impact of poroelastic response of sandstones on geothermal power production during geothermal power production using a borehole doublet consisting of a production and injection well the reservoir conditions such as permeability k porosity and skempton coefficient b at the geothermal research site gross schoenebeck germany will change besides a temperature decrease at the injection well and a change of the chemical equilibrium also the pore pressure pp will vary in a range of approximately 44 mpa 10 mpa in our reservoir at 3850 to 4258 m depth this leads to a poroelastic response of the reservoir rocks depending on effective pressure p eff difference between mean stress and pore pressure resulting in a change in permeability k porosity and the poroelastic parameter skempton coefficient b hence we investigated the effective pressure dependency of flechtinger sandstone an outcropping equivalent of the reservoir rock via laboratory experiments the permeability decreased by 21 at an effective pressure range from 3 to 30 mpa the porosity decreased by 11 p eff 6 to 65 mpa and the skempton coefficient decreased by 24 p eff 4 to 25 mpa we will show which mechanisms lead to the change of the mentioned hydraulic and poroelastic parameters and the influence of these changes on the productivity of the reservoir the most significant changes occur at low effective pressures until 15 to 20 mpa for our in situ reservoir conditions p eff 43 mpa a change of 10 mpa effective pressure will result in a change in matrix permeability of less than 4 and in matrix porosity of less than 2 besides natural fracture systems fault zones and induced hydraulic fractures the rock matrix its only one part of geothermal systems all components can be influenced by pressure temperature and chemical reactions therefore the determined small poroelastic response of rock matrix does not significantly influence the sustainability of the geothermal reservoir

pressure dependent production efficiency of an enhanced geothermal system egs stimulation results and implications for hydraulic fracture treatments a series of stimulation experiments were carried out at the geothermal research well in gros schonebeck egrsk 3 90 located in the northeastern part of germany the intended purpose of these experiments was to develop concepts for a productivity increase of the geothermal well to create an enhanced geothermal system egs two different kinds of stimulation types were performed hydraulic gel proppant stimulations were conducted in sandstone sections with high initial permeability then a different fracturing concept was applied injecting high amounts of water this waterfrac stimulation was realized in the entire open section including sandstones and volcanic rocks evidence of the creation and properties of a very long vertical fracture was retrieved from pressure response analyses demonstrating a bilinear flow regime the production efficiency of the produced artificial fractures shows a strong dependence on reservoir pressure at increased reservoir pressure the artificial fractures of all stimulated intervals are highly conductive and subsequently become less conductive during pressure decline hence the range of a suitable reservoir pressure is constrained by this fracture efficiency and limits the usage of this well as an injection well for geothermal power production

new global marine gravity model from cryosat 2 and jason 1 reveals buried tectonic structure gravity models are powerful tools for mapping tectonic structures especially in the deep ocean basins where the topography remains unmapped by ships or is buried by thick sediment we combined new radar altimeter measurements from satellites cryosat 2 and jason 1 with existing data to construct a global marine gravity model that is two times more accurate than previous models we found an extinct spreading ridge in the gulf of mexico a major propagating rift in the south atlantic ocean abyssal hill fabric on slow spreading ridges and thousands of previously uncharted seamounts these discoveries allow us to understand regional tectonic processes and highlight the importance of satellite derived gravity models as one of the primary tools for the investigation of remote ocean basins

review of fossil chemosynthetic assemblages in japan abstract seventy five fossil chemosynthetic assemblages of cretaceous to holocene age have been discovered in japan many are interpreted to have been cold seep dependent and one is associated with a whale fall fossil hydrothermal vent assemblages have not been found in japan non seep assemblages of solemyids lucinids and or thyasirids are not included in this study various combinations of five diagnostic features characterize cold seep assemblages 1 the abundant and often exclusive occurrence of large invertebrate taxa suspected of harboring chemosynthetic bacteria 2 associated authigenic carbonates greatly depleted in 13c 3 a three dimensional distribution of the assemblage that is laterally restricted 4 associated pockmark or diapir related sedimentary structures and 5 the presence of conduit related tectonic or sedimentological structures such as faults slumps or debris flows excluding the whale fall assemblage we can divide cenozoic fossil chemosynthetic assemblages in japan into three types regardless of geochronologic age type i is dominated by vesicomyid bivalves and or tube worms characterized by its allochthonous or parautochthonous mode of occurrence in deep water greater than 1000 m settings along with tectonically or sedimentologically induced structures such as faults slumps diapirs or debris flows likely dependent on seepage controlled by subduction related tectonism and or on methane coming from the drastic decomposition of gas hydrate type ii is dominated by vesicomyid bivalves in most cases the species differ from those in type i and is characterized by autochthonous occurrences in muddy sediments from less than 1000 m water depth type iii is dominated by lucinoma and or conchocele and characterised by autochthonous occurrences in muddy sediments from depths of less than 300 m a living community similar to the type ii and iii assemblages has not yet been observed in the seas around japan it is noteworthy that no tectonically or sedimentologically induced structures have been observed in and around the type ii and iii fossil localities although the muddy sediments sometimes show brecciated facies that suggest an explosive effusion of methane

highly isotopically depleted isoprenoids molecular markers for ancient methane venting abstract we propose that organic compounds found in a miocene limestone from marmorito northern italy are source markers for organic matter present in ancient methane vent systems cold seeps the limestone contains high concentrations of the tail to tail linked acyclic c20 isoprenoid 2 6 11 15 tetramethylhexadecane crocetane a c25 homolog 2 6 10 15 19 pentamethylicosane pme and a distinctive glycerol ether lipid containing 3 7 11 15 tetramethylhexadecyl phytanyl moieties the chemical structures of these biomarkers indicate a common origin from archaea their extremely 13c depleted isotope compositions 13c 108 to 115 6 pdb suggest that the respective archaea have directly or indirectly introduced isotopically depleted methane derived carbon into their biomass we postulate that a second major cluster of biomarkers showing heavier isotope values 13c 88 is derived from sulfate reducing bacteria srb the observed biomarkers sustain the idea that methanogenic bacteria in a syntrophic community with srb are responsible for the anaerobic oxidation of methane in marine sediments marmorito may thus represent a conceivable ancient scenario for methane consumption performed by a defined two membered bacterial consortium 1 archaea that perform reversed methanogenesis by oxidizing methane and producing co2 and h2 and 2 srb that consume the resulting h2 furthermore the respective organic molecules are unlike other compounds tightly bound to the crystalline carbonate phase the marmorito carbonates can thus be regarded as cold seep microbialites rather than mere authigenic carbonates

post glacial microbialite formation in coral reefs of the pacific atlantic and indian oceans abstract the occurrence of microbialites in post glacial coral reefs has been interpreted to reflect an ecosystem response to environmental change the greater thickness of microbialites in reefs with a volcanic hinterland compared to thinner microbial crusts in reefs with a non volcanic hinterland led to the suggestion that fertilization of the reefal environment by chemical weathering of volcanic rocks stimulated primary productivity and microbialite formation using a molecular and isotopic approach on reef microbialites from tahiti pacific ocean it was recently shown that sulfate reducing bacteria favored the formation of microbial carbonates to test if similar mechanisms induced microbialite formation in other reefs as well the tahitian microbialites are compared with similar microbialites from coral reefs off vanuatu pacific ocean belize caribbean sea atlantic ocean and the maldives indian ocean in this study the selected study sites cover a wide range of geological settings reflecting variable input and composition of detritus the new lipid biomarker data and stable sulfur isotope results confirm that sulfate reducing bacteria played an intrinsic role in the precipitation of microbial carbonate at all study sites irrespective of the geological setting abundant biomarkers indicative of sulfate reducers include a variety of terminally branched and mid chain branched fatty acids as well as mono o alkyl glycerol ethers isotope evidence for bacterial sulfate reduction is represented by low 34s values of pyrite 43 to 42 enclosed in the microbialites and compared to seawater sulfate slightly elevated 34s and 18o values of carbonate associated sulfate 21 9 to 22 2 and 11 3 to 12 4 respectively microbialite formation took place in anoxic micro environments which presumably developed through the fertilization of the reef environment and the resultant accumulation of organic matter including bacterial extracellular polymeric substances eps coral mucus and marine snow in cavities within the coral framework tof sims analysis reveals that the dark layers of laminated microbialites are enriched in carbohydrates which are common constituents of eps and coral mucus these results support the hypothesis that bacterial degradation of eps and coral mucus within microbial mats favored carbonate precipitation because reefal microbialites formed by similar processes in very different geological settings this comparative study suggests that a volcanic hinterland is not required for microbialite growth yet detrital input derived from the weathering of volcanic rocks appears to be a natural fertilizer being conductive for the growth of microbial mats which fosters the development of particularly abundant and thick microbial crusts

methane derived authigenic carbonates formed by subduction induced pore water expulsion along the oregon washington margin authigenic magnesian calcite dolomite and aragonite are precipitated in the uppermost terrigenous sediments of the washington oregon accretionary prism by subduction induced dewatering these distinctive carbonates are methane derived and occur at sites of concentrated pore water expulsion unique biologic communities that subsist at least indirectly on methane suess et al 1985 are also found at some of these sites the methane which is dominantly biogenic is carried to the uppermost sediments of the prism by fluids and is oxidized by sulfate reducers before being incorporated into a carbonate cement carbonate precipitation occurs below the oxic layer probably no deeper than several centimetres to a few metres below the seabed cementation may be induced by three factors 1 increased carbonate alkalinity resulting from microbial sulfate reduction 2 decreased co 2 solubility resulting from a pressure decrease when the pore water escapes the prism and or 3 the addition of ca 2 and mg 2 ions from sea water near the sediment water interface the convergent margin setting engenders precipitation of authigenic carbonates in several ways compressive stresses induce anomalously rapid compaction and dewatering rates and they may cause overpressuring in migrating pore water thereby delaying precipitation of carbonates until pressure is released near the sediment water interface structural deformation of the accretionary prism creates pathways such as fault zones secondary fracture porosity and dipping permeable layers often exposed by mass movement for efficient advection and expulsion of methane enriched pore water these characteristic conditions which lead to the precipitation of methane derived carbonates may be found at other convergent margins

concretionary methane seep carbonates and associated microbial communities in black sea sediments abstract gas seeps in the euxinic northwestern black sea provide an excellent opportunity to study anaerobic methane based ecosystems with minimum interference from oxygen dependent processes an integrated approach using fluorescence and electron microscopy fluorescence in situ hybridization lipid biomarkers stable isotopes 13c and petrography revealed insight into the anatomy of concretionary methane derived carbonates currently forming within the sediment around seeps some of the carbonate concretions have been found to be surrounded by microbial mats the mats harbour colonies of sulphate reducing bacteria dss group and archaea anme 1 putative players in the anaerobic oxidation of methane isotopically depleted lipid biomarkers indicate an uptake of methane carbon into the biomass of the mat biota microbial metabolism sustains the precipitation of concretionary carbonates significantly depleted in 13c the concretions consist of rectangularly orientated rod to dumbbell shaped crystal aggregates made of fibrous high mg calcite the sulphate reducing bacteria exhibit intracellular storage inclusions and magnetosomes with greigite fe3s4 indicating that iron cycling is involved in the metabolism of the microbial population transfer of fe3 into the cells is apparently mediated by abundant extracellular vesicles resembling known bacterial siderophore vesicles marinobactine in size 20 to 100 nm and structure

strontium isotope correlation of the basal maastrichtian stage in antarctica to the european and us biostratigraphic schemes new 87 sr 86 sr dating allows the correlation of a marker horizon within the prolific late cretaceous gunnarites antarcticus faunal assemblage of the cape lamb member snow hill island formation vega island antarctica with reference sections in europe and the usa this horizon is between 81 5 and 96 5 m above the base of the g antarcticus assemblage replicate analysis of six macrofossils from within it yielded a mean value for 87 sr 86 sr of 0 707 735 9 0 000 004 3 2 s e n 17 this ratio in turn yields a numerical age of 71 0 0 2 ma when compared to the standard 87 sr s6 sr reference curve for the latest cretaceous for which the campanian maastrichtian boundary is placed at 71 3 0 5 ma the value of 0 707 735 9 0 000 004 3 correlates to a level in the belemnella lanceolata belemnite zone of the chalk of northwestern germany that is 2 5 5 m beneath the base of the overlying b pseudobtusa zone and 7 5 m above the campanian maastrichtian belemnite boundary and to an interval within the ammonite zonation of the us western interior that spans the early maastrichtian baculites baculus and b eliasi zones but with a most likely level within the b eliasi zone an earliest maastrichtian age is thereby determined for the antarctic horizon and indeed for the entire g antarcticus assemblage gunnarites sensu lato is an important ammonite marker for the base of the maastrichtian throughout the southern high latitude regions and the associated large heteromorph ammonite diplomoceras may comprise a macrofossil link back to the maastrichtian type sections

isotope sclerochronology of ammonites baculites compressus from methane seep and non seep sites in the late cretaceous western interior seaway usa implications for ammonite habitat and mode of life ammonites as well as other fauna were common in methane seeps of the late cretaceous western interior seaway wis of north america biogeochemical processes at the seeps in particular the anaerobic oxidation of methane produced a dissolved inorganic carbon reservoir with a low 13c manifested in the carbon isotope composition of the inorganic calcium carbonate concretions associated with the seeps and recorded in well preserved shells of ammonites documented at the sites detailed sclerochronological sampling of six well preserved specimens of baculites compressus collected at seep sites in the pierre shale of south dakota reveals three patterns that can be explained by reference to two specimens of the same species collected at age equivalent non seep sites three of the specimens exhibit uniformly low values of 13c that are significantly different unpaired t test p

the paleocene of antarctica dinoflagellate cyst biostratigraphy chronostratigraphy and implications for the palaeo pacific margin of gondwana abstract the paleocene 66 56 ma was a critical time interval for understanding recovery from mass extinction in high palaeolatitudes when global climate was warmer than today a unique sedimentary succession from seymour island antarctic peninsula provides key reference material from this important phase of the early cenozoic dinoflagellate cyst data from a 376 m thick stratigraphical section including the cretaceous paleogene boundary is correlated with biozones from new zealand the east tasman plateau and southeastern australia a detailed age model is suggested for the lopez de bertodano ldbf and sobral sf formations based on dinoflagellate cyst biostratigraphy and u pb dating of zircons supported by correlated magnetostratigraphy and strontium isotope values from macrofossils the top of the ldbf is confirmed as latest maastrichtian to earliest danian 66 2 65 65 ma in age the overlying sf is mostly danian in age with an inferred hiatus near the top overlain by sediments dated as late thanetian rare apectodinium homomorphum first appear in the uppermost sf the earliest in situ record from antarctica the distribution of marine and terrestrial fossils from uppermost cretaceous to eocene sediments in patagonia antarctica new zealand and australia required both sea and land connections between these fragments of gondwana fossil evidence and reconstructions of antarctic palaeogeography and palaeotopography reveal evidence for persistent embayments in the proto weddell and ross sea regions at this time we conclude that a coastal dispersal route along the palaeo pacific margin of gondwana could explain the fossil distribution without requiring a transantarctic strait or closely spaced archipelago a region in the west to east antarctic boundary zone elevated until the early paleogene perhaps acted as a site for high elevation ice caps this supports fossil geochemical and sedimentological evidence for cold climate intervals and significant sea level falls during the maastrichtian and paleocene

field relationships and stable isotope geochemistry of concretions from james ross island antarctica abstract early diagenetic precompactional concretions are abundant throughout the cretaceous tertiary marambio group larsen basin antarctica four distinct concretion types are recognised 1 spherical subspherical concretions 2 sheet concretions 3 fossil nucleated concretions and 4 concretionary burrow networks all concretion types have a micritic to microsparry variably non ferroan to ferroan calcite cement stable isotope analyses show a wide spread in both 18o and 13c 13c values are typically negative ranging between 3 38 and 39 15 o pdb usually 16 to 230 18o ranges between 1 28 and 13 81 pdb with most of the values between 5 and 10 the 13c signature is interpreted to represent carbon sourced from sulphate reduction and or methane oxidation with minor input from shell dissolution and is consistent with a shallow burial early diagenetic origin a single mudstone hosted concretion has a 18o composition indicative of precipitation of carbonate from seawater the low 18o signatures in the sandstone and siltstone hosted concretions are possibly due to early diagenetic modification of the pore water composition through volcaniclastic mineral dissolution reprecipitation reactions and perhaps through input of meteoric water concretion distribution is related to a changes in sedimentation rate and b the dominance of diffusion on concretion cementation

predation scar frequencies in chemosymbiotic bivalves at an oligocene seep deposit and their potential relation to inferred sulfide tolerances abstract three species of chemosymbiotic bivalves with different inferred sulfide tolerances and life habits from a lower oligocene seep deposit in eastern hokkaido japan were investigated for drill holes and scars of durophagous predation the thyasirid conchocele bisecta had the lowest inferred sulfide tolerance and showed the highest frequencies of repair 0 4 and drilling predation 0 1 and specimens with drill holes were on average smaller than non drilled specimens indicating that large size is a refuge from drilling predation in this species the bathymodiolin bathymodiolus inouei and the vesicomyid hubertschenckia ezoensis are inferred to have lived at higher sulfide concentrations than c bisecta based on comparisons to their living relatives and show lower repair frequencies 0 24 in b inouei and 0 17 in h ezoensis based on the assumption that increased sulfide concentrations are increasingly toxic to predators we conclude that the frequency of shell injuries in the three investigated species is inversely related to the sulfide concentrations that these species are able to tolerate thus when applied carefully the frequency of shell injuries among shelled invertebrates at fossil seeps may be used to infer their relative tolerances toward sulfide and may thus represent a tool to assess the life habits of extinct invertebrates that inhabited methane seeps in the geologic past

shallow water methane seep faunas in the cenomanian western interior seaway no evidence for onshore offshore adaptations to deep sea vents sulfi de rich environments in shallow water were considered as sites where animals acquired preadaptations enabling them to colonize deep sea hydrothermal vents and seeps or where they survived extinction events in their deep sea habitats here we document late cenomanian shallow water seep communities from the tropic shale in the western interior seaway united states as a possible refutation of these hypotheses the late cenomanian was a time of extremely warm deep water temperatures which supposedly facilitated adaptations to the deep sea and of widespread oceanic anoxia oceanic anoxic event 2 that supposedly extinguished deep water vent and seep faunas contrary to the expectations the taxa of the tropic shale seeps were not found at coeval or younger deep water seep or vent deposits furthermore a cluster analysis of faunal similarity among cretaceous vent and seep faunas revealed no distinction between pre and post cenomanian seep faunas but instead strong similarities among aptian to late cretaceous seep faunas this suggests that a low temperature gradient from shallow to deep water did not facilitate invasions of deep sea vents and seeps from shallow water and that preadaptation for living at deep sea vents and seeps did not evolve at shallow water methane seeps the vast majority of adaptations to successfully colonize deepsea vents and seeps were most likely acquired below the photic zone

astronomical calibration of the maastrichtian late cretaceous abstract recent improvements to astronomical modeling of the solar system have contributed to important refinements of the cenozoic time scale through astronomical calibration of sedimentary series we extend this astronomical calibration into the cretaceous on the base of the 405 ka orbital eccentricity variation thanks to the recovery of well preserved maastrichtian sedimentary series from odp ocean drilling program holes 1258a leg 207 equatorial atlantic 1267b leg 208 south atlantic 762c leg 122 indian ocean and dsdp deep sea drilling program hole 525a leg 74 south atlantic cyclostratigraphic analysis is performed on high resolution measurements of magnetic susceptibility on sediments cored during legs 207 and 208 and gray level variations of sediment color obtained from core photographs from legs 122 and 74 astronomical control on sedimentation is evident at every site with the presence of cycles corresponding to forcing by precession obliquity and orbital eccentricity variations identification of these cycles leads to the definition of a detailed cyclostratigraphic frame covering nearly 8 ma from the upper campanian to the cretaceous paleogene k pg boundary durations of each magnetochron from c32r 2r to c29n are inferred by cycle counting astronomical calibrations of maastrichtian sedimentary series are proposed based on the 405 ka eccentricity variation according to the most recent astronomical solution la2010a two different ages are suggested for the k pg boundary considering the uncertainty of the long term variation of the 405 ka eccentricity cycle the first proposal provides a cretaceous paleogene boundary age of 65 59 0 07 ma and the second an age of 66 0 07 ma which is coherent with the most recent radio isotopic datings magnetochron boundaries and the campanian maastrichtian boundary are dated relative to these numerical ages of the k pg boundary

occurrence of faecal pellet filled simple and composite burrows in cold seep carbonates a glimpse of a complex benthic ecosystem abstract ichnofossils preserved in marine sedimentary records provide unique information on various activities feeding dwelling excretion etc of benthic organisms here we report faecal pellet filled tubular simple and composite burrow casts from cold seep carbonate layers 16 18 mbsf deposited at least 46 58 kyr ago in the krishna godavari basin bay of bengal india deposition of these chemosynthetic clam bearing authigenic carbonate sediments with highly depleted carbon stable isotope ratios indicates methane expulsion that resulted in the development of a cold seep ecosystem although cold seep communities are extensively reported from the rock record and modern seep sites hardly any information is available on burrowing activity of the seep biota our findings open up a window for future investigation of the ecological significance of such burrows

carbon isotope δ13c differences between late cretaceous ammonites and benthic mollusks from antarctica abstract ammonites are one of the most common fossils of the mesozoic but there is little consensus on their mode of life isotopic studies have been used to reconstruct their preferred water temperature from 18 o measurements but 13 c values have more ambiguous interpretations previous studies have recorded population differences in 13 c values between ammonite and benthic organisms without explaining the cause in detail here we examine a molluscan community from seymour island antarctica and find a 4 carbon isotope offset between ammonites and other benthic mollusks the most likely cause of this anomaly is an increased metabolic carbon contribution to ammonite shell material when compared with other mollusks but we cannot rule out the possibility of a methane seep contribution increased respired co 2 production could be generated by a more active lifestyle and increased energy demands which may have increased the susceptibility of ammonites to the end cretaceous mass extinction

patterns of carbonate authigenesis at the kouilou pockmarks on the congo deep sea fan abstract different types of seep carbonates were recovered from the kouilou pockmarks on the congo deep sea fan in approximately 3100 m water depth the carbonate aggregates are represented by pyritiferous nodules crusts and slabs tubes and filled molds the latter are interpreted to represent casts of former burrows of bivalves and holothurians the nodules consisting of high mg calcite apparently formed deeper within the sediments than the predominantly aragonitic crusts and slabs nodule formation was caused by anaerobic oxidation of methane dominantly involving archaea of the phylogenetic anme 1 group whereas aragonitic crusts resulted from the activity of archaea of the anme 2 cluster evidence for this correlation is based on the distribution of specific biomarkers in the two types of carbonate aggregates showing higher hydroxyarchaeol to archaeol ratios in the crusts as opposed to nodules formation of crusts closer to the seafloor than nodules is indicated by higher carbonate contents of crusts probably reflecting higher porosities of the host sediment during carbonate formation this finding is supported by lower 18 o values of crusts agreeing with precipitation from pore waters similar in composition to seawater the aragonitic mineralogy of the crusts is also in accord with precipitation from sulfate rich pore waters similar to seawater moreover the interpretation regarding the relative depth of formation of crusts and nodules agrees with the commonly observed pattern that anme 1 archaea tend to occur deeper in the sediment than members of the anme 2 group methane represents the predominant carbon source of all carbonates 13 c values as low as 58 9 v pdb and the encrusted archaeal biomarkers 13 c values as low as 140 v pdb oxygen isotope values of some nodular carbonates ranging from 3 9 to 5 1 v pdb are too high for precipitation in equilibrium with seawater probably reflecting the destabilization of gas hydrates which are particularly abundant at the kouilou pockmarks

high benthic methane flux in low sulfate oceans evidence from carbon isotopes in late cretaceous antarctic bivalves abstract the shell material of marine benthic bivalves provides a sensitive archive of water chemistry immediately above the sediment water interface which in turn is affected by sedimentary geochemistry and redox reactions sulfate has a major controlling effect on sedimentary carbon cycling particularly the processes of methane production and oxidation with lower concentrations of sulfate likely resulting in an increase in sedimentary methane production whilst it is accepted that ocean sulfate varied markedly across the phanerozoic evidence of changes in methane production in sediments has so far been lacking there is potential for the oxidation products of sedimentary methane to be preserved and detected in marine fossils here we present the results of high resolution carbonate isotope records from two taxa of well preserved shallow infaunal bivalve lahillia and cucullaea collected from the marine shelf succession across the cretaceous paleogene k pg boundary in seymour island antarctica the succession has pre existing subtle indications of more abundant methane and the time period is characterized by much lower marine sulfate concentrations than modern these shell carbonate carbon isotope records vary widely at one extreme shells have typical average values and small ranges compatible with a contemporaneous marine dissolved inorganic carbon dic source and modern style sedimentary carbon cycling at the other the shells have large amplitude annual cycles of carbon isotopic variability of up to 23 8 within a single year of growth and shell carbonate 13 c compositions as negative as 34 shells with these increased ranges and unusually negative values are found at discrete intervals and across both bivalve taxa the contribution of methane required to explain the most negative carbonate carbon isotopic values in the bivalve shells is extremely high between 30 to 85 of bottom water dic based on mass balance calculations records of organic carbon isotopes from the same succession remained between 26 1 and 21 7 throughout suggesting that methane influence was restricted to bottom waters a lack of authigenic carbonate in the section indicates that methane oxidation progressed aerobically and may have provided a significant driver for transient bottom water de oxygenation where methane addition is indicated the seasonal sensitivity precludes control by methane hydrates we argue that these data represent the increased importance and sensitivity of methanogenesis in the sediments enabled by lower ocean sulfate concentrations during the late cretaceous the tendency towards a more dynamic role for marine methane production and oxidation is likely to apply to other times of low marine sulfate in earth s history

extinction patterns δ18 o trends and magnetostratigraphy from a southern high latitude cretaceous paleogene section links with deccan volcanism although abundant evidence now exists for a massive bolide impact coincident with the cretaceous paleogene k pg mass extinction event 65 5 ma the relative importance of this impact as an extinction mechanism is still the subject of debate on seymour island antarctic peninsula the lopez de bertodano formation yields one of the most expanded k pg boundary sections known using a new chronology from magnetostratigraphy and isotopic data from carbonate secreting macrofauna we present a high resolution high latitude paleotemperature record spanning this time interval we find two prominent warming events synchronous with the three main phases of deccan traps flood volcanism and the onset of the second is contemporaneous with a local extinction that pre dates the bolide impact what has been termed the k pg extinction is potentially the sum of multiple independent events at least at high latitudes

significance of aragonite cements around cretaceous marine methane seeps abstract detailed petrography and geochemistry of carbonate precipitates in cretaceous cold seep mounds from the canadian arctic show spectacular early diagenetic products some still preserved splays and isopachous layers of fine acicular aragonite and large botryoids and crusts of low magnesium calcite showing unusual entanglement of former fibrous calcite and aragonite the latter mineralogy is suggested by clear flat terminated cathodoluminescence patterns interpreted as ancient crystal growth steps and the former by rhombohedral terminations the early cement phases very likely precipitated in cold arctic water dominated by bicarbonates derived from bacterially oxidized methane these cements have d13c values around 44 and d18o values of 1 8 to 0 1 pdb coexistence of calcite and aragonite early cements in the cretaceous seep mounds is unusual because precipitation occurred in high latitude cold water settings and during a so called calcite sea mode as in modern marine hydrocarbon seeps the chemistry of the cretaceous system was apparently controlled by chemosynthetic bacterial activity resulting in high ahco3 that promoted precipitation of carbonates we suggest that locally fluctuations in ahco3 aso42 resulted in oscillating aragonite or calcite supersaturation and hence controlled the mineralogy of the early precipitates

late cretaceous winter sea ice in antarctica the late cretaceous is considered to have been a time of greenhouse climates although evidence from maastrichtian sediments for rapid and significant sea level changes suggests that ice sheets were growing and decaying on antarctica at that time there is no direct geological evidence for glaciation but we present palynomorph records from seymour island antarctica that may suggest maastrichtian sea ice the dinoflagellate cyst impletosphaeridium clavus is dominant we propose that its profusion may signify the accumulation of resting cysts from dinoflagellate blooms related to winter sea ice decay prior to the cretaceous paleogene transition i clavus decreased dramatically in abundance we link this with climate warming terrestrial conditions inferred from pollen and spore data are consistent with our climate interpretations based on i clavus together with 18 o values from macrofossils these data and our interpretation support the presence of ephemeral ice sheets on antarctica during the latest cretaceous highlighting the extreme sensitivity of this region to global climate change

initial characterization of cold seep faunal communities on the new zealand hikurangi margin abstract cold seep communities have been known from the north atlantic and north pacific for more than 20 years but are only now being explored in the southern hemisphere while fisheries bycatch had suggested the presence of cold seeps on the new zealand margin the biodiversity and distribution of these communities remained unknown explorations using towed cameras and direct sampling gear revealed that cold seep sites are abundant along the new zealand hikurangi margin initial characterization of the faunal communities at 8 of these sites indicates a fauna that is associated with particular sub habitats but which varies in abundance between sites community composition is typical at higher taxonomic levels of cold seep communities in other regions the dominant symbiont bearing taxa include siboglinid tube worms vesicomyid clams and bathymodiolin mussels at the species level much of the seep associated fauna identified so far appears either to be new to science or endemic to new zealand seeps suggesting the region may represent a new biogeographic province for cold seep fauna some overlap at the species and genus level is also indicated between the sampled seep communities and the fauna of hydrothermal vents on the kermadec arc in the region further taxonomic and genetic identifications of fauna from this study will allow us to fully test the levels of species overlap with other new zealand chemosynthetic ecosystems as well as with other cold seep sites worldwide these apparently novel communities exhibit evidence of disturbance from a deep bottom trawl fishery and appear to be threatened along the entire new zealand margin as bottom fisheries mining and fossil fuel exploitation move into deeper waters seep communities may be endangered worldwide necessitating the initiation of conservation efforts even as new seep ecosystems are discovered and explored our findings highlight the unique nature of anthropogenic impacts in the deep sea in which reservoirs of biodiversity can be impacted long before they are even known

control of hazard due to seismicity induced by a hot fractured rock geothermal project in 2003 hydraulic stimulations were carried out in a geothermal field in eastern el salvador central america as part of a project to explore the feasibility of commercial hot fractured rock energy generation a key requisite for this environmentally friendly energy source is that the fracturing of the hot rocks at depths of 1 2 km must not produce levels of ground shaking at the surface that would present a serious disturbance or threat to the local population thresholds of tolerable ground motion were inferred from guidelines and regulations on tolerable levels of vibration and from correlations between instrumental strong motion parameters and intensity considering the vulnerability of the exposed housing stock the thresholds were defined in terms of peak ground velocity pgv and incorporated into a traffic light system that also took account of the frequency of occurrence of the induced earthquakes the system was implemented through a dedicated seismograph array and locally derived predictive equations for pgv the traffic light was used as a decision making tool regarding the duration and intensity of pumping levels during the hydraulic stimulations the system was supplemented by a small number of accelerographs and re calibrated using records obtained during the rock fracturing

paleocene methane seep and wood fall marine environments from spitsbergen svalbard abstract here we describe a paleocene aged methane seep locality and an associated layer of sunken wood from fossildalen on spitsbergen svalbard hosted in offshore to prodelta siltstones of the basilika formation van mijenfjorden group the fossiliferous seep carbonates were first identified in museum collections from expeditions in the 1920s and 1970s and subsequently sampled as ex situ blocks in the field in 2015 the isotopically light composition 13c values approaching 50 v pdb and characteristic petrographic textures of the carbonates combined with the isotopically light archaeal lipids are consistent with their formation at fossil hydrocarbon seep environment the invertebrate fauna within the carbonates is of moderate diversity 17 species and has a shallow water affinity wood specimens within the carbonates contain the borings and shells of wood boring bivalves the seep fauna is dominated by a species of the thyasirid genus conchocele common to other seeps of similar age the data shed new light onto the history of methane seepage on svalbard and the evolution and ecology of seep and wood fall faunas during the latest cretaceous earliest paleogene time interval

diffusive methane seepage in ancient deposits examples from the neogene shin etsu sedimentary basin central japan abstract along continental margins various types of methane seeps with a variety of flux rates spatial extents and durations occur although numerous studies have investigated spatially extensive high flux rate seeps seeps with ephemeral and or weak flows known as diffusive seeps have received less attention this study investigates ancient diffusive methane seeps in the shin etsu sedimentary basin central japan aiming to deduce their spatial extent and their sedimentological paleontological and geochemical properties the seeps were identified as centimeter scale carbonate concretions in two outcrops of neogene siltstones in the basin a comprehensive examination of the spatial distribution of the carbonates their associated molluscan fossils petrography carbon and oxygen isotopic compositions and lipid biomarker contents of the concretions revealed that they originated from the anaerobic oxidation of methane aom and formed via a weak diffusive fluid flow the small size and irregular or burrow shaped morphologies of the concretions indicate that methane bearing fluids diffused through small pore spaces such as burrows associated molluscan fossils consist of vesicomyids and other bivalves typical of methane seeps fossils of predator species were also identified but epifaunal seep organisms are notably absent the carbonate concretions are composed of strongly 13c depleted micrite 13c values as low as 46 0 vs vpdb with minor 13c rich void filling sparry cements the presence of lipid biomarkers pentamethylicosane pmi with 13c values as low as 119 and biphytane and the absence of crocetane suggests that the aom was performed by an anme 1 dominated archaeal community the insights of diffusive methane seepage in the geological record gained from this study can help to better understand depositional processes of seep deposits and variations in fluid flows in both ancient and modern methane seeping systems

fatty acids in sparry calcite fracture fills and microsparite cement of septarian diagenetic concretions sparry calcite fracture fills and concretion body cements in concretions from the flodigarry shale member of the staffin shale formation isle of skye scotland entrap and preserve mineral and organic materials of sedimentary and diagenetic origin fatty acids are a major component of the lipids recovered by decarbonation and comprise mainly n alkanoic and dicarboxylic acids two generations of fracture fill calcite early brown and later yellow and the concretion body microspar yield significantly different fatty acid profiles early brown calcites yield mainly medium chain n alkanoic acids with strong even predominance later yellow calcites are dominated by dicarboxylic acids with no even predominance both fracture fills lack the long chain n alkanoic and dicarboxylic acids additionally recovered from the concretion bodies the absence of longer chain acids in the calcite spar fracture fills is inferred to result from the transport of fatty acids by septarian mineralising fluids whereby low aqueous solubility of longer chain acids or their salts accounts for their relative immobility comparative experiments have been carried out using conventional solvent extraction on the concretion body and associated shales both decarbonated and untreated extracted lipid yields are higher but the fatty acids probably derive from mixed locations in the rock including both kerogen and carbonate associated lipid pools only experiments involving decarbonation yielded dicarboxylic acids in molecular distributions probably controlled mainly by fluid transport alkane biomarker ratios indicate very low thermal maturity has been experienced by the concretions and their host sediments septarian cracks lined by brown calcite formed during early burial microbial co2 from sulphate reducing bacteria was probably the main source of mineralising carbonate emplacement of the later septarian fills probably involved at least one episode of fluid invasion

permeability creation and damage due to massive fluid injections into granite at 3 5 km at soultz 2 critical stress and fracture strength 1 the stress acting on fractures in a 3 5 km deep borehole in granite is examined to place constraints on fracture strength and to evaluate whether permeable fractures tended to be critically stressed two data sets consisting of some 500 fractures are analyzed the first considers the permeable impermeable fracture populations in their natural state the second considers the populations after the hole had been subject to a prolonged 9 mpa overpressure in two major injections which increased the number of permeable fractures from 18 to more than 95 for both data sets it is found that permeable fractures are critically stressed inasmuch as they support levels of shear stress that would be verging on failure if their strength were governed by a coulomb friction law with a coefficient of 0 6 1 0 however the vast majority of impermeable fractures are also critically stressed implying that critical stressing is a necessary but not a sufficient condition for permeability to develop most permeable fractures showed evidence of shear failure after the injections and tended to occur in hydrothermally altered cataclastic shear zones suggesting that they may have been relatively weak because of the presence of illite to prevent failure of the impermeable fractures during the injections requires a cohesion of at least 6 5 mpa to augment a maximum allowable friction coefficient of 1 0 these are probably early mode 1 fractures that are sealed primarily with calcite the strength of the shear zones appears to be significantly greater than the illite rich fractures from which they are composed this imposes constraints on their internal architecture

hydraulic fracturing in a sedimentary geothermal reservoir results and implications field experiments in a geothermal research well were conducted to enhance the inflow performance of a clastic sedimentary reservoir section due to depths exceeding 4050 m bottom hole temperatures exceeding 140 c and open hole section dual zone technically demanding and somewhat unprecedented conditions had to be managed the fracturing operations were successful fractures were created in two isolated borehole intervals and the inflow behaviour of the reservoir was decisively enhanced the effective pressures applied for fracture initiation and propagation were only slightly above in situ pore pressures nevertheless the stimulation ratio predicted by fracture performance modelling could not be achieved multiple reasons could be identified that account for the mismatch an insufficient fracture tie back as well as chemical and mechanical processes during closure led to reduced fracture conductivities and therefore diminished productivity the insights gained are the basis for further fracture design concepts at the given and geologic comparable sites

strontium isotope profiles across k t boundary sequences in denmark and antarctica strontium isotope profiles derived from minimally altered samples across marine k t boundary sequences exposed at kjolby gaard and nye klov denmark and on seymour island antarctica show neither the boundary excursions nor the boundary spikes in 87sr 86sr that have been reported for k t boundary sequences from elsewhere nor do our data conform to modelled predictions of the sr isotopic response of the oceans to a positive spike in 87sr 86sr at the terminal cretaceous boundary values for 87sr 86sr with 95 confidence intervals are 0 707828 3 in denmark and 0 707832 7 in antarctica our data suggest that 87sr 86sr stopped increasing and started decreasing at least 90 ka before the k t boundary

burial diagenesis and pore fluid evolution in a mesozoic back arc basin the marambio group vega island antarctica upper cretaceous shallow marine sediments from vega island antarctica contain five major authigenic phases glauconite pyrite a zeolite mineral of the clinoptilolite heulandite group chlorite and calcite the framework sediment composition changes from quartzose at the base of the measured succession to volcaniclastic at the top the petrogenesis of individual samples reflects the local controls on diagenesis of depositional environment and sediment composition combined with the effects of burial to no more than 1 km calcite cements are the most abundant precipitates marine carbonate cements include acicular and other fringing cements that commonly are present within bioclasts early burial micritic to sparry calcite cements include both concretionary and nonconcretionary forms burial calcites occlude residual porosity replace detrital grains and form veins with fibrous and cone in cone textures the stable isotope composition of the carbonate cements is very variable with delta 18 o ranging from 0 60 per thousand to 19 93 per thousand pdb and delta 13 c of 1 33 per thousand to 28 09 per thousand pdb the stable isotope data reflect the initial conditions of mineral precipitation in oxic and anoxic marine pore waters together with the effects of subsequent fluid rock interaction through both recrystallization and cementation the latest precipitates thought to have been formed during over pressuring define a vertical field for burial calcite on an isotope cross plot suggesting that late fluids responsible for cementation and alteration of earlier precipitates had negative delta 18 o and contained carbon with variable delta 13 c the oxygen values are compatible with either influx of high latitude meteoric water or intense fluid rock interaction with reactive volcanic detritus or a combination of the two processes the very variable carbon signatures probably reflect dissolution of bioclasts and earlier diagenetic precipitates only by identifying possible end member compositions for both early and late diagenetic precipitates can most of the isotopic data be interpreted correctly

fossil clams from a serpentinite hosted sedimented vent field near the active smoker complex rainbow mar 36 13 n insight into the biogeography of vent fauna hydrothermal circulation at ultramafic hosted sites supports a large variety of high and low temperature hydrothermal vents and associated ecosystems the discovery of abundant fossil vesicomyid and thyasirid shell accumulations at the ridge crest approximately 2 5 km east of the active rainbow vent field on the mid atlantic ridge mar 36 degrees 13 n increased our knowledge regarding the diversity of vent communities at slow spreading ridges bivalve molluscs of the family vesicomyidae were represented by the genus phreagena here we present the first record of this genus in the atlantic ocean this second vesicomyid species known from the mar phreagena sp was found to be associated with a thyasira species that is affiliated with t southwardae at the logatchev vent field on the mar and with t vulcolutre in the gulf of cadiz these two clams have close relationships with seep taxa along the continental margin and were likely associated with sedimented vent fields delta o 18 and delta c 13 analyses of the shells suggested that the burrowing bivalve thyasira could incorporate isotopically light carbon derived from the oxidation of methane in the sediment while the signature of phreagena sp shells denoted a different carbonate source c 14 dating of the shells denoted that the hydrothermal activity in the rainbow area began at least similar to 25 5 kyr bp which is similar to the model of the hydrothermal vent field distribution that was proposed for the logatchev hydrothermal site the results provide new insight regarding the diversity of chemosynthetic fauna on the mar over geologic time ultramafic hosted on axis sedimented vent fields extend the range of habitats for chemosynthetic communities underlying the need to further explore the geology of these types of environments on slow spreading ridges and to determine their role in the ecology of deep sea vent communities

a new lower cretaceous hydrocarbon seep locality from the czech carpathians and its fauna abstract a new lower cretaceous hydrocarbon seep locality at baska in the czech carpathians is described the seep carbonate and associated mollusk fauna have been encountered in deep water claystones and siltstones of the upper barremian upper part of the hradist formation associated with pillow lavas of so called teschenite association the investigated carbonate displays petrographic characters typical of seep sediments clotted micrite isopachous rim cements and layered pyrite aggregations the carbon isotopic composition 20 0 to 23 5 vs v pdb most likely indicates anaerobic oxidation of thermogenic methane the fossils recovered from this locality are rather poorly preserved but hokkaidoconchid gastropods and lucinid bivalves in association with trochid and zygopleurid gastropods are identified this finding confirms the existence of seep faunas in the western carpathians which was anticipated based on the presence of seep mollusks and brachiopods in old monographs that cover lower cretaceous fossils of this region the fossils illustrated in the monograph of ascher 1906 are here briefly re evaluated and possible seep members are indicated

seismic imaging of the transitional crust across the northeastern margin of the south china sea abstract crustal structure across the passive continental margin of the northeastern south china sea scs is presented based on a deep seismic survey cooperated between taiwan and china in august 2001 reflection data collected from a 48 hydrophone streamer and the vertical component of refraction reflection data recorded at 11 ocean bottom seismometers along a nw se profile are integrated to image the upper 1 6 2 4 km s lower 2 5 2 9 km s and compacted 3 4 5 km s sediment the upper 4 5 5 5 km s middle 5 5 6 5 km s and lower 6 5 7 5 km s crystalline crust successively the velocity model shows that the thickness 0 5 3 km and the basement of the compacted sediment are strongly varied due to intrusion of the magma and igneous rocks after seafloor spreading of the scs furthermore several volcanoes and igneous rocks in the upper middle crust 7 10 km thick and a high velocity layer 0 5 km thick in the lower crust of the model are identified as the ocean continent transition oct below the lower slope in the northeastern margin of the scs a thin continent nw of the oct and a thick oceanic crust se of the oct in the continental margin of the northeastern scs are also imaged but these transitional crusts cannot be classified as the oct due to their crustal thickness and the limited amount of the volcano the magma and the high velocity layer the extended continent next to the gravity low and a sag zone extended from the sw taiwan basin may have resulted from subduction of the eurasian plate beneath the manila trench whereas the thick oceanic crust may have been due to the excess volcanism and the late magmatic underplating in the oceanic crust after seafloor spreading of the scs

miocene shallow marine cold seep carbonate in fold and thrust western foothills sw taiwan a mound shaped authigenic carbonate buildup 50 m wide and 5 m high occurred in the middle part of the late miocene shallow marine succession the hunghuatzu formation exposed along the nantzuhsien river sw taiwan the carbonate concretions are classified into four types based on morphology which appeared to develop in upward sequence with vague boundaries 1 flat pipe shaped nodules highly dolomitic small pipes or nodules subparallel to the host strata 2 bulb shaped nodules discrete or combined small mesoclots with subspherical to irregular shapes 3 mushroom shaped concretions large mushroom like or irregular shaped blocks with chimney or vent structures and 4 carbonated layers with sedimentary structures these concretions are mainly composed of dolomite micrites quartz feldspar muscovite and clay minerals ubiquitously interweaved with blackish brown colored low magnesium calcite lmc veins low delta c 13 vpdb values 51 8 parts per thousand to 29 8 parts per thousand of all types of the carbonates reveal that the carbonates were mainly derived from anaerobic oxidation of hydrocarbons many samples are also o 18 depleted delta o 18 vpdb 11 5 parts per thousand to 1 00 parts per thousand due to the mixture with isotopically light lmc veins likely precipitated from meteoric waters there are numerous chemosymbiotic bivalve fossils genus monitilora diameter 3 4 cm in growth position just above the carbonate buildup according to the geological and isotopic signatures the hunghuatzu carbonates are related to a cold seep pseudobioherm which formed in a very shallow marine environment like tidal flat in a passive margin setting exposures of the hunghuatzu pseudobioherm may provide clues for tracking and comparing the evolution history of gas reservoir systems and hints of active tectonics of the sw taiwan region c 2012 elsevier ltd all rights reserved

seismic stratigraphy and tectonic structure from a composite multi channel seismic profile across the entire dangerous grounds south china sea abstract we interpret a more than 500 km long composite multi channel seismic reflection profile across the entire dangerous grounds the south china sea five tectonostratigraphic units are determined together with seven sequence boundaries detailed analysis of extensional features based on measurements of fault heaves revealed two major phases of extension separated by a distinct unconformity which likely correspond with the beginning of sea floor spreading in the south china sea early extension occurred during continental rifting late cretaceous early oligocene and resulted in formation of half grabens and rotated blocks controlled by a deeply rooted detachment system extension continued in our study area during the drifting phase of the east subbasin of the south china sea late oligocene early miocene until the subsequent opening of the southwest subbasin at about 25 ma but its intensity decreased markedly thereafter deeply rooted detachment systems evolved possibly during this second phase of extension at the continent ocean transition area from a coincidence of the lowermost reflections and moho depth as derived from gravity inversion we tentatively interpret the flattened part of this detachment system as the crust mantle boundary it is suggested that the dangerous grounds reflect a magma poor rift system at the initial stage of mantle unroofing we suggest that a widespread carbonate platform developed across the dangerous grounds concurrent with the period of seafloor spreading in the southwest subbasin of the south china sea fault related stretching factors f along the line show discrepancies with the whole crustal stretching factors c the continental crust of the dangerous grounds may have experienced nonuniform thinning

tectonic controls on the genesis and distribution of late cretaceous western interior basin hydrocarbon seep mounds tepee buttes of north america abstract within the western interior basin of north america hundreds of small carbonate mounds associated with late cretaceous hydrocarbon emissions or seeps form the most extensively distributed occurrence of fossil seep mounds that is known the tepee buttes analysis of the stratigraphic literature for the basin reveals that tepee butte formation occurred intermittently over a 10 m yr period within a narrowly restricted paleogeographic region the modern geographic distribution of the tepee buttes is constrained roughly to between 101 30 documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empt

an integrated geophysical study on the mesozoic strata distribution and hydrocarbon potential in the south china sea abstract a series of drilling dredge and seismic investigations indicate that mesozoic sediments exist in the south china sea scs which shows a bright prospect for oil and gas exploration in order to study the distribution of mesozoic strata and their residual thicknesses in the scs we carried out an integrated geophysical study based mainly on gravity data gravity basement depth and distribution of residual mesozoic thickness in the scs were obtained using gravity inversion constrained with high precision drilling and seismic data in addition the fine deep crustal structures and distribution characteristics of mesozoic thicknesses of three typical profiles were obtained by gravity fitting inversion mesozoic strata in the scs are mainly distributed in the south and north continental margins and have been reformed by the later tectonic activities they extend in ne trending stripes are macro controlled by the deep and large ne trending faults and cut by the nw trending faults which were active in later times the offset in nw direction of mesozoic strata in nansha area of the southern margin are more obvious as compared to the north margin in the pearl river mouth basin and southwest taiwan basin of the north continental margin the mesozoic sediments are continuously distributed with a relatively large thickness in the nansha area of the south margin the mesozoic strata are discontinuous and their thicknesses vary considerably according to the characteristics of mesozoic thickness distribution and hydrocarbon potential analyses from drilling and other data dongsha uplift chaoshan depression southwest taiwan basin peikang uplift and liyue bank have large thickness of the mesozoic residual strata have good hydrocarbon genesis capability and complete source reservoir cap combinations show a bright prospect of mesozoic oil gas resources

evidence for a petroleum subsystem in the frontier formation of the uinta piceance basin petroleum province anomalous carbonate horizons with intercrystalline hydrocarbon residue cone in cone structures and calcite beef veins in adjacent sandstone beds record potential evidence for hydrocarbon generation and seepage in the middle to upper turonian frontier formation from the uinta basin utah and colorado eight carbonate occurrences all encountered within distal delta front facies thin bedded sandstones and siltstones were sampled at outcrop locations from the southern and eastern margins of dinosaur national monument seven petrographic facies pf1 pf7 were identified using standard petrographic and cathodoluminescence microscopy pf1 large and small botryoids and fans pf2 yellow brown spherules pf3 microcrystalline spar cement pf4 blocky spar pf5 prismatic spar pf6 drusy mosaic spar and pf7 dolomite facies pf1 pf3 are synsedimentary phases comprising a large percentage of carbonate horizon volume whereas pf4 pf7 are late stage fabrics the 13c values of pf1 pf3 9 9 to 20 0 are consistent with contributions from biogenic methane seepage during deposition and early diagenesis brecciated pf1 fabrics and blowout depressions within sandstone horizons further indicate significant methane generation during deposition and early burial late stage fabrics contain 13c 8 0 to 17 3 and 18o 6 5 to 13 5 values consistent with progressive burial during which intercrystalline hydrocarbon residue cone in cone structures and calcite beef veins were formed by the thermal maturation of organic matter from enclosing distal delta front facies together these features reveal the potential for the thin bedded facies of the frontier formation distal delta front to serve as a potentially viable petroleum subsystem previously unrecognized in the uinta piceance petroleum province

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

late cretaceous maastrichtian shallow water hydrocarbon seeps from snow hill and seymour islands james ross basin antarctica fossil hydrocarbon seeps are present in latest cretaceous maastrichtian volcaniclastic shallow shelf sediments exposed on snow hill and seymour islands james ross basin antarctica the seeps occur in the snow hill island formation on snow hill island and are manifest as large sized cement rich carbonate bodies containing abundant thyasirid bivalves and rarer ammonites and solemyid bivalves these bodies have typical seep cement phases with 13c values between 20 4 and 10 7 and contain molecular fossils indicative of terrigenous organic material and the micro organisms involved in the anaerobic oxidation of methane including methanotrophic archaea and sulphate reducing bacteria on seymour island the seeps occur as micrite cemented burrow systems in the lopez de bertodano formation and are associated with thyasirid solemyid and lucinid bivalves and background molluscan taxa the cemented burrows also have typical seep cement phases with 13c values between 58 0 and 24 6 there is evidence from other data that hydrocarbon seepage was a common feature in the james ross basin throughout the maastrichtian and into the eocene the snow hill and seymour island examples comprise the third known area of maastrichtian hydrocarbon seepage but compared to most other ancient and modern seep communities the james ross basin seep fauna is of very low diversity being dominated by infaunal bivalves all of which probably had thiotrophic chemosymbionts but which were unlikely to have been seep obligates absent from the james ross basin seep fauna are typical obligate seep taxa from the cretaceous and the cenozoic reasons for this may have been temporal palaeolatitudinal palaeobathymetric or palaeoecological

13c depleted biphytanic diacids as tracers of past anaerobic oxidation of methane abstract 13 c depleted biphytanic diacids containing 0 2 pentacyclic rings are abundant biomarkers in cenozoic methane seep limestones the strong 13 c depletion 132 to 96 suggests that they derive from euryarchaea metabolizing methane they occur with other biomarkers typically associated with anaerobic oxidation of methane such as crocetane pentamethylicosane pmi archaeol hydroxyarchaeol and glycerol dibiphytanyl glycerol tetraethers gdgts in contrast to gdgt derived biphytane hydrocarbons the biphytanic diacids appear to be almost exclusively derived from methanotrophic euryarchaea

on the potential generality of depth related ecologic structure in cold seep communities evidence from cenozoic and mesozoic examples faunal communities inhabiting hydrocarbon seeps in the deep sea today show a depth related change in their ecologic structure the proportion of obligate endemic taxa increases with depth while the abundance of predators and other background taxa decreases here the fossil record of seep communities is investigated for similar gradients the middle eocene to middle miocene deep water cold seep deposits in western washington state usa are from different depths those of the middle to late eocene humptulips bear river and whiskey creek sites lived in depths of 500 to 2000 m those of the late oligocene to middle miocene seep communities of the lincoln creek and astoria formations in depths of 16 to 900 m these seeps were inhabited by the same taxa that inhabit cold seeps today and like their modern analogs they show an increasing proportion of obligate taxa and a decreasing abundance of predators and other background taxa with depth also among late mesozoic seep sites a depth related change in the proportion of obligate taxa is apparent seep communities in shallow shelf settings harbor virtually no obligates while seep communities in outer shelf to slope settings show a high proportion of obligates although the constituting species have different taxonomic affinities than their cenozoic and extant counterparts unlike in modern examples differences between seep communities from outer shelf and slope depths were not seen it is hypothesized that due to the higher mesozoic sea levels many seep communities on the continental shelves were located below the photic zone where an obligate seep fauna could develop because an increase in the proportion of obligate taxa with depth can be seen both in the cenozoic and in the late mesozoic despite the different taxonomic affinities of the obligate taxa it is suggested here that this depth related structure is a general feature of seep faunas independent of the taxa that express this pattern

outcrop analogues of pockmarks and associated methane seep carbonates a case study from the lower cretaceous albian of the basque cantabrian basin western pyrenees abstract late albian deep water sediments of the black flysch group in the basque cantabrian basin western pyrenees preserve a fossil pockmark field including methane seep carbonates and associated macrofauna the geometry of the pockmarks is reconstructed from repeated lens shaped turbidite deposits with centrally located carbonate bodies early diagenetic carbonate phases such as clotted micrite and yellow calcite with 13c values as low as 41 6 and hydrocarbon biomarkers e g 2 6 10 15 19 pentamethylicosane with strong depletions in 13c indicate that the carbonates precipitated due to anaerobic oxidation of methane the pockmarks probably formed due to subsidence induced by dewatering and degassing of the gas charged seabed perhaps enhanced by the weight of the carbonate bodies the macrofauna resembles that of other late mesozoic deep water methane seeps world wide and is dominated by large lucinid and caspiconcha bivalves and hokkaidoconchid gastropods during late diagenesis the carbonate 18o values were reset to a narrow range of 12 to 10 the remaining pore spaces and fissures were filled with pyrobitumen and additional carbonate phases precipitated potentially due to thermochemical sulfate reduction processes

lipid biomarker patterns of methane seep microbialites from the mesozoic convergent margin of california abstract in order to reconstruct biogeochemical pathways at mesozoic methane seeps a set of late jurassic tithonian to early cretaceous aptian albian 13 c depleted seep limestones from forearc strata in western california were subjected to detailed molecular isotopic biomarker analyses two of the microbial carbonate deposits are turbidite hosted fault related whereas one is hosted in serpentinite in a diapir related setting the limestones contain 13 c depleted archaeal lipid biomarkers such as crocetane 13 c 80 and pmi 100 indicative of an involvement of anaerobic oxidation of methane aom in carbonate precipitation isotopically depleted crocetane in the tithonian sample represents the oldest reported occurrence of this compound at methane seeps in the set of samples a series of strongly 13 c depleted regular c 21 to c 24 isoprenoids possibly results from diagenetic alteration of archaeal sesterterpanylglycerol diethers as suggested by the presence of the putative intermediate 3 7 11 15 19 pentamethylicosanoic acid 13 c depleted 17 h 21 h and 17 h 21 h hopanes c 30 c 34 with 22 s and 22 r isomer couplets c 31 are present in all samples in distributions indicative of a moderate thermal maturity low 13 c values 78 to 60 suggest that these are derived from anaerobic bacteria involved in aom notably 22 s isomers are consistently enriched in 13 c relative to their 22 r counterparts our samples represent 70 myr of seepage activity and aom along the mesozoic margin of western california filling the gap between the currently oldest methane seep biomarker record from the oxfordian late jurassic and the more widely recognised cenozoic examples

soil forensics as a tool to test reported artefact find sites the reported find sites for archaeological artefacts such as coin hoards can in some cases be either accidently mistaken or potentially deliberately fabricated however testing the veracity of such reported find sites can be difficult advances in the analysis of soil samples for both criminal and environmental forensic investigations is allowing the characterisation of very small soil samples to be achieved in this study forty three soil samples were analysed from six groups of coins each of which had been reported as an individual coin hoard collected at different locations in devon and somerset uk in situ soils were removed from the surface of the coins and mineralogically analysed using automated scanning electron microscopy and energy dispersive analysis the mineralogical data show that five of these six coin groups could not have been derived from individual find sites the mineralogical data for one of the groups was indicative that the coins making up that group could potentially have been derived from a single location subsequent and independent to the mineralogical assessment of the coins a numismatic inspection of the coins led to the same conclusions automated mineral analysis which can be carried out on very small soil samples may prove to be a useful technique for the assessment of the reported provenance of archaeological artefacts

a comprehensive approach to the study of methane seep deposits from the lincoln creek formation western washington state usa a comprehensive approach using palaeontology petrography stable isotope geochemistry and biomarker analyses was applied to the study of seven small methane seep carbonate deposits these deposits are in the oligocene part of the lincoln creek formation exposed along the canyon and satsop rivers in western washington each deposit preserves invertebrate fossils many representing typical seep biota authigenic carbonates with 1 3 c values as low as 51 pdb reveal that the carbon is predominately methane derived carbonates contain the irregular isoprenoid hydrocarbons 2 6 11 15 tetramethylhexadecane crocetane and 2 6 10 15 19 pentamethylicosane pmi lipid biomarkers diagnostic for archaea these lipids are strongly depleted in 1 3 c 1 3 c values as low as 120 pdb indicating that archaea were involved in the anaerobic oxidation of methane small filaments preserved in the carbonate may represent methanotrophic archaea archaeal methanogenesis induced the formation of a late diagenetic phase brownish calcite consisting of dumbbell shaped crystal aggregates that exhibit 1 3 c values as high as 7 pdb clotted microfabrics of primary origin point to microbial mediation of carbonate precipitation downward directed carbonate aggregation in the seeps produced inverted stromatactoid cavities large filaments interpreted as green algae based on their size shape arrangement and biomarkers imply that deposition occurred in places in water no deeper than 210 m

cretaceous methane seep deposits from new zealand and their fauna abstract six cretaceous methane seep deposits are reported from the raukumara peninsula eastern north island new zealand dinoflagellate dating indicates a late albian to mid cenomanian age for three deposits from port awanui and a mid campanian age for two deposits from waipiro bay and for one from owhena stream the dominant petrographic fabric of the carbonates is detrital micrite and the numerous fenestrae and vugs are filled with various cements including two types of non detrital micrite and botryoidal and banded fibrous calcites these petrographic features in combination with negative 13c values of early diagenetic micrites as low as 29 2 vs v pdb and 13c depleted molecular fossils such as the archaeal biomarkers pentamethylicosane 97 vs v pdb and biphytane 99 and the bacterial biomarker anteiso c15 fatty acid 47 reveal that sulfate dependent anaerobic oxidation of methane aom induced the formation of these deposits the carbonates preserve a typical mollusk dominated late mesozoic deep water seep fauna including the large modiomorphid bivalve caspiconcha the lucinid bivalve ezolucina and limpets hokkaidoconchids and a large abyssochrysoid among the gastropods with close biogeographic relationships to north pacific seep faunas of cretaceous age in contrast to the general marine mollusk fauna of new zealand which shows a high degree of endemism in both the cenozoic and recent new zealand s cretaceous to present day seep faunas consist largely of taxa known from coeval seeps around the world thus while deep water seeps in new zealand were repeatedly or continuously colonized by members of the global seep fauna the general mollusk fauna of the new zealand region developed a considerable degree of endemism during this time

far field poroelastic response of geothermal reservoirs to hydraulic stimulation treatment theory and application at the gros schonebeck geothermal research facility abstract enhanced geothermal systems egs are engineered reservoirs developed to extract heat from low permeability and low porosity geological formations cyclic hydraulic stimulation treatments can be used in some cases to create hydraulic fractures and gain access to the target formation fluids drain the geothermal fluid and increase the overall productivity of the reservoir during these operations successive cycles of injection at high flow rates are conducted to decrease the effective minimum principal stress to the tensile strength of the material developing a mode i fracture opening of the newly developed fractures induces additional deformation of the reservoir rocks whose impact on the far field reservoir hydraulics has not been addressed so far for real case applications these rates of compressive deformation can be significantly high in the context of cyclic stimulation treatments and can lead to a poroelastic pore pressure increase which spans quasi instantaneously at greater distances than diffusive processes in this study such a poroelastic response resulting from cyclic deformation during hydraulic stimulation treatment of a well is investigated using hydromechanical coupling between pore pressure variations and rock deformation the effects of this poroelastic response on the hydromechanical state of a reservoir is illustrated with field measurements of a cyclic hydraulic stimulation treatment conducted at the gros schonebeck geothermal research site in august 2007 this study demonstrates that the pore pressure increase monitored in a neighbor well located approximately 475 m away from the stimulated well at reservoir depth is controlled by diffusive processes responsible for the long term increase of pore pressure but also by poroelastic effects responsible for the quasi instantaneous local peaks in pore pressure the results from this applied study helped to quantify the relevance of the poroelastic behavior of stimulated reservoir rocks in a way than can improve current understanding of such hydraulic stimulation settings

characterisation of a fractured reservoir using microearthquakes induced by hydraulic injections abstract microseismic activity is induced by a number of engineering activities which involve fluid injection or extraction in naturally fractured rock masses evidence collected during the last 15 years of hot dry rock hdr geothermal energy research has clearly indicated the very strong positive correlation between induced microearthquake locations and fluid flow paths within the fractured rock mass microseismic monitoring is now used regularly in hdr research as the only effective means of mapping hydraulic stimulations and monitoring hydromechanical processes during operation of the fractured reservoir many of the techniques that have been developed through hdr research are directly applicable to the hydrocarbon industry for the monitoring of hydraulic fracturing treatments waterflood operations and reservoir depletion this paper provides a brief introduction to the hydromechanical interactions that result in induced microseismicity and presents case studies from three european hdr sites where the monitoring of microseismic activity has proved vital in targeting production wells mapping the progress of stimulation and waterfloods and understanding the hydromechanical behaviour of the fractured system

a crustal structure profile across the northern continental margin of the south china sea an ocean bottom seismometer obs geophysical experiment was carried out across the northern continental margin of the south china sea two dimension kinematic ray tracing was used to construct synthetic records and to define the geological model along the obs profile according to the calculation and interpretation of refracted p wave phases the crustal thickness decreases from 22 km obs 1 in littoral area to 8 km obs 15 in deep sea the lower slope structured by volcanism changes sharply in moho depth from 22 to 9 km the volcanoes over the lower slope were markers of ocean continental transition zone a high velocity layer hvl with an average thickness of 4 km was found in the base of the lower crust over the shelf and slope the south china sea was originated by the passive rifting of south china continent and seafloor spreading however geological and geophysical data collected in the northern margin of the south china sea show a small amount of magma intruded into or erupted onto the crust during pull apart and breakup further analysis shows that the hvz in the base of the thinned continental crust was related to magmatism that occurred after the cessation of seafloor spreading of the south china sea magmatism during the crustal extension and breakup is very weak therefore the northern continental margin of the scs is classified as non volcanic passive margin the southern margin of the south china sea has a crust with a steady thickness of 18 24 km which is different from the nor them margin of the south china sea with a gradually thinned crust they constitute an asymmetrically conjugated pair of passive margins c 2001 elsevier science b v all rights reserved

slip tendency analysis fault reactivation potential and induced seismicity in a deep geothermal reservoir abstract a slip tendency analysis is used to assess the reactivation potential of shear and dilational fractures in a deep geothermal reservoir in the northeast german basin based on the notion that slip on faults is controlled by the ratio of shear to normal stress acting on the plane of weakness in the in situ stress field the reservoir rocks composed of lower permian sandstones and volcanics were stimulated by hydraulic fracturing a surprisingly low microseismic activity was recorded with moment magnitudes mw ranging from 1 0 to 1 8 the slip tendency analysis suggests a critically stressed reservoir exists in the sandstones whereas the volcanic rocks are less stressed rock failure first occurs with an additional pore pressure of 20 mpa presumed failure planes form a conjugate set and strike nw and ne slip failure is more likely than tensional failure in the volcanic rocks because high normal stresses prevent tensional failure these results from slip tendency analysis are supported by the spatial distribution of recorded microseismicity source characteristics indicate slip rather than extension along presumed ne striking failure planes this suggests that slip tendency analysis is an appropriate method that can be used to understand reservoir behavior under modified stress conditions

archaeal and bacterial lipids in authigenic carbonate crusts from eastern mediterranean mud volcanoes abstract we investigated the distributions and 13 c values of lipid biomarkers in authigenic methane related carbonate crusts formed on eastern mediterranean mud volcanoes a highly diverse suite of microbial membrane lipids was detected strongly 13 c depleted lipids diagnostic for archaea include isoprenoid glycerol diethers isoprenoid glycerol dialkyl glycerol tetraethers and several c 20 c 35 isoprenoid hydrocarbons bacterial lipids mainly consist of dialkyl glycerol diethers branched fatty acids and hopanoids showing important 13 c depletions albeit less than archaeal lipids the data provide further evidence for the involvement of archaea and bacteria in the anaerobic oxidation of methane aom and in the sequestration of methane derived carbon in authigenic carbonate crusts varying distributions and isotopic compositions of 13 c depleted lipids argue for heterogeneous aom related microbial consortia expanding on existing work at cold seeps distinctive biomarker features and inferred microbial assemblages are observed in these crusts in agreement with available phylogenetic data for the samples our results support the potential of lipids for distinguishing methanotrophic communities despite the observed variances conservative features in the abundances and isotopic offsets of microbial biomarkers occur likely reflecting the overall relationships between archaea and bacteria and the nature of carbon flow between them

methane seeps as ammonite habitats in the u s western interior seaway revealed by isotopic analyses of well preserved shell material methane seep deposits are common in the upper cretaceous pierre shale of the u s western interior they contain a rich fauna including ammonites bivalves gastropods sponges corals echinoids crinoids and fish in an effort to understand the role of ammonites in these ecosystems we examined a seep from the upper campanian didymoceras cheyennense zone in custer county south dakota that contains molluscs with well preserved shell material permitting isotopic analyses values of 13c of the micritic limestone at the seep range from 46 94 to 11 49 confirming the influence of anaerobic oxidation of methane on the isotopic composition of the dissolved inorganic carbon reservoir the ammonites also consistently display light values of 13c ranging from 13 71 to 0 68 these values are generally lighter than those in nonseep specimens from age equivalent rocks elsewhere in the basin 1 75 to 3 42 in a single specimen of baculites corrugatus from the seep light 13c values occur throughout ontogeny these data suggest that ammonites incorporated isotopically light methane derived carbon in their shells and lived near the vent fluids and methane oxidizing bacteria both juvenile and adult specimens are present implying that these ammonites spent their entire lives at the seep and formed an integral part of an interwoven community the values of 87sr 86sr in the limestone and well preserved fossils at the seep 0 707690 0 707728 are higher than that of the open ocean at this time 0 707659 these elevated values suggest that the seep fluids were imprinted with a radiogenic sr signature perhaps derived from equilibration with granitic deposits at depth during the initial uplift of the black hills

a new constraint on the antiquity of anaerobic oxidation of methane late pennsylvanian seep limestones from southern namibia late pennsylvanian seep limestones ca 300 ma enclosed in the ganigobis shales in southern namibia formed by microbial activity the process that induced carbonate precipitation was the anaerobic oxidation of methane the presence of 13 c depleted pentamethylicosane pmi 113 and a mixture of crocetane and phytane 112 in concert with similarly 13 c depleted pseudohomologous series of regular isoprenoids reveals that methanotrophic archaea oxidized methane anaerobically at the ancient seep site biphytane and a c 39 pseudohomologue are other archaeal molecular fossils with 13 c values of 99 and 97 respectively the former presence of sulfate reducing bacteria as the syntrophic partners of methanotrophic archaea in the anaerobic oxidation of methane is indicated by isotopically depleted iso and anteiso alkanes these compounds most probably derive from non isoprenoidal monoethers and diethers synthates of sulfate reducing bacteria these findings show that anaerobic oxidation of methane is at least 300 m y old extending the record of this process for 140 m y as the molecular fossils of archaea and bacteria are preserved in a product of their own metabolic activity i e methane derived carbonates with 13 c values as low as 51 the syngenicity of molecular fossils and enclosing deposits is unambiguous this reveals that microbially formed rocks can represent excellent archives for studying past biogeochemical processes

widespread venting of methane rich fluids in late cretaceous campanian submarine springs tepee buttes western interior seaway u s a from new mexico to montana campanian shales contain abundant submarine spring and seep deposits aligned along early laramide basement faults from spring conduit to sea floor characteristic lithofacies are a a vuggy pelletoid micrite core to 30 m height 5 m width b lucinoid bivalve coquina in pelletoid micrite or grainstone c carbonate slump breccias in shale d concretion bearing shale and e organic rich shale stable isotope analyses of early zoned marine core rock cements suggest a an oxidized methane source for the carbonate carbon b venting of methane charged fluids along active fracture zones and c methanogenesis in older and coeval organic carbon rich muds six consistently zoned foraminifer and macrofaunal communities suggest a strong environmental stress gradient over a few metres from spring vents to the adjacent sea floor these methane springs and their biotas were dynamic and episodically active over a 1 25 m y time span

evolution of middle to late cretaceous oceans a 55 m y record of earth s temperature and carbon cycle a new 55 m y global compilation of benthic foraminifera 13 c and 18 o for the middle to late cretaceous shows that there was widespread formation of bottom waters with temperatures 20 c during the cretaceous greenhouse world these bottom waters filled the silled north atlantic and probably originated as thermocline or intermediate waters in the tropical oceans carbon burial during the cretaceous oceanic anoxic events produced a positive 13 c shift in global carbon reservoirs but this is not particularly large especially by comparison with the remarkable late paleocene carbon maximum the interbasin 13 c gradient was unusually large during the cretaceous hot greenhouse probably because the north atlantic sills prevented the free exchange of waters in the deep basin the hot greenhouse ended when the equatorial atlantic gateway opened sufficiently to flood the deep north atlantic with relatively cool polar waters formed in the southern ocean

crustal scale seismic profiles across taiwan and the western philippine sea abstract we have used combined onshore and offshore wide angle seismic data sets to model the velocity structure of the taiwan arc continent collision along three cross island transects although taiwan is well known as a collisional orogen relatively few data have been collected that reveal the deeper structure resulting from this lithospheric scale process our southern transect crosses the hengchun peninsula of southernmost taiwan and demonstrates characteristics of incipient collision here 11 km thick transitional crust of the eurasian plate eup subducts beneath a large rapidly growing accretionary prism this prism also overrides the n luzon forearc to the east as it grows just west of the arc axis there is an abrupt discontinuity in the forearc velocity structure because this break is accompanied by intense seismicity we interpret that the forearc block is being detached from the n luzon arc and philippine sea plate psp at this point our middle transect illustrates the structure of the developing collision steep and overturned velocity contours indicate probable large scale thrust boundaries across the orogen the leading edge of the coherent psp appears to extend to beneath the east coast of taiwan deformation of the psp is largely limited to the remnant n luzon arc with no evidence of crustal thickening to the east in the huatung basin our northern transect illustrates slab continent collision the continuing collision of the psp and eup as the psp subducts the collisional contact is below 20 km depths along this transect ne of hualien this transect shows elements of the transition from arc continent collision to ryukyu arc subduction both of our models across the central range suggest that the paleozoic to mesozoic basement rocks there may have been emplaced as thick coherent thrust sheets this suggests a process of partial continental subduction followed by intra crustal detachment and buoyancy aided exhumation although our models provide previously unknown structural information about the taiwan orogen our data do not define the deepest orogenic structure nor the structure of western taiwan additional seismic active and passive geologic and geodynamic modeling work must be done to fully define the structure the active deformation zones and the key geodynamic process of the taiwan arc continent collision

cold seep deposits of beauvoisin oxfordian southeastern france and marmorito miocene northern italy microbially induced authigenic carbonates the relation of two well known ancient carbonate deposits to hydrocarbon seepage was confirmed by this study archaea are found to be associated with the formation of oxfordian seep carbonates from beauvoisin and with a miocene limestone from marmorito tube worm limestone carbonates formed due to a mediation by archaea exhibit extremely positive or extremely negative 13ccarbonate values respectively highly positive values 15 reflect the use of 13c enriched co2 produced by methanogenesis low 13c values of the marmorito carbonates 30 indicate the oxidation of seepage derived hydrocarbons likewise the 13c content of specific tail to tail linked isoprenoids biomarkers for archaea was found to be strikingly depleted in these samples as low as 115 the isotopic signatures corroborate that archaea were involved in the cycling of seepage derived organic carbon at the ancient localities another miocene limestone marmorito limestone shows a strong imprint of methanotrophic bacteria as indicated by 13c values of carbonate as low as 40 and biomarker evidence epifluorescence microscopy and field emission scanning electron microscopy revealed that bacterial biofilms were involved in carbonate aggregation in addition to lucinid bivalves previously reported from both localities we infer that sponges from beauvoisin and tube worms from marmorito depended on chemosynthesis as well low 13c values of nodules related to sponge taphonomy 27 indicate that sponges might have been linked to an enhanced hydrocarbon oxidation tube worm fossils from marmorito closely resemble chemosynthetic pogonophoran tube worms from recent cold seeps and are embedded in isotopically light carbonate 13c 30

the beast burrowed the fluid followed crustacean burrows as methane conduits abstract an extensive pockmark field with associated methane seep carbonates has recently been reported from the late albian lower cretaceous ubidepea mudstone of the black flysch group in the basque country northern spain but the exact pathways of the migrating methane rich fluids remained elusive here we provide petrographic stable carbon and oxygen isotope evidence that abundant crustacean burrows in the surrounding mudstone preserved as the trace fossil thalassinoides and the seep carbonates themselves have acted as long lasting fluid conduits in this system the thalassinoides infill generations show a diagenetic parasequence often starting with a distinctive lining followed by one to several phases of cementing of the burrow walls and burrow infills and finally late diagenetic sparry calcite that filled the remaining open cavities and conduits the micrite cementing the burrow walls shows negative 13 c values similar to those reported from the seep carbonates indicating that methane oxidation was involved in their precipitation rather than or in addition to the oxidation of other organic matter even the late diagenetic sparry calcite shows 13 c values as low as 30 4 versus pdb providing evidence that these burrows served as fluid conduits for an extended period of time our study supports the growing body of evidence that crustacean burrows play an important role in channeling seeping fluids in such systems we anticipate that this phenomenon is much more widespread than currently appreciated especially in examples where other types of fluid conduits are absent

archaea mediating anaerobic methane oxidation in deep sea sediments at cold seeps of the eastern aleutian subduction zone cold seeps in the aleutian deep sea trench support prolific benthic communities and generate carbonate precipitates which are dependent on carbon dioxide delivered from anaerobic methane oxidation this process is active in the anaerobic sediments at the sulfate reduction methane production boundary and is probably performed by archaea working in syntrophic co operation with sulfate reducing bacteria diagnostic lipid biomarkers of archaeal origin include irregular isoprenoids such as 2 6 11 15 tetramethylhexadecane crocetane and 2 6 10 15 19 pentamethylicosane pmi as well as the glycerol ether lipid archaeol 2 3 di o phytanyl sn glycerol these biomarkers are prominent lipid constituents in the anaerobic sediments as well as in the carbonate precipitates carbon isotopic compositions of the biomarkers are strongly depleted in 13c with values of 13c as low as 130 3 pdb the process of anaerobic methane oxidation is also reflected in the carbon isotope composition of organic matter with 13c values of 39 2 and 41 8 and of the carbonate precipitates with values of 45 4 and 48 7 this suggests that methane oxidizing archaea have accumulated within the microbial community which is active at the cold seep sites the dominance of crocetane in sediments at one station indicates that probably due to decreased methane venting archaea might no longer be growing whereas high amounts of crocetenes found at other more active stations may indicate recent fluid venting and active archaea comparison with other biomarker studies suggests that various archaeal assemblages might be involved in the anaerobic consumption of methane the assemblages are apparently dependent on specific conditions found at each cold seep environment selective conditions probably include water depth temperature degree of anoxia and supply of free methane

rare earth elements in authigenic methane seep carbonates as tracers for fluid composition during early diagenesis abstract authigenic carbonates forming at an active methane seep on the makran accretionary prism mainly consist of aragonite in the form of microcrystalline cryptocrystalline and botryoidal phases the 13 c carbonate values are very negative 49 0 to 44 0 v pdb agreeing with microbial methane as dominant carbon source the 18 o carbonate values are exclusively positive 3 0 to 4 5 v pdb and indicate precipitation in equilibrium with seawater at bottom water temperatures the content of rare earth elements and yttrium ree y determined by laser ablation inductively coupled plasma mass spectrometry la icp ms and solution icp ms varies for each aragonite variety with early microcrystalline aragonite yielding the highest cryptocrystalline aragonite intermediate and later botryoidal aragonite the lowest ree y concentrations shale normalised ree y patterns of different types of authigenic carbonate reflect distinct pore fluid compositions during precipitation microcrystalline aragonite shows high contents of middle rare earth elements mree reflecting ree patterns ascribed to anoxic pore water cryptocrystalline aragonite exhibits a seawater like ree y pattern at elevated total ree y concentrations indicating higher concentrations of rees in pore waters which were influenced by seawater botryoidal aragonite is characterised by seawater like ree y patterns at initial growth stages followed by an increase of light rare earth elements lree with advancing crystal growth reflecting changing pore fluid composition during precipitation of this cement conventional sample preparation involving micro drilling of carbonate phases and subsequent solution icp ms does not allow to recognise such subtle changes in the ree y composition of individual carbonate phases to be able to reconstruct the evolution of pore water composition during early diagenesis an analytical approach is required that allows to track the changing elemental composition in a paragenetic sequence as well as in individual phases high resolution analysis of seep carbonates from the makran accretionary prism by la icp ms reveals that pore fluid composition not only evolved in the course of the formation of different phases but also changed during the precipitation of individual phases

fracture mapping in the soultz sous forets geothermal field using microearthquake locations 1 in 2003 a massive hydraulic fracturing experiment was carried out at the european geothermal hot dry rock site at soultz sous forets france the 2 week injection of water generated a high level of microseismic activity triggering about 90 000 microearthquakes during and after the fluid injection of these 21 000 events detected at all stations were located individually with a grid search algorithm to characterize the extent of the seismic zones and ultimately of the fracture network the accuracy of these initial locations was around 70 m not sufficient to map detailed fracture patterns a precise relocation effort was undertaken to reduce the location uncertainties using three different techniques joint hypocenter determination jhd collapsing and multiplet analysis the collapsing method was added to the jhd results to further consolidate the hypocenters on the other hand a multiplet analysis was performed on the initial data set for identifying microearthquakes with similar waveforms and hence relocating relatively the correlated events the delays in traveltime were computed by wavelet analysis and the events were relocated using a grid search algorithm we found 7463 events whose seismograms correlated with a correlation coefficient of 0 8 or higher most of which were doublets multiplets are horizontal tube like structures with lengths from a hundred to several hundred meters striking along the direction of the maximum compressive horizontal stress we interpret these structures as the preferential paths where fluid flow is largely confined this hypothesis is reinforced by the good correlation in depth between the events and the fluid outflows observed in the well therefore we believe that these relocated events highlight the zones where the permeability of the reservoir is increased

high paleolatitude late cretaceous paleotemperatures new data from james ross island antarctica oxygen isotope analysis of well preserved macrofossils from the santonian campanian of james ross island and the maastrichtian of vega island antarctica indicates that cool high paleolatitude temperatures prevailed during the late cretaceous and suggests that cooling occurred between the santonian campanian and the maastrichtian although more than 50 of the material showed diagenetic alteration 52 unaltered aragonite and calcite samples were analyzed mean delta sup 18 o and calculated paleotemperature values were minus 0 23 per thousand and 13 6 c respectively for the santonian campanian and 0 66 per thousand and 11 7 c respectively for the masstrichtian in conjunction with recent late cretaceous paleoclimatic data from high northern paleolatitudes these data indicate the presence of cool polar regions with broad climatic zonation during the late cretaceous this may have partly controlled faunal distributions

vast fields of hydrocarbon derived carbonate chimneys related to the accretionary wedge olistostrome of the gulf of cadiz we report the first discovery and sampling of vast fields of hydrocarbon derived carbonate chimneys along the gulf of cadiz continental slope at depths between 500 and 1200 m a large variety of carbonate chimneys more than 200 samples were recovered from four different areas named the diasom tasyo gbf guadalquivir basin and esf east moroccan fields observations from an underwater camera revealed a spectacular high density of pipe like chimneys some of them longer than 2 m lying over the sea floor and some protruding from muddy sediment local fissures and alignment of isolated chimneys were also observed suggesting that their distribution is controlled by fault planes chimneys collected show a wide range of morphological types spiral cylindrical conical mushroom like and mounded with numerous nodule protuberances and ramified fluid channelways the chimneys are mainly composed of authigenic carbonates ankerite fe bearing dolomite and calcite with abundance of iron oxides forming agglomerates of pseudo pyrite framboids n 18 o isotopic values vary from 0 7 to 5 5x whereas n 13 c values indicate that chimney carbonates are moderately depleted in 13 c ranging from 346x to 320x pdb interpreted as formed from a mixture of deep thermogenic hydrocarbons and shallow biogenic methane these vast fields of carbonate chimneys imply new considerations on the importance of hydrocarbon fluid venting in the gulf of cadiz and moreover on the active role of the olistostrome accretionary wedge of the gibraltar arc b 2003 elsevier science b v all rights reserved

eocene deep sea communities in localized limestones formed by subduction related methane seeps southwestern washington densely populated communities of soft bottom dwelling taxa similar to those found today along subduction zones off the coasts of japan and oregon have been discovered in very localized deep water limestones of late middle to late eocene age along the southwestern margin of washington subduction was prevalent in this area during this time and compressive forces squeezed subsurface methanerich waters onto the ocean floor where opportunistic bivalves especially modiolus calyptogena and thyasira vestimentiferan tube worms serpufid tube worms siliceous sponges very small limpets trochid and turbinid archaeogastropods and other macrobenthos colonized these assemblages are the earliest recorded biologic communities formed in response to methane seeps in subduction zones

diagenetic alteration affecting δ18o δ13c and 87sr 86sr signatures of carbonates a case study on cretaceous seep deposits from yarlung zangbo suture zone tibet china abstract seep carbonates provide excellent records of past seepage activities and have been commonly considered to preserve primary unaltered stable carbon isotope signatures however late diagenetic reactions may overprint original isotopic compositions but the mode and effect of such alterations are poorly understood in particular there are significant uncertainties regarding how carbon and strontium isotopic compositions of seep carbonates respond to diagenesis this study reports recently discovered cretaceous hydrocarbon seep deposits from the yarlung zangbo suture zone tibet china that have experienced substantial diagenetic alteration that is shown by recrystallization and secondary veins unitary linear recursive analysis was applied to 13 c values and 87 sr 86 sr ratios of the seep carbonates to evaluate the degree of secondary modification and to quantitatively constrain the compositions of primary carbonates and late diagenetic fluids the 18 o values range from 11 8 to 2 2 13 c values from 34 1 to 12 9 and 87 sr 86 sr ratios from 0 706221 to 0 706808 the heterogeneity in isotopic compositions and the observation that the most negative 18 o values occur in samples with the most extensive recrystallization indicate significant and spatially heterogeneous modification of isotope compositions during late diagenesis the linear correlations between 13 c values and 18 o values for matrix micrites r 2 0 54 and between bulk carbonate 87 sr 86 sr ratios and 18 o values r 2 0 85 are best explained by burial diagenetic overprinting of oxygen strontium and even carbon isotopic compositions rather than by meteoric water hypergenesis extrapolated values of 13 c and ratios of 87 sr 86 sr against a 18 o value of 2 average value of calcite precipitated in isotopic equilibrium with coeval cretaceous seawater that would characterize the primary carbonate give an end member 13 c value of 34 and an end member 87 sr 86 sr ratio of 0 7072 the end member isotopic values obtained by this extrapolation suggest that the primary seep carbonates with low 13 c values and high 87 sr 86 sr ratios were formed by anaerobic oxidation of methane near the seafloor in contrast the measured 18 o values and 87 sr 86 sr ratios reflect late diagenetic fluids represented by burial pore water characterized by a low 87 sr 86 sr ratio and high temperature our findings reveal that 13 c values can only be moderately and 87 sr 86 sr ratios can be significantly altered during late diagenesis and show that it is possible to quantitatively assess the primary composition of diagenetically altered seep carbonates

formation of methane related authigenic carbonates within the bioturbated zone an example from the upwelling area off vietnam abstract in the biologically high productive area off vietnam authigenic carbonates formed in the bioturbated zone while methane was oxidized microbially under anaerobic conditions open crustacean burrows spongeliomorpha connected to the seafloor acted as conduits for methane as suggested by intense cementation of burrow walls having a light c isotope signature although seawater circulated within these open inhabited tubes conditions favorable for anaerobic oxidation of methane aom occurred trypanites cementation started at several spots that coalesced later to form the nodule carbon isotopes indicate a biogenic methane source 13 c carb reaching 49 to 40 v pdb while higher 13 c values imply mixing with carbon from other sources that is very likely within the bioturbated zone the cement is generally fine grained 18 o values of 5 1 reflect the general 18 o enriched isotope signature of the bottom water in south china sea especially during glacial times but influence of water released from decaying gas hydrate cannot be excluded the studied nodule was found on top of a slump that displaced it

crustal structure across the xisha trough northwestern south china sea located at the northwestern part of the south china sea scs between the hainan and xisha paracel islands the xisha trough represents a failed rift in conjunction with the opening of the scs between 32 and 17 ma from west towards east within a scale of several hundred kilometers it presents all major stages of the rifting process and thus provides an ideal place to study the rifting process in great details in the autumn of 1996 a joint team of sino german scientists carried out a wide angle seismic experiment across the xisha trough with 10 ocean bottom hydrophones obh along a 237 km nnw sse oriented profile which was surveyed in 1987 with multi channel seismic mcs method by bgr of germany and soa of china favorable weather conditions and the powerful 4 x 12 1 air gun array rendered very good quality data with seismic signals observed at the offset of up to 110 km a detailed velocity depth model was obtained by using an interactive trial and error 2d ray tracing method interpretation of the nics data published by bgr provides very good geometrical constraints of the complex upper crustal structure which is characterized by fault blocks half horsts and half grabens filled with syn and post rift cenozoic sediments the velocity model in turn confirms the major structure outlined by the interpretation of the mcs data showing a varying sedimentary layer between i and 4 km of thickness and velocities between 1 7 and 4 5 km s the p wave velocity of 5 5 km s on the top of the crystalline basement is relatively low suggesting strong weathering within the crystalline crust the velocity increases downward continuously to 6 8 km s at the bottom of the crust without a clear differentiation in the middle crust showing clearly its continental nature even beneath the xisha trough the moho is marked by a sharp first order interface with a velocity of 8 0 8 1 km s at the uppermost mantle the moho depth is 15 km beneath the center of the trough and increases gradually to more than 25 kin towards north and south corresponding to an extreme thinning of the pre rift continental crust from more than 25 kin under the coast line to only 8 kin beneath the xisha trough the similar velocity structure of the continental nature on both sides of the xisha trough suggests a homogeneous pre rift continental setting the sharp moho and the lack of high velocity body hvb in the lower crust imply no magmatic underplating which is very different to interpretations across the eastern part of the continental margin in northern south china sea the intense faulting in the upper crust the strong but rather symmetrical crustal thinning centered at the xisha trough and the close neighborhood to the open scs nw subbasin suggest a pure shear rifting which failed most likely at the phase shortly before the continental breakup c 2001 elsevier science b v all rights reserved

a miocene chemosynthetic community from the ogaya formation in joetsu evidence for depth related ecologic control among fossil seep communities in the japan sea back arc basin abstract two large carbonate bodies within deep water sediments of the uppermost middle miocene ogaya formation at kita kuroiwa niigata prefecture central japan are identified as an ancient hydrocarbon seep site based on petrographic features such as acicular and sparry calcite cements and clotted micrite with 13c values as low as 38 0 vs vpbd and a low diversity fauna of vesicomyid and mytilid bivalves and provannid gastropods compared to well studied coeval seep communities from the japan sea back arc basin species diversity is particularly low at the kita kuroiwa site while the percentage of seep obligate taxa taxa that are restricted to this type of environment is very high largely due to the absence of predatory gastropods such as naticids and buccinids modern seep communities show a decrease in species diversity and an increase in seep obligate taxa with depth due to the lower abundance and diversity of background colonists entering cold seep habitats likewise depth is here considered as the most likely cause for the observed differences in community structure because the kita kuroiwa seep site was located in considerably deeper water 1000 2000 m than the comparable coeval seep sites in the japan sea back arc basin

definition of late cretaceous stage boundaries in antarctica using strontium isotope stratigraphy abstract new 87sr 86sr analyses of macrofossils from 13 key marker horizons on james ross and vega islands antarctica allow the integration of the antarctic late cretaceous succession into the standard biostratigraphic zonation schemes of the northern hemisphere the 87sr 86sr data enable late cretaceous stage boundaries to be physically located with accuracy for the first time in a composite southern hemisphere reference section and so make the area one of global importance for documenting late cretaceous biotic evolution particularly radiation and extinction events the 87sr 86sr values allow the stage boundaries of the turonian coniacian coniacian santonian santonian campanian and campanian maastrichtian as well as other levels to be correlated with both the united kingdom and united states these correlations show that current stratigraphic ages in antarctica are too young by as much as a stage immediate implications of our new ages include the fact that inoceramus madagascariensis a useful

late cretaceous extinction patterns in antarctica new correlations of marine clastic sedimentary rocks exposed within the james ross basin antarctica have shown that the mid to late cretaceous succession is in excess of 5 km thick plotting the ranges of the principal molluscan macrofossils against the revised stratigaphy indicates that inoceramid bivalves are totally absent and dimitobelid belemnites extremely rare throughout an extensive 1400 m thick maastrichtian succession these early extinction patterns are interpreted to be due to both a regional shallowing event and a pronounced phase of high latitude campanian maastrichtian cooling cool polar bottom waters may have been forming by as early as mid to late campanian times

the stress regime in a rotliegend reservoir of the northeast german basin in situ stresses have significant impact either positive or negative on the short and long term behaviour of fractured reservoirs the knowledge of the stress conditions are therefore important for planning and utilization of man made geothermal reservoirs the geothermal field gros schonebeck 40 km north of berlin germany belongs to the key sites in the northeastern german basin we present a stress state determination for this lower permian rotliegend reservoir by an integrated approach of 3d structural modelling 3d fault mapping stress ratio definition based on frictional constraints and slip tendency analysis the results indicate stress ratios of the minimum horizontal stress s hmin being equal or increasing 0 55 times the amount of the vertical stress s v s hmin 0 55s v and of the maximum horizontal stress s hmax 0 78 1 00s v in stress regimes from normal to strike slip faulting thus acting stresses in the 4 100 m deep reservoir are s v 100 mpa s hmin 55 mpa and s hmax 78 100 mpa values from hydraulic fracturing support these results various fault sets of the reservoir are characterized in terms of their potential to conduct geothermal fluids based on their slip and dilatation tendency this combined approach can be adopted to any other geothermal site investigation

rock specific hydraulic fracturing and matrix acidizing to enhance a geothermal system concepts and field results abstract enhanced geothermal systems egs are engineered reservoirs developed to extract economic amounts of heat from low permeability and or porosity geothermal resources to enhance the productivity of reservoirs a site specific concept is necessary to actively make reservoir conditions profitable using specially adjusted stimulation treatments such as multi fracture concepts and site specific well path design the results of previously performed stimulation treatments in the geothermal research well gtgrsk4 05 at gros schonebeck germany are presented the reservoir is located at a 4100 4300 m depth within the lower permian of the ne german basin with a bottom hole temperature of 150 c the reservoir rock is classified by two lithological units from bottom to top volcanic rocks andesitic rocks and siliciclastics ranging from conglomerates to fine grained sandstones fluvial sediments the stimulation treatments included multiple hydraulic stimulations and an acid treatment in order to initiate a cross flow from the sandstone layer the hydraulic stimulations were performed in different depth sections two in the sandstone section and one in the underlying volcanic section in low permeability volcanic rocks a cyclic hydraulic fracturing treatment was performed over 6 days in conjunction with adding quartz in low concentrations to maintain a sustainable fracture performance flow rates of up to 150 l s were realized and a total of 13 170 m3 of water was injected a hydraulic connection to the sandstone layer was successfully achieved in this way however monitoring of the water level in the offsetting well egrsk3 90 which is 475 m apart at the final depth showed a very rapid water level increase due to the stimulation treatment this can be explained by a connected fault zone within the volcanic rocks two gel proppant treatments were performed in the slightly higher permeability sandstones to obtain long term access to the reservoir rocks during each treatment a total of 100 ton of high strength proppants was injected with 500 m3 of cross linked gel the subsequent production test in conjunction with flowmeter logging showed an improvement of productivity by a factor of more than 4 due to assumed residual drilling mud constituents calcite dolomite and aragonite in the near wellbore vicinity an acid matrix stimulation was performed thereafter using a coil tubing unit the following nitrogen lift test demonstrated another increase of productivity by 30 50 to an overall increase by a factor of 5 5 6 2