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

50 ma initiation of hawaiian emperor bend records major change in pacific plate motion the hawaiian emperor bend has played a prominent yet controversial role in deciphering past pacific plate motions and the tempo of plate motion change new ages for volcanoes of the central and southern emperor chain define large changes in volcanic migration rate with little associated change in the chain s trend which suggests that the bend did not form by slowing of the hawaiian hot spot initiation of the bend near kimmei seamount about 50 million years ago ma was coincident with realignment of pacific spreading centers and early magmatism in western pacific arcs consistent with formation of the bend by changed pacific plate motion

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

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

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

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

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

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

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

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

comment on a 40ar 39ar and u pb isotopic study of the ilimaussaq complex south greenland implications for the 40k decay constant and the duration of magmatic activity in a peralkaline complex by krumrei et al

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

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

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

a 40ar 39ar and u pb isotopic study of the ilimaussaq complex south greenland implications for the 40k decay constant and for the duration of magmatic activity in a peralkaline complex abstract magmatism in the gardar province south greenland is related to two main rifting events at 1280 ma and 1180 to 1140 ma little is known about the duration of the magmatic activity in a specific complex the ilimaussaq intrusion belongs to the second period of rifting and comprises an extraordinary diversity of granitic and syenitic rock types which intruded and fractionated in three successive magmatic events as the intrusion contains some of the most evolved incompatible element rich rocks on earth it was chosen for a detailed geochronological study to quantify the duration of melt production intrusion fractionation and cooling amphiboles which are abundant in all rock types including pegmatites and late magmatic veins were dated using the 40 ar 39 ar technique since the solidus temperature of the most evolved melts is below the closure temperature of amphibole and no later heating event occurred the 40 ar 39 ar ages reflect the magmatic crystallisation and can be used to determine the duration of igneous differentiation the 40 ar 39 ar plateau ages range between 1142 6 2 2 ma and 1152 3 3 7 ma using the steiger and jager steiger r h and jager e 1977 subcommision on geochronology convention on the use of decay constants in geo and cosmochronology earth planet sci lett 36 359 362 40 k decay constant these ages are younger than an u pb age of 1160 5 ma on baddeleyite from the first magma batch our results indicate that the 40 k decay constant of steiger and jager may be too high a lambda similar to that proposed by kwon et al kwon j min k bickel p and renne p r 2002 statistical methods for jointly estimating decay constant of 40 k and age of a dating standard math geol 34 457 474 is required to make the 40 ar 39 ar match the u pb age

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

comment to distribution and geochronology of the oregon plateau u s a flood basalt volcanism the steens basalt revisited by m e brueseke et al j volcanol geotherm res 161 2007 187 214 abstract the 40 ar 39 ar stepheating results of brueseke et al 2007 are critically evaluated firstly for possible alteration of the samples dated steps passing the alteration index test baksi 2007a can then be used to derive plateau ages which must satisfy rigorous statistical tests of the eleven samples studied by brueseke et al 2007 only four yield plateau values that reflect eruption ages these suggest steens basalt was erupted within a relatively short period of time 0 2 m y considerably less than the 1 m y suggested by the authors the seeming difference between the plateau ages for the steens mountain basalts obtained by these authors and two earlier attempts is resolved by a proper adjustment of ages at various laboratories for interlaboratory calibration differences and by rejecting ages from altered samples the age of the important steens mountain geomagnetic polarity transition is 16 59 0 03 ma

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

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

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

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

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

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

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

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

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

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

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

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

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

reply to comment on precise k ar 40ar 39ar rb sr and u pb mineral ages from the 27 5 ma fish canyon tuff reference standard by m a lanphere and h baadsgaard

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

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

reevaluation of plate motion models based on hotspot tracks in the atlantic and indian oceans abstract plate motion models based on hotspot tracks in the atlantic and indian oceans predict minimal movement less than a few millimeters per year between these hotspots and their counterparts in the pacific ocean for the past 100 m yr whereas plate circuit exercises indicate relative motions of 20 mm yr hotspot based models also suggest that the rajmahal traps india were located 1000 km away from the kerguelen hotspot at 115 ma and the deccan traps india were located a similar distance from the reunion hotspot at 65 ma this is at odds with conclusions derived from paleomagnetism plate circuits and geochemical parameters that suggest a genetic link between flood basalt provinces in india and hotspots in the indian ocean these divergent views may be explained by plume action 1000 km from its center or errors in the hotspot motion models the latter hypothesis is scrutinized in this article by examination of the radiometric ages for hotspot tracks in the atlantic and indian oceans the

global plate motion models incorporating the velocity field of itrf96 in this paper incorporating the itrf96 velocity field that is free of any tectonic plate model assumption a new present day plate motion model relative to the itrf96 reference frame called the itrf96vel is determined the total angular momentum of all tectonic plates with regards to the itrf96vel shows that the itrf96 rotates in a right handed sense relative to the no net rotation nnr reference frame at 0 164 degrees m yr about 50 7 degrees s 65 8 degrees e this means that itrf96 is not sufficiently concordant with the definition of the conventional terrestrial reference system ctrs in order to more properly compare plate motions from the itrf96 velocity field with the nnr nuvel1a another plate motion model relative to the nnr reference frame called the nnr itrf96vel is also established the results indicate that the nnr itrf96vel is quite consistent with the nnr nuvel1a the consistency testifies to the reliability of the nnr nuvel1a and shows the tectonic plate motions were steady over past millions of years