coal petrology of coal seams from the leao butia coalfield lower permian of the parana basin brazil implications for coal facies interpretations abstract in the leao butia coalfield rio grande do sul the coal seams occur in the rio bonito formation guata group tubarao supergroup of the parana basin brazil and are of permian artinskian kungurian age this study is the first detailed investigation on the coal petrographic characterization of the coal bearing sequence in relation to the depositional settings of the precursor mires both in terms of whole seam characterization and in seam variations the study is based on the analyses of nine coal seams i2 ci l4 l3 l2 l1 s3 s2 s1 which were selected from core of borehole d 193 leao butia and represent the entire coal bearing sequence the interpretation of coal facies and depositional environment is based on lithotype maceral and microlithotype analyses using different facies critical petrographic indices which were displayed in coal facies diagrams the seams are characterized by the predominance of dull lithotypes dull banded dull the dullness of the coal is attributed to relatively high mineral matter inertinite and liptinite contents the petrographic composition is dominated by vitrinite 28 70 vol mmf and inertinite 30 vol mmf groups liptinite contents range from 7 to 30 vol mmf and mineral matter from 4 30 vol microlithotypes associations are dominated by vitrite duroclarite carbominerite and inertite it is suggested that the observed vertical variations in petrographic characteristics lithotypes microlithotypes macerals vitrinite reflectance were controlled by groundwater level fluctuations in the ancient mires due to different accommodation peat accumulation rates correlation of the borehole strata with the general sequence stratigraphical setting suggests that the alluvial fan system and the coal bearing mudstone succession are linked to a late transgressive systems tract of sequence 2 based on average compositional values obtained from coal facies diagrams a deposition in a limno telmatic to limnic coal facies is suggested

extension of the parana basin to offshore brazil implications for coalbed methane evaluation abstract coalbed methane cbm is a worldwide exploration target of the petroleum industry in brazil the most important coal bearing succession is associated with the permian rio bonito formation of the parana basin the gas prone areas are located at the southeastern margin of the parana basin and possibly in the offshore region of the northern part of the pelotas basin coalfields end abruptly at the present day shoreline a result of rifting of gondwana and the evolution of the south atlantic ocean all geologic indicators suggest that in pre rift times the coal seams extended further eastwards probably now lying deeply buried below the sedimentary succession of the pelotas basin the present paper discusses structural stratigraphic seismic and aeromagenetic data that support the preservation of continental crust beneath ocean sediment if the coal beds had similar lateral extent to known onshore coals and coal beds extended across the projected extension of the parana basin and there was a conservative 5 m of cumulative coal thickness then a potential methane volume can be estimated for this newly inferred resource average onshore coal gas content is 32 scf ton 1 00 m 3 ton if this is similar in the offshore coal deposits then the hypothetical methane volume in the offshore area could be in excess of 1 9 10 12 scf 56 10 9 m 3 metamorphism from dikes associated with rifting are potential complicating factors in these deposits and since no borehole reaching the deep lying strata in the offshore area are available this is a hypothetical gas resource with a certain level of uncertainty which should be tested in the future by drilling a deep borehole

high pressure methane and carbon dioxide sorption on coal and shale samples from the parana basin brazil abstract an experimental study has been conducted to assess the potential for coalbed methane production and carbon dioxide storage in coals carbonaceous shales and source rocks in the parana basin in brazil high pressure sorption tests with methane and carbon dioxide were performed on coal and carbonaceous shales from the santa terezinha coalfield and samples from two principal petroleum source rocks measured excess sorption capacities ranged from 0 03 to 0 47 mmol g for methane and 0 14 to 0 81 mmol g for carbon dioxide showing a decrease with decreasing organic matter content linear regression lines for methane sorption capacity vs toc extrapolated to approximately zero whereas for carbon dioxide the intercept of the regression line indicated a residual sorption capacity of 0 2 mmol g on the mineral matter present day gas contents of coals collected from the first cbm well in the santa terezinha coalfield correspond to 13 38 of the measured maximum sorption capacities carbon dioxide sorption capacities exceed methane sorption capacities by a factor of 1 9 to 6 9 for these coals free sorption capacities of the under saturated coals in combination with preferential sorption of carbon dioxide could favour co 2 enhanced methane recovery and co 2 storage in coals and shales of the study area based upon the calculated coal reserves gas contents and measured sorption capacities a total storage potential of 15 4 gt co 2 was estimated for an area of 20 40 km 2 in the santa terezinha coal field assuming a combined co 2 enhanced coalbed methane ecbm production and co 2 storage operation to fully evaluate the potential for carbon dioxide storage and coalbed methane production further studies are required to assess producibility of methane and efficiency of long term co 2 storage in the study area

preliminary assessment of resources and economic potential of individual gas hydrate accumulations in the gulf of mexico continental slope abstract some global estimates suggest that gas hydrates represent the largest reservoir of fossil fuel however only a few studies of the resource and economic potential of individual gas hydrate accumulations exist here we estimate the volume of hydrate bound gas at gc green canyon blocks 184 185 gc 234 235 gb garden banks 388 mc mississippi canyon 798 842 gc 204 mc 852 853 and at atwater valley 425 426 sites in the gulf of mexico at water depths 500 2000 m the structural accumulations may contain from 4 7 10 8 to 1 3 10 11 m 3 of gas at standard temperature and pressure the resources in individual gas hydrate accumulations are comparable by volume with the reserves in very small to major conventional gas fields various geologic technologic and economic factors affect the economic potential of studied accumulations the mc 852 853 appears to be characterized by the most favorable combination of these factors and thus is suggested to have the highest economic potential the economic potential of gas hydrate accumulations at gc 204 gb 388 and at 425 426 sites is ranked as average gas hydrate accumulations at gc 234 235 gc 184 185 and mc 798 842 sites contain only small volumes of hydrate bound gas and likely have no economic potential future gas hydrate research should focus on the detailed study of large structural gas hydrate accumulations from which gas may be profitably recovered e g the mc 852 853 site

using iron speciation in authigenic carbonates from hydrocarbon seeps to trace variable redox conditions abstract seepage of hydrocarbon rich fluids out of the marine sedimentary column is characterized by temporal changes of flow intensity and resultant spatially variable redox conditions authigenic carbonates at marine hydrocarbon seeps provide excellent geological and geochemical archives that serve to explore seepage dynamics over time in this study we investigated the potential of mossbuaer spectroscopy and fe contents of seep related authigenic carbonates from the congo fan the gulf of mexico and the black sea for reconstructing past redox conditions and fluid seepage activity at cold seeps the fe speciation observed by mossbauer spectroscopy and fe contents suggest that 1 the congo fan carbonates precipitated in a sulfidic environment 2 the formation conditions of seep carbonates were variable at the gulf of mexico seep site ranging from oxic to suboxic and anoxic and even spanning into the methanogenic zone and 3 the stratified water column of the black sea or suboxic condition resulted in low fe contents of black sea carbonates the study reveals that fe speciation can provide constraints on the wide range of redox conditions that imprinted seep carbonates during the life span of seepage similarly mossbauer spectroscopy particularly when used in combination with the analysis of redox sensitive elements is a promising tool to trace variable redox conditions in marine paleoenvironments other than seeps

sequence stratigraphy of a lagoonal estuarine system an example from the lower permian rio bonito formation parana basin brazil abstract detailed stratigraphic analysis of the early permian artinskian kungurian succession of the intracratonic parana basin in southernmost brazil has revealed that the study region previously interpreted as formed by a barrier island system in a shallow wave dominated sea actually originated mainly in a mixed tide and wave influenced estuary setting four main depositional systems have been recognized alluvial fan fluvial dominated delta lagoonal estuary and barrier shoreface the regional correlation of the lithofacies within the different depositional systems has led to a high resolution stratigraphic framework with three third order depositional sequences sequence boundary sb1 marks the base of the permian succession above the crystalline basement sequence boundary sb2 is characterized by fluvial sediments overlying marine shales and sandstones sequence boundary 3 sb3 has a different signature reflecting differential subsidence some areas clearly experienced temporary regression and basinward shift of facies while in others the transgression rapidly reworked the regressive sediments and left only a thin veneer of pebbly sandstone the typical signature of a transgressive surface coinciding with a sequence boundary within depositional sequence 2 the main target of the study because it has economically important coal seams seven parasequences are recognized two forming the lowstand systems tract of the sequence four forming the transgressive systems tract and one parasequence forming the highstand systems tract two parasequence limits are erosional transgressive surfaces as indicated by the occurrence of a substrate controlled ichnofacies glossifungites and a veneer of intraclasts composed of nodules chert shell fragments and muddy rip up clasts the base level variations had a strong tectonic component as indicated by 1 the shift in shoreline configuration from east west to a north south direction after unconformity sb3 formation 2 the transgressive reworking of regressive sediments in the southern part of the study area indicating differential subsidence and consequent differential accommodation available for the sediments and 3 the angularity displayed by the strata adjacent to the sequence boundary sb3

geologic and hydrological controls on coal reservoir water production in marine coal bearing strata a case study of the carboniferous taiyuan formation in the liulin area eastern ordos basin china abstract coalbed methane cbm is commercially explored and produced in the continental permian shanxi formation of the southern qinshui and eastern ordos basins of china however cbm production in marine carboniferous taiyuan formation is hindered by a lack of knowledge about the controlling factors on water production the liulin area of the eastern ordos basin is one of the trail areas for cbm development in china in this study water yield characteristics and their influencing factors during cbm production in the liulin area were investigated by fluid inclusion studies core slice observations and stable isotope analyses of groundwater the results demonstrated that the recharge area for this limestone aquifer of the taiyuan formation is the exposed carbonate in the northeastern liulin area the thickness along with the dissolved pores and fractures of the limestone aquifer were closely related to the water production of the cbm well from an engineering point of view hydraulic fracturing allows the direct movement of water from coal seams to the roof limestone aquifers which was a key factor in the high water yield of cbm wells in the liulin area finally based on the structure and distribution of roof limestone as well as water production data the geologic scenarios for water production in the taiyuan formation was divided into four types these divisions indicated that the best prospective target areas for cbm production should have low numbers of faults small limestone thicknesses relatively large burial depths and normal reservoir pressures and temperatures the results of this study are helpful for cbm exploration and production in the marine coal bearing strata of china

the structure of the lower crust at the argentine continental margin south atlantic at 44 s abstract it is well established that the argentine passive margin is of the rifted volcanic margin type this classification is based primarily on the presence of a buried volcanic wedge beneath the continental slope manifested by seismic data as a seaward dipping reflector sequence sdrs here we investigate the deep structure of the argentine volcanic margin at 44 s over 200 km from the shelf to the deep oceanic argentine basin we use wide angle reflection refraction seismic data to perform a joint travel time inversion for refracted and reflected travel times the resulting p wave velocity depth model confirms the typical volcanic margin structure an underplated body is resolved as distinctive high seismic velocity vp up to 7 5 km s feature in the lower crust in the prolongation of a seaward dipping reflector sequence a remarkable result is that a second isolated body of high seismic velocity vp up to 7 3 km s exists landward of the first high velocity feature the centres of both bodies are 60 km apart the high velocity lower crustal bodies likely were emplaced during transient magmatic volcanic events accompanying the late rifting and initial drifting stages the lateral variability of the lower crust may be an expression of a multiple rifting process in the sense that the south atlantic rift evolved by instantaneous breakup of longer continental margin segments these segments are confined by transfer zones that acted as rift propagation barriers a lower crustal reflector was detected at 3 to 5 km above the modern moho and probably represents the lower boundary of stretched continental crust with this finding we suggest that the continent ocean boundary is situated 70 km more seaward than in previous interpretations

permian endemic bivalves of the irati anoxic event parana basin brazil taphonomical paleogeographical and evolutionary implications abstract anoxic to dysoxic conditions must have existed in the parana basin during the deposition of the permian oil bearing shales of the irati formation reflecting the marine isolation of the basin from the panthalassic ocean in this environment benthic invertebrates are extremely rare in contrast to the overlying serra alta and teresina formations which were deposited in dysoxic oxic waters respectively hence the abundant shallow burrowing endemic bivalves recorded in the shales of the basal portion of the irati formation are one of the most distinctive features of this stratigraphic interval their preservation in offshore deposits is however a product of storm flows in shallow waters that swept the shells to distal settings subsequently these were sorted by long lasting shelf currents that produced dense 2 5 shells 20 cm2 pavements in which shells in a hydrodynamically stable posture convex up predominate forming thin complex shell concentrations despite their simple internal stratigraphy the new data presented here have important paleoecologic paleogeographic and evolutionary implications and indicate that a during the deposition of the oil rich shales of the irati formation numerous benthic bivalves thrived in the contemporary shallow water bottoms of the parana basin b the mono to paucispecific nature of the studied shell rich pavements is in part due to hydrologic shell transport and c restricted connections to open ocean waters panthalassa existed during irati times therefore the origin of the endemic passa dois molluscan fauna occurred somewhere between the interval represented by the underlying palermo formation and the basal portion of the irati formation finally these endemic bivalves appeared at least 10 million years earlier than previously thought

petrology and geochemistry of lavas from antuco volcano a basaltic volcano of the southern andes 37 25 s sierra velluda plio pleistocene cerro condor pleistocene and antuco holocene volcanoes form a volcanic group located in the southern andes at latitude 37 25 s lavas from these volcanoes become less silicic with decreasing age antuco volcano consists of two units pre and post caldera collapse antuco i and antuco ii and a parasitic cone antuco lavas are basalts and those from antuco i and ii are relatively uniform in mineral and chemical composition common phenocrysts are plagioclase an65 an81 18 33 vol olivine fo 78 3 18 vol and clinopyroxene 0 5 3 vol the same phenocrysts occur in the parasitic cone lavas but plagioclase is much more abundant key compositional features of antuco lavas are 52 sio2 17 al2o3 3 3 4 2 na2o 1 2 tio2 0 9 k2o and mg mg fe ratios 0 60 these major element features characterize many circumpacific basalts in island arc and continental margin environments the antuco i and ii lavas have light ree abundances equal to 26 33 chondrites and heavy ree abundances equal to 8 9 chondrites some samples have positive 10 eu anomalies but no negative eu anomalies occur in these lavas trace element abundances in the antuco lavas are similar to those in theoretical liquids derived by 5 10 partial melting of garnet free peridotite followed by 10 fractionation of a clinopyroxene 40 and olivine 60 cumulate thus a plausible model is that the lavas were derived from the mantle by partial melting followed by mafic mineral fractionation

changing redox conditions at cold seeps as revealed by authigenic carbonates from alaminos canyon northern gulf of mexico anaerobic oxidation of methane in anoxic sediments at cold seeps often leads to formation of authigenic carbonates close to the seafloor along continental margins recent work however indicated that the redox conditions in sediments may vary to some degree during seepage activity in order to shed new light on the extent of this variability authigenic carbonates from alaminos canyon lease block 645 of the northern gulf of mexico have been characterized by means of inorganic and organic geochemistry the carbonates were collected from seep deposits representing various seafloor morphologies including extensive pavements mounds fractured carbonate slabs surrounded by dense bivalve shells and vestimentiferan tubeworm colonies the deposits almost entirely consist of aragonite the 18o values of aragonite vary from 2 6 to 5 8 v pdb suggesting precipitation in slight disequilibrium with the surrounding pore fluids the 13c values of aragonite between 33 9 and 20 4 v pdb agree with variable amounts of carbonate derived from oxidation of thermogenic methane and crude oil methane was primarily oxidized in an anaerobic process as revealed by the presence of 13c depleted molecular fossils of methane oxidizing archaea 13c values as negative as 118 and sulfate reducing bacteria 13c values as negative as 97 the syntrophic partners in the anaerobic oxidation of methane the observed inventories of molecular fossils in the authigenic carbonates mirror those of known consortia of anaerobic methane oxidizing archaea anme and sulfate reducing bacteria namely the anme 2 desulfosarcina desulfococcus dss and anme 3 desulfobulbus dbb consortia in contrast the same carbonates exhibit shale normalized rare earth elements patterns that all display real negative ce anomalies ce ce 0 78 suggesting that at least temporarily oxic conditions prevailed the episodic occurrence of oxic conditions is confirmed by the presence of molecular fossils of aerobic methanotrophic bacteria including 4 methylcholesta 8 14 24 dien 3 ol and two bacteriohopanepolyols aminotetrol and aminotriol the 13c values of the biomarkers of aerobic methanotrophs are as negative as 58 and are consequently less 13c depleted than the molecular fossils of the prokaryotes performing anaerobic oxidation of methane a pattern in accord with culture experiments overall our results suggest that redox conditions at cold seeps are variable this variability probably reflects changes in seepage flux the combination of an inorganic and an organic geochemical approach used here is promising to better assess the variability and diversity of past fluid and gas expulsion at seeps

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

a blast of gas in the latest paleocene simulating first order effects of massive dissociation of oceanic methane hydrate carbonate and organic matter deposited during the latest paleocene thermal maximum is characterized by a remarkable 2 5 excursion in delta 13c that occurred over approximately 10 4 yr and returned to near initial values in an exponential pattern over approximately 2 x 10 5 yr it has been hypothesized that this excursion signifies transfer of 1 4 to 2 8 x 10 18 g of ch4 from oceanic hydrates to the combined ocean atmosphere inorganic carbon reservoir a scenario with 1 12 x 10 18 g of ch4 is numerically simulated here within the framework of the present day global carbon cycle to test the plausibility of the hypothesis we find that 1 the delta 13c of the deep ocean shallow ocean and atmosphere decreases by 2 3 over 10 4 yr and returns to initial values in an exponential pattern over approximately 2 x 10 5 yr 2 the depth of the lysocline shoals by up to 400 m over 10 4 yr and this rise is most pronounced in one ocean region and 3 global surface temperature increases by approximately 2 degrees c over 10 4 yr and returns to initial values over approximately 2 x 10 6 yr the first effect is quantitatively consistent with the geologic record the latter two effects are qualitatively consistent with observations thus significant ch4 release from oceanic hydrates is a plausible explanation for observed carbon cycle perturbations during the thermal maximum this conclusion is of broad interest because the flux of ch4 invoked during the maximum is of similar magnitude to that released to the atmosphere from present day anthropogenic ch4 sources

fluid flow and mass flux determinations at vent sites on the cascadia margin accretionary prism fluid venting from the toe of the accretionary prism off oregon was measured in situ during a series of dives with dsrv alvin in 1987 and 1988 a benthic chamber was placed over active vent sites to sequentially collect samples of venting fluids and to make direct measurements of discharge rates calibrated flow meter measurements and flow rates determined from dissolved methane transfer indicate that discharge from two vent sites alvin 1428 and alvin 1900 ranges roughly between 100 and 500 l m 2 d 1 with the most reliable estimates falling in the range of 125 150 l m 2d 1 these rates imply subsurface advective flow on the order of 100 m yr 1 comparison of observed discharge rates with rates calculated for steady state expulsion supported by accretion related compaction indicates that the observed flow is greater than predicted flow by several orders of magnitude the disparity dictates that fluids are not derived locally but are transported laterally within the prism or that flow is not steady state and that individual vents are short lived features in the ongoing accretion process

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

pore fluid chemistry of the north anatolian fault zone in the sea of marmara a diversity of sources and processes as part of the 2007 marnaut cruise in the sea of marmara an investigation of the pore fluid chemistry of sites along the main marmara fault zone was conducted the goal was to define the spatial relationship between active faults and fluid outlets and to determine the sources and evolution of the fluids sites included basin bounding transtensional faults and strike slip faults cutting through the topographic highs the basin pore fluids are dominated by simple mixing of bottom water with a brackish low density pleistocene lake marmara end member that is advecting buoyantly and or diffusing from a relatively shallow depth this mix is overprinted by shallow redox reactions and carbonate precipitation the ridge sites are more complex with evidence for deep sourced fluids including thermogenic gas and evidence for both silicate and carbonate diagenetic processes one site on the western high displayed two mound structures that appear to be chemoherms atop a deep seated fluid conduit the fluids being expelled are brines of up to twice seawater salinity with an exotic fluid chemistry extremely high in li sr and ba oil globules were observed both at the surface and in cores and type ii gas hydrates of thermogenic origin were recovered hydrate formation near the seafloor contributes to increase brine concentration but cannot explain their chemical composition which appears to be influenced by diagenetic reactions at temperatures of 75 c 150 c hence a potential source for fluids at this site is the water associated with the reservoir from which the gas and oil is seeping which has been shown to be related to the thrace basin hydrocarbon system our work shows that submerged continental transform plate boundaries can be hydrologically active and exhibit a diversity of sources and processes

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

methane seepage patterns during the middle pleistocene inferred from molybdenum enrichments of seep carbonates in the south china sea abstract seepage of methane rich fluids are widespread along the continental margins of the world intense seepages of methane may lead to the emission of this powerful greenhouse gas into the hydrosphere and atmosphere with implications in the understanding of past dramatic marine environment changes and global warming however euxinic environments with sulfidic bottom water as a result of vigorous seepages at ancient cold seeps remain unidentified here we report trace element geochemistry and associated mineralogical and carbon and oxygen isotopic data in seep carbonates collected from long drill cores in the south china sea three distinct stages of methane seepages events probably caused by the dissociation of gas hydrates are discernible carbonates formed in stage 2 during the marine isotope stage 5 mis5 are mainly occurred as aragonite and show extremely high molybdenum mo contents up to 118 g g and strong enrichments of authigenic mo in relative to uranium these results suggest the presence of intermittent or even permanent euxinic conditions generated by sulfidic bottom water that result from intensive methane seepages in contrast mineral compositions and trace element patterns indicate that the carbonates before and after the mis 5 stages 1 and 3 form within sulfidic conditions restricted to pore water under relatively lower methane fluxes our results highlight extremely intense methane seepages that may potentially result in localized euxinic environments the inferred euxinic environments imply more amount of massive methane release into the water column than a previous estimation which was triggered by large scale dissociation of gas hydrates in the south china sea during mis 5

increased continental margin slumping frequency during sea level lowstands above gas hydrate bearing sediments we present sup 14 c data on sediment samples from cores of the upper 7 m of the sediment column overlying a major continental rise gas hydrate field on the southern carolina rise and inner blake ridge offshore the southeastern united states the data show that glacial age sediments are underrepresented in the cores the observation is consistent with a previously predicted association between sea level lowstands and increased frequency of sea floor slumping on continental margins containing gas hydrates 26 refs 3 figs

benthic foraminifera of the blake ridge hydrate mound western north atlantic ocean abstract in a 240 m 70 m area at the top of the blake ridge diapir water depth 2150 m the benthic foraminiferal assemblage in surface sediment 0 1 cm consists of about 130 species hydrocarbon seepage is indicated here by the presence of methanotrophic bivalves and white bacterial mats and by present day formation of gas hydrate the foraminiferal assemblage density is generally high indicating an abundance of food bolivina lowmani and globocassidulina subglobosa dominate the assemblage in the silt clay substrate whether at the edge of bathymodiolid mussel beds or under bacterial mats the only notable difference between these two sample groups is in the higher variation of foraminiferal density in the mussel bed samples a control sample at 32 29 654 n and 76 11 324 w taken from bioturbated sediment light grey silt and clay with no visible bacterial or molluscan colonization is comparable to the seep samples in the distribution of calcareous species but shows a much higher diversity and abundance of agglutinated species no segregation of foraminiferal species by substrate geochemistry can be inferred for the seep samples and the possible effect of variable sulfide or methane fluxes on the community cannot be demonstrated by our data

north atlantic volcanic margins dimensions and production rates early tertiary lithospheric breakup between eurasia and greenland was accompanied by a transient 3 m y igneous event emplacing both the onshore flood basalts of the north atlantic volcanic province navp and huge extrusive complexes along the continent ocean transition on the rifted continental margins seismic data show that volcanic margins extend 2600 km along the early eocene plate boundary in places underlain by high velocity 7 2 7 7 km s lower crustal bodies quantitative calculations of navp dimensions considered minimum estimates reveal an areal extent of 1 3 106 km2 and a volume of flood basalts of 1 8 106 km3 yielding a mean eruption rate of 0 6 km3 yr or 2 4 km3 yr if two thirds of the basalts were emplaced within 0 5 m y the total crustal volume is 6 6 106 km3 resulting in a mean crustal accretion rate of 2 2 km3 yr thus navp ranks among the world s larger igneous provinces if the volcanic margins are considered the velocity structure of the expanded crust seaward of the continent ocean boundary differs from standard oceanic and continental crustal models based on seismic velocities this volcanic margin crust can be divided into three units of which the upper unit corresponds to basaltic extrusives the regionally consistent velocity structure and geometry of the crustal units suggest that the expanded crust including the high velocity lower crust which extends some distance landward of the continent ocean boundary was emplaced during and subsequent to breakup the volcanic margin crust was formed by excess melting within a wide zone of asthenospheric upwelling probably reflecting the interaction of a mantle plume and a lithosphere already extending

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

temporal variability of in situ methane concentrations in gas hydrate bearing sediments near bullseye vent northern cascadia margin 1 to assess the temporal variability in the methane fluxes from marine sediments that overly gas hydrate bearing sediments and the factors that might control its rate in situ methane concentrations were measured near bullseye vent on the northern cascadia continental margin a long term sampling device collected overlying water and pore fluid samples from 25 cm above seafloor at the sediment water interface swi and 7 cmbsf centimeters below seafloor over a 9 month period august 2009 may 2010 these samples provide a record at 4 day resolution of in situ methane ethane propane sulfate and chloride concentrations as well as stable carbon isotope ratios of methane 13c ch4 and dissolved inorganic carbon 13c dic we show that pore fluids near the swi are saturated or supersaturated with respect to methane 80 mm and the methane flux from the seabed is variable over time we hypothesized that regional seismic activity controlled this variable ch4 flux in the northern cascadia continental margin setting however we found no direct correlation between earthquakes and ch4 flux we also posited alternative controls on ch4 flux variability such as storms regional oceanography and microbial activity again no direct correlation was seen this study takes first steps toward exploring which physical factors play a role in methane flux from hydrate bearing sediments

measurements of transience and downward fluid flow near episodic methane gas vents hydrate ridge cascadia aqueous flux measurements within cold seep regions on northern hydrate ridge cascadia indicate a high degree of variability with extended periods of downflow and reversals of flow direction over periods of weeks to months local episodic venting of free methane gas was also observed the instruments recorded similar changes in hydrologic flow patterns both on and off clam fields the magnitude of the flow rates decreasing away from the clam field the coincidence of episodic gas venting with nearby highly variable aqueous fluid flow suggests that they may be coupled we propose that these observations are consistent with the action of a gas driven pump that operates somewhat like a geyser the hypothesis of gas driven pumping of seawater through northern hydrate ridge has important ramifications for the mass fluxes through this region

fluid and chemical cycling at bush hill implications for gas and hydrate rich environments 1 the results of a deployment of aqueous flux meters at the bush hill hydrate mound show that persistent hydrologic instability is a primary feature of the globally abundant gas and hydrate rich cold seep environment seven flux meters were deployed for 14 weeks in the area of the bush hill hydrate mound instruments were deployed on microbial mats bivalves adjacent to the surface hydrate mound and a site without visible fauna flow rates were observed to range from downflow of 0 01 mm day to upflow of 15 mm day temporal variability and a major hydrological event were observed to occur on all instruments there is evidence that this event was related to a gas expulsion episode the two instruments which exhibited downflow during the event were near surface hydrates and bubbling vents nearby instruments recorded a rapid increase in flow rates at the time of the event with a subsequent decrease in rates to the previous background values two instruments showed significant output of seawater like fluids while the others output typical methane seep type pore fluids these results at a passive margin site along with our previously published convergent margin results at gas rich northeast pacific cold seeps hydrate ridge eel river margin illustrate the hydrologic complexity of these environments we now propose that these and our earlier results are characteristic of seafloor environments which have abundant free gas and hydrates these mechanisms have major consequences for the near surface geochemical and microbial environment and for the way we interpret measurements made in these areas

crustal structure across the colorado basin offshore argentina summary the geology of the wide shelves surrounding the south atlantic is closely linked to the kinematics and history of the opening of the ocean however several wide sedimentary basins which developed along the margins show peculiarities that are not yet understood in the context of the evolution of the south atlantic the colorado basin a wide sedimentary basin on the broad shelf of argentina extends in ew direction the basin s evolution oblique or orthogonal to the continent ocean boundary indicates that it is not a product of simple progressive extension and crustal thinning in addition a basement high paralleling the continental margin and separating the colorado basin from the deep sea basin is a common interpretation these findings are hardly in accordance with the idea that the colorado basin is an extensional basin that developed in conjunction with the early e w opening phase of the south atlantic in the late jurassic early cretaceous the composition type and structure of the basement key points for the evaluation of the basins evolution are widely speculative in this context multichannel seismic reflection data from the argentine shelf and a 665 kmlong onshore offshore refraction profile running across the colorado basin onto the coast are discussed in combination with gravity data the stratigraphy for the sedimentary successions was adopted from the literature and the reflection seismic marker horizons formed besides the interval velocities the input for the starting model for refraction seismic traveltime modelling the modelling strategy was an iterative procedure between refraction seismic traveltime and gravity modelling the preparation of the density models was coarsely orientated on published velocity density relations the modelling results are in favour of a continuation of the main onshore geological features beneath the sedimentary infill of the colorado basin we interpret the basement along the line from west to east as offshore continuation of the ventana hills the

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

stable isotope signatures and methane use by new zealand cold seep benthos the carbon isotopic composition of seep faunal tissue represents a time integrated view of the interaction between biology and the biogeochemical gradients within the environment here we provide an initial description of carbon and nitrogen stable isotope signatures of dominant symbiont bearing megafauna and heterotrophic mega and macrofauna from 10 methane seep sites on the continental margin of the north island of new zealand 662 1201 m water depth isotopic signatures suggest that sulfide oxidation supports symbiont bearing taxa including solemyid and vesicomyid bivalves and methanotrophic symbionts are present in the seep mussel bathymodiolus sp multiple species of frenulata siboglinidae are present and have a range of isotopic values that are indicative of both thiotroph and methanotroph based nutrition isotopic composition of the tubeworm lamellibrachia sp varied by 23 3 among individuals although there was no consistent difference among sites variation in methane use by heterotrophic fauna appears to reflect the availability of hard vs soft substrate macrofauna on hard substrates had high 13c signatures reflecting consumption of photosynthetic derived organic matter two unique biotic assemblages were discovered to be fueled largely by methane a hard substrate multi phyla sponge associated community inhabiting the sponge pseudosuberites sp and a soft sediment assemblage dominated by ampharetid polychaetes isotope signatures yield estimates of 38 100 and 6 100 methane derived carbon in sponge associates and ampharetid bed macrofauna respectively these estimates are comparable to those made for deeper methane seeps at the florida escarpment 3290 m and kodiak alaska seeps 4445 m the overall high use of methane as a carbon source by both symbiont bearing and heterotrophic fauna suggests that new zealand methane seeps are an ideal model system to study the interaction among metazoans bacteria archaea and their resulting effect on methane cycles

the eo permian coal seams of the parana basin in southernmost brazil an analysis of the depositional conditions using sequence stratigraphy concepts the eo permian of the parana basin is studied using sequence stratigraphy the study was based on data acquired from 92 entirely cored and geophysically logged boreholes the study is an applicability test of the conceptual and methodological framework of sequence stratigraphy in the examination of the coal seams of the eo permian rio bonito formation the coal seams were predominantly deposited in a lagoon barrier system linked with a third order transgressive systems tract subdivided into four parasequence sets each set represents a major transgressive pulse in the sedimentary history of the basin

coalbed methane characteristics of gates formation coals northeastern british columbia effect of maceral composition the majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite rich coals however western canadian coals are more inertinite rich than those of the western united states and are shown to differ in gas adsorption characteristics the influence of maceral composition upon gas adsorption characteristics of medium volatile coal samples from the middle cretaceous gates formation of northeastern british columbia was investigated lithotype coal facies samples were analyzed for surface area maceral and mineral composition and methane adsorption standard coal analyses were also performed proximate low temperature ash and equilibrium moisture the vitrinite content of the samples analyzed ranges from 18 to 95 vol min ral matter free the ash yield varies from 4 4 to 33 7 wt both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms on a mineral matter free basis the amount of methane adsorbed generally increases with vitrinite enrichment the lowest methane adsorption occurs in the sample with the highest inertinite content carbon dioxide surface areas of the lithotypes range from 87 to 176 m2 g on a raw coal basis and from 99 to 184 m2 g on a mineral matter free basis surface area generally decreases with increased mineral matter content and increases with increased vitrinite content the increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite vitrinite is predominantly microporous whereas inertinite is meso to macroporous the monolayer volumes of carbon dioxide as calculated from the dubininradushkevich equation are higher than those of methane as determined from the langmuir equation but are correlated the methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit

pore fluid compositions and inferred fluid flow patterns at the haima cold seeps of the south china sea abstract fluid flow patterns at cold seeps provide insights into the mechanism and influence of methane emission into the ocean which is critical in its environmental impact assessment here we report pore fluid compositions of three 8 m long piston cores qdn 14a qdn 14b and r1 collected from the newly discovered active haima cold seeps on the northwestern slope of the south china sea reaction transport models were further applied to quantify related biogeochemical processes and to reveal the patterns of fluid flow extremely low 13c values

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

impact of anaerobic oxidation of methane on the geochemical cycle of redox sensitive elements at cold seep sites of the northern south china sea abstract cold hydrocarbon seepage is a frequently observed phenomenon along continental margins worldwide however little is known about the impact of seeping fluids on the geochemical cycle of redox sensitive elements pore waters from four gravity cores d 8 d 5 d 7 and d f collected from cold seep sites of the northern south china sea were analyzed for so42 mg2 ca2 sr2 dissolved inorganic carbon dic 13cdic dissolved fe mn and trace elements e g mo u the sulfate concentration depth profiles 13cdic values and dic ca2 mg2 so42 ratios suggest that organoclastic sulfate reduction osr is the dominant process in d 8 core besides osr anaerobic oxidation of methane aom is partially responsible for depletion of sulfate at d 5 and d 7 cores the sulfate consumption at d f core is predominantly caused by aom the depth of sulfate methane interface smi and methane diffusive flux of d f core are calculated to be 7 m and 0 035 mol m 2 yr 1 respectively the relatively shallow smi and high methane flux at d f core suggest the activity of gas seepage in this region the concentrations of dissolved uranium u were inferred to decrease significantly within the iron reduction zone it seems that aom has limited influence on the u geochemical cycling in contrast a good correlation between the consumption of sulfate and the removal of molybdenum mo suggests that aom has a significantly influence on the geochemical cycle of mo at cold seeps accordingly cold seep environments may serve as an important potential sink in the marine geochemical cycle of mo

quantifying submarine fluid seep activity along the north anatolian fault zone in the sea of marmara abstract the sea of marmara presents the rare case where active seafloor venting sites are found on the surface trace of a major plate boundary fault the north anatolian fault zone the objective of the 2007 marnaut project was to quantify the level of activity of these venting sites and the source of the fluids emitted with the goal of understanding the processes involved and setting a baseline for long term studies of the relationship between seismic activity and fluid migration expulsion processes sites for flow meter and fluid sampler deployment and coring included basin bounding transtensional faults and strike slip faults cutting through the topographic highs significant fluid flow appears to be primarily an episodic phenomenon at all sites with background rates on the order of mm yr to cm yr except at or very near rare focused vents basin bounding faults expel primarily shallow sourced fluid with a strong influence of brackish pleistocene lake marmara water with the notable exception of the main active fault along the northern edge of the cinarcik basin expulsion sites where the main fault crosses topographic highs are more complex with evidence for deep sourced fluids including thermogenic gas one site on the western high displayed two mound structures that appear to be chemoherms atop a deep seated fluid conduit the fluids being expelled are brines with an exotic fluid chemistry along with thermogenic gas and oil our work shows that submerged continental transform plate boundaries can be hydrologically active and exhibit a diversity of sources and processes

evaluation of coalbed gas potential of the seelyville coal member indiana usa abstract the seelyville coal member of the linton formation in indiana potentially contains 0 03 trillion m3 1 1 tcf of coalbed gas the gas content determined by canister desorption technique ranges from 0 5 to 5 7 cm3 g on dry ash free basis 15 4 to 182 2 scf ton the controls on gas content distribution are complex and cannot be explained by the coal rank alone ash content and the lithology of the overlying strata among other factors may influence this distribution

tracing the evolution of seep fluids from authigenic carbonates green canyon northern gulf of mexico authigenic carbonates from hydrocarbon seeps are unique long term archives of past fluid flow the studied samples were collected from green canyon block 140 at a water depth of 260 m in the gulf of mexico petrography x ray diffraction stable isotopes and c 14 dating were applied to assess the evolution of seep activity and potential driving forces the carbonates are dominated by high mg calcite hmc and aragonite with a minor amount of low mg calcite lmc and dolomite petrographically peloids clotted microfabric acicular aragonite and a variable content of bioclasts were observed three types of carbonates are recognized structure i carbonates with c 14 ages from 46 5 ka to 25 8 ka bp are characterized by delta c 13 values from 23 2 parts per thousand to 5 1 parts per thousand suggesting multiple carbon sources that include thermogenic methane biodegraded crude oil seawater and residual co2 from methanogenesis at greater depth in contrast structure ii carbonates formed between 17 6 ka and 11 7 ka bp and have delta c 13 values varying from 22 2 parts per thousand to 8 8 parts per thousand suggesting carbon sources similar to those of structure i carbonates but with a negligible influence of residual co2 from methanogenesis in addition the presence of lmc in this type of carbonate may be associated with brine seepage structure iii carbonates among the youngest of the samples analyzed with c 14 ages of 1 2 ka bp these carbonates have the most negative delta c 13 values ranging from 36 1 parts per thousand to 26 8 parts per thousand suggesting that thermogenic methane is the primary carbon source the majority carbonates of both structure i and ii are slightly o 18 enriched which is most likely related to the incorporation of water from dehydration of clay minerals the considerable range of mineralogical and isotopic variations of the studied carbonates highlights the local control of the seepage flux it is proposed that factors affecting the activity of hydrocarbon seeps are sea level changes and salt movement the combination of petrography stable isotopes and dating approach used here highlights that these are valuable tools to assess the variability of past fluid flow at hydrocarbon seeps c 2013 elsevier ltd all rights reserved

complex flow patterns through hydrate ridge and their impact on seep biota our recent measurements of long term fluid flux rates and output fluid chemistry at seep sites on hydrate ridge cascadia suggest that the mechanisms driving fluid flow in gas hydrate bearing forearc settings may be significantly more complex than previously thought temporal changes in the polarity and magnitude of flow and in seep fluid chemistry were observed the nature of flow appears to generate a strong response in the chemosynthetic seep community ecology we document here 1 the frequency and range of temporal variability in flow rates 2 the relatively rapid changes in outflow composition 3 strong outflow of seawater like fluids 4 the association of calyptogena sp clams with oscillatory and inflow settings and 5 microbial mat communities associated with strong advection of altered fluids these results suggest that a reappraisal may be required of the nature of the hydrologic system and its effect on related processes such as benthic seep community ecology and biogeochemical cycles

coals associated with tidal sediments in the wilcox group paleogene south texas abstract the several coal seams in 50 m of wilcox strata on the chacon creek east lignite property in south texas are closely associated with tidal sediments the coal bearing sequence is underlain by greenish bioturbated sandstone deposited in open marine water the sediments between the coals and cutting the coals consist of coarsening and fining upward sequences of interbedded sandstone and mudstone with lenticular wavy and flaser bedding and ripple laminated and cross bedded sandstone the sediments contain marine dinoflagellates and palynomorphs of an inland flora most of the sediment accumulated in tidal channels each coal is underlain by rooted strata usually an underclay palynomorphs in the lignite suggest the peat accumulated in low lying swamps dominated by tupelo trees these swamps lay along the landward margin of a tidal channel complex the channel complex probably extended 10 to 30 km inland from the main coastline repeated regressive and transgressive episodes with corresponding expansion and contraction of the peat swamps within the estuarine complex would explain the coal bearing sequence at chacon creek east

jolliet field thrust fault structure and stratigraphy green canyon block 184 offshore louisiana abstract jolliet field is believed to be the first development in the offshore u s gulf of mexico to exploit a major thrust fault structure and as such represents a new and potentially important type of deep water structural play the field s multiple stacked reservoirs consist of pleistocene lowstand gravity flows deposited in upper slope fans the thrust fault is documented by 3 d seismic interpretation repeated paleontologic markers and correlation of up to 3000 feet of repeated pay section this fault is believed to be the toe thrust of a major gravity slide which was triggered in the lower pleistocene when sediments were tilted to a critical angle by a rising salt diapir seismic data suggest that the resulting slide surface is approximately cylindrical connecting a major growth fault on the west side of green canyon block 184 to the jolliet field thrust fault salt withdrawal in the area produced normal faults some of which cut the thrust fault adding structural complexity to the field in addition to the geologic and geophysical evidence the structural model is supported by slope stability computer modelling using realistic sediment shear strengths densities and pore pressures

the argentine continental margin north of 48 s sedimentary successions volcanic activity during breakup abstract new seismic data and geophysical results from the outer argentine continental margin and from seismic flow line transects across the oceanic argentine brazil and cape angola basins are presented the results document that the early cretaceous south atlantic continental breakup and initial sea floor spreading were accompanied by large scale transient volcanism emplacing voluminous extrusive constructions on the conjugate outer continental margins of the south atlantic on the argentine margin we interpret three major tectono volcanic crustal units beneath a thick and tectonically undisturbed sedimentary succession of cretaceous and tertiary age 1 syn rift basins and even pre rift features are present on the outer shelf 2 a deeply buried 60 120 km wide and several thousand metres thick volcanic wedge occupies most of the slope the wedge is characterized by seaward dipping reflectors and is associated with the distinct magnetic anomaly g 3 the seaward adjacent oceanic crust of cretaceous age shows isochronous changes of the seismic images along our flow line transects suggesting some form of episodicity of rich magma and poor to moderate magma supply at the pre existing mid ocean ridge of the south atlantic during cretaceous time

fluid venting along japanese trenches tectonic context and thermal modeling abstract large benthic chemosynthetic communities have been observed at four main locations during the kaiko submersible dives in the japanese trenches they appear to be associated with venting along fractures the first site for our observation was along the japan and kuril trenches where the continental margin is eroded by the subducting plate and collapses into the trench the benthic communities there seem to be related to tension gashes parallel to the subduction vector the other communities were found on the toe of the nankai accretionary prism along the frontal thrust and tension gashes the temperature anomaly associated with one of the communities is modeled to constrain the upward flow of interstitial water as the anomaly has a small spatial extent and as the peak thermal gradient is high the best fitting model is to be found in a vertical upward flow at a velocity of 100 m yr in a cylindrical conduit leading out of an underlying shallow thrust