boron isotope signatures in the coastal groundwaters of french guiana 1 drinking water used by the population of french guiana comes mostly from rivers and can induce major health impacts consequently groundwaters are being studied in terms of an alternative drinking water supply in this context boron isotopes were applied to the coastal aquifers to better constrain the water rock interactions we found that the 1 1 b signatures vary between 2 98 and 49 35 o in the groundwaters and between 36 35 and 42 41 o in the river waters and that the local seawater gave a value of 40 76 o we also noted an inverse correlation between groundwater ph and 1 1 b this relationship previously demonstrated experimentally is particularly well defined in the french guiana coastal aquifer because of the wide ph range 4 18 to 7 64 naturally present in the groundwaters it would appear that the variations in 1 1 b values are linked to water rock interaction processes e g dissolution precipitation of silicates

atmospheric and oceanic forcing of weddell sea ice motion the data from sea ice buoys which were deployed during the winter weddell sea project 1986 the winter weddell gyre studies 1989 and 1992 the ice station weddell in 1992 the antarctic zone flux experiment in 1994 and several ship cruises in austral summers are uniformly reanalyzed by the same objective methods geostrophic winds are derived after matching of the buoy pressure data with the surface pressure fields of the european centre for medium range weather forecasts the ratio between ice drift and geostrophic wind speeds is reduced when winds and currents oppose each other when the atmospheric surface layer is stably stratified and when the ice is under pressure near coasts over the continental shelves the spatial inhomogeneity of tidal and inertial motion effectively controls the variability of divergence for periods below 36 hours far from coasts speed ratios which presumably reflect internal stress variations in the ice cover are independent of drift divergence on the spatial scale of 100 km to study basin scale ice dynamics all ice drift data are related to the geostrophic winds based on the complex linear model thorndike and colony 1982 for daily averaged data the composite patterns of mean ice motion geostrophic winds and geostrophic surface currents document cyclonic basin wide circulations geostrophic ocean currents are generally small in the weddell sea significant features are the coastal current near the southeastern coasts and the bands of larger velocities of 6 cm s 1 following the northward and eastward orientation of the continental shelf breaks in the western and northwestern weddell sea in the southwestern weddell sea the mean ice drift speed is reduced to less than 0 5 of the geostrophic wind speed and increases rather continuously to 1 5 in the northern central and eastern weddell sea the linear model accounts for less than 50 of the total variance of drift speeds in the southwestern weddell sea and up to 80 in the northern and eastern weddell sea

the effect of ph and temperature on the isotopic fractionation of boron between saline brine and sediments the effects of ph and temperature on the adsorption distribution of boron in sediment and the boron isotopic fractionation factor between saline brine and sediment were studied the results show that the adsorption and isotopic fractionation of boron between saline brine and sediment are similar to that between seawater and marine or pure sediments in a certain ph range the adsorption distribution factor kd and isotopic fractionation factor of boron are controlled by the ph of the saline brine kd increases with ph while decreases an unusual aspect of this study was that 11b enrichment in the solid was seen during boron adsorption by clay at high ph these results have been used to study the distribution of boron isotopes in salt lakes of qaidam basin

wind and wave influences on sea ice floe size and leads in the beaufort and chukchi seas during the summer fall transition 2014 sea ice floe size distribution and lead properties in the beaufort and chukchi seas are studied in the summer fall transition 2014 to examine the impact on the sea ice cover from storms and surface waves floe size distributions are analyzed from medea landsat8 and radarsat 2 imagery with a resolution span of 1 100 m landsat8 imagery is also used to identify the orientation and spacing of leads the study period centers around three large wave events during august september 2014 identified by swift buoys and wavewatch iii model data the range of floe sizes from different resolutions provides the overall distribution across a wide range of ice properties and estimated thickness all cumulative floe size distribution curves show a gradual bending toward shallower slopes for smaller floe sizes the overall slopes in the cumulative floe size distribution curves from landsat8 images are lower than while those from radarsat 2 are similar to previously reported results in the same region and seasonal period the medea floe size distributions appeared to be sensitive to the passage of storms lead orientations regardless of length correlate slightly better with the peak wave direction than with the mean wave direction their correlation with the geostrophic wind is stronger than with the surface wind the spacing between shorter leads correlates well with the local incoming surface wavelengths obtained from the model peak wave frequency the information derived shows promise for a coordinated multisensor study of storm effects in the arctic marginal ice zone

oceanic anoxia at the precambrian cambrian boundary the precambrian cambrian pc c boundary separates fossils representing two discrete evolutionary phases the neoproterozoic soft bodied ediacarian biotas and cambrian small shelly faunas the biological discontinuity is suspected to have been a result of mass extinction however recent discoveries of the ediacarian biotas in cambrian sediments have led to an understanding that the faunal change was gradual through the pc c transition th u ratios which are high in oxidizing conditions and low in reducing conditions show a considerable positive correlation with 13c values at all studied sites of the pc c boundary this correlation indicates that reported 13c variation across the pc c boundary from numerous localities corresponds to redox variation in the depositional environment the negative 13c anomaly that occurs worldwide at the pc c boundary therefore corresponds to the widespread development of an oxygen deficient shallow marine environment this finding suggests that widespread oceanic oxygen deficiency which has been interpreted to reflect phanerozoic mass extinction events also occurred immediately before the cambrian explosion

a new perspective on southern hemisphere storm tracks abstract a detailed view of southern hemisphere storm tracks is obtained based on the application of filtered variance and modern feature tracking techniques to a wide range of 45 yr european centre for medium range weather forecasts ecmwf re analysis era 40 data it has been checked that the conclusions drawn in this study are valid even if data from only the satellite era are used the emphasis of the paper is on the winter season but results for the four seasons are also discussed both upper and lower tropospheric fields are used the tracking analysis focuses on systems that last longer than 2 days and are mobile move more than 1000 km many of the results support previous ideas about the storm tracks but some new insights are also obtained in the summer there is a rather circular strong deep high latitude storm track in winter the high latitude storm track is more asymmetric with a spiral from the atlantic and indian oceans in toward antarctica and a subtropical jet related lower latitu

studies of the antarctic sea ice edge and ice extent from satellite and ship observations abstract passive microwave derived ice edge locations in the antarctic are assessed against in situ observations from ships between 1989 and 2000 during the growth season march october the ship data agrees with satellite data very well with r2 values of 0 99 and 0 97 for the bootstrap and team algorithms respectively during the melt season november february the agreement is not so good with the passive microwave ice edge typically 1 2 of latitude south of the observations this is due to the low concentration and saturated nature of the ice and the r2 values for this period are 0 92 and 0 80 for the bootstrap and team algorithms respectively sensitivity studies show that such an offset in the summer ice edge location can cause significant errors in trend studies of the extent of sea ice cover in the southern ocean the passive microwave ice concentration at the ice edge observed by ship varies greatly averaging 14 for the team algorithm and 19 for the bootstrap comparisons between passive microwave data and sar landsat and ols data during the ice growth season show that while small scale details in ice edge location are lost the passive microwave data generally provide good and consistent representation of the higher resolution imagery

climate links and recent extremes in antarctic sea ice high latitude cyclones southern annular mode and enso in this article we study the climate link between the southern annular mode sam and the southern sea ice extent sie and discuss the possible role of stationary waves and synoptic eddies in establishing this link in doing so we have used a combination of techniques involving spatial correlations of sie eddy streamfunction and wind anomalies and statistics of high latitude cyclone strength it is suggested that stationary waves may be amplified by eddy anomalies associated with high latitude cyclones resulting in more sea ice when the sam is in its positive phase for most but not all longitudes a similar association is observed during enso la nina years although this synergy in the sam enso response may partially reflect preferential areas for wave amplification around antarctica the short extent of the climate records does not allow for a definite causality connection to be established with sie stronger polar cyclones are observed over the areas where the stationary waves are amplified these deeper cyclones will break up and export ice equatorward more efficiently but the near coastal regions are cold enough to allow for a rapid re freeze of the resulting ice break up we speculate that if global warming continues this same effect could help reverse the current positive antarctic sie trends once the ice gets thinner similarly to what has been observed in the northern hemisphere

observation of cyclone induced inertial sea ice oscillation in fram strait 1 in march 2007 the field campaign framzy took place in the region between spitsbergen and greenland one goal of the experiment was the observation of cyclone impact on ice drift by means of autonomous meteorological buoys deployed on sea ice on 23 march an intense cyclone of about 500 km diameter passed with about 20 m s from south to north over the ice covered part of the fram strait and induced strong inertial oscillations of the sea ice ice drift velocity fluctuations abruptly increased by a factor of three to values of more than 1 m s this was caused by a resonant wind forcing for almost three quarters of the inertial oscillation depending on the local ice conditions the oscillations lasted over a two to five days period the inertial oscillations caused ice drift divergence fluctuations of 6 10 6s 1 and a reduction of ice concentration by up to 11

boron isotopic compositions of brine sediments and source water in da qaidam lake qinghai china abstract the isotopic compositions of boron in da qaidam lake quinghai have been determined by using the technique of thermal ionization mass spectrometry of cesium tetraborate the brines are enriched in 11b with an average 11b of 5 49 2 34 compared with those of lake sediments and boron minerals produced by the lake the apparent isotopic fractionation factors between brine and lake sediments as well as boron minerals are 0 988 0 001 and 0 986 0 001 respectively source water 11b values range from 11 72 to 16 69 depending on their origin

influence of palaeoclimate and hydrothermal activity on organic matter accumulation in lacustrine black shales from the lower cretaceous bayingebi formation of the yin e basin china abstract the lacustrine black shales of the lower cretaceous bayingebi formation are an important hydrocarbon source rock in the yin e basin it is important to understand the mechanism of organic matter accumulation in these shales to reconstruct the palaeoenvironment and palaeoclimate in the early cretaceous in northwestern china and search for potential oil and gas resources based on petrological elemental geochemical and organic geochemistry analyses of typical field profile samples the influence of palaeoclimate and hydrothermal activity on organic matter accumulation in different sedimentary units unit i ii and iii is revealed unit ii has the highest total organic matter abundance tocavg 5 95 mainly type i kerogen lamalginite which is in the immature to low mature stage organic carbon isotope data 13corg element ratios sr cu and c value and weathering indexes including cia ciw and pia together revealed that the region experienced a semihumid to semiarid palaeoclimate in the middle of the early cretaceous the increase in rainfall in unit ii enhanced the abundance of lake algae and surrounding terrestrial vascular vegetation and elevated the lake level which contributed to adequate sources and favourable preservation conditions for organic matter accumulation several lines of evidence including high sulfur contents the combination of vein pyrite and micritic dolomite positive eu anomalies and element geochemical correlations confirm the existence of intermittent low temperature white smoker type hydrothermal activity the decrease of oxygen content in lake bottom water may be related to the input of hydrothermal fluid which provided necessary nutrient elements for biological productivity according to palaeontological and radioisotope dating data it can be inferred that the black shales of the bayingebi formation are the product of the combined effect of global palaeotemperature rise in the early aptian stage of the early cretaceous and intermittent low temperature hydrothermal activity

the supply and accumulation of silica in the marine environment rivers and submarine hydrothermal emanations supply 6 1 1014g sio2 yr to the marine environment approximately two thirds of the silica supplied to the marine environment can be accounted for in continental margin and deep sea deposits siliceous deep sea sediments located beneath the antarctic polar front convergence account for over a fourth 1 6 1014g sio2 yr of the silica supplied to the oceans deep sea sediment accumulation rates beneath the polar front are highest in the south atlantic with values as large as 53cm kyr during the last 18 000 yr siliceous sediments in the bering sea sea of okhotsk and subarctic north pacific accumulate 0 6 1014g sio2 yr or 10 of the dissolved silica input to the oceans the accumulation of biogenic silica in estuarine deposits removes a maximum of 0 8 1014g sio2 yr although estuarine silica versus salinity plots indicate extensive removal of riverine silica from surface waters the removal rates must be considered as maximum values because of dissolution of siliceous material in estuarine sediments and bottom waters siliceous sediments from continental margin upwelling areas e g gulf of california walvis bay or peru chile coast have the highest biogenic silica accumulation rates in the marine environment 69 g sio2 cm2 kyr despite the rapid accumulation of biogenic silica upwelling areas account for less than 5 of the silica supplied to the marine environment because they are confined laterally to such small areas

impact of a fram strait cyclone on ice edge drift divergence and concentration possibilities and limits of an observational analysis 1 this study aims at the determination of a fram strait cyclone track and of the cyclone s impact on ice edge drift divergence and concentration a 24 h period on 13 14 march 2002 framed by two radarsat images is analyzed data are included from autonomous ice buoys a research vessel special sensor microwave imager ssm i and quikscat satellite and the operational european centre for medium range weather forecasts ecmwf model during this 24 h period the cyclone moved northward along the western ice edge in the fram strait crossed the northern ice edge made a left turn loop with 150 km diameter over the sea ice and returned to the northern ice edge the ecmwf analysis places the cyclone track 100 km too far west over the sea ice a deviation which is too large for representative sea ice simulations on the east side of the northward moving cyclone the ice edge was pushed northward by 55 km because of strong winds on the rear side the ice edge advanced toward the open water but by a smaller distance because of weaker winds there the ice drift pattern as calculated from the ice buoys and the two radarsat images is cyclonically curved around the center of the cyclone loop ice drift divergence shows a spatial pattern with divergence in the loop center and a zone of convergence around ice concentration changes as retrieved from ssm i data follow the divergence pattern such that sea ice concentration increased in areas of divergence and decreased in areas of convergence

ocean heat flux under antarctic sea ice in the bellingshausen and amundsen seas two case studies we examine the role of ocean heat flux ohf in antarctic sea ice growth and melt using data from autonomous ice mass balance buoys deployed on pack ice in the bellingshausen sea and on fast ice in the amundsen sea during the spring summer october december 2007 and summer autumn february march 2009 transitions respectively ohfs are derived using two methods that examine changes in 1 sub ice ocean water properties ohf1 and 2 ice thickness ohf2 the latter only applying to thick snow covered ice i e a near zero temperature gradient near the ice bottom good agreement is found between the time averaged estimates of ohf1 and ohf2 average ohf measured was 8 2wm 2 under the pack ice and 17 2wm 2 under the landfast ice some short term ohf values ohf1 in both seas exceeded 55wm 2 the spring ohf variations in the bellingshausen sea were periodic and controlled by semi diurnal ice velocity fluctuations larger temperature fluctuations in the summer amundsen sea originating from incursions of warm deep water masses contributed to the ohf being twice as high as in the bellingshausen sea and also accounted for the irregular ohf variability there

thin ice and storms sea ice deformation from buoy arrays deployed during n ice2015 arctic sea ice has displayed significant thinning as well as an increase in drift speed in recent years taken together this suggests an associated rise in sea ice deformation rate a winter and spring expedition to the sea ice covered region north of svalbard the norwegian young sea ice2015 expedition n ice2015 gave an opportunity to deploy extensive buoy arrays and to monitor the deformation of the first year and second year ice now common in the majority of the arctic basin during the 5 month long expedition the ice cover underwent several strong deformation events including a powerful storm in early february that damaged the ice cover irreversibly the values of total deformation measured during n ice2015 exceed previously measured values in the arctic basin at similar scales at 100 km scale n ice2015 values averaged above 0 1 d 1 compared to rates of 0 08 d 1 or less for previous buoy arrays the exponent of the power law between the deformation length scale and total deformation developed over the season from 0 37 to 0 54 with an abrupt increase immediately after the early february storm indicating a weakened ice cover with more free drift of the sea ice floes our results point to a general increase in deformation associated with the younger and thinner arctic sea ice and to a potentially destructive role of winter storms

weddell sea ice drift kinematics and wind forcing ice drift in the weddell sea was studied on the basis of positional and meteorological data from argos buoys drifting in 1990 1992 and surface pressure analyses from the european centre for medium range weather forecasts ecmwf the drift kinematics showed differences between the eastern and western parts of the weddell sea close to the antarctic peninsula the ice drifted as an almost nonrotating uniform field at a low speed having reduced small scale motions with little meandering compared to regions further to the east inertial motion was detected from the ice drift in areas east of 35 w and in the region of the antarctic circumpolar current on timescales of days wind was the primary forcing factor for the drift a linear model between the wind and ice drift explained 40 80 of the drift velocity variance the degree of explanation was higher in the central weddell sea around 40 w and lower closer to the antarctic peninsula the geostrophic wind was found to provide almost as good a basis for the general drift estimation as the surface wind observed by the buoys although strong cyclones were not well detected by the ecmwf analyses the data suggest a dependency upon atmospheric stability such that stable stratification reduces the wind forcing on the drift for 60 80 of the time the direction of the drift deviated less than 45 from the geostrophic wind and for 45 70 of the time less than 45 from the ocean current ice transport through a transect crossing the weddell sea from the antarctic peninsula tip to kapp norwegia was estimated on the basis of the geostrophic winds the drift s observed response to the wind and literature based information on ice concentration and thickness the estimated annual mean net export in 1992 1994 varied from 8000 to 22 000 m3 s most of the net export took place in winter and spring export prevailing west of 35 w and import east of it

chemical and boron isotope compositions of non marine brines from the qaidam basin qinghai china the general chemistry and boron isotope composition were investigated in fresh waters and hypersaline brines from the qaidam basin northern qinghai xizang tibet plateau china this basin is a large tectonically active system isolated from the ocean and composed of thick clastic and evaporite sediments the modern playas are subject to intense evaporation and are characterized by hypersaline brines as well as potash and borate evaporites the chemical composition of the dissolved solutes in the modern brines and waters reveals three main sources 1 inflow of hot springs enriched in sodium sulphate and boron evaporation of these waters leads to a high na cl ratio 1 a na cl so4 brine and an evaporite mineral assemblage of halite mirabilite borate lakes daqaidam and xiaoqaidam 2 inflow surface river waters which are modified by preferential dissolution of halite and potassium and magnesium salts characterized by a na mg cl solute type with low na cl 1 brcl licl and bcl ratios and 3 ca chloridic subsurface brines which are controlled by both salt dissolution and dolomitization processes evaporation and salt crystallization of mixtures of the latter two types leads to a marine like brine e g na mg cl type nacl ratio 1 and mineral assemblages similar to that predicted for progressive evaporation of seawater e g qarhan playa halite sylvite carnallite bischofite the 11 b values of the input waters to the qaidam basin range of 0 7 to 10 9 vs nbs 951 and brines from salt lakes 0 5 to 15 0 are similar to those of associated granitic rocks 11b 2 3 to 3 7 n 3 and hence indicate the non marine origin of these fluids the highest 11b values are associated with fluids with low bli ratios indicating selective removal of elemental boron and 10b by adsorption onto clay minerals the magnitude of 11b enrichment due to adsorption is 15 20 and thus non marine brines are well distinguished from marine derived brines 11b of 39 to 59 preserving the large isotopic difference 40 of their source waters it is proposed to use this distinctive isotopic signature for tracing the origin of ancient evaporite environments

serpentinization carbon and deep life the aqueous alteration of ultramafic rocks through serpentinization liberates mantle carbon and reducing power serpentinization occurs in numerous settings on present day earth including subduction zones mid ocean ridges and ophiolites and has extended far into earth s history potentially contributing to the origins and early evolution of life serpentinization can provide the energy and raw materials to support chemosynthetic microbial communities that may penetrate deep into earth s subsurface microorganisms may also influence the composition and quantity of carbon bearing compounds in the deep subsurface however conditions created by serpentinization challenge the known limits of microbial physiology in terms of extreme ph access to electron acceptors and availability of nutrients furthermore the downward transport of surface carbon and subsequent mixing with calcium rich fluids at high ph contributes to the precipitation and immobilization of carbonate minerals the following chapter will explore the physiological challenges presented by the serpentinite environment data from studies of serpentinite hosted microbial ecosystems and areas in need of further investigation physical and chemical consequences of serpentinization serpentinization is an alteration process of low silica ultramafic rocks characteristic of the lower oceanic crust and upper mantle these rocks are rich in the minerals olivine and pyroxene water rock reactions result in the oxidation of ferrous iron from olivine and pyroxene resulting in the precipitation of ferric iron in magnetite fe3o4 and other minerals and in the release of diatomic hydrogen h2 at low temperatures 150 c the reaction results in extremely high ph commonly above 10 the combination of h2 and co2 or co under highly reducing conditions leads to formation of methane and other hydrocarbons through fischer tropsch type ftt synthesis mccollom and seewald 2001 charlou et al 2002 proskurowski et al 2008 mccollom 2013 serpentinization also results in volume changes in the altered materials making serpentinites less dense than

response of the weddell sea pack ice to wind forcing sea ice drift in the weddell sea was studied on the basis of data from seven buoys deployed on ice floes in january february 1996 six of the buoys formed an array with initial mutual distances of 50 km which by october 1996 were stretched to 400 km in an east west direction the differential kinematical parameters i e divergence shearing rate and vorticity were estimated from the buoy array positions by applying a time dependent method the large scale drift of the array was divergent until august 1996 but after the array came under the influence of the antarctic circumpolar current the deformation was mainly shearing meteorological data from european centre for medium range weather forecasts analyses and special sensor microwave imager derived ice concentrations were interpolated at the buoy sites the drift velocity was highly wind dependent it was also wind dependent in winter when the momentum balance was mainly between the internal ice stress and the air drag the drift divergence and shearing rate were related to the wind forcing while the array vorticity correlated better with the air pressure itself we estimated the air ice drag coefficient to be 1 8 10 3 at a height of 10 m over the ice and the geostrophic drag coefficient to be 6 1 10 4 the stability effects on the coefficients were mostly felt in conditions of light winds the average ice water drag coefficient based on 5 day periods was 2 1 10 3 the ice transport through a transect crossing the weddell sea was computed on the basis of the geostrophic winds observed wind drift dependence ssm i derived ice concentrations and the literature on ice draft statistics the resulting annual mean net export in 1996 was 1600 km3 yr 1

climate ocean control on the depositional watermass conditions and organic matter enrichment in lower cambrian black shale in the upper yangtze platform abstract the lower cambrian sediments including the qiongzhusi and maidiping formations in the sichuan basin are generally considered as the main source rocks of precambrian cambrian petroleum system a comprehensive study integrated with multiple geochemical methods was conducted on 119 lower cambrian drillcore samples collected from the upper yangtze platform the results show that the fluctuation of sea level and climate during the deposition of the qiongzhusi and maidiping formations act as the critical factors controlling the watermass conditions and thus om accumulation during the deposition of upper maidiping formation 1m the paleoclimate was arid and sea level was relatively low in the study area the depositional environment indexes uef moef gammacerane index carotane and vef suggested that the upper 1m was deposited in a strong restricted marine setting with high water salinity and anoxic water conditions in ziyang weiyuan area however during the early qiongzhusi formation period the paleoclimate became humid and sea level rose in the study area high paleoproductiviy caused by high concentrations of nutrients brought by seawater and freshwater plays an important role in om accumulation in the basal part of the qiongzhusi formation 1q furthermore the model of paleoproductivity promotion caused by the coordinated control of climate and extensive transgression in the lower part of 1q may also be applicable to interpret the origin of high organic carbon abundance in the strata deposited in the same period with the 1q such as shiyantou shuijingtuo and niutitang formations in other parts of the upper yangtze platform

the role of moist intrusions in winter arctic warming and sea ice decline abstractthis paper examines the trajectories followed by intense intrusions of moist air into the arctic polar region during autumn and winter and their impact on local temperature and sea ice concentration it is found that the vertical structure of the warming associated with moist intrusions is bottom amplified corresponding to a transition of local conditions from a cold clear state with a strong inversion to a warm opaque state with a weaker inversion in the marginal sea ice zone of the barents sea the passage of an intrusion also causes a retreat of the ice margin which persists for many days after the intrusion has passed the authors find that there is a positive trend in the number of intrusion events crossing 70 n during december and january that can explain roughly 45 of the surface air temperature and 30 of the sea ice concentration trends observed in the barents sea during the past two decades

hydrothermal scavenging at the mid atlantic ridge modification of trace element dissolved fluxes abstract we have carried out an icp ms study of the distributions of trace elements fe ca mg al mn cu zn v as cr co pb y mo ag sn cd and be in particulate material collected from the tag hydrothermal plume 26 n mid atlantic ridge to examine the extent to which fluxes of dissolved trace elements emitted from hydrothermal vent fluids are balanced by the precipitation of associated particulate phases comparison of particulate trace element distributions with particulate fe concentrations within the neutrally buoyant plume reveals that the distribution of trace elements within the plume is controlled by the following processes i co precipitation from vent fluids ii scavenging from seawater and iii preferential settling from the plume and oxidative dissolution within the water column for y and be continuous scavenging from seawater appears to be important whereas for v as and cr it appears that conditions suitable for uptake into particles may be restricted to the buoyant portion of the hydrothermal plume from a comparison of trace element fe ratios in the particles and associated mid atlantic ridge vent fluids it appears that for many elements e g cu co ag pb al cd be and zn the flux of dissolved material from vent fluids is matched closely by the precipitation of hydrothermal particulate phases of the various elements studied here hydrothermal activity only appears to act as a significant source for dissolved ca and dissolved mn

influence of volcanic and hydrothermal activity on organic matter enrichment in the upper triassic yanchang formation southern ordos basin central china abstract based on the field investigation of oil shales in the southern ordos basin detailed observations and systematic sample analyses of core samples from a well that penetrated an oil shale the influence of volcanic and hydrothermal activity on the chang 8 chang 7 members of the yanchang formation on organic matter om enrichment was geochemically and petrologically analyzed according to maceral analyses and rock pyrolysis the kerogen types of the samples in the study area are widely distributed those of the oil shale with the highest om abundance are mostly type ii i and are immature or in a stage of low maturity six layers of tuff and tuffaceous mudstone were identified by core observation and element characteristics they are characterized by higher total rare earth element ree and ce values and th contents and lower la yb n and eu values mineral assemblages of anhydrite pyrite marcasite and relevant diagrams of the elemental geochemistry confirmed the existence of hydrothermal deposits the high yn hon and u th ratios and total sulfur ts contents indicate that the chang 7 member experienced four episodes of intense hydrothermal activity early in the chang 73 member volcanic ash and hydrothermal fluids brought in a large amount of nutrients which not only increased primary productivity but also increased the salinity of the water column enhanced anoxia in the sedimentary environment of the lake bottom promoted the preservation of om and finally formed the oil shale layer with the richest om however the strong volcanic eruption in the late chang 73 member led to changes in the regional climate causing it to dry and become colder and resulting in a decrease of primary productivity earthquakes triggered by volcanism resulted in turbidite deposits which destroyed the preservation and diluted the enrichment of om this study reveals in detail the influence of volcanic and hydrothermal activity on om enrichment during the evolution of the basin and thereby deepens our theoretical understanding of om enrichment

the ice thickness distribution across the atlantic sector of the antarctic ocean in midwinter during the first leg of the winter weddell sea project antarktis v 2 cruise of f s polarstern the entire width of the antarctic sea ice zone was traversed in the vicinity of 0 longitude in the period july 18 to september 10 1986 ice thicknesses were measured by direct drilling and by helicopter profiling using an exstar 100 mhz impulse radar system in addition aerial photography of the ice cover was done from 100 to 2000 m altitude using a 70 mm aerial camera mounted in the helicopter the results of the point measurements drilling are reported in this paper together with an indication of how the radar and photography data will be used to extend them so as to yield area averaged ice thickness distributions it was found that the main ice type across the entire width of the ice cover was consolidated pancake ice occurring in vast floes this formed out of a 250 km wide band at the advancing ice edge which comprised a concentrated field of individual pancakes in a matrix of frazil ice preferred thicknesses of undeformed floes were 40 60 cm of ice covered with 5 15 cm of snow the individual pancakes attained almost all of this thickness before consolidation subsequent congelation growth was slow estimated at 0 4 cm d 1 the floes contained much small scale roughness on the upper and lower surfaces due to rafting of pancakes at the time of consolidation but pressure ridging was modest except in the far south a few very thick 8 11 m multiyear floes were observed embedded in the pack at latitudes beyond 66 s

unprecedented springtime retreat of antarctic sea ice in 2016 during austral spring 2016 antarctic sea ice extent sie decreased at a record rate of 75 103 km2 day 1 which was 46 faster than the mean rate and 18 faster than in any previous spring season during the satellite era the decrease of sea ice area was also exceptional and 28 greater than the mean anomalous negative retreat occurred in all sectors of the antarctic but was greatest in the weddell and ross seas record negative sie anomalies for the day of year were recorded from 3 november 2016 until 9 april 2017 rapid ice retreat in the weddell sea took place in strong northerly flow after an early maximum ice extent in late august rapid ice retreat occurred in november in the ross sea when surface pressure was at a record high level with the southern annular mode at its most negative for that month since 1968

a devonian hydrothermal chert reservoir the 225 bcf parkland field british columbia canada the 225 bcf original gas in place ogip parkland a pool was discovered in 1956 with the drilling of imperial pacific 6 29 81 15w6 this well initially production tested at 19 mmcf gas day and has produced more than 95 bcf of sweet gas the parkland play type as defined by the geological survey of canada consists principally of fracture associated hydrothermally karsted and dolomitized reservoirs hosted in the upper devonian famennian wabamun group medial ramp carbonates resting on the axis of the peace river arch and includes major fields such as tangent teepee and gold creek ironically parkland itself owes little of its production to hydrothermally dolomitized carbonates instead most of the reservoir pore volume can be attributed to microintercrystalline porosity within a pervasive replacement microquartz chert that occurs at the dolomite limestone interface the thickness of this chert zone in the 6 29 well is 35 m and occurs near the top of the wabamun the origin of the chert is problematic it postdates matrix dolomitization and crosscuts the early tournaisian mississippian exshaw ash but is in turn truncated by later saddle dolomite and calcite veins the replacement chert is composed of a microporous up to 30 meshwork of microquartz crystals averaging 5 10 m in size and is texturally distinct from early diagenetic chert nodules also found in the wabamun the two cherts are also distinguishable isotopically with the replacement microquartz showing significantly more depleted oxygen values 22 vs 25 d18o standard mean ocean water smow consistent with precipitation from hot fluids having a temperature range from about 140 to 200 c silicification has had the greatest impact on slightly dolomitized limestone at the outer margin of the hydrothermal dolostone pod entrapped floating euhedral crystals of dolomite within the replacement chert show little evidence of microdissolution suggesting that the silicic begin page 52 acid charged fluid although undersaturated with respect to the microspar lime matrix was saturated with respect to dolomite we postulate that hydrothermal fluids of common parentage only marginally evolved in composition if at all were responsible for both dolomitization and silicification both replacement processes occurred in relatively rapid succession at shallow burial depths and were related to an early tournaisian period of hydrothermal activity associated with both wrench and minor extension structuring linked with the nascent development of the fort st john graben the source of the silica is thought to be the immediately subjacent granite wash or possibly the precambrian basement stratigraphic proximity to the granite wash is likely a prerequisite condition for chert reservoir development within the wabamun and serves to explain along with significantly different hydrothermal fluid temperatures much hotter to the west why parkland is such a distinct field compared to tangent and teepee hydrocarbon reservoirs that are dominantly chert hosted are relatively uncommon but where recognized e g monterey formation california they are related to the redistribution and transformation of biogenic opal a silica derived from diatoms spicules and or radiolarians in deeper water sediments to our knowledge parkland is the only hydrothermal chert reservoir that has been reported anywhere in the world

in situ measurements of an energetic wave event in the arctic marginal ice zone r v lance serendipitously encountered an energetic wave event around 77 n 26 e on 2 may 2010 onboard gps records interpreted as the surface wave signal show the largest waves recorded in the arctic region with ice cover comparing the measurements with a spectral wave model indicated three phases of interaction 1 wave blocking by ice 2 strong attenuation of wave energy and fracturing of ice by wave forcing and 3 uninhibited propagation of the peak waves and an extension of allowed waves to higher frequencies above the peak wave properties during fracturing of ice cover indicated increased groupiness wave ice interaction presented binary behavior there was zero transmission in unbroken ice and total transmission in fractured ice the fractured ice front traveled at some fraction of the wave group speed findings do not motivate new dissipation schemes for wave models though they do indicate the need for two way wave ice coupling

pancake ice formation in the weddell sea 1 the ice formation resulting from two low temperature events at the weddell sea ice edge during april 2000 is presented pancake and frazil ice were sampled at seven stations at varying distances from the ice edge the ice cover was further characterized from above using helicopter aerial photography and from below using a remotely operated vehicle previously undescribed two layer pancake types were observed and classified a novel pancake growth mechanism is introduced to account for these involving the washing of frazil ice over the pancake top surface and its subsequent freezing the process was directly observed in ice tank experiments layer thicknesses seen in the field were compared to the ice growth that would occur both under calm conditions and from free surface frazil ice growth classical bottom accretion pancake growth was found to proceed at a rate similar to that of thin congelation ice top layer growth was more rapid at approximately double the congelation rate overall ice volume production was similar to congelation ice for the thin pancakes considered 20 cm though subsequent thickening was expected to be faster as the rapid top layer process continued and the equivalent congelation growth slowed it is suggested that parameterization of this new process is important for models that aim to simulate the rapid advance and thickening of wave influenced ice covers

geochemistry of trace elements in chinese coals a review of abundances genetic types impacts on human health and industrial utilization abstract china will continue to be one of the largest coal producers and users in the world the high volume of coal use in china has focused attention on the amounts of toxic trace elements released from coal combustions and also the valuable trace elements extracted or potentially utilized from coal ash compared to world coals chinese coals have normal background values for most trace elements with the exception of higher li 31 8 g g zr 89 5 g g nb 9 44 g g ta 0 62 g g hf 3 71 g g th 5 84 g g and rare earth elements la lu y 136 g g this is not only due to the higher ash yields of chinese coals but also to alkali volcanic ashes found in some southwestern coals the background values of toxic elements of hg 0 163 g g as 3 79 g g and f 130 g g in chinese coals are comparable to coals from most other countries the genetic types for trace element enrichment of chinese coals include source rock controlled marine environment controlled hydrothermal fluid controlled including magmatic low temperature hydrothermal fluid and submarine exhalation controlled subtypes groundwater controlled and volcanic ash controlled the background values of trace elements were dominated by sediment source regions low temperature hydrothermal fluid was one of the major factors for the local enrichment of trace elements in southwestern china serious human health problems caused by indoor combustion of coal in china include endemic fluorosis arsenosis selenosis and lung cancer endemic fluorosis mainly occurring in western guizhou was mostly attributed to the high fluorine in clay that was used as a briquette binder for fine coals in addition to a small quantity of fluorine from coal fluorine in the coal from endemic fluorosis areas of western guizhou is within the usual range found in china and the world endemic arsenosis in southwestern guizhou is attributed to indoor combustion of high as coal endemic selenosis in enshi of hubei was due to high se in carbonaceous siliceous rocks and carbonaceous shales fine particles of quartz released into air during coal combustion are hypothesized as a possible cause for the lung cancer epidemic in xuanwei yunnan china valuable elements including ge ga u ree rare earth element nb zr and re are concentrated to levels comparable to conventional economic deposits in several coals or coal bearing strata in china the ge deposits at lincang yunnan province and wulantuga inner mongolia have been exploited and industrially utilized the enrichment of ge in the two deposits was caused by hydrothermal fluids associated with adjacent granitoids the ga al ore deposit in the jungar coalfield inner mongolia was derived from the neighboring weathered and oxidized bauxite of the benxi formation pennsylvanian the nb ta zr hf ree ga deposits in the late permian coal bearing strata of eastern yunnan and chongqing of southwestern china were attributed to ashes of the alkali volcanic eruptions

arctic marginal ice zone trending wider in summer and narrower in winter 1 declines in arctic sea ice extent and thickness suggest scientifically important changes in the spatial pattern of the marginal ice zone miz a dynamic and biologically active band of sea ice cover close to open ocean arctic miz widths were measured in satellite era sea ice concentrations over the years 1979 2011 using a recently published miz width analysis method over the record the warm season july september miz width increased by 13 km decade 1 amounting to a 39 widening this widening trend resulted from a marked poleward advancement of the miz poleward edge into regions where sea ice was increasingly younger and thinner at the beginning of annual melt while the miz s equatorward edge moved comparatively little the warm season miz widening contrasted in sign and strength with a cold season february april miz narrowing trend 4 km decade 1 amounting to a 15 narrowing

the palaeobiology and geochemistry of precambrian hydrocarbon source rocks abstract organic carbon productivity and formation of hydrocarbon source rocks during the early precambrian was almost exclusively the product of the growth of microbial mats indirect evidence of microbial mats can be traced back to at least 2 6 2 7 ga neoarchaean with the earliest evidence of mat development in siliciclastic sediments coming from the 2 9 ga mesoarchaean predominantly marine sedimentary rocks of the mozaan group in south africa the earliest direct evidence for terrestrial microbial mats in siliciclastic sediments comes from the 2 75 ga palaeoproterozoic fluviolacustrine sediments of the hardey formation of the pilbara craton in western australia well preserved proterozoic hydrocarbons provide valuable information about the early evolution of the biosphere eukaryotic steranes biomarker for eukaryotic cells and therefore evolved forms of life are present in the geological record from about 2 7 ga but they are not abundant or diverse within archaean communities which tend to be dominated by archaea isoprenoids some hydrocarbons have been generated and migrated from archaean organic rich shales but they were probably not of sufficient volume to be of commercial interest the world s oldest significant hydrocarbon source rocks are palaeoproterozoic in age and include the shungite deposits 2 0 ga in the lake onega region of arctic russia there is strong evidence of a global biospheric oxygenation event at c 1300 1250 ma mesoproterozoic in conjunction with a first order positive shift in the marine carbon isotope record this is supported by the appearance of the oldest bedded marine gypsum deposits and of the earliest unambiguously multicellular eukaryotes at this time this oxygenation event probably played a significant role in supporting the more diverse eukaryotic communities preserved in the neoproterozoic molecular record and provided the volume of organic material required to generate commercial volumes of hydrocarbons hydrocarbon source rocks of late mesoproterozoic and early neoproterozoic age are widespread and include highly organic rich shales deposited in restricted basinal settings adjacent to stromatolitic carbonate banks by c 850 ma the neoproterozoic molecular record is dominated by hopanes from cyanobacteria with a significant abundance and diversity of eukaryotic steranes including those of multicellular eukaryotes red and green algae as well as molecular evidence for heterotrophic protists the most widespread hydrocarbon source rocks of mid to late neoproterozoic age are commonly transgressive organic rich black shales associated with inter glacial and post glacial phases of the neoproterozoic global scale glaciations the relative dominance of microbial mats in the contribution of organic matter as a source for hydrocarbon generation probably decreased significantly during the late neoproterozoic and earliest cambrian perhaps as a result of the rapid growth of grazing metazoan communities or possibly as a result of changes in seawater chemistry and or nutrient supply precambrian and infracambrian petroleum systems are relatively abundant and widespread the oldest live oil recovered to date is sourced from mesoproterozoic rocks within the velkerri formation roper group of the mcarthur basin of northern australia dated at 1361 21 ma and 1417 29 ma re os dates with at least the initial phase of oil generation and migration having taken place before 1280 ma however the geologically oldest commercial production is currently from the somewhat younger mid to late neoproterozoic cryogenian ediacaran petroleum systems of the lena tunguska province in east siberia and in southern china from the latest neoproterozoic to early cambrian huqf supergroup in oman and potentially in the near future from the age equivalent mawar supergroup in western india

conditions leading to the unprecedented low antarctic sea ice extent during the 2016 austral spring season the 2016 austral spring was characterized by the lowest anomalous southern hemisphere sh sea ice extent seen in the observational record 1979 present and coincided with anomalously warm surface waters surrounding most of antarctica two distinct processes contributed to this event firstly the extreme el nino event peaking in december february djf 2015 16 contributed to pronounced extra tropical sh sea surface temperature and sea ice extent anomalies in the eastern ross amundsen and bellingshausen seas that persisted in part until the following 2016 austral spring secondly internal unforced atmospheric variability of the southern annular mode promoted the exceptional low sea ice extent in november december 2016 these results suggest that a combination of tropically forced and internal sh atmospheric variability contributed to the unprecedented sea ice decline during the 2016 austral spring on top of the slow background changes expected from greenhouse gas and ozone forcing

effects of an explosive polar cyclone crossing the antarctic marginal ice zone antarctic sea ice shows a large degree of regional variability which is partly driven by severe weather events here we bring a new perspective on synoptic sea ice changes by presenting the first

late archean euxinic conditions before the rise of atmospheric oxygen life on earth is thought to have coevolved with the chemistry of the oceans and atmosphere and the shift from an anoxic to an oxic world across the archean proterozoic boundary represents a fundamental step in this process in order to understand the relative influence of biological and geological factors on this transition we must constrain key variables in seawater chemistry before the great oxidation event ca 2500 ma we present a multielement c s fe mo biogeochemical study of ca 2662 ma shales from the hamersley province in western australia our data reveal a sustained episode of fe limited pyrite formation under an anoxic and sulfidic euxinic water column this is the oldest known occurrence of euxinia in earth9s history and challenges the paradigm of persistently fe rich archean oceans bulk trace metal chemistry and preservation of strong mass independent s isotope fractionations in sedimentary pyrites indicate that ocean euxinia was possible prior to oxidative weathering suggesting that sulfidic waters may have been common throughout the archean eon c s fe systematics suggest that oxygenic photosynthesis was the primary source of organic carbon in the basin and the absence of mo enrichments highlights a potential link between inefficient nitrogen fixation and the delayed arrival of the great oxidation event

sedimentary characteristics and origin of dolomitic ooids of the terminal ediacaran dengying formation at yulin chongqing south china abstract the ediacaran was a crucial transition period in the evolutionary history of the earth ediacaran ooids in the dengying formation from the yulin section in southwestern china are important archives of paleoenvironmental information although these ooids have been totally dolomitized the cortical fabric characteristics are locally preserved well indicating that these ooids were mimetically replaced the common occurrence of concentric radial fabrics and low level of sr concentrations 60 3 8 8 ppm in the studied ooid cortex is more likely suggestive of a primary low mg calcite mineralogy and that a calcite sea might exist during deposition of the second member of the dengying formation in situ geochemical data for the ooid cortices obtained by laser ablation inductively coupled plasma mass spectrometry show that these ooids have middle rare earth element enrichment prn smn 0 7 0 1 and smn ybn 1 5 0 4 and high fe contents 8200 1800 ppm this suggests ferruginous pore waters which were related to the selective or preferential absorption and release of rees by fe mn oxyhydroxides

ocean heat flux in the central weddell sea during winter abstract seasonal sea ice which plays a pivotal role in air sea interaction in the weddell sea a region of large deep water formation with potential impact on climate depends critically on heat flux from the deep ocean during the austral winter of 1994 an intensive process oriented field program named the antarctic zone flux experiment measured upper ocean turbulent fluxes during two short manned ice drift station experiments near the maud rise seamount region of the weddell sea unmanned data buoys left at the site of the first manned drift provided a season long time series of ice motion mixed layer temperature and salinity plus a truncated high resolution record of temperature within the ice column direct turbulence flux measurements made in the ocean boundary layer during the manned drift stations were extended to the ice ocean interface with a mixing length model and were used to evaluate parameters in bulk expressions for interfacial stress a rossby similarity drag law and ocean to

lithium and boron bearing brines in the central andes exploring hydrofacies on the eastern puna plateau between 23 and 23 30 s internally drained basins of the andean plateau are lithium and boron bearing systems the exploration of ionic facies and parental links in a playa lake located in the eastern puna 23 23 30 s was assessed by hydrochemical determinations of residual brines feed waters and solutions from weathered rocks residual brines have been characterized by the cl so4 na k ratio residual brines from the playa lake contain up to 450 mg l of boron and up to 125 mg l of lithium and the las burras river supplies the most concentrated boron 20 mg l and lithium 3 75 mg l inflows of the basin the hydro geochemical assessment allowed for the identification of three simultaneous sources of boron 1 inflow originating from granitic areas of the aguilar and tusaquillas ranges 2 weathering of the ordovician basement and 3 boron rich water from the las burras river most of the lithium input of the basin is likely generated by present geothermal sources rather than by weathering and leaching of ignimbrites and plutonic rocks however xrd analyses of playa lake sediments revealed the presence of lithian micas of clastic origin including taeniolite and eucriptite this study is the first to document these rare li micas from the puna basin thus both residual brines and lithian micas contribute to the total li content in the studied hydrologic system

petrology and geochemistry of chert on the marginal zone of yangtze platform western hunan south china during the ediacaran cambrian transition the ediacaran cambrian transition was one of the most critical intervals in earth history during this interval widespread chert was precipitated commonly as a stratal wedge in carbonates along the southern margin of the yangtze platform south china the chert wedge passes into a full chert succession further basinward to the south east four lithotypes of chert are identified across the marginal zone in western hunan mounded vein brecciated and bedded chert the mounded chert is characterized by irregular to digitiform internal fabrics generally with abundant original vesicles and or channels that mostly are lined by botryoidal chalcedony cements with minor quartz and barite crystals the host chert or matrix of these mounds is dominated by amorphous cryptocrystalline silica commonly disseminated with pyrite the vein chert with minor quartz locally generally cross cuts the overlying dolostone and chert horizons and terminates under the mounded and or bedded chert bodies the brecciated chert commonly occurs as splayed intrusions or funnel shaped wedges and cross cuts the topmost dolostones the bedded chert the most common type generally is thin to medium bedded and laminated locally it is composed of amorphous silica with minor amounts of black lumps microthermometry of fluid inclusions from vein and void lining minerals mainly quartz and barite revealed homogenization temperatures from 120 to 180 c for the trapped primary fluids compositionally these chert deposits generally are pure with sio2 92 wt and only minor fe2o3 and al2o3 contents most of which show positive europium anomalies in rare earth element patterns especially for the mounded chert all these data suggest that the marginal zone chert deposits resulted from a low temperature silica rich hydrothermal system in which the mounded chert was precipitated around the releasing vents i e as silica chimneys the vein and splayed brecciated chert however was formed along the syndepositional fault fracture conduits that linked downward while the bedded chert was precipitated in the quieter water column from the fallout of hydrothermal plumes onto the sea floor these petrological and geochemical data provide compelling evidence and a new clue to the understanding of the extensive silica precipitation rapid tectonodepositional and oceanic changes during the ediacaran cambrian transition in south china

dynamical contrasts between pancake and pack ice investigated with a drifting buoy array 1 the motion of pancake ice was investigated using an array of specialised drifting buoys deployed into the advancing ice edge of the weddell sea in april 2000 the buoys remained in the ice as the pancakes consolidated into a coherent ice sheet and the study examined the contrasts in dynamics for equivalent periods before and after consolidation drift velocities were largely determined by the meridional component perpendicular to the ice edge prior to consolidation these showed significantly elevated magnitudes at high frequencies periods shorter than six hours scalar velocities were higher than previously reported values reducing with time and distance from the ice edge the same trends were not evident from in situ wind data derivation of momentum transfer parameters wind factor turning angle was hampered by a lack of reliable wind directions from the outermost buoys however relative motions between buoys were investigated using differential kinematic parameters these displayed high amplitude high frequency oscillations in unconsolidated ice with rms invariant values up to two orders of magnitude higher than normally reported for weddell sea pack ice the values were found to be strongly dependent on sampling interval increasing further at intervals less than one hour in situ winds did not display an equivalent variation suggesting that wind forcing was not responsible and translation under wave action either internal or surface gravity was postulated as the forcing

quantitative evaluation of the biostratigraphic distribution of acanthomorphic acritarchs in the ediacaran doushantuo formation in the yangtze gorges area south china abstract doushantuo acanthomorphic acritarchs are large morphologically complex organic walled microfossils broadly constrained between the 635 ma nantuo glaciation and the 551 ma miaohe biota they are potential biostratigraphic tools for subdivision and correlation of the ediacaran system in south china however major variations in sedimentary facies and stratigraphic thickness present challenges in understanding the spatial and temporal distribution of these acritarchs further the distribution of acritarchs in the doushantuo formation is associated with the presence of early diagenetic chert and phosphate implying a certain degree of preservational bias and or environmental control the purpose of this paper is to document the stratigraphic distribution of doushantuo acritarchs and to quantitatively evaluate their biostratigraphic significance and possible taphonomic environmental biases based on high resolution paleontological data from six sections over 100 km in the yangtze gorges area south china a total of 1082 acritarch fossils were recorded from 84 chert horizons in the six sections of the study area these chert horizons are not uniformly distributed throughout the doushantuo formation thus the presence absence of early diagenetic chert does play a role in controlling the distribution of acritarchs the sampled chert horizons can be grouped into two stratigraphic intervals in the lower and upper doushantuo formation respectively based on regional stratigraphic correlation quantitative analysis shows that the two intervals are distinct taxonomically and largely independent of taphonomic or facies controls thus the two intervals can be regarded as assemblage biozones the lower biozone biozone 1 is numerically dominated by tianzhushania spinosa n 587 68 3 and meghystrichosphaeridium magnificum n 74 8 6 whereas the upper biozone biozone 2 is dominated by ericiasphaera rigida n 104 47 1 and tianzhushania spinosa n 34 14 1 the three most common genera meghystrichosphaeridium tianzhushania and ericiasphaera have been identified in all sections correspondence analysis ca detrended correspondence analysis dca discriminant analysis da and pairwise comparisons of samples spearman rank coefficient and jaccard chao index all consistently support biostratigraphic zonations thus the distribution of the doushantuo acanthomorphs is primarily controlled by biostratigraphic position of samples with facies and taphonomic differences playing a secondary role our case study suggests that acanthomorphic acritarchs can offer a viable tool for regional correlation of the ediacaran system

ediacaran cambrian ordovician silurian and permian shales of the upper yangtze platform south china deposition thermal maturity and shale gas potential abstract for many years the yangtze platform has been successfully explored and exploited for petroleum the lower silurian longmaxi shale proved to contain commercial quantities of gas but several other formations might also have a high potential for shale hosted gas exploration this paper comprises of geochemical petrographical petrophysical and mineralogical information on the major proterozoic and paleozoic gas shales in the upper yangtze area which provides insights on the depositional environment the thermal maturity of organic matter shale gas storage capacity and the fracability of these rocks the total organic carbon toc content varies from 0 1 to 22 5 with an average value of 2 7 and most of these shales were deposited in an oxygen depleted marine environment equivalent vitrinite reflectance vrr values range from 2 20 to 4 25 indicating that all samples are in the gas generation window and lost a large amount of primary organic carbon porosity varies between 1 5 and 13 6 with an average value of 5 8 while the excess sorption capacity ranges from 0 10 to 0 22 mmol g rock minerology data show that quartz is the predominant mineral except for the upper permian longtan formation in which clay minerals account for 29 to 84 new data were combined with those from other publications and compared to information on other well studied shale hosted gas systems

the rainbow vent fluids 36 14 n mar the influence of ultramafic rocks and phase separation on trace metal content in mid atlantic ridge hydrothermal fluids fluids were collected from the rainbow vent field 36 14 n on the mid atlantic ridge mar during the 1997 diving flores cruise this vent field in ultramafic rocks at a depth of 2300 m is composed of 10 black smokers emitting acidic ph 2 8 fluids at 365 c the low ph of the hot temperature rainbow fluids likely results from seawater ultramafic rock interaction that releases h ions into reducing hydrothermal fluids fluid chemistry is strongly influenced by phase separation generating cl rich brines clem 750 mm strongly enriched with mn fe co ni cu zn ag cd cs pb y and rare earth elements ree ree and transition metal abundance particularly fe and mn in the rainbow fluids is dramatically higher than in other mar fluids the abundance of trace element and ree enrichment is due to the greater solubility of these elements that is strongly favored by cl complexation at low ph and high temperature conditions chondrite normalized ree patterns show strong lree enrichment with evidence of the typical eu anomaly this ree partitioning suggests that either 1 ultramafic rocks represent only a part of rocks leached during hydrothermal alteration and or 2 that the unique rainbow fluid temperature ph and redox state issued from the ultramafic character of leached substratum can produce unique ree partitioning

sar imaging of wave dispersion in antarctic pancake ice and its use in measuring ice thickness 1 a synthetic aperture radar sar image of the advancing winter marginal ice zone miz in the antarctic composed of frazil pancake ice has been analysed in a new way in order to test the predictions of a recently developed theory of wave dispersion in pancake ice which treats the ice as a viscous layer in the image obtained in april 2000 the structure of the wave spectrum in the miz and its change from the open water spectrum are consistent with a pancake layer 24 cm thick intensive in situ measurements of the pancake ice in the miz 280 km w of the image location were made from fs polarstern during a period covering the satellite imaging and also yielded a mean ice thickness of 24 cm we conclude that this technique gives realistic results for ice thickness whereas earlier work based on a different dispersion theory mass loading tended to over estimate thickness after further validation it is therefore possible that the sar wave technique can become an accepted method for monitoring ice thickness in pancake icefields

strong responses of southern ocean phytoplankton communities to volcanic ash volcanic eruptions have been hypothesized as an iron supply mechanism for phytoplankton blooms however little direct evidence of stimulatory responses has been obtained in the field here we present the results of twenty one 1 2 day bottle enrichment experiments from cruises in the south atlantic and southern ocean which conclusively demonstrated a photophysiological and biomass stimulation of phytoplankton communities following supply of basaltic or rhyolitic volcanic ash furthermore experiments in the southern ocean demonstrated significant phytoplankton community responses to volcanic ash supply in the absence of responses to addition of dissolved iron alone at these sites dissolved manganese concentrations were among the lowest ever measured in seawater and we therefore suggest that the enhanced response to ash may have been a result of the relief of manganese co limitation our results imply that volcanic ash deposition events could trigger extensive phytoplankton blooms potentially capable of significant impacts on regional carbon cycling

influence of volcanic activities on redox chemistry changes linked to the enhancement of the ancient sinian source rocks in the yangtze craton abstract volcanic eruptions and related submarine hydrothermal activities were very extensive during the precambrian periods in the yangtze craton in southern china how these geological events affected redox chemistry changes linked to the enhancement of mudstone shale hydrocarbon source rocks in ancient strata is an important concern for oil and gas exploration in the precambrian strata samples were collected from two sinian ediacaran outcrops in the northern sichuan basin the zhaiziyan and yanhe outcrops which revealed doushantuo formation z1ds shales approximately 30 5 m in thickness and shales in the third member of the deying formation z2dn3 approximately 30 0 m in thickness toc contents of the black carbonaceous shales in the doushantuo formation of the zhaiziyan outcrop are mostly greater than 5 0 up to 12 9 positive correlations were observed between toc contents and trace and rare earth element concentrations in the shales samples with high concentrations of trace elements such as v ni cu zr rb and pb and total rare earth element ree concentrations had relatively high toc contents the shales are rich in volcanic ash interlayers and thin siliceous layers and have positive eu anomalies indicating that volcanic activities and related hydrothermal activities significantly impacted the development of black shale source rocks in the rifting background of the sinian cratonal marginal extensive volcanic activities brought rich nutrients to the seawater which may have promoted the breeding of cyanobacteria and multicellular algae at the same time the volcanic activities released large amounts of h2s and so2 which could cause the seawater to become a euxinic environment in which the bottom seawater was sulfurized and anoxic massive amounts of organic matters formed in the surface seawater entered the anoxic bottom seawater and were well preserved in the shale sediments therefore under the influence of volcanic activities ancient sinian organic rich high quality source rocks were widely developed and had a large hydrocarbon supply potential for the sinian dolomite reservoirs

lagrangian modelling of frazil ice in the ocean a new modelling framework using lagrangian particle tracking has been developed to assess dynamic and thermodynamic effects of underwater frazil ice this frazil ice model treats a lagrangian particle as a bulk cluster of many frazil crystals and calculates the thermodynamic growth of each particle and the corresponding budget of latent heat and fresh water the effective density and viscosity of sea water depend on the mass fraction of underwater frazil ice and hence affect ocean convection an idealized experiment using our model successfully reproduces the formation of underwater frazil ice and its transition to grease ice at the surface because underwater frazil ice does not reduce the atmosphere ocean heat exchange surface heat flux and net sea ice production in the experiment with frazil ice are relatively high compared with the experiment where surface cooling directly leads to columnar growth of a solid ice cover which effectively insulates the heat flux these results suggest that large scale sea ice models which do not take account of the effects of frazil ice might underestimate atmosphere ocean heat exchange particularly at times of active new ice formation

explosive cyclone development in the southern hemisphere and a comparison with northern hemisphere events abstract a compilation of southern hemisphere sh explosively developing cyclones or bombs has been assembled based on the national centers for environmental prediction department of energy reanalysis 2 data over the 21 yr period from 1979 to 1999 the identification of these features was undertaken with an objective automated cyclone finding and tracking scheme the procedure allows for the confounding influence of spatial variations of climatological mean pressure on the pressure deepening of explosive cyclones a perspective of particular importance in the sh on average 26 explosive cyclones occur per year in the sh they are more prevalent in winter although their seasonality is more modest than that seen in the northern hemisphere nh the distribution of sh explosive cyclones has a close association with that of strong baroclinicity although the relationship is not one to one it is found that many of these cyclones occurring south of 50 s show equatorward movement in contrast with the pol