the vorticity dynamics in the northern part of the bay based on radar derived surface current data indicated that the cyclonic circulation generated in the bay was enhanced due to the transport of the positive relative vorticity by the kwwi plus the horizontal convergence accompanied by the stretching of the vorticity

uranium geochemistry and dating of pacific island apatite abstract uranium series disequilibrium dating of island phosphate deposits is evaluated in terms of known associated coral ages uranium geochemistry and stratigraphic sequences as well as the concordance between the geochronometers 234 u 238 u 230 th 234 u and 226 ra 238 u u vi is the predominant oxidation state of uranium in island phosphorites and by analogy to the youngest surficial deposits most of the uranium initially bound is in the form of u vi sorbed by surfaces from seawater insular deposits contain more organic matter than even very young ocean floor samples and this leads to a greater probability of reduction of available recoil uranium than occurs in marine deposits as a consequence r vi r t r vi where r represents the 234 u 238 u activity ratio this situation is completely opposite from that observed for marine origin phosphorites we determined that a fraction of u vi in ancient insular phosphorites is very labile and lost to alkaline carbonate solutions with a uranium activity ratio even more depleted in 234 u than the bulk r vi most younger samples appear to have no more discordance between 234 u 238 u 230 th 234 u and 226 ra 238 u than marine phosphorites of similar apparent age young surficial atoll rim apatite cements and unconsolidated phosphorites date in the range of 1500 8000 years b p consistent with the concept of partial submergence of low lying coral islands prior to 2000 years b p sub surficial samples in the same environment date older at about 20 000 years b p violation of the closed system assumption occurs in at least 6 out of 13 ancient 800 000 year samples uranium series disequilibrium dating of insular apatite shows some promise as a recorder of climatic sea level events but the assumptions necessary for valid ages must be carefully evaluated for each occurrence

variability of the kuroshio current south of sagami bay as observed using long range coastal hf radars 1 ocean surface currents between cape nojima and hachijo island have been mapped since fall 2000 using a pair of seasonde long range hf radars during september 2000 through december 2001 the no large meander nlm nearshore n and offshore o modes were observed the surface current maps allowed new details to be observed in the structure of these modes and the transitions between them two noteworthy phenomena include blocking of the surface currents when the kuroshio was in an extreme nearshore position behind the zenisu ridge and the kyucho pattern when the current retroflexed from the nlmo position in early 2004 a large meander lm developed and was well established in its historical position south of honshu by august 2004 subsequently the lm continued propagating downstream but stopped when it encountered the izu ridge it then moved back to its original position near 137 5 e and the process repeated itself this east west oscillation resulted in two common positions for the lm south of sagami bay from its more westerly position lmw for west the kuroshio had a very favorable approach to the deep gap between miyake island and the zenisu ridge and the currents were strongly toward the northeast through the region when the meander moved up against the ridge lme for east a strong along ridge current toward the northwest was evident which turned sharply northeast when it encountered the shallow zenisu ridge the dominant timescale for this within mode variability was about 30 days

a tectonic model for the tertiary evolution of strike slip faults and rift basins in se asia abstract models for the tertiary evolution of se asia fall into two main types a pure escape tectonics model with no proto south china sea and subduction of proto south china sea oceanic crust beneath borneo a related problem is which if any of the main strike slip faults mae ping three pagodas and aliao shan red river asrr cross sundaland to the nw borneo margin to facilitate continental extrusion recent results investigating strike slip faults rift basins and metamorphic core complexes are reviewed and a revised tectonic model for se asia proposed key points of the new model include 1 the asrr shear zone was mainly active in the eocene oligocene in order to link with extension in the south china sea the asrr was less active during the miocene tens of kilometres of sinistral displacement with minor amounts of south china sea spreading centre extension transferred to the asrr shear zone 2 at least three important regions of metamorphic core complex development affected indochina from the oligocene miocene mogok gneiss belt doi inthanon and doi suthep around the asrr shear zone hence paleogene crustal thickening buoyancy driven crustal collapse and lower crustal flow are important elements of the tertiary evolution of indochina 3 subduction of a proto south china sea oceanic crust during the eocene early miocene is necessary to explain the geological evolution of nw borneo and must be built into any model for the region 4 the eocene oligocene collision of ne india with burma activated extrusion tectonics along the three pagodas mae ping ranong and klong marui faults and right lateral motion along the sumatran subduction zone 5 the only strike slip fault link to the nw borneo margin occurred along the trend of the asrr fault system which passes along strike into a right lateral transform system including the baram line

formation and fate of sedimentary depocentres on southeast asia s sunda shelf over the past sea level cycle and biogeographic implications abstract sea level variations are the major factor controlling sedimentation as well as the biogeographic patterns at continental margins over late quaternary times fluctuations on millennial time scales produce locally complex deposits in coasts and on shelves associated with short term influence on species development this article reviews the sedimentary and biogeographic history of the tropical siliciclastic sunda shelf as an end member of continental shelves regarding extreme width an enormous sediment supply and highest biodiversity in response to rapid sea level fluctuations we describe particular depositional segments as part of a genetic succession of zones from land to the deep sea based on literature data field observations and calculation of hydro isostatic adjustment effects on changing relative sea level these segments are characterized by individual sedimentary processes and deposits and by a specific potential for material storage and re mobilization long term regressive intervals led to overall sigmoidal promoting extremely thick and wide succeeding units in contrast rapid lateral shifts of defined depocentres over long distances took place in response to short term sea level fluctuations fully isolated small scale sediment bodies formed when sea level changed at exceptionally high rates as a result of the high availability of organic rich sediments mangrove and freshwater peats formed frequently over late quaternary times the appearance of thick massive and widespread peats is mainly linked to time intervals of a sea level rise at slow rates whilst organic matter appears much more dispersely in the sediments during episodes of rapidly changing sea level the preservation potential of the regressive units is generally high due to highest initial sediment supply stabilizing soil formation during exposure and rapid subsidence preservation of depositional elements from other periods is more exceptional and either restricted to local morphological depressions or to episodes of rapid sea level change besides complex channel incision an overall lowering of the sediment surface related to erosion as deep as 20 m or more over wide areas took place mainly during sea level lowering the final export of shelf material is documented by enormous mass wasting packages on the associated continental slope from a palaeogeographic perspective the rapid formation or disappearance of special habitat zones such as mangrove fringes and extended mud flats led to species establishment or truncation in distribution in addition the opening or closure of ocean passages as narrow bridges allowing limited species crossing or as fully colonized corridors had severe impact on eco fragmentation and the expansion or contraction of species independent of such particular conditions sea level changes have been too rapid over the past climatic cycle to allow full regeneration and mature development of coast related ecosystems

annual and interannual variability in the kuroshio current system abstract individual seasonal 300 m temperature maps were constructed over the kuroshio current system from 130 e to 170 w for a 4 year period from summer 1976 through spring 1980 using transpac xbt data and jodc temperature depth data quasi stationary meanders in the kuroshic current system occurred at 137 c i e kuroshio meander at 144 e and 150 e i e lee wave meanders and near 160 e i e meander over the shatsky rise a composite of the paths of the kuroshio i e the 12 c isotherm from the individual seasonal maps and the total variance map finds nodes i e minima and anti nodes i e maxima of variability to have existed along the mean kuroshio path the anti nodes coincided with the location of the quasi stationary meanders the nodes in between zonal propagation of temperature anomalies accounted for 20 30 of the total interannual variance these temperature anomalies propagated eastward at 0 5 1 5 cm s 1 in the region 140 155 e and westward at 1 to 2 cm s 1 in the re

geological development of the central and south vietnamese margin implications for the establishment of the south china sea indochinese escape tectonics and cenozoic volcanism abstract the vietnamese margin forms a key region to the understanding of escape tectonics and the development of the south china sea scs the existing geological reconstructions of the region are restricted to studies of single basins are based on limited amounts of geophysical data or analysis of onshore geological features these models are critically assessed on the basis of interpretation of the most comprehensive 2 d digital seismic database published to date within the area combined with a thorough analysis of existing literature and a new model is presented the vietnamese margin is underlain by a series of paleogene rift basins established through southeastward extrusion of indochina the east vietnam boundary fault evbf forms the almost 1000 km long seaward continuation of the left lateral ailao shan red river shear zone asrrsz toward the southern half of the phu khanh basin the evbf breaks up into discrete segments and splays into the se directed tua hoa fault zone paleogene faults splayed from the evbf and the mae ping shear zone and accommodated the coeval motion of these two major left lateral structural lineaments during the late oligocene basin inversions offshore occurred contemporaneously with initial right lateral inversion along the mae ping shear zone and the onset of major uplift of the metamorphic core complexes along the asrrsz it is suggested that a dramatic change of the regional stress pattern occurred in response to the northward movement of india and the effective coupling of the west burma block and india the later resulting in broadening of the indenting continental mass after the mid oligocene left lateral movements across the offshore evbf decreased and eventually ceased later onshore sinistral movements were accommodated by internal shortening and local clockwise block rotations within the shan thai terrain renewed rifting offshore south vietnam resulted from the jump of the scs spreading axis and subsequent neogene southwestward propagation of continental break up the neogene opening of the scs is viewed as a consequence of a slab pull associated with subduction of the proto scs underneath borneo as offshore neogene escape tectonism had virtually ceased during this phase of rifting right lateral transtension is inferred along n to nw oriented fault zones in the phu khanh and the nam con son basins rifting and by inference seafloor spreading continued until the end of middle miocene time although at significantly reduced rates during the final 5 10 ma termination of seafloor spreading is marked by a distinct latest middle miocene unconformity in the nam con son and the southern phu khanh basins neogene volcanism resulted in the build up of several magmatic structures across the central and south vietnamese margin and induced reactivation of older faults in the phu khanh basin the offshore magmatism heralded widespread volcanism onshore southern indochina associated with a latest neogene uplift and denudation event the uplift led to significantly increased siliciclastic accumulation rates offshore which repressed widespread carbonate deposition

the effect of orthophosphate on carbonate mineral dissolution rates in seawater the dissolution kinetics of a variety of synthetic and biogenic carbonates low mg calcite mg calcite and aragonite were investigated in gulf stream seawater salinity s 35 spiked with orthophosphate to a concentration of 50 m phosphate is known to inhibit calcite dissolution and has been reported to catalyze the dissolution of aragonite the main goal of the study was to assess whether the degree of inhibition depends on the mineralogy of the dissolving carbonate phase dissolution experiments were conducted at 25 c and a pco2 of 10 2 5 atm using the ph stat technique dissolution rates were measured at saturation states ranging from 0 1 to 0 8 times saturation with respect to the dissolving carbonate mineral and were compared to rates measured in low phosphate seawater the degree of inhibition caused by phosphate addition increased as saturation state with respect to the dissolving carbonate mineral increased at a saturation state of 0 2 addition of phosphate reduced dissolution rates by about a factor of 2 closer to equilibrium at a saturation state of 0 8 dissolution rates were reduced by about a factor of 4 more importantly all carbonate samples whether of synthetic or biogenic origin were inhibited to similar degrees at equivalent saturation states the catalysis reported by previous workers for synthetic aragonite appears to be an artifact of its anomalous non linear dissolution rate over time because phosphate inhibits the dissolution of different carbonate minerals to similar degrees selective dissolution of aragonite from metastable carbonate sediments cannot be promoted by the presence of orthophosphate

the stratigraphy structure and evolution of zengmu basin abstract the zengmu basin is a large tertiary marine sedimentary basin in the southern region of the south china sea it is considered to have multiple combinations of source rocks reservoirs and caprock making it a favourable prospect for oil and gas seismic investigations have shown that this has three tectonic sequences separated by two unconformities the upper sequence consists of oligocene to recent marine sediments the middle sequence is thought to be composed of paleogene to eocene shelf neritic clastic deposits and the lower sequence is interpreted as being pre tertiary metamorphic or igneous rocks the development of the basin has been controlled by faults especially by northwest trending faults leading to gradual stepped block subsidence to the northeast three fault systems trending nw ne and s n separate the basin into ten secondary tectonic units with five depressions and five highs taking into account the seismic reflection data collected during the 1987 survey by the shiyan ii and the geological information available from earlier work this paper elucidates our understanding of the sequences division and tectonic subdivision and of the formation evolution and oil and gas prospects of the zengmu basin

the role of the east asian active margin in widespread extensional and strike slip deformation in east asia east asia is a region of widespread deformation dominated by normal and strike slip faults deformation has been interpreted to result from extrusion tectonics related to the india eurasia collision which started in the early eocene in east and se china however deformation started earlier than the collision latest cretaceous to palaeocene suggesting that extrusion tectonics is not the only driving mechanism for east asia deformation it is suggested that the east asian active margin has influenced deformation in east asia significantly along the margin cenozoic back arc extension took place behind several adjoining arcs implying eastward rollback of the subducting slab and collapse of the overriding plate towards the retreating hinge line we show that extension took place along a c 7400 km long stretch of the east asian margin during most of the cenozoic physical models are presented simulating overriding plate collapse and back arc extension the models reproduce important aspects of the strain field in east asia for geometrical and rheological conditions scaled to represent east asia modelling shows that the active margin can be held responsible for deformation in east asia as far west as the baikal rift zone located c 3300 km from the margin

comparison of model and observational ocean circulation climatologies for the new zealand region 1 primitive equation three dimensional regional models driven by global models can be used to generate climatologies of the ocean circulation with 1 12 resolution these model climatologies begin to resolve the coastal circulation and it is appropriate to ask whether they are adequate to replace observational climatologies we compare circulation climatologies derived from a z coordinate 36 vertical layer model run with three different diffusivities with an observational climatology csiro atlas of regional seas cars and with surface velocities derived from lagrangian drifters deployed under the global drifter program gdp all the climatologies capture the major features in the mean circulation south of the chatham rise and east of new zealand the model climatologies agree better with gdp than does cars north of the chatham rise the models overestimate the strength of the east cape eddy wave number spectra from the models suggest that instability processes which are important in the mean are captured with diffusion less than 25 m2 s 1 the model with lowest diffusion may be providing the best estimate of the mean circulation but at the expense of numerical instability

currents associated with the quasi stationary jet separated from the kuroshio extension abstractthe hydrographic structure of a quasi stationary jet separated from the kuroshio extension a phenomenon that possibly leads to deepening of the winter mixed layer is revealed via intensive observations using a conductivity temperature depth profiler and a ship mounted acoustic doppler current profiler adcp carried out in september 2009 data collected from profiling floats set to drift isopycnal layers and time series of sea surface buoys and satellite altimeters were also analyzed to understand the continuity water characteristics and time variation of the jet although the flow field was complex due to disturbances such as energetic eddies the jet transported subtropical water to the downstream northeastern observation region in a layer shallower than 400 dbar and its highest velocity was concentrated in the mid and deep layers 0 30 m s 1 at the sea surface and 0 05 m s 1 at 800 m depth the velocity axes of the jet detected from the satellite data corresponded to those detected th