an outline of the plate tectonics of china china is principally a part of the eurasian plate but the margins of the indian and philippine sea plates are involved in the himalayas and in the coastal range of taiwan respectively within the eurasian plate the cathaysian paleoplate is separated from the angaraian paleoplate by the junggar hegen suture which contains paleozoic ophiolites and rare blueschists the three microplates of the cathaysian paleoplate consist of precambrian cratons and or phanerozoic accretionary fold belts these coalesced precambrian cratons record at least six stages of intense orogeny before cratonization the paleozoic to cenozoic accretionary fold belts of china can be correlated with similar events now found in west pacific andean and atlantic type active continental margins ophiolites occupying many of these tectonic zones provide evidence for the age and igneous history of oceanic crust formed during the paleozoic to cenozoic the presence of blueschist in some of these chinese sutures reveals evidence of large scale subduction and tectonic exhumation during consolidation of the eurasian plate cenozoic collision of the eurasian and indian plates produced deformation and uplift of the himalayas strongly influencing the tectonics of western china in contrast mesozoic tertiary evolution of eastern china is typical basin range geology similar to that of the western united states which included development of deep sedimentary basins along with calc alkaline plutonic and volcanic activity associated with crustal thinning and high heat flow the complicated tectonic evolution of china is greatly illuminated by the presence of ophiolites and blueschists in proterozoic to tertiary convergent boundaries these petrotectonic assemblages provide evidence of an extremely mobile history of plate movement in china

three dimensional aspects of the seasonal heat balance in the gulf of california previously unresolved three dimensional aspects of the time mean as well as the annual and semiannual cycles of the heat transport are studied in the gulf of california using a minimal box model suggested by the hydrographic data at the very least three horizontal domains are needed for the model a shallow region north of the big islands a deep region identifiable with the ballenas channel and another deep region spanning the rest of the gulf south of the archipelago only one vertical layer is considered in the northern region whereas two layers are taken into account in the other two regions out of all of the possible heat exchanges among the various boxes of the model the least flux variance solution is considered the annual mean heat entering the surface in the northern region is exported in almost equal amounts to the ballenas channel and the southern region ballenas channel in turn exports heat to the southern region mainly through the lower layer producing a transversal asymmetry of the mouthward flux into the upper layer at the mouth the heat is exported to the pacific ocean largely through the upper layer both the annual and semiannual amplitude of the exchanges between all regions are as important as the annual average except at the mouth of the gulf where the semiannual component is not statistically relevant the pacific ocean fluxes estimates at the annual frequency agree well with those produced by a baroclinic wave which has been shown to explain a big deal of the thermodynamics of the gulf the annual mean vertical flux per unit horizontal area in the ballenas channel is much larger than that in the southern region this reinforces previous speculations that mixing processes in this region are very important a depth independent eddy diffusivity parameterization suggests that diffusion might not be invoked to explain the annual mean vertical flux in the ballenas channel

a three dimensional model of the mean and seasonal circulation of the gulf of california 1 the mean and seasonal circulation of the gulf of california is simulated with a three dimensional numerical model forced by the pacific ocean through specifying the sea level the temperature and the salinity fields at its entrance at the sea surface the wind and the heat and freshwater fluxes are specified the model reproduces the observed mean and seasonal variability of sea level of heat and salt balances and the sea surface temperature sst climatology it also reproduces the general surface circulation of the northern gulf which consists of a seasonally reversing basin wide gyre it is found that tides and heat fluxes are both indispensable to reproduce the spatial structure and temporal evolution of the sst tides provide the mixing to upwell the cooler subsurface waters in the large islands area and the heating from the surface raises the sst the general circulation of the southern part of the gulf is due to the wind and the pacific forcing in the ekman layer two periods of anticyclonic circulation and one cyclonic per year occur below this layer two cyclonic periods develop in the northern part the tides play an important role in producing mean residual currents and both tides and winds compete against the pacific forcing to produce a cyclonic and anticyclonic circulation once a year contrary to conclusions of previous studies the thermohaline circulation is found to be unimportant in the gulf

seasonal gyres in the northern gulf of california abstract the circulation pattern in the northern gulf of california based on drifting buoys and hydrographic observations can be explained using the results of a linear two layer primitive equations model forced at the annual frequency by the pacific ocean wind stress and heat flux through the surface the modeled surface circulation consists of a cyclonic gyre from june to october and an anticyclonic gyre from december to april both located in the central region of the northern gulf of california which includes angel de la guarda island the maximum intensities of the gyres occur in august and february respectively with values of surface velocities of 65 cm s 1 in agreement with the observations and very low opposite velocities in the bottom layers may and november are transition months in which both gyres can be observed finally in june july or december january the growing gyre is still connected with the rest of the gulf of california through the narrows between tiburon island san este

carboniferous and early permian biogeography during the carboniferous changes in the biogeographical distribution of shelf dwelling benthic marine invertebrates were made in response to changes in physical paleogeography and climatic variations calcareous foraminifers and bryozoans are principal examples of the general trends during the early carboniferous which show that tournaisian and early and middle visean faunas were broadly cosmopolitan in a circumequatorial belt and that latitudinal diversity gradients were relatively minor during the later part of the visean and early part of the namurian the hercynian orogeny caused by the collision of euramerica with gondwana disrupted these cosmopolitan equatorial faunal patterns this was also a time of progressively cooler temperatures throughout the world of dramatic reduction in faunal diversity and of high rates of extinction of both species and genera during middle carboniferous time strongly provincial faunas were common spasmodic but limited dispersals gave a few widespread genera significantly different stratigraphic ranges in different provinces so that tethyan and non tethyan distributions are recognizable faunal diversity gradually increased during the middle carboniferous and then declined at the end of the epoch with additional high levels of extinction of species and genera during late carboniferous time several new faunal lineages became well established some filled vacant ecological niches however others took advantage of the increase in the number of niches that became available because of gradually warming climates provinciality continued to be pronounced diversity gradually increased and continued to do so through the early permian

internal structure of sst features in the central gulf of california abstract closely spaced xbt and ctd data were used to study the sub surface structure of features observed in satellite avhrr sea surface temperature sst images of the gulf of california gc such as fronts jets and gyres the lowest ssts in the gc are found around the midriff islands and especially over the sills because of strong mixing from tidal currents and breaking internal waves this minimum sst area is limited to the south and north by sharp sst fronts which frequently show convolutions gyres and filaments a vertical section of temperature along the gulf length shows that about 300 km south of the sills the isotherms begin to spread out in the vertical reducing stratification the thermocline isotherms begin surfacing about 100 km south of the sill forming the sst minimum area which has a maximum temperature difference of 6 c with waters to the south and a horizontal sst gradient of 0 05 c km 1 the evolution and subsurface structure of a cool filament apparently originated as an instability of the sst front was intensely sampled satellite images show that its head advanced due south at about 0 5 ms 1 along the edge of a pool of warm surface water about 110 km in diameter the thermocline below the warm pool was raised at its edge and some isotherms reached the surface producing the cool filament the tilt of the temperature salinity and density isolines at the edge of the warm pool produced a geostrophic jet adjacent to the cool filament and just inside the warm pool with maximum speed 0 5 ms 1 and extending down to 80 m the filament lasted about 10 days its width was 30 km and it reached a maximum length of 120 km the volume transport of the jet in the top 100 m was around 0 7 sv

mesozoic overthrust tectonics in south china whether south china was a platform or a para platform after the mid paleozoic deformation or whether the mountains of huanan south china form a mesozoic collision type orogen depends upon whether the ophiolite melange in the yangtze region is precambrian basement or was overthrust onto a foreland thrust belt during the mesozoic this paper presents evidence of tectonic windows under the melange and basement klippes above the melange in the yangtze region

thermohaline circulation in the gulf of california the gulf of california a narrow semienclosed sea is the only evaporative basin of the pacific ocean as a result of evaporative forcing salinities in the gulf are 1 to 2 higher than in the adjacent pacific at the same latitude this paper examines the thermohaline structure of the gulf and the means by which thermohaline exchange between the pacific and the gulf occurs over time scales of months to years in addition to evaporative forcing air sea heat fluxes and momentum fluxes are important to thermohaline circulation in the gulf from observations presented here it appears that the gulf gains heat from the atmosphere on an annual average unlike the mediterranean and red seas which have comparable evaporative forcing as a result outflow from the gulf tends to be less dense than inflow from the pacific winds over the gulf change direction with season blowing northward in summer and southward in winter this same seasonal pattern appears in near surface transports averaged across the gulf the thermohaline circulation then consists of outflow mostly between about 50 m and 250 m inflow mostly between 250 m and 500 m and a surface layer in which the direction of transport changes with seasonal changes in the large scale winds using hydrographic observations from a section across the central gulf total transport in or out of the northern gulf is estimated to be 0 9 sv heat gain from the atmosphere is estimated to be 20 to 50 w m 2 and evaporation is estimated to be 0 95 m yr 1 these estimates are annual averages based on cruises from several years seasonal variations in thermohaline structure in the gulf are also examined and found to dominate the variance in temperature and density in the top 500 m of the water column salinity has little seasonal variability but does exhibit more horizontal variablility than temperature or density major year to year variations in thermohaline structure may be attributable to el nino southern oscillation events

climate forcing primary production and the distribution of holocene biogenic sediments in the gulf of california abstract the gulf of california is a marginal seaway under the influence of a monsoon climate that produces cool dry winters and warm humid summers winds tidal mixing and coastal trapped waves forced by climate and the pacific ocean control nutrient advection and primary productivity pp strong northwest winds from the subtropical east pacific high pressure system begin in november and last until april and drive coastal upwelling along the mainland margin especially in the central and southern gulf in the northern gulf particularly around the midrift island tidal mixing and turbulence occurs year round advecting nutrients into the mixed layer and high productivity during summer and early fall months winds are variable of less intensity and mainly blow cross basin except in the most northern gulf summer pp is generally low in the central and southern gulf except along the mainland where coastal trapped waves associated with tropical surges and hurricanes generate mixing over the continental shelf mesoscale eddies or gyres often associated with jets and filaments extend to depths of 1000 m and transport nutrient enriched upwelled waters and plankton detritus across the gulf the largest and most persistent gyres rotate in an anti cyclonic direction east to west and are a principal source of the plankton export to the peninsula margin two major biogenic sediment patterns are present in core top sediments hemipelagic biosiliceous rich muds are accumulating beneath upwelling areas of high productivity in the central gulf and along the mainland margin calcium carbonate and organic carbon rich oc sediments are concentrated along the peninsula margin generally beneath lower productivity waters with the highest oc content in areas with the lowest productivity the high uniform biosiliceous content in guaymas basin extending southward into carmen basin reflects the redistribution by mesoscale gyres of phytoplankon debris produced in mainland coastal upwelling and tidally forced areas around the midrift islands holocene biogenic patterns are similar to the present day with the major difference in rates of accumulation phytoplankton production prior to about 8200 yr bp was significantly higher in the central and southern gulf decreased though the mid holocene and has been reasonably steady for the past 2500 yr the strong north south and east west gradients in present day phytoplankton productivity patterns are also reflected in the holocene sediment record a series of depositional cycles occur in the biogenic record with the strongest peaks of variability at about 150 144 18 200 198 5 and 350 350 40 yrs longer periodicities are present prior to 3200 yr bp but the 350 yr cycle dominates in the late holocene where it is best expressed as productivity dissolution cycles in the carbonate record

geothermal fluid chemistry of the orakeikorako field new zealand abstract samples of water and steam from natural discharges in the orakeikorako geothermal area of the taupo volcanic zone have been analyzed for their chemical and stable isotopic components the waters are near neutral with chloride contents less than 400 mg kg a model of the subsurface hydrology based upon well measurements and chemical and isotopic measurements has been developed in which the dilute waters discharged at the surface are considered to result from the dilution of deeper fluids which may have temperatures as high as 280 c in the northern parts of the field waters with relatively lower chloride and higher bicarbonate composition have further diluted the rising fluid there is no evidence that local lake or river waters have changed the field character or water composition significantly since the river water level was raised

the effect of the seasonal variation of stratification on the circulation of the northern gulf of california abstract direct current measurements reveal that the circulation of the northern gulf of california in the annual timescale consists of a cyclonic basinwide gyre 0 35 m s 1 that lasts from june to september 4 months and an anticyclonic gyre 0 35 m s 1 lasting from november to april 6 months the transitions between regimes take about three weeks each the hypothesis that the difference in duration of the two circulation regimes is due to the seasonal variation of stratification of the water column is explored by simulations with a nonlinear two layer numerical model of circulation and thermodynamics that includes vertical mixing parameterized as an entrainment velocity the model results agree remarkably well with the observations considering its simplified vertical structure in addition the model predicts a net circulation consisting of an anticyclonic gyre of 0 05 m s 1 with a corresponding average concavity of the interface and a two layer exchange through the main channels of the arc

phylogeny and paleobiogeography of triassic sauropterygia problems solved and unresolved abstract this comparison of the geographic and stratigraphic distribution of the secondarily marine stem group sauropterygian reptiles from the triassic with the phylogenetic relationships within this group indicates an incompleteness of the fossil record for the clade of almost 50 which limits the reconstruction of the biogeographical history of its component taxa given their restriction to nearshore habitats or shallow epicontinental seas it is unlikely that stem group sauropterygians had the capacity for trans oceanic dispersal dispersal along coastlines may have been a component of their biogeographical history however as is indicated by the immigration of sauropterygians into the anglo germanic basin at the transition of the lower to middle triassic and by the population of the alpine triassic by sauropterygians after the evolution of the appropriate intraplatform basin habitat during the middle triassic conversely trans panthalassan relationships of pistosaur sauropterygians appear best explained as a consequence of vicariance due to the accretion of exotic terranes at opposite margins of the pacific basin a vicariant event resulting from the opening of the southern branch of the neotethys may also account for the sister group relationships of nothosaurs from the northern gondwanan shelf and the anglo germanic basin

the chemistry of geothermal waters in iceland iii chemical geothermometry in geothermal investigations abstract new data from geothermal wells in iceland have permitted empirical calibration of the chalcedony and na k geothermometers in the range of 25 180 c and 25 250 c respectively the temperature functions are t c 1112 4 91 log sio 2 273 15 t c 933 0 993 log na k 273 15 concentrations are expressed in ppm these temperature functions correspond well with the chalcedony solubility data of fournier 1973 and the thermodynamic data for low albite microcline solution equilibria of heloeson 1969 a new co2 geothermometer is proposed which is considered to be useful in estimating underground temperatures in fumarolic geothermal fields its application involves analysis of co2 concentrations in the fumarole steam the temperature function which applies in the range 180 300 c is logco2 37 43 73192 t 11829 103 t2 0 18923t 86 187 logt where t is in k and co2 in moles per kg of steam

a numerical simulation of the two and three dimensional lagrangian circulation in the northern gulf of california the surface circulation in the northern gulf of california is dominated by a cyclonic gyre during summer and an anticyclonic gyre during winter the associated 3d lagrangian circulation is calculated and compared with that detected by surface floats by inhibiting vertical advection in a three dimensional 3d numerical model in general the 3d circulation follows the same horizontal paths as in the two dimensional 2d case but with vertical excursions along the trajectories however in some areas especially those close to the coasts which represents 20 of the study area the vertical displacements cause the paths of both cases with and without vertical advection to differ considerably thus resulting in different destinations for the particles this finding is of relevance for the fate of larvae or contaminants in the area which so far had been studied on the basis of 2d results alone

diurnal cycle of surface flows during 2004 name and comparison to model reanalysis abstract during the north american monsoon experiment name an unprecedented surface dataset was collected over the core monsoon region observations from 157 surface sites in this region along with twice daily quick scatterometer quikscat oceanic winds were quality controlled and processed into a gridded dataset covering the domain 15 40 n 90 120 w at 1 h 0 25 resolution for the period from 1 july to 15 august using this dataset the mean temporal variability and diurnal characteristics of the monsoon surface flow are documented with detail not previously possible being independent of model data over land these objectively analyzed surface products are compared to similar analyses from a special north american regional reanlysis for name narr name that was produced for the same period observed surface fields indicate that a robust land sea breeze circulation is present over most of the gulf of california goc region in response to the strong diurnal heating of landmasses on both sides

la icp ms analysis of rare earth elements in marine reptile bones from the middle triassic bonebed upper silesia s poland impact of long lasting diagenesis and factors controlling the uptake abstract the rare earth elements ree contained in fossil bones are widely used for provenance and palaeoenvironmental studies earlier works suggested that the ree uptake is limited to early diagenesis but more recent research provided evidence of long term open system diffusion in fossil bones we analysed thin walled reptile bones all collected from the same middle triassic 245 ma marine bonebed comprising vertebrate remains of likely different ages to check the influence of the long term diagenesis on the concentrations of ree in terms of impact of pore water the upper parts of the bones are contained in a low permeability crinoidal limestone whereas their lower parts have been affected by diagenetic fluids for a long time we measured ree and other trace element contents in 29 bones using la icp ms totally 660 spots in 45 depth profiles neither the absolute concentrations of the ree and the ree intra bone paas normalised patterns nor the inter element ratios and the la ce and eu anomalies appear useful to distinguish between the likely older and younger bones in the bonebed the mree n enrichment combined with the flat intra bone distributions of the ree lead to conclusion that ree fractionation and substitution for ca were the most important processes responsible for the selective uptake the low permeability host rock and diagenetic fluids had a significant impact on the trace element uptake and their intra bone distribution patterns the lower parts of the bones that likely had a long lasting contact with the diagenetic fluids reveal a relative enrichment in the ree and their easier diffusion into the bone centres the ability of fossil bones to incorporate trace elements over a long time span strongly limits the usage of particularly the older samples for provenance and palaeoenvironmental reconstructions additionally the presented new analyses fill the gap between the available databases of trace element concentrations in fossil bones with regard to middle triassic samples

summer generation of the southern gulf of california eddy train 1 ocean color and sea surface temperature satellite observations show the existence of a series of anticyclonic eddies along the axis of the southern gulf of california sgoc to investigate the summer generation of these eddies a regional version of the hybrid coordinate ocean model hycom has been configured for the goc and has been nested inside the global model a suite of experiments using the nested goc model was developed and used to isolate the effects of the local wind and the effects of the oceanic remote forcing on the generation of the sgoc eddies the results indicate that the local wind is not essential for the generation of these eddies rather it is the oceanic remote forcing in the sgoc the monthly variability of the currents and sea surface height is mainly due to the deterministic near coastal poleward eastern boundary currents pebc the interaction of the pebc with the topographic irregularities the capes at topolobampo and cabo lobos and the ridges extending offshore from the entrance of the san lorenzo and sinaloa rivers generates the sgoc eddies the northward upper ocean transport induced by the pebc includes two maximums one in may june and the other in december during the summers of 1999 and 2004 the pebc were intensified by the arrival of equatorially originated downwelling coastally trapped waves ctws which contributed to the generation of the sgoc eddies the summer 2004 ctw increased the northward upper ocean transport by 2 sv this particular ctw was measured by several tide gauges located along the coast

the triassic u pb age for the aquatic long necked protorosaur of guizhou china the ancient marine limestone beds of the upper part of the guanling formation panxian county guizhou province sw china yielded a wide range of high diversity well preserved marine reptiles such as the fully aquatic protorosaur with an extremely long neck dinocephalosaurus orientalis the oldest mixosaurid ichthyosaurs and lariosaurs however there is no precise isotopic age to study the intriguing origin evolution and emigration history of the important fauna we report a sensitive high resolution ion microprobe shrimp u pb zircon age for a volcanic tuff bed within the upper part of the guanling formation the result indicates that the age of the fossil horizon is 244 0 1 3 ma 14 ma earlier than the previously estimated age based on conodont evidence we consider that the marine reptiles had a relatively rapid evolution during middle triassic time some 8 ma after the end permian mass extinction

surface heat flux in the northern gulf of california recent coastal meteorological data 1979 1986 are used to evaluate the seasonal cycle of surface heat fluxes in the northern gulf of california although net heat loss occurs from october to january the annual mean of the net surface heat flux was found to be into the sea 69 w m 2 near the coast and 83 w m 2 offshore with a mean evaporation rate 0 9 m yr 1 these results require an oceanic export of heat and salt out of the northern gulf to achieve a balance and imply that the annual mean thermohaline circulation must have an inflowing component at depth thus enriching the central and northern parts of the gulf these results differ from previous meteorological estimates which suggested a net surface heat loss but confirm those based on hydrographic data

residual circulation and tidal stress in the gulf of california 1 results of a three dimensional nonlinear barotropic shelf model are used to study the effect of the m2 tidal stress on the residual current in the gulf of california the tidal stress summarizes the nonlinear interactions and forces the residual circulation it is calculated following the method developed by nihoul and ronday 1975 the vertical structure of the tidal stress reveals clearly the zones where the interaction between tidal currents and the basin geometry is strong the highest values of tidal stress were found over the salsipuedes sill and in the ballenas channel in the central archipelago and in the colorado river delta relatively high values of tidal stress were also found in deeper layers in the southern part the high tidal stress values coincide well with the anomalous cold water patches observed in the archipelago area attributed to tidal mixing the calculated residual currents show a maximum of about 15 cm s 1 in the upper layers in the archipelago area at subsurface layers an anticyclonic circulation is observed divergence patterns in the upper layers suggest that m2 tide residuals contribute to significant upward movements of water on the west side of tiburon island this barotropic process may contribute to the generation of the observed cold patches

a new age constraint for the early triassic alcova limestone chugwater group wyoming abstract the alcova limestone is a widely exposed but poorly studied triassic unit found throughout wyoming although it is used as a regional lithostratigraphic marker bed the age of the limestone is not well constrained and contention regarding its depositional nature marine vs non marine saline lake has not been adequately resolved although the marine hypothesis is more widely accepted currently its age is based on the occurrence of a single basal pistosaurid corosaurus alcovensis we provide the first 87 sr 86 sr analysis of the alcova limestone the data strongly support a marine origin for this unit furthermore the data provide an age range based on their placement on the marine strontium curve that limits the deposition of the alcova limestone to the latest olenekian to earliest anisian early triassic middle triassic boundary this placement is consistent with the timing of the spathian regression recorded in other transitional marine to non marine strata of the western usa

surface circulation in the gulf of california in summer from surface drifters and satellite images 2004 2006 surface drifters released in the gulf of california between june 2004 and august 2006 are used to describe the surface circulation in late spring and summer in the june to september mean there was a poleward coastal current on the shelf and slope of the mainland side of the gulf with mean speed 0 3 m s it reached the northern gulf and joined the cyclonic circulation typical of this zone in summer in the western half of the southern gulf the drifters presented recirculating currents that are due to mesoscale eddies that appear to dominate the surface circulation in summer in june 2004 the coastal current presented an enhancement event with mean speed around 0 60 m s and maximum 0 80 m s it took 20 days for a particular drifter to travel the 1000 km from the gulf entrance to the head this strengthening of the coastal current was apparent in chlorophyll a and sst satellite images the drifters following closely the intrusion of warm chlorophyll poor surface water from outside the gulf the drifters and the satellite images suggest that the current enhancement event lasted less than a month this mesoscale event was linked with a mesoscale remote forcing in the tropical pacific coast and with a mesoscale local forcing of the wind these events seem to occur every year and are probably important in carrying organisms and properties from the entrance to the whole length of the gulf

surface dispersion in the gulf of california abstract surface dispersion is measured in the gulf of california by means of argos drifters released along this semi enclosed elongated basin first basic one particle statistics lagrangian scales absolute dispersion and diffusion coefficients are estimated along and across the gulf absolute dispersion shows a nearly ballistic regime during the lagrangian time scale t 2 where t is time during the subsequent 30 days absolute dispersion enters a random walk regime t along the gulf while being saturated across the basin due to the lateral boundaries secondly the analysis is extended to two particle statistics relative dispersion between pairs of drifters and finite scale lyapunov exponents fsle relative dispersion is nearly exponential in both directions during the first few days though evidence is not conclusive during the subsequent 30 days it grows as t 1 5 along the gulf while being saturated across the basin again it is shown that relative dispersion along the gulf is proportional to t 3 where t represents a shifted time that depends on the initial separation of the particles this form of the richardson regime is consistently measured for particles that are sufficiently separated 30 km or more the richardson regime is verified with the fsle for particle separations ranging from 30 to 140 km approximately the obtained dispersion properties are discussed in terms of the main circulation features within the basin such as mesoscale vortices that occupy the width of the gulf these structures might retain buoys during days or weeks thus preventing or delaying further displacements and therefore affecting the particle dispersion the vortices are also an important mechanism to translate particles across the gulf between the peninsula and the continent thus promoting the saturation of dispersion along this direction

major hydrogeochemical processes in the two reservoirs of the yangbajing geothermal field tibet china abstract the yangbajing geothermal field with the highest reservoir temperature in china is located about 90 km northwest to lhasa city capital of tibet where high temperature geothermal fluids occur both in shallow and deep reservoirs the geophysical survey by the indepth international deep profiling of tibet and the himalayas project group proved the existence of magmatic heat source at yangbajing in the study area the hydrochemistry of cold surface waters and groundwaters and that of thermal groundwaters from both reservoirs are distinctively different however analysis of the relationship between enthalpy values and cl concentrations of cold groundwaters and geothermal fluids indicates that the geothermal fluids from the shallow reservoir were formed as a result of mixing of cold groundwaters with geothermal fluids from the deep reservoir in other words the geothermal fluids from the deep reservoir flowed upwards into the shallow reservoir where it was diluted by the shallow cold groundwaters to form the shallow geothermal fluids with much lower temperature a binary mixing model with two endmembers the cold groundwaters and the deep geothermal fluids was proposed and the mixing ratios for the geothermal fluid from each shallow well were estimated using the mixing ratios the concentrations of some constituents in shallow geothermal fluids such as as b sio 2 so 4 2 and f were calculated and their differences with the actual concentrations were estimated the results show that the differences between estimated and actual concentrations of as and b are small the average absolute values being only 1 9 and 7 9 respectively whereas those of sio 2 so 4 2 and f are much bigger indicating that other hydrogeochemical processes are responsible for the concentrations of these constituents it is postulated that sio 2 precipitation due to water temperature decrease h 2 s oxidation and ion exchange between oh in geothermal waters and exchangeable f in fluoride bearing silicate minerals during the geothermal fluid upflow might be the causes for the observed concentration differences

water mass formation in the gulf of california the gulf of california is a long narrow marginal sea lying between the baja california peninsula and the mainland of mexico air sea fluxes of heat and moisture in the gulf are enhanced because of geographical isolation from the pacific provided by the mountainous baja california peninsula in the northern gulf annual evaporation rates are about 1 m y 1 unlike most evaporative basins however the gulf gains heat from the atmosphere at an annual average rate of 20 to 80 w m 2 bray 1988 given the unusual air sea forcing of the gulf what form or forms should water mass formation take the annual moisture loss and heat gain require that high salinity surface water be transported downward to an intermediate depth and that cold fresh inflow be transported upward to an intermediate depth this is accomplished through several mechanisms 1 winter convection this occurs only in a limited geographical region the wagner basin of the far northern gulf except in el nino southern oscillation years when convection appears to be more widespread 2 dispersion of convected water in small eddylike features this occurs within a large scale southward transport possibly driven by the large scale density gradient associated with atmospheric fluxes 3 an anticyclonic circulation in the northern gulf this is found south of the convection region and transports high salinity water off the shallow shelves and to substantial depths where it may mix with water of central gulf origin 4 tidal mixing most of the energy available for mixing in the northern gulf derives from the tides in particular tidal mixing over the sill in the island region is responsible for the substantial reduction in salinity of northern gulf waters as they enter the central gulf

tectonics of south china key to understanding west pacific geology abstract south china is not a post caledonian platform but a composite of orogenic belts this late proterozoic mesozoic orogen is a collage of three continental fragments the three blocks are yangzi huanan and dongnanya and they are separated by the banxi nanpanjiang formerly xianggangzhe and gunanhai suture zones yangzi was separated from gondwanaland during late precambrian when an open ocean called banxi was present between the two continents tectonic processes at an active margin during sinian and early paleozoic time led to the genesis of an accretionary wedge complex the banxi melange and the huanan flysch nappes on the northern margin of huanan which was then the northern margin of the gondwana continent reorganization of plates during the devonian suspended subduction at the huanan active margin huanan was uplifted and unconformably overlain by transgressive deposits of devonian and or carboniferous age a remnant ocean the nanpanjiang sea still existed between yangzi and huanan and deep water sedimentation continued both at the southern margin of yangzi and at the northwestern margin of huanan the latter again became an active margin during late paleozoic when permian and triassic flysch sediments were deposited in foredeeps ahead of advancing nappes huanan and yangzi collided during the triassic and resulted in the deformation of the passive margin of the latter to form the yangzi deformed belt huanan was separated from a more southerly continent dongnanya in the devonian by seafloor spreading which created a late paleozoic and early mesozoic ocean gunanhai ocean a continuously deposited sequence ranging in age from devonian to triassic was laid down on the southern passive margin of huanan on the other side of the ocean the dongnanya permian strata include glacial marine deposits of gondwanaland affinity dongnanya became separated from gondwanaland during the late permian when it marched northward to be reunited with huanan the huanan passive margin sequence was deformed by folding and overthrusting after the late mesozoic collision of huanan and dongnanya scattered outcrops of the suture melange resulting from this collision occur at a few localities in coastal fujian dongnanya in our model was the mesozoic continent of southeast asia peripheral to mainland asia this may or may not have been the eastern continuation of the microcontinent sibumasu siam thailand burma malaysia sumatra the collision of dongnanya and asia gave rise not only to the gunanhai melange of coastal fujian but also to the ophiolite melanges parts of which are present in taiwan tailuko the philippines and western malaysia

modeling the seasonal and interannual variability of the northern gulf of california salinity 1 the 7 years 2003 2009 of output from a regional version of the hybrid coordinate ocean model hycom nested in global hycom are used to study the seasonal and interannual variability of the salinity in the northern gulf of california ngoc previous studies illustrate that the ngoc is characterized by an annual evaporation of 0 9 m yr this evaporation generates high sea surface salinity sss water which reaches a maxima in the ngoc 37 and decreases to 35 toward the entrance of the gulf of california the ngoc surface water is interannually modulated by fluctuations in evaporation and by fluctuations in the low salinity water transported into the region by poleward eastern boundary currents the fluctuations in the transport of low salinity water are linked to the arrival of equatorially originated coastally trapped waves the crucial role of the transport of low salinity water for the interannual variability of sss is illustrated by the 2006 and 2008 fall seasons which include the lowest simulated salinity of the period 2003 2009 the lowest salinity in 2006 and 2008 cannot be explained solely by evaporation because 2006 was characterized by the largest evaporation of the period 2003 2009 however the presence of the lowest salinity environment can be attributed to the evaporation in conjunction with the largest upper ocean transport of low salinity water carried to the ngoc by the 2006 and 2008 coastally trapped waves intensified poleward eastern boundary currents

genesis of the lower triassic bonebeds from gogolin s poland the impact of microbial mats on trapping of vertebrate remains abstract three bone bearing horizons consisting of seven bone bearing beds with fish and reptile remains were recently discovered in the uppermost rot buntsandstein lower triassic peritidal and shallow marine carbonates in the vicinity of gogolin s poland the aim of this study is to recognize the genesis and depositional environments of the bonebeds detailed fieldwork microfacies analysis and sem eds analysis reveal that the vertebrate remains occur to a great extent alongside evidence for former microbial activity the reptile remains represent at least dactylosaurus and nothosaurus sauropterygia genera while the fish remains belong to the chondrichthyes and actinopterygii the vertebrate remains were deposited in a transitional zone between the costal sabkha and the epicontinental sea the first bone bearing horizon originated in the most landward setting in the uppermost intertidal zone likely at the margins of a pond or coastal lagoon the second bone bearing horizon was formed in the upper intertidal zone the vertebrate remains of the third bone bearing horizon were accumulated in two different settings in the lower intertidal zone in a small palaeopond and in the subtidal zone in a protected back shoal lagoon three bone accumulations occur within planar stromatolites while the other bone bearing beds reveal more indirect evidence for former microbial activity in our opinion the presence of the sticky microbial mats in the intertidal settings was the crucial factor that allowed the establishment of and controlled these accumulations of vertebrate remains the soft gluey substrates trapped vertebrate remains that were transported across them once trapped the vertebrate bioclasts were efficiently immobilized and thus protected against damage due to sedimentological agents the lack of any orderly arrangement of the vertebrate bioclasts suggests that they may have been delivered to the individual mat surfaces by diverse media from various directions and also at different times

ocean color observations of eddies during the summer in the gulf of california 1 using seawifs ocean color satellite images collected during 1997 2001 a series of eddies have been observed in the gulf of california these eddies are not clearly seen in the summertime sea surface temperature images the surface circulation between the midriff islands and the mouth of the gulf appears to be dominated by this series of eddies that have an alternating sense of rotation an eddy pair is observed to extend from cabo lobos in each of the three years suggesting that the eddies are topographically locked the formation mechanism of the eddies remains unknown however we suspect the most likely mechanism includes baroclinic instabilities along the coast produced by interactions between coastally trapped waves and local wind driven currents

analysis of marrow cavity fillings as a tool to recognise diverse taphonomic histories of fossil reptile bones implications for the genesis of the lower muschelkalk marine bone bearing bed middle triassic żyglin s poland abstract the bone bearing bed from yglin s poland which likely represents the oldest lower muschelkalk accumulation of reptile remains in the se part of the germanic basin has been investigated in order to determine its genesis the basic methods were supported by petrographic analysis of the marrow cavity and large inter trabecular pore space fillings of fossil bones which was used to check its usefulness to identify the environments where the bones were initially deposited and to decipher taphonomic histories of the remains the bone bearing bed is a composite deposit which consists of three distinct layers from bottom to top micritic limestone mudstone bioturbated autochthonous mud crinoidal limestone grainstone to packstone calcirudite and shell rich limestone packstone to wackstone calcirudite the crinoidal limestone layer the main bone bearing bed is recognised as the proximal tempestite deposited in the mid ramp zone the petrographic analysis of the fillings reveals the prevalence of minute ostracod carapaces accompanied by other grains embedded together with micrite to microspar such compositions suggest that these sediments may have been inserted into the bone pore spaces in lagoons and tidal flat ponds features of some bones record their early diagenetic burial and lithification before the final redeposition the isopachous spar blocky spar and weathered pyrite document changes in the chemical composition of fluids that flowed into the bone interiors the burrow found in the marrow cavity of specimen iguam zov 7 provides evidence that some remains were inhabited by minute or juvenile invertebrates all recognised features indicate that both invertebrate and vertebrate bioclasts included in the tempestite were initially deposited in various settings of the carbonate ramp and in the end redeposited as a result of a heavy storm or a hurricane the examined bone bearing bed represents time averaged assemblage which originated due to hydraulic concentration of the vertebrate bioclasts the petrographic analysis of the fillings is a valuable tool to identify complex taphonomic pathways of vertebrate bioclasts

seasonal evolution of the geostrophic circulation in the northern gulf of california abstract an improved description of the seasonal variability of the geostrophic circulation in the northern gulf of california is obtained from a historical hydrographic database larger than in previous studies the evolution of the geostrophic circulation consists of a cyclonic summer period an anticyclonic winter period and two transition periods the cyclonic summer period lasts from june to september four months and is characterized by a strongly baroclinic cyclonic gyre which dominates the circulation the anticyclonic winter period starts in november and persists until april six months the anticyclonic geostrophic circulation is less robust than that in summer the transition periods take of the order of one month occurring around october and april may and are characterized by the simultaneous presence of both types of gyres empirical orthogonal function analysis shows a strong seasonal signal in the dynamic height for the first mode 97 2 of the total variance whose spatial structure is a closed gyre which oscillates between cyclonic during the summer months and anticyclonic the rest of the year the results strengthen and extend those from previous work based on analysis of hydrographic data on limited direct observations on satellite image analysis and on numerical modelling