organic matter in oligocene menilite formation rocks of the ukrainian carpathians palaeoenvironment and geochemical evolution abstract the ukrainian carpathians form the middle sector of the carpathian arc the menilite black shale formation oligocene early miocene is the youngest part of the flysch sequence and occurs in a wide depth range the anaerobic bacterial processes during early diagenesis led to formation of 13 c rich carbonate concretions and 13 c depleted organic matter black shales contain type ii kerogen with high source rock potential in the upper 4 km of the sequence the rocks preserved their pre overthrusting level of maturity close to the beginning of the oil window while at greater depths the maturity increases under the influence of present day heat flow

migration induced compositional changes in oils and condensates of a single field thirty one oils and condensates from the vermilion 39 field offshore louisiana u s gulf coast are examined using techniques of elemental isotopic and molecular geochemistry in an effort to determine the causes of compositional differences among them compositional variability in elemental concentration carbon isotope ratios and molecular distributions suggests that at least two sub groups occur in the sample set the sub groups are characterized by differences in n c 15 content relative to n c 15 pristane phytane ratio 13 c sulfur and nitrogen concentration and s n ratio although the separation into these two sub groups is superficially indicative of distinct sources and or variable levels of thermal maturity interpretation of the data set as a whole indicates that source influences maturity differences and biodegradation do not control observed variations in composition reliable source e g r c 27 29 sterane distribution and maturity e g 20s 20s 20r parameters provide clear evidence of a common source and constant maturity level for all 31 oils condensates the remaining geochemical differences including various molecular pristane phytane isotopic 13 c oil and elemental s n parameters correlate with the extent of migration fractionation that each sample has undergone as measured by the relative amount of n c 15 in each sample the migration fractionation process in the vermilion 39 field is facilitated by fault initiated pressure releases within reservoirs that originally contained full range crudes vertical migration of the released saturated hydrocarbon gases has led to a concentration of lighter components in the most fractionated samples this geochemical interpretation is supported by geologic data inasmuch as the extent of fractionation is least in the deepest samples and greatest in the shallowest samples the results presented here indicate the potential for misinterpretation of geochemical parameters previously considered to be influenced solely by source influence or thermal maturity

ch 4 consuming microorganisms and the formation of carbonate crusts at cold seeps to understand the role played by microorganisms in the formation of cold seep carbonates we conducted an integrated microbial mineralogical and organic geochemical study of methane related authigenic carbonate crusts formed on eastern mediterranean mud volcanoes we show that supersaturation with respect to carbonate minerals is induced by microbial anaerobic oxidation of methane combined lipid biomarker analysis and 16s rrna gene surveys identified a highly diversified methane consuming archaeal community possibly comprising novel species implying that the anaerobic oxidation of methane is phylogenetically widespread and directly implicating these organisms in the process of crust precipitation moreover pore water sulphate gradients produced by co occurring methane based sulphate reduction exert the main control on aragonite versus magnesian calcite precipitation we propose that this may be the dominant mode of carbonate crust formation at cold seeps world wide in agreement with aquatic chemistry predictions and explaining carbonate mineralogy

oil oil and oil source rock correlations in the carpathian foredeep and overthrust south east poland abstract the chemical composition of 35 crude oils and the extracts of potential source rock samples from south east poland were studied in detail by geochemical methods in order to understand their genetic relationships twenty six oils including three seep samples were collected from cretaceous to oligocene reservoirs within the carpathian overthrust nine oils originated from carboniferous to miocene reservoirs within the carpathian foredeep the rock samples studied were selected after rock eval pyrolysis screening of a large suite of samples and consist of one lower cretaceous sample and five oligocene menilite shale samples from three different outcrop locations all within the carpathian overthrust geochemical fingerprinting indicates at least two families of crude oils the first represented only by one oil has no specific characteristics except for a light carbon isotope composition the second family is characterized by the presence of 28 30 dinor hopane oleanane and a highly branched isoprenoid c25 alkane within this latter family four subfamilies were recognized a 19 oils having the aforementioned characteristics b seven oils similar to subfamily a but with a relatively high sulphur content c one oil with high abundance of higher plant derived triterpanes and d seven oils with abundant 28 30 dinor hopane although maturity influences the relative abundance of 28 30 dinor hopane it suggested that subfamilies a b and c had an initial low 28 30 dinor hopane content whereas subfamily d an initial high 28 30 dinor hopane content only one oil of subfamily a could potentially be a high maturity counterpart of subfamily d a palaeozoic source rock is suggested for the first family and the second family including the majority of the pils from the carpathian foredeep is most likely derived from the oligocene menilite shales an oil source rock relationship with the menilite shale is supported by the presence although not in all samples studied of 28 30 dinor hopane oleanane or its precursors and the highly branched isoprenoid alkane the strong facies variations observed within this shale gave rise to the different types of crude oils in the second family

diagenetic and catagenetic products of isorenieratene molecular indicators for photic zone anoxia a wide range of novel diagenetic and catagenetic products of the diaromatic carotenoid isorenieratene a pigment of the photosynthetic green sulphur bacteria chlorobiaceae has been identified in a number of sedimentary rocks ranging from ordovician to miocene compound identification is based on nmr mass spectrometry the presence of atropisomers and stable carbon isotopes atropisomers contain an axially chiral centre which in combination with other chiral centres results in two or more diastereomers that can be separated on a normal gc column chlorobiaceae use the reverse tca cycle to fix carbon so that their biomass is enriched in 13c high 13c contents of isorenieratene derivatives therefore support their inferred origins isorenieratene derivatives include c 40 c 33 and c 32 diaryl isoprenoids and short chain aryl isoprenoids with additional aromatic and or s containing rings c 33 and c 32 compounds are diagenetic products of c 33 and c 32 carotenoids formed from isorenieratene during early diagenesis through expulsion of toluene and m xylene respectively cyclisation of the polyene acyclic isoprenoid chain can proceed via an intramolecular diels alder reaction followed by aromatisation of the newly formed ring sulphurisation is also an important process during early diagenesis competing with expulsion and cyclisation sulphur bound isorenieratane is released during progressive diagenesis due to cleavage of relatively weak ss and cs bonds cleavage of c c bonds during aromatisation of newly formed rings and during catagenesis yields short chain compounds the inherent presence of a conjugated double bond system in carotenoids implies that similar diagenetic and catagenetic reactions can occur with all carotenoids chlorobiaceae live at or below the oxic anoxic boundary layer and require both light and h 2s the presence of isorenieratene or its diagenetic and catagenetic products in ancient sedimentary rocks and crude oils is therefore an excellent indication for photic zone anoxia in the depositional environment diagenetic and catagenetic products of isorenieratene are expected to find applications in reconstruction of palaeoenvironments and in oil oil and oil source rock correlation studies their presence in several petroleum source rocks suggests that anoxia is an important environmental parameter for the preservation of organic matter

raman spectroscopy for mineral identification and quantification for in situ planetary surface analysis a point count method quantification of mineral proportions in rocks and soils by raman spectroscopy on a planetary surface is best done by taking many narrow beam spectra from different locations on the rock or soil with each spectrum yielding peaks from only one or two minerals the proportion of each mineral in the rock or soil can then be determined from the fraction of the spectra that contain its peaks in analogy with the standard petrographic technique of point counting the method can also be used for nondestructive laboratory characterization of rock samples although raman peaks for different minerals seldom overlap each other it is impractical to obtain proportions of constituent minerals by raman spectroscopy through analysis of peak intensities in a spectrum obtained by broad beam sensing of a representative area of the target material that is because the raman signal strength produced by a mineral in a rock or soil is not related in a simple way through the raman scattering cross section of that mineral to its proportion in the rock and the signal to noise ratio of a raman spectrum is poor when a sample is stimulated by a low power laser beam of broad diameter results obtained by the raman point count method are demonstrated for a lunar thin section 14161 7062 and a rock fragment 15273 7039 major minerals plagioclase and pyroxene minor minerals cristobalite and k feldspar and accessory minerals whitlockite apatite and baddeleyite were easily identified identification of the rock types kreep basalt or melt rock from the 100 location spectra was straightforward

methane related carbonate cements in pockmarks of the north sea abstract some pockmarks on the norwegian continental shelf contain patches of cemented sediment that can provide hardgrounds attractive to a variety of benthonic organisms detailed examination of a sandstone sample from a pockmark in norwegian block 25 7 in the north sea has revealed the presence of mg calcite and aragonite cements some of the latter forming botryoids all cement types are characterized by extremely light carbon isotopic compositions with a mean 13c value of 56 1 pdb which shows that the cements contain carbonate produced by oxidation of biogenic methane oxidation occurred in both the oxic and anoxic diagenetic zones trace amounts of interstitial methane mean 13c 40 8 and higher hydrocarbon gases up to c5 with a c1 cn ratio of 0 855 0 874 in the pockmark sediments indicate that some thermogenic methane may be mixed with the biogenic gas

laser raman detection of authigenic carbonates from cold seeps at the formosa ridge and east of the pear river mouth basin in the south china sea abstract laser raman spectroscopy has been successfully applied for the in situ detection of gases and liquids but has not yet been extensively applied to rocks in the deep sea authigenic carbonate rocks are widely distributed at the formosa ridge site f and the eastern region of the pear river mouth basin site p in the south china sea scs considerable raman spectral information on authigenic carbonates was obtained from laboratory measurements of slices of authigenic carbonate direct measurements in a simulation environment and in situ measurements in the deep sea the dominant band of authigenic carbonate from site f ranges from 1084 to 1087 cm 1 while the dominant band from site p ranges from 1088 to 1091 cm 1 suggesting that compositional differences exist between the samples from the two cold seep areas the results of the point counting method indicates that the aragonite content in site f is higher than that at site p the wider peak width of the aragonites at site p shows the aragonites at site p have lower degree of crystallinity which suggests that aragonite is likely to be destroyed when the cold seep weakens or dies the above information obtained via the raman spectroscopy can guide sample collection in the deep sea and can be used in conjunction with other analysis methods to better understand environmental changes or the geological processes

fluid flow methane fluxes carbonate precipitation and biogeochemical turnover in gas hydrate bearing sediments at hydrate ridge cascadia margin numerical modeling and mass balances a numerical model was applied to investigate and to quantify biogeochemical processes and methane turnover in gas hydrate bearing surface sediments from a cold vent site situated at hydrate ridge an accretionary structure located in the cascadia margin subduction zone steady state simulations were carried out to obtain a comprehensive overview on the activity in these sediments which are covered with bacterial mats and are affected by strong fluid flow from below the model results underline the dominance of advective fluid flow that forces a large inflow of methane from below 869 mumol cm 2 a 1 inducing high oxidation rates in the surface layers anaerobic methane oxidation is the major process proceeding at a depth integrated rate of 870 mumol cm 2 a 1 a significant fraction 14 of bicarbonate produced by anaerobic methane oxidation is removed from the fluids by precipitation of authigenic aragonite and calcite the total rate of carbonate precipitation 120 mumol cm 2 a 1 allows for the build up of a massive carbonate layer with a thickness of i m over a period of 20 000 years aragonite is the major carbonate mineral formed by anaerobic methane oxidation if the flow velocity of methane charge fluids is high enough greater than or equal to10 cm a 1 to maintain super saturation with respect to this highly soluble carbonate phase it precipitates much faster within the studied surface sediments than previously observed in abiotic laboratory experiments suggesting microbial catalysis the investigated station is characterized by high carbon and oxygen turnover rates approximate to1000 mumol cm 2 a 1 that are well beyond the rates observed at other continental slope sites not affected by fluid venting this underlines the strong impact of fluid venting on the benthic system even though the flow velocity of 10 cm a 1 derived by the model is relative low compared to fluid flow rates found at other cold vent sites non steady state simulations using measured fluid flow velocities as forcing demonstrate a rapid respond of the sediments within a few days to changes in advective flow moreover they reveal that efficient methane oxidation in these sediments prevents methane outflow into the bottom water over a wide range of fluid flow velocities 80 cm a 1 only at flow rates exceeding approximately 100 cm a 1 does dissolved methane break through the sediment surface to induce large fluxes of up to 5000 mumol ch4 cm 2 a 1 into the overlying bottom water

no signature of abyssal carbon in intermediate waters off chile during deglaciation the rise in atmospheric carbon dioxide at the end of the last glacial maximum has been attributed to the release of carbon dioxide from the deep southern ocean however reconstructions of the radiocarbon signature of chilean margin intermediate waters during the glacial termination do not reflect the influence of such a release

geochemistry origin and deep water exploration potential of natural gases in the pearl river mouth and qiongdongnan basins south china sea more than 10 gas pools have been discovered since 1983 in the shallow water region of the pearl river mouth prm basin and the qiongdongnan qdn basin offshore south china sea gases produced from the qdn basin are characterized by high contents of benzene and toluene and relatively heavy 13c2 values 25 to 27 the associated condensates have a high abundance of bicadinanes and oleanane providing a good correlation with the coal bearing sequence of the oligocene yacheng formation in the basin in contrast the gases from the prm basin contain lower amounts of benzene and toluene and lighter 13c2 values 24 to 34 widely variable concentrations of bicadinane and oleanane were identifiied from the associated condensates which can be mostly correlated with the lower oligocene enping formation source rocks formed in a swamp to shallow lake environment oil cracked gases sourced from the eocene oil prone source rock may also provide some contribution to the prm basin gases the available geochemical data indicate that both the yacheng and enping formations contain mainly type iii and ii2 kerogens with dominant gas potential regional geological information indicates that the deep water regions of the two basins share the same hydrocarbon source sags with the shallow water areas and they developed massive sandstone reservoirs during the oligocene and miocene fluid flow modeling results show that the deep water regions were on the pathway of lateral migrating gases and the interpreted reservoirs in these zones have developed abundant seismic bright spots which may reflect the presence of gas the deep water regions of the offshore south china sea are believed to have great gas exploration potential

raman spectroscopy as a method for mineral identification on lunar robotic exploration missions fiber bundle that carried the laser beam and returned the scattered radiation could be placed against surfaces at any desired angle by a deployment mechanism otherwise the instrument would need no moving parts a modem micro raman spectrometer with its beam broadened to expand the spot to 50 gm diameter and set for low resolution 7 cm in the 100 1400 cm region relative to 514 5 nm excitation was used to simulate the spectra anticipated from a rover instrument we present spectra for lunar mineral grains 1 mm soil fines breccia fragments and glasses from frequencies of olivine peaks we derived sufficiently precise forsteritc contents to correlate the analyzed grains to known rock types and we obtained appropriate forsteritc contents from weak signals above background in soil fines and breccias peak positions of pyroxenes were sufficiently well determined to distinguish among orthorhombic monoclinic and triclinic pyroxenoid structures additional information can be obtained from pyroxene spectra but requires further laboratory calibration plagioclase provided sharp peaks in soil fines and most breccias even when the glass content was high

source rock habitat and hydrocarbon potential of oligocene menilite formation flysch carpathians southeast poland an organic geochemical and isotope approach geochemical and isotope methods have been used to analyse the hydrocarbon potential and petroleum generation characteristics of the oligocene menilite formation the most important petroleum source rock in the overthrust part of the carpathian foreland basin in se poland the data show a large variability in quantity up to 18 toc quality type ii and ii iii and carbon isotope composition of the organic matter in samples of different lithology and from different stratigraphic and tectonic settings these differences reflect distinct sedimentary and tectonic histories of individual sub basins the maturity in the outer tectonic units is very low tmax 420 c ro 0 35 but increases towards the inner nappes and also laterally to the se the variability of the kinetic parameters indicates the likely occurrence of multiphase hydrocarbon generation the menilite formation forms a very good source rock in the complex petroleum system of the carpathian overthrust belt

authigenic carbonates from an active cold seep of the northern south china sea new insights into fluid sources and past seepage activity abstract site f also named formosa ridge represents the most vigorous cold seep on the northern south china sea continental slope in order to constrain the fluid sources and intensities of seepage we investigated the petrography mineralogy stable carbon and oxygen isotopic compositions element geochemistry and radiocarbon dating of authigenic carbonate rocks retrieved from the seafloor carbonate rocks mainly occurred as crusts nodules and nodular masses incorporated in carbonate breccias the carbonates were comprised mainly of high mg calcite and aragonite the 13 c of authigenic carbonate varied from 55 3 to 34 3 mean 48 5 n 47 vs v pdb suggesting biogenic methane is the dominant carbon source fuelling the system the 18 o carbonate values were from 3 6 to 4 8 mean 3 9 n 47 the observed 18 o enrichement in relation to calculated equilibrium values in the carbonates probably reflects dissolution of gas hydrates combination of seafloor observations and the obtained ams 14 c ages suggest that 1 initiation of methane seepage from at least 10 6 ka ago 2 environmental conditions may have been favorable for enhanced fluid seepage around 6 ka bp and 3 relatively low intensity of seepage from 2 ka bp till today

geological features controlling factors and potential prospects of the gas hydrate occurrence in the east part of the pearl river mouth basin south china sea abstract logging while drilling lwd and wireline log cwl data were acquired during china s second gas hydrate drilling expedition gmgs 2 in the east of pearl river mouth basin south china sea disseminated and massive gas hydrates deposits were found at different sites gas hydrate bearing lithologies identified from the sample coring included the fine grained sediments and coarse grained sediments lwd logs from site gmgs2 08 indicate significant gas hydrate in clay bearing sediments including two layers with massive gas hydrate with a bulk density near to 1 08 g cm3 high electrical resistivities with a range of 2 5 2000 0 m and high p wave velocities are simultaneously observed in the hydrate bearing sediments the average gas hydrate saturation estimated from the pore water freshing analysis ranges from 45 to 55 of the pore space buried carbonate layers above the massive gas hydrate deposit discovered at sites gmgs2 08 indicate that the formations are likely to have formed initially at the surface and then were buried significant high amplitude seismic anomalies discontinuous bottom simulating reflection bsr and blanking zone are detected in the drilling zone the hydrate bearing sediments predominantly consist of silty clay and limestone grains in which the gas hydrates are deposited primarily in the form of laminated massive veins or nodule the gas hydrates occurrences are subjected to the sediment lithology new tectonic activities migration of fluid and gas and also the factors such as heat flow salinity and time which affect the nucleation of gas hydrates its natural morphologies present massive laminated nodular nugget and disseminated of which the former four often formed in shallow fault inter layer s weak cementation zone and on the seabed the buried gas hydrates with high saturation are good zones for gas hydrate exploitation

stable isotope patterns of coexisting pyrite and gypsum indicating variable methane flow at a seep site of the shenhu area south china sea aggregates of authigenic pyrite and gypsum were found at site hs373 in the shenhu seepage area south china sea most of the pyrite occurs as tubes consisting of framboids gypsum aggregates are mainly represented by rosettes and some of them grew over pyrite revealing that gypsum precipitation postdated pyrite formation at seeps extensive sulfate driven anaerobic oxidation of methane aom commonly leads to the accumulation of 34s enriched sulfide resulting in the formation of 32s depleted pyrite the sulfur isotopic composition of pyrite at site hs373 reveals a great variability of 75 5 in 34s values spanning from 37 6 to 37 9 v cdt with a distinct trend towards higher values with increasing depth this trend indicates an increase of the effect of sulfate driven aom with depth whereas pyrite at shallow depth apparently resulted mostly from organiclastic sulfate reduction to date reports on coexisting pyrite and gypsum in seep environments are limited and therefore the mechanism of gypsum formation is insufficiently understood this is the first time that the sulfur and oxygen stable isotope composition of gypsum has been analyzed to understand its formation at seeps the 34s values of gypsum vary from 24 5 to 0 9 revealing a similar trend with depth like pyrite the 18ogypsum values range from 5 3 to 12 3 v smow with a scattered trend to lower values with depth the combined evidence reveals that gypsum formation was linked to the establishment of more oxidizing conditions probably caused by waning seepage this led to the oxidation of pyrite and the associated increase in pore water sulfate and acidity which favored carbonate mineral dissolution providing the calcium ions required for gypsum formation the observed isotopic variability of gypsum suggests that oxidation occurred by different mechanisms at different depth whereby pyrite oxidation was dominated by aerobic processes at shallow depth involving dissolved molecular oxygen and by anaerobic processes at greater depth involving electron acceptors like ferric iron taken together the stable isotope compositions of pyrite and gypsum suggest that the redox conditions within the studied sediments were variable such variability was controlled by complex factors among which changes in seepage activity have been instrumental for the vertical displacement of the sulfate methane transition zone

oil source rock correlations in the polish flysch carpathians and mesozoic basement and organic facies of the oligocene menilite shales insights from hydrous pyrolysis experiments the oligocene menilite shales in the study area in the polish flysch carpathians are organic rich and contain varying mixtures of type ii type iis and type iii kerogen the kerogens are thermally immature to marginally mature based on atomic h c ratios and rock eval data this study defined three organic facies i e sedimentary strata with differing hydrocarbon generation potentials due to varying types and concentrations of organic matter these facies correspond to the silesian unit and the eastern and western portions of the skole unit analysis of oils generated by hydrous pyrolysis of outcrop samples of menilite shales demonstrates that natural crude oils reservoired in the flysch sediments appear to have been generated from the menilite shales natural oils reservoired in the mesozoic basement of the carpathian foredeep appear to be predominantly derived and migrated from menilite shales with a minor contribution from at least one other source rock most probably within middle jurassic strata definition of organic facies may have been influenced by the heterogeneous distribution of suitable menilite shales outcrops and producing wells and subsequent sample selection during the analytical phases of the study

factors influencing methane derived authigenic carbonate formation at cold seep from southwestern dongsha area in the northern south china sea this paper carried out mineral and geochemical studies on a profile through a diagenetic methane derived authigenic carbonate sample that was collected from southwestern dongsha area of the northern south china sea five samples locating in the cross sectional middle mainly consist of dolomite and quartz and two samples close to the surface have a small amount of mg calcite the delta c 13 values of the samples vary between 30 59 and 0 30 vpdb with delta o 18 values ranging from 3 07 to 3 59 vpdb delta ca 44 40 values ranging from 1 35 to 1 47 srm915a indicating a contribution of methane to the carbon pool where the precipitation of authigenic carbonates occurred based on the isotope values alone it can not be distinguished if the carbon source is thermogenic gas or a mixture of biogenic methane and marine dissolved inorganic carbon the delta o 18 values are in general consistent with dolomite precipitation from a fluid similar to present seawater the observed small variation might be related to the oxygen isotope composition of seep fluid the relative small range in calcium isotope values suggests that relatively constant growth conditions and precipitation from seawater the central part of the carbonate nodule formed under the strong influence of methane seepage and the external part is less influenced by methane either due to reduced methane flux to the surface or caused by erosional exhumation of the carbonate nodule from greater depth to the sediment surface

development of the mars microbeam raman spectrometer mmrs 1 raman spectroscopy is a powerful tool for mineral characterization and for detection of water and organic and inorganic forms of carbon the mars microbeam raman spectrometer mmrs is designed for close up analysis of rocks and soils in planetary surface exploration the mmrs consists of a probe in a flight unit to be deployed by a robotic arm and a spectrograph laser source and electronics in a flight unit to reside on a rover or lander the raman probe has a scanning optical bench that enables a 1 cm linear traverse across a target rock or soil both on target materials as encountered and on fresh surfaces of rocks exposed by abrasion or coring from these spectra one can identify major minor and trace minerals obtain their approximate relative proportions and determine chemical features e g mg fe ratio and rock textural features e g mineral clusters amygdular fill and veins one can also detect and identify organic species graphitic carbon and water bearing phases extensive performance tests have been done on a brassboard model of the mmrs using a variety of geological materials minerals rocks martian meteorites etc these tests show that a raman spectrometer can be built that is suitably miniaturized sufficiently robust and low enough in power usage to serve as an on surface planetary instrument yet the spectrometer can retain high detection sensitivity and yield near laboratory quality spectra over a broad wavelength range these features are essential to provide definitive mineralogy in a planetary exploration

composition and origin of coalbed gases in the lower silesian basin southwest poland abstract coalbed gases in the lower silesian coal basin lscb of poland are highly variable in both their molecular and stable isotope compositions geochemical indices and stable isotope ratios vary within the following ranges hydrocarbon chc index chc ch4 c2h6 c3h8 from 1 1 to 5825 wet gas c2 index c2 c2h6 c3h8 c4h10 c5h12 ch4 c2h6 c3h8 c4h10 c5h12 100 from 0 0 to 48 3 co2 ch4 cdmi index cdmi co2 co2 ch4 100 from 0 1 to 99 9 13c ch4 from 66 1 to 24 6 d ch4 from 266 to 117 13c c2h6 from 27 8 to 22 8 and 13c co2 from 26 6 to 16 8 isotopic studies reveal the presence of 3 genetic types of natural gases thermogenic ch4 higher gaseous hydrocarbons and co2 endogenic co2 and microbial ch4 and co2 thermogenic gases resulted from coalification processes which were probably completed by late carboniferous and early permian time endogenic co2 migrated along the deep seated faults from upper mantle and or magma chambers minor volumes of microbial ch4 and co2 occur at shallow depths close to the abandoned mine workings late stage microbial processes have commenced in the upper cretaceous and are probably active at present however depth related isotopic fractionation which has resulted from physical and physicochemical e g diffusion and adsorption desorption processes during gas migration cannot be neglected the strongest rock and gas outbursts occur only in those parts of coal deposits of the lscb which are dominated by large amounts of endogenic co2

is there evidence for a substantial contribution of prokaryotic biomass to organic carbon in phanerozoic carbonaceous sediments the role of prokaryotes bacteria and archaea in producing biomass and reworking settling and buried organic matter is of paramount importance since it exerts a major impact on the composition of sedimentary organic matter and ultimately petroleum this key role of prokaryotes in combination with a biomarker fingerprint often dominated by prokaryotic molecular fossils e g hopanoids has led to the assumption that prokaryotic biomass is a substantial source for organic carbon in carbonaceous sediments however biosynthesising and reworking organic matter does not necessarily imply sourcing organic matter by the prokaryotes and the abundance of biomarkers does not always reflect relative contributions to sedimentary organic matter in this paper the existing evidence for a substantial prokaryotic biomass contribution to sedimentary organic carbon oc is critically evaluated this shows that despite the often prominent presence of prokaryotic biomarkers in sediments evidence for a substantial prokaryotic contribution to sedimentary oc is generally lacking this is demonstrated by i the application of the carbon isotopic mass balance principle in various sedimentary settings ii an alternative explanation for the proposed dominant role of heterotrophic reworking in the oxford clay iii a summary of the effects of bacterial oxidation in organic matter rich turbidites and iv recent data showing that the evidence for recalcitrant carbon in prokaryotes is scant although these observations do not rule out substantial contributions of prokaryotic carbon to oc in phanerozoic carbonaceous sediments this remains to be demonstrated and the final answer awaits the development of new technologies to full characterise sedimentary oc

future acidification of marginal seas a comparative study of the japan east sea and the south china sea the response of marginal peripheral seas to ocean acidification on short and long time scales is not well established through modeling we examine the future acidification of two adjacent marginal seas the south china sea scs and the japan east sea j es our results illustrate the importance of unique features in determining their acidification the j es basin will become completely undersaturated with regard to calcite rapidly in the next few decades while the scs basin will experience relatively slower acidification during its acidification the j es will continually act as a sink for atmospheric co2 whereas the scs will temporarily switch from a source to a sink during the peak pco2 interval only to return slowly to being a source again marginal sea acidification will be determined by multiple factors including their connections with the open ocean and their unique physical and biogeochemical dynamics in addition to the level of atmospheric co2

melting of the patagonian ice sheet and deglacial perturbations of the nitrogen cycle in the eastern south pacific local 230 th normalized biogenic vertical fluxes from the chilean continental margin they document in detail the sharp transition from relatively low wcd rates during the last glacial maximum lgm to high ones during the deglaciation and holocene but give no evidence that the glacial interglacial difference of wcd could have been caused by changes in local primary productivity furthermore we found no evidence that changes in ventilation due to samw formation could explain the nitrogen isotope record we present evidence for an alternative mechanism related to the melting of the patagonian ice sheet pis which is consistent with recent published proxy data and the regional physical oceanography

u th dating of cold seep carbonates an initial comparison authigenic carbonates from hydrocarbon seeps are unique archives of past seepage and associated environmental parameters in order to constrain the ages of a set of seep carbonates and the time involved in carbonate formation we applied uranium thorium u th dating to samples from the gulf of mexico the congo fan and the black sea the resulting u th ages indicate that environmental conditions must have been favorable for enhanced methane rich fluid seepage during the time intervals of 53 4 to 1 7 ka bp for the gulf of mexico and 45 5 to 3 0 ka bp for the congo fan the seep carbonates from the black sea formed at 1 6 to 1 1 ka bp our results suggest that enhanced fluid flow during these time intervals was closely related to 1 sea level variations associated with glacial interglacial cycles and 2 environmental alterations in the course of late quaternary climate change including variations in bottom water temperatures that affected the stability of gas hydrate reservoirs

application of laser raman micro analyses to earth and planetary materials abstract raman spectroscopy contributed greatly in the past 30 years or so for the advances of our understanding of earth and planetary materials and their associated geological processes after a brief introduction of the history and basic theory of raman spectroscopy the advantages and disadvantages of this spectroscopic analysis method were listed and examples were given when appropriate for its applications to the analyses of earth materials which include minerals and organic materials silicate glasses and melts aqueous solutions and gases and h2o gas systems previous works were discussed and cited this was followed by a review on applications of raman spectroscopic studies of minerals and fluids to petrogenesis and crustal evolution in which several p t diagrams were given to show metamorphic evolution of ultra high pressure units as well as a schematic cross section of the earth s outer shells showing recycling of crustal materials in different tectonic regimes for its applications to the analyses of planetary materials which include lunar samples martian meteorites and other extraterrestrial materials a brief history on the starting and development of raman spectroscopy technique was given we then discussed raman point counting and quantitative chemical analysis methods developed for obtaining quantitative information on mineral proportions and mineral chemistry in planetary surface explorations respectively finally new developments and future works which include quantitative analyses raman mapping portable raman systems and raman effects resonance raman spectroscopy cars sers and their associated applications were discussed

authigenic carbonates from methane seeps of the northern congo fan microbial formation mechanism abstract authigenic carbonates were collected from methane seeps at hydrate hole at 3113 m water depth and diapir field at 2417 m water depth on the northern congo deep sea fan during rv meteor cruise m56 the carbonate samples analyzed here are nodules mainly composed of aragonite and high mg calcite abundant putative microbial carbonate rods and associated pyrite framboids were recognized within the carbonate matrix the 13c values of the hydrate hole carbonates range from 62 5 to 46 3 pdb while the 13c values of the diapir field carbonate are somewhat higher ranging from 40 7 to 30 7 pdb indicating that methane is the predominant carbon source at both locations relative enrichment of 18o 18o values as high as 5 2 pdb are probably related to localized destabilization of gas hydrate the total content of rare earth elements ree of 5 hno3 treated solutions derived from carbonate samples varies from 1 6 ppm to 42 5 ppm the shale normalized ree patterns all display positive ce anomalies ce ce 1 3 revealing that the carbonates precipitated under anoxic conditions a sample from hydrate hole shows a concentric lamination corresponding to fluctuations in 13c values as well as trace elements contents these fluctuations are presumed to reflect changes of seepage flux

identification of aryl isoprenoids in source rocks and crude oils biological markers for the green sulphur bacteria abstract a series of c13 to c31 aryl isoprenoids 1 alkyl 2 3 6 trimethylbenzenes have been identified in reef hosted oils and their source rocks from the middle and upper silurian of the michigan basin and middle devonian of the alberta basin canada their structure has been confirmed by unambiguous synthesis of the c14 member of the series their structure and isotopic composition indicate that they are derived from isorenieratene from the chlorobiaceae family of sulphur bacteria these results are consistent with geological and geochemical studies that show that the source rocks were deposited under metahaline to hypersaline sulphate and sulphide rich water columns the distribution of other biomarkers in these oils and source rocks indicates that a diverse biota contributed organic matter to the source environment in conjunction with the aryl isoprenoids they show that there is a remarkable similarity in composition between the two sets of oils and source rocks despite their great temporal and geographic separation this reflects the similarity of their environments and emphasizes the importance of sedimentary facies in controlling the composition of organic matter in source rocks and their derived oils

resources for paleoceanographic and paleoclimatic analysis a 6 700 year stratigraphy and regional radiocarbon reservoir age δr record based on varve counting and 14c ams dating for the santa barbara basin offshore california u s a abstract holocene sediments from the central santa barbara basin sbb contain invaluable paleoceanographic information and document paleoclimatic supra regional teleconnections the well constrained dating and stratigraphy of the sbb can serve as a model for the paleoclimatic exploitation of laminated sediments elsewhere here we present an improved 6 700 yr master chronology that is based on sequential downcore counting of annual varves and 14c ams dating starting from the june 2004 sediment surface diagnostic lamination patterns and the presence of prominent marker layers in an 9 m long sequence of x radiographic images from various cores including odp hole 893a and piston core 6p offer convenient dating for other central sbb sediment cores via direct x radiographic and or visual correlation against the master chronology presented here the new sequence of x radiographs of piston core 6p spans the coring hiatus at 7 04 mbsf in odp hole 893a varve count ages agree well with an independent chronology based on calibrated 14c ages of planktic foraminifers in contrast 14c ages of benthic foraminifers and of kerogen from flood layers are more strongly affected by variable 14c reservoir effects and are therefore of limited value for absolute dating of sbb sediment layers a late holocene shift towards larger 14c age differences between planktic and benthic foraminifers after 2 000 yr b p suggests influx of a more 14c depleted thus older and oxygen depleted source of sub sill bottom water into the sbb consistent with the absence of bioturbating benthos and the enhanced preservation of varves observed in the cores the independent varve chronology allowed us to derive a record of the regional radiocarbon reservoir age r by comparing with the 14c dates for the last 6 700 years

disparities in glacial advection of southern ocean intermediate water to the south pacific gyre highlights surface mg ca temperatures and salinities show comparable glacial conditions subsurface mg ca temperatures suggest that lgm is 3 to 2 c colder than mis 6 relative to holocene subsurface salinities suggest fresher lgm and saltier mis 6 thermal gradients suggest stratified lgm and well mixed mis 6 water column contrasting glacial scenarios suggest variable formation and advection of soiws abstract the intermediate waters formed in the southern ocean are critical for ventilating the thermocline in the southern hemisphere gyres and transporting climatic signals from high to low latitudes on glacial interglacial time scales despite the importance of the southern ocean intermediate waters soiws information on past changes in soiws formation is fragmentary and its impact on the south pacific gyre spg s thermocline largely unknown here we present a 200 kyr record of paired mg ca ratios and stable oxygen isotope from surface and deep dwelling planktonic foraminifera from the spg on average the globigerina bulloides mg ca derived sea surface temperatures show similar conditions during the lgm and marine isotope stage mis 6 9 4 c versus 9 8 c in contrast the subsurface temperatures derived from the mg ca values of globorotalia inflata and globorotalia truncatulinoides suggest that lgm is 3 to 2 c colder than mis 6 furthermore at subsurface depths the reconstructed 18osw ivc record proxy for relative local salinity changes suggests opposite glacial conditions with slightly saltier than holocene waters during mis 6 and fresher than holocene waters during lgm contrasting glacial scenarios plausibly due to changes in the presence of soiws at the study site suggest variable formation and or advection of soiws to the spg during different glacial stages the variability in soiws is probably driven by the changes in the intensity of the southern westerly winds

authigenic carbonates from seeps on the northern continental slope of the south china sea new insights into fluid sources and geochronology seep carbonates represent excellent archives of seepage activities near seafloors in order to provide insights on sources of seeping fluids stable carbon and oxygen isotopes and sr 87 sr 86 ratios were applied to seep carbonates from shenhu sw dongsha and ne dongsha on the northern continental slope of the south china sea u th dating was selected to constrain the time involved in carbonate formation and the potential driving force the delta c 13 values of the shenhu and ne dongsha carbonates vary from 52 3 parts per thousand to 32 6 parts per thousand v pdb indicating that biogenic methane is the primary carbon source at both locations the delta c 13 values of the sw dongsha carbonates are much higher ranging from 18 8 parts per thousand to 11 parts per thousand v pdb suggesting that thermogenic methane is the predominant carbon source in this region a relatively deep origin of thermogenic methane for the sw dongsha seeps is also supported by somewhat lower sr 87 sr 86 ratios of the samples from 0 709025 to 0 709097 the delta o 18 values of the shenhu and ne dongsha carbonates vary from 1 4 to 5 1 v pdb while the delta o 18 values of the sw dongsha carbonates range from 2 5 to 3 4 v pdb many samples from shenhu and ne dongsha demonstrate an o 18 enriched fluid source that most likely originated from waters released from the dissociation of locally abundant gas hydrate u th ages of the shenhu carbonates show a large range from 330 ka to 152 ka bp and the ne dongsha carbonates have ages from 77 ka to 63 ka bp interestingly u th ages of most samples are either within times of sea level lowstands or correspond to periods when the sea level was falling taken together our data suggest that in the south china sea gas hydrate dissociation during sea level lowstands or falling stages resulted from reduced hydrastastic pressures which in turn enhanced the seep activities and promoted the formation of authigenic carbonates close to the seafloor c 2013 elsevier ltd all rights reserved

gas hydrate destabilization enhanced dewatering benthic material turnover and large methane plumes at the cascadia convergent margin mixed methane sulfide hydrates and carbonates are exposed as a pavement at the seafloor along the crest of one of the accretionary ridges of the cascadia convergent margin vent fields from which methane charged low salinity fluids containing sulfide ammonia 4he and isotopically light co2 escape are associated with these exposures they characterize a newly recognized mechanism of dewatering at convergent margins where freshening of pore waters from hydrate destabilization at depth and free gas drives fluids upward this process augments the convergence generated overpressure and leads to local dewatering rates that are much higher than at other margins in the absence of hydrate discharge of fluids stimulates benthic oxygen consumption which is orders of magnitude higher than is normally found at comparable ocean depths the enhanced turnover results from the oxidation of methane hydrogen sulfide and ammonia by vent biota the injection of hydrate methane from the ridge generates a plume hundreds of meters high and several kilometers wide a large fraction of the methane is oxidized within the water column and generates 13c anomalies of the dissolved inorganic carbon pool

argo profiling floats document subantarctic mode water formation west of drake passage 1 subantarctic mode water samw the precursor of antarctic intermediate water which occupies the 600 to 1100 m layer of the water column in the oceans of the southern hemisphere is formed in the southern oceans north of the polar frontal zone 56 60 s where saltier upper deep water is upwelled close to the surface the surface layer there in contrast is determined by fresher water which occupies about the upper 100 m of the water column during austral summer surface cooling during austral winter initiate vertical convection which supposedly homogenizes several hundreds of meters of the upper water column hereby transforming saltier upper deep water to lighter samw by incorporating fresh subantarctic surface water here we show the formation process of samw west of drake passage as documented by autonomous profiling floats vertical convection exceeds 500 m during september and october but only south of 56 s

jiulong methane reef microbial mediation of seep carbonates in the south china sea chemoherm carbonates as well as numerous other types of methane seep carbonates were discovered in 2004 along the passive margin of the northern south china sea lithologically the carbonates are micritic containing peloids clasts and clam fragments some are highly brecciated with aragonite layers of varying thicknesses lining fractures and voids dissolution and replacement is common mineralogically the carbonates are dominated by high magnesium calcites hmc and aragonite some hmcs with mgco3 contents of between 30 38 mol extreme hmc occur in association with minor amounts of dolomite all of the carbonates are strongly depleted in 13c with a range from 35 7 to 57 5 pdb and enriched in 18o 4 0 to 5 3 pdb abundant microbial rods and filaments were recognized within the carbonate matrix as well as aragonite cements likely fossils of chemosynthetic microbes involved in carbonate formation the microbial structures are intimately associated with mineral grains some carbonate mineral grains resemble microbes the isotope characteristics the fabrics the microbial structure and the mineralogies are diagnostic of carbonates derived from anaerobic oxidation of methane mediated by microbes from the succession of hmcs extreme hmc and dolomite in layered tubular carbonates combined with the presence of microbial structure and diagenetic fabric we suggest that extreme hmc may eventually transform into dolomites our results add to the worldwide record of seep carbonates and establish for the first time the exact locations and seafloor morphology where such carbonates formed in the south china sea characteristics of the complex fabric demonstrate how seep carbonates may be used as archives recording multiple fluid regimes dissolution and early transformation events

organic geochemical study and genetic correlation of natural gas oil and menilite source rocks in the area between san and stryi rivers polish and ukrainian carpathians abstract we studied the source rocks and petroleum accumulations in the carpathian mountains of the polish ukrainian border area between the san and stryi rivers a total of 108 oligocene menilite formation rock samples 12 oil and 15 gas samples accumulated in the oligocene reservoirs and one oil and gas sample from an upper cretaceous reservoir were analysed the aim of this study was to evaluate the petroleum potential of the menilite formation in this area and to evaluate potential genetic correlations between source rock and petroleum the menilite formation represents a prolific source rock with toc content ranging from 2 to 7 wt locally exceeding 20 wt algal type ii and mixed type ii iii kerogens dominate but sometimes type iii kerogen and rarely type i kerogen occur thermal maturity of the oligocene menilite formation increases from outer to inner tectonic units from the immature in the boryslav pokuttya and skole units to the overmature in the southern parts of silesian and dukla units as a consequence petroleum potential decreases in the same order geochemical analyses reveal that oil and gas generation and migration processes within the carpathian flysch succession are complicated all analysed oils were generated from the menilite formation during early and peak stages of the oil window associated gas is of low temperature thermogenic origin sometimes containing an admixture of microbial gas high temperature thermogenic gas occurs only in the polish part of the silesian unit

initial results of comparing cold seep carbonates from mussel and tubeworm associated environments at atwater valley lease block 340 northern gulf of mexico abstract chemosymbiotic macrofauna such as mussels and tubeworms and authigenic carbonates are typical of many hydrocarbon seeps to address whether mussels and tubeworms could impact the sediment geochemistry of their habitat where authigenic carbonates are precipitated a comparative study of petrographic and geochemical features of the authigenic carbonates from mussel and tubeworm associated environments at hydrocarbon seeps in atwater valley lease area block 340 at340 of the gulf of mexico was undertaken both mussel and tubeworm associated carbonates are dominated by high magnesium calcite hmc and aragonite and two tubeworm associated carbonate samples have minor amounts of dolomite the 13c values of all carbonates are low ranging from 60 8 to 35 5 pdb although there is much overlap surprisingly the 13c values of mussel associated carbonates are generally higher than those of tubeworm associated carbonates 51 8 vs 54 8 for an average of over 60 subsamples it is suggested that 1 carbon isotopic vital effect of seep mussels and tubeworms 2 fluid physical pumping of mussels and 3 release of sulfate by tubeworm roots may be responsible for the relatively lower 13c values of tubeworm associated carbonates it has been suggested that the heterogeneities in mineralogy and stable carbon isotope geochemistry of the seep carbonates may be attributed to the activity of macrofauna mussels and tubeworms and associated microbes our observations also suggest that at at340 the geochemical evolution of seep macrofauna is from a mussel dominated environment to a mixed mussel tubeworm environment and finally to a mostly tubeworm dominated environment this evolution is controlled mainly by the habitat e g hydrocarbon seep flux

formation regions of subantarctic mode water detected by ofes and argo profiling floats 1 we investigated the distribution of the deep mixed layer in the southern ocean where subantarctic mode water samw forms by using argo profiling floats and the ocean general circulation model for the earth simulator ofes the mixed layer depth mld generally increased eastward from 50 180 e and from 180 80 w with distinct local maxima near major bathymetric features a sudden transition from deep to shallow mixed layer was found along the equatorward limit of the deep mixed layer this diagnosed mld front coincides with the line of ug s 0 indicating the distributions of the general deepening and local maxima of mld were affected by near surface geostrophic flow the flow is steered by the major bottom topographies and the local mld maxima occurred where the flow direction was deflected southward this implies a link between the bathymetric features and formation of thick samw

seep carbonates and preserved methane oxidizing archaea and sulfate reducing bacteria fossils suggest recent gas venting on the seafloor in the northeastern south china sea seep carbonates formed by the synergistic metabolism of methane oxidizing archaea moa and sulfate reducing bacteria srb have been found in many places worldwide but have not been found to date in the south china sea mud volcanoes and shale diapirs have been reported in the south china sea however and microscope and geochernical analysis of carbonates dredged where bottom simulating reflectors bsr suggest the presence of gas hydrate on the northeastern continental slope of the south china sea suggest that the carbonates are hydrocarbon seep related carbonates the carbonates we dredged are chimney like and preserve moa srb fossils their very light carbon isotopic compositions 51 25 to 51 76 parts per thousand suggest that their carbon was derived from microbial methane oxidization these seep carbonates and their preserved moa srb fossils imply gas venting has occurred recently on the seafloor in the northeastern continental slopes in the south china sea c 2005 elsevier ltd all rights reserved

geochemical record of methane seepage in authigenic carbonates and surrounding host sediments a case study from the south china sea abstract sediments at marine methane seep sites provide potential archives of past fluid flow that serve to explore seepage activities over time three gravity cores d 8 d f and d 7 were collected from seep sites on the northern slope of the south china sea where gas hydrates were drilled in the subsurface various carbon and sulfur contents 13c values of total inorganic carbon 13ctic 34s values of chromium reducible sulfur 34scrs trace element contents grain size and ams 14c dating of planktonic foraminifera in the sediments were determined to explore the availability of related proxies at seeps and to trace past methane seepage activities evidence for the presence of methane seepage and consequently anaerobic oxidation of methane comes from the occurrence of 13c depleted authigenic carbonate nodules 13c values as low as 49 discovered at an interval of 150 200 cm in core d 7 this finding is supported by high s c ratios and molybdenum enrichment in the same interval however low contents of crs and negative 34scrs values are present it is suggested to reflect a transient methane seepage event which continued for about 1 ka based on the 14c ages cores d 8 and d f have 13ctic values close to zero low s c ratios and crs contents negative 34scrs values and no trace element enrichment suggesting a negligible impact of methane seepage on the sediments the negative 34scrs values of the studied seep impacted and background sediments suggest that the application of 34scrs alone as a proxy to identify aom related process may be insufficient sediment carbon sulfur trace element systematics and 14c ages used here have the potential to be a promising tool to recognize transient methane seepages and constrain their timescales

in situ raman analyses of deep sea hydrothermal and cold seep systems gorda ridge and hydrate ridge the deep ocean raman in situ spectrometer doriss instrument was deployed at the sea cliff hydrothermal field and hydrate ridge in july 2004 the first in situ raman spectra of hydrothermal minerals fluids and bacterial mats were obtained these spectra were analyzed and compared to laboratory raman measurements of standards and samples collected from the site spectra of vent fluid 294 c at the orifice at 2700 m depth were collected with noncontact and immersion sampling optics compared to spectra of ambient 2 c seawater the vent fluid spectra show changes in the intensity and positions of the water o h stretch bands due to the elevated temperature the sulfate band observed in seawater spectra is reduced in vent fluid spectra as sulfate is removed from vent fluid in the subseafloor additional components of hydrothermal fluid are present in concentrations too low to be detected with the current raman system a precision underwater positioner pup was used to focus the laser spot on opaque samples such as minerals and bacterial mats spectra were obtained of anhydrite from actively venting chimneys and of barite deposits in hydrothermal crusts laboratory analysis of rock samples collected in the vent field also detected the presence of gypsum spectra of bacterial mats revealed the presence of elemental sulfur s8 and the carotenoid beta carotene challenges encountered include strong fluorescence from minerals and organics and insufficient sensitivity of the instrument the next generation doriss instrument addresses some of these challenges and holds great potential for use in deep sea vent environments

coupled pyrite concentration and sulfur isotopic insight into the paleo sulfate methane transition zone smtz in the northern south china sea abstract the sulfate methane transition zone smtz is an important diagenetic redox boundary within marine sediments where the anaerobic oxidation of methane aom coupled with bacterial sulfate reduction can promote sulfur isotopic enrichments in several solid phase minerals including pyrite fes2 authigenic pyrite can form in concentrated abundances within the smtz and as such can be used as a proxy to identify paleo smtzs this study uses enrichments in 34s and anomalously high abundances of authigenic pyrites in 287 samples from the northern south china sea scs to determine the paleo smtz the pyrite samples were collected from sediment cores acquired at three sites each of which are known to be located in natural gas hydrate bearing regions we assess the relative abundances of authigenic pyrites the types of pyrite morphologies recovered in the cored sediments and the sulfur isotopic values of recovered pyrite samples using two methods 1 handpicked sample analysis using a binocular microscope and 2 the chromium reduction method our results show that pyrite concentrations and sulfur isotopic compositions exhibit synchronous fluctuations particularly from 6 8 m below seafloor mbsf to 8 4 mbsf at all three study sites there is a significant increase in the occurrence of rod like pyrite morphology within this key interval we define the position of the paleo smtz by the presence of anomalously high accumulations of pyrites at greater than 5 0 wt using the handpicking method or greater than 0 5 wt via the chromium reduction method along with positive 34s excursions greater than 10 0 vcdt we discovered a regional paleo smtz that is shallower than the modern smtz suggesting a previous period of elevated methane flux from depth possibly related to widespread gas hydrate dissociation

geochemistry of oils from the northern timan pechora basin russia abstract a geochemical study of 36 oils from the northern timan pechora basin indicates four oil types two types of sulfur rich oils range 1 4 2 5 sulfur can be identified on the basis of both gross and molecular properties these oils are found primarily in the toravey south toravey and roman trebs fields they are also present in the offshore prirazlom field thereby extending the geographic range of sulfur rich oils into the pechora sea another oil type exhibits a distinctive odd predominance of n alkanes in the range n c 11 through n c 19 and a diminished abundance of n alkanes greater than c 19 these oils which occur primarily in the a titov and labogan fields show striking similarities to ordovician sourced oils from other paleozoic basins throughout the world their biomarker and isotopic compositions for example bear a strong resemblance to oils generated from the ordovician viola limestone of the anadarko basin the fourth oil type occurs in the northwestern portion of the basin in the khylchuyu field some mixing between the various types is evident light oils and condensates of the peschano ozyor shtokman rusanov and vasilkovo fields cannot be readily assigned to any of these four types the upper devonian domanik formation is generally thought to be the major oil source in the timan pechora basin however geochemical characteristics of timan pechora oils analyzed do not closely resemble those of other upper devonian source oils such as those generated from the duvernay formation of western canada these differences might reflect variations in the organic matter preserved in the two basins during the late devonian or may indicate that the upper devonian is not an important hydrocarbon source in the northern timan pechora region the results suggest that the timan pechora oils analyzed are generated from paleozoic carbonate or calcareous shale source rocks at least one of which appears to be of ordovician age

satellite gravity anomalies and their correlation with the major tectonic features in the south china sea abstract the south china sea scs is a region of interaction among three major plates the pacific indo australian and eurasian the collision of the indian subcontinent with the eurasian plate in the northwest back arc spreading at the center and subduction beneath the philippine plate along manila trench in the east and the collision along palawan trough in the south have produced complex tectonic features within and along the scs this investigation examines the satellite derived gravity anomalies of the scs and compares them with major tectonic features of the area a map of bouguer gravity anomaly is derived in conjunction with available seafloor topography to investigate the crustal structure the residual isostatic gravity anomaly is calculated assuming that the cenozoic sedimentary load is isostatically compensated the features in the gravity anomalies in general correlate remarkably well with the major geological features including offsets in the seafloor spreading segments major faults basins seamounts and other manifestations of magmatism and volcanism on the seafloor they also correlate with the presumed location of continental oceanic crust boundary the region underlain by oceanic crust in the central part of the scs is characterized by a large positive bouguer gravity anomaly 220 330 mgal as well as large free air and residual isostatic anomalies there are however important differences among spreading segments for example in terms of free air gravity anomaly the southwest section of mid ocean has an approximately 50 km wide belt of gravity low superimposed on a broad high of 45 mgal running nw se whereas there are no similar features in other spreading segments there are indications that gravity anomalies may represent lateral variation in upper crustal density structure for instance free air and isostatic anomalies show large positive anomalies in the east of the namconson basin which coincide with areas of dense volcanic material known from seismic surveys the red river fault system are clearly identified in the satellite gravity anomalies including three major faults songchay fault in the southwest songlo fault in the northeast and central fault in the center of the basin they are elongated in nw se direction between 20 30 n and 17 n and reach to vietnam scarp fault around 16 30 n it is also defined that the crustal density in the south side of the central basin is denser than that in the north side of the central basin

in situ raman detection of gas hydrates exposed on the seafloor of the south china sea gas hydrates are usually buried in sediments here we report the first discovery of gas hydrates exposed on the seafloor of the south china sea the in situ chemical compositions and cage structures of these hydrates were measured at the depth of 1 130 m below sea level using a raman insertion probe rip gh that was carried and controlled by a remotely operated vehicle rov faxian this in situ analytical technique can avoid the physical and chemical changes associated with the transport of samples from the deep sea to the surface natural gas hydrate samples were analyzed at two sites the in situ spectra suggest that the newly formed hydrate was structure i but contains a small amount of c3h8 and h2s pure gas spectra of ch4 c3h8 and h2s were also observed at the scs sgh02 site these data represent the first in situ proof that free gas can be trapped within the hydrate fabric during rapid hydrate formation we provide the first in situ confirmation of the hydrate growth model for the early stages of formation of crystalline hydrates in a methane rich seafloor environment our work demonstrates that natural hydrate deposits particularly those in the early stages of formation are not monolithic single structures but instead exhibit significant small scale heterogeneities due to inclusions of free gas and the surrounding seawater there inclusions also serve as indicators of the likely hydrate formation mechanism these data also reinforce the importance of correlating visual and in situ measurements when characterizing a sampling site

the mechanism for antarctic intermediate water renewal in a world ocean model abstract realistic representation of the low salinity tongue of antarctic intermediate water aaiw has been achieved in a coarse resolution ocean general circulation model the authors find that this water mass is not generated by direct subduction of surface water near the polar front instead the renewal process is concentrated in the southeast pacific ocean off southern chile the outflow of the east australian current progressively cools by heat loss to the atmosphere and freshens by assimilation of polar water carried north by the surface ekman drift during its slow movement across the south pacific toward the aaiw formation zone further deep warm advection near chile enables more convective overturn resulting in very deep mixed layers from which aaiw is fed into the south pacific and also into the malvinas current along with this isolated region of aaiw renewal the model relies on alongisopycnal mixing of fresh surface water from the polar front to capture a realistic circumpolar tongue

fluid source and methane related diagenetic processes recorded in cold seep carbonates from the alvheim channel central north sea integrated petrography mineralogy geochronology and geochemistry of cold seep carbonate crusts and free gas from the alvheim channel elucidate diagenetic carbonate precipitation and related seepage histories in the central north sea free gas isotope characteristics coupled with carbonate 13c values as low as 66 vpdb indicate a predominantly microbial methane source with minor thermogenic contribution we estimate that 70 of the carbon sequestered into carbonate precipitates was derived from local oxidation of methane the early stage of crust growth is represented by microcrystalline aragonite and mg calcite 10 to 40 mol mgco3 cementing seafloor sediments consisting of clays quartz feldspar and minor detrital low mg calcite and dolomite typical association of aragonite cement with coarse grained detritus may reflect elevated fluid flow and flushing of fine particles prior to cementation close to the seafloor middle rare earth element enrichment in early generation microcrystalline cements containing framboidal pyrite indicates diagenetic precipitation within the zone of anaerobic methane oxidation contiguous to iron reduction the later generation diagenetic phase corresponds to less abundant radial fibrous and botryoidal aragonite which lines cavities developed within the crusts in contrast to early generation cements late generation cavity infills have rare earth elements and y patterns with small negative ce anomalies similar to seawater consistent with carbonate precipitation in a more open seawater dominated system aragonite u th ages indicate carbonate precipitation between 6 09 and 3 46 kyr bp in the northern part of the channel whereas in the southern part precipitation occurred between 1 94 and 0 81 kyr bp reflecting regional changes in fluid conduit position

water column structure during deposition of middle devonian lower mississippian black and green gray shales of the illinois and michigan basins a biomarker approach abstract the extractable organic matter of organic rich black shales and associated organic poor bioturbated green gray shales of the illinois and michigan basins of north america is analyzed to constrain the water column structure during their deposition all black shale samples contain derivatives of the biomarker isorenieratene a diaromatic carotenoid pigment produced exclusively by the brown strain of the green sulfur bacteria chlorobiaceae chlorobiaceae are phototrophic organisms requiring euxinic anoxic and sulfidic conditions to survive and the presence of isorenieratene derivatives indicates that the middle devonian early mississippian epeiric seas of north america experienced bottom water euxinic conditions during black shale deposition analysis of green gray shales also reveals the presence of isorenieratene derivatives and in some cases isorenieratane the highly bioturbated fabric of these sediments indicates the presence of oxygen in bottom waters during their deposition thus we suggest that short term shoaling of the oxycline across the basin slope may have occurred during their deposition though they were deposited predominantly under an oxygenated water column i e above the chemocline most green gray shales contain three pseudohomologous series of branched alkanes with quaternary substituted carbon atoms baqcs which are absent in black shale samples recent studies suggest that baqcs are produced by benthic chemoautotrophs dwelling at the redox boundary separating anoxic sediments from moderately oxygenated waters comparison of the biomarker content i e regular isoprenoid baqcs between black and green gray shales indicates different sources of organic matter and suggests that phytoplanktonic productivity in the upper water column was enhanced during black shale deposition the results of this study indicate that the alternation of green gray and black shales in these basins results from the vertical fluctuations of the chemocline these fluctuations seem to be driven by changes in phytoplanktonic productivity our data when associated to previous studies of other black shales from canada and europe confirm that photic zone euxinia was a widespread feature of low latitude epeiric seas during the middle devonian lower mississippian

southern ocean mixed layer depth from argo float profiles 1 argo float profiles of temperature salinity and pressure are used to derive the mixed layer depth mld in the southern ocean mld is determined from individual profiles using both potential density and potential temperature criteria and a monthly climatology is derived from individual mlds using an objective mapping method quantitative data are available in the auxiliary material the spatial structures of mlds are similar in each month with deep mixed layers within and just north of the antarctic circumpolar current acc in the pacific and indian oceans the deepest mixed layers are found from june to october and are located just north of the acc where antarctic intermediate water aaiw and subantarctic mode water samw are formed examination of individual mlds indicates that deep mixed layers mld 400 m from both the density and temperature criteria are concentrated in a narrow surface density band which is within the density range of samw the surface salinity for these deep mixed layers associated with the samw formation are slightly fresher compared to historical estimates differences in air sea heat exchanges wind stress and wind stress curl in the pacific and indian oceans suggest that the mode water formation in each ocean basin may be preconditioned by different processes wind mixing and ekman transport of cold water from the south may assist the samw formation in the indian ocean in the eastern pacific the formation of mode water is potentially preconditioned by the relative strong cooling and weak stratification from upwelling

methane seepage intensities traced by biomarker patterns in authigenic carbonates from the south china sea authigenic carbonate rocks from an active seep site f located in the south china sea scs at a water depth of 1120 m were studied using mineralogical and lipid biomarker analyses carbonate mineral compositions in specific samples were predominantly aragonite high mg calcite hmc or a mixture of both abundant c 13 depleted lipid biomarkers diagnostic for archaea provide evidence that anaerobic oxidation of methane aom mediated by anaerobic methane oxidizing archaea anme and their bacterial partners are the major processes leading to formation of the carbonates high methane index dominance of anme 2 assemblages and the predominant contribution of aom related biomarkers in the aragonitic carbonate point to the strong impact of aom communities during its precipitation which is likely caused by high seepage intensities the relatively low methane index and abundant allochthonous input of the hmc carbonate are a result of the weak impact of aom microbial communities under conditions of low methane seepage evidence for this interpretation also comes from relatively higher carbonate content lesser contribution of allochthonous organic matter and lower pyrite content in the aragonitic carbonate than in the hmc carbonate high concentrations of c 13 depleted hopanoids were observed in the aragonitic sample which may be a result of the intermittent presence of oxic conditions in an overall anoxic condition possibly induced by changing seepage intensities our data suggests that lipid biomarkers in authigenic carbonate from seep sites can be helpful for improving assessments of the fluid dynamics in such a complex system c 2015 elsevier ltd all rights reserved

aryl isoprenoids and diaromatic carotenoids in paleozoic source rocks and oils from the western canada and williston basins abstract aryl isoprenoids in the range c13 c31 have been identified in source rock bitumens and oils from several paleozoic age petroleum systems in the western canada and williston basins the principal compounds possess the 2 alkyl 1 3 4 trimethyl substitution pattern characteristic of diaromatic carotenoids found in the chlorobiaceae family of photosynthetic sulfur bacteria two c40 perhydrodiaromatic carotenoids which are structurally related to the presumed precursors of the aryl isoprenoids have also been identified in oils and source rock bitumens of the duvernay late devonian petroleum system pyrolysis gas chromatograms of kerogens isolated from several paleozoic source rocks show an unusual abundance of 1 2 3 4 tetramethylbenzene it is proposed that this compound arises from cleavage of diaromatic carotenoid moieties which have been incorporated into the kerogen structure with increasing maturation concentrations of the aryl isoprenoids in duvernay source rock bitumens increase to a point whereas the c40 perhydrodiaromatic carotenoids decrease steadily previous studies have suggested that aryl isoprenoids may be indicators of enhanced salinity environments this is not supported by the present work which shows high concentrations in source rocks associated with presumed normal marine salinities there is however a general association with intervals of condensed clastic or mixed clastic carbonate sedimentation within carbonate depositional systems from the association found and from parallels to modern habitats of photosynthetic bacteria it can be inferred that these biomarkers indicate prolific bacterial growth in a stratified water column at and below the oxic anoxic boundary layer in sub tropical to tropical marine environments

interactions between deformation and fluids in the frontal thrust region of the nantroseize transect offshore the kii peninsula japan results from iodp expedition 316 sites c0006 and c0007 integrated ocean drilling program iodp expedition 316 sites c0006 and c0007 examined the deformation front of the nankai accretionary prism offshore the kii peninsula japan in the drilling area the frontal thrust shows unusual behavior as compared to other regions of the nankai trough drilling results integrated with observations from seismic reflection profiles suggest that the frontal thrust has been active since 0 78 0 436 ma and accommodated 13 to 34 of the estimated plate convergence during that time the remainder has likely been distributed among out of sequence thrusts further landward and or accommodated through diffuse shortening unlike results of previous drilling on the nankai margin porosity data provide no indication of undercompaction beneath thrust faults furthermore pore water geochemistry data lack clear indicators of fluid flow from depth these differences may be related to coarser material with higher permeability or more complex patterns of faulting that could potentially provide more avenues for fluid escape in turn fluid pressures may affect deformation well drained sand rich material under the frontal thrust could have increased fault strength and helped to maintain a large taper angle near the toe recent resumption of normal frontal imbrication is inferred from seismic reflection data associated decollement propagation into weaker sediments at depth may help explain evidence for recent slope failures within the frontal thrust region this evidence consists of seafloor bathymetry normal faults documented in cores and low porosities in near surface sediments that suggest removal of overlying material overall results provide insight into the complex interactions between incoming materials deformation and fluids in the frontal thrust region

chemical biological and hydrological controls on the 14c content of cold seep carbonate crusts numerical modeling and implications for convection at cold seeps understanding the hydrology of cold seep environments is crucial to perform accurate estimates of fluid and chemical fluxes at sedimentary wedges shallow convection processes may affect fluid flux estimates and could favor the destabilization of gas hydrate accumulations increasing the sediment ocean methane flux evidence for the occurrence of convection at cold seeps however is still limited we use the concentration of 14c d14c in carbonate crusts formed at cold seeps of the eastern mediterranean sea as a tracer for convective recirculation of seawater derived fluids a numerical model is applied to investigate the controls on 14c incorporation in cold seep carbonates our simulations show that increased amounts of ch4 in the expelled fluids result in elevated crust d14c while high ca2 and hco3 concentrations produce the opposite effect convection is the only transport process that can significantly increase crust d14c advection bioirrigation eddy diffusion and bioturbation instead have little effect on or produce a decrease of crust d14c in addition the presence of old or modern carbon mc in host sediments prior to cementation and the 14c decay associated to the time needed to form the crust contribute in defining the d14c of carbonate crusts we then use the model to reproduce the 14c content of the eastern mediterranean sea crusts to constrain the chemical and hydrological conditions that led to their formation some crusts contain relatively low amounts of 14c 945 0 d14c 930 2 which assuming no ageing after crust formation can be reproduced without considering convection other crusts from two sites the amsterdam and napoli mud volcanoes instead have a very high 14c content 899 0 d14c 838 4 which can only be reproduced by the model if convection mixes deep fluids with seawater order of magnitude calculations using the rayleigh criterion for convection suggest that the slow seepage about 10 cm year 1 of low salinity 20 fluids at the amsterdam sites could trigger haline convection there on the napoli mud volcano where high density brines are expelled density driven convection cannot take place and other processes possibly involving the rapid movement of free gas in the sediment could be important

cold seep carbonates of the middle and lower continental slope northern gulf of mexico authigenic carbonates from cold seeps on the middle and lower continental slope of the northern gulf of mexico gom exhibit a wide range of mineralogical and stable isotopic compositions these carbonates consist of concretions and nodules in surface sediments hardgrounds of crusts and isolated slabs and mounded buildups of blocks and slabs of up to over 10 meters in relief above the surrounding seafloor mineralogically the carbonates are dominated by high mg calcite hmc and aragonite however low levels 5 wt of dolomite are present in most samples petrographically mg calcite peloidal matrix and acicular to botryoidal aragonitic void filling cements are the most frequent associations the carbon isotopic compositions of the carbonates range from 60 8 to 14 0 pdb indicating complex carbon sources that include 13c depleted biogenic and thermogenic methane biodegraded crude oil seawater co2 and 13c enriched residual co2 from methanogenesis a similarly large variability in 18o values 2 5 to 6 7 pdb demonstrates the geochemical complexity of the slope with some samples pointing toward an 18o enriched oxygen source that is possibly related to advection of 18o enriched formation water and or to the decomposition of gas hydrate a considerable range of mineralogical and isotopic variations in cold seep carbonate composition was noted even within individual study sites however common trends occur across multiple geographic areas this situation suggests that local controls on fluid and gas flux types of seep hydrocarbons the presence or absence of gas hydrate in the near surface sediment and chemosynthetic communities as well as the temporal evolution of the local hydrocarbon reservoir all may play a part in determining carbonate mineralogy and isotope geochemistry the carbon isotope data clearly indicate that between site variation is greater than within site variation seep carbonates formed on the middle and lower continental slope of the gom do not appear to be substantially different from those found on the upper slope 1000 m water depth the highly variable fluids and gases that leave their geochemical imprints on seep carbonate of the middle and lower continental slope are similar to their outer shelf and upper slope counterparts

mineral phase analysis of deep sea hydrothermal particulates by a raman spectroscopy expert algorithm toward autonomous in situ experimentation and exploration 1 this paper demonstrates that a raman spectroscopy point counting technique can be used for phase analysis of minerals commonly found in deep sea hydrothermal plumes even for minerals with similar chemical compositions it also presents our robust autonomous identification algorithm and spectral database both of which were developed specifically for deep sea hydrothermal studies the raman spectroscopy expert algorithm was developed and tested against multicomponent mixtures of minerals relevant to the deep sea hydrothermal environment it is intended for autonomous classification where many spectra must be examined with little or no human involvement to increase analytic precision accuracy and data volume or to enable in situ measurements and experimentation