microbial fabrics from neogene cold seep carbonates northern apennine italy abstract a number of hydrocarbon seep carbonate masses are hosted within miocene and pliocene siliciclastic units along the apennine range and sicily and are mainly composed of micritic and microsparitic textures geomicrobiological analysis of some of these deposits shows that preserved microbial processes are few and the contribution of microbe derived textures to their construction is volumetrically very limited in the carbonate groundmass of two northern apennine miocene and pliocene seep carbonate deposits uncommon and well preserved features suggest direct and indirect evidence of microbial activity some of these features are interpreted as the mineralization products of microbial textures and include complex alveolar textures and fossilized biofilms that line and fill microconduits pores and other voids similar to living bacterial aggregations recovered in modern seep carbonates other mineral structures such as spheroids and rhombs with concentric fabrics composed of calcite dolomite alternations abound as cement components and suggest a nucleation via bacterial sulfate reduction processes a similar origin is also assumed for the acicular aragonite bundles that in the miocene seep carbonate mass enclose dense clusters of millimeter size filamentous morphologies of biological origin

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

miocene chemoherms of the northern apennines italy in the miocene of the northern apennines methane derived limestones from various geologic settings represent important examples of fossil chemoherms and provide a basis for more accurate interpretations of seepage systems the systematic study of fossil chemoherms has allowed the definition of new field and compositional criteria for the recognition of these deposits which were previously based almost exclusively on negative carbon isotope composition and peculiar chemosynthetic communities this has constrained the relations between seepage and sedimentary and tectonic instability processes we suggest that the peculiar brecciated structures associated with fossil chemoherms are related to diapirism of overpressured pelitic sediments due to fluid venting fluidization of sediments increases the instability of mudstones in which chemoherms are contained thus favoring gravity slumping processes and the reworking of many chemoherms

the cenozoic ch4 derived carbonates of monferrato nw italy a solid evidence of fluid circulation in the sedimentary column abstract two types of methane derived carbonates each with different lithological and paleontological signatures have been distinguished in the oligocene miocene sediments of monferrato nw italy 1 irregularly shaped metre sized rock bodies characterized by the widespread occurrence of remains of large bivalves lucina sp these bodies include two subtypes differing in the lithological characteristics of the cemented sediments a lucina rich marly limestones encased in langhian outer shelf marls they document a slow seepage of ch4 rich fluids at the paleo sea floor b lucina bearing cemented mud breccias found either as cemented masses in the original stratigraphic position or as redeposited blocks within upper messinian chaotic block in matrix sediments these carbonate bodies document the activity of submarine mud volcanoes during the late messinian in particular they document intermittent fluid emission ranging from violent eruptive phases responsible for the extrusion of soft mud breccias at the sea floor to quiet degassing phases that promoted colonization by chemosymbiotic communities and localized cementation 2 very irregularly shaped strongly cemented mainly coarse grained clastic sediments reaching the lateral extent of few hundred meters and the thickness of few tens of meters they occur within oligocene to messinian sediments lack remains of chemosymbiotic taxa and are highly fractured with fractures filled with sediments and cements these carbonate cemented masses here referred to as macroconcretions result from the precipitation of carbonate cements within buried sediments flushed by ascending ch4 rich fluids they document a complex fluid circulation pattern in the sedimentary column in which so4 rich waters were drawn from surrounding sediments by the fast and prolonged flow of ch4 rich fluids and promoted anaerobic oxidation of methane and the precipitation of carbonate cements the polyphase network of clastic dykes and veins that characterize macroconcretions is related to an intermittent fluid flow regime dykes formed during fast upward flows of sediment rich fluids whereas carbonate filled veins formed during slower degassing phases the local lithostratigraphic and structural framework allow to correlate genetically and chronologically the macroconcretions to lucina bearing mud breccias consequently macroconcretions are here regarded as the result of cementation along fluid conduits feeding messinian mud volcanoes at the sea floor the massive release of fluids could have played a role in triggering large scale mass wasting events responsible for the emplacement of sedimentary melanges including ch4 derived rocks in the messinian

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

palaeogene and neogene cold seep communities in barbados trinidad and venezuela an overview palaeogene and neogene fossiliferous carbonates from barbados trinidad and northern venezuela are interpreted to have formed at ancient cold seep sites the hydrocarbon seepage that fuelled these chemosymbiotic ecosystems was related to tectonic activity in the southern caribbean region particularly the subduction of the caribbean plate beneath the north atlantic plate the carbonates and fossils from the scotland district north eastern barbados are eocene miocene in age and are associated with two distinct tectonic units the sub oceanic fault zone and a diapiric melange the sub oceanic fault zone is the tectonic junction between accretionary prism sediments and over lying thrust sheets of fore arc basin sediments the loading of the thrust sheets caused methane rich fluids to be expelled from the accretionary prism sediments and channelled to the sea floor via the sub oceanic fault zone where it supported chemosymbiotic invertebrate communities containing vesicomyid lucinid thyasirid solemyid and nuculanid bivalves a variety of gastropods and possibly vestimentiferan tube worms the diapiric melange is considered to represent sediment that failed under pressure in the accretionary prism and was remobilised as a diapir that extruded onto the sea floor providing a conduit for methane and other hydrocarbons that sustained a chemosynthesis based community of vesicomyid lucinid and nuculanid bivalves and various gastropods the geological setting of fossiliferous carbonates known as freeman s bay limestone in southwest trinidad has been less fully investigated the freeman s bay limestone is a member of the miocene lengua formation which is believed to have formed in a fore deep basin on lapping onto an accretionary prism formed by the subduction of proto caribbean crust beneath the south american plate the carbonates and fossils of the fbl including the bivalves pleurophopsis unioides van winkle 1919 and thyasira adoccasa van winkle 1919 lucinids nuculanids and bathymodiolins and provannid and other gastropods are interpreted to have formed at palaeo seep sites on the accretionary prism little is currently known about the geological setting of the fossils collected from the miocene huso member of the pozon formation from northern venezuela but a seep origin is strongly suspected based on the taxa present like the fossil assemblages from barbados and trinidad the venezuelan material is dominated by vesicomyid bivalves together with lucinid thyasirid bathymodiolin and solemyid bivalves and various gastropods these taxa are characteristics of modern cold seep communities most comparisons between the fossil caribbean and modern seep fauna are necessarily at the generic or family level although in some cases individual species are found at both ancient and modern seep sites for example the gastropod cataegis meroglypta is found in seep carbonate from the sofz of barbados and the fbl of trinidad as well as at modern seeps on the barbados prism at the generic level this study has revealed the first fossil occurrences of abyssochrysos and provanna in the caribbean such temporal and spatial links further the understanding of both local and global patterns of biogeographic distribution of cold seep fauna

the timing of martian valley network activity constraints from buffered crater counting abstract valley networks concentrations of dendritic channels that often suggest widespread pluvial and fluvial activity have been cited as indicators that the climate of mars differed significantly in the past from the present hyperarid cold desert conditions some researchers suggest that the change in climate was abrupt while others favor a much more gradual transition thus the precise timing of valley network formation is critical to understanding the climate history on mars we examine thirty valley network incised regions on mars including both cratered upland valley networks and those outside the uplands and apply a buffered crater counting technique to directly constrain when valley network formation occurred the crater populations that we derive using this approach allow assessment of the timing of the last activity in a valley network independent of the mapping of specific geological units from these measurements we find that valley networks cluster into two subdivisions in terms characteristics and age 1 valley network activity in the cratered highlands has an average cessation age at the noachian hesperian boundary and all valleys that we crater counted are early hesperian or older no evidence is found for valley networks in the cratered uplands of late hesperian or amazonian age the timing of the cessation of cratered upland valley network activity at the noachian hesperian boundary also corresponds to a decline in the intensity of large crater formation and degradation and to the apparent end of phyllosilicate type weathering 2 a few valley network incised regions formed outside of the cratered uplands on volcanic edifices in association with younger impact craters and on the rim of valles marineris we applied our buffered crater counting technique to four such valleys on the volcanoes ceraunius tholus hecates tholus and alba patera and on the rim of echus chasma and find that each has distinctive and different late hesperian or early amazonian ages indicating that valley networks formed from time to time in the post noachian period unlike the cratered upland valley networks these isolated occurrences are very local and have been interpreted to represent local conditions e g snowpack melted during periods of intrusive volcanic activity in contrast to a gradual cessation in the formation of valley networks proposed by some workers our new buffered crater counting results indicate a relatively abrupt cessation in the formation of the widespread cratered upland valley networks at approximately the end of the noachian followed only by episodic and very localized valley network formation in later mars history very likely due to specific conditions e g local magmatic heating these valley network ages and correlations are thus consistent with a major change in the near surface aqueous environment on mars at approximately the noachian hesperian boundary the noachian environment supported surface running water and fluvial erosion across mars in the cratered uplands enhanced crater degradation and a weathering environment favoring the formation of phyllosilicates the hesperian amazonian environment was more similar to the hyperarid cold desert of today with valley networks forming only extremely rarely and confined to localized special conditions sources of water for these latter occurrences are likely to be related to periodic mobilization and equatorward migration of polar volatiles due to variations in spin axis orbital parameters and to periodic catastrophic emergence of groundwater

the effects of sediment supply and concentrations on the formation timescale of martian deltas abstract we used a comprehensive 2 d and 3 d basin filling morphodynamical model to explore the effects of changing hydrologic and sedimentary conditions on delta formation under martian conditions spatial and temporal deposition of sediment into a body of standing water was simulated using event based time stepping e g seasons river and sediment discharge were calculated using the darcy weisbach equation for width and depth averaged flow velocity and well known and tested terrestrial sediment transport predictors modified for application to martian flows a range in sediment grain sizes was determined from both landers and orbiting spacecraft data in order to include grain sizes typical of mars and yet representative of the martian deltas several different scenarios of seasonal river discharge and sediment supply were explored to encompass a range of possible formation conditions with the ability to track sediment as it is transported throughout the basin it is apparent that non negligible amounts of material are moved beyond the delta forming region this loss of sediment increased with river discharge increasing the gap between the calculated and modeled formation timescales these results have important implications for the formation timescales of the deltas and the small number of identifiable deltas on mars today formation timescales that consider only the supply of sediment to the system and do not take into account factors affecting deposition and delta formation are underestimates of the actual amount of time needed to form the deposits the lack of identifiable deltas in many paleolakes is likely a result of significant sediment transport beyond the channel mouth causing the expected delta deposit to be draped throughout the basin

late jurassic early cretaceous hydrocarbon seep boulders from novaya zemlya and their faunas the paper describes late jurassic early cretaceous seep carbonate boulders from the russian arctic island of novaya zemlya collected in 1875 by a e nordenskiold during his expedition to siberia the carbonates are significantly depleted in heavy carbon isotopes 13c values as low as ca 40 and show textures typical for carbonates formed under the influence of hydrocarbons such as fibrous carbonate cements and corrosion cavities the rocks contain index fossils of late oxfordian early kimmeridgian late tithonian jurassic and latest berriasian early valanginian cretaceous age the fossil fauna is species rich and dominated by molluscs with subordinate brachiopods echinoderms foraminifera serpulids and ostracods most of the species including two chemosymbiotic bivalve species likely belong to the background fauna only a species of a hokkaidoconchid gastropod and a possible abyssochrysoid gastropod can be interpreted as restricted to the seep environment other seep faunas with similar taxonomic structure are suggestive of rather shallow water settings but in case of novaya zemlya seep faunas such structure might result also from high northern latitude

authigenic carbonate formation revealed by lipid biomarker inventory at hydrocarbon seeps a case study from the okinawa trough abstract authigenic carbonates were recovered from the northern okinawa trough at 540 700 m water depth development of microbial communities and seepage dynamics driving the precipitation of authigenic carbonates remains poorly constrained even though the source of methane rich fluids formation of fe rich carbonates and the potential driving forces were previously reported here petrologic observations stable carbon and oxygen isotopic compositions mineralogy and lipid inventories of authigenic carbonates from the northern okinawa trough were analyzed the carbonate minerals were comprised predominantly of aragonite high magnesium calcite and siderite the presence of molecular fossils diagnostic for anaerobic methane oxidizing archaea anme and sulfate reducing bacteria srb with pronounced 13c depletions as low as 134 together with highly negative 13ccarb values as low as 55 8 suggest that the carbonates precipitated from anaerobic oxidation of methane aom with microbial methane as the predominant carbon source the difference between measured and calculated 18ocarb values based on 0 of sea water 18o vs v smow was higher than 3 in one of the carbonates ggd16 reflecting an origin from gas hydrate dissociation most of the carbonates revealed 18o offsets between measured and calculated values within 3 or a lower measured 18o than calculated value suggesting a mixture of methane derived carbonates low 13c high 18o and detrital origin carbonates high 13c low 18o biomarker patterns varied significantly among samples a suite of 13c depleted biomarkers indicated the predominance of an anme 1 assemblage for all samples suggesting carbonates formed at low to medium methane flux the predominance of anme 1 abundant detrital minerals and allochthonous biomarkers as well as low carbonate contents indicate that most samples formed at greater depth within the sediment column only one carbonate sample in this study is interpreted to have precipitated at relatively shallower depth as indicated by the occurrence of crocetane dominance of aragonite and higher overall carbonate content

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

a new straight chain hydrocarbon biomarker associated with anaerobic methane cycling abstract 13c depleted e and z n tricos 10 enes are prominent biomarkers in an anaerobic microbial mat at black sea methane seeps these n alkenes co occur with archaeal irregular c25 isoprenoid hydrocarbons namely 2 6 10 15 19 pentamethylicosane pmi and enes pmi low 13c values 73 and 77 for n tricosenes and pmi imply the anabolism of methane carbon by their source biota the n tricosenes apparently originate from microorganisms closely associated with if not identical to isoprenoid producing methane metabolizing archaea methane seep deposits of tertiary to jurassic ages showed the absence of n tricosenes but 13c depleted n tricosane 13c as low as 87 a plausible diagenetic product was observed in enhanced concentrations in 7 out of 9 samples studied it is proposed that a preference of n tricosane over the enveloping n alkanes may provide a specific hydrocarbon fingerprint for the anaerobic cycling of methane in ancient settings

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

paleohydrology of eberswalde crater mars abstract eberswalde crater mars contains a well preserved fluvial distributary network in a likely deltaic setting the meandering inverted paleochannels and closed drainage basin of this deposit support relatively well constrained estimates of channel forming discharge over an individual event flood timescale runoff production event and annual timescales and longevity of deposition geologic timescale during the late hesperian to early amazonian epochs the width and meander dimensions of two inverted paleochannels reflect the channel forming discharge from event floods 200 to 400 m 3 s the deposit surface indicates the level 1400 to 1350 m and surface area 410 to 810 km 2 of the likely paleolake and the topography and mapped extent of tributaries constrain the watershed area 5000 to 17 000 km 2 based on these results and terrestrial empirical constraints on evaporation and sediment concentration we evaluated three hypothetical water sources meltwater liberated by the nearby holden crater impact continuous deposition over 10 1 10 2 years intermittent rainfall or snowmelt during finite periods controlled by orbital evolution deposition over 10 4 10 6 years and highly infrequent runoff or melting of accumulated snowpacks following distant impacts or secular changes in orbital parameters local impact generated runoff and highly infrequent rainfall or snowmelt require unreasonably high and low rates of evaporation respectively to maintain the paleolake level the local impact hypothesis alternatively depends on one flooding episode with very high concentrations of fluvial sediment that are inconsistent with morphologic considerations multiple primary impact craters in the area postdate holden ejecta but were later dissected indicating fluvial erosion long after the holden impact intermittent rainfall of 1 cm day and seasonal snowmelt are both consistent with our results over a deposition timescale totaling 10 4 10 6 years

authigenic carbonates in upper miocene sediments of the tertiary piedmont basin nw italy vestiges of an ancient gas hydrate stability zone a wide array of carbonate rich rocks has been recognized in the tertiary piedmont basin nw italy hosted in lower messinian slope deposits carbonate cements show negative 13 c values and positive 18 o values suggesting that carbonate precipitation was induced by microbial degradation of methane produced from gas hydrate destabilization two groups of rocks have been distinguished 1 lucina bearing mud breccias representing the seafloor product of an ancient seepage site and 2 lucina free concretions originating below the sediment water interface within this group two subtypes have been further distinguished stratiform concretions and cylindrical concretions stratiform concretions result from precipitation of dolomite in the pores of muddy sediments some of them display a brecciated structure others show a network of septarian like cracks that are empty filled with sediments or zoned carbonate cements their internal features are related to the formation of gas hydrates within the sediments and to their destabilization thus these rocks mark a portion of the sedimentary column located within a paleo gas hydrate stability zone cylindrical concretions represent ancient fluid conduits related to the upward migration of ch 4 rich fluids subsequent to gas hydrate destabilization the carbonate rich rocks of the tertiary piedmont basin stand as one of the first examples of methane derived rocks that record successive episodes of dissociation and re formation of gas hydrates and they provide precious elements to model the general evolution of a portion of the sedimentary column located within the hydrate stability zone

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

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

evidence for archaeal methanogenesis within veins at the onshore serpentinite hosted chimaera seeps turkey abstract serpentinite hosted ecosystems are potential sites where life may first have evolved on earth serpentinization reactions produce strongly reducing and highly alkaline fluids that are typified by high concentrations of molecular hydrogen h2 and methane ch4 which can be used as an energy source by chemosynthetic life low temperature serpentinization at slow spreading mid ocean ridges provides an ideal environment for rich microbial communities similar environments have also been discovered on land where present day low temperature serpentinization occurs during the circulation of groundwater through exposed ophiolites triggering the production of ch4 and h2 as well as the precipitation of secondary carbonate minerals the rock samples analyzed here are from the chimaera seeps in turkey representing serpentinized peridotites that are cross cut by veins composed of brucite and hydromagnesite hydromagnesite features a mean 13c value of 19 8 caused by kinetic isotope fractionation during air groundwater exchange of co2 followed by co2 hydroxylation to bicarbonate within the groundwater geochemical modeling revealed that mixing of mg and ca rich groundwaters is required for hydromagnesite formation at the expense of brucite within the carbonate hydroxide veins the lipid biomarkers pentamethylicosane pmi and squalane with 13c values of 10 and 14 respectively and unsaturated derivatives thereof were identified archaeol sn2 hydroxyarchaeol and sn3 hydroxyarchaeol are other prominent archaeal biomarkers in the veins also revealing high 13c values from 6 to 13 these isotope patterns combined with the absence of crocetane a biomarker for methanotrophic archaea reveal that the microbial communities of the chimaera seeps performed methanogenesis from a co2 limited pool rather than methanotrophy moreover bacterial dialkyl glycerol diethers dages with unusually high 13c values 9 to 2 and minor monoalkyl glycerol monoethers mages were identified suggesting that bacterial sulfate reduction is also active at the chimaera site this study reveals that archaeal methanogenesis and bacterial sulfate reduction may be prominent at onshore peridotite hosted sites and that biogenic ch4 may contribute to abiotic ch4 emissions from terrestrial seeps

rare earth elements in seep carbonates as tracers of variable redox conditions at ancient hydrocarbon seeps marine hydrocarbon seeps are dynamic systems which are typically reflected in complex lithologies of limestones forming at these sites in order to test if seep limestones with their multiple generations of carbonate phases reflect variable redox conditions the rare earth element ree patterns of limestones from five ancient hydrocarbon seep localities hollard mound middle devonian iberg mississippian beauvoisin oxfordian canyon and satsop river oligocene and marmorito miocene have been investigated the total ree contents vary widely 0 3 43 7 p p m early microcrystalline phases tend to show higher contents than spatially associated later phases microspar sparite and blocky cement the shale normalized ree patterns of the carbonates show both negative and positive ce anomalies even for individual deposits suggesting that the redox conditions varied significantly it is apparent that in addition to anoxic conditions oxic conditions were common in some ancient seep environments intermittent oxygenation is presumed to have resulted from abrupt changes in fluid flow

greater contrast in martian hydrological history from more accurate estimates of paleodischarge correlative width discharge relationships from the missouri river basin are commonly used to estimate fluvial paleodischarge on mars however hydraulic geometry provides alternative and causal width discharge relationships derived from broader samples of channels including those in reduced gravity submarine environments comparison of these relationships implies that causal relationships from hydraulic geometry should yield more accurate and more precise discharge estimates our remote analysis of a martian terrestrial analog channel combined with in situ discharge data substantiates this implication applied to martian features these results imply paleodischarges of interior channels of noachian hesperian 3 7 ga valley networks have been underestimated by a factor of several whereas paleodischarges for smaller fluvial deposits of the late hesperian early amazonian 3 0 ga have been overestimated thus these new paleodischarges significantly magnify the contrast between early and late martian hydrologic activity width discharge relationships from hydraulic geometry represent validated tools for quantifying fluvial input near candidate landing sites of upcoming missions

methane seep brachiopod fauna within turbidites of the sinaia formation eastern carpathian mountains romania abstract this study elucidates the paleoecology and paleobiogeography of the early cretaceous brachiopod peregrinella known in museum collections from a few localities in romania supplemented with new material from a rediscovered locality first mentioned in the 1870s most peregrinella fossils are enclosed in mass waste deposits but at two sites authigenic limestones with assemblages of brachiopods preserved in life position have been recognized paleontological petrographic stable isotopic and organic geochemical investigations of these brachiopod bearing limestones from the upper sinaia formation eastern carpathian mountains romania confirm peregrinella as having lived at methane seeps in a siliciclastic dominated flysch basin the seeps developed on the slope of the external dacides basin the new collections of peregrinella indicate that shells derived from contemporaneous intrabasin methane seeps and were transported downslope by turbidity currents previous paleoecological models that consider peregrinella to be solely derived from transport downslope from shelf environments are questionable especially as peregrinella has never been recovered from typical shelf faunas in the instance documented here from the external dacides basin methane seep faunas with peregrinella are likely to be the origin of such allochthonous faunas the sinaia formation was deposited in a deep water marine basin derived from an intracontinental rift that developed during late jurassic early cretaceous extension the fractured and faulted basin margin provided the backdrop for the development of the methane seepage and the associated fauna foraminifera from background sediments in the sequence with turbidites confirm a late hauterivian to early barremian age for peregrinella within the sinaia formation this is significant because it indicates that peregrinella ranged through into the barremian whereas it has typically been considered to range only as high as the hauterivian

chemosynthetic communities as fingerprints of submarine sliding linked hydrocarbon seepage miocene deep sea strata of the tuscan romagna apennines italy abstract a specialised low diversity bivalve assemblage dominated by chemosymbiotic vesicomyid bivalves calyptogena sp is associated with a large submarine landslide casaglia m della colonna slide within the turbiditic miocene marnoso arenacea formation in the northern apennines this macrofossiliferous horizon is located just at the top of the slide close to the boundary between intrabasinal deformed sediments and extrabasinal sediments there is a causal relationship between the emplacement of this large submarine slide and fluid expulsion promoting the localised and ephemeral establishment of specialised communities the occurrence of exclusively sulphur based biota and the concomitant absence of 13c depleted authigenic carbonates from the host sediment are likely an indication that hydrocarbons within subsurface fluids were consumed through sulphate reduction processes as a result high levels of shallow seated h2s were produced and then exploited by chemosymbiotic bivalves

valleys in pit craters on mars characteristics distribution and formation mechanisms abstract new observations of central pit craters on mars reveal that some craters contain prominent interior valley networks that drain into their central pit in this study we catalog the distribution of pit craters with associated valleys and characterize in detail five diverse well preserved examples in some instances sedimentary deposits we interpret as either alluvial fans or deltas are found in the central pits and evidence suggests that at least some of these pits once contained lakes fluvial activity within the five pit craters we detail appears to have occurred relatively late in mars history during the hesperian or amazonian periods for this reason further understanding the formation mechanisms of these valleys has important implications for the history of water on mars

hydrocarbon seep carbonates of a miocene forearc east coast basin north island new zealand an ancient hydrocarbon seep province of 14 isolated authigenic carbonate deposits has been identified in fine grained deep marine siliciclastic strata of the miocene east coast basin north island new zealand these forearc sediments have been uplifted and complexly deformed into accretionary ridges adjacent to the still active hikurangi convergent margin older active and passive margin strata mid cretaceous to oligocene in age underlie the neogene sequence and contain oil and gas prone source rocks older mesozoic meta sedimentary rocks constitute the backstop against which the current phase of subduction related sedimentation has accumulated 24 ma present the seep carbonates up to 10 m thick 200 m across archive methane signatures in their depleted carbon isotopes to 13c 51 7 pdb and contain chemosynthesis based paleocommunities e g worm tubes bathymodioline mussels and vesicomyid lucinid and thyasirid bivalves typical of other cenozoic and modern seeps northern and southern sites are geographically separated and exhibit distinct lithological and faunal differences structural settings are variable seep associated lithologies also are varied and suggest carbonate development in sub seafloor seafloor and physically reworked diapiric expansion gas explosion gravity slide or debris flow settings similar to italian apennine seep deposits of overlapping ages peculiar attributes of the new zealand miocene seep deposits are several including digitate thrombolites of clotted microbial micrite encased in thick isopachous horizons and botryoids of aragonite seep plumbing features are also well exposed at some sites displaying probable gas explosion breccias filled with aragonite tubular concretions fluid conduits and carbonate cemented thin sandstone beds and burrows within otherwise impermeable mudstones a few seeps were large enough to develop talus debris piles on their flanks which were populated by lucinid bivalves and terebratulid brachiopods firmgrounds and hardgrounds were common as evidenced by trace fossil associations or caryophyllid coral thickets atop some seep carbonate deposits thus the new zealand examples show strong evidence of formation in sediments at or just beneath the seafloor but some were clearly exhumed by erosion to sustain later non seep epifaunal and boring paleocommunities

late hesperian to early amazonian midlatitude martian valleys evidence from newton and gorgonum basins 1 numerous shallowly incised valleys extend from the upper interior rims of newton and gorgonum basins across smooth interior basin deposits these valleys are a few meters to 300 m wide and may have experienced discharges over all or most of their width implying that they are in fact incised channels in newton crater these valleys extend up to 75 km to near the center of the basin floor in gorgonum basin the valleys terminate at what we interpret to be a former ice covered lake these valleys appear to be examples of scattered shallowly incised valleys found throughout the midlatitudes of mars superimposed upon the widespread mantling deposits within the region on the basis of crater count age dating the interior valleys in newton and gorgonum basins were formed at about the hesperian to amazonian transition the runoff through the valleys may have occurred due to episodic melting of snow and ice that had accumulated on the crater rims temperatures warm enough to cause extensive melting may have occurred during optimal orbital and obliquity configurations because of intensive volcanism releasing greenhouse gasses or as a result of a brief episode of warming from a large impact somewhere on mars the valleys were formed at about the same time as major outflow channels were active along the highlands lowlands boundary water delivered to the northern lowlands by the outflow channels may have been recycled as snow and ice deposits within the martian midlatitudes the episodic melting of such deposits may have formed the midlatitude valleys

fluvial sedimentary deposits on mars ancient deltas in a crater lake in the nili fossae region 1 new spacecraft observations in the nili fossae region of mars reveal two valley networks 80 and 200 km long that each formed distributary fans as they entered an ancient 40 km diameter impact crater an outlet channel on the eastern crater rim lying at an elevation above the fans suggests these fans formed as subaqueous deltas in a crater lake water flowing in the valley networks entered the crater and deposited the fans and ponded to a maximum depth of about 450 m the lake then overtopped and breached the crater rim incising it and dropping the lake level by 100 m geological evidence combined with the volume of water necessary to fill the crater suggests the duration of flow through this system was prolonged the existence of the deposits described here implies that the early martian environment supported overland flow and ponding of water for an extended period of time

seep deposits from northern istria croatia a first glimpse into the eocene seep fauna of the tethys region three isolated limestone deposits and their fauna are described from a middle eocene flysch succession in northwestern istria croatia the limestones are identified as ancient methane seep deposits based on fabrics and characteristic mineral phases 13 c carbonate values as low as 42 2 and 13 c depleted lipid biomarkers indicative of methane oxidizing archaea the faint bedding of the largest seep deposit the great dominance of authigenic micrite over early diagenetic fibrous cement as well as biomarker patterns indicate that seepage was diffusive rather than advective apart from methanotrophic archaea aerobic methanotrophic bacteria were present at the eocene seeps as revealed by 13 c depleted lanostanes and hopanoids the observed corrosion surfaces in the limestones probably reflect carbonate dissolution caused by aerobic methanotrophy the macrofauna consists mainly of chemosymbiotic bivalves such as solemyids acharax thyasirids thyasira and lucinids amanocina the middle eocene marks the rise of the modern seep fauna but so far the fossil record of seeps of this age is restricted to the north pacific region the taxa found at buje originated during the cretaceous period whereas taxa typical of the modern seep fauna such as bathymodiolin mussels and vesicomyid clams are absent although this is only a first palaeontological glimpse into the biogeography during the rise of the modern seep fauna it agrees with biogeographic investigations based on the modern vent fauna indicating that the dominant taxa of the modern seep fauna first appeared in the pacific ocean

on the instability and evolutionary age of deep sea chemosynthetic communities abstract though not directly dependent on photosynthesis deep sea chemosynthetic communities have not been sheltered from catastrophic changes affecting earth s photic zone instead the constituent animals may be particularly vulnerable to large climatic changes that have historically affected ocean temperatures and circulation patterns chemosynthetic animals occupy narrow redox zones mostly at hydrothermal vents hydrocarbon seeps or sites of organic deposition where subsurface fluids laden with reduced gases e g sulfides methane hydrogen meet oxygenated seawater dependence on chemolithoautotrophic bacteria as primary producers may render these deep sea communities particularly susceptible to climatic changes that alter the breadth of the oxic anoxic interface the fossil record clearly reveals major transitions of chemosynthetic faunas during the middle to late mesozoic failing to support prior hypotheses that these environments harbor an extraordinary number of ancient relics and living fossils the molecular phylogenetic analyses summarized herein support cenozoic

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

cold seep systems in the south china sea an overview abstract three decades after the discovery of cold seep systems various sites of hydrocarbon seepage have been found in the south china sea scs over the past decade these sites have become model systems for understanding the variability of hydrocarbon seepage and associated biogeochemical processes in this review we describe the cold seep systems of the scs with an emphasis on seafloor manifestations fluid sources biogeochemical processes and macroecology seafloor features associated with seeps include mud volcanoes pockmarks and carbonate deposits a common characteristic of cold seeps is the occurrence of authigenic i e in situ precipitated carbonate minerals these carbonates commonly exhibit low 13c and high 18o values suggesting the incorporation of methane derived carbon and oxygen derived from gas hydrate water biogeochemical processes such as sulfate driven anaerobic oxidation of methane sd aom the key process at seeps have been studied in detail with the aim of establishing geochemical proxies to trace these processes into the geological past we also detail the features characterizing seep ecosystems understanding the impact of decomposing methane hydrate on the marine carbon budget remains challenging and requires additional seafloor observations as well as models predicting how gas hydrate responds to changing conditions such as temperature increase sea level rise and episodic mass wasting

stable isotope evidence for chemosynthesis in an abyssal seep community communities of abundant organisms similar to those which surround the hydrothermal vents of the east pacific rise epr occur in 3 266 m of water in the gulf of mexico they were discovered with the alvin at 26 02 n 84 55 w in an area where pore waters seep from the cretaceous limestones of the adjacent platform at the contact between the florida escarpment and the holocene hemipelagic sediments of the abyssal gulf because of the unusual abundance of organisms in this deep sea environment and the taxonomic similarities to the chemosynthetically based communities which surround the hydrothermal vents on the epr the seep communities are suspected to exist on a local non photosynthetic food source1 we have now measured isotope ratios in tissues of organisms which surround these saline seeps to determine the origin of the local food chain the tissues have extremely negative 13c 42 to 77 pdb and 15n 2 72 to 9 34 air values such highly fractionated carbon and nitrogen isotopes are unknown in food chains based on photosynthesis suggesting that these communities are chemosynthetic the cause of this extreme fractionation is attributed either to assimilation from local supplies of isotopically depleted methane and ammonium or to biochemical fractionation the tissues of these animals contain significant amounts of 14c 60 modern so the source of this fractionated carbon is not predominantly fossil methane

lipid biomarker patterns reflect different formation environments of mussel and tubeworm dominated seep carbonates from the gulf of mexico atwater valley and green canyon abstract mussels and tubeworms thriving at many methane seeps typically live in symbiosis with chemosynthetic chiefly methanotrophic or thiotrophic bacteria it has been shown that the activities of chemosymbiotic animals can result in large differences in the sedimentary environments of their habitats here we put forward the concept that such environmental variability can be archived in the lipid biomarker inventories of authigenic carbonates forming in different locally confined environments at seeps mussel beds and tubeworm bushes in this case to test this hypothesis lipid biomarker patterns of carbonates from mussel and tubeworm environments from two seep sites atwater valley 340 and green canyon 852 of the gulf of mexico were analyzed previous work revealed stronger carbon isotope fractionation between the methane source and biomarkers of anaerobic methane oxidizing archaea 2 anme 2 sulfate reducing desulfosarcina desulfococcus dss consortia than for anme 1 dss consortia both performing anaerobic oxidation of methane aom similar 13cmethane values were found at the mussel and tubeworm sites from the same seeps and the local microbial consortia also appear to be largely similar based on the observed aom biomarker inventories yet a large average offset of 32 between the 13c values of molecular fossils of sulfate reducing bacteria srb involved in aom was observed with lower values typifying tubeworm carbonates than mussel carbonates this pattern is interpreted to reflect local effects on isotope fractionation caused by the chemosymbiotic metazoans at mussel and tubeworm dominated sites at tubeworm dominated sites the excess sulfate produced by thiotrophic symbionts of tubeworms and pumped down into the sediment results in persistent production of aom derived bicarbonate and the enrichment of 12c in sub surface sediments interestingly tubeworm carbonates also contain high amounts of non isoprenoidal dialkyl glycerol diethers dages with extreme 13c depletions representing compounds that derived from non dss cluster srb most likely 13c depleted aom derived organic intermediates were used as carbon sources by the dage producing non dss cluster srb possibly performing organoclastic sulfate reduction our study identifies significant variation in biomarker patterns between mussel and tubeworm carbonates at two seep sites in the gulf of mexico such variation allows to characterize different habitats at seeps which are shaped by the interaction of chemosymbiotic seep metazoans and their symbionts with the local environment metazoan community composition apparently controls geobiological interaction in seep ecosystems to a large degree which may allow tracing of the effects of chemosymbiosis into the rock record

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

corrosion patterns of seep carbonates from the eastern mediterranean sea terra nova 23 206 212 2011 abstract porous seep carbonates are exposed at mud volcanoes in the eastern mediterranean sea the 13c depleted aragonitic carbonates formed as a consequence of the anaerobic oxidation of methane in a shallow sub surface environment besides the macroscopically visible cavernous fabric extensive carbonate corrosion was revealed by detailed analysis after erosion of the background sediments the carbonates became exposed to oxygenated bottom waters that are periodically influenced by the release of methane and upward diffusion of hydrogen sulphide we suggest that carbonate corrosion resulted from acidity locally produced by aerobic oxidation of methane and hydrogen sulphide in the otherwise with respect to aragonite oversaturated bottom waters although it remains to be tested whether the mechanisms of carbonate dissolution suggested herein are valid this study reveals that a better estimate of the significance of corrosion is required to assess the amount of methane derived carbon that is permanently fixed in seep carbonates

hesperian age for western medusae fossae formation mars the medusae fossae formation mff on mars is an intensely eroded deposit north of the cratered highlands it is widely thought that mff materials were emplaced through ignimbrite eruptions recent geologic mapping of western mff identified outliers of mff materials well beyond the previously mapped western extent for the deposit including outliers close to gale crater we report counts of impact craters on the mff units that have implications for our understanding of the general history of mff and the uppermost layered materials on the gale crater mound

lipid biomarker patterns of authigenic carbonates reveal fluid composition and seepage intensity at haima cold seeps south china sea abstract authigenic carbonates retrieved from sites rov1 and rov2 of the haima hydrocarbon seeps of the south china sea at approximately 1390 m water depth were studied using lipid biomarker analyses abundant molecular fossils of anaerobic methane oxidizing archaea anme and sulfate reducing bacteria srb with strong 13c depletions 13c values as low as 126 in combination with low 13ccarbonate values 42 7 to 36 8 provide evidence that anaerobic oxidation of methane aom was the major process driving the precipitation of the studied seep carbonates the extremely low 13c values of archaeal biomarkers confirm that biogenic methane was the main carbon source but the seepage of accessory crude oil is also suggested by the presence of unresolved complex mixtures in the hydrocarbon fractions a suite of 13c depleted biomarkers indicate the predominance of anme 1 dss consortia at both sites which indicates that the studied carbonates formed during low to medium methane flux somewhat higher contents of archaeal biomarkers and their stronger 13c depletion at site rov2 probably reflect at least temporarily higher seepage intensities than at site rov1 abundant bacterial dialkyl glycerol diethers dages revealing a large offset of their 13c values compared to srb derived terminally branched fatty acids were possibly produced by distinct srb species other than members of the dss cluster the encountered hopanoids are attributed to aerobic methanotrophic bacteria based on their moderate 13c depletion the application of molecular fossils in combination with their compound specific isotope signatures is an efficient tool to reconstruct the composition of seepage fluids and seepage intensities

fluvial erosion and post erosional processes on titan the surface of titan has been revealed by cassini observations in the infrared and radar wavelength ranges as well as locally by the huygens lander instruments sand seas recently discovered lakes distinct landscapes and dendritic erosion patterns indicate dynamic surface processes this study focus on erosional and depositional features that can be used to constrain the amount of liquids involved in the erosional process as well as on the compositional characteristics of depositional areas fluvial erosion channels on titan as identified at the huygens landing site and in radar and visible and infrared mapping spectrometer vims observations have been compared to analogous channel widths on earth yielding average discharges of up to 1600 m3 s for short recurrence intervals that are sufficient to move centimeter sized sediment and significantly higher discharges for long intervals with respect to the associated drainage areas this roughly translates to 1 150 cm day runoff production rates with 10 years recurrence intervals and by assuming precipitation this implies 0 6 60 mm h rainfall rates thus the observed surface erosion fits with the methane convective storm models as well as with the rates needed to transport sediment during cassini s t20 fly by the vims observed an extremely eroded area at 30 w 7 s with resolutions of up to 500 m pixel that extends over thousands of square kilometers the spectral characteristics of this area change systematically reflecting continuous compositional and or particle size variations indicative of transported sediment settling out while flow capacities cease to account for the estimated runoff production and widespread alluvial deposits of fine grained material release of area dependent large fluid volumes are required only frequent storms with heavy rainfall or cryovolcanic induced melting can explain these erosional features

polyphasic carbonate precipitation in the shallow subsurface insights from microbially formed authigenic carbonate beds in upper miocene sediments of the tertiary piedmont basin nw italy article i nfo authigenic methane derived carbonates hosted in upper miocene slope sediments of the tertiary piedmont basin nw italy are studied by a multidisciplinary approach including petrography stable oxygen and car bon isotopes of carbonates as well as lipid biomarkers in order to explore the relationship between microbial activity and carbonate precipitation in the shallow subsurface the studied rocks show a bed parallel geom etry and are characterized by dolomitic intergranular cement which is typified by positive 13 c values as high as 6 2 vpdb a striking feature of some dolomite beds is an intricate network of septarian like cracks filled with both injected sediments and polyphasic carbonate cements prokaryotic molecular fossils in the dolomite beds comprise archaeol 13 c 40 vpdb and various bacterial dialkyl glycerol diethers dages 13 c 30 vpdb strongly suggesting that dolomite precipitation took place at the interface of the zones of archaeal methanogenesis and bacterial sulphate reduction in contrast extremely negative 13 c values of carbonate cements as low as 56 3 vpdb and various archaeal and bacterial molecular fossils e g pentamethylicosane pmi 106 vpdb are recorded in the crack filling carbonate cements these cements precipitated due to anaerobic oxidation of methane coupled to sulphate reduction we pro pose a scenario for the formation of the diagenetic beds suggesting that carbonate precipitation was the re sult of three microbially driven processes sulphate reduction methanogenesis and finally anaerobic oxidation of methane this unusual sequence was a consequence of a dynamic change of environmental geo chemical conditions and fluid circulation patterns that prevailed in the ancient subseafloor during early dia genesis of the unconsolidated sediments anaerobic oxidation of methane which usually predates methanogenesis during increasing burial postdates methanogenesis in case of the septarian like beds after the beds were affected by crack formation induced by overcritical pore pressure allowing the ingress of sulphate rich water from above and methane rich water from below

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

hydrocarbon seepage during the messinian salinity crisis in the tertiary piedmont basin nw italy abstract seep carbonate deposits of messinian age have been recently found in the tertiary piedmont basin nw italy these carbonates are preserved as blocks within a chaotic unit emplaced during the messinian salinity crisis msc they show negative 13 c values from 27 to 15 vpdb that indicate the involvement of hydrocarbon rich fluids in their genesis three types of carbonates are recognised i vuggy carbonates ii lucina carbonates and iii tubeworm carbonates vuggy carbonates are characterised by carbonate pseudomorphs after gypsum and probably formed during the first stage of the msc they are the product of a complex diagenesis influenced by both hypersalinity and seepage of hydrocarbon rich fluids these rocks lack chemosymbiotic assemblages reflecting their formation under extreme environmental conditions inhospitable for most metazoans in contrast lucina and tubeworm carbonates are characterised by chemosymbiotic macrofauna represented respectively by lucina bivalves and putative vestimentiferan tubeworms the latter have not commonly been documented in ancient seep carbonates and have never been reported from the messinian sediments of the piedmont basin both lucina and tubeworm carbonates are interpreted as the product of hydrocarbon seepage during the second msc stage these two types of carbonates formed under less severe conditions than the vuggy carbonates allowing the survival of seep dwelling metazoans during the second msc stage the seafloor was probably characterised by an irregular topography and a thin bottom layer of dense anoxic brines produced by the dissolution of gypsum it is suggested that vestimentiferan worms were able to thrive on morphologic highs with the posterior part of tubes just below the oxic anoxic interface but the anterior part projecting into oxic water the infaunal lucina bivalves were only able to live at seeps with an overlying oxic water column the studied carbonate deposits show features reflecting the uncommon interaction of hydrocarbon rich seep fluids and sulphate enriched waters the latter resulting from both evaporation and dissolution of gypsum and allow to reconstruct the evolution of a seepage system during the msc

stromatolitic fabric of authigenic carbonate crusts result of anaerobic methane oxidation at cold seeps in 4 850 m water depth methane seepage leads to mg calcite and aragonite precipitation at a depth of 4 850 m on the aleutian accretionary margin stromatolitic and oncoid growth structures imply encrustation of microorganisms microbial mats in the host sediment with a unique growth direction downward into the sediment forming crust shaped lithologies biomarker investigations of the residue after carbonate dissolution show strong enrichments in crocetane and archaeol which contain extremely low 13c values this indicates the presence of methane consuming archaea and 13c values of 42 to 51 pdb indicate that methane is the carbon source for the carbonate crusts thus it appears that stromatolitic encrustations of methanotrophic anaerobic archaea probably occurs in a consortium with sulphate reducing bacteria and that carbonate precipitation proceeds downward into the sediment where ascending cold fluids provide a methane source strontium and oxygen isotope analyses as well as 14c ages of the carbonates suggest that the fluids come from deep within the sediment and that carbonate precipitation began about 3 000 years ago

formation of seep carbonates along the makran convergent margin northern arabian sea and a molecular and isotopic approach to constrain the carbon isotopic composition of parent methane abstract authigenic carbonate deposits have been sampled with the remotely operated vehicle marum quest 4000 m from five methane seeps between 731 and 1823 m water depth along the convergent makran continental margin offshore pakistan northern arabian sea two seeps on the upper slope are located within the oxygen minimum zone omz ca 100 to 1100 m water depth the other sites are situated in oxygenated water below the omz below 1100 m water depth the carbonate deposits vary with regard to their spatial extent sedimentary fabrics and associated seep fauna within the omz carbonates are spatially restricted and associated with microbial mats whereas in the oxygenated zone below the omz extensive carbonate crusts are exposed on the seafloor with abundant metazoans bathymodiolin mussels tube worms galatheid crabs aragonite and mg calcite are the dominant carbonate minerals forming common early diagenetic microcrystalline cement and clotted to radial fibrous cement the 18 o carbonate values range from 1 3 to 4 2 v pdb indicating carbonate precipitation at ambient bottom water temperature in shallow sediment depth extremely low 13 c carbonate values as low 54 6 v pdb point to anaerobic oxidation of methane aom as trigger for carbonate precipitation with biogenic methane as dominant carbon source prevalence of biogenic methane in the seepage gas is corroborated by 13 c methane values ranging from 70 3 to 66 7 v pdb and also by back calculations considering 13 c methane values of carbonate and incorporated lipid biomarkers these calculations 13 c methane carbonate 13 c anme methane 13 c mox methane prove to be useful to assess the carbon stable isotope composition of seeping methane if this has not been determined in the first place such an approach represents a useful tool to reconstruct fluid composition of ancient seeps aom is also revealed by lipid biomarkers of anaerobic methane oxidizing archaea such as crocetane pentamethylicosane pmi and sn2 hydroxyarchaeol strongly depleted in 13 c 13 c values as low as 127 v pdb biomarkers of sulphate reducing bacteria are also abundant showing slightly less negative 13 c values but still significantly 13 c depleted average values as low as 101 other bacterial biomarkers such as bacteriohopanepolyols bhps hopanols and hopanoic acids are detected in most carbonates but are particularly common in seep carbonates from the non omz sites the bhp patterns of these carbonates and their low 13 c values resemble patterns of aerobic methanotrophic bacteria in the shallower omz sites bhps revealed much lower contents and varying compositions most likely reflecting other sources than aerobic methanotrophic bacteria 230 th u carbonate ages indicate that aom induced carbonate precipitation at the deeper non omz seeps occurred mainly during the late pleistocene holocene transition i e between 19 and 15 ka before present when the global sea level was lower than today

pervasive aqueous paleoflow features in the aeolis zephyria plana region mars abstract a survey of themis visible wavelength images in the aeolis zephyria plana region over the two western lobes of the equatorial medusae fossae formation mff shows 150 sinuous ridges having a variety of morphologies and contexts to systematize investigation we use a classification scheme including both individual ridge and ridge network types as well as associations with impact craters and fan shaped features the morphology of the ridges their location downslope from higher topography e g crater rims and scarps and their association with fan shaped forms indicate that most sinuous ridges formed through overland aqueous flow analysis of observations by individual ridge type leads to interpretation of most of these sinuous ridges as inverted fluvial channels or floodplains and a few as possible eskers with the origin of the remaining ridges under continuing investigation about 15 of the sinuous ridges are associated with impact craters but data analysis does not support a genetic relationship between the craters and the sinuous ridges instead analysis of one sinuous ridge network associated with a crater indicates that the water source for the network was atmospheric in origin namely precipitation runoff the broad areal distribution of these 150 ridges and the network morphologies in particular the branched and subparallel types suggest that an atmospheric water source is generally applicable to the population of sinuous ridges as a whole this concentration of sinuous ridges is the largest single population of such landforms on mars and among the youngest these ridges are situated at a paleoscarp between cerberus palus and the aeolis highlands suggesting that the precipitation that formed them was orographic in origin the ages of the equatorial mff units in which this population of sinuous ridges is found imply that this orographic rain and or snow fell during some period from the late hesperian through the middle amazonian

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

anatomy of seep carbonates ancient examples from the miocene of the northern apennines italy ancient hydrocarbon seep carbonates of miocene age have been reported from marine sedimentary successions of the northern apennines in the form of irregularly shaped micritic masses containing abundant fossil remains of oligotypic assemblages they are recognized by their peculiar biological sedimentological and geochemical features and represent an excellent on land example of carbonate bodies interpreted as the remains of ancient cold seeps in the apenninic chain the abundance and the extent of the outcrops provide a rare opportunity to study the geometry facies distribution and internal structures of fossil methane derived carbonates the present study reports an integrated view of the sedimentology mineral paragenesis and geochemistry of these seep carbonates in two different tectono sedimentary settings foredeep and satellite basins the main result of this study is the recognition of 17 facies in the investigated seepcarbonates the detailed facies and microfacies analysis led to the identification of different structures which occur in welldefined parts of the carbonate masses the recurring and broadly similar stratigraphy and facies association from the two considered geological environments is diagnostic of the different stages of seep carbonate formation and evolution d 2005 elsevier b v all rights reserved

hydrology of early mars valley network incision 1 widespread occurrences of valley networks on mars provide geomorphic evidence for an active hydrologic cycle to constrain the climatic conditions capable of forming the valley networks a hydrological model was used to analyze the valley incision depth and volume of eroded valleys because the absolute magnitudes of precipitation runoff and evaporation are uncertain we have used the ratio of these quantities the x ratio to express climatic conditions the spatial distribution and strength of the correlations between 1 the estimated depth and volume of eroded material and 2 estimated flood magnitude and valley gradients were investigated as a function of the assumed x ratio we also conducted an analysis of conditions required to have appreciable discharge in selected valley networks which provided the most definitive constraint on martian paleoclimate the other methods show a relatively weak dependency of incision depths and volumes upon the assumed x ratio the multiple regression analyses indicate that incision depth is strongly influenced by gradient and weakly related to modeled flood discharge the factors determining relative depth of incision depend partly on the type of channel bed however postflow modification of the valley networks by mass wasting cratering aeolian infilling and ice related processes precludes direct determination of bed morphology our hydrological analyses suggest that climatic conditions on early mars were at least as moist as those that occurred in the great basin region of the u s when large lakes were present during the pleistocene in terms of the balance of runoff and lake evaporation

3d morphology and timing of the giant fossil pockmark of beauvoisin se basin of france in the se basin of france drome fossil cold seep structures made of fossil rich carbonate lenses were identified in the oxfordian late jurassic terres noires formation about 30 years ago to date all seep sites have generally been studied individually without consideration of any link to neighboring or more distant sites based on a detailed fieldwork in the beauvoisin area and comparison with the modern active giant regab pockmark and sandbox experiments we suggest that this site can now be considered as a 800 m wide fossil analogue of a giant pockmark it comprises several 4 6 m deep 80 120 m wide coalesced sub seep sites a spatio temporal 3d reconstruction of the position of these sub sites shows that the carbonate lenses are organized in clusters with only one cluster active at a given period two periods of seep activity are separated by a period of quiescence due to the lateral shift of the feeder conduit beneath the structure this suggests that even if a seafloor pockmark appears to be inactive this could be due to the lateral shift of the feeder conduit meaning that the sub seafloor is still charged in gas

inverted fluvial features in the aeolis zephyria plana region mars formation mechanism and initial paleodischarge estimates 1 a subset of the sinuous ridges srs in the aeolis zephyria plana azp region of mars has been previously hypothesized to be inverted fluvial features although the precise induration and erosion mechanisms were not specified morphological observations and thermal inertia data presented here support this hypothesis a variety of mechanisms can cause inversion and identification of the specific events that lead to fluvial sr formation can provide insights into the sedimentological geochemical and climatic processes of the region reconnaissance of two terrestrial lava capped ridges suggests some criteria that may be used to identify inverted fluvial features formed by lava infill on mars but these criteria are not satisfied by the majority of the azp fluvial srs armoring also appears inconsistent with terrestrial analogs layering and surface textures of fluvial srs indicate that the most likely induration mechanism was geochemical cementation of fluvial sediments and that the primary erosional mechanism that exposed the fluvial srs was aeolian abrasion this analysis of formation mechanism provides a foundation for estimating paleodischarge using an empirical form discharge approach to which we have applied scaling for martian gravity for those fluvial srs meeting a set of criteria for accurate paleodischarge estimates paleodischarge values generally range between 101 and 103 m3 s 1 the largest of these initial estimates are comparable to paleodischarge estimates for some late stage noachian fluvial channels on mars and provide a constraint on the atmospheric conditions at this equatorial location during the late hesperian to early amazonian time frame

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

downstream variations in the width of bedrock channels field surveys of channel width w and drainage area a in bedrock channel reaches reveal relationships where w 5 ca b similar to the classic hydraulic geometry of alluvial channels data from five mountain channel networks support the assumption used in many landscape evolution models that an alluvial hydraulic geometry relationship where b 5 0 3 0 5 holds for bedrock channel systems although there is substantial local variability in channel width in bedrock channel systems there is no systematic difference in width versus drainage area relations for the surveyed bedrock and alluvial reaches in sedimentary lithologies in coastal oregon and washington in contrast bedrock channels were narrower and therefore had deeper flow than alluvial channels with equal drainage areas in the granite and limestone terrain of the yuba river california in addition data from the mokelumne river show that bedrock channel width decreases substantially downstream at the contact between relatively weak limestone and more erosion resistant granite but that channel slope does not change appreciably across contacts between these two lithologies data from coastal oregon drainage basins further show systematic channel widening after flood flows and debris flow impacts we conclude that downstream variations in the width of bedrock channels generally follow traditional hydraulic geometry relations but also reflect the local influence of longitudinal patterns of bedrock erosivity and disturbance history

on the latitudinal changes in ionospheric electrodynamics and composition based on observations over the 76 77 e meridian from both hemispheres during a geomagnetic storm the relative contributions of the composition disturbances and the disturbance electric fields in the redistribution of ionospheric plasma is investigated in detail by taking the case of a long duration positive ionospheric storm that occurred during 18 21 february 2014 gps total electron content tec data from the indian antarctic station bharti 69 4 s 76 2 e geographic the northern midlatitude station hanle 32 8 n 78 9 e geographic northern low latitude station lying in the vicinity of the anomaly crest ahmedabad 23 04 n 72 54 e geographic dip latitude 17 n and the geomagnetic equatorial station trivandrum 8 5 n 77 e geographic dip latitude 0 01 s are used in the study these are the first simultaneous observations of tec from bharti and hanle during a geomagnetic storm the impact of the intense geomagnetic storm dst 130 nt on the southern hemisphere high latitude station was a drastic reduction in the tec negative ionospheric storm starting from around 0330 indian standard time ist on 19 february which continued till 21 february the maximum reduction in tec at bharti being 35 tec units on 19 february in the northern hemisphere midlatitude and equatorial stations a positive ionospheric storm started on 19 february at around 0900 ist and lasted for 3 days the maximum enhancement in tec at hanle was about 25 tecu on 19 february while over trivandrum it was 10 tecu this long duration positive ionospheric storm provided an opportunity to assess the relative contributions of disturbance electric fields and composition changes latitudinally the results indicate that the negative ionospheric storm over bharti and the positive ionospheric storm over hanle are the effect of the changes in the global wind system and the storm induced composition changes at the equatorial latitudes the positive ionospheric storm was due to the interplay of prompt penetration electric field and disturbance dynamo electric field

aerobic methanotrophy at ancient marine methane seeps a synthesis abstract the molecular fingerprints of the chemosynthesis based microbial communities at methane seeps tend to be extremely well preserved in authigenic carbonates the key process at seeps is the anaerobic oxidation of methane aom which is performed by consortia of methanotrophic archaea and sulphate reducing bacteria besides the occurrence of 13 c depleted isoprenoids and n alkyl chains derived from methanotrophic archaea and sulphate reducing bacteria respectively 13 c depleted triterpenoids have been reported from a number of seep deposits in order to evaluate the significance of these apparently non aom related molecular fossils the biomarker inventories of one campanian and two miocene methane seep limestones are compared these examples provide strong evidence that methane was not solely oxidized by an anaerobic process structural and carbon isotope data reveal that aerobic methanotrophy was common at some ancient methane seeps as well the miocene marmorito limestone contains abundant 3 methylated hopanoids 13 c 100 most likely 3 methylated hopanepolyols prevailing in aerobic methanotrophs were the precursor lipids of these compounds a series of isotopically depleted 4 methylated steranes lanostanes 13 c 80 to 70 and similarly isotopically depleted 17 h 21 h 32 hopanoic acid in the miocene pietralunga seep limestone also are derived probably from aerobic methanotrophs lanosterol which is known to be produced by aerobic methanotrophs is the most likely precursor of 4 methylated steranes less obvious is the origin of 8 14 secohexahydrobenzohopanes 13 c 110 to 107 in late cretaceous seep limestones these hopanoids probably reflect early degradational products of precursor lipids locally produced by seep endemic aerobic methanotrophs

evaluation of paleohydrologic models for terrestrial inverted channels implications for application to martian sinuous ridges abstract fluvial systems can be preserved in inverted relief on both earth and mars few studies have evaluated the applicability of various paleohydrological models to inverted fluvial systems the first phase of this investigation focused on an extensive spanning 12 km inverted paleochannel system that consists of four sandstone capped carbonate cemented sinuous ridges within the early cretaceous cedar mountain formation located southwest of green river utah morphologic and sedimentologic observations of the exhumed paleochannels were used to evaluate multiple numerical models for reconstructing paleofluvial hydrological parameters another objective of the study was to determine whether aerial or orbital observations yield model results that are consistent with those constrained by field data the models yield an envelope of plausible dominant discharge values 100 500 m 3 s reflecting the limitations of the approach and no single model can be used to reliably estimate paleodischarge on mars landforms with attributes consistent with inverted channels have been identified in spite of differences in the formation history between these martian landforms and the terrestrial analog described here including potential differences in cement composition and the erosional agent that was responsible for relief inversion these numerical models can be applied with modification to the martian landforms and yield an envelope of plausible values for dominant discharge