microbial sulfate reduction in deep sea sediments at the guaymas basin hydrothermal vent area influence of temperature and substrates abstract microbial sulfate reduction was studied by a 35 s tracer technique in sediments from the hydrothermal vent site in guaymas basin gulf of california mexico in situ temperatures ranged from 2 7 c in the overlying seawater to 120 c at 30 cm depth in the hydrothermal sediment sulfate reduction was measured in intact cores of hydrothermal sediment at 3 20 35 50 70 and 90 c the maximum rates of sulfate reduction were found in the upper 0 2 cm of the sediment and ranged from 32 nmol cm 3 d 1 at 90 c to 1563 nmol cm 3 d 1 at 70 c the rates of sulfate reduction rapidly decreased with depth in the upper 0 10 cm of the sediment and the maximal depth integrated rate 0 10 cm was 70 3 mmol so 4 2 m 2 d 1 at 70 c in comparison the sulfate reduction rate in nonhydrothermal sediment from the vent area was 0 85 mmol m 2 d 1 at the in situ temperature of about 3 c the high subsurface rates of sulfate reduction in the hydrothermal vent area was attributed to an enhanced local substrate availability in slurries of hydrothermal sediment incubated at 10 120 c microbial sulfate reduction extended to 102 c and different temperature groups of microbial sulfate reducers had optimum temperatures at around 34 70 and 80 88 c the overall temperature response of thermophilic sulfate reduction was similar in hydrothermal sediment sampled at different sites addition of short chain fatty acids and yeast extract to the sediment slurries stimulated sulfate reduction rates at all incubation temperatures no sulfate reduction was detected in the temperature range from 102 120 c microbial rather than thermochemical sulfate reduction could be a possible source of h 2 s in sulfide deposits with formation temperatures at about 100 c

low temperature hydrothermal maturation of organic matter in sediments from the atlantis ii deep red sea abstract hydrocarbons and bulk organic matter of two sediment cores no 84 and 126 chain 61 cruise located within the atlantis ii deep have been analyzed although the brines overlying the coring areas were reported to be sterile microbial inputs and minor terrestrial sources represent the major sedimentary organic material this input is derived from the upper water column above the brines both steroid and triterpenoid hydrocarbons show that extensive acid catalyzed reactions are occurring in the sediments in comparison with other hydrothermal guaymas basin or intrusive systems cape verde rise the atlantis ii deep exhibits a lower degree of thermal maturation this is easily deduced from the elemental composition of the kerogens and the absence of polynuclear aromatic hydrocarbons of a pyrolytic origin in the bitumen the lack of carbon number preference among the n alkanes suggests especially in the case of the long chain homologs that the organic matter of atlantis ii deep sediments has undergone some degree of catagenesis however the yields of hydrocarbons are much lower than those observed in other hydrothermal areas the effect of lower temperature and poor source rock characteristics appear to be responsible for the differences

first evidence of benthic communities based on chemosynthesis on the napoli mud volcano eastern mediterranean abstract some molluscan valves attributed to myrtea sp lucinidae vesicomya sp and another undetermined vesicomydae were sampled in 1993 cruise ttr3 leg2 and 1994 cruise um94 by coring on the top of the napoli dome a mud volcano located on the mediterranean ridge at about 1900 m of water depth these bivalves belong to an unknown apparently rich benthic community associated to the sulphides and methane rich emissions that characterize the napoli dome outside the mediterranean deep sea lucinidae and vesicomyidae are associated with cold seeps and hydrothermal vents and are known to be sustained by bacterial chemosynthetic activity based on sulphide and or methane oxidation the same explanation is given for this newly discovered deep mediterranean fauna firstly described here

sedimentary geochemistry of hydrothermal vents in guaymas basin gulf of california mexico abstract surface sediments from 4 contrasting environmental settings in the southern trough of guaymas basin were analysed to determine their texture total organic matter tom p tp and n tn content as well as the spatial variation in their c n p atomic ratios in hydrothermally altered sediments particle size analysis revealed a marked spatial heterogeneity among sites cores taken at beggiatoa bacterial mats and at clam fields contained significant silt and clay content while those obtained near venting sites had sand and gravel as the main components because no fine sedimentary materials are deposited at these sites fine grain sediments were common farther away from vents high levels of organic c 3 4 to 12 4 were recorded in the upper 8 cm but no clear trends of decreasing toc with depth were noted the presence of hydrothermally generated petroleum in some cores increased the organic c content between 8 and 12 cm tn was generally high 456 3 4356 g g and sustained a significant correlation with tom r 0 834 p beggiatoa or vesicomyd clams are predominant

vent type taxa in a hydrocarbon seep region on the louisiana slope recent discoveries on the northern gulf of mexico continental slope have altered our understanding of biological and chemical processes occurring in the deep ocean a biological community of hydrothermal vent type organisms was recently discovered at the base of the florida escarpment1 where the fauna are apparently nourished by hydrogen sulphide rich hypersaline water seeping out onto the sea floor dense colonies of deep living chemosynthetic benthic organisms were first discovered during investigations of warm water anomalies along the axis of the galapagos rift in the pacific ocean in 19772 4 and this first discovery of clusters of clams tube worms and other filter feeders in the immediate proximity of warm water vents has been followed by the discovery of a number of other hydrothermal vent sites for example guaymas basin east pacific rise at 21 n the dense population assemblages at these sites are apparently restricted to small areas of the ocean floor where hydrogen sulphide rich water is escaping from spreading centres but the florida escarpment discovery indicates that these communities can also exist on passive margins here we report the discovery of dense biological communities associated with regions of oil and gas seepage on the louisiana continental slope these communities of large epi and infaunal organisms are similar to those associated with the vents of the pacific and the hypersaline brine seeps of the florida escarpment carbon isotope analyses suggest that these communities are chemosynthetic and derive their energy from hydrogen sulphide and or hydrocarbons similar communities may be widely distributed on the sea floor in other oil producing regions of the ocean

high molecular weight polycyclic aromatic hydrocarbons in hydrothermal petroleums from the gulf of california and northeast pacific ocean hydrothermal petroleums and heavy tars have been analyzed for polycyclic aromatic hydrocarbons pah with molecular weights greater than that of coronene 300 da samples from the hydrothermal systems in the guaymas basin gulf of california and in the escanaba trough and middle valley northeastern pacific were analyzed by gas chromatography mass spectrometry and high pressure liquid chromatography with diode array absorbance detection mass spectra and fluorescence spectra were used to characterize the compounds several large pahs with six and more rings were identified among the heavy pah production routes via one ring build up and scholl condensation are proposed to explain the observed structures the variations in pah concentrations and distributions between samples from different locales are a consequence of the hydrothermal conditions of generation migration and post depositional alteration

measurements of winds on mars with hubble space telescope images in 2003 opposition the winds of mars at the water cloud level are measured by tracking cloud features in sequential high resolution hubble space telescope uv images for 5 days during the perihelion season in 2003 global circulation model gcm predictions are in general agreement with the observations for the zonal wind component but reveal significant differences for the meridional component

deep biological communities in the subduction zone of japan from bottom photographs taken during nautile dives in the kaiko project abstract twenty seven dives of the submersible nautile in the subduction zone around japan conducted in the french japanese project kaiko proved that fairly luxuriant benthic communities dominated by deep sea giant clams of the genus calyptogena family vesicomyidae were consistently present on the accretionary prism at abyssal depths benthic communities characterized by three hitherto undescribed bivalves of the genus calyptogena were found between depths of about 3800 and 4020 m at the mouth of tenryu canyon and at the top of basement swell of the zenisu ridge both situated in the eastern nankai subduction zone sporadic but discrete patches of organisms characterized by one more undescribed bivalve belonging to the genus calyptogena were observed and collected between depths of 5130 and 5960 m on the landward wall of the japan and kouriles trenches photographic inventories were prepared semiquantitatively using each series of bottom photographs taken in these areas with bow cameras of the submersible nautile observations on the sporadic but dense distribution of the clams and other characteristic associated organisms match well with the scheme that communities sustained by chemosynthetic energy sources can be present at connate water seepages in subduction zones these are to date the deepest record of benthic communities supposedly associated with chemosynthetic processes

crustal processes at spreading centers recent discoveries and research on mid ocean ridges mor s in the last four years have greatly increased our knowledge of this fundamental type of plate boundary the last iugg review of mor research was in 1975 aumento et al 1975 and its omission as a topic in 1978 may have reflected a feeling that spreading centers were reasonably well understood since that time however there has been a surfeit of important new observations and exciting research and there is now a turmoil of innovative ideas about the processes which create and leave their imprint on two thirds of the earth s crust new seismic measurements have been made and interpreted as evidence for the existence of shallow axial magma chambers amc beneath intermediate total opening rate 5 9 cm yr and fast 9 18 cm yr spreading centers fig 1 yet there is controversy as to whether they are steady state whether they persist beneath slow ridges as well in the steady state what the dimensions and shape of the chamber are its relation to oceanic crustal stratigraphy and its relation to observations in ophiolites black smoker hydrothermal vents have been discovered in the pacific spewing forth 350 c fluids blackened by polymetallic sulfide precipitates this discovery is embroiled in debate as to how long the vents last whether they occur at slow spreading rates as well whether the enormous heat flux of the vents freeze the magma chamber even at fast spreading rates their influence on geochemical balances in the ocean and the value of the sulfide deposits commercially it has been found that our initial view of mor s as two dimensional linear structures has served us well as an initial working model but must be significantly modified to account for variations in tectonic volcanic and hydrothermal activity along strike as well as for episodicity of these processes deep sea drilling project dsdp samples have raised fundamental questions about formation of the magnetic source layer hydrothermal circulation and fault mechanisms along the mor spreading centers which penetrate existing lithosphere along strike as propagating rifts have modified our views of how plate boundaries reorient themselves and how v shaped magnetic and topographic trends are formed we have also found that transform faults may modify spreading center processes for some distance away from their intersections with mor s and that rigid plate transform faults may fail to develop at fast spreading centers under certain conditions resulting in en echelon overlapping of spreading centers this review will focus on these developments and several others only example references to these topics will be given in the text and many important topics will not be discussed directly e g petrology and geochemistry mantle convection research on lithosphere older than 1 m y however i have tried to compile and have included an extensive bibliography for u s research on a broader range of mor topics for mid 1978 to mid 1982 which is the main purpose of this report pre 1978 references are occasionally included where appropriate abstracts are not included

petroleum generation an easy and widespread process in hydrothermal systems an overview abstract the conversion of organic matter to petroleum products by hydrothermal activity is an easy process occurring in nature in many types of environments geologically immature organic matter of marine sediments has been shown to be altered to petroleum products by this process in the guaymas basin escanaba trough bransfield strait and atlantis ii deep and this process probably occurs elsewhere in active sedimented rift systems contemporary organic detritus and or viable microorganisms are also converted in part to petroleum like products when they become entrained by turbulent mixing into hydrothermal vent waters resulting in their instantaneous hydrous pyrolysis this latter case occurs in hydrothermal vent fields without a sedimentary cover emanating directly from oceanic ridges as for example on the east pacific rise at 13 n and 21 n and on the mid atlantic ridge at 26 n this process is probably also ubiquitous for all actively venting sediment starved oceanic ridges the hydrocarbon products generated in these areas have been compared in terms of composition organic matter sources and analogy to reservoir petroleum they represent a major carbon source for chemosynthetic assimilation by vent biota and are compositionally similar to normal petroleum

evaporation effects on the formation of martian gullies abstract in order to investigate the formation of martian gullies and the stability of fluids on mars we examined about 120 gully images twelve hirise images contained a sufficient number of transverse aeolian ridges tars associated with the gullies to make the following measurements overall gully length length of the alcove channel and apron and we also measured the frequency of nearby tars six of the 12 images examined showed a statistically significant negative correlation between overall gully length alcove channel and apron length and tar frequency previous experimental work from our group has shown that at temperatures below 200 k evaporation rate increases by about an order of magnitude as wind speed increases from 0 to 15 m s thus the negative correlations we observe between gully length and dune frequency can be explained by formation at temperatures below 200 k where wind speed evaporation is a factor governing gully length in these cases evaporation of the fluid carving the gully was a constraint on their dimensions cases where there is no correlation between gully length and tar frequency can be explained by formation at temperatures 200 k the temperatures are consistent with global circulation model and thermal emission spectrometer tes data for these latitudes the temperatures suggested by these trends are consistent with the fluid responsible for gully formation being a strong brine such as fe 2 so 4 3 which has a eutectic temperature of 200 k we also find that formation timescales for gullies are 10 5 10 6 years

spatial distribution of diverse cold seep communities living on various diapiric structures of the southern barbados prism three sectors of the south barbados prism between 1000 and 2000 m depth were explored by the french submersible nautile chemosynthesis based benthic communities were discovered on several structures affected by diapirism including mud volcanoes domes and an anticlinal ridge the communities are associated with the expulsion of methane rich fluids which is a wide spread process in the area these communities are dominated by large bivalves and vestimentiferans which harbour chemoautotrophic symbiotic bacteria the symbiotic bivalves include two species of mytilidae and one of vesicomyidae with dominance of a methanotrophic mussel cartography of the benthic communities interpretation of thermal measurements and observation of sedimentary patterns have been used to define the life habits of each of the three species of symbiotic bivalves each species has a characteristic preference for different conditions of edaphic and fluid flow the dominant methanotrophic mussel appears to require high velocity vents and hard substratum the vesicomyids and the other species of mussel are able to take up sulfide from the sediments and so are associated with low seepages but also require soft sediment the three bivalve species are assumed successively to colonize the top of a diapiric ridge in a succession related to the temporal evolution of fluid flow and sedimentation the composition of the bivalve assemblages their densities and biomasses all differ between the several mud volcanoes and domes studied and these parameters are thought to be related to the spatial and temporal variations of fluid expulsion through the structures and the lithification processes linked to fluid expulsion one very active dome is at present colonized by an exceptionally large and dense population of the methanotrophic mussel in contrast communities in another area on the domes and volcanoes that are currently inactive were colonized by only a few living vesicomyids and mussels both associated with sulfur oxydizing bacteria and there were numerous empty shells the densities and biomasses of symbiotic bivalves were far greater in the area studied than in a deeper mud volcano field on the same prism that had been studied previously this is consistent with a report that methane production is greater in the southern region of this accretionary prism than in the northern numerous non symbiotic organisms were observed in and around the areas of the seeps some are endemic to the seep communities including some gastropods and shrimps others are either colonists or vagrants from the surrounding deep sea floor filter feeders were very abundant and some of these like the serpulids and large sponges may also be dependent on the chemosynthetic production faunistic composition of both symbiotic and non symbiotic taxa of the assemblages around these cold seeps is closely related to that reported for communities living on hydrocarbon seeps in the gulf of mexico

seafloor facies related to upward methane flux within a giant pockmark of the lower congo basin the origin of the cold fluid venting from a giant pockmark within the lower congo basin has been elucidated based upon results of precise mapping submersible dives gravity coring and isotopic analyses realized under a total ifremer cooperative project zaiango and biozaire projects during four dives of the ifremer rov victor 6000 the bottom was filmed hard and soft samples were lifted from the sediment and water samples were collected with a ctd rosette system the detailed dip map shows that the 800 m wide giant pockmark is a composite feature due to the coalescence of multiple 100 m wide depressions that displays a broad range of biological mineralogical and chemical features on the seafloor leading to a seafloor anomaly recorded on the multibeam imagery methane rich fluids migrating through the sedimentary column from a buried palaeochannel clearly react with the sulphate rich circulating sea water to produce hydrogen sulphide and bicarbonate ions this situation leads to a concentrical arrangement of the sedimentary facies with methane related features in the centre and sulphide related features at the periphery this organization is correlated with high levels of methane up to 20 mol l measured in the centre of the giant pockmark responsible for the crystallization of gas hydrates at the bottom in this model the concentrical organization of mineralogical and biological features reflects a geochemical partitioning related to the peripheral progressive mixing of the methane flux

deep water hydrocarbon seeps in guaymas basin gulf of california abstract acoustically discovered hydrocarbon seeps along a transform fault zone on the sonoran margin of guaymas basin and in the southern trough of guaymas basin were examined and sampled during dives of dsv alvin seepage of methane and heavier hydrocarbons occurs through shallow pockmarks along the eroding crest of a steep anticline 1600 m below sea level extensive ledges of aragonite crop out around the rims of the pockmarks isotopic analysis indicates that carbonate precipitation is a result of methane oxidation seepage zones within the pockmarks support dense communities of calyptogena half buried in the mud tubeworms lamellibracheae sp have colonized many of the aragonite outcrops though the margin site is only a few kilometers from a high temperature sulfide precipitating and petroleum discharging vent system at a nearby center its structural setting is more akin to pockmarks described from continental shelves and its chemosynthetic fauna is more like that around low temperature seeps on other continental slopes and margins e g oregon u s a and japan the seep in the southern trough is a condensate type petroleum c 1 c 40 and rises as a plume from a young vent mound system about 2000 m below sea level

evidence from fluid seeps atop serpentine seamounts in the mariana forearc clues for emplacement of the seamounts and their relationship to forearc tectonics abstract the mariana forearc is a non accretionary forearc with numerous seamounts dredge hauls from these seamounts are composed primarily of serpentinite indicating a non volcanic origin in addition dredged carbonate samples reveal 1 the presence of aragonite in water depths greater than the aragonite compensation depth 2 unusual porosity and cement types 3 light carbon and heavy oxygen isotopic compositions and 4 an unusual trace element geochemistry of aragonite and calcite these mineralogic petrologic and geochemical characteristics formed the basis of a prediction that methane bearing fluids are venting from these seamounts subsequent to this prediction submersible dives on a mariana forearc seamount found and sampled chimneys seeping cool water that contains dissolved methane the serpentine substrate beneath the chimneys appears to form from cold gravitational flows of serpentine material fluid inclusion contents of chimney samples also show an earlier history of methane as well as longer chain hydrocarbons aromatics and acetate ions drilling into the flank and the summit of this seamount by the ocean drilling program during leg 125 confirmed the presence of methane other light alkanes and organic acids in the present day interstitial pore fluid of the cores the presence of aromatic compounds and organic acids if derived from the maturation of organic compounds indicates a thermogenic origin for these volatiles strontium isotopic ratios of the aragonitic chimney samples and of the present day interstitial waters range from present day seawater values to significantly lower values the strontium isotopic ratios of the pore waters within the seamount trend toward a relatively less radiogenic composition with increasing depth below the seafloor this strontium isotopic signature is probably not the consequence of near surface processes but more likely a contribution from an igneous source deeper in the lithosphere the lack of a large accretionary prism in the mariana forearc removes the complication of fluid contribution from dewatering of the prism by compression during convergence as in the oregon washington or barbados margins the organic compounds in the fluid inclusions and interstitial pore fluids as well as the isotopic and the geochemical composition of the carbonates and the dissolved constituents suggest that fluids are derived from dewatering compression and dehydration of subducted sediments and the subducting plate furthermore the composition of the fluid is influenced by thermal maturation of organics in subducted sediments as well as by a contribution from a deep igneous source

surficial evidence of fluid expulsion from the costa rica accretionary prism the nature and distribution of authigenic carbonates chemosynthetic bacterial mats and unique macrobenthic chemosynthetic communities of bivalves and tube worms are important for evaluating and reconstructing present and past fluid venting of accretionary complexes this paper describes the authigenic carbonates chemosynthetic fauna and fluid venting observed at the four tectonic regions of the costa rica accretionary wedge in february 1994 during an alvin diving program of 20 submersible dives we found no surficial evidence of highly focused fluid venting at the toe of the prism outermost 3 km as implied by the absence of authigenic carbonates and chemosynthetic fauna the absence of vent communities on the lower 3 km of the prism and the relatively elevated heat flow with respect to the adjacent incoming cocos plate langseth and silver this issue suggests diffuse rather than focused flow through the toe of the prism twelve active and relict vent sites marked by small clusters of live vesicomyid clams are localized at the bases and tops of out of sequence thrusts implicating fracture permeability as the fluid conduit in the lower slope region but upslope from the toe vast authigenic carbonates and seven active and relict vent sites marked by large dense clusters of chemosynthetic organisms predominate the largest mud diapir in the mid slope region fluid expulsion appears to be more restricted on the upper slope with only 2 small but dense vents marked by chemosynthetic fauna observed at one wall of one canyon

basal tuffs and contemporaneity of the chattisgarh and khariar basins based on new dates and geochemistry abstracttime bracketing of thousands of meters thick unmetamorphosed fossil free sedimentary successions is a long standing challenge in indian proterozoic stratigraphy limited geochronologic ages from either the basal or the upper part of the successions prevent workers from constraining the precise age interval for individual basin fill leaving aside the issue of correlatability between different basin sequences this article deals with silicic tuff units from the basal part of two areally separated proterozoic sedimentary successions of central india the singhora group of the chattisgarh supergroup and the khariar group the singhora tuff is enriched in large ion lithophile rb ba th etc elements and light rare earth elements and in a discrimination diagram falls within the volcanic arc granite field u th pb electron probe microanalyzer geochronology of monazite and zircon grains from the singhora tuff revealed several age data clusters namely 2500 2100 1800 1500 and 1000 ma in c

fault related biogenic mounds in the ceduna sub basin australia implications for hydrocarbon migration abstract the early cenozoic in the bight basin represents a transitional period from the slow to fast oceanic crust spreading of the southern ocean between australia and antarctica this period is characterised by widespread igneous activity and the occurrence of biogenic mound complexes in the proximal part of the ceduna sub basin these mound complexes thrive on local topographic highs exploiting the shut down in siliciclastic sediment supply during the eocene new interpretation of 2d and 3d seismic data from the central ceduna sub basin shows additional undrilled paleocene eocene biogenic mound complexes they display rugose morphology progradational and aggradational internal organisation and high impedance contrast with the surrounding sediments these mounds typically show a clear relationship with underlying reactivated fault segments these faults intersect potential oil mature cretaceous source rock intervals and therefore one plausible mechanism for the development of fault related mound complexes in the central ceduna sub basin relies on natural hydrocarbon seeps along faults supplying nutrients for a benthic chemosynthetic organisms and localised biogenic mound growth the presence of a sub bottom profile anomaly overlaid by a vertical water column acoustic contact in close vicinity of a mound complex support this model the occurrence of seep related biogenic mounds would validate the presence of mature source rock s and hydrocarbon charge in the central ceduna sub basin if confirmed the biogenic mounds would imply fluid migration occurrence until at least the eocene

a braided distributary system on the orinoco deep sea fan abstract a long range side scan sonar gloria survey has been made of part of the orinoco deep sea fan that abuts against the deformation front of the barbados outer ridge i e in a pre orogenic setting immediately east of the deformation front sinuous channels up to 65 m deep and 3 km wide extend downslope and become very shallow a few metres or less deep and branch into a pattern that resembles stream braiding near the foot of the slope here there is a possible suprafan lobe and an almost flat perched sediment pond dammed by a buried basement ridge in this locality many of the acoustic contrasts on the sonographs are primarily due to differences in sediment type and small scale roughness rather than to variations in slope angle possible debris flows aligned along some of the braided channels have been identified from high resolution profiles this braided system of shallow channels then converges into a single channel that overtops the dam because of their braided nature the internal structure of the resulting deposits is likely to be complex these deposits should eventually be incorporated into the barbados ridge complex in contrast to this pre orogenic setting gloria sonographs also suggest that some orinoco sediment moves down along synclinical axes of folds on the barbados ridge complex i e in a syn orogenic setting

improved general circulation models of the martian atmosphere from the surface to above 80 km we describe a set of two new generation general circulation models of the martian atmosphere derived from the models we originally developed in the early 1990s the two new models share the same physical parameterizations but use two complementary numerical methods to solve the atmospheric dynamic equations the vertical resolution near the surface has been refined and the vertical domain has been extended to above 80 km these changes are accompanied by the inclusion of state of the art parameterizations to better simulate the dynamical and physical processes near the surface boundary layer scheme subgrid scale topography parameterization etc and at high altitude gravity wave drag in addition radiative transfer calculations and the representation of polar processes have been significantly improved we present some examples of zonal mean fields from simulations using the model at several seasons one relatively novel aspect previously introduced by wilson 1997 is that around northern winter solstice the strong pole to pole diabatic forcing creates a quasi global angular momentum conserving hadley cell which has no terrestrial equivalent within such a cell the coriolis forces accelerate the winter meridional flow toward the pole and induce a strong warming of the middle polar atmosphere down to 25 km this winter polar warming had been observed but not properly modeled until recently in fact thermal inversions are generally predicted above one and often both poles around 60 70 km however the mars middle atmosphere above 40 km is found to be very model sensitive and thus difficult to simulate accurately in the absence of observations

hydrothermal petroleum in mineralized mounds at the seabed of guaymas basin petroleum has been dredged from an active hydrothermal mound area in the southern rift of guaymas basin gulf of california this organic matter is composed of gasoline range aliphatic and aromatic hydrocarbons and predominantly residual polar asphaltic material the aliphatic hydrocarbons of two bitumen samples have very different boiling range and composition both samples contain polynuclear aromatic hydrocarbons and olefins which indicate formation at pyrolytic temperatures the overall compositional data indicate an origin from biological detritus by thermal alteration and rapid quenching by hydrothermal removal followed by condensation at the seabed

oil source rock correlation of the lower paleozoic petroleum system in the baltic basin northern europe the correlation of lower paleozoic marine source rocks with reservoired oils by biomarkers is complex because of the uniform early phanerozoic biomass bacteria and algae and the lack of land plant and animal input accordingly the main source rocks for the most prolific oil province in the baltic basin are still a matter of debate the 10 source rocks and 15 oil samples from 5 northern european countries bordering the baltic sea basin were analyzed by gas chromatography gc with flame ionization detector gc mass spectrometry gcms and gcms ms to detect acyclic isoprenoids and aliphatic aromatic and nitrogen sulfur and oxygen biomarkers chemometric tools were applied to screen for meaningful source and age related biomarkers and to highlight genetics extended tricyclic terpane ratios c24 tetracyclic terpane c26 tricyclic terpane ratios and relative c29 sterane concentrations are considered the most promising biomarkers in differentiating llandovery shales from cambrian to ordovician alum shale and for correlation with expelled oil the uranium irradiation related c26 c28 triaromatic steroid concentrations provide possible distinguishing criteria for the source potential of the different alum shale units enhanced oil maturation by volcanic intrusion is highlighted by sterane biomarkers and polycyclic aromatic hydrocarbons the alum shale is here considered the main source rock for oil accumulations in lower paleozoic reservoirs of the baltic basin oil seepage occurring in ordovician limestone was mainly generated by the middle cambrian alum shale and middle cambrian sandstone reservoirs were mainly sourced by upper cambrian and lower ordovician alum shale with higher maturity considerations about the assessment of migration distance are based on carbazole concentrations and c29 sterane isomerization advanced studies to unravel detailed lower paleozoic oil source rock correlations are based on meaningful biomarkers offer approaches to significantly reduce the exploration risk in this area and could be applied to similar early paleozoic petroleum systems in other basins

present status of the geochronology of the precambrian rocks of rajasthan abstract age determinations mostly by rb sr analyses of the precambrian rocks of rajasthan by us and by others are summarized and discussed broad periods of acid magmatism at 1 3000 2900 m y 2 2600 2500 m y 3 2000 1900 m y 4 1700 1500 m y and 5 850 750 m y were identified the oldest rocks in the area are the yet undated banded gneisses bgc east of udaipur intruded by the untala granite dated at 2950 m y and hence of mid archean age the basal status hitherto attributed to the berach granite dated at 2600 m y is no longer tenable the radiometric control on the beginning and duration of the overlying aravalli supergroup is not yet satisfactory though a lower limit at 2000 m y is indicated heron s original delhi rocks have recorded two magmatic events widely separate in space and time while the earliest granitic activity at 1600 m y is recorded only in the alwar basin in the northeast the younger activity between 850 750 m y is widespread as shown by the nearly concordant ages of erinpura type granites along the aravalli mountain range and the malani rhyolites in the western plains of the aravalli range

composition and spatial organization of a cold seep community on the south barbados accretionary prism tectonic geochemical and sedimentary context abstract deep faunal assemblages were observed on cold seeps between 1000 and 2000m depth along the southern termination of the barbados accretionary prism during the caracolante ii and diapicar cruises faunal composition and microdistribution of a cold seep community were analyzed at one site using deep sea photographs and seismic 3 5 kz profiles the community is dominated by large mussels up to 20cm long possibly related to the genus bathymodiolus tiny vesicomyid clams and vestimentiferan clusters in which animals are up to 2m long there is a high density of sponges three species bryozoans and gorgonians other taxa occasionally associated with this assemblage include galatheid crabs anemones holothurians and possibly pennatulaceans which are numerous at boundaries of the site a typical deep sea fauna of fish asteroids and ophiuroids is also scattered about the vicinity this seep community is distributed as a band of discontinuous colonies 40 50m in width and more than 10km in length living colonies alternate with accumulations shells and bare areas the substratum is hard mud covered by a ferrugineous crust and cemented by carbonates the early diagenetic character of the bottom and the occurrence of biological assemblages indicate that seepages of sulphur and or methane which have been revealed along the decollement zone of the barbados prism must diffuse through the sea floor these biological and geological features are located on the crests of ne sw anticlinal ridges and mud volcanoes which have been built by diaprism

generation of short chain acid anions in hydrothermally altered sediments of the guaymas basin gulf of california an initial investigation of the concentration distribution of short chain organic acid anions in hydrothermally altered sediments of the guaymas basin reveals the presence of high concentrations of acetate and propionate relative to normal marine sediments acetate and propionate concentrations appear to vary as a function of sediment temperature and reach concentrations 1100 and 200 m respectively at temperatures 100 c as in previously studied oil field formation waters these acid anions probably play a key role in the generation of co2 and hydrocarbons gases hydrogen ion ph buffering the complexing of aqueous ions and mineral dissolution and precipatation at temperatures 100 c these and other acid anions should be important substrates for heterotrophic bacterial processes including sulfate reduction

sediment instability related to fluid venting in miocene authigenic carbonate deposits of the northern apennines italy chemosynthetic carbonates identified by isotopic palaeoecological and sedimentological features are concentrated in middle late miocene satellite and foredeep deposits of the northern apennines chemoherms in the foredeep are hosted in thick pelitic intervals probably deposited in intrabasinal structural highs which are entirely or partly involved in large slumps in many cases associated with extrabasinal slides sediment textures in carbonates and in the enclosing foredeep pelitic sediments indicate a link between hydrocarbon fluid venting sediment deformation and mobilisation and tectonics the intensity and style of fluid release phases directly influenced chemoherm typology and also determined overpressure conditions in low shear strength pelitic sediments favouring sediment mobilisation and influencing slope instability which widely affected the apennine foredeep chemosynthetic carbonates are associated with sites of tectonically fractured and compressed sediments in the apennine foredeep thrust belt system thus indicating a relation with the tectonic loading of the apennine thrust sheets which favoured fluid expulsion along forerunner faults possible gas hydrate contributions to fluid expulsion processes are discussed based on sediment textures compared with modern vent areas finally sediment instability may have facilitated a large amount of fluid escape thus stopping carbonate precipitation

hot fluids burial metamorphism and thermal histories in the underthrust sediments at iodp 370 site c0023 nankai accretionary complex abstract drilling during international ocean discovery program iodp expedition 370 at site c0023 encountered instances of hydrothermal mineralization from 775 to 1121 m below seafloor fluid inclusion homogenization temperatures measured on barite veins within this interval indicate precipitation from fluids with temperatures up to 220 c and salinities ten times higher than interstitial water 16 25 c f 2 8 3 6 wt nacl patches of stratabound mineralization rhodochrosite calcite barite and anhydride are largely confined to the vicinity of veins and have vertical thicknesses and extents that can be explained by precipitation within the thermal aureoles of veins thermal maturities measured on petroleum biomarkers in underthrust sediments record a rise from pre oil window to early oil window thermal maturities basin models show that increases in thermal maturity can be explained by burial metamorphism and kinetic based calculations suggest that hot fluids would only have had a minimal effect on hydrocarbon generation however the movement of hot fluids still has geochemical implications and creates a complex thermal history where both short duration localized heating within fracture zones at hot temperatures 200 c for less than 1 yr and heating during burial over long durations 80 110 c for 0 5 2 myrs need to be considered

ketones in hydrothermal petroleums and sediment extracts from guaymas basin gulf of california the polar compound nso fractions of seabed petroleums and sediment extracts from the guaymas basin hydrothermal system have been analyzed by gas chromatography and gas chromatography mass spectrometry the oils were collected from the interiors and exteriors of high temperature hydrothermal vents and represent hydrothermal pyrolysates that have migrated to the seafloor by hydrothermal fluid circulation the downcore samples are representative of both thermally unaltered and thermally altered sediments the survey has revealed the presence of oxygenated compounds correlated with samples exhibiting a high degree of thermal maturity several homologous series of related ketone isomers are enriched in the interiors of the hydrothermal vent samples or in hydrothermally altered sequences of the downcore sediments dsdp holes 477 and 481a the n alkanones range in carbon number from c11 to c33 with a cmax from 14 to 23 distributions that are similar to those of the n alkanes the alkan 2 ones are usually in highest concentrations with lower amounts of 3 4 5 6 7 and higher alkanones and they exhibit no carbon number preference there is an odd carbon number preference of alkanones observed for downcore samples the alkanones are enriched in the interiors of the hydrothermal vent spires or in downcore hydrothermally altered sediments indicating an origin at depth or in the hydrothermal fluids and not from an external biogenic deposition minor amounts of c13 and c18 isoprenoid ketones are also present simulation of the natural hydrothermal alternation process by laboratory hydrous pyrolysis techniques provided information regarding the mode of alkanone formation hydrous pyrolysis of n c32h66 at 350 c for 72 h with water only or water with inorganic additives has been studied using a stainless steel reaction vessel in each experiment oxygenated hydrocarbons including alkanones were formed from the n alkane the product distributions indicate a reaction pathway consisting of n alkanes and olefins as primary cracking products with internal olefins and alkanones as secondary reaction products hydrous pyrolyses of messel shale spiked with molecular probes have been performed under similar time and temperature constraints to produce alkanone distributions like those found in the hydrothermal vent petroleums

origin of petroliferous bitumen from the buyuk menderes gediz geothermal graben system denizli saraykoy western turkey abstract the kb 5 well is located at the intersection of the geothermally active menderes and gediz graben systems in western turkey significant volumes of petroleum like material plm with its associated thermal water 120 c erupted onto the surface during drilling from a depth of 120 132 m i e from the claystone and marl rich early to middle pliocene kolonkoya formation the purpose of this paper is 1 to characterize this plm 2 to assess the source characteristics from which the plm was likely generated and 3 to recognize the generation mechanism considering the geothermal gradual versus the hydrothermal rapid processes analytical organic geochemistry using thin layer chromatographic separation followed by gas chromatography mass spectrometry gc ms was carried out the plm is composed primarily of polar nso compounds asphaltenes 77 this feature is similar to hydrothermal petroleums e g calcite springs yellowstone national park wyoming the plm shows n alkanes ranging from n c 19 to n c 38 i e with a maximum at n c 30 but n alkanes are depleted in n c 19 an absence of acyclic isoprenoids pristane and phytane and considerably large ucm unresolved complex mixture indicate that the plm has been subjected to a moderate degree of alteration possibly by the accompanying hot geothermal waters the source specific biomarkers i e low c 29 nh c 30 h ratio presence of gammacerane and 18 h oleanane high c 35 c 34 homohopane ratio and c 29 sterane concentration n c 28 n c 27 n c 29 c 28 27 29 r steranes c 29 r c 27 r suggest that the plm is a petroleum and was most likely generated from a tertiary source rock with a carbonate clay rich lithology the source organic matter was predominantly terrestrial and bacterial detritus deposited in relatively saline anoxic environmental conditions maturity sensitive biomarker parameters i e t m t s c 29 sterane 20 s 20 s 20 r 0 35 c 32 hopane 22 s 22 s 22 r 0 57 low diasterane regular sterane ratio correspond to a maturity level of approximately 0 50 0 60 r o this level of maturation could not be reached by such a young upper miocene lower pliocene and shallow sedimentary column max 600 m in the absence of instantaneous hydrothermal activity pahs are not detectable but series of alkylbenzenes alkyltoluenes alk 1 enes and triaromatic steranes are present the lack of organic richness and maturity in the drilled section of the kb 5 well indicates that the petroleum was generated in the deeper sections of the formation the temperature profile of the well and composition of the hydrocarbons in the petroleum suggest that the temperature of the hydrothermal activity during hydrocarbon generation was

geochemical and biogeochemical observations on the biological communities associated with fluid venting in nankai trough and japan trench subduction zones we have studied the compositions and structure of the lamellibranchiacalyptogena sp associated with fluid venting in subduction zones off japan the gills of thecalyptogena are the habitat of symbiotic bacteria which develop owing to chemoautotrophy they most probably assimilate hydrogen sulfide methane and or carbon dioxide and reduce nitrogen the isotopic budget of methane uptake enables to establish the thermal diagenetic origin of the light hydrocarbons brought by the upwelling fluids the microscopic examination of thin sections of the bacteria enables to establish that their membranes are compatible with uptake of inorganic nutrients and to establish relations with the metabolism of archeobacteria

a multidisciplinary study of middle miocene seep carbonates from the northern apennine foredeep italy several pelitic intervals are intercalated at various levels within the marly arenaceous turbiditic successions of the middle miocene northern apennine foredeep they range in thickness from 30 to 200 m and represent sedimentation on top of ephemeral structural highs related to blind faults sediments are made up of hemipelagites and fine grained turbidites and include 13c depleted carbonates related to the rising of methane rich fluids hydrocarbon seep carbonates large portions of pelitic intervals are involved in chaotic masses by soft sediment deformation slumps slides intraformational breccias revealing an intense sediment instability during middle miocene a stratigraphic mineralogic and geochemical study was conducted on two of these pelitic intervals castagno d andrea mt citerna in order to reconstruct carbonate development the composition of fluids and to document the connections between fluid seepage and syndepositional tectonics this multidisciplinary approach has allowed us to discriminate between the two examined pelitic intervals in terms of age depositional rates and conditions organic carbon and post depositional processes seep carbonates are characterized by chemosymbiotic fossil communities autoclastic fractures and brecciation carbonate bodies show complex facies relationships as indicative of different stages in chemoherm growth the compositional study evidences the peculiar chemistry of chemoherm carbonates calcite low in mg and sr compared with carbonates in associated enclosing pelites and with modern chemoherms in general the non carbonate components within the chemoherms are enriched in detrital minerals and depleted in phyllosilicates with respect to the enclosing pelites the mineralogical changes in the clay component within the brecciated unit of the castagno d andrea chemoherms suggest authigenic precipitation of the mg rich phases isotopic analyses show the distinct carbon signature in the chemoherms from the two examined intervals castagno d andrea chemoherms more depleted from 15 8 up to 41 3 pdb than mt citerna from 5 2 up to 16 7 and the transitional 13c depletion trend observed moving from chemoherms to the enclosing pelites moderately depleted and te bouma sequence turbidites in the range of marine carbonates a slight but significant enrichment in 18o up to 1 4 pdb is observed for all chemoherms when compared to values of carbonate phases present in enclosing pelites geochemical data indicate that the brecciated facies of seep carbonates are related to an explosive release of gaseous fluids probably associated with the rise of deep hypersaline fluids

geophysical survey of a mud volcano seaward of the barbados ridge accretionary complex a detailed geophysical investigation that included multibeam bathymetry 3 5 khz channel and single channel seismic profiles 20 heat flow measurements and four piston cores was made of a mud volcano located about 8 km seaward of the toe of the barbados ridge accretionary complex in the northern guiana basin the material erupted from the volcano covers an oval area about 3 9 km with its long axis oriented e w roughly perpendicular to the deformation front a flat topped mound on the western side of the feature is the currently active center acoustic stratigraphy suggests that mud volcanism began at the site about 200 000 ma a piston core taken on the flank of the active mound sampled deposits erupted 20 000 30 000 ma that contain late miocene nannofossils heat flow on the active mound is 4 times that in the surrounding basin one dimensional modeling of this anomaly supports a low level continuing flux of mud and water at rates of 2 5 cm yr the mud volcanism appears to have arisen from the combined action of overpressured water that comes from beneath the accretionary prism and existing overpressures in the oceanic section large east west trending basement escarpments underlie the two known mud volcanoes seaward of the barbados ridge accretionary complex and they probably play an important role in developing vertical pathways for fluid to escape and in determining the location where mud volcanism starts

late archaean to proterozoic tectonothermal events in napier complex east antarctica correlation with east gondwana fragments

solid bitumens an assessment of their characteristics genesis and role in geological processes familiar since antiquity and subject in contemporary times to various characterization schemes the exact nature of solid bitumen is not yet fully known bitumens have random polymer like molecular structures are mobile as highly viscous fluids or were once fluids but have since turned into solids solid bitumens consist mainly of large moieties of polyclyclic aromatic hydrocarbons occasionally with finely admixed fine grained cryptocrystalline graphite solid bitumens are distinguished from kerogen which is the syngenetic and generally finely dispersed particulate organic matter in sedimentary rock that virtually does not migrate following its deposition occurrences of solid bitumens are relevant to petroleum exploration as well as the search for and evaluation of a variety of metallic mineral deposits genesis of bitumen is in many cases linked to the thermal and hydrothermal history of organic matter in sedimentary rock apparently bitumen or more specifically organic acids generated along with bitumen during diagenesis may alter porosity of reservoir rocks or otherwise prepare the ground for ore deposition bitumen is also relatively sensitive to alteration processes some of which such as oxidative weathering water leaching biodegradation contact metamorphism and ionizing radiation may likewise affect its nature elemental composition of bitumen commonly reflects the nature of mineral deposits is is possible that in petroleum exploration trace metal abundances of bitumen may eventually allow prediction of crude oil types and volumes anticipated from a given source rock beside transition elements notably ni and v highly anomalous concentrations of u pt and au occur in some solid bitumens during the generation of petroleum from kerogen the trend in 13c is toward lighter values the opposite seems to occur when liquid petroleum is subjected to thermal cracking and or related processes yielding solid bitumen enriched in 13c and isotopically light methane in fact except for deasphalting and possibly some irradiation processes the result of thermal cracking oxidation water leaching inspissation drying and bacterial degradation of crude oil is that lower molecular weight hydrocarbons are removed leaving bitumen residues enriched in aromatic hydrocarbons heteroatomic compounds nso and 13c such phenomena are relevant to bitumen paragenesis in petroleum reservoir rocks to certain phanerozoic occurrences of multiple generations of bitumens and to bitumens in mineral deposits

hydrothermal discharge and alteration in near surface sediments from the guaymas basin gulf of california abstract in the guaymas basin gulf of california hydrothermal fluids discharge onto the seafloor via both direct emanation through hydrothermal spires and diffusely through the sediments the latter mode is the focus of this study short 20 cm sediment cores were taken in zones of diffuse hydrothermal flow for chemical investigation of interstitial fluids and bulk solids the hydrothermal component of the pore fluids was quite variable indicating the heterogenous nature of the near surface flow regimes the bulk solids chemistry indicates that the suite of cores has encountered different amounts of cumulative hydrothermal exposure dissolution of biogenic silica and deposition of large amorphous silica clasts in the sediment are related to the extent of hydrothermal exposure surface enrichments in ba are formed as barite precipitates when ba rich hydrothermal fluids mix with sulfate rich seawater at the seafloor formation of pyrite and removal of mg from the solid phases are also observed effects of hydrothermal flow through these sediments

multibeam bathymetric survey and high resolution seismic investigations on the barbados ridge complex eastern caribbean a key to the knowledge and interpretation of an accretionary wedge abstract an important problem of active margin processes is the way accretionary wedges form in response to oceanic crust subduction new data have been obtained along the barbados ridge in front of the lesser antilles tertiary island arc they include high resolution multichannel seismic data and accurate sea beam bathymetric maps both have been used to propose a 3 dimensional interpretation of tectonic and sedimentary processes related to subduction such as oceanic off scraping ductile folding relative uplift and subsidence fore arc basin evolution and mud diapirism they all improved our knowledge of the evolution of accretionary prisms and more specifically of the barbados ridge development in plio quaternary time previous tectonic events are deduced from recently published geological data from barbados and the lesser antilles islands

liquefied vs stratified sediment mobilization processes insight from the south of the barbados accretionary prism this paper discusses the nature and origin of subsurface sediment mobilization processes in deep marine clay rich environments in the studied area of the southern barbados accretionary prism new geophysical acquisitions have emphasized the spectacular widespread development of mud volcanoes that are well developed along ramp anticlines and along sigmoidal rises with trends that are oblique to the axes of the main folds of the accretionary wedge on some active mud volcanoes heat flow measurements show high positive anomalies related to high fluxes of mud transfer the mobilized solid fraction expelled by the mud volcanoes does not originate from a unique source bed but from various formations pierced by the mud conduits and is driven by the water phase the area studied also exhibits trends of structures corresponding to sub circular massive local uplifts of deformed but well preserved stratified sediments turbidites and hemipelagics no piercing shale diapirs have been encountered in this area some of these local uplift structures are complicated by the development of collapses calderas and superimposed mud volcanoes mud volcanism corresponds fundamentally to fluid displacement water and gas whereas massive sedimentary uplift corresponds to large vertical displacements of stratified solid levels but for which the deep cause could be partly the intrusion of mud plugs both are dynamic phenomena controlled by the development of overpressure at depth contributing to sedimentary mobilizations

cloud tracked winds for the first mars global surveyor mapping year we have measured winds using cloud motion in consecutive mars global surveyor mgs mars orbiter camera moc wide angle global map swaths taken during the first mapping year l s 135 360 111 we present a total of 11 200 wind vectors collected in the north polar region during l s 135 195 late summer early fall and l s 20 55 mid spring and in the south polar region during l s 337 10 late summer early fall for cases with good coverage we also present the derived mean zonal and meridional winds and the associated eddies the speed of the zonal winds in 60 n 70 n increases at 0 6 m s l s in late northern summer and that in 60 s 70 s increases at a rate of 0 7 m s l s in late southern summer the latitudinal distribution of zonal wind within 50 n 75 n from mid northern summer to early northern fall indicates that winds at higher latitudes are generally weaker than those at lower latitudes but the rate of increase with time is faster at higher latitudes there is a cyclonic gyre in the 90 w 0 30 e sector in the north polar region there are large scale waves in the weekly mean meridional wind and in the biweekly mean eddy momentum flux and eddy kinetic energy fields in the north polar region from mid to late summer the cloud tracked winds in the north are generally consistent with winds calculated by general circulation model at the water condensation level derived from mgs thermal emission spectrometer tes observations but appear stronger than the gradient winds derived from tes assuming no flow at the surface